f^^ 


C-' 


THE 


COMPARATIVE  ANATOMY 

OF    THE 

DOMESTICATED    ANIMALS. 


THE 


COMPARATIVE    ANATOMY 


OF    THE 


DOMESTICATED  ANIMALS. 


By  a.  CHAUVEAU, 

PROFESSOR    AT   THE    LTONS    VETERINARY    SCHOOL. 


ntrnts  ©Mtion,  ^ebiscb  anb  6nlargfb,  foitlj  the  Co-operation  of 
S.   ARLOING, 

LATE  PEINCIPAL  OF  AXATOMT  AT  THE  LTONS  VETERINARY  SCHOOL  ; 
PROFESSOR  AT  THE  TOULOUSE  VETEBI:NARY  SCHOOL. 


TRANSLATED  AND  EDITED 


GEOEGE    FLEMING,    F.  R.  G.  S.,   M  A.  I., 

vetbrlnart  surgeon,  royal  engineers, 
author  of  '-travels  on  h0e8eback  in  mantchtj  taktart,"  "hor8b-8hoe3  and  horse-shoeing,' 

"animal  plagues,"   "practical  HORSE-SHOEING,"    "RABIES   AND  HYDROPHOBIA,"  ETC. 


'WITH     4SO     ILLUSTRATIONS. 


NEW  YORK: 
D.    APPLE  TON     AND     COMPANY, 

549    &    551    BROADWAY. 
1873. 


Digitized  by  the  Internet  Archive 

in  2009  with  funding  from 

NCSU  Libraries 


http://www.archive.org/details/comparativeanaOOchau 


BftJtcatctJ 

TO    THE    MEMORY    OF 

JOHX  LA^ysoN,  m. rc.v.s., 

OF   MANCHESTER, 

WHO  FIRST  URGED  THE  DESIRABILITY  OF  UNDERTAKING  THIS  TASK, 
AND  AVHOSE  SINCERE  AND  INESTIMABLE  FRIENDSHIP  AND  ENCOURAGEMENT   FOR 

MANY  YEARS 

THE  EDITOR,  AND  TRANSLATOR  HEREBY  ACKNOWLEDGES  WITH  SORROWFUL 

AFFECTION  AND  GRATITUDE. 


PREFACE  BY  THE  TRANSLATOR  AND 
EDITOR. 


In  undertaking  the  arduous  task  of  translating  and  editing  the  '  Traite  d* 
Anatomie  Gomparee  des  Animaux  Domestiques '  of  M.  Chauveau,  I  have  been 
moved  by  a  desire  to  fill  a  void  in  medical  literature  which  has  always 
existed,  so  far  as  the  English  language  is  concerned.  There  has  been  no 
complete  treatise  on  the  anatomy  of  the  domesticated  animals,  and  the 
absence  of  such  a  work  has  exerted  a  serious  influence  on  the  progress  of 
veterinary  science,  and  doubtless  proved  more  or  less  of  a  loss  to  the 
community  at  large. 

The  only  text  book  to  which  the  student  or  practitioner  of  animal 
medicine  could  until  recently  refer,  has  been  that  on  the  anatomy  of  the 
Horse,  written  by  the  late  distinguished  army  veterinary  surgeon,  William 
Percivall,  more  than  forty  years  ago :  a  book  which,  though  in  every  way 
creditable  to  its  author,  was  notoriously  incomplete,  even  as  regards  the 
anatomy  of  the  only  animal  it  treated  of,  and  was  without  illustrations.  No 
serious  attempt  has  been  made  to  teach  the  structure  of  the  other  useful 
creatures  domesticated  by  man,  valuable  though  many  of  them  are ;  and 
the  student  who  was  anxious  to  acquire  this  knowledge  had  no  guide  to 
lead  or  instruct  him.  At  college,  this  loss  may  not  have  been  so  severely 
felt  as  when,  having  graduated,  he  entered  on  the  jiractice  of  his  profession ; 
and  if  the  experience  of  veterinary  surgeons  in  general  has  been  like  my 
owTi,  they  will  be  ready  to  testify  to  the  almost  daily  regret  they  felt 
at  the  very  meagre  notions  of  anatomy  they  possessed,  and  the  benefit  a 
complete  and  trustworthy  manual  would  confer. 

My  professional  avocations  in  the  army  would  not  permit  me  to  make 
the  necessary  dissections  for  the  production  of  such  a  work  •  and  indeed 
so  many  classical  and  standard  treatises  on  the  subject  have  appeared, 
during  this  century,  on  the  Continent,  and  notably  in  France  and  Germany, 
that  it  would  seem  a  mere  waste  of  time  and  labour  to  attempt  a  task  which 


viii  PREFACE  BY  THE  TRANSLATOR  AND  EDITOR. 

has   been  already  so  thoroughly  accomplished  by  very  zealous  and  pro- 
ficient anatomists. 

In  selecting  for  translation  the  present  treatise  in  preference  to  other 
works  which  are  justly  held  in  high  estimation,  I  was  influenced  not  only 
by  the  knowledge  that  it  was  written  by  one  of  the  most  talented  com- 
parative anatomists  and  physiologists  of  the  day,  but  by  the  ability  and 
ori""inality  which  are  so  conspicuous  in  every  page,  I  was  also  aware 
that,  for  more  than  a  century,  the  French  veterinary  schools  have  been 
celebrated  for  the  careful  and  thorough  manner  in  which  anatomy  has  been 
taught  by  most  efficient  teachers,  who  are  all  selected  by  open  com- 
petition ;  and  that  Professor  Chauveau's  book  was  the  approved  dissection 
manual  of  these  and  other  Continental  schools. 

Escellent  as  was  the  first  edition  of  the  work,  the  second  is  still  more 
complete ;  indeed  it  may  be  said  to  be  almost  a  new  book,  owing  to  the 
assistance  afforded  by  M.  Arloiug,  an  anatomist  who  promises  to  assume  a 
high  rank  in  his  profession. 

The  French  treatise  is  illustrated  by  three  himdred  and  sixty-eight  wood- 
cuts, but  for  several  reasons  it  was  deemed  advisable  to  select  only  one 
hundred  and  seventy-three  from  this  number  :  those  rejected  being  chiefly 
human  figures,  and  either  far  larger  than  was  necessary  or  compatible  with 
the  space  at  disposal,  or  not  so  well  suited  for  such  a  work  as  1  was 
intent  on  producing.  Nearly  sixty  original  figures  have  been  added  to  those 
selected;  and  through  the  courtesy  and  liberality  of  Messrs.  J.  and  A. 
Churchill,  the  total  number  has  been  increased  to  four  hundred  and  fifty. 
The  profuseness  and  general  excellence  of  these  drawings,  and  their  great 
accuracy,  will,  it  is  hoped,  materially  lessen  the  fatigue  and  time  demanded 
for  the  study  of  this  most  important  subject,  and  prove  valuable  for  reference 
to  the  operator  or  busy  practitioner. 

No  labour  or  pains  have  been  spared  to  make  the  work  the  most  complete 
and  useful  of  any  that  has  been  produced.  The  best  treatises  in  German, 
French,  and  Italian  have  been  consulted  in  editing  it,  and  when  necessary, 
I  have  added  to  the  descriptions.  These  additions  are  contained  within 
brackets,  thus  (  ).  As  my  task  has  been  accomplished  without  any 
aid,  I  assume  the  entire  responsibility  for  any  errors  of  omission  or 
commission  that  may  exist ;  my  aim  being  to  furnish  what  has  been  an 
urgent  desideratum  for  very  many  years — a  complete  dissection  manual  for 
the  student  of  veterinary  science,  a  book  of  reference  for  the  veterinary 
surgeon,  and  a  work  that  might  be  available  for  the  zoologist,  comparative 
anatomist,  ethnologist,  and  medical  practitioner.  I  have  for  a  long  time 
believed  that  the  two  branches  of  medicine — human  and  animal — should  be 
more  closely  allied  than  they  are  at  present,  and  that  this  alliance  can  only 
be  effected  by  a  mutual  study  and  recognition  of  the  facts  which  prove  that 
the  two  are  really  one — wide  apart  though  they  have  hitherto  been  kept 
in  this  country — and  that  each  is  capable  of  conferring  on  the  other  great 
and  lasting  benefits.     Hence  my  retaining  what  constitutes  a  new  feature 


PREFACE  BY  THE  TRANSLATOR  AND  EDITOR.  ix 

in  the  second  edition  of  Chauveau's  treatise — the  comparison  of  the  organs 
of  Man  with  those  of  Animals. 

I  have  omitted  from  the  translation  the  references  made  to  the  Dro- 
medary and  Eabbit ;  these  animals  seldom,  if  ever,  coming  under  the  notice 
of  the  comparative  pathologist  in  this  country. 

My  grateful  acknowledgments  are  due  to  my  friend  and  colleague, 
Professor  Chauveau,  for  the  great  courtesy  with  which  he  not  only  sanc- 
tioned the  translation  now  before  the  i^ublic,  but  offered  to  supply  me  with 
the  proof  sheets  of  the  new  edition  as  it  passed  through  the  press. 

To  the  numerous  professional  friends  who  pressed  upon  me  the  necessity 
of  making  such  an  extensive  sacrifice  of  my  few  leisure  hours,  by  under^ 
taking  a  work  of  this  magnitude,  I  have  to  express  my  deep  regret  at  the 
delay  which  has  occured  in  its  appearance.  The  fault  was  not  mine  :  but  for 
the  disturbance  and  abeyance  of  all  business,  save  that  of  slaughter,  in  and 
around  Paris  while  the  book  was  in  course  of  publication,  my  task  must 
have  been  achieved  nearly  two  years  ago. 

I  may  assure  them,  how^ever,,  that  the  delay  has  been  rather  beneficial 
than  otherwise ;  as  it  has  allowed  me  to  give  more  time  to  perfect  what 
might,  under  other  circumstances,  have  been  less  complete  and  satisfactory. 


GEOKGE  FLEMING. 


Brompton  Baebacks,  Chatham. 
February,  1873. 


PEEFACE  TO  THE  FIRST  EDITION, 


To  present  iu  a  concise  and  complete  form  an  exact  description  of  tlie 
anatomical  machinery  of  which,  the  bodies  of  our  domesticated  animals  are 
composetl,  has  been  onr  aim  in  writing  the  book  now  offered  for  public 
appreciation. 

We  have  sought  for  concision,  not  only  in  language,  but  also  in  the 
choice  of  facts  and  ideas,  with  a  kind  of  stubbornness.'  In  imposing  on 
ourselves  this  condition,  we  believe  we  have  rendered  a  service  to  those 
who  may  have  recourse  to  the  book,  in  economising  their  time.  In  an  age 
of  progress  like  the  present,  when  the  sciences  are  becoming  multiplied  and 
developed,  and  when  the  hiunan  mind,  seized  by  the  fever  of  production, 
gives  forth  every  day  books  consecrated  to  the  study  of  these  sciences,  there 
is  scarcely  leisure  to  read  and  to  learn.  It  is,  therefore,  the  duty  of  a 
writer  to  be  brief.  If  he  loads  his  book  with  puerile  details ;  if  he  says 
that  which  may  easily  be  divined  by  his  reader ;  and  if  he  describes  facts 
and  ideas  too  redundantly ;  will  he  have  attained  the  wished-for  perfection 
—in  a  word,  will  he  be  complete  ?  No,  he  will  be  tedious :  a  serious 
inconvenience,  which  neither  elegance,  warmth,  nor  brilliancy  of  style  will 
always  excuse  when  met  with  in  a  didactic  work,  and  especially  in  an 
elementary  treatise. 

No  effort  has  been  spared  to  achieve  exactitude — the  primary  desideratum 
in  such  a  work  as  this ;  neither  have  evenings  spent  in  bibliographic  re- 
searches, nor  fatigue  in  the  dissecting-room  been  considered.  All  iniblished 
writings  on  animal  organisation,  general  treatises,  special  manuals,  mono- 
graphs, and  articles  in  periodicals  have  been  read  and  interrogated.  But  we 
have  more  particularly  sought  for  information  from  Nature — that  certain 
and  infallible  guide,  always  wise,  even  in  her  diversities ;  we  have  consulted 
her,  scaljiel  in  hand,  with  a  perseverance  that  nothing  could  repel.  Animals 
of  every  kind  were  had  recourse  to,  and  we  have  largely  profited  by  the 
immense  resources  which  our  position  as  principal  of  anatomical  teaching 
in  the  Imperial  Veterinary  School  has  placed  at  our  disposal. 


xii  FEE  FACE  TO  THE  FIRST  EDITION. 

It  was  not  enougli  that  we  should  be  correct,  that  we  should  faithfully 
describe  the  organs  of  the  animal  economy.  It  was  desirable  tliat  the  truth 
might  be  presented  from  a  high  philosophical  point  of  view — one  that 
should  rise  above  details.  It  is  necessary  in  a  book,  and  especially  in  one 
on  anatomy,  that  there  should  be  a  salient  idea  which  might  indicate 
its  purpose  and  originality,  and  distinguish  it  as  something  more  than  a 
mere  arid  catalogue,  by  unifying  the  thousand  different  objects  of  which 
it  treats.  In  support  of  this,  we  would  ask  permission  to  explain,  in  a  few 
words,  the  idea  that  presided  in  the  construction  of  our  work. 

Among  the  beings  or  objects  composing  the  natural  world,  animals  are 
distinguished  by  diversity  in  size  and  external  conformation.  Is  this 
diversity  repeated  in  their  internal  structure  ?  When  order  and  simi^licity 
prevail  everywhere  else  in  nature,  should  we  expect  to  find  disorder  and 
complication  there,  or  look  for  as  many  different  organisations  as  there  are 
particular  sj)ecies  ?  To  state  these  questions,  and  to  resolve  them  in  the 
affirmative,  would  be  to  insult  the  wisdom  of  the  Creator.  The  early 
naturalists,  guided  by  instinct  rather  than  knowledge,  admired  a  certain 
uniformity  in  the  composition  of  animals. 

It  was  a  good  inspiration,  which  threatened  to  become  effaced  at  the 
period  when  anatomical  science,  diffused  and  cultivated  everywhere  with  the 
most  laudable  eagerness,  daily  discovered  the  secrets  of  the  organisation  of 
new  species.  Without  a  guide  in  the  search  for  analogies,  struck  with  the 
apparent  differences  their  scalpel  exposed  every  moment,  the  anatomists  of 
that  epoch  neglected  to  compare  the  diverse  animals.  In  presence  of  a  new 
form  of  organs,  they  believed  in  the  existence  of  a  new  instrument,  and 
created  a  new  name  to  designate  it.  Then  was  human  anatomy,  and  that  of 
the  Horse,  Ox,  etc.,  established ;  monographs  became  multiplied ;  as  the 
different  opinions  increased,  so  there  was  the  greater  need  for  a  bond  to 
unite  these  incongruous  materials ;  confusion  commenced,  and  chaos  was 
about  to  appear ;  and  the  principle  of  analogies  was  on  the  point  of  being 
buried  beneath  the  ruins  of  science. 

Hapj)ily,  two  men  appeared,  men  of  genins,  who  were  the  glory  of 
France — G.  Cuvier  and  Etienne  Geoffrey  Saint- Hilaire  ;  two  names  which 
will  be  for  ever  illustrious,  and  which  we  love  to  unite  as  the  expression 
of  one  and  the  same  symbol. 

The  first,  after  immense  researches,  ventured  to  compare  the  innu- 
merable species  in  the  animal  kingdom  with  each  other;  he  seized  their 
general  characters — the  analogies  which  allied  them  to  one  another ;  he 
weighed  these  analogies,  contrasted  them  with  the  dissimilarities,  and 
established  among  them  different  kinds  and  different  degrees ;  and  in  this 
way  was  he  able  to  form  natural  groups,  themselves  subdivided  into  several 
categories  in  which  individuals  were  gathered  togetlier  according  to  their 
analogies  and  affinities.  Then  the  chaos  was  swept  away,  light  appeared, 
and  the  field  of  science  was  no  longer  obscured ;  comparative  anatomy  was 
created  in  all  its  branches,  and  the  structure  of  the  animal  kingdom  was 


PREFACE  TO  THE  FIRST  EDITION.  xiii 

brought  within  those  laws  of  uniformity  which  shine  throughout  the  other 
parts  of  creation. 

Geoffiroy  Saint-Hilaire  followed  Cuvier  over  the  same  ground.  More 
exclusive  than  Cuvier,  he  entirely  neglected  the  differential  characters,  and 
allowed  himself  to  be  governed  by  the  consideration  of  resemblances.  He 
especially  pursued  the  discovery  of  a  fixed  rule  for  guidance  in  the  search 
after  these  resemblances — a  difficult  task,  and  a  dangerous  reef,  upon 
which  the  sagacity  of  his  illustrious  rival  was  stranded.  To  be  more 
certain  than  Cuvier,  and  the  better  to  grasp  his  subject,  he  restricted  the 
scope  of  his  observations,  confining  himseK  more  particularly  to  the  class  of 
vertebrata  in  order  to  solve  the  enigma  whose  answer  he  sought.  At  last 
he  found  it,  and  made  it  known  to  us  in  those  memorable,  though  abstruse 
pages,  in  which  the  meaning  is  often  obscui-e  and  hidden,  but  which 
contain,  nevertheless,  magnificent  hymns  chanted  to  the  honour  of  the 
Creator.  The  shape  and  functions  of  organs,  he  says,  do  not  offer  any 
stability,  only  their  relations  are  invariable ;  these  alone  cannot  give 
deceptive  indications  in  the  comparison  of  the  vital  instruments.  He  thus 
founded  his  great  principle  of  connections,  firmly  established  its  value, 
fortified  it  by  accessory  principles,  and  held  it  up  to  the  generations  to 
come  as  a  compass,  a  succourable  beacon-light,  under  whose  protection  they 
might  proceed  to  the  conquest  of  analogies  with  confidence  and  security. 
Then  was  the  philosophical  sentiment  decidedly  introduced  into  the 
researches  in  organisation,  and  anatomy  became  a  veritable  science. 

Enthusiastically  admiring  these  two  great  masters,  we  glory  in  be- 
longing to  their  school ;  it  is,  therefore,  enough  to  say  that  the  prevailing 
idea  in  our  work  has  been  inspired  by  their  labours.  Thus,  in  describing 
the  organs  in  the  somewhat  numerous  species  of  animals  treated  of, 
and  noting  their  differential  characters,  we  have  always  endeavoured  to 
demonstrate  their  analogies. 

The  hojies  that  Geoffroy  Saint-Hilaire  entertained  for  the  future  of 
philosophical  anatomy  have  not  been  entirely  realised.  Natm-alists,  it  is 
true,  have  always  cultivated  this  admirable  science ;  Lecoq  has  preserved 
its  traditions  at  the  Lyons  Veterinary  School,  in  his  simple,  lucid,  and 
elevated  teaching ;  and  at  Toulouse,  an  able  and  learned  professor,  Lavocat, 
has  courageously  hoisted  his  flag.  But  everywhere  else,  and  particularly  in 
the  Medical  Schools,  has  not  anatomy  remained  essentially  monographic 
and  purely  surgical  ?  And  many  medical  men  and  veterinary  surgeons,  only 
looking  at  the  practical  side  of  this  science,  and  full  of  defiance  with 
respect  to  speculative  theories,  will  perhaps  give  us  no  credit  for  our  efforts 
in  bringing  the  anatomy  of  animals  into  philosophical  courses.  To  these 
we  have  nothing  to  say ;  if  they  do  not  see  how  much  science  is  developed 
and  becomes  comprehensible  with  such  elements:  if  they  cannot  under- 
stand all  that  is  noble  and  useful  in  these  generalising  views ;  and  if  they 
do  not  feel  elevated  sentiments  .revolve  in  their  mind  in  jjresence  of  the 
simplicity  of  Nature's  laws,  it  is  because  their  thoughts  are  not  in  unison 


xlv  PREFACE  TO  THE  FIRST  EDITION. 

with  onrs,  and  we  carefully  abstain  from  engaging  in  a  sterile  discussion 
with  them. 

Such  is  our  plan  :  have  we  executed  it  in  a  satisfactory  manner  ?  We 
have  not  deluded  ourselves  with  regard  to  our  strength,  and  willingly 
acknowledge  that  many  resources  and  many  qualities  have  failed  us  in 
carrying  the  enterprise  to  a  favourable  termination ;  therefore  we  hope  to 
be  indulgently  judged. 

If  we  have  succeeded  in  facilitating  the  study  of  so  important  a  subject 
as  anatomy  for  the  pupils  of  the  veterinary  schools  ;  if  our  book  becomes,  in 
the  hands  of  practitioners,  a  useful  surgical  guide ;  if,  lastly,  medical  men 
and  naturalists  find  that  it  will  assist  them  in  their  researches  in  com- 
parative anatomy,  our  object  will  have  been  attained,  and  we  shall  have 
received  the  best  recompense  which  the  honest  writer  can  hope  to  obtain. 

Before  terminating,  a  sentiment  of  justice  and  recognition  again  brings 
the  honourable  name  of  M.  Lecoq  to  our  pen ;  the  idea  of  this  book  was 
conceived  at  his  lectures,  and  it  is  from  these  lectures  that  we  have  derived 
the  major  part  of  our  materials ;  it  was  to  satisfy  the  most  imperious 
desire  of  our  heart  and  conscience  that  we  offered  to  dedicate  this  first 
attempt  to  him.     Could  it  be  better  placed  than  under  his  patronage  ? 

We  have  also  willingly  joined  to  his  name  that  of  M.  H.  Bouley,  that 
eminent  and  devoted  master,  to  whose  advice  we  owe  so  much,  and  who  has 
evinced  the  liveliest  solicitude  for  us  in  circumstances  which  we  can  never 
forget.  May  he  deign  to  accept  this  homage  as  the  expression  of  our 
sincere  recognition. 

We  have  found  in  the  obligingness  and  intelligence  of  M.  Eodet  a  very 
efficacious  aid ;  he  will  permit  us  to  tender  all  our  gratitude. 

We  have  frequently  put  the  complaisance  of  the  students  around  us  to  a 
severe  test ;  bi;t  they  have  never  failed,  and  we  are  gratified  in  being  able  to 
thank  them  most  cordially.  We  especially  mention  the  name  of  M.  Violet, 
whose  intelligent  zeal  has  spared  us  much  toil  in  the  difficult  task  imposed 
upon  us. 

A.  Chauveau. 
Lyons, 
September  30,  1854. 


PEEFACE  TO  THE  SECOND  EDITION. 


CiECUMSTANCES  independent  of  my  "wiU  Iniv^  prevented  me  from  publishing 
the  Second  Edition  of  my  '  Treatise  on  Anatomy '  earlier.  Those  to  whom 
the  work  is  addressed  will  have  lost  nothing  by  the  delay,  as  it  has  allowed 
me  to  procm-e  the  co-operation  of  one  of  my  most  distinguished  and  best- 
esteemed  pupils. 

The  researches  in  pathological  physiology  and  experimental  medicine, 
to  which  I  have  consecrated  my  efforts  and  resources  for  some  years,  would 
have  left  me  no  leisure  to  do  more  than  give  a  simple  reprint  of  my  first 
edition  ;  consequently,  I  must  have  allowed  important  omissions  to  remain, 
and  have  renounced  the  idea  of  re-casting  it  according  to  a  new  plan  I  had 
conceived,  even  before  that  edition  was  terminated. 

Thanks  to  the  assistance  of  M.  Arloing,  who  had  long  before  been 
initiated  into  my  projects,  and  the  details  as  to  their  execution  which  had 
been  present  to  my  mind,  this  re-casting  has  been  aceomj)lished,  and  the 
'  Treatise  on  the  Comparative  Anatomy  of  the  Domesticated  Animals '  has 
thus  become  an  almost  entirely  new  work. 

I  need  not  attempt  to  indicate  the  importance  of  the  modifications  and 
considerable  additions  that  this  remodelling  has  entailed  ;  nor  the  ame- 
liorations which  the  publishers  have  introduced  in  the  execution  of  the 
material  portion  of  the  work.  It  is  sufficient  to  open  the  book  to  be 
convinced  of  these  advantages. 

A.  Chauveau. 
Lyons, 

March  15th,  1872, 


v^ 


TABLE   OF   CONTENTS. 


Translator  and  Editor's  Preface 
Preface  to  the  First  Edition    .. 
Preface  to  the  Second  Edition 
Table  of  Contents 
Table  of  Illustrations 


PAGE 

vii 

si 

sv 

xvii 

xxxvi 


GENERAL    CONSIDEKATIONS. 
Definition  and  Division  of  Anatomy  ...... 

Enumeration  and  Classification  of  the  Domesticated  Animals  . 
General  Idea  of  the  Organisation  of  Animals,  and  the  order  followed  in  studying 
their  apparatus  ......... 


BOOK  I. 

LOCOMOTOEY   APPARATUS. 
First  Sectiox. — The  Bones    ..... 
Chapter  I. — The  Bones  in  G  eneral        .... 
Article  i. — The  Skeleton  ..... 
Article  n. — General  Principles  applicable  to  the  Study  of  all  the  Bones 
Name,  Situation,  Direction,  and  Configuration  of  the  Bones 
Internal  Conformation  of  the  Bones.     Structure  of  the  Bones 
Development  of  the  Bones  .... 

Chapter  II. — The  Bones  of  Mammalia  in  Particular 
Article  i. — Vertebral  Column        .... 
Characters  Common  to  all  tlie  Vertebrae 
Characters  Proper  to  the  Vei  tubras  in  each  region 

1.  Cervical  VertebrsB        ..... 

2.  Dorsal  Vertebrae    ..... 

3.  Lumbar  Vertebraa        ..... 

4.  Sacrum     .....  ^ 

5.  Coccygeal  Vertebrae     ..... 
Of  the  Spine  in  General  .... 
DitTerential  Cliaracters  in  the  Vertebral  Column  of  other  than 

Animals  ...... 

Comparison  of  the  Vertebral  Column  of  Man  with  that  of  Animals 
Article  n. — Tne  Head  ..... 

The  Bones  of  the  Cranium 

1.  Occipital         .  .  .... 

2.  Parietal     ....... 

3.  Frontal'  ...... 

2 


. 

6 

6 

7 

les 

10 

10 

13 

16 

18 

, 

18 

19 

21 

21 

, 

24 

25 

. 

26 

27 

28 

Solipec 

I 

29 

32 

33 

^ 

33 

33 

, 

35 

36 

TABLE  OF  CONTENTS. 


4.  Ethmoid    ..... 

5.  Sphenoid         .... 

6.  Temporal  .... 
The  Boues  of  the  Face 

1.  Superior  Maxillary  or  Great  Supermaxillary 

2.  Intermaxilla,  Incisive  Bone,  Small  Supermaxilla,  or  Premaxilla 

3.  Palate       .... 

4.  Pterygoid        .... 

5.  Zygomatic  . 

6.  Lachrymal      .... 

7.  Bones  proper  to  the  Nose,  or  Supcrnasal 

8.  Turbinated  Bones 

9.  Vomer       .... 

10.  Inferior  Maxillary 

11.  Hyoid        .... 

Of  the  Head  in  General       ...... 

Differential  Characters  in  the  Head  of  other  tiian  Soliped  Animals 
Comparison  of  the  Head  of  Man  with  that  of  Animals 

Article  in. — The  Thorax  ...... 

The  Bones  of  the  Thorax  in  Particular        .... 

1.  Sternum  of  the  Horse        ..... 

2.  Eibs    ........ 

Of  the  Thorax  in  General  ..... 

Differential  Characters  in  the  Thorax  of  other  than  Soliped  Animals 

1.  Sternum    ....... 

2.  Eibs    . 
Comparison  of  the  Thorax  of  Man  with  that  of  Animals 

1.  Sternum 

2."  Ribs 
Article  rv. — Anterior  Limbs 
Shoulder 
Scajjula 
Arm 

Humerus     . 
Fore-Hrm 

1.  Eadius 

2.  Ulna 
Anterior  Foot 

1.  Bones  of  the  Carpus 

2.  Bones  of  the  Metacarpus 

3.  Bones  of  the  Digit,  or  Phalangeal  Region 
Differential  Characters  in  tiie  Anterior  Limb  nf  other  than  Soliped  Animal 
Comparison  of  the  Thoracic  Limb  of  Man  with  that  of  the  Domesticated 

Animals 
Article  v. — Posterior  Limbs 
Pelvis 

A.  Coxse 

B.  The  Pelvis  in  General 
Tiiigii  . 
Femur 
Leg       . 

1.  Tibia  . 

2.  Fibula 

3.  Patella 


TABLE  OF  CONTENTS. 

Posterior  Foot  ........ 

1.  Bones  of  the  Tarsus     ....... 

2.  Bones  of  the  Metatarsus    ....... 

3.  Bones  of  the  Digital  Begion     ...... 

Differential    Characters    in    the  Posterior   Limb   of  other    than    Soliped 

Animals     ........ 

Comparison  of  the  Abdominal  Limb  of  Man  with  that  of  the  Domesticated 
Animals  ...... 

Article  vr. — The  Limbs  in  General,  and  their  Parallelism 
Chapter  III. — The  Bones  in  Birds         .... 

Chapter  IV. — Theory  of  the  Vertebr.d  Constitution  of  the  Skeleton 
Second  Section. — The  Articulations  .... 

Chapter  I. — The  Articulations  in  Geneial  .... 

General  Characters  of  Diarthroses    .... 

General  Characters  of  Synarthroses        .... 

General  Characters  of  Amjohiartli roses  or  Symphyses 
Chapter  II. — The  Articulations  of  Mammalia  in  Particular 
Article  i. — Articulations  of  the  Spine 

Articulations  between  the  Vertebra;,  or  Intervertebral  Articulations 
Article  ii. — Articulations  of  the  Head 

1.  Atlo-axoid  Articulation 

2.  Occipito-atloid  Articulation 

3.  Articulations  between  the  Bones  of  the  Head 

4.  Temporo-maxillary  Articulation 

5.  Hyoideal  Articulations 
Article  III. — Articulations  of  the  Thorax 

1.  Costo-vertebral,  or  Articulations  of  the  Kibs  with  the  Vertebral  Cohm 

2.  Costo-sternal  Articulations 

3.  Chondro-costal  Articulations,  or  Articulations  between  the  Eibs 

4.  Articvdations  between  the  Costal  Carti'ages     . 

5.  Sternal  Articulation  peculiar  to  the  Ox  and  Pig     . 

6.  The  Articulations  of  the  Thorax  considered  in  a  general  manner,  witl 

respect  to  their  IMovements   . 
Article  iv. — Articidations  of  the  Anterior  Limbs  . 

1.  Scapulo-hunit-ral  Articulation. 

2.  Humero-radial  Articulation 

3.  Radio-ulnnr  Articulation 

4.  Articulations  of  the  Carpus 

5.  Intermetacarpal  Articulations. 

6.  Metacarpo-phalangeal  Articulations  .... 

7.  Articulation   of  the  First   Plialanx  with  tlie  Second,  or   first   Inter 

phalangeal  Articulation         ..... 

8.  Articulation  of  the  Second  Phalanx  with  the  Third,  Second  Inter 

phalangeal  Articulation,  or  Artienlation  of  the  Foot 
Article  v. — Articulations  of  the  Posterior  Limbs 

1.  Articulations  of  the  Pelvis 

2.  Coxo-femoral  Articulation 

3.  Femoro-tibial  Articulation 

4.  Tibio-fibular  Articulation 

5.  Articulations  of  the  Tarsus,  or  Hock 
Chapter  III. — The  Articulations  in  Birds 

Third  Section. — The  Muscles. 

Chapteu  I. — General  Considerations  o;i  the  Striped  Muscles 
The  Striped  Muscles  in  General 


XIX. 

PAGE 

102 
102 
105 
105 

105 

107 
109 
112 
118 
121 
121 
123 
128 
129 
129 
130 
130 
135 
135 
137 
137 
138 
139 
140 
I  140 
141 
142 
142 
142 

142 
143 
143 
144 
147 
148 
152 
153 

156 

157 
159 
159 
161 
163 
167 
168 
172 
173 
174 
174 


s  TABLE  OF  CONTENTS. 

Structure  of  the  Striped  Muscles 
Physico-chemical  Properties  of  the  Striped  Muscles 
Physiological  Properties  of  the  Striped  Muscles 
Annexes  of  the  Muscles 
Manner  of  Studying  the  Muscles     . 
Chapter  II. — The  Muscles  of  Mammalia  in  Particular 
Article  i. — The  Muscles  of  the  Trunk 

Subcutaneous  Eegion    .... 
Fleshy  Pauniculus 

Cervical  Kegion  .... 

A.  Superior  Cervical  or  Spinal  Region  of  the  Neck 
1. 


Ehomboideus         ..... 

2.  Angularis  Muscle  of  the  Scapula 

3.  Splenius    ...... 

4.  Great  Complexus         ..... 

5.  Small  Complexus  (Trachelo-mastoideus)    . 

6.  Transverse  Spinous  Muscle  of  the  Neck  (Spinalis  Colli) 

7.  Intertransversal  Muscle  of  the  Neck 

8.  Great  Oblique  Musfle  of  the  Head  (Obliquus  Capitis  Inferior) 

9.  Small  Oblique  Muscle  of  the  Head    Obliquus  Capitis  Superior) 

10.  Great  Posterior  Straight  Muscle  of  the  Head  . 

11.  Small  Posterior  Straight  Muscle  (Rectus  Capitis  Posticus  Minor 
B.  Inferior  Cervical  or  Trachelian  Region     .... 

1.  Subcutaneous  Muscle  of  the  Neck  (Panniculus  Carnosus)  . 

2.  Mastoido-humeralis  (Levator  Humeri). 

3.  Sterno-maxillaris  ...... 

4.  Sterno-hyoideus  ...... 

5.  Sterno-thyroideus.  ..... 

6.  Omo-hyoideus,  or  Subscapulo-hyoideus 

7.  Great  Anterior  Straiglit  Muscle  of  the  Head  (Pectus  Capitis  Anticus 

Major)  ...... 

8.  Small  Anterior  Straight  Muscle  of  the  Head  (Eeetus  Capitis  Anticus 

Minor)  ...... 

9.  Small  Lateral  Straight  Muscle  (Obliquus  Capitis  Anticus) 

10.  Scalenus  ...... 

11.  Long  Muscle  of  the  Neck  (Longus  Colli)   . 
Differential  Characters  in  the  Muscles  of  the  Cervical  Region  of  other 

Soliped  Animals     ...... 

A.  Superior  Cervical  Region         .... 

B.  Inferior  Cervical  or  Trachelian  Region 
Spinal  Region  of  the  Back  and  Loins 

1.  Trapezius  ...... 

2.  Great  Dorsal  (Latissimus  Dorsi) 

3.  Small  Anterior  Serrated  Jluscle  (Superficialis  Costarum) 

4.  Small  Posterior  Serrated  Muscle  (Superficialis  Costarum) 

5.  Ilio-spinalis  Muscle  (Longissimus  Dorsi) 

6.  Common  Intercostal  Muscle  (Transversalis  Costarum) 

7.  Transverse  Spinous  Muscle  of  the  Back  and  Loins  (Spinalis  and 

Semispinalis  Dorsi  ...... 

Differential  Ciiaracters  in  the  Muscles  of  the  Spinal  Region  of  the  Back  and 
Loins  of  other  than  Soliped  Animals    ..... 

Comparison  of  the  Muscles  of  the  Back,  Neck,  and  Cervix  in  Man  with  the 
analogous  Muscles  in  the  Domesticated  Animals 
A.  Muscles  of  the  Back  and  Cervix    ..... 


PAGE 

178 
180 
181 
183 
183 
186 
186 
186 
186 
187 
187 
188 
189 
189 
191 
191 
193 
193 
193 
194 
195 
195 
195 
196 
196 
198 
198 
198 
198 

199 

199 
199 
200 
200 

201 
201 
201 
203 
203 
203 
205 
205 
206 
208 

209 

209 

209 
210 


TABLE  OF  CONTENTS.  xxi 

PAGE 

B.  Muscles  of  the  Neck  .  .  .  .        ,     .  .  .211 

Sublumbar  or  Inferior  Lumbar  Ecgion  .  .  .  .  211 

1.  Iliac  Fascia  or  Lumbo-iliac  Aponeurosis       ....  212 

2.  Great  Psoas  Muscle        ......  212 

3.  Iliac  Psoas  Muscle  (Iliacus) ......  212 

4.  Small  Psoas  Muscle        ......  214 

5.  Square  Muscle  of  the  Loins  (Sacrn-lumbalis)  .  .  .  214 

6.  Intertransverse  Muscles  of  the  Loins  (Intertransversales  Lumborum)  215 
Differential  Characters  in  the  Muscles  of  the  Sublumbar  Region  of  other 

than  Soliped  Animals  .......  215 

Comparison  of  the  Sublumbar  Muscles  of  Man  with  those  of  Animals    .  215 

Coccygeal  Region .  .......  215 

1.  Sacro-coccygeal  Muscles  .  .  .  .  •  215 

2.  Ischio-coccygeus  (Compressor  Coccygeus)     ....  217 
Region  of  the  Head  .....•■  217 

A.  Facial  Region  .......  217 

1.  Labialis  (Orbicularis  Oris)     .....  217 

2.  Alveolo-labialis  (Buccinator)         .....  218 

3.  Zygomatico-labialis  (Zygomaticus)      ....  219 

4.  Lachrymo-labial,  or  Lachrymal  Muscle     ....  220 

5.  Supernaso-labialis  (Levator  Labii  Superioris)  .  .  220 

6.  Supermaxillo-labialis  (Nasalis  Longus  Labii  Superioris)    .  .  220 

7.  Great  SupermaxiUo  Nasalis  (Dilatator  Naris  Lateralis)  .  221 

8.  Small  Supermaxillo-nasalis  (Nasalis  Brevis  Labii  Superioris)         .  221 

9.  Transversalis  Nasi  (Dilatator  Naris  Anterior ) .  .  .  221 

10.  jMiddle  Anterior  Muscle  (Depressor  Labii  Superior!)  .  .  222 

11.  Maxillo-labialis  (Depressor  Labii  Iiiferiorisj    .  .  ,  222 

12.  Mento-labialis,  or  Muscle  of  the  Chin        .  .  .  .222 

13.  Middle  Posterior  Muscle  (Levator  Menti)        ...  222 

B.  Masseterine  or  Temporo-maxillary  Region    ....  223 

1.  Masseter         .......  223 

2.  Temporal  or  Crotaphitic  Muscle    .....  223 

3.  Internal  Pterygoid  (Pterygoidtus  Internus)    .  .  .  224 

4.  External  Pterygoid  ......  224 

5.  Digastricus     .......  225 

c.  Hyoideal  Region      .......     225 

1.  Mylo-hyoideus  ......  225 

2.  Genio-hyoideus     .......     226 

3.  Stylo-hyoideus  (Hyoideus  Magnus)     ....  227 

4.  Kerato-hyoideus  (Hyoideus  Parvus)  ....     227 

5.  Occipito-styloideus      ......  227 

6.  Tranversalis  Hyoidei  ■       .  •  .  •  •  •     228 
Differential  Characters  in  the  Muscles  of  the  Head  of  other  than  Soliped 

Animals  ....••••     228 

A.  Facial  Region        ....•••  228 

u.  Masseterine  or  Temporo-maxillary  Region        ....     -29 

c.  Hyoid  Region        .....••  ^30 

Comparison  of  the  Muscles  of  the  Human  Head  with  those  of  the  Domes 

ticated  Animals      ....••• 

A.  Epicranial  Muscles      .  .  .  •  •  •         »  ' 

B.  Muscles  of  the  Fiice  ...••• 
c.  IMuscles  of  the  Lower  Jaw        .  .  •  •  • 
D.  Hvoid  Muscles      ....•••  -^'■ 

9Q1 

Axillary  Region  ....•••  •    " 


230 
230 
230 
231 


TABLE  OF  CONTENTS. 

1.  Superficial  Pectoral  (Pi ctoralis  Transversus) 

2.  Deep  Pectoral  ..... 
Difi'ereatial  Characters  in  the  Muscles  of  the  Axillary  Ivegiou  of  other  than 

Soliped  Animals  ..... 

Costal  Kegion  ..... 

1.  Great  Serralus  ..... 

2.  Transverse  Muscle  of  the  Ribs  (Lateralis  Sterni) 

3.  External  lutercostals  .... 

4.  Internal  Intercostala       .... 

5.  Supercostals  (Levatores  Costarum)  . 

6.  Triangularis  of  the  Sternum  (Stenio-co.^tales)     . 
Differential  Characters  in  the  Muscles  of  the  Costal  Eegion  of  other  than 

Soliped  Animals    ..... 

Comparison  of  the  Thoracic  Muscles  of  Man  with  those  of  the  D(  mesticated 
Animals     ...... 

Inferior  Abdominal  Kegion  .... 


1.  Abdominal  Tunic  .... 

2.  White  Line.  .... 

3.  Great  or  External  Oblique  of  the  Abdomen 

4.  Small  or  Internal  Oblique  of  the  Abdomen    . 

5.  Great  Rectus  Muscle  of  the  Abdomen     . 

6.  Transverse  Muscle  of  the  Abdomen  ..... 
Ditferential   Characters  in   the  Muscles  of  the  Abdominal  Region  of  other 

than  Soliped  Animals  ...... 

Comparison  of  the  Abdominal  Muscles  of  Man  with  those  of  Animals 
Diaphragmatic  Region  ...... 

Diaphragm  ........ 

Differential  Characters  in  the  Diaphiagm  of  other  than  S<i]iped  Animals 
Comparison  of  the  Diaphragm  of  Man  with  that  of  Animals 
Article  ii. — Muscles  of  the  Anterior  Limbs     ..... 

Muscles  of  the  Shoulder  ...... 

A.  External  Scapular  Regicm       ...... 

1.  External  Scapular  Aponeurosis  ..... 

2.  Long  Abductor  of  the  Arm,  or  Scapular  portion  of  the  Deltoid  (^ Teres 

Major)      ...... 

3    Short  Abductor  of  the  Arm,  or  Teres  Minor 

4.  Superspinatus  (Antea  Spinatus) 

5.  Subspinatus  (Postea  Spinatus;   . 

B.  lutomal  Scapular  Region         .... 

1.  Subscapularis     ..... 

2.  Adductor  of  the  Arm,  or  Teres  Major 

3.  Coraco-humeralis,  Coiaco-brachialis,  or  Omo-brachialis 

4.  Small  Scapulo-humeralis      .... 
Differential  Characters  iu  the  Bluscles  of  the  Shoulder  of  other 

Animals     ...... 

Comparison  of  the  IMusclcs  of  the  Shoulder  of  Man  with  those  of 
Muscles  of  the  Arm       . 

A.  Anterior  Brachial  Region         .... 

1.  Long  Flexor  of  the  Fore-arm,  or  Brachial  L'iceps  (Flexor 

2.  Short  Flexor  of  the  Fore-arm  (Humeralis  Externus) 

B.  Posterior  Brachial  Region        .... 

1.  Long  Extensor  of  the  Fore  arm  (Caput  Magnum) 

2.  Large  Extensor  of  the  Fore-arm  (Caput  Magnum)    . 

3.  Slioit  Extensor  of  the  Fore  arm  (Caput  Medium) 


tlian  Soliped 


Animals 


BracLiiy 


FAGG 

231 
233 

235 
235 
236 
236 
237 
237 
237 
237 

238 

238 
238 
239 
240 
240 
2i2 
243 
244 

24.i 
245 
246 
240 
248 
248 
248 
249 
249 
249 

249 
250 
251 
251 
252 
252 
253 
2.54 
254 

254 
255 
255 
255 
255 
256 
258 
258 
258 
259 


TABLE  OF  CONTENTS. 

i.  IMiddle  Extensor  of  the  Fore-arm  (Caput  Parvum) 

5.  Small  Extensor  of  the  Fore-arm,  or  Anconeus 
Diflferential  Characters  in  the  Muscles  of  the  Arm  of  other  than  Solipecl 

Animals     ....•••• 

Comparison  of  the  Muscles  of  the  Arm  of  Man  with  those  of  Animals 
a\Iuscles  of  the  Fore-arm  ...... 

Aniibrachial  Aponeurosis     ....... 

A.  Anterior  Antibrachial  Region        ..... 

1.  Anterior  Extensor  of  the  Metacarpus  (Extensor  Metacarpi  ^lasnus") 

2.  Oblique  Extensor  of  the  Metacarpus  (Extensor  Metacarpi  Oi-li  ,uus) 

3.  Anterior  Extensor  of  the  Phalanges  (Extensor  Pedis 

4.  Lateral  Extensor  of  the  Phalanges  (Extensor  Suffiaginis) 

B.  Posterior  Antibrachial  Region  ..... 

1.  External  Flexor  of  the  Meticarpus,  or  Posterior  Ulnaris. 

2.  Oblique   Flexor   of  the   Jletacarpus,  or  Anterior  Ulnaris   (Flexor 

Metacarpi  Medius)  ...... 

3.  Internal   Flexor  of  the  Jlttacarpus,  or  Palmaris  Magnus  (Flexor 

Metacarpi  Internus) 

4.  Superficial  Flexor,  Sublimis  of  the  Phalanges,  or  Perforatus 

5.  Deep  Flexor  of  the  Phalanges,  or  Perlbrans 
Dififerential  Characters  in  the  Muscles  of  the  Fore-arm  of  other  than  Soliped 

Animals  ..... 

Muscles  proper  to  the  Fore-arm  in  Camivora  . 

1.  Proper  Extensor  of  the  Thumb  and  Index    . 

2.  Long  Supinator. 

3.  Short  Supinator        .... 

4.  Round  Pronator 

5.  Square  Pronator       .... 
Comparison  of  the  Muscles  of  the  Fore-arm  of  Man  witli  those  of  Animals 

A.  Anterior  Region  .  .  .  • 

B.  External  Region    .... 
c.  Posterior  Region  .  .  .  • 

Muscles  of  the  Anterior  Foot  or  Hand   . 

A.  Muscles  of  the  Anterior  Foot  in  Carnivora 

1.  Short  Abductor  of  the  Thumb    . 

2.  Opponens  of  the  Thumb 

3.  Short  Flexor  of  the  Thumb 

4.  Adductor  of  the  Index 

5.  Cutaneous  Palmar   P.dmaris  Brevis)      . 

6.  Adductor  of  the  Small  Digit 

7.  Short  Flexor  of  the  Small  Digit 

8.  Opponens  of  the  Small  Digit 

9.  Lumbrici  .... 
10.  Metacarpal  Interosseous  Mmcles 

B.  Muscles  of  the  Anterior  Foot  in  the  Pig    . 
c.  Muscles  of  the  Anterior  Foot  in  Solipeds 
D.  Muscles  of  the  Anterior  Foot  in  Ruminants 

Comparison  of  the  Hand  of  Man  with  that  of  Animals 

A.  Muscles  of  the  Thenar  Eminence  . 

B.  Muscles  of  the  Hypolhenar  Eminence, 
c.  Interosseous  IMuscles 

Article  in.— Muscles  of  the  Posterior  Limbs 
Muscles  of  the  Gluteal  Region,  or  Croup 

1.  Superficial  Gluteus   Gluteus  Externus) 


sxui 

PAGE 

259 
260 

260 

260 

261 

261 

262 

262 

263 

263 

264 

265 

265 

266 

266 
267 
268 

270 
272 
272 
272 
274 
274 
274 
274 
274 
276 
276 
276 
276 
276 

,  277 
277 
277 
277 

,  277 
277 

,  277 
278 

,  278 
278 

,  278 
279 

,  279 
279 
279 
279 

,  280 
280 
280 


TABLE  OF  CONTENTS. 

PAGE 

2.  Middle  Gluteus  (Gluteus  Maximus)       ....  281 

3.  Deep  Gluteus  (Gluteus  Internus)     .....  282 
Dififerential  Characters  in  the  Muscles  of  the  Gluteal  Eegion  of  other  than 

Soliped  Animals     .......  283 

Comparison  of  the  Gluteal  Muscles  of  Man  with  those  of  Animals  .             .  283 

Muscles  of  the  Thigh              ......  283 

A.  Anterior  Crural,  or  Femoral  Eegion     .....  283 

1.  Muscle  of  the  Fascia  Lata  (Tensor  Vaginse)        .             .             .  284 

2.  Crural  Triceps  .  .  .  .  .  .  .284 

3.  Anterior  Gracilis  (Crureus  vel  Cruralis).             .             .             .  285 

B.  Posterior  Crural  Region           ......  286 

1.  Long  Vastus  (Biceps  Abductor  Femoris)             .             .             .  286 

2.  Semitendinosus  Muscle  (Adductor  Tibialis)              .             .             .  287 

3.  Semimembranosus  (Adductor  Tibialis';   ....  288 
c.  Internal  Crural  Region             ......  288 

1.  Long  Adductor  of  the  Leg  (Sartorius)     ....  288 

2.  Short  Adductor  of  the  Leg  (Gracilis)  .  .  .  .289 

3.  Pectineus           .......  289 

4.  Small  Adductor  of  the  Thigh  (Adductor  Femoris)  .  .  .291 

5.  Great  Adductor  of  the  Thigh  (Adductor  Longus)            .             .  291 

6.  Square  Crural  (Quadratus  Femoris).             ....  292 

7.  External  Obturator         ......  292 

8.  Internal  Obturator  .  .  .  .  .  .  .292 

9.  Gemelli  of  the  Pelvis  (Gemini)  .             ....  293 
Differential  Characteis  in  the  Muscles  of  the  Thigh  of  other  than  Soliped 

Animals  .  .  .  .  .  .  .  .294 

A.  Anterior  Crural  Eegion     ......  294 

B.  Posterior  Crural  Region           ......  294 

c.  Internal  Crural  Eegion      ......  295 

Comparison  of  the  Muscles  of  Man's  Thigh  with  tliose  of  the  Thigh  of 

Animals            ........  295 

A.  Anterior  Muscles  .......  295 

B.  Muscles  of  the  Posterior  Eegioii            .....  295 

c.  Muscles  of  the  Internal  Region      .....  296 

Muscles  of  the  Leg  .  .  .  .  .  .  .297 

Tibial  Aponeurosis     .......  297 

A.  Anterior  Tibial  Region  .  .  .  .  .  .298 

L  Anterior  Extensor  of  the  Phalanges  (Extensor  Pedis)      .             .  298 

2    Lateral  Extensor  of  the  Phalanges  (Peroneus)          .             .             .  298 

3.  Flexor  of  the  Metat;irsus            .....  300 

B.  Posterior  Tibial  Region            ......  302 

1.  Gastrocnemii,  or  Gemelli  of  the  Tibia  (Gastrocnemius  Externus)  302 

2.  Soleus,  or  Solearis  (Plantaris)     .....  304 

3.  Superficial  Flexor  of  the  Pha'anges,  or  Perforatus  (Gastrocnemius 

Internus)  ........  304 

4.  Popliteus            .......  304 

5.  Deep  Flexor  of  the  Phalanges,  or  Perforans  (Flexor  Pedis)  .             .  305 

6.  Oblique  Flexor  of  the  Phalanges  (Flexor  Pedis  Accessorius)      .  306 
Differential  Characters  in  the  Muscles  of  the  Leg  of  other  than  Soliped 

Animals            ....                          ...  306 

A.  Anterior  Tibial  Region      .             .             .             .             •         •    •  306 

B.  Posterior  Tibial  Region            ......  309 

Comparison  of  the  Muscles  of  the  Leg  of  Man  with  those  of  Animals     .  309 

A.  Anterior  Region          .......  309 


TABLE  OF  CONTENTS.  xxv 

PAGE 

B.  External  Region    .......  309 

c.  Posterior  Eegion  .......     309 

Muscles  of  the  Posterior  Foot  .  .  .  .  .311 

Comparison  of  the  Muscles  of  the  Foot  of  Man  with  those  of  Animals  .     311 

A.  Dorsal  Eegion       .  .  .  .  .  .  .811 

B.  Plantar  Region  .  .  .  .  .  .  .312 

c.  Interosseous  Muscles  ......  313 

Chapter  III. — The  :Muscles  in  Birds    .  .....     313 

Chapter  FV. — General  Table  of  tlie  insertions  of  the  Muscles  in  Solipeds     .  315 

BOOK  II. 

THE   DIGESTIVE   APPARATUS. 

Chapter  I. — General  Considerations  on  the  Digestive  Apparatus    .  .  325 


330 
330 
330 
330 
332 
332 
334 
340 
344 


Chapter  II. — The  Digestive  Apparatus  in  Mammalia     . 
Article  i. — Preparatory  Organs  ot  the  Digestive  Apparatus 
The  Mouth  ..... 

1.  Lips       ...... 

2.  Cheeks         ..... 

3.  Palate   ...... 

4.  Tongue        ..... 

5.  Soft  Palate        ..... 

6.  Teeth  ..... 

7.  The  Mouth  in  General  ......  355 

Differeutial  Characters  in  the  :Mouth  of  other  than  SoMped  Animals  .     356 

Comparison  of  the  Mouth  of  ]\Ian  with  that  of  Animals  .  .  362 

The  Salivary  Glands        .......     364 

1.  Parotid  Gland  .......  365 

2.  Maxillary,  or  Submaxillary  Gland  .....     367 

3.  Sublingual  Gland  ......  369 

4.  Molar  Glands  .  .  .  .  •.  .  .369 

5.  Labial,  Lingual,  and  Palatine  Glands    ....  370 
Differential  Characteis  in  the   Salivary   Glands  of   other  than    Soliped 

Animals  ....... 

Comparison  of  the  Salivary  Glands  of  Man  with  those  of  Animals 
The  Pharyux       ....... 

Differential  Characters  in  the  Pharynx  of  other  than  Soliped  Animals  . 
Comparison  of  the  Pharyux  of  Man  with  that  of  Animals    . 

The  CEsuphagus         ....... 

Differential  Characters  in  the  (Esophagus  of  other  than  Soliped  Animals 
Comparison  of  the  Esophagus  of  Man  with  that  of  Animals 
Article  ii. — The  Essential  Organs  of  Digestion 

The  Abdominal  Cavity  ......  380 

Differential  Characters  in  the  Abdominal  Cavity  of  other  than   Soliped 
Animals  ....... 

Comparison  of  the  Abdominal  Cavity  of  Man  with  that  of  Animals 
The  Stomach        ....... 

1.  The  Stomach  of  Solipeds  .... 

Differential  Characters  in  the  Stomach  of  other  (han  Soliped  Animals 

1.  The  Stomach  of  the  Pig  .... 

2.  The  Stomach  of  Carnivora   ..... 

3.  The  Stomach  of  Ruminants         .... 
Comparison  of  the  Stomach  of  Man  with  that  of  Animals    . 


.370 
372 
372 
376 
377 
377 
380 
380 
3"80 


384 
385 
385 
385 
393 
393 
393 
393 
400 


xvi  TABLE  OF  CONTENTS. 

PAGE 

The  Intestines           .......  400 

1.  The  Small  Intestine             •••...  400 

2.  The  Large  Intestine       ....,,  407 

A.  Caecum            ........  407 

B.  Colon        ........  410 

c.  Rectum            ........  413 

Differential  Characters  in  the  Intestines  of  other  than  Soliped  Animals  .  414 

1.  The  Intestines  of  Ruminants              .....  414 

2.  The  Intestines  of  the  Pig            .....  416 

3.  The  Intestines  of  Carnivora  .....  416 
Comparison  of  the  Intestines  of  Man  with  tl:ose  of  Animals  .  .  417 
General  and  Comparative  Survey  of  the  Abdominal  or  Essential  Portion  of 

the  Digestive  Canal      .......  418 

Organs  Annexed  to  the  Abd:'minal  Portion  of  the  Digestive  Canal     .  419 

1.  Liver            ........  419 

2.  Pancreas             .......  427 

3.  Spleen          .             .             .             .             .             .      ■       .             ,  428 

Differential  Characters  in  the  Organs  Annexed  to  the  Abdominal  Portion  of 

the  Digestive  Canal  in  other  than  Soliped  Animals  .  .  432 
Comparison  of  the  Organs  Annexed  to  the  Abdominal  Portion  of  the  Digestive 

Canal  of  Man  with  those  of  Animals    .....  434 

Chapter  III.— The  Digestive  Apparatus  of  Birds    ....  435 


BOOK  III. 
RESPIRATORY   APPARATUS. 

Chapter  I.— Respiratory  Apparatus  in  Mammalia         ....     439 

The  Nasal  Cavities    .......  439 

L  The  Nostrils  .  .  .  .  .  .  .440 

2.  The  Nasal  Fossse  ......  441 

3.  The  Sinuses  .  .  ,  .  .  .  .446 
Differential  Characters  in  the  Nasal  Cavities  of  other  than  Soliped  Animals  448 
Comparison  of  the  Nasal  Cavities  of  Man  with  those  of  Animals              .  449 

Tlie  Air-tube  succeeding  the  Nasal  Cavities  ....     449 

1.  The  Larynx        -  ......  449 

2.  The  Trachea  ,  .  .  .  .  .457 

3.  The  Bronchi      .......  460 

Differential  Characters  in  the  Air-tube  succeeding  the  Nasal  Fossye  of  other 

than  Soliped  Animals  .....  461 

Comparison  of  the  Larynx  a  .d  Tiachea  of  Man  with  these  Organs  in  the 

Domesticated  Animals        ......  462 

'i'hc  Thorax  .  .  .  .  .  .  .462 

Differential  Characters  in  the  Thorax  of  other  than  Soliped  Animals  466 

The  Lungs           .                            ......  466 

Differential  Characters  in  tlie  Lungs  of  other  than  Soliped  Animals        .  470 
Comparison  of  the  Larynx.   Trachea,  and  Lungs  of  Man  with  the  same 

Organs  in  Animals                      ......  471 

The  Glandif(n-m  Bodii  s  connected  with  the  Respiratory  Apparatus     .  472 

1.  The  Tliyroid  Body   .  .  .  .  .  .  .472 

2.  Tlie  Thymus  Gland        ......  473 

Differential  CliAracters  in  the  Glandiform  Bodies  annexed  to  the  Respiratory 

Apparatus  of  other  than  Soliped  Animals  ....     474 


TABLE  OF  CONTENTS.  xxvii 

I- AGE 

Comparison  of  the  Glandiform  Bodies  annexed  to  the  Kespiratory  Apparatus 

in  Man  with  those  of  Animals         .....  475 

Chapter  II.— The  Respiratory  Apparatus  of  Birds         ....     475 


BOOK  IV. 

■   URINARY   APPARATUS. 

1.  The  Kidneys             .......  484 

2.  The  Ureters        .              .              .              .              .                            .  .490 

3.  The  Bladder             .......  491 

4.  The  Urethra        .             .             .             .             .             .             .  .493 

5.  The  Suprarenal  Capsules       ......  494 

Diflerential  Characters  of  the  Urinary  Apparatus  in  other  than   Soliped 

Animals  ........     495 

Comparison  of  the  Urinary  Apparatus  of  Man  with  that  of  Animals       .  496 


BOOK  V. 

CIRCULATORY    APPARATUS. 

First  Section. — The  Henrt           .             .            .            .            ...  499 

1.  The  Heart  as  a  Whole           ......  499 

2.  External  Conformation  of  the  Heart         .....  500 

3.  Internal  Conformation  of  the  Heart  .....  503 

4.  Structure  of  the  Heart     .......  507 

5.  The  Pericardium       .......  512 

6.  The  Action  of  the  Heart.  .  .  .  .  .  .513 

Differential  Characters  in  tlie  Heart  of  otiar  than  Soliped  Animals       .  513 

Comparison  of  the  Heart  of  Man  with  that  of  Animals         .             .             .  514 

Second  Section. — The  Arteries           ......  515 

Chapter  I. — General  Considerations      ......  515 

Chapteu  II. — Pulmonary  Artery      ......  521 

CHAPrER  III. — Aorta      ........  522 

Article  i.—  Common  Aorta,  or  Aortic  Trunk          ....  522 

Cardiac,  or  Coronary  Arteries       ......  523 

Ai'ticle  II. — Posterior  Aorta           ......  523 

Parietal  Branches  of  the  Posterior  Aorta  .....  525 

1.  Intercostal  Arteries         ......  525 

2.  Lumbar  Arteries       .......  526 

3.  Diaphragmatic  Arteries              .....  526 

4.  Middle  Sacral  Artery  .  .  .  .  .  .526 

Visceral  Branches  of  the  Posterior  Aorta       ....  526 

1.  Broncho-ffisophageal  Trunk             .....  526 

2.  Coeliac  Artery    .......  527 

3.  Great  Mesenteric  Artery      ......  529 

4.  Small  Mesenteric  Artery             .....  532 

5.  Eenal,  or  Emulgeut  Arteries             .....  534 

6.  Spermatic  Arteries          ......  534 

7.  Small  Testicular  Arteries  (Male),  Uterine  Arteries  (Female)             .  .535 
Differential  Characters  in  the  Posterior  Aorta  and  its  Collateral  Branches  of 

other  than  Solipeel  Animals             .....  535 

1.  Posterior  Aorta  in  Ruminants           .....  535 

2.  Posterior  Aorta  in  the  Pig          .....  537 

3.  Posterior  Aorta  in  Carnivora              .....  537 
Comparison  of  the  Aorta  of  Man  with  that  of  Animals  .             .             .  538 


iii  TABLE  OF  CONTENTS. 

PAGE 

Article  in. — Internal  Iliac  Arteries,  or  Pelvic  Trunks              .             .             .  638 

1.  Umbilical  Artery  .....••  538 

2.  Internal  Piulic,  or  Bulbous  Artery        .....  540 

3.  Subsacral,  or  Lateral  Sacral  Artery             ....  540 

4.  Iliaco-muscular,  or  Ilio-lumbar  Artery              .    '         .              .              .  541 

5.  Gluteal  Artery      .......  542 

6.  Obturator  Artery  .  .  .  .  .  •  .542 

7.  Iliaco-femoral  Artery         ......  543 

Diiferential  Characters  in  the  Internal  Iliac  Arteries  of  otlier  than  SolipL'd 

Animals  ....••••     543 

1.  Internal  Iliac  Arteries  of  Eumiuants       ....  543 

2.  Internal  Iliac  Arteries  of  the  Pig      .  .  .  .  .544 

3.  Internal  Iliac  Arteries  of  the  Carnivora  ....  544 
Comparison  of  the  Internal  Iliac  Arteries  of  Jlan  with  those  of  Animals      .     545 

Article  iv.— External  Iliac  Arteries,  or  Crural  Trunks      .  .  .  .  545 

Femoral  Artery   ...  ....  547 

1.  Prepubic  Artery  ......  547 

2.  Deep  Femoral,  Deep  Muscular,  or  Great  Posterior  Muscular  Artery  of 

the  Thigh  .  .  .  .  .  .  .548 

3.  Superficial  Muscular,  or  Great  Anterior  Muscular  Artery  .  548 

4.  Innominate  Muscular,  or  Small  Muscular  Arteries    .  .  .     549 

5.  Saphena  Artery  ......  549 

Popliteal  Artery  ........     549 

Terminal  Branches  of  the  Popliteal  Artery     ....  550 

1.  Posterior  Tibial  Artery         .  .  .  .  .  .550 

2.  Anterior  Tibial  Artery  .  .  .  .  .551 

3.  Pedal  Artery  .  .  .  .  .  •  .551 
Differential  Characters  in  the  External  Iliac  Arteries  of  other  than  Soliped 

Animals     ........  555 

1.  External  Iliac  Arteries  of  Ruminants     •       .  .  .  .  555 

2.  External  Iliac  Arteries  of  the  Pig  ....  556 

3.  External  Iliac  Arteries  of  Carnivora              ....  556 
Comparison  of  the  External  Iliac  Arteries  of  Man  witii  those  of  Animals  557 

Article  v. — Anterior  Aorta            ......  559 

Article  vi. — Axillary  Arteries,  or  Brachial  Trimks      ....  559 

Collateral  Branches  of  the  Axillary  Arteries  ....  560 

1.  Dorsal,  Dorso-muscular,  or  Transverse  Cervical  Artery         .             .  560 

2.  Superior  Cervical,  Cervico-muscular,  or  Deep  Cervical  Artery     .  561 

3.  Vertebral  Artery      .  .  .  .  •  •  .561 

4.  Internal  Thoracic,  or  Internal  Mammary  Artery              .              .  563 

5.  External  Thoracic,  External  Mammary,  or  Inferior  Thoracic  Artery  563 

6.  Inferior  Cervical  Artery              .             .             .             .             •  564 

7.  SuperscapuLir  Artery           ......  564 

8.  Subscapular  Artery        ......  564 

Terminal  Branch  of  the  Brachial  Trunk,  or  Humeral  Artery        .             .  565 

1.  Anterior  Radiul  Artery  ......  566 

2.  Posterior  Eadial  Artery        .  .  .  .  .  .567 

1.  First  Terminal  Branch  of  the  Posterior  Eadial  Artery,  or  Common 

Trunk  of  the  Interosseous  ]\Ietacarpals         .  .  .  568 

2.  Second  Terminal  Branch  of  the  Posterior  Eadial  Artery,  or  Colla- 

teral Artery  of  the  Canon  .....  569 

Differential  Characters  in  the  Axillary  Arteries  of  Non-soliped  Animals  570 

1.  Axilliiry  Arteries  of  Euminants         .  .  .  .  •  570 

2.  Axillary  Arteries  of  the  Pig       .  .  •  •  •  ^72 


TABLE  OF  CONTENTS. 


3.  Axillary  Arteries  of  Carnivora  . 
Comparison  of  the  Axillary  Arteries  of  Man  with  those  of  Animals 
Aiticle  VII. — Common  Carotiii  Arteries 
Occipital  Ai  tery 

Internal  Carotid  Artery  .... 

External  Carotid  Artery  ..... 

1.  External  Maxillary,  Facial,  or  Glosso-Facial  Artery 

2.  Maxillo-Muscular  Artery     .... 

3.  Posterior  Auricular  Artery 

4.  Superficial  Temporal  Artery,  or  Temporal  Trunk 

5.  Internal  Maxillary,  or  Gutluro-maxillary  Artery 
Differential  Characters  in  the  Carotid  Arteries  of  Non-soliped  Animals 

1.  Carotid  Arteries  of  Carnivora     . 

2.  Carotid  Arteries  of  the  Pig  . 

3.  Carotid  Arteries  of  Kuminants  . 
Comparison  of  the  Carotid  Arteries  of  Man  with  those  of  Animals 

Third  Section. — The  Veins    .... 
Chapter  I. — General  Considerations 

Chapter  II. — Veins  of  the  Lesser  Circulation,  or  Puhuonary  Veins 
Chapter  III. — Veins  of  t!ie  General  Circulation 
Article  i. — Cardiac,  or  Coronary  Veins     . 
Article  n. — Anterior  Vena  Cava 

Jugular  Veins  .... 

Boots  of  the  Jugular         .... 

1.  Superficial  Temporal  Vein 

2.  Internal  Maxillary  Vein 

3.  The  Sinuses  of  the  Dura  Mater  . 
Axillary  Veins    ..... 

1.  Subscapular  Vein 

2.  Humeral  Vein  .... 

3.  Spur,  or  Subcutaneous  Thoracic  Vein     . 

4.  Deep  Veins  of  the  Fore-arm 

5.  Superficial  Veins  of  the  Fore-arm 

6.  Metacarpal  Veins     .... 

7.  Digital  Veins     .... 

8.  Veins  of  the  Foot,  or  Ungual  Eegion 

a.  External  Venous  Apparatus  . 

b.  Internal,  or  Intra-osseous  Venous  Apparatus 
Article  in. — Posterior  Vena  Cava 

Diaphragmatic  Veins 

Vena  Portse  ..... 

1.  Boots  of  the  Vena  Portse 

2.  Lateral  Affluents  of  the  Vena  Portis 
Eenal  Veins         .... 
Spermatic  Veins         .... 
Lumbar  Veins      .... 
Common  Iliac  Veins,  of  Pelvi-crural  Trunks 

1.  Internal  Iliac  Vein  . 

2.  External  Iliac  Vein 

3.  Femoral  A'ein 

4.  Popliteal  Vein  .... 

5.  Deep  Veins  of  the  Leg 

6.  Superficial  Veins  of  the  Leg 

7.  Metatarsal  Veins 

8.  Veins  of  the  Digital  Eegion 


xxs  TABLE  OF  CONTENTS. 

PAGE 

Differential  Characters  in  the  Veins  of  other  than  Soliped  Animals  .  .     625 

Comparison  of  the  Veins  of  Man  with  those  of  Animals  .  .  G26 

FoUKTH  Section. — The  Lymphatics  ......     G27 

Chapter  T. — General  Considerations  .....  627 

Lymphatic  Vessels  .......     627 

Lymphatic  Glands,  or  Ganglia  .....  632 

Chapter  II. — The  Lymphatics  in  Particular      .....     634 

Article  i. — The  Thoracic  Duct      ......  634 

Article  ii. — The  Lymphatics  -which  constitute  the  Affluents  of  the  Thoracic 

Duct 637 

Lymphatics  of  the  Abdominal  Limb,  Pelvis,  Abdominal  Parietes,   and 
Pelvi-inguinal  Organs      .... 

1.  Sublumbar  Glands  .... 

2.  Deep  Inguinnl  Glands    .... 

3.  Superficial  Inguinal  Glands 

4.  Popliteal  Glands  .... 

5.  Iliac  Glands  .... 

6.  Precrural  Glands  .... 
Lymphatics  of  tlie  Abdominal  Viscera 

1.  Glands  and  Lymjjhatic  Vessels  of  the  Kectura  and  Floa 

2.  Glands  and  Lymphatic  Vessels  of  the  Large  Colon 

3.  Glands  and  Lymphatic  Vessels  of  the  Cajcum 

4.  Glands  and  Lymphatic  Vessels  of  the  Small  Intestine 

5.  Glands  and  Lymphatic  Vessels  of  the  Stomach 

6.  Glands  and  Lymphatic  Vessels  of  the  Sj^leen  and  Liver 
Glands  and  Lympl.atic  Vessels  of  the  Organs  contained  in  the  Thoracic 

Cavity  ...... 

Glands  and  Lymphatic  Vessels  of  the  Thoracic  Parietes 
Lymphatic  Vessels  of  the  Head,  Neck,  and  Anterior  Limb 

1.  Prepectoral  Glands        ..... 

2.  Pliaryngeal  Glands  ..... 

3.  Submaxillary,  or  Subglossal  Glands 

4.  Prescapular  Glands  .... 

5.  Brachial  Glands  ..... 
Article  iii. — Great  Lymphatic  Vein     .... 

Differential  Characters  in  the  Lymphatics  of  N"on-soliped  Animals 
Chapter  III. — The  Circulatory  Apparatus  in  Birds 

Article  i. — The  Heart        ...... 

Article  ii. — The  Arteries         ..... 

Article  in. — The  Veins     ...... 

Article  iv. — The  Lymphat'cs      .... 


638 
.  638 

638 
.  638 

640 
.  640 

640 

.  640 

ing  Colon    640 

641 
.  641 

641 
.  641 

642 


642 
642 
643 
643 
643 
644 
644 
644 
644 
64.5 
647 
647 
648 
649 
649 


BOOK  VI. 
APPAK-VTUS    OF    INNERVATION. 

First  Sectiox.— The  Nervous  System  in  General         ....  G.'iO 

General  Conformation  of  the  Nervous  System  ....  6.'51 
Structure  of  the  Nervous  System         .....  652 

Properties  and  Functions  of  the  Nervous  Systems  .  .  .     655 

Seconp  Section.— The  Central  Axis  of  the  Nervous  System     .  .  .659 

Chapter  I.— Protective  and  Enveloping  Parts  of  the  Cerebri)- spinal  Axis  659 

The  Bony  Case  which  lodges  the  Central  Cerebro-spinal  Axis  ,  659 

1.  The  Spinal  Catial     .  .  ■  •  •  •  .659 

2.  The  Cranial  Cavity         ......  660 


TABLE  OF  CONTEXTS.  xxxi 

I'AGK 

The  Envelopes  of  the  Cerebro-spinal  Axis             •             •             .  .     (560 

1.  The  Dura  Plater              ......  tjgl 

2.  The  Arachnoid         ......  ggS 

3.  The  Pia  Mater  .......  665 

Differential   Characters  in   the  Protecting  and   Envelopini^   Parts  of  the 

Cerebro-spinal  Axis  in  other  tlian  Soliped  Animals        .              .              .  6G6 
Comparison  of  the  Protective  and  Enveloping  Parts  cf  the  Cerebro-spinul 

Axis  of  Man  Mith  those  of  Animals             ....  666 

Chapter  II. — Tiie  Spinal  Cord  .......  666 

External  Conformation  of  the  Spinal  Cord       ....  666 

Internal  Conformation  and  Structure  of  the  Spinal  Cord   .              .              .  668 
Differential  Characters  in  the  Spinal  Cord  of  the  Domesticated  IMammals 

other  than  Solipeds             ......  672 

Comparison  of  the  Spinal  Cord  of  Man  with  that  of  Animals             .             .  672 

Chapter  III. — The  Encephalon        ......  672 

Article  i. — The  Encephalon  as  a  Whole           .....  672 

Aitit'le  II. — The  Isthmus  .......  675 

External  Conformation  of  the  Isthmus      .....  675 

1.  The  Medulla  Oblongata              .....  676 

2.  The  Pons  Varolii      .  .  .  .  .  .  .677 

3.  The  Crura  Cerebri           ......  677 

4.  The  Crura  Cerebeili              ......  678 

5.  The  Valve  of  Vieussens  ......  679 

6.  The  Corpora  Quadvigemina,  or  Bigemina      ....  679 

7.  The  Optic  Thalami         ......  679 

8.  The  Pineal  Gland    .  .  .  .  .  .  .680 

9.  The  Pituitary  Gland      ......  681 

Internal  Conformation  of  the  Isthmus       .....  682 

1.  The  Middle  Ventricle,  or  Ventricle  of  the  Optic  Tiialami  .  682 

2.  The  Aqueduct  of  S.vlvius      .  .  .  .  .  .683 

3.  The  Posterior,  or  Cerebellar  Ventricle     ....  683 
Structure  of  the  Isthmus  .......     683 

Differential  Characters  in  the  Isthmus  of  othei  than  Soliped  Animals    .  685 

Comparison  of  the  Isthmus  of  Man  with  that  of  Animals     .              .  .     685 

Article  iir.— The  Cerebellum          ......  686 

1.  External  Conformation  of  the  Cerebellum     ....     686 

2.  Internal  Conformation  of  the  Cerebellum  .  .  .  688 
Differential  Characters  of  the  Cerebellum  in  other  than  Soliped  Animals  .  689 
Comparison  of  the  Cerebellum  of  Man  with  that  of  Animals       .             .  689 

Article  iv. — The  Cerebrum     .  .  .  .  .  .  .689 

External  Conformation  of  the  Cerebrum         ....  690 

1.  The  Longitudinal  Eissiu-e     ......     690 

2.  The  Cerebral  Hemispheres  ......  691 

Internal  Conformation  of  the  Brain  .....     692 

1.  The  Corpus  Callosum     ......  693 

2.  The  Lateral,  or  Cerebral  Ventricles               ....  693 

3.  The  Septum  Lucidum    ......  694 

4.  The  Cerebral  Trigonum  (or  Fornix)  .  .  .694 

5.  The  Hippocampi             ......  695 

6.  The  Corpora  Striata               ...                            .              .  695 

7.  The  Cerebral  Choroid  Plexus,  and  Velum  Interpositum  .              .  696 
Structure  of  the  Cerebrum              ......  697 

Differential  Characters  in  the  Brain  of  other  than  Soliped  Animals         .  698 

Comparison  of  the  Brain  of  Man  with  that  of  Animals         .  .  .698 


XXXll 


TABLE  OF  CONTENTS. 


Third  Section. — The  Nerves 
Chapter  I. — ThexCranial,  or  Encephalic  Nerves 
1.  First  Pair,  or  Olfactory  Nerves 
'2.  Secoud  Pair,  or  Optic  Nerves  . 

3.  Third  Pair,  or  Conimon  Motor  Ocular  Nerves 

4.  Foiu-th  Pair,  or  Pathetic!  Nerves    . 

5.  Fifth  Pair  or  Trigeminal  Nerves  . 

6.  Sixth  Pair,  or  External  Motor  Ocular  Nerves 

7.  Seventh  Pair,  or  Facial  Nerves 

8.  Eighth  Pair,  or  Auditory,  or  Acoustic  Nerves  . 

9.  Ninth  Pair,  or  Glosso-Pharyngeal  Nerves  . 

10.  Teiith  Pair,  Vagus,  or  Pneumogastric  Nerves 

11.  Eleventh  Pair,  Spinal,  or  Accessory  Nerves  of  the  Pneumogastrics 

12.  Twelfth  Pair,  or  Great  Hypoglossal  Nerves 

Differential  Characters  in  the  Cranial  Nerves  of  other  than  Soliped  Animals 
Comparison  of  the  Cranial  Nerves  of  Man  with  those  of  Animals     . 
Chaptee  II. — Spinal  Nerves  .  .  .  . 

Article  i. — Cervical  Nerves  (Eight  Pairs)        ..... 

Article  ii. — Dorsal  Nerves  (Seventeen  Pairs)  .  .  .  . 

Article  iii. — Lumbar  Nerves  (Six  Pairs)  ..... 

Article  rv.— Sacral  Nerves  (Five  Pairs)     ..... 

Article  v. — Coccygeal  Nerves  (Six  to  Seven  Pairs)      .... 

Article  vi. — Composite  Nerves  formed  by  the  Inferior  Ramuscules  of  the  Spinal 
Branches        ........ 

Diaphragmatic  Nervt  s     ,  .  .  . 

Brachial  Plexus  .  .  .  .  .  .  . 


1.  Diaphragmatic  Branches      .... 

2.  Branch  to  the  Angularis  and  Rliomboideus 

3.  Branch  to  the  Serratus  Magnus,  or  Superior  Thoracic 

4.  Branches  to  the  Pectoral  Muscles,  or  Inferior  Thoracic 

5.  Subcutaneous  Thoracic  Branch 

6.  Branch  to  the  Groat  Dorsal 

7.  Axillary,  or  Circumflex  Nerve 

8.  Nerve  of  Adductor  of  the  Arm,  or  Teres  Major 

9.  Subscapular  Branches 

10.  Superscapular  Nerve 

11.  Anterior  Brachial  Nerve 

12.  Radial  Nerve      .... 

13.  Ulnar,  or  Culjito-cutaneous  Nerve     . 

14.  Median,  or  Cubito-plantar  Nerve 
Differential  Characters  in    the   Bracliial   Plexus  of   other    than    Soliped 

Animals  ....•••• 

Comparison  of  the  Brachial  Plexus  of  Mm  with  that  of  Animals 
Sacro-lumbar  Plexus        .  .  .  .  • 

1.  Iliaco-muscular  Nerves  .  .  .  •  • 

2.  Crural,  or  Anterior  Femoral  Nerve  . 

3.  Obturator  Nerve  .  .  '  . 

4.  Small  Sciatic,  or  Anterior  and  Posterior  Gluteal  Nerves 

5.  Great  Sciatic,  or  Great  Femoro-popliteal  Nerve  . 
Collateral  Branches  ..... 
Terminal  Branches    ....•• 

Differential  Characters  in  the  Sacro-lumbar  Plexus  of  other  than  Soliped 
Animals  .....••• 

Comparison  of  the  Sacro-lumbar  Plexus  of  Man  with  that  of  Animals    . 


PAGK 

700 
703 
705 
706 
708 
709 
710 
721 
721 
727 
727 
728 
736 
738 
739 
744 
747 
748 
750 
751 
752 
753 

753 
754 
754 
755 
755 
756 
756 
756 
7o8 
758 
758 
758 
758 
758 
759 
760 
•  760 

763 
767 
770 
772 
772 
772 
773 
774 
775 
777 

777 
778 


TABLE  OF  CONTENTS. 

Chapter  III. — The  Great  Sympathetic  ...... 

1.  Cephalic  Portiim  of  the  Sympatlieiic  Chain  .... 

2.  Cervical  Portion  of  the  Synipathetic  Cliain  .  .  ,  . 

3.  Dorsal  Portion  of  the  Sympathetic  Chain       .... 

4.  Lumbar  Portion  of  the  Sympathetic  Chain  .... 

5.  Sacral  Portion  of  the  Sympathetic  Chain       .... 
Diflerential   Characters  in  the   Great  Sympathetic  of  other  than  Solii^ed 

Animals  ........ 

Comparison  of  the  Great  Sympathetic  of  Man  with  that  of  Animals 
Chapter  IV. — The  Nervous  System  of  Birds      ..... 


ZXXllI 

PAG  K 

.    781 

782 

.     783 

786 

.     788 

788 

789 
783 
790 


BOOK  VII. 

APPARATUS    OF    SENSE, 

Chapter  I. — Apparatus  of  Touch     ......  792 

Article  i. — Of  the  Skin  Proper             ...,.,  792 

Article  II. — The  Integumentary  Appendages          ....  797 

The  Hair              ........  797 

Horny  Productions    .......  799 

1.  The  Hoof  of  Solipeds             ......  800 

a.  Tlie  Parts  contained  in  the  Hoof         ....  800 

b.  Description  of  the  Hoof    ......  805 

2.  Tlie  Claws  of  Ruminants  and  Pachyderms           .             ,             .  812 

3.  The  Claws  of  Carnivora         ......  812 

4.  The  Frontal  Horns         .  .  .  .  .  .813 

5.  The  Chesnuts           .             .             .             .             .'            .             .  813 
(6.  Tlie  Ergots        .......  813) 

Chapter  II. — Apparatus  of  Taste           .             .             .             .   '          .             .  813 

Ditferential  Characters  in  the  Apparatus  of  Taste  of  other  than  Soliped 

Animals     ........  815 

Comparison  of  the  Apparatus  of  Taste  in  Man  with  that  of  Animals             .  815 

Chapter  III. — Apparatus  of  Smell  ......  815 

Chapter  IV. — Apparatus  of  Vision         ......  816 

Article  i. — Essential  Organ  of  Vision,  or  Globe  of  the  Eye             .             .  817 
Membranes  of  the  Eye     .             .             .             .             .             .             .817 

1.  The  Sclerotica   .......  817 

2.  The  Transparent  Cornea       ......  819 

3.  The  Choroid  Membrane               .....  820 

4.  The  Iris        ........  822 

5.  The  Eetina         .......  824 

The  Humours  of  the  Eye  .  .  .  .  .  .826 

1.  Crystalline  Lens             ......  826 

2.  Vitreous  Humour     .......  827 

3.  Aqueous  Humour           ......  827 

Article  11. — Accessory  Organs  of  the  Apparatus  of  Vision        .             .  828 

Orbital  Cavity            .......  828 

Motor  Muscles  of  the  Globe  of  the  Eye     .  .  .  .  .828 

Protective  Organs  of  the  Eye              .....  830 

1.  Eyelids         .  .  "  .  .  .  .  .  .830 

2.  Membrana  Nictitans       ......  833 

Lachrymal  Apparatus      .......  834 

Differential   Characters   in   the  Visual  Apparatus   of  other  than  Soliped 

Animals     .             .             .             .             .             .             .             .  835 

Comparison  of  the  Visual  Apparatus  of  Man  with  that  of  Animals  .            .  836 
3 


TABLE  OF  CONTENTS. 


CnAPTER  V.  —Apparatus  of  Hearing  ..... 

Article  i. — Internal  Ear,  or  Labyrinth  .  ,  .  ,  . 

Bony  Labyrinth  ....... 

1.  The  Vestibule  ....... 

2.  The  Semicircular  Canals     '        . 

3.  The  Cochlea  ....... 

The  Membranous  Labyrinth  ...... 

1.  The  Membranous  Vestibule  ..... 

2.  The  Membranous  Semicircular  Canals  .... 

3.  The  Membranous  Cochlea     ...... 

Liquids  of  the  Labyrinlh         ...... 

Distribution  and  Termination  of  the  Auditory  Nerve  in  the  Membranous 

Labyrinth     ........ 

Article  ii. — Middle  Ear,  or  Case  of  the  Tympanum 

1.  Membrane  of  the  Tympanum  ..... 

2.  Tlie  Promontory,  Fenestra  Ovalis,  Fenestra  Kotunda 

3.  The  Mastoid  Cells    ....... 

4.  Chain  of  Bones  of  the  Middle  Ear 

5.  Mucous  Membrane  of  the  Tympanic  Case 

6.  Eustachian  Tube 

7.  Guttural  Pouches     . 
Article  ni. — The  External  Ear     . 

External  Auditory  Canal 
The  Concha,  or  Pavilion 

1.  Cartilaginous  Basis  of  the  Concha    . 

2.  Muscles  of  the  External  Ear 

3.  Adipose  Cushion  of  the  External  Ear 

4.  Integuments  of  the  External  Ear 
Differential  Characters  in  the  Auditory  Apparatus  of  other  than  Soliped 

Animals  ......•• 

Comparison  of  the  Auditory  Apparatus  of  Man  with  that  of  Animals     . 


837 
837 
837 
837 
837 
837 
838 
838 
839 
839 
840 

840 
840 
841 
842 
842 
842 
844 
844 
844 
846 
846 
846 
846 
847 
850 
850 

850 
850 


BOOK  VIII. 


GENERATIVK    APPARATUS. 

Chapter  I. — Genital  Organs  of  the  Male 

The  Testicles,  or  Secretory  Organs  of  the  Semen  . 

1.  Description  of  the  Vaginal  Sheath 

2.  Description  of  the  Testicles  . 
Excretory  Apparatus  for  the  Semen   . 

1.  The  Epididymis  and  Deferent  Duct 

2.  The  VesiculiB  Seminales  and  Ejaculatory  Ducts 

3.  The  Urethra  .... 

4.  The  Glands  Annexed  to  the  Urethral  Canal 

5.  The  Corpus  Cavcrnosum 

6.  The  Penis  ..... 
Differential  Characters  in  the  Mule  Genital  Organs  of  other  than 

Mammals         ...... 

Comparison  of  the  Genital  Organs  of  Man  with  those  of  Animals 
Chapter  II. — Genital  Organs  of  the  Female       . 

1.  The  Ovaries  ....... 

2.  The  Uterine  Cornua,  Fallopian  Tubes,  or  Oviducts 

3.  The  Uterus  ...•••• 


Soliped 


851 
851 
852 
853 

858 
858 
860 
861 
864 
864 
865 

867 
871 
872 
872 
876 
877 


TABLE  OF  CONTENTS.  xxxv 

PAGE 

4.  TheYagina         .  .  .....  880 

5.  The  Vulva    ........  882 

6.  The  MammjB      ...  ....  884 

Differential  Characters  iu  the  Female  Genital  Organs  of  other  than  Soliped 

Mammals  ........  886 

Comparison  of  the  Genital  Organs  of  Woman  with  those  of  Domesticated 

Female  Animals  .......  888 

Chapter  III. — Generative  Apparatus  of  Binls  ....  889 

1.  Male  Genital  Organs       .......  889 

2.  Female  Genital  Organs  ......  889 


BOOK  IX. 

EMBRYOLOGT. 

Chapter  I. — The  Ovum  and  its  Modifications  after  Impregnation            .             .  890 

Article  I.— The  Ovum       .......  890 

Article  ii. — Modifications  in  the  Ovmn  until  the  Appearance  of  the  Emhryo  .  890 

Article  in. — Development  of  the  Blastodermic  Laminae      .             .             .  892 

External  Lamina     ........  893 

Middle  Lamina              .......  893 

Internal  Lamina      .......  894 

Chapter  II. — The  Foetal  Envelopes  of  Solipeds        .                          .             ,  895 

1.  The  Chorion        .              .                            .....  895 

2.  The  Amnion              .......  896 

3.  The  Allantois      ........  896 

4.  The  Umbilical  Vesicle            ......  899 

5.  The  Placenta      .  ,  .  .  .  .  .  .899 

6.  The  Umbilical  Cord  .......  900 

Differential  Characters  in  the  Annexes  of  the  Foetus  of  other  Domesticated 

Animals  than  Solipeds              ......  901 

Comparison  of  the  Annexes  of  the  Human  Foetus  with  those  of  the  Foetus  of 

Animals     .             .             .             .             .             .             .             .  904 

Chapter  III. — Development  of  the  Foetus           .....  905 

Article  i. — Formation  of  the  Embryo         .....  905 

Development  of  the  Chorda  Dorsalis  and  Vertebral  Laminse              .             .  905 

Development  of  the  Lateral  and  Cephalic  Laminae          .             .             •  905 

Article  ii.— Development  of  the  Various  Organs  of  the  Animal  Economy          .  907 

Development  of  the  Nervous  System      .....  907 

Development  of  the  Organs  of  Sense            .....  908 

Development  of  the  Locomotory  Apparatus        .  .  .  .911 

Development  of  the  Circulatory  Apparatus               ....  914 

Development  of  the  Eespiratory  Apparatus         ....  918 

Development  of  the  Digestive  Apparatus      .....  919 

Development  of  the  Genito-urinary  Apparatus  ....  922 

Chaktek  IV.— The  Ovum  of  Birds  .  .  .  .  .  -925 

Index    ......                         .            .  927 


TABLE   OF  ILLUSTRATIONS. 


FIGS. 

1.  Skeleton  of  the  Dog    .... 

2.  Skeleton  of  the  Pig  .  .  . 

3.  Skeleton  of  the  Horse 

4.  Skeleton  of  the  Cow  . 

5.  Skeleton  of  the  Sheep  .... 

6.  Vertical  section  of  bone 

7.  Minute  structure  of  bone 

8.  Lacunse,  or  osteoplasts  of  osseous  substance 

9.  Cartilage  at  the  seat  of  ossification 

10.  Elements  of  a  vertebra 

11.  Atlas,  inferior  surface 

12.  A  cervical  vertebra 

13.  The  axis  or  dentata,  lateral  view 

14.  Type  of  a  dorsal  vertebra,  the  fourth 

15.  Upper  surface  of  lumbar  vertebrae 

16.  Lumbar  vertebra,  front  view 

17.  Lateral  view  of  sacrum 

18.  Horse's  head,  front  view    . 

19.  Anterior  bones  of  the  head  of  a  foetus  at  birth 

20.  Posterior  bones  of  the  head  of  a  foetus  at  birth 

21.  Posterior  aspect  of  Horse's  skull 

22.  Antero-posterior  and  vertical  section  of  the  Horse's 

23.  Longitudinal  and  transverse  section  of  the  Horse's 

24.  Inferior  maxilla     .... 

25.  Hyoid  bone     .  .  .  .  • 

26.  Lateral  view  of  the  Horse's  skull 

27.  Ox's  head,  anterior  aspect        .  . 

28.  Kam's  head,  anterior  aspect 

29.  Ox's  head,  posterior  aspect 

30.  IMedian  and  vertical  section  of  the  Ox's  head 

31.  Head  of  the  Pig,  anterior  aspect 

32.  Head  of  the  Pig,  posterior  aspect  . 

33.  Head  of  Dog,  anterior  aspect  . 

34.  Dog"s  head,  posterior  aspect 

35.  Front  view  of  the  human  cranium 

36.  External  or  basilar  surface  of  human  skull 

37.  The  sternum    ..... 

38.  Typical  ribs  of  the  Horse  . 

39.  Thorax  of  Man,  anterior  face  . 

40.  Eight  scapula,  outer  surface 


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TABLE  OF  ILLUSTRATIONS, 
mas. 

41.  Antero-extcinal  view  of  right  humerus 

42.  Posterior  view  of  right  humerus     . 

43.  External  face  of  the  radius  aud  ulna     . 

44.  Right  fore-foot  of  a  Horse 

45.  Posterior  view  of  the  right  carpus 

46.  Front  view  of  right  carpus 

47.  Posterior  view  of  right  metacarpus 

48.  Lateral  view  of  the  digital  region :  outside  of  right  limb 

49.  Posterior  view  of  front  digital  region    . 

50.  Plantar  surface  of  third  phalanx    . 

51.  Navicular  bone  .... 

52.  Fore-arm  and  foot  of  the  Ox,  front  view 

53.  Fore-arm  and  foot  of  the  Dog,  anterior  face 

54.  Human  scapula,  external  aspect     . 

55.  Right  human  humerus,  anterior  surface 

56.  Human  arm  bones,  front  view 

57.  Palmar  surface  of  left  human  hand 

58.  The  Coxae,  seen  from  below 

59.  Pelvis,  front  view         .... 

60.  Pelvis,  lateral  view  .... 

61.  Left  femur,  anterior  view 

62.  Left  femur,  posterior  view 

63.  Section  of  left  femur,  showing  its  structure 

64.  Posterior  view  of  right  tibia 

65.  Left  hind  foot,  external  aspect 

66.  Left  hock,  front  view         .... 

67.  Left  hock,  internal  aspect 

68.  Posterior  aspect  of  left  metatarsus 

69.  Human  pelvis,  female 

70.  Right  human  femur,  anterior  aspect 

71.  Human  tibia  and  fibula  of  right  leg,  anterior  aspect 

72.  Dorsal  surface  of  left  human  foot  . 

73.  Skeleton  of  a  Fowl      .... 

74.  Cephalic  vertebrae  of  the  Dog        .... 

75.  Plans  of  the  diiferent  classes  of  articulations    .  Beaunis 

76.  Section  of  branchial  cartilage  of  Tadpole  . 

77.  Fibro-cartilage  ..... 

78.  White  or  non- elastic  fibrous  tissue 

79.  Yellow  or  elastic  fibrous  tissue 

80.  Intervertebral  articulations 

81.  Atlo-axoid  and  occipito-atloid  articulations 

82.  Temporo-maxillary  articulation 

83.  Articulations  of  the  ribs  with  the  vertebrae,  upper  plane 

84.  Articulations  of  the  ribs  with  the  vertebrae,  inferior  plane 

85.  Scapulo-humeral  and  humero-radial  articulations,  external  face 

86.  Carpal  articulations,  front  view      .... 

87.  Lateral  view  of  the  carpal  articulations 

88.  Section  of  inferior  row  of  carpal  bones,  and  metacarpal  and  sus- 

pensory ligament  ..... 

89.  Posterior  view  of  metacarpo-plialangeal   and  interphalangeal 

articulations  ..... 

90.  Sacro-iliac  and  coxo-femoral  articulations  . 

91.  Femoro-tibial  articulation        .  .  .  .  . 

92.  Ligaments  attaching  the  three  bones  of  the  leg 


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xxxviii  TABLE  OF  ILLUSTRATIONS. 

FIGS. 

93.  Tarsal  articulations,  front  view  .... 

94.  Articulations  of  the  tarsus,  lateral  view 

95.  Ultimate  fibril  of  muscle  .... 

96.  Striated  muscular  tissue  fibre         .... 

97.  Termination  of  nerves  in  muscular  fibre 

98.  Distribution  of  capillaries  in  muscle 

99.  Termination  of  nerves  in  au  elementary  muscular  fibre 

100.  Striated  fibre  of  muscle  during  contraction 

101.  Lateral  view  of  the  neck,  superficial  muscles    . 

1 02.  Superficial  muscles  of  the  neck  and  spinal  region  of  the  back 

and  loins  ...... 

103.  Lateral  view  of  the  neck,  middle  layer  of  muscles 

104.  Cervical  ligament  and  deep  muscles  of  the  neck    . 

105.  Muscles  of  the  spinal  region  of  the  neck,  back,  and  loins 

106.  Deep  ditto  ...... 

107.  Muscles  of  the  back  and  cervix  of  Man 

108.  Muscles  of  the  sublumbar,  patellar,  and  internal  crural  regions 

109.  Deep  muscles  of  the  sublumbar  region 

110.  Superficial  muscles  of  the  face  and  head    . 

111.  Hyoideal  and  pharyngeal  regions  .... 

112.  Superficial  muscles  of  the  Ox's  head 

113.  Muscles  of  the  human  head      .  .  .  .  . 

114.  Muscles  of  the  axillary  and  cervical  regions 

115.  Axillary  and  thoracic  muscles  .... 

116.  Muscles  of  the  inferior  abdominal  region  . 

117.  Muscles  of  the  anterior  aspect  of  the  body  of  Man 

118.  Diaphragm,  posterior  face  .  .  ^  . 

119.  External  muscles  of  the  anterior  limb 

120.  Muscles  of  anterior  aspect  of  Man's  upper  arm 

121.  Internal  aspect  of  left  anterior  limb      .  .  .  . 

122.  Deep  muscles  on  external  aspect  of  right  anterior  limb 

123.  Muscles  of  the  fore-arm  of  the  Ox         .  .  . 

124.  Tendinous  and  ligamentous  apparatus  in  the  digital  region  of 

the  Ox  . 

125.  Muscles  of  the  fore-arm  and  paw  of  the  Dog    . 

126.  Superficial  muscles  of  human  fore-arm 

127.  Deep  layer  of  superficial  muscles  of  human  fore-arm     . 

128.  Muscles  of  human  hand     ..... 

129.  Superficial  muscles  of  the  croup  and  thigh 

130.  Muscles  of  the  sublumbar,  patellar,  and  internal  crural  regions 

131.  Coccygeal  and   deep    muscles   surrounding  the  coxo-femoral 

articulation         ...... 

132.  Superficial  muscles  of  the  croup  and  thigh  in  the  Cow 
183.  Muscles  of  the  anterior  femoral  region  in  Man 

134.  Muscles  of  the  posterior  femoral  and  gluteal  region  in  ]\Iau 

135.  External  deep  muscles  of  right  posterior  limb 

136.  Flexor  muscle  of  metatarsus     ..... 

137.  Muscles  on  inner  aspect  of  left  posterior  limb 

138.  External  muscles  of  the  leg  of  the  Ox  . 

139.  Muscles  of  the  human  leg,  anterior  tibial  region 

140.  Superficial  posterior  muscles  of  the  human  leg 

141.  First  layer  of  plantar  muscles  of  human  foot 

142.  Third,  and  part  of  second  layer  of  plantar  muscles  of  human 

foot  ...... 


PAGE 

Chauveau   . 

169 

Chauveau   . 

171 

Bowman     . 

178 

Bowman 

178 

Klihne 

179 

Berres 

180 

Beale 

180 

Bowman 

181 

Original 

188 

Chauveau   . 

190 

Original     . 

192 

Chauveau   . 

194 

Chauveau   . 

204 

Chauveau   . 

207 

Wilson 

210 

Chauveau   . 

213 

Chauveau   . 

214 

Original 

218 

Original 

226 

Chauveau   . 

228 

Wilson 

231 

Chauveau    . 

232 

Original 

234 

Chauveau  . 

243- 

Wilson 

245 

Chauveau   . 

247 

Chauveau   . 

250 

Wilson 

255 

Original 

257 

Original 

260 

Chauveau   . 

270 

Chauveau   . 

271 

Chauveau    . 

273 

Wilson 

275- 

Wilson 

275 

Wilson 

279 

Original 

,     282 

Chauveau   . 

290 

Chauveau    . 

,     293 

Chauveau   . 

.     294 

Wilson 

.     296 

Wilson 

.     296 

Original 

,     299 

Chauveau 

.     300 

Original 

.     303 

Chauveau 

.     307 

Wilson 

.     310 

Wilson 

.     310 

Wilson 

.     312 

Wilson 


312 


TABLE  OF  ILLUSTRATIONS. 

FIGS. 

143.  Squamous  epitlielium  from  the  mouth 

144.  Columnar  epithelimn   ..... 

145.  Columnar  ciliated  epithelium 
146-  Conical  villi  on  mucous  membrane  of  small  intestine     . 

147.  Fusiform  cells  of  smooth  muscular  fibre 

148.  Hard  and  soft  palate    ..... 

149.  Muscles  of  the  tongue,  soft  palate,  and  pharynx 

150.  Lobe  of  racemose  gland  from  the  floor  of  the  mouth 

151.  Follicular  gland     ..... 

152.  Median  longitudinal  section  of  the  head  and  upper  part  of  neck 

153.  Section  through  the  fang  of  a  molar  tooth 

154.  Transverse  section  of  enamel 

155.  Magnified  section  of  a  canine  tooth 

156.  Theoretical  section  of  dental  sac  of  permanent  incisor 

157.  Section  of  dentine  and  pulp  of  an  incisor  tooth 

158.  Dentition  of  inferior  jaw  of  Horse  . 

159.  Incisor  teeth  of  Horse,  details  of  structure 

160.  Profile  of  upper  teeth  of  the  Horse 

161.  Transverse  section  of  Horse's  upper  molar 

162.  Tlie  teeth  of  the  Ox  . 

163.  Ox's  incisor  tooth         ..... 

164.  Incisor  teeth  of  a  Sheep  two  years  old 

165.  Teeth  of  the  Pig  ....  . 

166.  General  and  lateral  view  of  the  Dog's  teeth 

167.  Anterior  view  of  the  incisors  and  canine  teeth  of  Dog  . 

168.  Section  of  the  human  face  .... 

169.  Lobule  of  parotid  gland  .... 

170.  Capillary  network  of  follicles  of  parotid  gland 

171.  Termination  of  the  nerves  in  the  salivary  glands 

172.  Inferior  aspect  of  head  and  neck     . 

173.  Maxillary  and  sublingual  glands 

174.  Pharyngeal  and  laryngeal  region    . 

175.  Median  longitudinal  section  of  head  and  upper  part  of  neck 

176.  Muscles  of  the  pharyngeal  and  hyoideal  regions     . 

177.  Human  pharynx  ..... 

178.  Transverse  vertical  section  of  head  and  neck 

179.  Pectoral  cavity  and  mediastinum 

180.  Theoretic;d  transverse  section  of  abdominal  cavity 

181.  Theoretical,  longitudinal,    and   median  section  of  abdominal 

cavity           ......  .     Chauveau  . 

182.  The  abdominal  cavity,  with  the  stomach  and  other  organs.             Original  . 

183.  Stomach  of  the  Horse  .....  .     Chauveau  . 

184.  Interior  of  the  Horse's  stomach      ....             Chauveau  . 

185.  Musculiir  fibres  of  stomach,  external  and  middle  layers  .     Chauveau  . 

186.  Deep  and  middle  muscular  fibres  of  stomach           .             .             Chauveau  . 

187.  Peptic  gastric  gland    .....  .     KoUiker  . 

188.  Portion  of  a  peptic  ctecum               ....             KoUiker  . 

189.  ]Mucous  gastric  gland  .....  .     KoUiker 

190.  Capillaries  of  mucous  membrane  of  stomach            .             .             Carpenter  . 

191.  Stomach  of  the  Dog     .....  .     CJiauveau  . 

192.  Stomach  of  the  Ox               .              .              .              .              .             Chauveau  . 

193.  Interior  of  the  stomach  of  Euminants  ....     Cliauveau  . 

194.  Section  of  the  wall  of  the  omasum  of  Sheep            .             .             Chauveau  . 

195.  Section  of  a  leaf  of  the  omasum  .  .  .  After  Chauveau 


Wilson 
KoUiker 
Carpenter 
Wilson 
Botcman 
Chauveau 
Chauveau 
KoUiker 
KoUiker 
Original 
Carpenter 
Carpenter 
Wilson 
Chauveau 
Carpenter 
Chauveau 
CJiauveau 
Chauveau 
Chauveau 
Chauveau 
Chauveau 
Chauveau 
Chauveau 
Cliauveau 
Chauveau 
Quain 
Wagner 
Berres 
Pfliiger 
Original 
Chauveau 
Original 
Original 
Original 
Wilson 
Original 
Chauveau 
Chauveau 


PAGE 

327 
327 
327 
328 
328 
333 
338 
339 
339 
341 
345 
346 
347 
348 
349 
350 
351 
353 
354 
357 
358 
359 
360 
361 
361 
362 
365 
365 
366 
367 
368 
372 
373 
375 
377 
378 
379 
382 

383 
386 
387 
388 
390 
390 
391 
391 
392 
392 
393 
394 
395 
398 
399 


xl  TABLE  OF  ILLUSTRATIONS. 

FIG& 

196.  Longitudinal  section  of  a  large  p  ipilla  from  the  omasum 

197.  Villi  of  human  and  Sheep's  intestine    . 

198.  Portion  of  Brunner's  gland 

199.  Section  of  mucous  meujbrane  of  small  intestine 

200.  Section  of  mucous  membrane  of  large  intestine 

201.  Injected  villi  of  intestine  .... 

202.  Blood-vessels  in  Peyerian  glandulaj 

203.  Diagram  of  origin  of  lacteals  in  villi    . 

204.  General  view  of  the  intestines  of  tlie  Horse,  right  side 

205.  General  view  of  the  Horse's  intestines,  inferior  aspect  . 

206.  The  colon  of  tiie  Horse 
2U7.  PLin  of  the  colon 

208.  General  view  of  the  intestines  of  the  Ox 

209.  Intestines  of  the  Dog  . 

210.  Human  intestines  . 
'.^11.  Abdominiil  cavity,  with  the  liver  and  other  organs 

212.  Port  on  of  a  hepatic  column,  with  secreting  cells 

213.  Biliary  capillaries  and  ducts    . 

214.  Bloud-vessels  in  lobules  of  liver 

215.  Section  of  lobules  of  liver,  with  intralobular  veins 

216.  Excretory  aj^paratus  of  the  Horse's  liver    . 

217.  Malpighian  corpuscles  attached  to  splenic  artery 

218.  Splenic  corpuscle  from  the  spleen  of  Ox     . 

219.  Liver  of  the  Dog,  with  its  excretory  apparatus 

220.  Under  surface  of  the  human  liver  . 

221.  General  view  of  the  digestive  apparatus  of  a  fowl 

222.  Cartilages  of  the  nose 

223.  Transverse  section  of  the  head  of  Horse 

224.  Longitudinal  section  of  the  head,  and  upper  part  of  neck 

225.  Cells  of  the  olfactory  mucous  membrane 

226.  Fibres  of  olfactory  nerve    . 

227.  Superior  face  of  larynx 

228.  Inferior  face  of  larynx 

229.  Postero-lateral  view  of  larynx  . 

230.  The  respiratory  organs,  inferior  aspect 

231.  Ciliated  epithelium  from  the  trachea  . 

232.  Bronchial  tube,  with  its  bronebules 

233.  Mucous  membrane  of  a  bronchial  tube 

234.  Tiie  pectoral  cavity  and  mediastinum 

235.  Theoretical  section  of  thoracic  cavity,  behind  the  heart 

236.  Theoretical  section  of  thoracic  cavity,  at  root  of  lungs 

237.  Theoretical  section  of  thoracic  cavity,  in  front  of  right 

238.  Plan  cf  a  pulmon;iry  lobule      .... 

239.  Air-cells  of  lung    ..... 

240.  Capillaries  ami  air-cells  of  lung 

241.  Lung  of  the  Sheep,  inferior  view    . 

242.  Human  lungs  and  heart  .... 

243.  Gland  vesicles  of  thyroid 

244.  Portion  of  thymus  of  calf  .... 

245.  Course  and  termination  of  ducts  in  thymus  gland  of  calf 

246.  General  view  of  the  air-sacs  in  the  duck 

247.  General  view  of  the  genito-urinary  ajiparatus  in  the  male 

248.  Horizontal  longitudinal  section  of  the  Horse's  kidney  . 

249.  Section  of  the  cortical  substance  of  the  kidney 


Ckauveau  . 

Teichmann . 

Thomson 

Teichmann. 

Teichmann . 
.     KolUker 

Kolliker 

Funlie 
After  Chauveau 

Chauveau  . 

Original 

Chauveau  . 

Chauveau,  . 

Chauveau   . 

Wilson 

Original 

Leidij 
Irminger  and  Freij 

Kiernan 
.     Kiernan 

Chauveau  . 
.     Kolliher 

Kolliker 

Chauveau  . 

Wilson 

Chauveau  . 

Chauveau  . 

Chauveau   . 

Original     . 
Clarke  and  Schultze 

Ecker 
After  Chauveau 
After  Chauveau 

Original 

Original 

Kolliker 

Heale 

Heale 

Chauveau  . 

Chauveau  . 

Chauveau   . 

Chauveau  . 

TT  fleers 

Kolliker 

Carpenter   . 

Chauveau   . 

Wilsoji 

Kolliker 

Kiilliker      . 

Wilson 

Chauveau   . 

Chauveau  . 

Chauveau  . 

Ecktr 


ventricle 


PAOE 

399 
403 
403 
404 
405 
405 
406 
406 
408 
409 
410 
411 
415 
416 
417 
421 
423 
423 
424 
424 
425 
430 
430 
433 
434 
436 
440 
442 
443 
445 
446 
4.i2 
452 
454 
458 
459 
460 
461 
463 
465 
465 
465 
468 
469 
469 
471 
471 
472 
474 
474 
480 
485 
487 
483 


TABLE  OF  ILLUSTRATIONS. 

FIGS. 

250.  Course  of  the  uriniferous  tubuli 

251.  Diagram  of  the  circulation  in  the  kidney   . 

252.  Transverse  horizontul  section  of  kidney 

253.  The  kidneys  and  bhidder  in  the  foetus  of  Solipeds 

254.  Eight  kidnt-y  of  Ox,  upper  and  external  face    . 

255.  Left  kidney  of  Ox,  internal  and  inferior  face 

256.  The  calices  in  left  kidney  of  Ox 

257.  Theoretical  plan  of  the  circulatory  system  . 

258.  The  heart  and  principal  vessels,  left  face 

259.  The  heart  and  principal  vessels,  right  face 

260.  Right  side  of  the  heart  laid  open 

261.  Section  of  the  heart  at  the  level  of  the  valves 

262.  Left  cavities  of  the  heart  laid  open 

263.  Anastomosing  muscular  fibres  of  heart 

264.  Epithelium  of  the  endocardium 

265.  Human  lungs  and  heart,  front  view 

266.  Web  of  Frog's  foot,  showing  blood-vessels  and  their  anastomoses 

267.  Epithelial  cells  of  blood-vessels 

268.  Fenestrated  membrane  from  the  carotid  artery  of  the  Horse 

269.  Coarse  elastic  tissue  from  pulmonary  artery  of  the  Horse 

270.  Transition  of  a  minute  artery  of  the  brain  into  capillary  vessels 

271.  Distribution  of  the  great  mesenteric  arteiy 

272.  Distribution  of  the  small  mesenteric  artery 

273.  Arteries  of  the  stomach  in  Ruminants  . 

274.  Upper  and  general  view  of  the  genito-urinary  apparatus  and 

arteries  in  the  male         ..... 

275.  Lateral  view  of  the  gc-nito-urinary  organs  in  the  male 

276.  Abdominal  aorta,  with  its  branches,  in  Man 

277.  Tiie  external  and  internal  iliac  arteries  in  the  Mare 

278.  Principal  arteries  and  veins  of  the  posterior  foot     . 

279.  Anterior  aspect  of  liuman  leg  and  foot 

280.  Posterior  aspect  of  human  leg 

281.  Arteries  of  sole  of  human  foot  . 

282.  Distribution  of  the  anterior  aorta  . 

283.  Arteries  of  the  fore-foot,  seen  from  behind 

284.  Arteries  of  the  human  fore-arm  and  hand  . 

285.  Arteries  of  the  brain    .... 

286.  Arteries  of  the  head  .... 

287.  Re'seau  admirable  of  tlie  Sheep,  seen  in  profile  . 

288.  Re'seau  admirable  of  the  Ox,  posterior  face 

289.  Arteries  of  the  face  and  head  of  Man    . 

290.  Roots  of  the  superior  jugular  vein,  with  its  collateral  atfiuents 

291.  Section  of  the  cianial  cavity  and  spinal  canal 

292.  Veins  of  the  foot  .... 

293.  General  view  of  the  veins  in  the  Horse 

294.  The  vena  ports  and  its  roots    . 

295.  Section  of  a  lymphatic  rete  mirabile 

296.  Section  of  lymphatic  gland 

297.  Section  of  simple  lymphatic  gland .... 

298.  Section  of  the  medullary  substance  of  lympnatic  gland  of  Ox 

299.  Ordinary  disposition  of  the  thoracic  duct    . 

300.  Double  variety  of  the  tlioracic  duct 

301.  Triple  variety  of  the  tl.oracic  duct 

302.  Lymphatic  system  of  the  Horse 


Eertz 
Bowman 
Original 
Chauveau  . 
Cfuiuveau  . 
Chauveau   . 
Chauveau   . 
Colin 

Chauveau   . 
Chauveau   . 
Wihon 
Stbso7i 
Wilson 
KuUiker 
Kvlliker 
Wilson 
Wagner 
K  oil!  her 
Kolliher 
KulUher 
Kolliker 
Chauveau   . 
Chauveau   . 
Chauveau  . 

Chauveau   . 
Chauveau   . 
Wilson 
Chauveau  . 
Chauveau  . 
Wilson 
Wilson 
W^ilso7i 
Chauveau   . 
Chauveau   . 
Wilson 
Chauveau   . 
Chauveau   . 
Cha uveau  . 
Chauveau  . 
Heath 
Chauveau   . 
Chauveau   . 
After  Bouley 
Chauveau  . 
Chauveau   . 
Teichmann . 
Kolliker 
Teichmann . 
Kolliker      . 
Colin 
Colin 
Colin 
Colin 


xli 

PAGE 

488 
489 
489 
492 
496 
496 
496 
498 
501 
502 
504 
505 
507 
509 
511 
514 
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519 
519 
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533 
536 

539 
542 
544 
546 
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508 
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580 
583 
593 
594 
595 
604 
607 
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636 
636 
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xlii 

FIG;!. 

303. 
304. 
305. 
306. 
307. 
308. 
309. 
310. 
311. 
312. 
313. 
314. 
315. 
316. 
317. 
318. 
319. 

320. 

321. 
322. 
323. 
324. 
325. 
326. 
327. 
328. 
329. 
330. 
331. 
332. 
333. 
334. 
335. 
336. 
337. 
338. 
339. 
340. 
341. 
342. 
343. 
344. 
■345. 
346, 
347. 
348. 
349. 
350. 
351. 
352. 
353. 
354. 


TABLE  OF  ILLUSTRATIONS. 

FAGE 

Great  lymphatic  vein  and  entrance  of  the  thoracic  duct      .  Colin          .     645 

Great  lymphatic  duct,  another  variety              .             .              .  Colin          .     645 

Thoracic  duct  in  the  Ox    .             .             .             .             •  Colin          .     645 

A  variety  of  the  thoracic  duct  in  the  Ox           .             .              .  Colin          .     646 

Anotlier  variety  of  the  thoracic  duct           .              .              .  Colin           .     646 

A  fourth  variety  of  the  thoracic  duct   ....  Colin           .     646 

Tljoracic  duct  of  small  Ruminants.              .              .              .  Colin           .     647 

Diagram  of  structure  of  nerve-fibre       ....  Carpenter  .     652 

Multipolar,  or  stellate  nerve-cell    ....  Ecl-er         .     653 

Ganglion  from  heart  of  Frog  .....  Eclcer          .     654 

Bipolar  ganglionic  cells  and  nerve-fibres    .             .             .  Ecker         .     654 

Stellate  nerve-cell         .....               .  Beale          .     654 

Structure  of  ganglionic  cells  ....  Beale  and  Arnold    654 

General  view  of  the  spinal  cord             ....  Colin           .     667 

Segment  of  the  spinal  cord  at  the  cervical  bulb     ,              .  Colin          .     667 

Section  of  the  spinal  cord  of  the  Horse  at  the  lumbar  region      .  Chauveau  .     669 
Transverse  section  of  spinal  cord  of  Man  at  the  middle  of  the 

lumbar  region           .              .              .              .              .               .  I.  L.  Clarke     670 

Longitudinal  section  through  cervical  bulb  of  spinal  cord  of  the 

Cat         .             .             .             •             •             •             ■  !•  L.  Clarke 

General  view  of  the  brain,  upper  surface          .              .               .  Chauveau   . 

General  view  of  the  brain,  lower  surface     .              .              .  Original     . 

Superior  view  of  the  encephalic  isthmus            .             .              .  Chauveau  . 

Lateral  view  of  the  isthmus            ....  Chauveau  . 

Transverse  section  of  the  encephalon    ....  Cliauveau  . 

Dissection  of  the  medulla  oblongata  .  .  Solly  and  Carpenter 

Median  and  vertical  section  of  the  encephalon  .              .               .  Cliauveau  . 

Section  of  the  cortical  substance  of  the  cerebellum  .             .  Kolliker 

Antero-posterior  and  vertical  section  of  the  encephalon              .  Chauveau  . 

Corpus  callosum    ......  Chauveau  . 

Anterior  portion  of  the  lateral  ventricles           .              .               .  Chauveau  . 

Corticle  substance  of  the  cerebral  hemispheres        .              .  Kolliker 


Base  of  the  human  brain 

Muscular  fibres,  with  termination  of  motor  nerve   . 

Nerves  of  the  eye         ..... 

General  view  of  the  superior  and  inferior  maxillary  nerves 

Section  through  the  summit  of  the  medulla  oblongata  . 

Origin  of  the  nerves  arising  from  the  medulla  oblongata    . 

Pneuniogastric  nerve,  with  its  branches  in  the  neck 

Origin  and  distribution  of  the  eighth  pair  of  nerves  in  Man 

Distribution  of  the  nerves  in  the  larynx  of  the  Horse   . 

Deep  nerves  of  the  head    ..... 

Nerves  of  the  guttural  region  in  the  Ox 

Nerves  of  tlie  face  and  scalp  of  Man 

Distribution  of  eighth  pair  of  nerves  on  left  side 

Ganglion  of  a  spinal  nerve  from  the  spinal  region 

Nerves  of  the  brachial  plexus  . 

External  nerves  of  anterior  limb     . 

Nerves  of  the  digit  of  Horse     . 

Nerves  of  the  digital  region  of  Ruminants  . 

Nerves  of  the  palmar  face  of  Dog's  foot 

Nerves  of  the  palmar  face  of  Cat's  foot 

Nerves  of  the  axilla  of  Man 

Nerves  of  the  front  of  fore-arm  and  hand  of  Man 


Hirschfeld  and  Leveill^ 

Cohnheim  . 

Chauveau  . 

Chauveau  . 

Carpenter  . 

Toussaint    . 

Toussaint   . 

Wilson 

Toussaint    . 

Chauveau   . 

Toussaint  . 
Hirschfeld  and  Leveilld" 
Hirschfeld  and  Leveille' 

Kolliker 

Chauveau   . 

Chauveau  . 
.     Bouley 

Chauveau  . 

Chauveau  . 

Chauveau  . 
Hirschfeld  and  Leveill€ 
Hirschfeld  and  Leveille 


671 
673 
676 
678 
680 
682 
684 
687 
689 
690 
693 
696 
697 
699 
702 
708 
714 
721 
730 
731 
732 
734 
738 
740 
745 
746 
748 
757 
759 
762 
764 
766 
767 
768 
7G9 


FIGS. 

355. 
856. 
357. 
35S. 
359. 
360. 
361. 
362. 
363. 
364. 
365. 
366. 
367. 
368. 
369. 
370. 
371. 
372. 
373. 
374. 
375. 
376. 
377. 
37S. 
379. 

380. 
381. 
382. 
383. 
384. 

385. 
386. 
387. 
388. 
389. 
390. 
391. 
392. 
393. 
394. 
395. 
396. 
397. 
398. 
399. 
400. 
401. 
402. 
403. 
404. 
405. 
406. 


TABLE  OF  ILLUSTRATIONS. 

Lumbo-sacral  plexus  and  internal  nerves  of  posterior  limb         .     Chauveau  . 
Posterior  portion  of  the  lumbo-sacral  plexus  .  .  Chauveau   . 

External  nerves  of  posterior  limb  ....     Chauveau  . 

Lumbar  plexus  of  Man      ....       Hirschfdd  and  LeveilU 
Nerves  at  the  posterior  aspect  of  human  leg      .  Hirschfeld  and  Leveille' 

Nerves  at  the  front  aspect  of  human  leg     .  .      Hirschfeld  and  Leveille 


Sympathetic  ganglion  from  a  Puppy    . 

Sympathetic  system  of  the  Horse  . 

Section  of  Horse's  skin  .... 

Capillary  loops  in  cutaneous  papillae 

Tactile  papillse  from  the  skin  . 

Interungulate  glund  of  Sheep 

Branches  of  cutaneous  nerves  in  skin  . 

Sudoriparous  gland 

Oblique  section  of  epidermis    .... 

Longitudinal  median  section  of  Horse's  foot 

Horizontal  section  of  Horse's  foot 

Lower  surface  of  the  Horse's  foot   . 

Lateral  view  of  the  Horse's  foot 

Hoof  removed  from  the  foot 

Hoof  with  outer  portion  of  v\  all  removed 

Plautar  surface  of  hoof      .... 

Horn-cells  from  the  sole  of  hoof 

Constituent  elements  of  the  wall    .... 

Horizontal  section  of  the  junction  of  the  wall  with  the  sole  of 
hoof  ...... 

Horizontal  section  of  wall,  and  horny  and  vascular  laminae 

Fibres  of  ultimate  ramifications  of  olfactory  nerves 

Cells  of  olfactory  mucous  membrane 

Theoretical  section  of  the  Horse's  eye  . 

Anterior  segment  of  a  transverse  section  of  the  globe  of  the  eye 
(human)  ..... 

Cells  from  pigmentum  nigrum 

The  eye  inhuman)  with  the  sclerotic  coat  removed  . 

Sluscular  structure  of  the  iris  . 

Vertical  section  of  retina    .... 

Diagram  of  the  structure  of  the  retina 

Capillaries  in  the  vascular  layer  of  the  retina 

Muscles  of  the  eye-ball,  viewed  from  above 

Section  of  lamina  spii-alis  of  the  cochlea    . 

Section  of  the  cochlea  parallel  to  its  axis 

Right  tympanic  cavity  of  Horse's  ear 

Bones  of  the  middle  ear  of  the  Horse  . 

Muscles  of  the  ear  .... 

Human  testis,  injected  with  mercury    . 

Vertical  section  of  the  Horse's  testis 

Internal  genito-urinary  organs  of  the  foetus  of  a  Mare 

Spermatozoa  of  various  animals 

Diagram  of  the  testicle 

Superior  view  of  the  genito-urinary  organs 

Longitudinal  section  of  the  free  extremity  of  the  Horse's  penis 

Sections  of  the  urethra  of  the  Ox  at  different  points 

Penis  and  muscles  of  the  sheath  of  the  Bull 

Section  of  human  pelvis    .... 


Kolliker 

Chauveau 

Chauveau 

Berres 

Ecker 

Owen 

Echer 

Wagner 

Carpenter 

Original 

Original 

Original 

Original 

Leisering 

Leisering 

Leisering 

Leisering 

Leisering 


Leisering    . 

Leisering    . 

.     Ecker 

Clarke  and  Shultzc 

Chauveau  . 


Wilion 

Carpenter 

Holden 

Kolliker 

Muller 

Krause 

Btrres 

Original 

Carpenter 

Breschet 

Chauveau 

Lavocat 

Original 

Lauth 

Chauveau 

Chauveau 

Carpenter 

Holden 

Chauveau 

Chauveau 

Chauveau 

Chauveau 

Gray 


xliii 

PAGE 

771 
773 

776 
779 

780 
780 
782 
784 
793 
793 
794 
794 
795 
795 
796 
800 
801 
802 
8' '3 
806 
806 
807 
809 
810 

811 
811 
816 
816 
818 

821 

822 

823 

823 

825 

826 

826 

829 

838 

838 

841 

843 

848 

854- 

855 

8.57 

858 

859 

860 

866 

868 

869 

871 


sliv  TABLE  OF  ILLUSTRATIONS. 

FIC-S. 

407.  Ovarium  of  the  Kabbit  .... 

408.  Constituent  parts  of  mammalian  ovum,  entire 

409.  Constituent  parts  of  mammulian  ovum,  ruptured 

410.  Formation  of  the  corpus  luteum     .... 

411.  Generative  organs  of  the  Mare,  isolated 

412.  Generative  organs  of  the  Mare,  in  situ 

41  o.  Termination  of  milk-duct  in  cluster  of  follicles 

414.  Ultimate  follicles  of  mammary  gland,  with  secreting  cells  . 

415.  Microscopic  appearance  of  milk 
41G.  Human  uterus,  with  its  appendages 

417.  First  stages  in  segmentation  of  mammalian  ovum 

418.  Later  stages  in  segmentation  .... 

419.  Section  through  embryo  of  the  Chick,  first  day  of  incubation 

420.  Plan  of  early  uterine  ovum  .... 

421.  Diagram  of  ovum  at  formation  of  the  amnion  . 

422.  Exterior  of  the  chorial  sac,  Mare    .... 

423.  Fecundated  egg,  showing  formation  of  amnion  and  allantois 

424.  Fecundated  egg,  with  amnion  nearly  completed 

425.  Foetus  of  the  Mare,  with  its  envelopes. 

426.  Portion  of  ultimate  ramifications  of  umbilical  vessels 

427.  Portion  of  one  of  the  fostal  villi 

428.  Equine  foetus,  opened  on  left  side  to  show  innbilical  vessels 

429.  Blood-vessels  in  liver  of  an  equine  foetus  at  mid-terra    . 

430.  Liver  of  a  Lamb  at  birth   ..... 

431.  Diagram  of  an  early  human  ovum 

432.  Diagram  of  a  human  ovum  in  second  month 

433.  Early  stages  in  the  development  of  a  Fowl 

434.  Transverse  section  of  embryo  of  Chick  on  third  day 

435.  Plan  of  development  of  eye      .... 

436.  Origin  of  encephalic  centres  in  human  embryo  of  sixth  week 

437.  Plan  of  chorda  dorsalis  at  period  of  formation  of  embryo     . 

438.  Plan  of  vertebra  at  an  early  period  of  development 

439.  Head  of  a  foetal  Lamb,  showing  Meckel's  cartilage 

440.  Plan  of  first  system  of  vessels,  embryo  . 

441.  Embryonic  heart  at  an  early  period,  anterior  view 

442.  Ditto,  seen  from  behind  .... 

443.  Heart  of  an  equine  foetus  ..... 

444.  Plan  of  the  aorta  and  its  arches  at  an  early  period 

445.  Plan  of  the  circulation  in  the  human  embryo,  side  view 

446.  First  appearance  of  the  lungs  .... 

447.  Embryo  of  Dug  at  twenty-five  days 

448.  Origin  of  liver  from  intestinal  Avail  of  embryo  Chick     . 

449.  Urinary  and  genital  apparatus  in  embryo  Chick     . 

450.  Section  of  Fowl's  egg  ..... 


Pouchet 
Coste 
Coste 
Fouchet 
Chauveau   . 
Chauveau   . 
Sir  A.  Cooper 
Leber  t 
FunJce 
Wilson 
Coste 
Coste 
Kolliker 
Warjuer 
Wagner 
Chauveau   . 
Dalton 
Daltou 
Cliaui-eau   . 
Carpenter  . 
Ecker 
Chauveau   . 
Colin 
Colin 
Wagner 
Wagner 
Huxley 
Kolliker 
Kolliker 
Wagner 
Kolliker 
Kolliker 
Huxltij 
Kolliker 
Kolliker 
Kolliker 
Chauveau  . 
Kolliker 
Coste 
Wagner 
Bischoff 
Miiller 
Mailer 
Alien  Thomson 


PAGE 

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922 
922 
925 


THE    COMPAEATIVE    ANATOMY 


OF   THE 


DOMESTICATED    ANIMALS. 


GENEEAL  COXSIDERATIONS. 

DEEmiTIOX    AND    DIVISIONS    OF    AXATOMT. 

Anatomy  is  the  science  of  organisation ;  it  studies  the  structure  of 
animated  beings  when  these  have  been  deprived  of  life.  It  comprises  two 
grand  divisions :  physiological  anatomy,  which  describes  healthy  organs,  and 
pathological  anatomy,  whose  object  is  the  description  of  diseased  organs. 

Physiological  anatomy,  in  its  turn,  embraces  : — 

1.  General  anatomy,  which  is  occupied  with  the  analogous  matters  or 
tissues  of  the  animal  body,  with  regard  to  their  texture,  and  their  physical, 
chemical,  and  physiological  properties,  irrespective  of  the  organs  in  which 
these  tissues  exist.  The  particular  study  of  the  anatomical  elements 
entering  into  the  composition  of  the  tissues  is  named  histology. 

2.  Descriptive  anatomy,  which  studies  the  situation,  form,  and  relation 
of  organs,  as  well  as  the  relative  arrangement  of  the  various  tissues 
composing  them,  with  the  exception  of  the  structure  and  properties  of  these 
tissues. 

If  this  study  be  devoted  to  a  single  species,  it  is  designated  special 
anatomy.  Example  :  human  anatomy,  or  anthropotomy  ;  the  anatomy  of  the 
Horse,  or  hippotomy. 

When  descriptive  anatomy  embraces  the  study  of  the  organisation  of  the 
entire  animal  kingdom,  and  examines  the  differences  which  characterise  the 
same  organ  or  the  same  series  of  organs  in  each  class,  family,  genus,  or 
species,  it  is  named  comparative  anatomy.  Restricted  to  the  domesticated 
animals,  this  study  constitutes  veterinary  anatomy. 

Philosophical  or  transcendental  anatomy  differs  from  comparative  anatomy, 
inasmuch  as  it  indicates  the  analogies  of  organs  or  apparatus,  in  order  to 
exhibit  the  simplicity  of  Nature's  plan  in  the  general  laws  of  organisation. 

Finally,  if  descriptive  anatomy  is  limited  to  denoting  the  relations 
existing  between  the  various  organs  of  a  region,  particularly  with  a  view  to 
the  performance  of  operations  and  the  diagnosis  of  external  diseases,  it  takes 
the  names  of  topographical,  regional,  or  surgical  anatomy. 


GENERAL  CONSIDERATIONS. 


ENUMERATION   AND   CLASSIFICATION    OF   THE    SPECIES    OF   DOMESTICATED 

ANIMALS. 

The  object  of  tliis  book  is  the  study  of  veterinary  anatomy.  The 
animals  of  which  it  treats  belong  to  the  mammiferous  class  and  to  that  of 
birds. 

The  domesticated  mammals  of  our  regions  have  their  representatives  in 
a  large  number  of  orders.     Thus,  we  find  among  them  : — 

1.  Of  the  carnivora,  the  Dog  and  Cat; 

2.  A  rodent,  the  Bahhit ; 

3.  A  pachyderm,  the  Pig  ; 

4.  Of   solipeds,  the  Horse  and  Ass ;  the  produce  of  the  male  ass  with 

the  mare,  i.e.,  the  Mule,  and  that  of  the  horse  with  the  female  ass, 
known  by  the  name  of  Hinny ; 

5.  Of  ruminants,  the  Ox,  Sheej>,  and  Goat. 

With  regard  to  poultry,  they  range  themselves  :— 

1.  In  the  gallinaceous  order,  the  genera  to  which  the  common  fowl, 

guinea  fowl,  turhey,  and  pigeon  belong  ; 

2.  In  the  order  of  palmipeds,  the  geese  and  ducJcs. 

Girard  has  proposed  a  special  classification  for  the  domesticated  mammals, 
based  upon  the  number  of  digits  terminating  each  of  their  limbs,  and  has 
defined  four  categories :  the  first  comprises  the  horse,  ass,  mule,  and  hinny, 
which  take  the  name  of  monodactyles,  because  their  digital  region  is  composed 
of  a  single  digit ;  in  the  second,  under  the  denomination  of  didactyles  or 
bisulcate  animals,  those  with  two  digits,  such  as  the  ox,  sheep,  and  goat ;  in 
the  third,  or  regular  tetradactyles,  is  found  rauged  the  pig,  each  of  whose 
limbs  shows  four  digits ;  lastly,  the  dog  and  cat,  which  most  frequently 
have  four  digits  on  the  posterior  members  and  five  on  the  anterior  ones,  and 
form  the  class  of  irregular  tetradactyles. 

This  nomenclature  will  not  be  followed  here,  as  it  is  opposed  to  the  general 
laws  of  organisation  ;  philosophical  anatomy  has,  in  fact,  demonstrated  that 
there  are  really  no  veritable  monodactyles,  didactyles,  etc.,  all  are  materially 
or  virtually  pentadactyles.  It  is  therefore  considered  better  to  keep  to  the 
classification  established  by  zoologists,  because  it  prevents  confusion  in 
scientific  language,  which  should  always  be  the  same  for  everyone  engaged 
in  the  study  of  anatomy. 

The  regimen  and  habits  of  the  domesticated  animals  bring  about  differ- 
ences in  their  organisation  which  appear  very  great  at  first  sight,  though  in 
reality  they  are  not  so  profound  as  they  seem. 

In  order  to  study  the  descriptive  anatomy  of  all  these  animals,  we  will 
not  pass  them  in  review,  one  after  another,  giving  for  each  the  description 
of  every  organ ;  but  shall  take  a  type,  which  will  most  frequently  be 
the  Horse,  and  briefly  compare  all  the  others  with  it.  In  the  majority  of 
cases,  we  will  describe,  without  leaving  the  Horse,  all  the  organs  of  an 
apparatus  ;  afterwards  the  same  organs  in  the  other  species  will  be  studied 
in  the  same  order.  In  this  comparison,  the  animals  will  be  generally  classed 
according  to  their  domestic  value ;  though  exceptions  will  be  made  to  the 
rule  which  has  been  instituted  by  our  predecessors,  whenever  any  advantage 
in  point  of  concision  or  perspicuity  is  likely  to  be  obtained. 


GENERAL  CONSIDERATIONS.  3 

GENERAL     IDEA     OF     THE     OEGANISATION     OF     ANIMALS. 

Order  followed  in  studying  the  Various  Apparatus. 

The  bodies  of  animals,  formed  of  organised  matter,  contain  fluids  and 
solids. 

The  fluids  are  very  abimdant  in  the  animal  economy ;  not  only  do  they 
fill  certain  vessels  constructed  for  them,  but  they  also  impregnate  all  the 
solid  parts  of  the  body.  Their  importance  is  very  great,  for  witlioiit  them 
the  organic  solids  would  perish ;  an  element  deprived  of  humidity  is  an 
element  deprived  of  life. 

Fluids  vary  in  their  nature  and  composition.  Apart  from  those  that 
the  solids  imbibe,  there  is  not  one  whicb  is  completely  amorphous.  In  the 
midst  of  a  liquid  holding  organised  matter  in  solution  there  are  always 
elements  which  will  be  referred  to  hereafter.    Examples  :  the  blood  and  lymph. 

In  studying  the  organic  solids,  we  will  proceed  from  the  simple  to  the 
complicated. 

Elements. — Solid  organised  matter  presents  itself  in  the  form  of  more  or 
less  voluminous  particles,  in  every  instance  invisible  to  the  naked  eye,  and 
named  the  anatomical  elements.  They  may  be  reduced  to  three  principal : 
the  granule,  cell,  and  fibre. 

Granules. — These  are  the  smallest  known  elements.  They  may  be  held 
in  suspension  in  animal  fluids,  remain  free  among  the  other  elements,  or  be 
enclosed  in  the  interior  of  cells.  Their  nature  is  not  always  the  same : 
they  are  proteic  or  fatty.  They  are  called  pigmentary  when  they  exhibit 
a  brown  colour. 

Cells. — The  cell  is  pre-eminently  the  anatomical  element. 

It  may  be  represented  to  the  mind  as  a  microscopic  collection  of  a 
nitrogenous  substance,  viscid  or  slightly  granular,  and  endowed  with  extreme 
vitality.  Frequently  in  the  midst  of  this  protoplasm  (for  so  it  has  been 
called),  there  is  perceived  a  nucleus  provided  with  a  nucleolus,  and  at  its 
periphery  an  enveloping  membrane  is  discovered.  It  must  not  be  forgotten 
that  this  membrane,  and  even  the  nucleus,  is  necessarily  a  constituent  portion 
of  the  cell. 

The  cell  lives  like  an  entire  organism  :  it  feeds,  grows,  nniltiplies, 
absorbs,  secretes,  moves,  etc.  It  behaves  like  a  complete  animal,  though  it 
be  a  microscopic  one. 

The  form  of  the  cell  varies  greatly,  as  does  its  volume  and  its  nature. 
It  has  therefore  received  various  names. 

There  are  round,  polyhedral,  fusiform,  stellate,  and  other  shaped  cells. 
Some  have  a  diameter  of  l-12000th  part  of  an  inch,  while  others  are  l-2000th 
part.  Cells  multiply  in  various  ways :  1st,  by  the  division  of  the  nucleus 
and  segmentation  of  the  protoplasm  in  the  interior  of  the  enveloping 
membrane  (endogenous  multiplication);  2nd,  by  constriction,  the  division 
of  the  nucleus,  protoplasm,  and  enveloping  membrane  [fissiparous  midtipli- 
cation)  ;  3rd,  by  a  kind  of  bulging  or  swelling  of  the  enveloping  membrane, 
and  strangulation  and  separation  of  the  enlargement  thus  formed 
{gemmation). 

A  large  number  of  cells  only  temporarily  remain  in  this  condition.  In 
consequence  of  modifications  that  cannot  be  referred  to  here,  they  are  con- 
verted into  fibrillse  or  other  elements,  in  which  it  is  difficult  to  recognise 
them. 

Others  maintain  the  cellular  form :  then  they  are  developed,  live,  and 
die  in  several  ways.     Sometimes  they  are  worn  by  the  contact  of  foreign 


i  GENERAL  CONSIDEBATIOXS. 

bodies,  as  on  the  surface  of  tlie  skin  ;  at  other  times  they  become  dissolved, 
as  in  some  glands  :  finally,  at  other  periods  they  submit  to  fatty  degeneration, 
which  gradually  brings  about  their  complete  destruction. 

The  permanent  cells  have  been  arranged  according  to  the  following 
denominations  : — 

1.  Ucematies  or  red  globules,  which  are  found  in  a  state  of  suspension 

in  the  blood ;  they  are  round  or  elliptical. 

2.  Leucocytes,  or  ichite  globules,  which  float  in  the  blood,  lymph,  and  chyle. 

3.  Connective  cells,  comprising  the  connective  cell  properly  so-called, 

the  plasmatic  cell,  and  the  adipose  cell. 

4.  Medullary  cells,  forming  the  principal  elements  of  the  marrow  of 

bones  (myeloplaxes  and  medullo-cells). 

5.  Coniractile  cells,  which  constitute  the  basis  of  muscular  tissue. 

6.  Nerve  cells,  met  with  in  the  cerebro-spinal  centres  and  the  ganglia 

of  the  cerebro-spinal  and  sympathetic  systems. 

7.  Epithelial   cells,   comprising   the    epithelial    cells    properly    called, 

situated  on  the  surface  of  the  skin  and  mucous  membranes,  and 
the  glandular  cells. 

Fibres. — A  fibre  is  an  elongated  anatomical  element,  of  variable  dimensions 
and  composition.  It  may  be  very  fine  and  represented  by  a  single  line,  or 
thicker  and  marked  by  two  lines  more  or  less  apart  from  one  another.  It 
is  homogeneous  throughout,  or  the  contents  are  distinct  from  the  envelope. 

The  vitality  of  fibres  is  not  to  be  compared  with  that  of  cells  ;  after  they 
are  formed,  they  can  only  be  nourished,  and  cannot  multiply  of  themselves. 
In  the  animal  economy  four  kinds  of  fibres  are  distinguished  : — the  connective 
fibre,  elastic  fibre,  muscidar  fibre,  and  nervous  (or  nerve)  fibre. 

Tissues. — Tlie  elements  that  have  now  been  rapidly  described,  in 
becoming  united  and  grouped  in  diflerent  fashions,  form  the  tissues. 

Some  tissues  are  composed  of  one  kind  of  element ;  these  are  the  simple 
tissues.     Example : — The  epithelium. 

The  majority,  however,  are  formed  by  the  union  of  several  different 
elements  :  these  are  the  composite  tissues.     Example  : — Nervous  tissue. 

It  is  also  remarked  that  there  are  tissues  in  which  exists  a  fundamental 
intercellular  substance,  and  others  in  which  this  is  absent.  The  latter  are 
few  in  number,  for  the  vessels  and  nerves  may,  in  certain  tissues,  be 
considered  as  intercellular  substance. 

The  anatomical,  physico-chemical,  and  physiological  characters  of  the 
tissues  repeat,  as  might  easily  be  inferred,  the  anatomical,  physico-chemical, 
and  physiological  properties  of  the  elements  entering  into  their  formation. 

Only  four  fundamental  tissues  are  recognised,  basing  them  on  the 
morphological,  chemical,  and  physiological  characters  of  the  elements. 

In  the  first  place,  the  tissue  of  the  conjunctivcd  substance  should  be  noticed ; 
this,  in  consequence  of  some  differential  characters,  may  be  divided  into : — 
gelatinous  tissue,  conjunctival  (or  connective)  tissue,  cartilaginous  tissue,  and  boni/ 
tissue. 

Then  comes  the  cellular  tissue,  formed  entirely  of  persistent  cells.  It 
comprises  the  epithelial  tissue  and  the  glandular  tissue. 

The  cells  of  the  epithelial  tissue  may  aftcct  different  arrangements.  If 
they  are  disposed  in  a  single  row,  there  results  a  simple  epithelium  ;  if  they 
are  superposed  it  is  a  stratified  epithelium.  According  to  the  form  of  the 
cells  of  the  superficial  layer,  the  epithelium  is  polyhedral,  pavement,  cylindrical, 
or  sphericcd.  In  certain  points,  these  superficial  cells  are  furnished  with 
vibratile  filaments ;  they  are  then  designated  vibratik  (or  ciliated)  e^pithelium. 


GENERAL  CONSIDERATIONS.  5 

In  tlie  third  place,  is  tlae  muscular  tissiie,  which  may  be  divided  into 
striated  and  non-striated  (or  striped,  and  non-striped  or  smooth)  fibres. 

Lastly  comes  the  nervous  tissue,  whicli  offers  two  aspects :  the  white  and 
grey  substance.  The  tii-st  is  entirely  formed  by  nerve  fibres,  and  the  second 
by  fibres  and  nerve  cells. 

Organs. — The  term  organ  is  given  to  an  agglomeration  of  tissues 
possessing  a  determinate  form,  and  having  a  function  to  fulfil.  Organs  are 
therefore  composed  of  tissues,  as  the  tissues  themselves  are  constituted  by 
anatomical  elements. 

All  animal  organs  are  enclosed  between  two  membranes  named  limitary 
or  tegumentary  membranes,  which  are  continuous  with  one  another  at  the 
margin  of  the  natural  openings.  These  are  the  skin  and  the  mucous 
membranes,  in  whose  composition  is  included  a  layer  of  connective  tissue 
covered  by  an  epithelium. 

Organs  are  distinguished  into  those  which  are  solid,  and  those  which  are 
hollow. 

Among  the  first,  a  certain  number  act  as  supports :  such  are  the  organs 
formed  by  the  connective  tissue,  and  particularly  the  cartilages  and  bones. 

Others  are  destined  to  produce  movements :  these  are  the  two  kinds  of 
muscles.  The  action  of  the  muscles  is  communicated  directly  to  the  organs 
that  are  to  be  moved,  or  it  is  transmitted  through  the  medium  of  other 
organs,  such  as  the  tendons  and  ai)oneui'oses. 

The  central  nervous  organs,  nerves  properly  so  called,  and  the  vascular 
glands,  belong  to  this  group  of  solid  organs. 

With  regard  to  the  hollow  organs,  they  are  everywhere  covered  by  the 
internal,  tegumentary,  or  mucous  membrane.  Examples  : — the  lungs  and 
stomach.  There  must  also  be  included  the  vessels  formed  by  elastic  and 
contractile  membranes  arranged  as  canals,  in  which  the  blood  and  lymj^h 
circulate ;  and,  lastly,  the  serous  membranes,  which  line  the  interior  of  the 
splauclmic  cavities,  and  cover  the  sm-face  of  the  organs  contained  in  them. 

Apparatus. — Organs  are  very  numerous  in  the  animal  economy,  and  in 
order  to  study  them  profitably  it  is  necessary  to  classify  them  in  a  methodi- 
cal manner,  according  to  their  physiological  afiinities.  Consequently,  there 
have  been  collected  into  a  single  category  all  those  organs  which  are  destined 
to  achieve  the  same  physiological  finality,  and  to  such  a  group  has  been  given 
the  name  of  fljjpara^HS. 

An  apparatus  is,  then,  an  assemblage  of  all  those  organs  of  an  animal 
which  concur  to  the  same  end,  and  which  serve  for  the  accomplishment  of 
the  same  function. 

We  will  successively  describe,  in  the  following  order,  the  different  appa- 
ratus of  which  the  organism  is  composed  : — 

1.  Locomotm'y  Apparatus ; 

2.  Digestive  Apparatus ; 

3.  Respiratory  Apparatus  ; 

4.  Urinary  Depurative  Apparatus  ; 

5.  Circulatory  Apparatus; 

6.  Innervatory  Aj^paratus ; 

7.  Sensory  Apparatus  ; 

8.  Generative  Apparatus  ; 

This  description  will  be  terminated  by  a  brief  exposition  of  the  evolution 
of  the  foetus  and  its  appendages. 

4 


BOOK  I. 

LocoMOTORY  Apparatus. 

The  locomotory  apparatus  is  composed  of  all  those  organs  which  minister  to 
the  movements  an  animal  may  execute.  It  is  certainly  one  of  the  most  im- 
portant in  the  economy,  from  the  number  and  volume  of  the  pieces  which 
enter  into  its  formation,  and  by  the  necessary  co-operation  that  it  affords  the 
other  apparatus  in  the  performance  of  the  physiological  acts  which  are 
allotted  to  them. 

It  is  constituted  of  two  kinds  of  organs ;  the  bones  and  muscles.  The 
hones,  hard  and  resisting,  stony  in  appearance,  are  real  inert  levers,  joined  to 
each  other  by  firm  and  movable  articulations,  which  permit  their  playing 
upon  each  other  with  the  greatest  facility,  at  the  same  time  maintaining 
them  in  tlieir  relative  positions.  The  muscles,  grouped  around  the  bones 
and  attached  to  them,  are  soft  organs  which  possess  the  pro^jerty  of  contrac- 
tion, under  certain  determinate  conditions  and  of  involving  in  that  move- 
ment the  bones  to  which  they  are  fixed  by  their  extremities.  The  first  are 
altogether  passive  in  their  motion,  while  the  second  are  really  the  active 
.organs  of  locomotion — the  powers  intended  to  move  the  bony  levers. 

We  will  treat  successively  of: — 

1.  The  study  of  the  bones,  a  particular  branch  of  descriptive  anatomy 

whicli  has  received  the  name  of  osteology  ; 

2.  The  study  of  the  articulations,  or  arthrologtf  , 

3.  The  study  of  the  muscles,  or  myology. 


FIKST  SECTION. 
The  Bones. 

CHAPTEE  L 

THE    BONES   IN   GENERAL. 


Bones,  properly  speaking,  are  only  to  be  found  in  vertebrate  animals,  and 
constitute  their  principal  zoological  character.  In  the  animal  body  they 
form  an  internal  framework  which  consolidates  the  entire  edifice,  and  gives 
it  its  general  form  and  dimensions.  It  is  advantageous,  before  commencing 
a  particular  description  of  each  bone,  to  survey  them  in  a  general  manner. 
This  study  comprises  :  1,  The  description  of  the  skeleton  ;  2,  The  summary 
indication  of  the  general  principles  which  should  be  known  in  order  to  com- 
prehend the  details  of  the  special  descriptions. 


TEE  SKELETON.  7 

Article  I. — The  Skeleton. 

The  whole  of  the  bones,  considered  in  their  natural  relations  to  each 
other,  constitute  the  skeleton.  In  order  to  prepare  the  skeleton  of  any 
animal,  it  is  sufficient  to  free  it  from  the  soft  parts  surrounding  it.  The 
skeleton  should  be  designated  natural,  if  in  this  operation  the  ligaments 


SKELETON    OF    THE   DOG. 

Tig-.  2. 


SKELETON   OF   THE   PIG. 


8  THE  BONES. 

that  naturally  join  the  various  pieces  together  are  allowed  to  remain  ;  and 
artificial  if,  after  these  ligaments  have  been  destroyed,  it  is  necessary  to 
replace  them  by  materials  foreign  to  organisation,  such  as  iron  or  brass 
wii'e. 

The  skeleton  is  divided  into  trunk  and  limbs. 

The  trunk  offers  for  consideration,  in  the  median  line,  the  sjnne  or 
vertebral  column,  a  flexible  stalk  measuring  the  entire  length  of  the  animal, 
and  composed  of  a  series  of  distinct  pieces  articulated  one  behind  the 
other.  Anteriorly,  this  stalk  supports  the  head,  a  pyramidal  protuberance 
which  itself  results  from  the  assemblage  of  a  large  number  of  bones. 
On  each  side  of  the  middle  portion  of  the  spine,  there  are  detached  bony 


SKELETON   OF   THE   HORSE. 


arches  which  have  received  the  name  of  ribs,  and  which  rest,  directly 
or  indu'ectly,  by  their  inferior  extremities,  on  a  single  bone  called  the 
sternum.  These  bony  arches  in  this  way  circumscribe  the  tliorax,  a 
spacious  cavity  destined  for  the  reception  of  the  principal  organs  of  re- 
spiration and  circulation. 

The  limbs,  four  in  number,  two  anterior  and  two  posterior,  are  the 
appendages  which  support  the  trunk.  Each  represents  a  column  divided 
into  several  rays  resting  upon  one  another,  and  generally  forming  more 
or  less  acute  angles.  The  anterior  limbs  are  each  divisible  into  four 
principal  regions  :  the  shoulder,  applied  against  the  front  jiart  of  the  thorax ; 
the  arm,  which  succeeds  the  shoulder ;  and  the  fore-cmn  and  foot.  The 
posterior  limbs  also  comprise  four  regions :  the  haunch  or  pelds,  which 
articulates  with  the  posterior  part  of  the  spine :  and  the  thigh,  leg,  and 
posterior  foot. 


THE  SKELETON.  9 

In  birds,  the  posterior  limbs  alone  assume  the  function  of  columns 
of  support.  The  anterior  limbs,  formed  for  flight,  constitute  the 
wings. 

Fig.  4. 


SKELETON  OF  THE  COW, 
Fis.  5. 


SKELETON  OF  THE  SHEEP. 


The  number  of  bones  entering  into  the  composition  of  the  skeleton  of 
the  domesticated  animals,  arrived  at  the  adult  period  of  life  varies  according 


10 


GENERAL  PRINCIPLES  APPLICABLE  TO 


to  the  species.     They  are  apportioned  to  the  regions  of  the  trunk  and  limbs 
just  mentioned,  in  the  manner  indicated  in  the  following  table : 


DESIGNATION. 


Vertebral  Column ' 
Head*    .... 
Thorax  .... 
Shoulder  .  1 
Arm   .      .  I 
Fore-arm.  | 
Fore-foot . 
Pelvis 
Thigh      . 
Leg    .      . 
Hind-foot 


Double  regions 


Solipeds.i 

Ruminants. 

Pig. 

Dog.2 

44 

43 

42 

43 

28 

28 

29 

28 

37 

27 

29 

27 

1-2 

1-2 

1-2 

1-2 

1-2 

1-2 

1-2 

1-2 

2-4 

2-4 

2-4 

2-4 

16-32 

20-40 

36-72 

36-72 

1-2 

1-2 

1-2 

1-2 

1-2 

1-2 

1-2 

1-2 

3-6 

3-6 

3-6 

3-6 

15-30 

19-38 

30-72 

32-64 

Article  II. — General  Principles  Applicable  to  the  Study  of  all 

THE  Bones. 

The  description  of  any  bone  comprises  its  name,  situation,  direction, 
conformation,  structure,  and  mode  of  development. 

Name. 
The  nomenclature  of  osteology  does  not  rest  on  any  basis  capable  of 
conferring  upon  it  a  methodic  form.  Consequently,  we  find  bones  which 
derive  their  name  from  their  shape,  (example  :  the  fibula) ;  others  from 
their  resemblance  to  known  objects  (the  tibia  and  vomer).  Some  owe  it 
to  their  position  (cotes,  sides  or  ribs),  or  their  uses  (the  axis  and  parietal 
bones).  Several  attempts  have  been  made  to  submit  the  nomenclature  of 
the  bones  to  more  precise  and  uniform  rules,  but  the  new  designations 
proposed  have  not  been  sanctioned  by  custom. 

Situation. 

The  situation  of  a  bone  should  be  viewed  in  two  ways :  1st,  Relative  to 
tlie  median  plane  of  the  body  ;  2ud,  Belative  to  the  other  portions  of  the  skeleton. 

A.  Situation  relative  to  the  median  plane  of  the  body.  The  designation 
of  median  plane,  or  improperly  median  line,  is  given  to  an  imaginary  vertical 
plane,  passing  through  the  middle  of  the  skeleton  which  it  divides,  from 
before  to  behind,  into  two  equal  portions.  The  bones  may  be  situated 
on  the  median  plane,  in  which  case  there  is  only  one  of  each  kind,  and 
they  are  called  single;  they  are  also  named  symmetrical  bones,  because 
the  median  plane  divides  them  into  two  equal  lateral  halves  exactly  alike. 
The  bones  disposed  in  a  double  and  regular  manner  on  the  sides  of  the 
median  plane  bear,  for  this  reason,  the  name  of  pairs ;  they  are  also  called 
asymmetrical  bones,  because  their  form  does  not  admit  of  their  being 
separated  in  any  sense  into  two  similar  portions.  On  the  contrary,  a  bone 
of  this  kind  always  offers  the  most  perfect  symmetry  with  its  fellow  on  the 
opposite  side. 

'  One  lumbar  vertebra  less  is  found  in  the  ass,  and  sometimes  also  in  the  mule. 
'  The  OS  penis  has  not  been  included. 

'  The  sacrum  is  reckoned  as  a  single  bone,  and  the  number  of  coccygeal  vertebrae  at 
an  average  of  12  for  the  Horse,  16  for  the  Ox,  14  for  the  Pig,  and  15  for  the  Dog. 
*  The  OS  hyoides  comprises,  and  is  reckoned  as,  a  single  bone. 


TEE  STUDY  OF  THE  BONES.  11 

B.  Belative  situation  to  the  other  parts  of  the  skeleton. — To  indicate  the 
situation  of  a  bone,  considered  from  this  point  of  view,  is  to  make  known  the 
place  it  occupies  in  the  region  to  which  it  bek^ngs,  and  the  connections  it  may 
have  with  adjoining  regions.  Thus  the  radius  is  situated  in  front  of  the 
ulna  between  the  arm-bone  and  the  carpus. 

Direction. 

This  is  absolute  or  relative.  The  direction  of  a  bone  may  be  vertical, 
horizontal,  or  oblique.  Example :  the  scapula  is  placed  in  an  oblique  direc- 
tion from  above  to  below,  and  from  behind  to  before. 

Configuration  of  the  Bones. 

Form. — This  is  also  absolute  or  relative. 

A.  Absolute  Form. — The  absolute  form  of  a  bone  is  that  which  it  owes  to 
the  relations  existing  between  its  three  dimensions — length,  width,  and 
thickness,  a.  A  bone  in  which  one  of  its  dimensions  much  exceeds  those  of 
the  other  two  is  a  long  bone.  Example  : — the  femur.  All  the  long  bones  are 
hollowed  out  internally  by  an  elongated  space — the  medullarij  cavity.  Long 
bones  belong  exclusively  to  the  limbs.  In  the  animal  economy,  there  are  found 
bones  which  resemble  them  in  their  dimensions,  but  they  have  no  medullary 
canal.  Example  :^the  ribs.  These  differ  essentially  from  the  true  long 
bones,  and  are  sometimes  distinguished  from  them  by  the  appellation  of 
elongated  bones,  b.  A  bone  that  offers  two  dimensions  much  more  developed 
than  the  third,  is  a  flat  or  ivide  bone.  Example  : — the  parietal  bone.  The 
bones  of  this  category,  destitute  of  a  medullary  cavity,  are  met  with  in  the 
head  and  the  upper  regions  of  the  limbs,  c.  A  bone  which  offers  nearly  the 
same  development  in  all  its  dimensions,  is  called  a  short-bone.  Example : — 
the  astragalus.  Destitute,  like  the  preceding,  of  a  medullary  cavity,  the 
short  bones  are  found  in  the  spine  and  some  regions  of  the  limbs. 

B.  Belative  Form. — To  make  known  the  relative  form  of  a  bone  is  to 
indicate  the  greater  or  less  exact  resemblance  it  may  bear  to  geometrical 
figures,  or  to  familiar  objects.  Thus  the  scapula  is  a  bone  of  a  triangular 
form. 

External  Peculiarities  of  Bones. — These  markedly  attract  the  atten- 
tion, because  they  modify  the  general  shape  of  bones,  and  singularly  assist 
us  in  distinguishing  one  bone  from  another.  These  peculiarities,  which  are 
real  distinctive  features  that  permit  their  description  to  be  precisely  esta- 
blished, are  always  either  eminences  {processes)  or  depressions. 

Eminences. — The  eminences  that  stand  out  in  relief  from  the  surfaces  of 
bones  are  divided  into  two  different  categories.  One  class  concurs  in  the 
formation  of  the  articulations  which  join  the  bones  to  each  other ;  they  are 
named  articular  eminences,  in  which,  again,  are  distinguished  dinrthrodial  and 
synarthrodial  eminences,  according  as  they  belong  to  movable  or  immovable 
articulations.  The  others,  usually  destined  for  the  insertion  of  ligaments 
and  muscles,  are  called  non-articular,  or  eminences  of  hisertion. 

(The  term  imprint  is  also  used  in  anatomy,  and  signifies  a  collection  of 
small  rugged  eminences  which  make  the  surface  of  the  bone  uneven  and 
rough.  There  are  muscular,  tendinous,  ligamentous,  and  aponeurotic  im- 
prints, according  as  they  give  attachment  to  muscles,  tendons,  ligaments,  or 
aponeuroses.) 

The  synarthrodia!  eminences  are  always  indentations  more  or  less  deep 
and  finely  cut. 


12  GENERAL  PRINCIPLES  APPLICABLE  TO 

The  diarthrodial  eminences  are  voluminous  and  smooth,  and  in  a  fresh 
state  are  covered  with  cartilage.  They  are  named  heads  and  condyles : 
heads,  when  they  describe  the  segment  of  a  sphere  (head  of  the  femur,  head 
of  the  humerus)  ;  condyles,  when  they  represent  the  segment  of  an  oval 
figure,  cut  parallel  to  its  large  axis  (condyles  of  the  femur.) 

The  non-articular  eminences  receive  various  names.  If  they  are  volumi- 
nous and  much  detached  from  the  bone,  they  are  called  processes  or  apophyses. 
Apophyses  receive  qualificatives  derived  from  the  analogies  jierceived  between 
them  and  knowTi  objects.  (Examples : — the  styloid,  clinoid,  corouoid  and 
coracoid  processes.)  The  appellations  of  protaherances  and  tuberosities 
are  given  to  non-articular  eminences  when  they  are  large  and  round,  and 
but  slightly  prominent.  Lastly,  they  are  named  lines,  crests,  and  ridges, 
when  they  are  narrow  and  very  long. 

Cavities. — The  cavities  of  bones  have  also  been  divided  into  articular  and 
non-articular  cavities. 

The  first  correspond  to  the  eminences  of  the  same  name  in  the  bony 
joints.  They  take  the  designation  of  cotyloid  cadties  when  they  are  deeply 
excavated,  like  a  basin  or  the  cup  of  an  acorn  (the  glenoid  cavity  of  the 
scapula,  and  the  cotyloid  cavity  of  the  coxa). 

The  non-articular  cavities  serve  either  for  ligamentous  or  muscular 
implantation,  or  for  the  passage  of  vessels,  nerves,  tendons,  etc. 

They  are  termed  channels  or  fiirroics,  when  they  are  wide,  deep,  and 
smooth ;  grooves,  when  they  are  long,  narrow,  and  even  at  the  bottom  ; 
fissures,  when  they  are  narrow  and  rough.  Digital  impressions  is  the  name 
given  to  those  excavations  in  bones  which  look  as  if  produced  by  the 
pressure  of  the  finger.  The  fossce,  sinuses,  cells,  and  notches  are  also  non- 
articular  cavities  of  bones.  The  sinuses  and  cells  are  formed  by  open 
spaces  in  the  interior  of  bones;  notches,  by  cavities  excavated  on  their 
margins. 

When  a  cavity  passes  quite  through  a  bone  it  is  termed  a  foramen.  If 
this  foramen  offers  a  certain  length,  it  is  then  designated  a  conduit  or  canal. 
Fissures  are  long,  narrow  foramina;  hiatus  is  the  term  aj)plied  to  wide 
openings  with  irregular  outlines. 

Regions  of  the  Bones. — When  it  is  desired  to  describe  the  eminences 
and  external  cavities  of  a  bone,  it  is  essential  not  to  notice  them,  as  it  were, 
by  chance — passing  indifferently  from  one  to  another.  In  order  to  avoid 
the  difficulties  which  would  result  from  the  application  of  such  an  irrational 
system,  it  is  convenient  to  divide  the  bone  to  be  described  into  several 
regions,  in  which  are  examined,  one  after  another,  all  the  external  peculiari- 
ties that  may  offer. 

The  following  is  the  course  to  pursue  in  order  to  establish  the  regions 
of  a  long,  a  flat,  and  a  short  bone. 

(rt)  A  long  bone  is  always  divided  into  three  parts :  a  body  and  two 
extremities.  The  body,  middle  part,  or  dlaphysis,  is  the  narrowest  portion  of 
the  bone.  It  represents  a  geometrical  solid,  approaching  more  or  less  the 
figure  of  a  very  elongated  prism.  In  a  long  bone,  therefore,  it  is  necessary 
to  study  as  many  faces,  angles,  or  borders,  as  the  prism  it  represents  may 
offer. 

With  regard  to  the  extremities,  or  epiphyses,  these  are  more  or  less  con- 
siderable enlargements,  showing  articular  surfaces,  as  well  as  surfaces 
intended  for  muscular  or  ligamentous  insertion. 

(h)  A  flat  bone  must  necessarily  have  two  faces,  as  well  as  borders  and 
angles. 


THE  STUDY  OF  THE  BONES. 


13 


(c)  A  short  bone  offers  for  description  a  variable  number  of  faces,  and 
plane  or  salient  angles,  which  are  often  neglected  because  of  theii-  trifling 
importance. 

Internal  Conformation  of  Bones. 

Sections  made  in  various  directions  through  the  substance  of  bones  show 
that  theii*  internal  conformation  varies,  according  as  they  belong  to  the 
category  of  long,  flat,  or  short  bones.  The  diaphysis  of  long  bones  is 
hollowed  out  into  a  large  fusiform  cavity ;  this  is  the  medullary  canal. 
This  canal  is  absent  in  the  flat  and  short  bones.  Its  walls  are  formed  by  a 
very  dense  bony  tissue,  whose  pores  are  scarcely  visible  to  the  naked  eye, 
and  which  is  called  the  compact  substance.  The  extremities  of  long  bones 
are  surroimded  by  a  thin  layer  of  compact  substance,  while  the  remainder 
of  their  mass  is  constituted  by  the  sjMngy  substance — bony  tissue  channeled 
into  cells,  or  very  large  areolae,  which  freely  communicate  with  each  other. 
(Reticulated  bony  tissue  is  but  another  form  of  spongy  substance,  the  only 
diflerence  between  the  two  consisting  in  the  cells  or  meshes  of  the  first 
being  formed  of  intercrossed  osseous  fibres,  while  those  of  the  second  are 
formed  of  lamellce.)  The  medullary  canal,  and  areolfe  of  the  spongy  tissue, 
are  filled  by  a  cellulo-fatty  substance,  the  marroio  (or  medulla).  The  flat 
bones  are  constituted  by  a  layer  of  spongy  tissue  placed  between  two  laminfe 
of  compact  substance.  In  the  flat  bones  of  the  cranium,  the  two  layers  of 
compact  tissue  are  termed  the  vitreous  tables,  while  the  cells  of  the  spongy 
tissue  are  designated  diploe.  In  certain  points  of  their  extent,  the  spongy 
substance  disappears,  and  then  the  bone  is  found  to  be  composed  of  a  single 
lamina  of  comj^act  tissue.  The  short  bones  have  a  nucleus  of  spongy 
substance,  enveloped  in  a  layer,  more  or  less  thick,  of  compact  tissue. 

The  compact  substance  of  the  bones  being  very  resisting,  is  found  in  all 
those  situations  which  have  to  sustain  violent  efforts.  The  spongy  substance 
is  very  light  and  bulky,  and  is  met  with  in  the  widened  portions  of  the 
bones,  to  which  it  affords  increased  size  without  adding  sensibly  to  their 
weight. 

Structure  of  Bones. 

Bones  are  formed  of  a  proper  tissue,  covered  externally  by  a  particular 
membrane,  the  periosteum,  and  occupied  internally 
by  the  medulla,  vessels,  and  nerves. 

Proper  tissue. — The  texture  of  the  proper  tissue 
of  bones  varies  slightly  in  the  compact  and  spongy 
substance. 

The  compact  tissue  is  composed  of  a  funda- 
mental substance,  which  is  amorphous,  or  slightly 
granular,  white,  and  more  or  less  opaque,  accord- 
ing to  the  thickness  it  offers. 

This  fundamental  substance  is  penetrated  by 
an  infinite  number  of  vascular  canaliculi,  known 
as  the  Haversiayi  canals.  These  canals,  which 
measure  from  l-2500th  to  l-200th  of  an  inch  in 
diameter,  are  parallel  to  each  other  and  to  the 
larger  axis  of  the  bone ;  they  frequently  com- 
municate   by    transverse    branches.      The    most  „ ,  ^„   „^„„ 

r.    ■    ^       ''  ^1  J,  J.    XT         1  1  VERTICAL    SECTION    OF     BONE, 

superficial  open  on  the  surfixce  oi  the  bone,  be-      showin"    the    network    of 
neath  the  periosteum,  and  the  deepest   into  the      Haveisfan  canals. 


u 


GENERAL  FRINCIFLES  AP  FLIC  ABLE  TO 


medullary  canal;  while  a  certain  number  tei-minate  in  the  areolaa  of  the 

spongy  substance. 

The  walls  of  these  canals  are  constituted  by  several  concentric  lamellaa 

of  fundamental  substance,  and  in 
"■    ■  the  body  of  these  are  lodged  the 

essential  elements  of  the  bony 
tissue,  or  osteoplasts  {corpuscles  or 
lacunce).  These  are  minute  cavi- 
ties lined  by  a  cellular  membrane, 
and  furnished,  at  their  circum- 
ference, with  a  great  number  of 
canaliculated  prolongations,  which 
communicate  with  the  adjacent 
osteoplasts,  or  with  the  Haversian 
canals.  In  a  thin  dried  section 
of  bone,  the  osteoplasts  appear 
black  by  transmitted  light,  and 
white  and  brilliant  by  direct  light ; 

MINUTE  STRCCTURE  OF  BONE,  as  shown  in  a  tliin   tjjjg  appeai-ance  has  led  some  ob- 

spction  cut  transversely  to  the  direction  of  the  ,  ii    j.   j.\ 

setiiou  cuL  Lictusveiscij  Ku  servers  to  suppose  that  they  were 

Haversian  canals.  „  ^      />  ^^  n       ^ 

1,  A  Haversian  canal  surrounded  by  its  concentric  formed  of  small  masses  of  calca- 
lamellce;  the  lacunre  are  seen  between  the  la-  reous  matter,  it  IS  noW  well 
mella;,  but  the  radiating  tubuli  are  omitted;  knowu  that  they  are  minute 
2,  Ibid,  with  its  concentric  lamina,  lacunae,  and  ramifying  cavities,  lodging  a  cell 
radiating  tubuli;  3,  The  area  of  o^e  of  the  i^preanated  with  liquid, 
canals;  4,  4,  Intervening  lamellai,  and  between 
them,  at  the  upper  part,  several  very  long 
lacunse  with  their  tubuli. 


Fi9c.  8. 


LACUN.E,  OR  OSTEOPLASTS  OF   OSSEOUS   SUBSTANCE, 

magnified  500  diameters. 


imjwegnatea  witn  liqui 

In  the  spongy  texture  no 
Haversian  canals  can  be  seen , 
the  osteoplasts  are  irregularly 
disposed  in  the  thickness  of  the 
fundamental  substance,  which  con- 
stitutes the  septa  of  the  areolae  of 
this  tissue. 

As  a  rule,  the  proper  tissue  of 
the  bones  is  composed  of  a  frame- 
work of  organic  matter  which  has 
gelatine  for  its  base,  and  in  which 
are  deposited  the  calcareous  phos- 
phates and  carbonates,  which  give 
to  this  tissue  its  characteristic 
a,  Central  cavity ;  b,  Its  ramifications.  i^^^rdness.     This  is  easily  rendered 

evident  by  immersing  any  bone  in  dilute  nitric  or  hydrochloric  acid  ;  acids 
dissolve  the  calcareous  salts,  but  do  not  act  upon  the  organic  framework. 
So  it  is  that,  after  some  days'  maceration,  the  bone  becomes  flexible,  like 
cartilage,  and  loses  part  of  its  weight,  although  it  preserves  its  volume. 
The  counterpart  of  this  experiment  may  be  made  by  submitting  it  to  the  action 
of  fire.  It  is  then  rendered  quite  friable,  because  its  organic  skeleton  has 
been  destroyed  without  the  earthy  salts  it  contained  being  affected. 

Periosteum. —  This  is  a  very  vascular  and  nervous  fibrous  membrane  that 
covers  the  entire  bone,  with  the  exception  of  the  articular  surfaces.  Its 
thickness  and  adliercnce  are  not  the  same  everywhere.  By  its  inner  face  it 
corresponds  to  the  surface  of  the  bone  ;  by  its  external  face,  it  is  confounded 
with  the  insertion  of  the  tendons  and  ligaments,  or  with  the  surrounding 
connective  tissue. 


THE  STUDY  OF  THE  BONES.  15 

The  periosteum  may  be  resolved  into  two  layers,  though  these  are  not 
very  distinct.  The  superficial  layer  is  essentially  fibrous,  and  is  formed  by 
a  mixture  of  connective  and  elastic  fibres  and  plasmatic  cells.  The  deep 
layer  also  contains  a  loose  connective  tissue,  but  more  especially  elastic 
fibres,  and  more  or  less  voluminous  sj)herical  or  fusiform  cells.  This  is 
called  the  osteofjenotis  layer. 

Medulla. — The  medulla,  or  marrow,  is  a  pulpy,  fatty  substance,  which  fills 
the  medullary  canal  and  the  areolaB  of  the  spongy  tissue  of  the  bones. 
Somewhat  consistent,  and  of  a  rose  tint  in  the  bones  of  the  young  animal,  the 
marrow  becomes  difiiueut  and  yellow  in  the  bones  of  those  advanced  in  age. 
In  the  first  instance,  it  only  contains  traces  of  fat;  while  in  the  second  it  has 
96  per  cent,  of  this  substance.  The  medulla  of  bones  is  composed  of: 
1st,  Some  trabeculfe  of  delicate  connective  tissue,  which  serves  to  support 
the  vessels  and  nerves ;  2nd,  Fat  either  free  or  inclosed  in  vesicles ; 
3rd,  Particular  cells,  named  by  M.  Kobin  meduUo-cells  and  myeloplaxes. 

The  medulla  cells,  abundant  in  the  red  or  foetal  marrow,  are  small  cells 
with  a  spherical  nucleus;  while  tlie  myeloplaxes  are  large,  flattened,  or 
polyhedral  elements  of  an  irregular  outline,  containing  a  great  number  of 
nuclei.  Rare  in  the  yellow  marrowy  they  are  more  particularly  found 
adhering  to  the  walls  of  the  medullary  canal,  or  the  alveoli  of  the  spongy 
tissue. 

Blood-vessels. — The  arteries  of  bones  belong  to  three  orders  ;  a  distinction 
founded  on  their  volume  and  the  extent  of  their  distribution. 

The  arteries  of  the  fii'st  order  penetrate  to  the  interior  of  the  medullary 
canal  of  long  bones  by  a  particular  orifice,  the  nutritious  foramen.  They 
soon  divide  into  two  branches,  which  break  uj)  into  a  network  that  lines  the 
walls  of  the  canal  and  enters  the  tissue  of  the  medulla.  Tliis  network 
communicates  with  the  arteries  of  the  second  order,  which  are  destined  to 
the  spongy  tissue  of  the  extremities  of  the  long  bones,  penetrating  them  by 
the  numerous  nutritious  foramina  that  surround  the  epiphyses.  Lastly,  the 
arteries  of  the  third  order  are  branches  of  the  i:)eriostic  network  which  enter 
the  superficial  Haversian  canals.  These  canals  which  open  in  this  manner 
on  the  surface  of  the  bones  may  be  considered,  strictly  speaking,  as  a  third 
category  of  nutritious  conduits.  In  the  flat  and  short  bones  there  are  no 
arteries  of  the  first  order. 

Veins  accomi^any  the  arteries,  and  are  always  more  voluminous  than 
these ;  they  frequently  make  their  exit  by  special  and  very  large  openings 
at  those  points  where  the  sjiongy  tissue  is  abundant.  The  veins  of 
bones  sometimes  exhibit  saccular  dilatations  on  their  course.  Certain  veins 
in  the  cranial  bones  have  their  parietes  entirely  composed  of  osseous  tissue. 

Lymphatic  vessels. — The  existence  of  these  in  the  interior  of  bones 
cannot  be  affirmed. 

iVeri'cs.— These  belong  to  the  cerebro-spinal  and  ganglionic  system  of 
nerves  ;  the  latter  are  always  vaso-motory  nerves. 

Almost  constantly  a  somewhat  voluminous  nerve  enters  the  medullary 
canal  by  passing  through  the  nutritious  foramen,  and  is  distributed  to  the 
medulla.  The  compact  tissue  receives  few  nervous  filaments ;  while,  on 
the  contrary,  the  spongy  tissue  at  the  extremities  of  the  long  bones,  as  well 
as  the  short  bones,  obtains  an  abundant  supply.  Certain  short  bones,  such 
as  the  vertebrae,  are  especially  remarkable  for  the  numerous  nerves  they 
receive. 


16  GENERAL  PRINCIPLES  APPLICABLE  TO 

DEVELOPMENT    OP    BONES. 

Bones,  before  arriving  at  the  state  in  which  they  present  themselves  in 
the  adult  animal,  pass  through  several  successive  phases,  whose  study  consti- 
tutes what  is  termed  osteogeny. 

In  the  embryo,  at  a  very  early  period,  the  bones  are  composed  of  a 
mucous  material  analogous  to  that  which  enters  into  the  composition  of  all 
the  other  organs ;  this  matter  is  constituted  by  a  mass  of  what  are  called 
embryonic  culls.  At  a  later  period  they  are  impregnated  with  gelatine,  and 
nearly  all  become  harder,  white,  and  elastic,  passing  into  the  cartilaginous 
state.  Exception  must  be  made,  however,  to  the  lateral  and  anterior  parietes 
of  the  cranium  and  the  face,  the  bones  of  which  are  at  first  fibrous  but 
never  cartilaginous.  The  cartilaginous  bones  show  a  fundamental  amorphous 
substance,  in  which  are  disseminated  spherical  cells  containing  one  or  more 
nuclei.  This  condition  is  transitory ;  the  cartilaginous  tissue  soon  submits 
to  modifications  which  result  in  conferring  on  the  pieces  that  it  composes 
the  hardness  and  structure  of  perfect  osseous  tissue.  These  modifications 
constitute  the  process  of  ossification.  There  are  several  portions  of  the 
skeleton  which  do  not  undergo  this  osseous  transformation,  and  which 
most  frequently  remain  in  the  cartilaginous  condition  during  the  entire  life 
of  the  animal.  These  permanent  cartilages  are  met  with  at  those  points 
where  the  bony  skeleton  must  preserve  a  certain  degree  of  flexibility, 
and  on  the  articular  surfaces.  During  the  process  of  ossification,  the 
cartilages  become  vascular,  are  impregnated  with  calcareous  salts,  and 
excavated  with  Haversian  canaliculi  and  medullary  cavities.  The  saline 
molecules  are  deposited  in  the  amorphous  substance,  which  grows  more 
hard  and  opaque  ;  at  the  same  time  the  cartilaginous  cells  become  the  point  of 
departure  of  a  new  embryonic  proliferation,  from  which  results  the  neoplasts. 

Ossification  begins  at  the  same  time  in  several  parts  of  the  skeleton,  and 
in  each  of  the  bones  in  particular ;  though  it  does  not  appear  over  the 
whole  extent  of  the  latter  at  once ;  on  the  contrary,  in  certain  determinate 
points  of  the  cartilaginous  mass,  bony  tissue  can  be  perceived  developing 
itself  and  extending  gradually  until  it  finishes  by  completely  invading  it. 
These  points  are  called  centres  of  ossification. 

These  centres  are  primary  or  complementary ;  the  latter  are  in  some  way 
added  to  the  bone,  and  form,  wholly  or  in  part,  certain  processes.  Although 
these  centres  of  ossification  enlarge  from  day  to  day,  yet  for  a  somewhat 
long  period  they  remain  completely  independent  of  one  another,  and  are  only 
connected  by  cartilaginous  tissue. 

The  term  epnphyses  is  given  to  the  osseous  centres  which  are  placed  at 
the  extremities  of  the  principal  centre.  When  the  skeleton  is  completely 
developed,  the  various  centres  of  ossification  are  fused  into  each  other,  and 
then  there  are  no  longer  epiphyses  ;  this  fusion  always  takes  place  at  an  almost 
determinate  epoch.  It  has  been  remarked  that,  of  two  epiphyses,  it  is  con- 
stantly the  one  near  which  the  nutritious  foramen  is  directed  that  is  first 
united  to  the  body  of  the  bone. 

Growth. — Bones  grow  in  width  and  thickness  by  the  apposition  of  new 
elements.  In  the  long  bones,  the  growth  in  length  takes  place  by  the 
ossification  of  the  cartilage  uniting  the  epiphyses  to  the  body  of  the  bone. 
Consequently,  elongation  should  cease  as  soon  as  the  epiphyses  are  incor- 
porated with  the  diaj)hysis.  With  regard  to  the  long  bones  of  the  limbs, 
Duhamel,  Floureus,  and  particularly  MM.  Oilier  and  Humi^hry,  have 
remarked  that,  in  the  thoracic  limb,  the  extremity  furthest  removed  from 


THE  STUDY  OF  TEE  BONES. 


17 


the  hiimero-radial  articulation  grows  fastest ;  while  in  the  abdominal  limb, 
the  extremity  most  distant  from  the  femoro-tibial  articulation  grows  the  least. 
Concerning  the  growth  of  the  bones  in  thickness,  this  occurs  by  the  ossifi- 
cation of  the  devY>  layer  of  the  periosteum  called  the  osteogenetic  layer.  The 
experiments  of  the  above-named  authors  have  irrefutably  demonstrated  this 
fact.  The  formation  of  bony  tissue  in  the  deep  layer  of  the  periosteum  is  very 
active  during  the  youth  of  animals ;  but  it  soon  slackens,  and  in  advanced 
age  ceases  completely.  In  the  first  period  of  life,  in  proportion  as  the  new 
layers  are  added  to  the  surface  of  the  bone,  the  old  layers,  those  nearest  the 
medullary  canal,  disappear  by  resorption.  Later,  the  process  of  resorption 
exceeds  that  of  formation,  which  is,  in  old  age,  completely  annihilated.  It 
has  also  been  observed  that  the  formation  of  a  certain  quantity  of  the 
osseous  elements  takes  place  on  the  inner  face  of  the  medullary  canal,  at  the 
expense  of  the  medullary  tissue.  In  the  flat  bones,  the  primitive  centre  of 
ossification  is  developed  nearly  in  the  middle,  and  the  calcareous  salts  are 
afterwards  deposited  in  radiating  lines  from  this  sjjot  towards  the  perijihery. 
These  bones  are  augmented  in  thickness  by  the  formation  of  subperiostic 

layers,  and  by  the  development  of  the  spongy  tissue  between  their  two 

compact  laminas ;    they  increase  in  width  by  the  ossification  of  what  are 

termed  the  marginal  epiphyses. 

The  short  bones  grow  from  the  periosteum 

and  the  epiphysery  cartilages,  when  they  possess 

complementary  centres. 

Nutrition. — The  exj^eriments  which  consisted 

in   feeding   young    animals   with   madder,  and 

afterwards  examining  their  osseous  system,  have 

for  a  long  period  demonstrated  the  nutrition  of 

bones.     When  bones  cease  to  grow,  their  nutri- 
tion becomes  less  active ;  but  it  is  evident  that 

it  does   go  on,  in  order  to  maintain  the  organic 

matter  of  the  osseous  tissue  in   a  proper  con- 
dition. 

(Professor  Owen  has  explicitly  and  concisely 

stated  the  development  of  bone  to  occur  as  fol- 
lows : — "  The  primitive  basis,  or  '  blastema '  of 

bone  is  a  transparent  glairy  matter  containing 

numerous  minute  corpuscles.     It  progressively 

acquires  increased  firmness  ;  sometimes  assuming 

a  membranous  or  ligamentous  state,  usually  a 

gristly  consistence,  before   its  conversion   into 

bone.     The  change  into  cartilage  is  noted  by 

the  appearance  of  minute  nucleated  cells,  which 

increase  in  number  and  size,  and  are  aggregated 

in   rows,  with    intercellular   tracts,  where   the 

ossification  is  about  to  begin,  as  in  fig.  9, 

These   rows,  in   the   cartilaginous  basis  of 

long  bones,  are  vertical  to  its  ends ;  in  that   of 

flat  bones  they  are  vertical  to  the  margin.     The 

cells  furthest  from  the  seat  of  ossification  are 

flattened  and  in  close  contact ;  nearest  that  seat 

they  become  enlarged  and  separated. 

The  first  appearance  of  bone  is  that  of  minute  granules  in  the  inter- 
columnar  and  intercellular  tissue.     Canals  are  next  formed  in  tlie  bone  by 


CARTILAGE     AT     THE     SEAT     OF 

OSSIFICATION,  showing  at  its 
lower  portions  the  clusters 
of  cells  arranged  in  columns, 
each  of  which  is  inclosed  in  a 
sheath  of  calcified  intercellular 
substance. 


18  THE  BONES 

absorption,  which  ultimately  receive  bloodvessels,  and  become  the  *  vascular 
canals.'  The  immediate  nutrition  of  bone  is  i)rovided  for  by  the  production 
of  minute  '  plasmatic  canals '  from  the  vascular  ones.  When  these  canals 
become  dilated,  so  as  to  oifer  definite  forms,  they  are  termed  '  lacuna} '  or 
'  bone-cells,'  and  to  some  extent  characterise,  by  their  shape  and  size,  the 
osseous  tissue  of  the  respective  vertebrate  classes.  lu  the  concentric 
laminae  sm-rounding  the  vascular  canal,  the  bone-cells  or  osteoplasts  are 
arranged  concentrically,  between  the  laminae,  with  the  long  axis  in  the 
direction  of  the  circular  line  of  the  plate.  Most  of  the  plasmatic  tubes  con- 
tinued from  the  bone-cells  pierce  the  plates  at  right  angles  in  their  course 
to  the  vascular  canal,  with  which  they  connnuuicate ;  and  they  form  the 
essential  vehicle  of  the  material  for  future  growth.  Extension  of  parts, 
however,  is  not  the  sole  process  which  takes  place  in  the  growth  of  bone ; 
to  adapt  it  to  its  destined  offices,  changes  are  wrought  in  it  by  the  removal 
of  parts  previously  formed.  In  marine  creatures,  the  bones  usually  remain 
solid ;  but  in  the  active  land  quadrupeds,  the  shaft  of  the  long  bones  is 
hollow,  the  first-formed  osseous  substance  being  absorbed,  as  new  bone  is  being 
deposited  without.  The  strength  and  lightness  of  the  limb-bones  are  thus 
increased  after  the  well-known  principle  of  the  hollow  column.  The  bones 
of  birds  i^resent  this  quality  in  the  highest  degree,  particularly  those  of 
powerful  flight.  In  these  the  medullary  cavity  of  beasts  is  transformed  into  a 
capacious  cavity  containing  rarified  air  instead  of  marrow.  In  the  mam- 
malian class,  the  air-cells  of  bone  are  confined  to  the  head,  and  are  filled 
from  the  cavities  of  the  nose  or  ear,  not  from  the  lungs,  as  in  birds.  Such 
cells  are  called  '  frontal  sinuses,'  '  antrum,'  '  sphenoidal,'  and  '  ethmoidal.' 
The  frontal  sinuses  extend  backward  over  the  top  of  the  skull  in  the  rumi- 
nant and  some  other  quadrupeds,  and  penetrate  the  cores  of  the  horns  in 
oxen,  sheep,  and  cei'tain  antelopes.  The  most  remarkable  development  of 
cranial  air-cells  is  presented  by  the  elephant,  the  intellectual  jihysiognomy 
of  this  large  quadruped  being  caused,  as  in  the  owl,  not  by  the  actual 
capacity  of  the  brain-case,  but  by  the  vast  extent  of  the  pneumatic  cellular 
structure  between  the  outer  and  inner  plates  of  the  skull-wall.  All  these 
varied  changes  in  the  osseous  tissue,  from  mere  cancelli  to  large  medullary 
or  pneumatic  cavities,  are  the  residt  of  secondary  changes  by  absorption, 
and  not  of  the  primitive  constitution  of  bones,  which  were  at  first  solid.") 


CHAPTEE  II. 

THE  BONES   OF    MAMMALIA   IN   PARTICULAR. 

Article  I. — ^Vertebral  Column. 

The  vertebral  column,  or  spine,  is  a  solid  and  flexible  stalk  situated  in  the 
middle  and  upper  part  of  the  trunk,  of  which  it  forms  the  essential  portion. 
It  protects  the  S2)iual  cord  and  sustains  the  thorax,  as  well  as  the  principal 
organs  of  the  circulation,  respiration,  and  digestion.  Articulated  anteriorly 
with  the  head,  and  terminating  in  a  point  at  its  posterior  extremity,  this 
piece  is  formed  by  a  somewhat  considerable  assemblage  of  short,  single, 
tuberous  bones,  to  which  has   been  given  the  name  of  vertehree.      These 


TUE  VERTEBRAL  COLUMN.  19 

bones,  though  all  constructed  on  an  uniform  type,  yet  do  not  offer  the  same 
configuration  throughout  the  whole  rachidean  stalk.  The  differences  they 
present  into  this  respect,  have  allowed  of  their  being  formed  into  five  prin- 
cipal groups ;  whence  the  division  of  the  vertebral  column  in  five  regions, 
which  are,  enumerating  them  from  before  to  behind:  1,  Cervical  region; 
2,  Dorsal  region  ;  3,  Lumbar  region  ;  4,  Sacral  region  ;  5,  Coccygeal  region. 
The  first  comprises  seven  vertebrae,  which  serve  as  a  base  for  the  animal's 
neck  :  the  second  has  eighteen,  against  which  the  ribs  are  placed  ;  the  third 
has  only  six,  which  correspond  to  the  loins  ;  in  the  fourth  there  arc  five, 
constantly  solidified  into  one  mass  in  the  adult,  to  constitute  a  single  bone — 
the  sacrum  ;  while  the  fifth  possesses  a  variable  number  of  small  degenerate 
vertebrae,  gradually  decreasing  in  size  to  form  the  tail.  The  pieces  consti- 
tuting the  first  three  regions  are  called  true  vertebras  ;  those  of  the  last  two 
are  designated  false  vertehrse. 

The  characters  belonging  to  all  these  verteorae  will  be  first  studied ;  then 
a  particular  description  of  the  vertebne  of  each  region  will  be  given ;  and, 
finally,  an  examination  will  be  made  of  the  spine  as  a  whole. 

,  CHARACTERS    COMMON    TO    ALL   THE    VERTEBRA. 

Each  of  these  small  bones  is  pierced  from  before  to  behind  by  a  wide 

Figr.  10. 


ELEMENTS   OF   A   VERTEBRA:    AFTER   OWEN. 

A,  Ideal  typical  vertebra ;  B,  Actual  thoracic  vertebra  of  a  bird ;  c,  Centrum  (or 
6oc?.v),  giving  off,  d,  d,  the  diapophyses,  and  p,  2^,  the  parapophyses  (transverse  and 
articular  processes);  the  neural  arch,  inclosing  the  spinal  cord,  is  tbrmed  by 
n,  n,  the  neurapophyses  {lamiiuv),  and  n,  s,  the  neural  spine  Cspinous  j^roccss); 
the  hamal  arch,  inclosing  the  great  centres  of  the  circulation,  is  formed  by  h,  h, 
the  hsemapophyses  (costal  cartilages),  and  h,  s,  the  ha;mal  spine  (sternum). 
From  both  the  neurapophyses  and  htemapophyses  maybe  given  off  the  zygapophyses, 
z,  z.  The  lateral  arches,  which  may  inclose  the  vertebral  arteries,  o,  o,  are 
completed  by  the  pleurapophyses  (ribs),  pi. ;  these  in  B  are  bent  downwards,  so 
as  to  form  part  of  the  hasmal  arch,  and  give  off  the  diverging  appendages,  a,  a. 

opening,  the  spinal  foramen  ;  whence  results,  for  the  entire  spine,  a  long 
canal   traversing  its  whole   length,   and   which  lodges  a  very   important 


20  THE  BONES. 

portion  of  the  nervous  centres — the  spinal  marrow.  This  canal,  which 
traverses  the  vertebra  from  one  end  to  the  other,  transforms  it  into  a 
veritable  ring  in  which  we  recognise,  for  facility  of  description,  two  parts — 
the  one  inferior,  the  other  superior.  The  first,  or  body,  is  very  thick,  and 
forms  the  base  of  the  vertebra ;  the  second,  which  is  thin,  has  been  de- 
signated spinous  or  spinal,  from  one  of  the  peculiarities  it  jiresents,  or  annular, 
because  it  circumscribes  the  major  portion  of  the  spinal  foramen.  This 
division  is  not  altogether  an  arbitrary  (me,  for  the  body  and  the  annular  por- 
tion constitute,  in  the  foetus,  two  distinct  i)ieces,  which  do  not  become 
united  for  a  long  time  after  birth. 

Body, — The  shape  of  the  body  of  a  vertebra  is  that  of  a  prism  with  four 
faces,  of  which  two  only — the  superior  and  inferior — are  free,  and  can  be 
studied  in  the  adult ;  the  two  lateral  faces  being  united  and  confounded 
with  the  annular  portion.  This  prism  also  presents  two  extremities — an 
anterior  and  posterior. 

Faces.  — The  superior  face,  limited  in  extent,  forms  part  of  the  spinal 
foramen,  constituting  its  flour.  It  exhibits :  1,  On  the  median  line,  two 
roughened,  prominent  surfaces,  rejsresenting  two  triangles,  whose  summits 
are  opposed ;  2,  On  the  sides,  two  depressed  smooth  surfaces,  perforated  by 
one  or  more  openings  that  lead  to  the  interior  of  the  bone.  The  inferior 
face  is  divided  into  two  lateral  portions  by  a  median  crest. 

Extremities. —  The  anterior  has  a  prominent  convex  head,  more  or  less 
detached.  The  posterior  offers  a  cavity  for  the  reception  of  the  head  of  the 
next  vertebra.  These  two  planes,  the  one  convex,  the  other  concave,  do  not 
come  into  immediate  contact ;  an  elastic,  flexible  fibro-cartilage,  firmly 
attached  to  each,  being  interposed  between  them. 

Annular  Portion. — This  is  formed  by  an  osseous  plate  that  curves  sud- 
denly downwards,  in  the  shape  of  an  arch,  the  two  extremities  of  which 
approach  each  other,  inclose  the  body,  and  become  united  to  it.  It  offers 
for  study :  1,  An  internal  and  an  external  surface ;  2,  An  anterior  and  a 
posterior  border. 

Surfaces. — The  internal  surface,  concave  and  smooth,  forms,  with  the 
superior  face  of  the  body,  the  spinal  foramen.  The  external,  convex  and 
irregular,  presents;  1,  A  single  prominence,  raised  in  the  middle  of  the 
superior  portion,  and  named  the  spinous  p>'>'ocess ;  2,  The  transverse  processes 
are  a  double  pair  of  eminences,  one  on  each  side,  and  projected  transversely 
outwards. 

Borders. — The  anterior  harder  has  two  articular  facets  looking  upwards : 
these  are  the  anterior  articular  processes,  right  and  left.  In  each  is  a  notch 
which,  when  placed  in  opposition  to  a  similar  excavation  in  the  preceding 
vertebra,  forms  the  intervertebral  foramen.  The  posterior  border  presents  the 
same  peculiarities,  with  this  difference,  that  the  articular  faces  of  the  pos- 
terior articular  processes  are  inclined  downwards,  to  correspond  with  the 
anterior  facets  of  the  succeeding  vertebra. 

Structure  of  the  vertehrce. — The  compact  substance,  which  is  abundant  in 
the  spinous  portion,  forms,  in  the  body,  an  extremely  thin  layer,  inclosing 
a  voluminous  nucleus  of  spongy  tissue.  The  latter  is  traversed  by  numerous 
venous  canals,  which  open  on  the  surface  of  the  bone. 

Development. — It  has  been  already  shown  that  the  body  and  spinous 
portion  of  a  vertebra  constitute,  in  young  animals,  two  distinct  pieces.  Each 
was  primarily  formed  from  two  lateral  centres,  which  met  on  the  median  line. 
In  the  body,  the  fusion  of  these  centres  is  so  prompt,  that  it  is  generally 
believed,  perhaps  justly,  that  the  develojiment  of  this  part  of  the  vertebra 


THE  VERTEBRAL  COLUMN.  21 

proceeds  from  a  single  centre  of  ossification.  The  union  of  the  tv\-o  centres 
iu  the  anuuhu"  portion,  usually  designated  the  vertebral  lamince,  is  slower. 
It  commences  iu  the  most  anterior  vertebrje,  and  is  latest  in  the  sacral  and 
coccygeal  regions.  To  the  two  principal  pieces  of  the  vertebra  in  process  of 
ossification,  is  added,  at  a  subsequent  period,  complementary  points  of  ossifi- 
cation, five  or  six  iu  number :  one  or  two  for  the  sjunous  process,  one  for  the 
summit  of  each  transverse  process,  another  for  the  head,  and  the  last  for  the 
posterior  cavity  of  the  body. 


CHAEACTERS  TKOPEU  TO  THE  VERTEBRA  OF  EACH  EEGIOX. 

A  casual  inspection  of  a  vertebra  might  suffice,  strictly  speaking,  to  dis- 
tinguish the  region  of  the  spine  to  which  it  belonged.  For  instance,  a 
cervical  vertebra  is  recognised  by  its  volume,  the  absence  of  a  spinous 
process,  and  the  foramen  which  traverses  the  base  of  its  transverse  processes. 
The  dorsal  vertebra  is  conspicuous  by  its  tubercular  transverse  processes, 
and  by  being  furnished,  outwardly,  with  an  articular  surface,  as  well  as 
by  the  defu-ession  on  its  body  destined  to  receive  the  heads  of  the  ribs.  The 
lumbar  vertebra  has  its  long  flattened  transverse  processes ;  while  the 
coccygeal  vertebra  oflFers  rudimentary  laminte  and  processes.  There  is  no 
necessity  for  noticing  the  sacrum,  whose  five  pieces  form  one  bone :  a  feature 
which  markedly  distinguishes  it  from  the  other  regions  of  the  vertebral 
column.  But  these  few  distinctive  characteristics  do  not  satisfy  the  require- 
ments of  descriptive  anatomy ;  so  that  it  is  necessary  to  undertake  a  more 
extensive  study  of  each  of  these  regions. 

1.  Cerdcal  Vertehrce. 

General  Characters. — These  vertebrse,  the  longest  and  thickest  in  the 
spine,  present  generally  a  cubic  form.  They  are  usually  distinguished  from 
the  vertebrfe  of  the  other  regions  by  the  following  characters : — The 
inferior  spine  of  the  body  is  strongly  marked,  especially  behind,  where  it 
terminates  in  a  small  tubercle.  The  head  is  well  detached  from  the  re- 
mainder of  the  bone,  and  describes  a  very  short  curve.  The  posterior  cavity, 
wide  and  deep,  represents  a  veritable  cotyloid  depression,  which  is  too 
large  to  fit  the  head  exactly :  the  intermediate  fibro-cartilage  on  these  two 
suiiaees  is  also  of  a  groat  thickness.  The  spinous  process  forms  a  simple 
roughened,  and  but  slightly  prominent,  ridge.  The  transverse  p-ocesses,  very 
developed,  are  elongated  in  an  antero-posterior  direction,  and  inclined  down- 
wards. In  this  region  they  are  designated  the  trachelian  processes,  because 
of  their  relations  with  the  trachea ;  a  foramen  that  traverses  them  from 
before  to  behind  at  their  base  has  been,  for  the  same  reason,  named  the 
iraclielian  foramen  (vertebral  foramen).  The  articular  processes,  large  and 
prominent,  are  inclined  downwards  and  inwards.  The  notches  are  wide  and 
deep. 

Specific  Characters. — The  seven  cervical  vertebraB  are  reckoned  from 
before  to  behind,  and  receive  numerical  names  indicating  their  place  in  the 
region. 

First. — The  first  vertebra  of  the  neck,  which  has  been  named  the  atlas,''- 
deserves  a  very  careful  description.     At  first  sight  there  is  recognised  the 

'  So  named  from  the  mythological  personage  who  was  supposed  to  support  the  earth, 
as  the  first  vertebra  (human)  supports  the  head.    (For  this  bone  in  the  domesticated 
animals  the  name  is  not  appropriate.) 
5 


29 


THE  BONES. 


Yiz.  11. 


great  development  of  its  transversal  diameter,  the  considerable  dimensions 
of  the  spinal  foramen,  and  the  thinness  of  its  body.  The  intra-rachidian 
face  of  the  latter  is  divided  into  two  portions  by  a  transverse  ridge ;  one 
anterior,  furnished  with  ligamentous  imprints,  exhibits,  laterally,  two  deep 
excavations,  which  lodge  the  venous  sinuses ;  the  other,  posterior,  is  smooth 
and  concave  from  side  to  side,  and  forms  an  articular  surface  into  which 
is  received  the  odontoid  j)rocess  of  the  axis ;   this  surface  resembles  the 

cotyloid  cavity.  The  inferior  spine  of  the 
body  appears  as  a  large  tubercle.  The  head 
is  absent,  and  is  replaced  by  two  concave 
facets.  The  anterior  articular  processes  have 
their  gliding  surfaces  looking  downwards ; 
they  are  joined  to  the  two  preceding  facets 
to  constitute  two  large  diarthrodial  cavities, 
which  correspond  to  the  occii)ital  condyles. 
There  is  no  spinous  process,  but  a  rough- 
ened surface  instead.  The  transverse  jiro- 
cesses  are  large,  flattened  above  and  below, 
incline  forwards  and  downwards,  and  are 
provided  with  a  thick  rugged  lip.  Pos- 
teriorly, quite  at  their  base,  and  on  each  side 
of  the  spinal  foramen,  they  show  two  large 
vertical  facets  wliich  rej^resent  the  posterior 
4,  Posterior,  or  cervical  fora-  a^-ticular  processes  :  these  facets  are  uneven, 
are  confounded  with  the  articular  cavity  oi 
the  upper  face  of  the  body,  and  correspond 
to  the  two  analogous  facets  of  the  axis. 
Each  transverse  i)rocess  is  pierced  at  its 
base  by  two  foramina,  which  traverse  it 
from  below  upwards.  The  posterior  rejn-e- 
sents  the  vertebral  foramen  of  the  other  ver- 
tebra ;  while  the  anterior  is  continued  to  the 
external  surface  of  the  process  by  a  wide, 
deep,  but  very  short  channel,  running  from 
without  to  within,  and  joins  a  third  fora- 
men, which  enters  the  spinal  canal.  These 
last  two  ojienings,  with  the  demi-canal 
which  unites  them,  rejilace  the  anterior 
notch ;  the  posterior  is  altogether  absent. 
Lastly,  an  inflected  venous  canal,  whose 
position  varies,  and  whose  presence  is  not 
constant,  crosses  the  lamina)  of  the  atlas, 
and  opens,  on  one  side,  into  the  spinal 
canal,  and  on  the  other,  beneath  the  trans- 
verse process.  The  atlas  contains  much 
compact  tissue,  and  is  generally  developed 
two  for  the  body,  which  at  an  early  period 
becomes  a  solid  piece,  and  two  for  the  annular  part ;  the  other  two  are 
complemientary  centres,  each  of  which  forms  one  of  the  two  posterior 
undulated  facets,  and  the  lip  of  the  corresponding  transverse  process. 

Second. — This  is  named  the  axis  (or  dentafa).  It  is  the  longest  of  all  the 
cervical  vertebrfe ;  those  which  succeed  it  gradually  diminish  in  length  and 
augment  in  thickness.     The  body  of  the  axis  has  not  any  head  anteriorly, 


ATLAS;  INFERIOR  SURFACE. 

1,  Articular  processes  for  condyles  of 
the  occipital  bone  ;  2,  ibidem  ;  3, 
Vertebral  or  antero-internal  fora- 
men 

men ;  5,  Transverse  process ;  6 
Tubercle  representing  the  inferior 
spinous  process ;  7,  Superior  arch, 
forming  the  roof  of  the  spinal  fora- 
men. 

Fig.  12. 


A   CERVICAL    VERTEBRA. 

1,  Superior  spinous  process;  2,  An- 
terior articular  processes  ;  3,  Pos- 
terior articular  processes ;  5,  An- 
terior convex  fiice  of  body ,  6,  7, 
Transverse  processes,  with  their 
tubercles  or  rudimentary  ribs ;  8, 
Inferior  crest,  or  spine  ;  9,  Concave 
posterior  face. 

from  six  centres  of  ossification 


THE  VERTEBRAL  COLUMN. 


23 


Fig.  13. 


but  a  conical  process  termed  the  odontoid,  wliicli  is  flattened  above  and  below, 
concave  and  rough  from  one  side  to  the  other  on  its  superior  face  ;  convex 
in  the  same  direction,  and  perfectly  smooth  on  its  inferior  face.  The  latter 
represents  an  articular  half-hinge, 
around  \vhich  glides  the  concave  arti- 
cular surface  on  the  sujierior  face  of 
the  body  of  the  atlas.  The  anterior 
articular  processes  are  carried  to  the 
base  and  to  each  side  of  the  odon- 
toidian  pivot,  in  the  shape  of  two  un- 
dulated facets,  which  are  confounded 
with  the  gliding  surface  of  the  latter, 
whose  destination  has  been  already 
noted.  The  spinous  process,  very 
powerful  and  elongated  antero-pos- 
teriorly,  is  divided  behind  into  two 
roughened  lijjs 


THE  AXIS,  OR  dentata;  lateral  view. 
i  ne  transverse  pro-  j^  Superior  spinous  process ;  2,  Odontoid  pro- 


cesses are  slightly  developed,  and  ter 
minate  posteriorly  in  a  single  tubercle, 
directed  backwards.  The  anterior 
notches  are  very  deep,  and  are  most 
frequently  converted  into  foramina, 


cess;  3,  Intervertebral  foramen,  or  hole  of 
conjugation ;  4,  Body ;  5,  Inferior  spinous 
process ;  6,  7,  Inferior  and  superior  articu- 
lating processes. 

This  vertebra,  although  voluminous, 


IS  light,  in  consequence  of  its  containing  much  spongy  substance.  In  the 
young  animal,  the  odontoid  process  and  the  articular  surfaces  on  each  side, 
constitute  two  centres,  distinct  from  each  other  and  from  the  body  of  the 
vertebra.  After  the  axis,  the  cervical  vertebrae  diminish  in  length  and 
increase  in  thickness  ;  while  the  obliquity  of  their  articular  processes  becomes 
the  more  pronounced  the  more  distant  they  are  from  that  vertebra. 

Third,  fourth,  and  fifth. — Each  of  these  has,  at  its  transverse  processes, 
two  prolongations,  one  anterior,  the  other  posterior.  The  inferior  face  of  their 
bodies  exhibits  a  median  spine  terminated  posteriorly  by  a  tubercle,  which 
gradually  increases  in  volume  from  the  third  to  the  fifth  vertebra. 

The  third  presents,  between  its  anterior  and  j^osterior  articular  j^rocesses 
an  almost  comjilete  gap  ;  if  its  anterior  extremity  be  jilaced  on  a  horizontal 
plane,  it  will  touch  that  plane  by  its  articular  and  transverse  processes  and 
its  head.  In  the  fourth,  the  articular  processes  are  united  by  a  thin,  shar]) 
osseous  plate,  notched  only  in  front.  Laid  on  a  horizontal  plane,  the  head 
remains  some  distance  from  it.  The  fifth  is  known  by  the  continuous,  thick, 
and  rugged  lamina  which  unites  the  articular  processes,  and  by  the  tubercle 
of  the  inferior  sj)ine  on  the  body,  which  is  in  shape  like  the  heart  on  a 
playing-card. 

Si.ith. — This  is  distinguished  by  the  slight  prominence  of  the  spinous 
process,  but  particularly  by  the  almost  total  disappearance  of  the  inferior 
spine,  and  the  presence  of  a  third  prolongation,  very  strong  and  inclining 
downwards  at  its  transverse  jjrocess,  a  circumstance  to  which  this  vertebra 
owes  its  designation  of  tricuspid. 

Seventh. — This  has  received  the  name  of  prominens,  because  its  spinous 
process,  terminating  in  a  point,  is  more  distinct  than  in  the  preceding 
vertebrae,  the  axis  excepted.  It  exhibits,  besides .  deep  imprints,  which 
replace  the  inferior  spine,  a  concave  demi-facet  on  each  side  of  the  posterior 
cavity  for  the  articulation  of  the  head  of  the  first  rib ;  a  particular  disposition 
of  its  transverse  processes,  which  are  unituberculous  ;  the  complete  absence  of 
the  vertebral  foramen;    and,  lastly,  the  depth  and  width  of  its  notches. 


24 


THE  BONES. 


The  spinal  foramen,  whicli  lias  already  assumed  a  somewhat  considerable 
diameter  in  the  sixth  cervical  vertebra,  is  still  larger  in  the  seventh.^ 


Fisj.  14. 


2. — Dorsal  VertehrcB. 

General  Characters. — In  the  dorsal  vertebrae  the  body  is  very  short, 
and  in  front  has  a  large  slightly  i)rojecting  head ;  behind,  it  has  a  shallow 
cavity.  Laterally,  these  vertebrae  present,  at  the  base  of  the  transverse 
processes,  fonr  concave  articular  facets,  the  two  anterior  of  which  are 
situated  near  the  head,  while  the  posterior  two  are  hollow^ed  out  of  the 
border  of  the  articular  cavity  of  the  body.     Each  of  these  facets  is  joined  to 

an  analogous  facet  on  the  neighbouring  ver- 
tebra to  form  a  small  excavation,  into  which 
is  received  the  head  of  the  corresponding 
rib.  The  spinous  process  is  very  high,  is 
compressed  on  both  sides,  inclines  backwards, 
and  its  summit  is  terminated  by  a  tubercle. 
The  transverse  pi-ocesses  are  unitubcrcular, 
and  directed  obliquely  outwards  and  up- 
wards ;  on  their  external  aspect  they  have  a 
diarthrodial  plane  facet  which  corresponds 
to  the  tuberosity  of  the  rib.  The  articular 
jrrocesses  are  narrow,  and  constitute  simple 
unrelieved  facets  cut  on  the  base  of  the 
spinous  pi'ocess.  The  posterior  notches  are 
deep,  and  sometimes  converted  into  foramina. 
Specific  Characters.  —  None  of  the 
eighteen  dorsal  vertebra)  diifer  mucli  from 
the  type  just  described ;  and  it  is  diiScult 
to  establish  special  characters  for  each. 
It  is,  nevertheless,  possible  to  assign  to  a 
dorsal  vertebra,  approximately,  the  rank  it 
should  occujiy,  in  accepting  the  following 
facts  as  a  guide : — 1.  The  vertical  diameter 
of  the  vertebral  hodies  augments  progi-es- 
sively  from  before  to  behind.  Their  lateral 
diameter,  which  determines  that  of  the  sjiinal 
canal,  becomes,  on  the  contrary,  less  from  tlie 


TYPE   OF   A   DORSAL   VEBiXEBKA ; 
THE   FOURTH. 

1,  Body ;  2,  2,  Articular  facets  for  the 
head  of  rib ;  3,  Articular  facet  for 
tuberosity  of  the  rib  ;  4,  Articular 
processes ;  5,  Spiual  foramen ;  6, 
Tuberous  base   of  spinous  process  ; 

7,  Posterior  articular  face  of  body  ; 

8,  8,  Transverse  processes ;  9, 
Superior  spinous  process;  10,  An- 
terior articulation  of  body. 


first  to  the  tenth  vertebra ;  after  which  it 
assumes  increasing  proportions  to  the  last  one.  The  articular  surfaces,  which 
serve  for  the  mutual  contact  of  head  and  cavity,  become  larger  and  shallower 
in  proportion  as  the  vertebrae  are  more  posterior.  The  inferior  spine  on  the 
body  is  very  salient  and  tuberculous  in  the  two  first  vertebrae,  very  acute  in 
the  third  and  fourth ;  it  disappears  in  the  sixth  and  ninth,  to  re-appcar  and 
become  more  marked  from  the  tenth  to  the  last.  2.  The  intci-vertebnd  cavities, 
intended  for  the  reception  of  the  heads  of  the  ribs,  diminish  in  depth  and 
extent  from  the  first  to  the  last.  3.  The  longest  S2)! nous  process  belongs  to  the 
third,  fourth,  and  fifth  vertebrae :  those  whicli  follow  gi-adually  decrease  to 
the  eighteenth.  Their  width  diminishes  from  the  second  to  the  eighth ;  it 
afterwards  increases  in  a  progi-cssive  manner  in  the  succeeding  vertebrae ; 

•  M.  Goubaux  lias   somotimcs  met  -with  asymmetrical  cervical  vertebrae  j   certaiu 
vertebrse,  tricuspid  on  one  side,  are  only  bicuspid  or  unicuspid  on  the  opposite  side. 


TEE  VERTEBRAL  COLUMN.  25 

from  the  second  to  the  tenth  vertebra,  the  summit  of  the  si^inous  process  is 
hxrge  and  tuberculous ;  in  the  last  seven  it  is  flattened  laterally.  Their 
obliquity  is  less  marked  as  they  proceed  backwards ;  in  the  sixteenth  and 
seventeenth  vertebrse,  the  spinous  process  is  nearly  vertical ;  it  inclines 
slightly  forward  in  the  eighteenth.  Those  of  the  tenth,  eleventh,  and 
twelfth  vertebrae  are  slightly  curved  like  an  S.  4.  The  articular  p-ocesses, 
from  the  first  to  the  tenth  vertebra,  gradually  contract  and  approach  the 
median  line ;  in  the  succeeding  vertebrte  they,  on  the  contrary,  increase, 
and  become  concave  and  wider  apart  from  those  of  the  opposite  side. 
5.  The  volume  of  the  transverse  processes  and  the  size  of  their  diarthrodial 
facets  diminish  from  before  to  behind.  In  the  three  first  vertebrfe  this 
facet  is  concave ;  in  the  first  nine  the  articular  facet  looks  outwards  and 
backwards,  while  the  facet  on  the  body  looks  forwards  ;  in  the  last  the  two 
facets  are  directed  forwards.  These  two  facets  are  generally  confounded  in 
the  seventeenth  and  eigliteenth  vertebree.  The  first  dorsal  vertebra  much 
resembles  the  prominens ;  it  is  distinguished  from  it,  however,  by  the 
presence  of  four  diarthrodial  facets  on  its  extremities.  It  also  differs  from 
the  other  vertebrae  by  the  shortness  of  its  spinous  process,  which  terminates 
in  a  point ;  by  the  size  and  2:)rominence  of  its  articular  processes  ;  and  by  the 
depth  of  its  notches.  The  last  vertebra  never  has  facets  on  the  contour  of 
its  posterior  cavity.^ 


3.  Lumhar  Vertebrce. 

General  Characters. — A  little  longer  and  wider  than  the  dorsal  vertebrte, 
which  they  resemble  in  the  arrangement  of  their  bodies,  these  vertebri^  are 
characterised :  1,  By  their  short,  thin,  and  wide  spinous  processes,  which 
are  slightly  inclined  forwards,  and  are  provided  at  their  summits  with  a 
scabrous  tubercle ;  2,  By  their  largely  developed  transverse  processes, 
flattened  above  and  below,  and  directed  horizontally  outwards;-  3,  By  the 
salient  anterior  articular  processes,  hollowed  out  on  each  side,  and  provided 
externally  with  a  tubercle  for  insertion ;  4,  By  theii"  equally  prominent 
posterior  articular  processes,  rounded  in  the  form  of  a  half-hinge. 

Specific  Characters. — The  characteristics  which  may  serve  to  distinguish 
these  vertebrfe  from  one  another  are  derived  from  the  body,  and  the  spinous 
and  tranverse  processes.  1.  From  the  first  to  the  last  there  is  a  progressive 
diminution  in  tLe  vertical  diameter  of  the  bodies,  and  an  increase  in  their 
transverse  diameter.  The  inferior  spine  on  the  body  becomes  shorter  and 
wider  from  the  fii-st  to  the  last  vertebra ;  in  the  six  vertebrae  it  resembles  an 
elongated  triangle  whose  summit  is  directed  forwards.  2.  The  spinous 
processes  decrease  in  width  from  before  to  behind,  and  their  anterior 
border  becomes  more  and  more  concave ;  their  summits  are  thickened  and 
tuberculous  in  the  three  first,  and  thin  and  slo2:)ing  forward  in  the  three 
last.  3.  The  transverse  processes  are  longer  in  the  middle  vertebrae 
than  in  those  placed  before  and  behind.     The  processes  in  the  first  and 

'  In  well-formed  horses,  it  is  not  unconimon  to  find  nineteen  dorsal  vertebra?,  with  an 
equal  number  of  ribs;  though  in  these  in>tances  there  are  most  frequently  only  five 
lumbar  vertebrse.  Husson  and  Goubaux  have  sometimes  met  with  nineteen,  and  the 
normal  number  in  the  other  regions.  Sometimes  there  are  only  seventeen  dorsal 
vertebrce. 

^  It  has  been  correctly  stated  that  these  processes  are  the  representatives  of  rudi- 
mentary ribs  which  have  become  united  to  the  vertebrae.  Therefore  it  is  that  they  are 
frequently  designated  costi/orm  processes. 


26 


THE  BONES. 


second  vertebrje  iucline  slightly  backward;  in  the  third  they  are  more  up- 
right ;  and  in  the  succeeding  ones  are  directed  a  little  forward.     In  the  last 

tw'O  they  are  remarkable  for  their 
thickness  ;  in  the  tifth  an  oval-shaped 
articular  facet  is  observed  on  their 
posterior  border ;  in  the  sixth,  two 
are  present —  one  in  front,  corresjjond- 
ing  to  the  preceding,  and  one  behind, 
slightly  concave,  meeting  a  similar 
facet  on  the  sacrum.  The  fourth  and 
tifth  vertebrae  very  often  correspond, 
at  their  transverse  processes,  by 
means  of  analogous  facets.^ 

In  the  Ass,  and  sometimes  in  the 
Mule,  only  five  lumbar  vertebras  are 
found.  According  to  M.  Sanson,  this 
is  the  natural  number  in  the  Arab 
Horse.  ^ 

4.  Sacrum. 

The    sacrum   results,    as   already 
stated,    from    the    consolidation     of 
five    vertebra3.       This    single    bone 
articulates,    in    front,    with    the    last 
lumbar   vertebra ;    behind,   with    the 
first    coccygeal    bone,    and    on    the 
sides  with  the  ossa  innominata.     It 
is    triangular,    flattened    above    and 
below,   and   from   before    to   behind 
describes    a    slight    curve    up- 
wards.     It   offers   for   study   a 
superior   and    an    infei'ior  face, 
two   borders,    a  base,   a  summit, 
and  a  central  canal,  the  exten 
sion  of  the  spinal  canal. 

Faces. — The  superior  face 
presents,  on  its  middle,  the  spi- 
nous jirocesscs  of  the  sacral 
vertebra3,  which  together  con- 
stitute what  is  called  the  sacral 
or  supersacral  spine.  These 
LUMBAR  VERTEBRA  ;froxt  VIEW.  proccsscs   are   xmited    at    their 

^\^.l^'  \^?'''^'7^''*"''^^^^T''''f°r   l^ase  only,  and  remain   is.dated 
process ,  4,  Spiual  foramen ;  5,  Anterior  articular     „       ^        '' '       .     ^  i!     ^     • 

processes;    6,    6,    Transverse,    or   costiform    pro-    ^^^'   *'!«    remainder   ot    their    ex- 
cesses, 7,  Posterior  articular  process.  tent ;  they  all  incline  backwards 

'  We  possess  the  skeleton  of  a  horse  which  has  seven  lumbiir  vertebra;,  with  the 
normal  compleniont  in  the  other  regions.  The  seventli  is  no  doubt  the  first  sacral,  as  it 
has  all  its  characters.  The  fifth  sacral  vertebra  is  evidently  derived  from  the  coccygeal 
region. 

-  (This  statement  is  scarcely  correct.  M.  Sanson  has  established  tlie  fact  that  there 
is  in  reality  no  Arab  horse;  and  asserts  that  the  specific  type  with  five  lumbar  vertebra-, 
is  very  probably  of  African  origin,  and  that  these  vertebinj,  independently  of  their  numb(  r, 
offer  individual  characteristics  different  from  those  observed  in  the  vertubrte  of  the  type 
which  has  six.) 


UPPER   SURFACE   OF    LUMBAR    VERTEBRA. 

1,  Summit  of  spinous  process  j  2,  2,  Anterior 
articular  processes;  3,  3,  Posterior  articu- 
lar processes ;  4,  4,  Transverse  processes. 

Ficr.  16. 


THE  VERTEBRAL  COLUMN. 


27 


and  terminate,  witli  the  exception  of  the  first,  by  a  tuberous  summit,  which 
is  often  bifid ;  their  length  diminishes  from  the  second  to  the  fifth  bone. 
On  each  side  of  the  sacral  spine 

exists  a  groove,  at  the  bottom  t'ig.  17. 

of  which  are  foiu"  openings — the 
supersacrcd  foramina.  These 
orifices  open  into  the  spinal 
canal,  and  communicate  with 
four  analogous,  but  wider  aper- 
tures, pierced  at  the  inferior 
face  of  the  bone,  and  for  this 
reason  named  the  subsacral  fo- 
ramina. The  inferior  face  is 
smooth,  and  shows  traces  of  the 
primitive  separation  of  the  ver- 
tebral bodies  ;  the  subsacral  fo- 
ramina, which  represent,  with 
the  corresponding  supersacral 
openings,  the  intervertebral  fo- 
ramina of  ihe  other  regions  of 
the  spine,  are  observed  on  this 
surface. 

Borders. — The  two  borders,  thick  and  concave,  form,  posteriorly,  a  rugged 
lip ;  in  front,  they  present  an  irregular  sui-face  inclining  obliquely  from 
above  to  below,  from  within  outwards,  and  from  before  to  behind.  This 
surface,  which  is  intended  for  the  articulation  of  the  sacrum  with  the  ossa 
innominata,  is  divided  into  two  parts :  one,  the  inferior,  named  in  man  the 
auricular  facet,  is  slightly  imdulated  and  diarthrodial ;  the  other,  the 
superior,  serves  for  ligamentous  insertions. 

Base. — This  offers :  1,  On  the  median  line,  the  anterior  orifice  of  the 
sacral  canal,  and  the  anterior  articular  snrface  of  the  body  of  the  first  sacral 
vertebra,  which  is  oval  and  slightly  convex ;  2,  On  the  borders,  the  articular 
processes  and  anterior  notches  of  this  vertebra,  as  well  as  the  elliptical 
and  somewhat  convex  facets  which  bring  it  into  contact  with  the  transverse 
processes  of  the  last  lumbar  vertebra. 

Summit. — The  summit,  thrown  back,  presents  :  1,  The  posterior  orifice 
of  the  sacral  canal ;  2,  The  posterior  articular  surface  of  the  body  of  the 
last  sacral  vertebra ;  3,  The  vestiges  of  the  articular  processes  and  posterior 
notches  of  that  vertebra. 

Sacral  canal. — This  is  the  portion  of  the  spinal  canal  which  is 
channeled  out  of  the  sacrum ;  it  is  triangular,  and  diminishes  in  width 
from  before  to  behind. 


LATERAL   VIEW   OF   SACRUM. 

1,  Articular  surface  of  body  :  2,  3,  Articular  surfaces 
corresponding  to  those  on  the  transverse  processes 
of  last  lumbar  vertebra;  4,  Spinal  foramen;  5, 
Auricular  facet ;  6,  Anterior  articular  processes ; 
7,  Inferior  or  subsacral  foramina ;  8,  Superior 
spinous  processes ;  9,  Summit  or  coccygeal  ex- 
tremity. 


5.    Coccygeal  Vertehrce. 

The  coccygeal  region,  or  coccyx,  comprises  from  fifteen  to  eighteen  de- 
generate vertebrae,  which  gradually  diminish  from  the  first  to  the  last.  In 
the  first  three  or  foui",  nearly  all  the  characteristics  of  true  vertebrae  are 
found ;  they  show  a  spinal  foramen,  a  body,  a  spinous  process,  and 
transverse  processes,  looking  backwards ;  the  articular  processes  only  are 
altogether  absent.  In  the  succeeding  vertebrte,  these  characters  become 
effaced  ;  the  vertebral  laminfe  do  not  join  completely,  and  the  spinal  canal 
is  only  a   simjile   groove,  which,  gradually  decreasing  in   depth,    at   last 


28  TEE  BONES. 

entirely  disappears.  The  insertion  eminences  also  become  less  salient, 
and  the  coccygeal  vertebrfe  are  soon  reduced  to  small  bony  cylinders, 
narrow  in  the  middle  and  wider  at  both  extremities,  with  a  convex  articular 
surface  at  each  end  (except  the  last,  which  has  only  one  ai'ticular  surface^. 
These  small  cylinders,  the  last  traces  of  the  vertebral  bodies,  are  each 
developed  from  three  centres  of  ossification ;  they  are  very  spongy  and 
light.  The  fii'st  coccygeal  vertebra  is  frequently  consolidated  with  the 
sacrum  in  aged  animals. 


THE    SPINE    IN    GENERAL. 

The  vertebral  column  has  now  to  be  considered  in  its  entirety,  and 
examined  successively  in  its  superior  face,  its  inferior  face,  its  lat.ral  faces, 
and  its  spinal  canal.  Afterwards  its  direction  and  mobility  will  be 
noticed. 

Superior  face. — This  presents,  on  its  median  line,  the  series  of  spinous 
processes.  But  little  salient  in  the  cervical  region,  these  eminences  are 
much  developed  in  the  dorsal  and  lumbar,  where  they  constitute  a  long 
crest,  the  dorso-lumhar  spine,  as  well  as  in  the  sacrum,  where  they  form 
the  sacral  spine.  They  soon  disappear  in  the  coccyg^l  vertebrte. 
Outwards,  and  on  each  side  of  these  processes,  is  seen  a  succession  of 
tubercles  of  insertion,  represented  in  the  cervical  and  lumbar  vertebrae 
by  articular  processes,  and  in  the  dorsal  vertebrfe  by  the  superior  or  rugose 
portion  of  the  transverse  processes.  These  tubercles  are  disposed  in  line, 
and  sejxarated  from  the  spinous  processes  by  a  channel  designated  the 
vertebral  groove,  which  is  more  or  less  deep  and  wide.  It  is  on  these,  and 
on  the  spinous  processes,  that  the  extensor  muscular  fasciculi  of  the  spine 
receive  the  greater  portion  of  their  fixed  or  moveable  insertions. 

Inferior  surface. — -Wide  at  the  neck,  this  face  becomes  narrow  in  the 
dorsal  region,  to  be  again  widened  at  the  lumbo-sacral  region,  and  once 
more  contracted  at  the  coccyx.  Crests  more  or  less  developed,  which  divide 
the  vertebral  bodies  into  two  lateral  portions,  right  and  left,  are  remarked. 

Lateral  surfaces. — These  offer  for  study  the  thirty-six  intervertebral 
foramina,  through  which  the  spinal  nerves  pass.  They  exhibit  besides, 
on  the  neck,  the  transverse  processes ;  in  the  back,  the  external  facets 
of  these  processes,  and  the  intervertebral  facets,  all  destined  to  sustain 
the  heads  of  the  ribs  ;  on  the  loins,  the  transverse  or  costiform  processes. 
It  may  be  remarked  that  the  ribs  and  the  transverse  processes  of  the  neck 
and  loins  furnish  points  of  insertion  to  the  powerful  muscles  which  produce 
the  lateral  movements  of  the  spine.  In  the  sacrum,  the  lateral  faces  are 
formed  for  the  articulation  of  the  spine  with  the  ossa  innominata. 

Spinal  canal. — This  canal  communicates,  in  front,  with  the  cranial  cavity. 
Very  wide  in  the  atlas,  for  the  reception  of  the  odontoid  process  and  to  permit 
the  rotatory  movements  of  the  head  without  iujm-y  to  the  spinal  cord,  this 
canal  suddenly  diminishes  in  the  axis.  It  again  dilates  at  the  termination 
of  the  cervical  region  and  the  commencement  of  the  dorsal ;  there  the  sjnnal 
cord  presents  a  greater  volume,  and  the  movements  of  the  spine  are  very 
extensive.  Towards  the  middle  of  the  back,  the  spinal  canal  offers  its 
smallest  diameter  ;  it  Avidens  from  this  part  to  the  lumbo-sacral  articula- 
tion ;  after  which  it  contracts  rapidly,  and  disappears  altogether  near  the 
fourth  or  fifth  coccygeal  vertebra.  The  lumbo-sacral  dilatation  coincides 
with  the  enlargement  of  the  cord  in  this  region,  and  with  the  enormous 
quantity  of  nerves  lying  beside  it. 


TEE  VERTEBRAL  COLUMN. 


29 


Direction  of  the  vertebral  column. — The  spine  docs  not  extend  in  a 
straifjbt  line  from  the  head  to  the  posterior  extremity  of  the  body.  If  it 
is  foUowed  from  the  caudal  termination,  which  is  free  and  looks  downwards, 
to  the  anterior  extremity,  it  will  be  seen  that  it  rises  upwards  and  forwards, 
forming  a  convex  intlexion  corresponding  to  the  roof  of  the  pelvis.  lu 
the  lumbar  and  the  posterior  half  of  the  doi-sal  region  it  is  nearly  horizontal 
and  rectilinear ;  from  thence  it  descends  to  the  cervical  region,  when  it 
again  rises  and  forms  two  curves,  the  one  posterior,  bending  upwards,  the 
other  anterior,  turned  down.  This  disposition  of  the  cervical  spine  gives 
it  the  shape  of  a  console. 

Mobility  of  the  vertebral  column. — In  the  cervical  region,  the  almost  total 
absence  of  spinous  processes,  the  great  development  of  the  articular 
processes,  and  the  very  short  curve  described  by  the  surfaces  of  contact 
of  the  vertebral  bodies,  allows  the  spine  very  extensive  and  very  diverse 
movements.  In  the  dorsal  region,  however,  these  movements  are  very 
limited,  the  spinous  processes  and  the  costal  arches  preventing  the  play 
of  the  vertebrte  on  each  other.  In  the  lumbar  region,  the  spine  can  be 
flexed  or  extended  more  than  in  the  dorsal ;  but  its  lateral  movements  are 
quite  as  restricted,  owing  to  the  jiresence  of  the  transverse  processes  and 
the  reciprocal  joining  or  dovetailing  of  the  articular  processes.  Lateral 
motion  is  even  rendered  impossible  in  the  posterior  half  of  this  region, 
from  the  manner  in  which  the  transverse  processes  are  adapteil  to  each  other. 
It  may  be  remarked,  however,  that  this  disposition  singularly  favours  the 
integral  transmission  of  the  propulsive  efforts  thrown  ujJon  the  trxmk  by 
the  posterior  extremities. 

The  sacral  vertebrae,  having  to  afford  the  ossa  innominata  a  solid  fixed 
point,  could  not  j^reserve  their  independence  and  mobility,  and  are  conse- 
quently consolidated  into  a  single  piece  which  fulfils  all  its  requirements 
in  this  respect.  In  the  coccyx  the  rachidean  stalk  again  recovers  its 
mobility,  and  to  a  degree  more  marked  than  elsewhere  ;  the  coccygeal  bones, 
articulated  with,  each  other  by  means  of  convex  siirfaces,  and  deprived  of 
long  processes  at  their  extremities,  are  placed  in  the  best  possible  conditions 
for  variety  and  extent  of  movement. 

DrETEKENTIAL   CHARACTERS   IN   THE   VERTEBRAL   COLUMN   OF  OTHER  THAN 
SOLIPED   ANIMALS. 

The  Number  of  Pieces  composing  the  Spine  slightly  varies  in  the  Domesticated 
Animals,  as  will  be  seen  in  the  following  Table. 


ANIMALS. 


Ox    . 

Sheep 
Goat 
Pig  . 
Do- 
Cat  . 


^TERTEBR.E. 


Cervical. 


DorsaL       Lumbar.       SacraL        Coccygeal. 


13 

6 

5 

13 

6  or  7 

4 

13 

6 

4 

14 

6  or  7 

4 

13 

7 

3 

13 

7 

3 

l^to20 
16  to  24 
11  to  12 
21  to  23 
16  to  21 
21 


A.  VERTEBR.E  OP  THE  Ox,  Sheep,  AND  GoAT. — 1.  Cewical  VeHehrx. — The  cervical 
vertebrpe  of  the  Ox  diflfer  from  those  of  solipeds  by  their  shortness  and  the  greater  deve- 
lopment of  their  insertion  eminences.  In  the  Sheep  and  Goat  they  are  relatively  longer. 
than  in  the  Ox.   The  transverse  processes  of  the  atlas  are  less  inclined  than  in  the  Horse, 


30  TEE  BONES. 

and  Lave  no  vertebral  foramiua ;  the  posterior  facets  for  articulation  with  the  axis  are 
nearly  flat  and  join  each  other.  The  axis  has  a  semicylindrical,  not  a  conical,  odontoid 
process,  which  is  so  concave  on  its  upper  surface  that  it  looks  like  a  groove.  Its  spinous 
process  is  not  so  thick  as  in  the  Horse,  and  is  not  bifid  posteriorly. 

In  the  five  succeeding  vertebrx,  a  rugged  continuous  lamina  unites  the  anterior  articular 
processes  to  the  posterior.  Tiie  spinous  process  inclines  forward  and  is  flattened  trans- 
versely at  its  summit,  which  is  sometimes  bifid ;  it  augments  progressively  in  height 
from  the  third  to  the  filth  vertebra. 

In  the  sixlli,  the  transverse  processes  have  only  two  prolongations — a  superior  and 
inferior ;  the  latter,  large  and  flattened  on  botli  sides,  is  bent  abruptly  downwards.  The 
spinous  process  has  already  attained  the  height  of  IJ  to  2  inches  in  this  vertebra,  and 
is  flattened  laterally. 

The  seventh  well  deserves  the  name  of  prominens  •  its  sjainous  process  being  no  less 
than  from  i  to  -i^  inchi-s. 

2.  Dorsal  vertebra;. — In  the  Ox  these  bones  are  longer  and  thicker  than  in  the  Horse. 
Their  spinous  processes  are  larger  and  incline  more  backward  ;  their  transverse  processes 
are  very  voluminous,  and  are  provided  with  a  convex  facet  from  above  to  below;  while 
their  posterior  notches  are  nearly  always  converted  into  foramiua. 

Cousidered  individually,  they  are  more  slender  in  the  middle  than  at  the  extremities. 
Their  spinous  processes  diminish  in  width,  especially  at  their  summits,  from  the  first  to 
the  eleventh  vertebra,  and  widen  again  in  the  two  last ;  they  progressively  increase  in 
slope  to  the  teuth,  after  which  they  become  more  and  more  upright ;  the  first  four  are 
the  longest,  and  are  nearly  the  same  in  height ;  the  others  gradually  decrease. 

In  the  lirst  four  or  five  vertebraj,  the  articular  facet  of  the  transverse  processes,  while 
retaining  its  vertical  convexity,  is  concave  in  an  antero-posterior  direction.  This  facet  is 
always  absent  in  the  last  vertebra,  and  sometimes  even  in  the  preceding  one.  The  two 
bones  terminating  the  dorsal  region  show,  in  addition,  the  articular  processes  disposed 
like  those  of  the  lumbar  vertebrae. 

The  dorsal  vertebrae  of  the  Sheep  and  Goat  are  relatively  less  strong  than  those  of  the 
Ox  ;  their  spinous  processes  are  not  so  wide,  and  their  posterior  notches  are  never  con- 
verted into  tViramina. 

3.  Luiahar  vcrtehrse. — The  lumbar  vertebrae  of  the  Ox  are  longer  and  thicker  than  in 
the  Horse.  The  transverse  processes  are  also  generally  more  developed,  are  concave  on  the 
anterior  border,  convex  ou  tiie  posterior,  and  incline  slightly  downward,  with  the 
exception  of  tlie  two  fiist,  which  remain  nearly  horizontal.  They  increase  in  length  from 
the  first  to  the  fourth  vertebra;  in  the  latter  and  the  fifth,  they  are  nearly  of  tlie  tame 
dimensions ;  in  the  last  they  suddenly  become  shorter.  Their  width  gradually  decreases 
from  before  to  behind.  In  the  fifth  and  sixth  vertebra,  these  processes  have  no  articular 
fecets  between  them  and  the  sacrum,  these  being  only  met  with  in  solipeds.  The  artic- 
ular processes  are  prominent,  and  further  removed  from  the  median  line  as  they  belong 
to  posterior  vertebrae. 

In  the  G  >at  the  transverse  processes  are  more  inclined  downwards. 

In  the  Sheep,  on  the  contrary,  the  processes  rise  up  towards  their  extremities. 

4.  Sacrum. — Tiie  tacrum  of  the  Ox  is  more  voluminous  and  curved  than  that  of  the 
Horse.  The  spinous  processes  are  entirely  consolidated,  and  are  surmounted  by  a  thick 
rugged  lip ;  tkey  are  leugtheued  at  their  base  and  on  each  side  by  a  ridge  that  represents 
the  rudiments  of  the  articular  processes.  Tlie  lateral  borders  are  sharp  and  bent  down- 
wards. The  surfaces  that  serve  to  unite  the  sacrum  to  the  ossa  innorainata  have  a  some- 
what vertical  direction.  There  are  no  lateral  facets  on  the  base  of  the  bone  for  the  union 
of  tlie  sacrum  with  the  transverse  processes  of  the  last  lumbar  vertebra.  In  the  Slieej) 
and  Goat,  the  sacrum  is  shorter ;  sometimes  the  consolidation  of  the  spinous  processes  is 
late,  or  never  occurs. 

5.  Coeeyrieal  verfebrx.  — In  proportion,  the  coccygeal  vertebrae  of  ruminants  are 
stronger  and  more  kiberous  than  those  of  the  Horse.  The  anterior  articular  processes 
exist  in  a  rudimentary  condition. 

B.  Veutebu.ts  of  the  Pig. — 1.  Cervical  vertehree. — Of  all  the  domesticated  animals, 
this  has  the  shortest,  the  widest,  the  most  tuberous,  and  consequently  the  strongest  cervi- 
cal vertebrae.  The  body  of  these  bones  is  deprived  of  its  crest  ou  the  inferior  face ;  its 
held,  but  little  detached,  is  scarcely  round,  and  looks  as  if  driven  back  on  itself;  con- 
sequently, its  posterior  cavity  is  not  deep. 

The  vertebral  laminoo  are  very  narrow,  and  scarcely  extend  from  one  part  of  the 
vertebra  to  the  other  in  the  superior  portion ;  so  that  the  spinal  canal  appears  at  this 
point  to  be  incomplete. 

In  the  atlas,  the  transverse  processes  are  yet  less  inclined  than  in  ruminants ;  the 
vertebral  foramen  is  not  constant,  and  when  it  exists,  opens  on  one  side,  under  the 


THE  VERTEBRAL  COLUMN.  SI 

transverse  proces3,  and  on  the  other,  oa  its  posterior  margin,  after  pursuing  a  certain 
truck  in  the  substance  of  the  bone. 

The  odontoid  process  of  the  axis  is  constricted  at  its  base.  This  vertebra  is  distin- 
guished by  its  high  and  thin  spinous  process  inclining  slightly  back,  by  its  transverse 
processes  being  but  slightly  piouiiueut  and  perforated  by  an  enormous  vertebral 
loramen. 

in  the  four  succeeding  vtriehnv,  the  spinous  process  terminates  in  a  blunt  point,  and 
uiclincs  forward;  slightly  salient  in  the  tirst,  it  gradually  rises  in  the  others.  The  trans- 
verse processes  form  two  prolongations :  one,  tlie  superior,  is  tulj>erculous,  and  is  joined 
to  the  anterior  articular  process  by  a  plate  of  bone,  which  is  pierced  by  a  foramen;  the 
other,  the  inferior,  flattened  on  both  sides,  bent  downwards,  and  large,  as  it  belongs  to 
the  posterior  vertebra;,  transforms  the  inferior  face  of  these  vertebral  bodies  into-  a  large 
groove.  The  seventh  is  provided  with  a  spinous  process  as  long  as  those  of  the  dorsa.! 
region.  A  perforated  bony  plate,  as  in  the  preceding  vertebraj,  unites  the  anterior 
articular  process  to  the  single  tubercle  composing  the  transverse  process ;  the  latter  is 
continued  back  nearly  to  the  posterior  notch  by  a  second  plate,  also  perforated  with  a 
foramen  (see  Fig.  2j. 

2  Dorsal  vertebra;. — The  Pig  has  fourteen  dorsal  vertebrfe,  which,  in  their  general 
disposition,  are  not  unlike  those  of  the  Ox.  As  with  that  animal,  the  intervertebral  fora;- 
mina  are  double,  each  vertebral  lamina  being  perforated  laterally  by  an  opening  situated 
in  front  of  the  posterior  notch.  In  addition,  the  vertebrse  of  the  Fig  present  this  pecu- 
liarity, that  their  transverse  processes  are  generally  traversed  at  the  base  by  a  single  or 
multiple  foramen  which  communicates  with  the  jjieeeding. 

With  regard  to  the  special  characters  proper  to  some  of  the  vertebrse,  these  are,  as  witk 
the  other  animals,  very  few,  and  may  be  described  as  follows;  1.  The  transverse  pro- 
cesses of  the  four  vertebra  preceding  the  last  project  but  slightly;  2.  In  the  fourteenth 
this  process  resembles  those  of  the  lumbar  vertebrse  ;  3.  The  articular  facet  of  the  trans- 
verse process  in  the  four  last  vertebra;  is  confounded  with  the  anterior  lateral  facet 
corresponding  to  the  head  of  the  rib,  4.  The  articular  processes  of  the  last  five  vertebrse 
are  arranged  like  those  of  the  lumbar  vertebrre  ;  and  the  prominence  formed  by  the 
tubercle  on  the  outside  of  the  anterior  articular  process  replaces,  to  a  certain  degree,  the 
transverse  process  of  these  vertebrse. 

3.  Lumbar  vertehrx. — These  bones  in  the  Pig  greatly  resemble  those  of  ruminant 
animals.  It  commonly  happens  that  seven  are  met  w  ith ;  but  in  this  case  the  supple- 
mentary vertebra  is  generally  a  sacral  one.  It  is  not  denied,  however,  that  seven  lumbar 
vertebrse  may  exist  in  the  Pig,  along  witli  the  normal  num1:>er  of  sacial  vertebrae. 

4.  Sacrum. — This  is  formed  by  four  vertebrse,  which  are  a  long  time  in  becoming 
fused  together ,  and  it  is  often  dilticult  to  discover  where  the  sacrum  ends  and  the  coccyx 
begins.'  The  spinous  processes  are  entirely  absent.  The  vertebral  laminse  are  not 
consolidated  ,  so  that  the  spinal  canal  is  half  cut  through  in  its  upper  portion,  as  in  the 
cervical  region ;  this  canal  is  also  much  compressed  above  and  below. 

5.  Coccygeal  vertehrx. — These  vertebrse  in  the  Fig  are  more  particularly  distin- 
guished by  the  presence  of  articular  processes,  by  means  of  which  the  foremost  bones 
correspond  with  each  other. 

C.  Vektebr.?;  of  the  Dog  anp  Cat. — 1.  Cervical  Vertehrx. — In  these  animals,  tlie 
cervical  vertebrse  are  long  and  thick,  and  much  resemble  those  of  solipeds.  Nevertheless, 
besides  their  smaller  volume,  they  are  distinguished :  1,  By  the  disposition  of  their 
corresponding  articular  surfaces;  the  anterior,  or'head,  is  nearly  flat,  and  is  even  slightly 
excavated  in  its  centre  ;  tlie  posterior,  or  cavity,  is  but  little  hollowed  to  receive  the  head 
of  the  next  vertebra ;  2,  By  the  width  of  the  vertebral  laminse,  which  exactly  cover  one 
another ;  3,  By  the  height  of  their  spinous  processes,  which  increases  as  the  vertebriB 
extend  back ;  4,  By  the  great  extent  of  the  anterior  and  posterior  articular  processes, 
whic'.i  are  united  by  means  of  a  continuous  and  very  salient  bony  plate,  that  considerably 
augments  the  transversal  diameter  of  each  vertebra. 

In  the  atlas,  the  articular  surface  for  the  odontoid  pivot  is  confounded  in  front  with  the 
cavities  which  correspond  to  the  occipital  condyles.  The  two  facets  which  are  annexed 
l)osteriorly  to  this  articular  surface,  instead  of  being  plane  or  gently  undulated,  as  in  the 


'  This  can  always  be  made  out.  however,  by  con.sulting  the  disposition  of  the 
articular  processes.  Thus,  in  the  sacral  vertebrse  these  eminences— if  we  except  the 
anterior  ones  of  the  first  and  the.  posterior  of  the  last— never  exist  except  in  a  rudi- 
mentary state;  while  in  the  other  five  coccygeal  vertebrae  they  ro-appear  with  all  their 
characters. 


S2  THE  BONES. 

other  domesticated  animals,  are  transformed  into  real  glenoid  cavities.'  The  transverse 
processes  are  carried  directly  outwards  and  a  little  backwaid;  the  lip  which  borders 
each  is  slii^htly  raised ;  of  the  two  foramina  which  replace  the  anterior  notch,  one  only 
exists,  and  this  penetrates  to  the  interior  of  the  spinal  canal ;  the  other  is  merely  a  simple 
notch. 

In  the  axis,  the  odontoid  process  is  cylindrical,  narrow  at  its  base,  and  bent  a  little 
upwards;  the  lateral  facets  of  this  eminence  represent  true  condyles.-  The  spinous 
process  is  veiy  thin  and  undivided,  and  is  curved  forward  above  the  laminiB  of  the  atlas. 
The  anterior  notches  are  never  converted  into  foramina. 

The  tliird  cervical  vertebra  is  the  largest,  and  the  succeeding  ones  gradually 
diminish  in  thickness  to  the  last,  contrary  to  what  occm-s  in  the  other  species.  The 
seventh  does  not  show  the  spinous  process  so  developed  as  in  ruminants  and  pachyderms 
(see  Fig.  1). 

2.  Dorsal  vertehrx. — In  the  Dog  the  dorsal  vertebrse  are  formed  on  the  .same  model  as 
those  of  the  Horse ;  but  their  spinous  processes  are  in  general  narrower  and  tliicker.  The 
tenth  always  has  its  spinous  process  vertical,  triangular,  and  terminated  in  a  sharp  point. 
The  last  three  have  no  posterior  facets  for  the  articulation  of  the  heads  of  the  ribs,  and 
exhibit,  in  the  conformation  of  their  articular  processes,  the  same  disposition  as  the 
lumbar  vertebrse.  In  the  Cat,  the  transverse  processes  of  the  three  last  dorsal  vertebrae 
are  thin,  sharp,  and  turned  backwards ,  they  never  possess  facets  for  the  tuberosity  of 
the  ribs. 

3.  Lumbar  verfebrx. — In  the  Dog  and  Cat,  the  lumbar  vertebrse  are  remarkable  for 
their  strengtli,  due  to  their  length,  thickness,  and  the  development  of  the  eminences  of 
insertion.  The  spinous  process  is  low,  and  becomes  acute  in  the  last  vertebra.  The 
transverse  processes  incline  very  much  forward  and  downward  ,  they  become  longer  from 
the  first  to  the  second-last  bone,  in  the  latter  they  become  contracted,  and  in  the  seventh 
vertebra  they  are  still  more  diminished,  and  terminate  in  an  obtuse  point.  The  tubercle 
of  the  anterior  articular  process  is  extremely  promment,  and  the  posterior  notches  are 
surmounted  by  a  small,  very  acute  prolongation,  directed  backwards,  which  becomes 
more  developed  towards  the  anterior  vertebrae.  Tiiis  small  prolongation  exactly 
i-epresents  the  transverse  process  of  the  dorsal  vertebrse. 

4.  Sacrnm. — -The  three  vertebrse  which  form  tiie  sacrum  of  carnivora  are  early  con- 
solidated. The  supersacral  spine  constitutes  a  thin  siiarp  ridge,  while  the  lateral 
surfaces  for  articulation  with  the  ossa  innominata  are  turned  quite  outwards  and  are  nearly 
vertical. 

5.  Coccygeal  vertebrse. — The  vertebrse  ot  the  coccyx  are  very  strong  and  tuberous. 
The  first  five  or  six  are  as  perfect  as  the  true  vertebrae,  and  comport  themselves  in  every 
respect  like  them.  The  last  are  small  V-shaped  bones,  which  M.  Goubaux  has  described 
by  the  name  of  hypsiloid  bones. 

COMPARISON   OF  THE   VERTEBRAL   COLUMN    OF   MAN    WITH  THAT   OF   THE   DOMESTICATED 

ANIMALS. 

The  vertebral  column  of  Man  is  composed  of  twenty-nine  bones  .  twenty-four  vertebrse. 
the  sacrum,  and  four  pieces  constituting  the  coccyx.  The  twenty-four  vertebrae  arc  thus 
distributed : 

Cervical  vertebrae " 

Dorsal  „  12 

Lumbar        „  5 

In  all  these  vertebrae,  the  bodies  are  slightly  excavated  at  the  two  extremities,  while 
in  the  domesticated  animals,  the  superior  or  anterior  is  convex,  and  the  inferior  or  posterior 
concave. 

1.  Cervical  verfebr.v.— These  are  wide  and  short.  The  spinous  processes  are  mode- 
rately developed  and  bifid  at  their  summits ,  the  transverse  processes  are  also  divided 
into  two  branches — a  posterior  and  an  anterior. 

2.  Dorsal  vertebrx. — In  these  vertebrse,  the  bodies  increase  in  thickness  from  the 
first  to  the  last.  In  the  first  as  well  as  in  the  last  dorsal  vertebrse,  the  spinous  process  is 
almost  immediately  directed  backwards;  in  the  middle  portion  of  this  region  these 
processes  are  very  obliquely  directed  downwards  and  backwards. 


'  (A  glenoid  cavity  is  a  shallow,  oval,  articular  depression.) 

2  (A  condyle  is  an  articular  eminence  representing  an  ovoid  segment.     Condyles 
always  corresj^nd  to  the  glenoid  cavities  in  the  articulations.) 


TEE  HEAD. 


33 


3.  Lumhar  vertehrx. — The  lumbar  vertebrae  are  the  strongest  bones  in  the  spine, 
and  their  bodies  are  marly  as  ihick  as  those  of  the  larger  domestic.ited  animals.  This 
enormous  development  of  the  lumbar  vertebrae  in  Man  is  related  to  his  position  as  a  bipe^l. 
In  the  fifth,  the  lower  face  of  the  body  is  cut  very  oi'liijuely  backwards  and  upwards,  and 
ti.e  transverse  processes  are  more  voluminous  than  those  of  the  otlier  lumbar  vertebrae. 

4.  Sacrum. — The  sacrum  is  lormed  by  the  union 

of  five  pieces.     It  is  very  concave   from    above  to  Fig.  is. 

below  and  before  to  behind.  In  becoming  united 
to  the  lumbar  region,  it  forms  a  salient  angle  in 
front,  to  which  has  been  given  the  name  of  promon- 
tory or  sacro-vertebra]  angle.  The  sacral  spine  is 
continuous  or  interrujited,  according  to  the  subject ; 
it  is  alway  bifid  inferiorly. 

5.  Coccygeal  vertehrx. — These  are  little  bones 
or  flattened  tubercles,  four  in  number,  rarely  five, 
and  usually  consoliilated.  The  coccyx  is  conical  in 
shape.  Its  base  shows  two  processes  directed  up- 
warJs,  which  are  called  the  cornua  of  the  coccyx. 
Its  summit  is  often  deviated  to  the  right  or  left. 

Article  II. — The  Head. 

The  head  is  a  large  bony  pyramid,  elon- 
gated from  above  to  below,  and  quadran- 
gular, suspended  to  the  anterior  extremity 
of  the  spine  ;  it  is  in  a  direction  varying  with 
the  attitudes  of  the  animal,  but  which  we  will 
suppose,  for  convenience  of  description,  to 
be  nearly  vertical.  It  is  formed  of  a  great 
number  of  particular  bones,  which  are  only 
distinct  from  one  another  in  very  young 
animals  ;  for  well  before  the  adult  period  is 
reached  the  majority  of  the  bones  are  united 
and  cannot  be  separated. 

The  head  is  divided  into  two  parts  :  the 
cranium  and  the  face. 

BOXES   OF    THE    CRANimi. 

The  cranium,  or  upper  part  of  the  head, 
is  composed  of  seven  flat  bones,  five  of 
which  are  single :  the  occipital,  parietal, 
frontal,  sphenoid,  and  ethmoid ;  one  only,  the 
temporal,  is  double.  These  bones  circum- 
scribe a  central  cavity,  the  cranial,  which 
communicates  behind  with  the  spinal  canal, 
and  lodges  the  principal  portion  of  the 
nervous  centres — the  encei^halon. 

1.  Occipital  Bone. 
The  occipital  bone  occupies  the  superior 
extremity  of  the  head,  which  it  supports 
from  the  anterior  extremity  of  the  spine. 
This  bone  is  very  irregular  in  its  form,  and 
is  bent  at  a  right  angle  in  front  and  behind. 
It  has  an  external  and  an  internal  face,  and 
a  circumference  which  brings  it  into  contact 
with  the  adjoining  cranial  bones ;  the  latter 


HORSE  S   HEAD  ;    FRONT   VIEW. 

1,  Occipital  protuberance;  2,  Origin 
of  the  mastoid  crest ;  3,  Parietal 
bone  ;  4,  Saggital  suture ;  5,  Junc- 
tion of  the  parietal  and  temporal 
bones ;  6,  Zygomatic  arch ;  7, 
Frontal  bone ;  8,  Frontal  suture ; 
9,  Temporal  fossa  ;  10,  Supraorbi- 
tal foramen;  11,  12,  Lachrymal 
bone;  13,  Malar  bone;  14,  Xasal 
border  of  frontal  bone ;  1 5,  Nasal 
bone;  16,  Suture  of  nasal  bones  ; 
17,  Superior  maxillary  bone;  18, 
Infraorbital  foramen;  19,  Ante- 
rior, or  pre-maxillary  bone  ;  20, 
Foramen  incisivum ;  21,  Incisor 
teeth — young  mouth. 

is  subdivided  into  two  anterior 


34  THE  BONES. 

lateral  borders,  two  posterior  lateral  horders,  an  anterior  and  posterior  salient 
angle,  and  two  lateral  re-entering  angles. 

Faces. — The  external  face  is  divided  into  three  portions  by  the  double 
flexure  of  the  bone :  one  looks  forward,  another  upward,  and  the  third 
backward.  It  exhibits  : — 1.  On  the  median  line,  and  from  before  to  behind  : 
a,  an  antero-posterior  ridge  which  constitutes  the  origin  of  the  jjarietal 
ridges,  to  be  mentioned  hereafter ;  h,  a  transverse,  voluminous,  and  very 
prominent  eminence,  marked  posteriorly  by  deep  imjprints,  with  a  medimn 
projection  named  the  cervical  tuberosity ;  this  is  the  external  occipital  pro- 
tuberance  which,  in  the  Horse,  corresponds  at  the  same  time  to  the  superior 
curved  lines  of  the  occipital  bone  of  Man.  This  protuberance  forms  the 
culminating  point  of  the  head,  and  divides  the  anterior  aud  superior  parts  of 
the  external  face  of  the  bone  ;  c,  the  occipital  foramen  (foramen  magnum),  a 
large  orifice  that  passes  through  the  bone  at  the  posterior  flexure,  aud  esta- 
blishes a  communication  between  the  cranial  cavity  and  spinal  canal ;  d,  the 
external  surface  of  the  basilar  process,  a  narrow  and  thick  prolongation  formed 
by  the  bone  as  it  passes  to  meet  the  sphenoid  :  this  surface  is  convex  laterally. 
2.  On  the  sides :  a,  A  sharp  crest  which  prolongs,  laterally,  the  superior 
curved  lines,  and  descends  on  the  middle  of  the  lateral  anterior  border  to  be 
continued  with  the  superior  root  of  the  zygomatic  process  and  the  mastoid 
crest  of  the  temporal  bone  ;  b,  Linear  imprints,  parallel  to  the  latter,  and 
prolonged  on  the  base  of  the  styloid  process :  they  are  destined  for  the 
insertion  of  the  small  oblique  muscle  of  the  head,  and  rejiresent  the  inferior 
curved  lines  of  the  occipital  bone  of  Man  ;  c,  Within  these  imprints  is  a  slightly- 
roughened  cavity  for  the  insertion  of  the  posterior  recti  muscles ;  d.  The  two 
condyles,  articular  eminences  with  a  double  convexity,  one  superior,  the  other 
inferior  :  these  eminences  are  situated  on  each  side  of  the  occij^ital  foramen 
(foi-amen  magnum),  and  corresjDond  to  the  anterior  cavities  of  the  atlas ; 
e.  More  outwards  are  the  two  styloid  processes,  or  jugular  eminences,  long 
projections  flattened  on  each  side,  terminated  in  blunt  points,  directed  back- 
wards, and  separated  from  the  condyles  by  a  deep  space,  the  stylo-condyloid 
notch ;  f.  Under  the  condyles  is  the  condyloid  fossa,  a  smooth  depression, 
pierced  at  the  bottom  by  the  condyloid  foramen,  which  penetrates  the  cranium. 

The  internal  face  of  the  occipital  bone  is  concave,  and  shows:  beliind, 
the  foramen  magnum  ;  above,  an  uneven  surface,  which  forms  the  roof  of  the 
cerebral  cavity ;  below,  the  superior  face  of  the  basilar  process,  slightly 
hollowed  into  a  groove ;  on  the  sides,  the  internal  orifice  of  the  condyloid 
foramen. 

Circumference. — The  anterior  lateral  borders  are  thick,  and  are  united  by 
suture  with  the  parietal  bone,  and  vnXh.  the  tuberous  jiortion  of  the  temporal 
bone  by  the  harmonia^  suture.  The  posterior  lateral  borders  are  sharp,  and 
constitute  the  sides  of  the  basilar  process ;  each  coucurs  in  the  formation  of 
the  occipito-splieno-temporal  hiatus,  also  termed  the  lacerated  foramen,  a  vast 
irregular  opening,  extending  from  above  downwards,  jienetrating  the 
cranium,  and  divided  by  a  ligament,  in  the  fresli  state,  into  two  jiortions, 
one  inferior,  the  anterior  lacerated  foramen,  the  other  superior,'-  the  posterior 
lacerated  foramen.  The  anterior  angle,  which  is  dcntated,  is  dovetailed  into 
the  parietal  bone.  The  posterior  angle  is  very  thick,  aud  forms  the  summit 
of  the  basilar  process ;  it  is  united  by  suture  with  the  body  of  the 
sphenoid.     The  lateral  re-entering  angles,  or  jugular  notches,  correspond  to  the 

'  (The  harmonia  suture  (&pe7v,  to  adapt)  is  the  simple  apposition  of  contiguous  borders, 
whicli  nre  roufihened  to  facilitate  retention.) 

'  (The  anterior  and  posterior  lacerated  foramen  of  Man.) 


THE  HEAD.  35 

point  where  tlie  bono  is  bent  posteriorly ;  they  separate  the  anterior  lateral 
from  the  corresponding  posterior  lateral  border,  and  ai'e  occupied  by  the 
tuberous  portion  of  the  temporal  bone. 

Structure. — The  occipital  bone  contains  much  spongy  substance. 

Development. — It  is  developed  from  four  centres  of  ossification  :  one,  the 
anterior,  is  single,  and  forms  the  occij)ital  protuberance;  another,  the 
posterior,  also  single,  forms  the  basilar  process ;  the  other  two  are  pairs,  and 
comprise  each  a  condyle,  with  the  styloid  process  and  the  corresponding 
condyloid  foramen. 

2.    The  Parietal  Bone. 

The  parietal  is  a  wide  and  thin  bone,  very  much  arched  to  form  the  roof 
of  the  cranial  cavity.  It  is  bounded  above  by  the  occipital  bone,  below 
by  the  frontal,  and  laterally  by  the  two  temporal  bones.  It  otters  for  study 
an  external  and  internal  face,  and  a  circumference  divided  into  four  regions  or 
borders. 

Faces. — The  external  face  is  convex.  It  exhibits  two  curved  ridges  whose 
concavity  is  directed  outwards  ;  these  two  crests,  which  are  termed  the 
parietal  ridges,  approach  each  other  and  unite  superiorly,  to  be  continued 
with  the  antero-posterior  ridge  of  the  occipital  bone ;  below  they  diverge 
and  proceed,  one  on  each  side,  to  join  the  supraorbital  process.  They 
divide  the  surface  of  the  bone  into  three  portions  :  two  lateral,  which  are 
rough  and  traversed  by  vascular  channels,  forming  part  of  the  temporal  fossae ; 
the  third,  or  middle,  is  plane,  smooth,  and  of  a  triangular  form,  and  covered 
by  the  skin.  The  internal  face  is  concave,  covered  by  digital  impressions, 
and  grooved  by  small  vascular  canals  ;  it  offers,  on  the  median  line,  and 
altogether  above,  the  parietal  eminence.^  This  trifacial  and  very  salient  pro- 
jection presents  at  its  base,  on  each  side,  an  excavation  elongated  trans- 
versely, into  which  opens  the  parieto-temporal  canal,  and  which  is  destined 
to  lodge  a  venous  sinus.  It  is  continued,  in  front,  by  a  median  crest,  which 
is  often  replaced  by  a  slight  groove,  the  saggitcd  furrow,  bordered  by  linear 
imprints.  Two  other  ridges,  resulting  from  the  abutment  of  the  lateral 
border  of  the  bone  against  the  anterior  face  of  the  petrous  bone,  rise  from  the 
sides  of  this  eminence  and  descend  to  the  sphenoid  bone ;  they  separate  the 
cerebral  from  the  cerebellar  cavity. 

Borders. — The  superior  border  is  notched,  thick,  and  slightly  dentated  ; 
it  articulates  with  the  occipital  bone.  The  inferior  border,  slightly  concave, 
and  deeply  dentated,  offers  an  external  bevel  in  its  middle  portion,  and  an 
internal  bevel  on  its  sides ;  it  corresponds  with  the  frontal  bone.  The 
latercd  borders  are  very  thin,  and  are  cut  at  the  expense  of  the  external  plate 
into  a  wide,  sloping  edge,  which  shows  a  groove  destined  to  form  the 
parieto-temporal  canal.  A  very  prominent  angle  separates  each  into  two 
portions,  an  inferior,  that  articulates  by  suture  with  the  squamous  portion 
of  the  temporal  bone  ;  and  a  superior,  curved  inwards  towards  the  centre  of 
the  cranial  cavity ;  the  latter  portion  of  the  lateral  border  is  in  contact 
with  the  anterior  face  of  the  petrous  portion  of  the  temporal  bone,  with 
which  it  concurs  to  form  the  lateral  crest  that  descends  to  the  parietal 
eminence. 

Structure. — This  bone  contains  much  compact  tissue,  the  spongy  sub- 
stance existing  only  in  its  middle. 

Development. — It  is  developed  from  two  large  centres  of  ossification,  to 

'  The  internal  occipital  eminence  of  Man. 


36  TSE  BONES. 

which  is  added  a  single  ceutre  to  form  the  parietal  eminence.^     In  early- 
life  the  parietal  ridges  are  absent. 

3.  Frontal  Bone. 

The  frontal  is  a  flat  quadrilateral  bone,  whose  sides  are  bent  in  the 
middle  at  an  acute  angle,  and  are  carried  back,  and  a  little  inwards,  to  meet 
the  wings  of  the  sphenoid  bone.  It  assists  in  forming  the  cranial  roof  and 
part  of  the  face.  It  is  bordered :  above,  by  the  parietal  bone  ;  below,  by  the 
nasal  and  lachrymal  bones ;  and  on  each  side,  by  the  temporal  bones.  It 
otfers  for  study  an  external  and  an  internal  face,  and  /o?fr  herders. 

Faces. — The  external  face  is  divided,  by  the  double  flexui-e  of  the  bone, 
into  thi'ee  regions :  a  middle  and  two  lateral.  The  first,  nearly  plane,  is 
lozenge-shaped,  is  covered  by  the  skin,  and  constitutes  the  base  of  the  fore- 
head. It  gives  rise  on  each  side,  at  the  point  where  it  is  inflected,  to  a  long 
2)rocess,  flattened  above  and  below,  which  curves  backward,  forming  the  orbital 
arch.  The  superior  or  external  face  of  this  pi'ocess  is  convex  and  slightly 
roughened ;  the  intei'nal  face  is  smooth  and  concave,  and  forms  part  of  the 
orbital  fossa.  Its  posterior  border,  thick  and  concave,  is  continued,  in- 
wardly, with  the  corresponding  parietal  ridge,  and  outwardly  with  the 
superior  border  of  the  zygomatic  process.  It  limits,  in  front,  the  temporal 
fossa.  The  anterior  border,  also  concave,  but  thin,  concurs  in  the  forma- 
tion of  the  orbital  margin ;  the  summit,  thickened  and  denticulated,  rests 
upon,  and  is  united  to,  the  zygomatic  j^rocess  of  the  temjioral  bone ;  the  base 
is  wide,  and  is  traversed  by  an  opening  termed  the  sup-aorhital,  or  super- 
ciliary foramen.  The  two  lateral  regions  of  the  external  face  of  the  frontal 
bone  are  slightly  excavated,  and  assist,  for  the  greater  portion  of  their 
extent,  to  form  tlie  orbits.  They  often  show,  near  the  base  of  the  orbital 
arch,  a  small  depression  corresponding  to  the  flexure  described  by  the 
great  oblique  muscle  of  the  eye  in  2)assing  through  its  pulley. 

The  internal  face  of  the  frontal  bone  is  concave,  and  divided  into  two 
unequal  jjarts  by  a  transverse  ridge,  corresponding  to  the  anterior  border  of 
the  cribriform  plate  of  the  ethmoid  bone.  The  superior,  the  most  extensive, 
is  covered  with  digital  impressions,  and  belongs  to  the  cranial  cavity.  It 
exhibits :  1,  On  the  median  line,  a  slight  furrow,  or  a  crest  which  is  con- 
tinuous, above,  with  the  median  ridge  of  the  parietal  bone,  and  below,  with 
the  crista- gain  process  ;  2,  On  the  sides,  and  in  the  re-entering  angle  formed 
by  the  flexure  of  the  bone,  there  is  a  narrow  slit,  or  mortice,  which  receives 
the  wing  of  the  sphenoid  bone.  The  inferior  part  is  united,  on  the  median 
line,  to  the  perpendicular  plate  of  the  ethmoid.  It  assists  in  forming  the 
bottom  of  the  nasal  cavities,  and  presents  laterally  two  large  openings 
which  lead  to  the  frontal  sinuses — vast  anfractuous  spaces  excavated 
between  the  two  plates  of  the  bone. 

Borders. — Tlie  superior  border  is  denticulated,  and  cut  obliquely,  in  its 
middle  portion,  at  the  expense  of  the  internal  plate,  and  on  the  lateral  parts 
at  the  expense  of  the  external  table ;  it  is  in  contact  with  the  parietal  and 

'  Tliis  centre  is  described  as  the  interparietal  hone  by  those  anatomists  who  consider 
the  two  lateral  centres  as  two  distinct  parietals.  (Leyh  is  one  of  the  veterinary  anatomists 
who  describe  thi.s  nucleus  as  a  separate  bone,  designating  it  the /aZe//'o?-m  or  mfe»7jar/etoZ 
Ijone.  He  also  describes  the  parietal  as  a  •pair  or  double  bone  ;  whereas  the  majority  of 
French  anatomists  include  the  interparietal  bone  as  tlie  mediiin  protuberance  of  the 
parietal,  which  they  look  upon  as  a  single  or  impair  bone.  Percivall  names  it  a  pair  bone, 
but  follows  the  example  of  the  French  hippotomists  with  regard  to  the  interparietal.) 


THE  HEAD.  37 

squamous  portion  of  the  temporal  bone.  Tlie  inferior,  prolonged  to  a 
point  in  tlie  middle,  is  in  apposition  witli  the  nasal  bones  through  the 
medium  of  a  wide  external  bevel ;  laterally,  it  is  very  thin,  faintly  serrated, 
and  artieulates  with  the  lachrymal  bone.  The  lateral  borders,  thin  and 
irregular,  present  two  notches :  one,  the  superior,  is  wide  and  deep,  and 
occupied  by  the  wing  of  the  sj)henoid  bone ;  the  other,  inferior,  is  very 
narrow,  and  uniting  with  a  similar  notch  in  the  sphenoid  bone,  forms  the 
orbital  foramen,  which  opens  into  the  cranium,  very  near,  but  external  to, 
the  ethmoid  fossa.  Each  of  these  borders,  also,  is  adapted,  for  a  limited 
extent,  to  the-  corresponding  palate  bone* 

Structure. — The  two  compact  plates  of  the  frontal  bone  are  separated  by 
spongy  texture  towards  the  middle  and  in  the  upper  part ;  they  separate 
below  to  form  the  frontal  sinuses.  Laterally,  they  are  very  thin  and 
consolidated  with  each  other. 

Dcrelopment. — The  frontal  bone  is  developed  from  two  lateral  centres  of 
ossification,  which  only  coalesce  at  a  late  period.  In  youth  the  cranial 
portion  of  the  bone  forms,  in  front  of  the  head,  a  large  rounded  protuberance 
standing  beyond  the  facial  portion.  This  prominence  disappears  when  the 
frontal  sinuses  begin  to  be  developed.  These  cavities  do  not  exist  at  an 
early  period  of  foetal  life ;  but  commence  to  form  about  the  fourth  month  of 
conception,  by  a  process  of  resorjition,  which  removes  the  spongy  substance 
interposed  between  the  two  compact  tables  of  bone,  and  may  even  cause  the 
destruction  of  the  internal  table.  The  sinuses  enlarge  with  age,  and  remain 
during  life  separated  from  one  another  by  a  vertical  septum. 

4.  Ethmoid  Bone. 

The  ethmoid  hone,  deeply  situated  in  the  limit  between  the  cranium  and 
the  face,  is  inclosed  between  the  frontal,  the  sphenoid,  the  vomer,  the  palate, 
and  the  supermaxillary  bones.  It  is  composed  of  three  portions :  a 
jperpendlcular  plate,  and  tivo  lateral  masses. 

The  Perpendicular  Lamina  of  the  Ethmoid  Bone. — Situated  in  the 
median  j^lane,  and  flattened  on  both  sides,  this  bone  presents  two  faces,  a  left 
and  right,  and  four  borders. 

Faces. — The  faces,  covered  by  the  pituitary  membrane,  present,  pos- 
teriorly, small  sinuous  crests  ;  elsewhere  they  are  smooth.  A  very  narrow 
interval,  constituting  the  bottom  of  the  nasal  cavities,  separates  them  from 
the  lateral  masses. 

Borders. — The  superior  border  looks  towards  the  centre  of  the  cranial 
cavity,  and  constitutes  what  is  called  the  ethmoidal  ridge,  or  crista-galli 
process.  It  is  free,  concave,  and  sharp,  prolonged  in  front  and  above  by  the 
median  crest  of  the  frontal  bone,  and  confounded  behind  with  the  middle 
portion  of  the  inferior  sphenoid.  The  inferior  border  is  continuous  with  the 
cartilaginous  plate  which  separates  the  nasal  cavities.  When  this  plate 
becomes  ossified,  which  is  not  unfrequent,  it  is  impossible  to  discover  the 
point  where  it  begins  or  the  ethmoid  bone  terminates.  The  middle  septum 
of  the  nose  has  been  considered,  and  justly,  as  a  prolongation  of  the  perpen- 
dicular plate  (or  lamina)  of  this  bone.  The  anterior  border  is  consolidated 
with  the  vertical  septum  which  separates  the  frontal  sinuses.  The  posterior 
border  is  joined,  above,  to  the  median  plate  which  divides  the  si:)henoidal 
sinuses  into  two  compartments.  Below,  it  is  fixed  in  the  groove  of  the 
vomer,  and  soon  becomes  confounded  with  that  bone,  which  is  itself  conso- 
lidated with  the  inferior  sphenoid. 

Lateral  Masses  of  the  Ethmoid  Bone. — These  are  two  large  pyrifonn 
6 


38 


THE  BONES. 


tuberosities  placed  on  each  side  of  the  perpendicular  lamina,  and  offering 
for  study  a  middle  portion,  a  base,  and  a  summit.  Each  of  these  is  formed  by 
an  assemblage  of  numerous,  extremely  thin,  osseous  plates,  curved  into 
small  and  very  fragile  convolutions.  These,  elongated  from  above  to  below, 
become  lonf^er  as  they  are  more  anterior  ;  they  are  attached  by  their  superior 
extremities  to  the  transverse  plate  which  separates  the  cranium  from  the 
nasal  cavities,  and  by  one  of  their  borders  to  a  thin  leaf  of  bone  which 

envelops  the  lateral  masses  out- 
wardly. They  have  received  the 
name  of  the  ethmoidal  volutes  (or 
cells). 

Middle  portion. — This  should 
be  studied  externally  and  inter- 
nally. 

The  external  surface  of  each 
ethmoidal  mass  is  divided  into  two 
sections :  an  internal,  making 
part  of  the  nasal  cavities ;  the 
other,  external,  concurs  in  form- 
ing the  walls  of  the  f 'ontal  and 
maxillary  sinuses.  The  first,  the 
least  extensive,  is  almost  plane ; 
jmrallel  to  the  perpeudicitlar  la- 
mina, it  is  isolated  from  it  by  the 
narrow  space  which  forms  the 
bottom  of  the  nasal  cavities ;  it 
jiresents  several  openings  which 
separate  the  most  superficial  cells, 
and  join  the  internal  canals  to  be 
hereafter  noticed.      The   second, 

A,  Occipital  bone. — 1,  Condyle ;  2,  Con- 
dyloid foramen;  3,  Styloid  process; 
4,  Summit  of  basilar  process. — n,  Parie- 
tal bone. — 8,  Parietal  protuberance; 
9,  Channel  which  concurs  to  form  the 
parieto-temporal  canal.  —  C,  Frontal 
bone. — 10,  Transverse  crests  separating 
the  cranial  from  the  facial  portion  of 
the  bone;  11,  Frontal  sinuses;  12, 
Notch  on  the  lateral  border  occupied 
by  the  wing  of  the  sphenoid  bone ;  13, 
Notch  for  the  formation  of  the  oi-bital 
foramen ;  1-1,  Summit  of  the  orbital 
process :  15,  Sujiraorbital  foramen. — 
D,  Perpendicular  lamma  of  the  ethmoid 
bone. — E,  E,  Lateral  masses  of  the  eth- 
moid bone. — 16,  The  great  ethmoid  cell. 
— F,  Squamous  portion  of  the  temporal 
bone. — 17,  Supercondyloid  process  ; 
18,  Channel  for  tlie  formation  of  the 
parieto-temporal  canal. — G,  Tuberous 
portion  of  the  temporal  bone. — 5,  Mas- 
toid process;  G,  Internal  auditory 
hiatus ;  7,  Opening  for  the  eustachian 
ANTERIOR  BONES  OF  THE  HEAD  OF  A  FCETUS  tube  into  the  tympanum. — H,  Lach- 
(horse)  at  birth  ;  DISARTICULATED,  AND  rymal  bone. — I,  Nasal  bone. — J,  Su- 
VIEWED  FROM  BEHIND.  perior  turbinated  bone. 


THE  HEAD.  39 

very  extensive  and  convex,  looks  outwards  in  front  and  behind,  and  is  covered 
by  an  osseous  i)late  traced  with  shallow  furrows,  which  correspond  internally 
-with  the  small  crests  to  which  the  cells  are  attached.  This  lamella  is 
prolonged,  inferiorly,  a  little  beneath  the  inferior  extremity  of  these  latter, 
and  turns  outwards  to  articulate  with  the  palate  and  superior  maxillary 
bones ;  superiorly,  it  coalesces  with  the  sphenoid  and  the  orbital  portion  of 
the  frontal  bone. 

Internalhj,  the  lateral  masses  are  hollowed  from  above  to  below  by 
extremely  diverging  canals,  which  open  inferiorly  into  the  nasal  cavities, 
and  separate  the  cells  from  one  another.  The  latter  are  so  incurvated  that 
the  internal  cells  communicate  with  each  other.  There  are  some,  however, 
which  are  com2)letely  closed  ;  the  anterior,  or  great  cell,  is  frequently  so.^ 

Base. — The  base  of  each  lateral  mass  looks  upwards,  and  is  formed  by  the 
transverse  septum  between  the  cranium  and  the  nasal  cavities.  This 
septum  is  perforated  by  openings  which  give  passage  to  the  ethmoidal  nerves ; 
it  is  named  the  cribriform  plate  of  the  ethmoid  bone.  It  is  concave  on 
the  superior  surface,  which  constitutes  the  ethmoidal  fossa,  and  convex  on 
the  opposite  face,  where  attachment  is  given  to  the  superior  extremities  of 
the  cells.  It  is  consolidated  internally  -with  the  perpendicular  j^late ;  the 
other  points  of  its  circumference  are  attached  to  the  sphenoid  bone,  and  to 
the  transverse  ridge  on  the  internal  face  of  the  frontal  bone. 

Summit. — The  summit  of  each  lateral  mass  is  formed  by  the  inferior 
extremity  of  the  ethmoidal  cells,  which  is  directed  downwards  towards  the 
nasal  cavities.  One,  more  voluminous  than  the  others,  is  carried  much 
lower,  and  terminates  by  a  rounded  protuberance.  It  corresponds  to  the 
middle  cornu  (concha  media)  of  Man. 

Structure  of  the  ethmoid  bone. — Very  little  spongy  tissue  enters  into  the 
composition  of  this  bone,  and  this  is  only  found  near  the  anterior  border  of 
the  jjerpendicular  plate. 

Development. — The  ethmoid  bone  is  late  in  attaining  its  development, 
and  the  adjoining  bones  are  nearly  completely  ossified  when  it  is  yet 
entirely  cartilaginous.  The  bony  transfoimation  commences  in  it  at  the 
inferior  extremity  of  the  cells,  and  advances  progressively  from  below 
upwards.  The  peri^endicular  plate  is  only  ossified  in  part  when  the  cells 
have  passed  through  the  first  half  of  the  process :  at  the  same  time  it 
coalesces  with  the  inferior  sphenoid.  The  cribriform  plate  is  the  last  to 
become  ossified ;  this  transformation  having  scarcely  been  achieved  when 
the  animal  is  six  or  eight  months  old. 

5.  Sphenoid  Bone. 

The  sphenoid  bone  is  situated  behind  the  cranium,  between  the  occipital, 
ethmoidal,  palate,  vomer,  pterygoid,  frontal,  and  temporal  bones.  It  is 
flattened  from  before  to  behind,  curved  from  one  side  to  the  other,  thick  in 
its  middle  part,  named  the  body,  and  thin  on  the  sides,  which,  in  their 
inferior  half,  are  prolonged  in  the  form  of  alee  or  wings.  It  has  two  surfaces 
and  four  borders. 

Surfaces. — The  external  surface  is  convex,  and  presents :  1,  On  the 
median  line,  the  external  surface  of  the  body,  rounded  from  one  side  to  the 
other,  is  continued  with  that  of  the  basilar  process,  and  has  marked  mus- 
cular imprints  superiorly;  2,  On  the  sides  and  from  within  outwards :  a, 
the  vidian  (or  pterygoid)  fisnire,  directed  from  above  downwards,  and  con- 
tinued by  the  vidian  canal,  a  very  small  foramen  which  opens  into  the 
'  It  is  not  rare  to  find  it  opening  into  the  frontal  sinus. 


40  THE  BONES. 

orbital  hiatus ;  h,  the  snhspJienoidal,  or  ptenjgoid  process,  a  long  eminence, 
flattened  on  both  sides,  inclining  downwards,  articulating  with  the  palate 
and  pterygoid  boues,  and  traversed  at  its  base  by  the  vidian  canal ;  c,  a 
little  behind  and  above  this  eminence,  the  superior  orifice  of  the  siih- 
sphenoidal  foramen,  a  large  canal  which  bifurcates  inferiorly ;  d,  more  in 
front,  the  orbital  hiatus,  a  kind  of  vestibule  into  which  open  in  common  the 
principal  branch  of  the  subsi^henoidal  canal,  the  three  supersj^hcnoidal 
canals,  the  vidian  and  optic  canals,  and  the  orbital  opening :  this  hiatus  is 
surmounted  by  a  thin  and  sharp  bony  plate,  above  which  opens  the  smallest 
branch  of  the  subspheuoidal  foramen ;  e,  altogether  without  the  hiatus  is 
remarked  a  smooth  surface  belonging  to  the  wing  of  the  sphenoid,  and 
which  concurs  to  form  the  orbital  cavity. 

The  internal  face  is  concave  from  side  to  side.  It  shows :  1,  On  the 
median  line,  and  from  before  to  behind,  a  small  projection  united  to  the 
crista-galli ;  the  optic  fossa,  elongated  transversely  in  the  form  of  a  shuttle, 
and  presenting  at  the  bottom,  and  on  each  side,  the  superior  orifice  of  the 
optic  foramen,  a  cylindrical  canal  directed  obliquely  downwards,  forwards, 
and  outwards,  to  reach  the  orbital  hiatus  ;  the  supersp>lienoidal  or  pituitary 
fossa,  also  named  the  sella  turcica,  a  slight  depression,  limited  behind  by  a 
scarcely  noticeable  transverse  projection  separating  it  from  the  superior 
channel  of  the  basilar  process;  2,  On  the  sides,  and  in  front,  the  internal 
surface  of  the  wings,  depressed  by  very  superficial  digital  impressions  ; 
more  behind  and  outwards,  a  fossa,  elongated  from  before  to  behind,  which 
lodges  the  mastoid  lobule  of  the  brain ;  between  this  fossa  and  the  sella 
turcica,  two  vertical  fissures  :  an  internal,  named  the  cavernous  sinus,  and  an 
external,  wider  and  deeper,  for  the  passage  of  a  large  nervous  branch. 
These  two  fissures  open  below,  near  the  junction  of  the  three  super- 
sphenoidal  canals.  Two  of  these,  which  are  very  wide,  are  placed  one  before 
the  other,  and  separated  only  by  a  slight  partition.  The  superior  of  these 
constitutes  tlie  great  sphenoidal  fissure  ;  the  other,  the  lower,  is  i\\Q  foramen 
rotundum,  and  opens  into  the  orbital  hiatus.  The  third,  very  small,  is  situated 
outside  the  great  anterior  canal,  opens  above  the  optic  foramen,  witliin  the 
bony  mass  surmounting  the  hiatus,  and  sometimes  on  the  free  margin  of 
this  lamina. 

Borders. — The  superior  is  a  little  concave,  and  shows,  in  its  middle,  the 
superior  extremity  of  the  body,  mammillated  and  articulated  with  the 
summit  of  the  basilar  process  ;  on  each  side,  two  notches  which  circumscribe 
below  the  occipito-si^heno-temporal  hiatus  (foramina  lacera  basis  cranii). 
The  internal  notch  is  the  narrowest,  and  from  its  afibrding  a  passage  for  the 
internal  carotid  artery,  is  called  the  carotid  notch  ;  it  is  continued  on  the 
external  face  of  the  bone  by  a  smooth  excavation  to  which  Eigot  has  given 
the  name  of  carotid  fossa.  The  external  is  also  j)rolonged  on  the  exterior 
surface  cf  the  sj)henoid  by  a  short  and  wide  fissure ;  it  lodges  the  inferior 
maxillary  nerve.  Outside  this  is  another  very  narrow  notch,  intended  for 
the  passage  of  the  middle  meningeal  artery.  The  fibro-cartilaginous  sub- 
stance that  partly  fills  the  occii>ito-spheno-temporal  hiatus,  transforms  these 
notches  into  foramina,  the  first  of  which  is  named  the  carotid  canal,  the 
second,  i\iG  foramen  ovale,  and  the  third,  the  foramen  spinosum.  The  inferior 
border,  also  concave,  is  likewise  divided  into  three  portions,  a  middle  and 
two  lateral.  The  first  is  thick,  and  formed  by  the  inferior  extremity  of  the 
body ;  it  is  excavated  by  two  large  cavities  belonging  to  the  sphenoidal  sinus. 
These  cavities  are  separated  from  one  another  by  a  vertical  osseous  plate, 
often  perforated,  which,  at  an  early  period,  is  fused  with  the  perpendicular 


THE  HEAD. 


41 


lamina  of  the  etlimoicl  bone.     The  very  thin  lateral  portions  form  part  of  the 

notched  near  their  union  with  the 


circuraff;rcuce  of  the  wings ;  they  are 
niidclle  piece  to  assist  in  the  formation 
of  the  orbital  foramen.  The  ta-o  htcral 
borders  are  thin  aiul  convex  in  their  an- 
terior half,  as  is  also  the  contour  of  the 
wings,  which  are  mortised  in  the  frontal 
bone.  For  the  remainder  of  tlieir  extent 
they  are  thick,  denticulated,  and  bevelled 
at  the  expense  of  the  external  plate,  to 
articulate  with  the  sq[uamous  portion  of 
the  temporal  bone. 

Structure. — This  bone  is  compact  on 
its  sides,  and  spongy  in  its  middle  part ; 
inferiorly,  it  is  excavated  by  the  splie- 
noidal  sinuses. 

Development. — It  is  developed  from 
two  principal  nuclei  of  ossification ;  a 
superior  forms  the  subsphenoidal  pro- 
cess and  the  canal  of  the  same  name, 
the  vidian  fissure,  pituitary  fossa,  fissures 
of  the  internal  face,  and  the  most  pos- 
terior of  the  great  supersphenoidal 
canals  ;  the  other,  the  inferior,  forms  that 
portion  of  the  body  hollowed  by  the 
sinuses,  the  lateral  ala3,^  and  the  optic 
fossa  and  canals.  In  meeting  each 
other,  these  centres  form  the  vidian  canal 
and  the  two  anterior  supersphenoidal 
canals.  They  are  not  consolidated  with 
each  other  until  a  very  late  pei'iod  ;  for 
which  reason  they  are  sometimes  de- 
scribed as  two  distinct  bones.  M. 
Tabourin  has  even  proposed  to  attach 
the  description  of  the  inferior  sjjhenoid 
to  that  of  the  ethmoid,  because  it  is  a,  Sphenoid  bone, 
united  with  this  bone  a  long  time  before 
it  is  joined  to  the  superior  portion. 


I'iir.  20. 


6.   Temporal  Bone, 
temporal     hones     inclose 


POSTERIOR  BONES  OF  THE  HEAD  OF  A 
FCETUS  (horse)  AT  BIRTH;  DISARTICU- 
LATED   AND    VIEWED    IN    FRONT, 

1,  Maxillary  notch  ;  2, 
Carotid  notch  ;  3,  Groove  for  the  passage 
of  the  maxillary  nerve;  4,  Cavernous 
sinus;  5,  Optic  fossa;  6,  Great  wing; 
6',  Unossified  portion  of  the  great  wing  ; 
7,  Kotch  for  the  formation  of  the  orbital 
foramen. — B,  Vomer. — C,  Palate  bone. — 
D,  Zygoma. — E,  Superior  maxilla. — 8,  In- 
ferior orifice  of  the  maxillo-dental  canal. 
— F,  Premaxillai-y  bone. 


The  temporal  hones  inclose  the 
cranial  cavity  laterally,  and  articulate 
with  the  occipital,  parietal,  frontal, 
sphenoidal,  and  the  zygomatic  bones ; 
also  with  the  inferior  maxilla  and  the  hyoid  bone.  Each  is  divided  into 
two  pieces,  whicli  are  never  consolidated  in  the  horse ;  one  forms  the 
squamous  portion  of  the  temporal  hone  ;  the  other,  the  tuberous  portion.  They 
will  be  described  separately. 

Squamous  Portion. — This  is  flattened  on  both  sides,  oval,  and  slightly 
incurvated  like  a  shell,  a  shape  to  which  it  owes  its  name.  It  offers  for 
study  an  external  and  an  infernal  face,  and  a  circumference. 

>  These  wings  arc  not  analogous  to  those  portions  of  the  sphenoid  bone  in  Man  bear- 
ing the  same  name.     They  are  the  processes  of  Ingrassias  enormously  developed. 


42  TEE  BONES. 

Faces. — The  external  face  is  convex,  and  marked  by  some  muscular 
imprints,  vascular  fissures,  and  openings  which  penetrate  the  parieto- 
temporal canal.  It  forms  part  of  the  temporal  fossa,  and  gives  origin  near 
its  middle  to  the  zygomatic  process,  a  long  eminence  which  at  first  runs 
outwards,  and  soon  curves  forwards  and  downwards  to  terminate  in  a 
thin  summit.  The  base  of  this  eminence  forms,  in  front,  a  concave  surface 
belonging  to  the  temporal  fossa;  behind,  it  offers  the  articular  surface  which 
corresponds  with  the  maxillary  bone.  The  latter  is  composed  of:  1,  A  condyle 
transversely  elongated,  convex  above  and  below,  and  slightly  concave  from 
side  to  side ;  2,  A  glenoid  cavity,  limited  below  by  the  condyle,  above  by  a 
mammiform  eminence,  the  super  condyloid, '^  against  which  rests  the  maxillary 
condyle  when  tliis  bone  is  drawn  backwards;  it  is  immediately  above  this 
eminence  that  the  inferior  orifice  of  the  parieto-temporal  canal  opens.  The 
ea-fernaZ /ace  of  the  zygomatic  process  is  smooth  and  convex;  the  internal, 
concave,  is  also  smooth,  and  bordered  outwards  by  the  temporal  fossa.  Its 
anterior  border  is  sharp  and  convex ;  the  posterior,  very  short,  is  thick  and 
roughened.  Its  summit  is  flattened  from  before  to  behind,  and  marked  by 
notches  on  its  two  faces;  it  somewhat  resembles  a  wedge,  fixed  as  it  is 
between  tlie  orbital  process  of  the  frontal  bone  and  the  zygoma ;  it  comes 
in  contact  with  the  maxillary  bone,  and  by  a  small  portion  of  its  anterior 
face,  which  is  deprived  of  notches,  it  concurs  in  circumscribing  the  orbital 
cavity.  In  the  domesticated  animals,  as  in  Man,  the  zygomatic  process 
appears  to  arise  from  the  surface  of  the  bone  by  two  roots :  one,  the  inferior 
or  transverse,  is  represented  by  the  condyle ;  the  other,  the  superior,  forms  a 
sharp  crest  which  is  continuous  with  the  anterior  border  of  the  process,  and 
above,  joins  the  lateral  crest  of  the  occipital  protuberance. 

The  internal  or  cerebral  face  of  the  squamous  portion  is  divided  into  two 
parts  by  an  almost  vertical  channel  which  terminates  above  the  super- 
condyloid  eminence,  and  which,  meeting  a  similar  furrow  on  the  parietal 
bone,  forms  the  parieto-temporal  canal.  The  superior  portion  is  but  of 
small  extent,  and  of  a  triangular  form  ;  it  articulates  by  a  simple  harmonia 
suture  with  the  external  face  of  the  petrous  portion.  The  inferior  part,  the 
widest,  presents  in  its  middle  some  cerebral  impressions.  For  the  re- 
mainder of  its  extent  or  circumference,  it  is  cut  into  a  wide,  dentated,  and 
lamellar  bevel,  which  brings  it  in  contact  with  the  surrounding  bones. 

Circumference. — This  may  be  divided  into  two  borders  :  one,  anterior,  is 
convex  and  united  with  the  parietal  and  frontal  bones  ;  the  other,  posterior, 
articulates  with  the  sphenoid  in  its  inferior  moiety,  and  is  provided,  above 
the  level  of  the  supra-condyloid  eminence,  with  a  deep  notch  which  receives 
the  external  auditory  canal.  Superiorly,  the  two  borders  unite  at  the  summit 
in  a  thin  point  which  rests  on  the  occipital  bone. 

Structure.— The  squamous  portion  of  the  temporal  bone  is  formed  of 
two  very  thin  compact  plates  which  have  but  little  spongy  tissue  between 
them ;  the  latter,  however,  is  very  abundant  in  the  body  of  the  zygomatic 
process. 

Development. — It  is  developed  from  a  single  nucleus  of  ossification. 

Tuberous  Pouiion. — This  is  one  of  the  most  interesting  parts  of  the 
skeleton  for  study,  in  consequence  of  its  containing  two  systems  of  cavities 
which  inclose  the  essential  organs  of  hearing.  One  of  these  systems  is 
named  the  cavity  of  the  tympanum  or  middle  ear ;  the  other  forms  the  internal 
ear.     These  cavities  mil  be  studied  when  we  come  to  speak  of  the  auditory 

'  In  Man  Ihis  is  rei:)resentecl  by  the  inferior  or  vertical  ramus  of  the  upper  root  of  tho 
zygomatic  process. 


THE  HEAD.  43 

apparatus.     In  the  meantime,  only  the  exterior  surface  and  the  structure 
and  development  of  this  portion  of  the  temporal  hone  will  be  noticed. 

It  is  wedged  between  the  antero-lateral  border  of  the  occipital  bone,  the 
lateral  border  of  the  ])arietal,  and  the  superior  part  of  the  internal  face  of 
the  temporal  shell.  It  represents  a  quadrangular  pyramid  whose  base  is 
turned  downwards  and  a  little  backwards.  It  will  be  studied  successively  in 
its  four  faces,  a  summit,  and  base. 

Faces. — The  anterior  face  is  united  by  harmonia  suture  to  the  parietal 
bone.  The  posteriir  face  articulates  in  the  same  manner  A^'ith  the 
occipital  bone.  The  external  face  lies  against  the  squamous  portion  of  the 
bone.  The  internal  face,  slightly  concave  and  marked  by  very  superficial 
digital  impressions,  furms  a  part  of  the  lateral  wall  of  the  cerebellar  cavity. 
It  presents  the  canal  or  internal  auditory  hiatus  (meatus  auditorius  internus), 
a  small  fossa,  the  bottom  of  which  is  pierced  by  several  foramina  for  the 
transmission  of  nerves ;  the  largest  of  these  is  the  internal  orifice  of  the 
aquceductts  Fallopii,  a  flexuous  canal  which  passes  through  the  bone  and 
opens  at  the  external  surface  of  its  base ;  the  other  foramina  penetrate  tlie 
cavities  of  the  internal  ear. 

These  faces  are  separated  from  each  other  by  so  many  borders  or  plane 
angles,  two  of  which  more  particularly  merit  attention ;  one  of  these  isolates 
the  external  from  the  posterior  face,  and  the  other  separates  the  anterior 
from  the  internal  face.  The  frst  is  thick  and  rugged,  and  constitutes  the 
mastoid  crest ;  it  is  continuous  above  with  the  lateral  ridge  of  the  occipital 
bone,  after  being  united  to  the  superior  root  of  the  zygomatic  jirocess,  and 
terminates,  near  the  base  of  the  bone,  by  a  tuberosity  for  muscular  insertion, 
to  which  has  been  given  the  name  of  mastoid  process.  This  border  is 
traversed  by  a  slit,  the  mastoid  fissure,^  which  passes  under  the  squamous 
portion  and  enters  the  jiarieto-temporal  canal.  The  second  is  thin,  and, 
with  the  superior  part  of  the  lateral  border  of  the  parietal  bone,  forms  the 
crest  which  establishes  the  line  of  demarcation  between  the  cerebral  and 
cerebellar  cavities  of  the  cranium ;  it  gives  attachment  to  the  tentorium 
cerebelli. 

Summit. — This  is  slightly  denticulated,  and  articulates  with  the  occipital 
bone. 

Base. — This  is  very  irregular,  and  offers  :  outwardly,  the  external  auditory 
canal  which  penetrates  the  middle  ear,  and  the  external  orifice  of  which  has 
been  named  in  veterinary  anatomy  the  external  auditory  hiatus  ;  inwardly,  a 
sharp  crest  which  circumscribes  the  external  contour  of  the  lacerated 
foramen  ;  above,  and  under  the  mastoid  process,  the  stylo-mastoid  ov pre-mastoid 
foramen,  the  external  orifice  of  the  aqueduct  of  Fallopius  ;  below,  the 
subuliform  (or  styloid)  process  for  the  attachment  of  the  stylo-staphyleus 
(tensor  palati)  muscle  and  the  Eustachian  tube  :  this  is  a  long,  thin,  and  pointed 
process  presenting,  at  its  base  and  within,  a  canal  which  enters  the  cavity  of  the 
tympanum,  and  which  is  incompletely  partitioned  by  a  small  bony  plate  into 
two  parallel  portions  :  in  the  centre,  the  liyoid  prolongation  or  vaginal process^^ 
a  little  cylindrical  eminence  surrounded  by  a  bony  sheath,  and  the  nKistoid 
protuberance  or  process,  a  slightly  salient,  smooth,  and  round  eminence 
hollowed  internally  by  numerous  cells,  which  form  part  of  the  middle  ear. 

The  several  small  and  very  remarkable  canals  which  pass  through  the 
tuberous  portion  of  the  temporal  bone,  will  be  noticed  when  the  nervous  and 
arterial  branches  they  ledge  are  described. 

*  This  is  the  analogue  of  the  mastoid  canal  in  Man. 

-  This  process  is  prokmged  by  a  cartilage  that  unites  it  to  the  sfijloid  hone. 


44  THE  BONES. 

Development. — The  tuberous  portion  of  the  temporal  bone  is  fleveloped 
from  two  principal  centres  of  ossification  which  are  consolidated  at  birth,  and 
which  are  often  described  as  two  distinct  portions :  the  one  as  the  petrous  or 
stony  portion,  the  other  as  the  mastoid  p>oriion. 

The  faces,  borders,  summit  and  inner  side  of  the  base  of  the  bone  are 
formed  by  the  ^;<?<ro«ts  part,  which  contains  the  cavities  of  the  internal  ear 
and  furnishes  the  inner  wall  of  the  middle  ear. 

The  mastoid  portion  constitutes  almost  entirely  the  base  of  the  temporal 
pyramid ;  to  it  belongs  the  external  auditory  canal,  the  mastoid  process,  the 
sheath  of  the  hyoid  prolongation,  and  the  styloid  process;  it  forms  the 
external  wall  and  circumference  of  the  case  of  the  tympanum. 

For  the  tuberous  portion  of  the  temporal  bone  there  are  also  two  small 
complementary  nuclei :  one  for  the  vaginal  process,  whose  base  is  united 
to  the  petrous  portion,  and  another  forming  the  ring  of  the  tympanum. 

Structure. — The  petrous  portion  is  the  hardest  mass  of  bone  in  the 
skeleton,  and  scarcely  contains  any  spongy  tissue,  except  at  the  centre  of  the 
mastoid  process  ;  in  the  mastoid  portion  it  may  be  said  not  to  exist. 

In  the  other  domesticated  animals,  the  tuberous  portion  of  the  temjioral 
bone  is  always  consolidated  with  the  squamous,  and  the  summit  of  the 
zygomatic  process  only  articulates  with  the  malar  bone. 

BOXES    OF    THE    FACE. 

The  face  is  much  more  extensive  than  the  cranium  in  the  majority  of  the 
domesticated  animals,  and  is  composed  of  two  jaws,  a  bony  apparatus  that  serves 
as  a  support  to  the  i^assive  organs  of  mastication — the  teeth.  The  superior 
or  anterior  jaw,  traversed  in  its  entire  length  by  the  nasal  cavities,  is  formed  by 
nineteen  wide  bones,  only  one  of  which,  the  vomer^  is  a  single  bone ;  the 
pairs  are :  the  superior  and  intermaxillaries  (or  premaxiUaries),  the  palate, 
pterygoid,  zygomatic,  lachrymal,  nasal,  and  superior  and  inferior  turhinated  hones. 
Of  these  only  four,  the  maxillaries,  are  intended  for  the  implant  ition  of 
the  teeth ;  the  others  form  the  union  between  the  cranium  and  the  suj^terior 
maxilla,  or  concur  in  the  formation  of  the  nasal  cavities.  The  lower  jaw  has 
for  its  base  a  single  bone,  the  inferior  maxilla  or  maxillary  hone. 

1.  Great  Super  maxilla,  or  Superior  Maxillary  Bone. 

This  bone,  the  most  extensive  in  the  upper  jaw,  is  situated  on  the 
side  of  the  face,  and  is  bordered  above  by  the  frontal',  palate,  zygomatic,  and 
lachrymal  bones ;  below,  by  the  premaxillary  bones  ;  in  front,  by  the  nasal 
bone  ;  behind  and  within,  by  that  of  the  opposite  side.  It  is  elongated 
vertically,  is  irregularly  triangular,  and  exhibits  two  faces,  two  horders,  and 
tioo  extremities. 

Faces. — The  external  face,  which  is  more  convex  in  the  young  than  the 
old  animal,  presents :  1,  On  the  level  of  the  fourth  and  lifth  molar  teeth,  a 
vertically  elongated  ridge  which  is  continued  above  with  the  inferior  border 
of  the  zygomatic  bone  ;  this  is  the  supermaxillary  spine  ;  2,  The  inferior 
orifice  of  the  supe7'maxillo-dental  canal,  or  infra-orhital  foramen. 

The  internal  face  concurs  in  forming  the  external  parietes  of  the 
nasal  cavities.  We  observe,  above  and  in  front,  a  deep,  wide,  and  diverticu- 
lated  excavation,  forming  part  of  the  maxiHary  sinus ;  above  and  behind,  a 
surface  roughened  by  tine  lamellaa  and  dentations  to  correspond  with  the 
palate  bone,  and  traversed  from  above  to  below  by  a  fissure  vvliich  forms, 
in  uniting  with  a  similar  fissure  in  the  latter  bone,  i\io  palatine  canal.  For 
the  remainder  of  its  extent  it  is  unequally  smooth,  covered  by  the  membrane 


THE  HEAD.  45 

of  the  nose,  and  divided  into  two  surfaces  by  a  sliglitly  vertical  and  sinuous 
crest  that  aftords  attachment  to  the  niaxiHary  turbinated  bone  :  the  anterior 
surface,  which  responds  to  the  middle  meatus  of  the  nasal  fossa,  shows  the 
lower  orifice  of  the  osseous  lachrymal  canal  continued  by  a  fissure  to  the  lower 
extremity  of  the  bone  ;  the  posterior  surface  belongs  to  the  inferior  meatus. 
This  face  presents,  near  its  inferior  border,  a  large  vertical  apophysis,  the 
jxdatine  ])rocess,  which  offers  an  anterior  slightly  concave  face,  funning  the 
floor  of  the  nasal  fossfe ;  a  posterior  face,  furrowed  by  small  fissures, 
perforated  by  fine  openings,  and  traversed  along  its  length  by  a  somewhat 
Avide  groove,  the  palatine  fissure,  which  commences  above  at  the  lower  orifice 
of  the  palatine  canal.  The  internal  border  of  this  process  articulates  with 
the  analogue  of  the  palatine  process  of  the  opposite  side. 

Borders. — The  anterior,  thin  and  convex,  is  divided  into  two  parts :  an 
inferior,  which  is  mortised  to  receive  the  external  border  of  the  nasal  bone 
and  the  external  process  of  the  premaxillary  ;  and  a  superior,  cut  in  a  wide 
bevel  at  the  expense  of  the  external  plate,  to  respond  to  tlie  lachrymal  and 
zygomatic  bones.  The  external  border  is  very  thick  and  hollowed  into  six 
large  quadrilateral  cavities,  named  alveoli,  in  which  are  implanted  the  molar 
teeth.  Above  the  last  alveolus  it  forms  a  rugged  eminence  designated  the 
alveolar  tuberosity  ;  below  the  first  it  becomes  thin  and  sharp,  and  constitutes 
part  of  the  interdental  space  which  separates  the  molar  from  the  incisor  teeth. 

Extremities. — The  superior  is  the  thickest,  and  represents  a  smooth 
rounded  protiiberance,  into  the  interior  of  which  tlie  maxillary  sinus  is 
prolonged.  Above  and  within  this  eminence,  is  a  wide  and  deeji  excavation, 
in  the  formation  of  which  the  palate  bones  participate.  This  is  the 
maxillary  hiatus,  situated  directly  opposite  the  orbital  hiatus.  At  the 
bottom  of  this  cavity  is  seen  the  nasal  foramen,  as  well  as  the  upper  orifice 
of  the  supermaxillo-dental  and  the  palatine  canals.  The  nasal  foramen 
belongs  to  the  palate  bone  and  enters  the  nasal  cavity.  The  super- 
maxillo-dental or  infra-orhital  canal  traverses  the  maxillary  sinus  in  passing 
above  the  roots  of  the  molar  teeth,  and  terminates  by  two  branches :  one, 
short  and  wide,  which  opens  on  the  external  surface  of  the  bone,  on  a 
level  with  the  third  molar ;  the  other,  very  narrow,  continues  the  course  of 
the  canal  in  the  thickness  of  the  bone,  and  is  prolonged  by  several  small 
very  fine  branches  into  the  premaxillary  bone.  The  palatine  canal,  channeled 
between  the  supermaxillary  and  the  palate  bone,  extends  from  the  maxillary 
hiatus  to  the  palatine  fissure. 

The  inferior  extremity  presents  a  cavity  which  forms  the  alveolus  of  the 
tusk  by  uniting  with  a  similar  space  in  the  premaxillary  bone. 

Structure  and  development. — This  bone  is  developed  from  a  single  nucleus, 
and  is  the  more  spongy,  particularly  towards  the  alveolar  border  and  the 
superior  extremity,  as  the  animal  is  young. 

2.  PremaxiUnry,  Intermaxillary,  Anterior  Maxillary  or  Incisive  Bone. 

This  bone  occupies  the  inferior  extremity  of  the  head,  and  is  composed  of 
a  tldcl:  prismatic  portion,  lengthened  superiorly  by  two  long  processes. 

Tliich  portion  or  base. — This  presents  a  solid  mass  ■svith  three  faces  :  an 
external  or  labial,  smooth  and  convex ;  an  internal,  denticulated  for  union 
with  the  opposite  bone,  and  traversed  from  before  to  behind  by  an  inflexed 
fissure,  which  forms,  with  an  analogous  one  in  the  other  premaxillary, 
the  incisive  canal  or  foramen  ;  the  third  ov  posterior,  also  called  the  buccal,  is 
slighty  concave,  and  shows  the  continuation  of  the  palatine  fissure,  which 


46 


TEE  BONES. 


Fig.  21. 


opens  into  the  incisive  foramen.  Tliese  three  faces  are  separated  by  as 
many  borders :  ttco  internal,  limiting  before  and  behind  the  corresponding 
face  ;  and  an  external,  separating  the  labial  from  the  buccal  face.  The  latter 
only  merits  notice  ;  it  is  very  thick,  and  is  divided  into  two  parts  :  an 
inferior,  which  describes  a  curved  line  with  the  concavity  upwards,  and 
is  hollowed  by  three  alveoli  to  receive  tlie  incisor  teeth ;  another,  the 
superior,  is  straight,  vertical,  and  somewhat  sharp,  and  forms  a  part  of 
the  dental  interspace.  It  is  limited  above,  near  the  base  of  the  external 
process,  by  a  cavity  for  the  formation  of  the  alveolus  of  the  tusk. 

Processes. — These  are  distinguished  as  ex- 
ternal and  internal.  The  first,  the  longest  and 
strongest,  is  flattened  on  both  sides ;  its  ex- 
ternal face  is  smooth  and  continued  with  that 
of  the  thick  portion  of  the  bone ;  its  internal 
face  is  covered  by  the  mucous  membrane  of 
the  nose  ;  the  anterior  border  is  smooth  and 
rounded ;  the  posterior,  denticulated  to  re- 
spond to  the  supermaxillary  bune,  is  in  con- 
tact with  the  external  border  of  tlie  base  ;  its 
summit  is  thin,  and  is  insinuated  between  the 
latter  and  the  nasal  bone.  Tlie  internal  pro- 
cess, the  smallest,  is  flattened  from  before  to 
behind,  and  forms  a  very  thin  tongue  of  bone, 
separated  from  the  other  portions  by  a  nar- 
row and  very  deep  notch  named  the  incisive 
opening  or  cleft.  Its  inferior  face  constitutes  a 
small  portion  of  the  floor  of  the  nasal  fossae ; 
the  posterior,  continuous  with  the  same  face 
of  the  principal  mass  of  the  bone,  forms  part 
of  the  palatine  roof;  its  external  border  cir- 
cumscribes, inwardly,  the  incisive  opening  ; 
the  internal  is  united  by  dentated  suture  with 
the  opposite  bone. 

Structure  and  development. — It  is  a  spongy 
bone,  developed  from  a  single  nucleus. 

3.  Palate  Bones. 

The  palate  hones  are  situated  between  the 
supermaxillaries,  at  the  margin  of  the  guttural 
opening  of  the  nasal  cavities,  and  are  articu- 
lated with  the  sphenoid,  ethmoid,  vomer, 
frontal,  and  pterygoid  bones.  Elongated  from 
above  to  below,  flattened  laterally,  and  curved 


POSTERIOR   ASPECT   OF   UORSE  S 
SKULL. 

1,  Occiiiital  protuberance;  2, 
Foraniea  mat^num ;  3,  3,  Oc- 
cipital condyles;  4,  4,  Styloid 


processes;  5,  5,  Petrous  bone;  6,  Basilar  process;  7, 
Pterygoid  fissure  of  the  sphenoid  bone;  8,  Foramen  lacerum  ;  9,  9,  Supra-coudyloid,  or 
anterior  mastoid  process;  10,  10,  Articular  eminence,  or  temporal  condyle;  11,  Body  ot 
sphenoid  bone;  12,  Pterygoid  process;  13,  Ethmoid  bone;  14,  Temporal  bone  and  sphe- 
noidal suture;  15,  Lachrymal  bone;  16,  Vomer;  17,  Malar  bone;  18,  Maxillary  tube- 
rosity, 19,  Posterior,  or  guttural  opening  of  the  nose;  20,  Palate  bone;  21,  Palatine 
styloid  process ;  22,  Palato-maxillary  foramen;  23,  Palatine  process  of  superior  maxil- 
lary bone  with  suture  ;  24,  Ditto  of  premaxillary  bone ;  25,  Premaxillary  bone  ;  26, 
Upjier  incisor  teeth;  27,  Point  of  junction  of  the  premaxillary  with  the  superior  maxil- 
lary bone  I  28,  Upper  molar  teeth — young  mouth. 


THE  HEAD.  47 

towards  each  other  at  their  inferior  extremity,  which  is  flattened  from 
before  to  behind,  these  bones,  though  irregular  in  shape,  ofter  for  study 
two  faces,  two  borders,  and  two  extremities. 

Faces. — The  external  face  of  the  paLate  bone  is  divided  into  three  frac- 
tions, a  superior,  or  orbital,  an  inferior,  or  palatine,  and  a  middle,  or  articular. 
The  first  is  smooth  and  slightly  excavated,  and  participates  in  the  forma- 
tion of  the  maxillary  hiatus  ;  it  shows  a  small  fissure,  the  staplujloid,  which 
reaches  the  palatine  fraction  in  passing  between  the  posterior  border  of  the 
bone  and  the  alveolar  tuberosity.  The  second  is  not  extensive,  and  looks 
backwards  in  consequence  of  the  antero-posterior  flattening  which  the  bone 
presents  at  its  inferior  extremity ;  it  forms  part  of  the  roof  of  the  palate. 
The  third  presents  a  lamellar  and  denticulated  surface  which  corresponds  to 
a  similar  face  on  the  supcrmaxillary  bone,  and  is  channeled  from  above  to 
below  by  the  internal  fissure  of  the  palatine  canal. 

The  internal  face,  smooth  and  concave,  forms  part  of  the  external  wall 
and  the  floor  of  the  nasal  fossa. 

Borders. — The  anterior  is  indented,  near  its  superior  third,  by  a  deep 
notch,  which  is  often  converted  into  a  foramen,  the  nasal.  Below  this  notch 
the  bone  is  thin  and  denticulated  for  union  with  the  supcrmaxillary  bone ; 
above,  its  two  plates  separate  widely  from  one  another,  giving  rise  to  a 
very  spacious  cavity  which  forms  part  of  the  sphenoid  sinus.  The  posterior 
border  presents,  above,  a  rugged  crest  called  the  palatine,  flattened  from  side 
to  side,  bent  outwards,  and  bordered  at  its  base  and  inwards  by  a  very 
narrow  synarthrodia!  sm-face  which  responds  to  the  pterygoid  bone.  It  is 
smooth  and  concave  in  its  inferior  half,  and  forms,  with  that  of  the  opposite 
side,  a  parabolic  arch  which  circumscribes,  below  and  at  the  side,  the  double 
guttural  orifice  of  the  nasal  cavities. 

Extremities. — The  superior,  flattened  on  both  sides,  is  bevelled  on  the 
external  side  to  articulate  with  the  subsphenoidal  process.  The  inferior, 
flattened  from  before  to  behind,  is  cm-ved  inwards  and  united  by  simple 
suture  with  that  of  the  opposite  bone. 

Structure  and  development. — This  is  a  very  compact  bone,  developed  from 
a  single  centre  of  ossification. 

4.  Pterygoid  Bone.^ 

A  small  and  very  narrow  bone,  elongated  from  above  to  below,  flattened 
on  both  sides,  and  situated  on  the  inner  aspect  of  the  subsphenoidal  process, 
but  external  to  the  vomer. 

Its  external  face  is  in  contact  with  the  palate  and  sphenoid  bones ; 
the  internal  is  smooth  and  covered  by  the  pharyngeal  mucous  membrane. 
Its  superior  extremity  is  tapering,  and  concurs  in  forming  the  vidian  canal ; 
the  inferior  is  thickened  into  a  small  pointed  process  (the  hamidar  process), 
whose  apex,  directed  backwards,  ofiers  outwardly  a  groove  which  serves  as  a 
pulley  to  the  tendon  of  the  tensor  palati.  This  bone  is  composed  entirely 
of  compact  tissue,  and  is  developed  from  a  single  centre  of  ossification, 

5.  Zygomatic  Bone. 

This  bone,  also  designated  the  malar  and  jugal  bone,  is  elongated  from 
above  to  below,  flattened  on  both  sides,  and  irregularly  triangidar  in  shape; 
it  is  situated  on  the  side  of  the  face,  and  articulates  with  the  supcrmaxillary, 

'  Thi5  bone  is  the  representative  of  the  internal  icing  of  the  pterygoid  process  ia  Man. 


48  THE  BONES. 

lachrymal,  and  temporal  bones.  It  is  described  as  having  two  faces,  two 
borders,  a  base,  and  a  summit. 

Faces. — The  external  face  comprises  two  portions  separated  from  each 
other  by  a  semicircular  ledge  that  extends  from  the  summit  to  the  middle  of 
the  anterior  border  of  the  bone,  and  concurs  to  form  the  outer  margin  of  the 
orbit.  The  anterior  portion,  smooth  and  concave,  belongs  to  the  orbital 
cavity.  The  posterior,  more  extensive,  is  also  smooth  and  slightly  convex. 
The  internal  face  is  excavated  in  its  central  part,  which  corresponds  to  the 
maxillary  sinus.  On  its  margin  it  shows  dentations  and  lamellae  for  articu- 
lation with  the  supermaxillary  bone. 

Borders. — The  anterior,  thin  and  denticulated,  is  joiaed  to  the  lachrymal 
bone.  The  posterior,  or  masseteric  border,  is  thicker,  and  constitutes  a 
roughened  crest,  the  zygomatic  ridge,  which  is  continued  above  with  the 
posterior  border  of  the  process  of  the  same  name,  and  below  with  the 
maxillary  spine.^ 

Base  and  summit. — The  base,  very  thin,  is  united  to  the  supermaxillary 
bone.  The  summit,  flattened  from  before  to  behind  and  bevelled  on  its 
anterior  face,  joins  the  zygomatic  process,  and  forms  with  it  the  jugal  bridge 
or  zygomatic  arch. 

Structure  and  development. — This  bone  is  rather  spongy  in  its  upper  part, 
and  is  developed  from  a  single  nucleus  of  ossification. 

6.  LacJirymal  Bone. 

A  small,  thin,  and  very  light  bone,  bent  on  itself  at  a  right  angle,  it  is  situ- 
ated beneath  the  orbit,  which  it  aids  in  forming,  and  is  wedged  between  the 
frontal,  nasal,  supermaxillary,  and  zygomatic  bones.  It  is  studied  on  its 
external  and  internal  faces  and  circumference. 

Faces. — The  external  is  divided  into  two  regions,  superior  and  inferior, 
by  a  curved  crest  which  forms  part  of  the  orbital  margin,  and  is  provided 
with  notches,  which  are  variable  in  their  form  and  number.  The  superior 
region,  named  the  orbital,  because  of  its  situation  in  the  orbit,  is  slightly 
concave  and  smooth.  It  presents,  near  the  orbital  margin,  the  orifice  of  the 
lachrymal  duct,  which  traverses  the  maxillary  sinus  and  opens  on  the  internal 
face  of  the  supermaxillary  bone,  where  it  is  continued  by  a  fissure  ;  behind 
this  is  the  lachrymal  fossa.  The  inferior  ov  facial  region  is  slightly  bulging, 
and  provided  sometimes  with  a  tubercle  of  insertion,  the  lachrymal  tubercle. 
The  internal  face  is  employed,  for  the  whole  of  its  extent,  in  the  formation  of 
the  walls  of  the  maxillary  and  frontal  sinuses ;  it  exhibits  a  cylindrical 
prominence  produced  by  the  bony  tube  of  the  lachrymal  duct. 

Circumference. — This  is  very  irregular  and  denticulated  to  respond  to 
the  neighbouring  bones. 

Structure  and  development, — This  bone  is  entirely  compact,  and  is 
develoj)ed  from  a  single  nucleus  of  ossification. 

7.  Nasal  Bones. 

Situated  on  the  anterior  aspect  of  the  head,  these  bones  articulate  with 
each  other  in  the  median  line,  and  are  fixed  between  the  frontal,  lachrymal, 
and  supermaxillary  bones;  they  are  triangular  in  shape,  elongated  from 
above  to  below,  flattened  from  before  to  behind,  and  offer  for  study  two  faces, 
two  borders,  a  base,  and  a  summit. 

Faces. — The   external  or  anterior  face,  larger  above  than  below,  is  convex 

'  The  designation  of  ztjgomatlo  crest  is  often  given  to  these  three  parts  collectively. 


THE  HEAD. 


49 


from  side  to  side  and  almost  smootli.  The 
^wstcrior,  internal,  or  nasal  face  exhibits  a  ver- 
tical crest  passing  along  the  external  border 
of  the  bone,  which  gives  attachment  to  the 
nated  portion  of  the  ethmoid;  at  its  supe- 
rior extremity  this  crest  bifurcates,  and  between 
its  two  branches  shows  a  concave  surface  which 
forms  part  of  the  frontal  sinus.  For  the 
remainder  of  its  extent  the  internal  face  is 
smooth,  and  covered  by  the  mucous  membrane 
of  the  nasal  fossa ;  it  is  also  excavated  into  a 
channel  to  form  the  superior  meatus  of  this 
cavity. 

Borders. — The  external  border  is  very  thin 
in  its  upper  two-thirds,  and  articulates  with 
the  lachrymal  bone,  the  anterior  border  of 
the  supermaxillary,  and  the  uj^per  extremity 
of  the  px'emaxillary  bones.  In  its  lower  third 
it  becomes  isolated  from  the  latter  bone,  in 
forming  with  the  anterior  border  of  its  large 
process  a  very  acute  re-entering  angle  whose 
opening  looks  downwards.  The  internal  border 
is  denticulated  to  correspond  with  the  opjjosite 
bone. 

JBase  and  Summit. — The  base  occupies  the 
superior  extremity  of  the  bone ;  it  describes 
a  curved  line  with  the  convexity  above,  and  in 
imiting  on  the  median  line  with  that  of  the 
opposite  bone,  forms  a  notch  similar  to  that 
of  the  heart  figured  on  playing  cards ;  it  is 
bevelled  at  the  expense  of  the  internal  j^late  to 
articulate  with  the  frontal  bone.  The  summit 
of  the  two  nasal  bones,  which  is  pointed, 
constitutes  the  nasal  prolongation:  the  name 
given  to  a  single  triangular  process  which 
comjirises  all  that  portion  of  the  nasal  bones 
separated  from  the  premaxillaries  by  the  re- 
entering angle  before  mentioned. 

Structure  and  development. — Almost  entirely 
compact  in  structure,  it  is  developed  from  a 
single  centre. 

8.  Turbinated  Bones. 

The  turbinated  bones,  two  on  each  side, 
represent  two  irregular  bony  columns,  wider 
above  than  below,  compressed  laterally,  hol- 
lowed internally,  and  lying  vertically  side  by 
side  on  the  external  wall  of  the  nasal  fossa, 
which  they  divide  into  three  meatuses  or  pas- 
sages. 

Tliey  are  distingiiished  into  anterior  and 
posterior  turbinated  bones. 

The  anterior   or   superior,  also  named  the 


Ficr.  22. 


ANTERO-POSTEEIOR  AKD  VERTICAL 
SECTION    OF  THE  HORSE's  HEAD. 

1,  Condyloid  foramen  ;  2,  Parietal 
protuberance  ;  3,  Internal  audi- 
tory hiatus  ;  4,  Cerebral  cavity ; 
5,  Cerebellar  cavity ;  6,  Supe- 
rior border  of  the  perpendicular 
plate  of  the  ethmoid  bone  (crista- 
galli  process);  7,  Ethmoidal 
volutes — nasal  face  ;  8,  Vestiges 
of  the  right  frontal  sinus ;  9, 
Ditto  of  the  sphenoidal  smus ; 
10,  Pterygoid  process;  11,  Eth- 
moidal turbinated  bone;  12, 
Jlaxillary  turbinated  bone;  lo, 
Crest  of  the  supermaxillary 
bone  to  which  the  latter  is  fixed  ; 
l-t,  Tomer. — a.  Orifice  of  com- 
munication between  the  nasal 
cavity  and  the  sinus. 


50 


Fig.  23. 


THE  BONES. 

ethmoidal,  is  formed  by  a  very  tliin  plate 
of  compact  tissue,  fragile  and  like  jiapyrus, 
fixed  by  its  anterior  border  to  the  internal 
crebt  of  the  nasal  bone,  and  rolled  on 
itself,  from  before  to  behind,  in  the  same 
manner  as  the  cells  of  the  ethmoid  bone. 
Above,  it  is  confounded  with  the  last- 
named  bone,  of  which  it  is  only,  properly 
speaking,  the  most  anterior  volute.  At  its 
inferior  extremity,  it  is  jprolonged  by  a 
fibro-cartilaginous  framework  to  the  ex- 
ternal orifice  of  the  nose. 

Its  internal  cavity  is  partitioned  by  a 
transverse  plate  into  two  portions:  the 
supei'ior  compartment  forms  part  of  the 
frontal  sinus  ;  the  inferior  is  subdivided  by 
other  small  lamellas  into  a  variable  number 
of  cells  which  communicate  with  the  nasal 
cavity.  This  bono,  developed  from  a 
single  nucleus,  is  ossified  at  the  same  time, 
and  in  the  same  manner,  as  the  ethmoidal 
cells.  Before  birth,  it  is  already  intimately 
consolidated  with  the  nasal  bone. 

The  posterior,  inferior,  or  maxillary 
turbinated  bone  resembles  the  first,  except 
in  some  particulars.  Thus,  its  bony  or 
proper  portion  is  not  so  long  or  volu- 
minous, while  its  cartilaginous  part  is,  on 
the  contrary,  more  developed.  It  is  at- 
tached, by  its  jiosterior  border,  to  the  ver- 
tical and  sinuous  crest  of  the  super- 
maxillary  bone,  and  is  rolled  from  behind 
to  before,  or  in  an  inverse  direction  to  the 
other.  It  has  no  connection  with  the 
ethmoid,  and  its  superior  cavity  forms 
part  of  the  inferior  maxillary  sinus.  It 
is  late  in  becoming  ossified,  and  is  scarcely 
imited  in  a  definite  manner  to  the  max- 
illary bone  until  the  horse  is  about  a  year 
old. 

The  meatuses  are  distinguished  into 
anterior  or  superior,  middle,  and  posterior 
or  inferior.  The  first  passes  along  the 
front  of  the  ethmoidal  turbinated  bone ; 
the  second  separates  the  two  turbinated 
bones,  and  presents,  near  its  superior 
extremity,  the  opening  communicating 
between  the  sinuses   and  the  nasal  cavi- 

rior  of  the  great  ethmoidal   cell;   12, 

12,  Bottom  of  the  maxillary  sinuses  communicating  witli  the  sphenoidal  sinuses;  13,  Supe- 
rior maxillary  sinus;  14,  Inferior  maxillary  sinus;  14',  Superior  compartment  of  the  max- 
illary turbinated  bone,  forming  part  of  the  latter  sinus;  15,  Section  of  the  supermaxillo- 
dental  canal;  16,  Channel  of  the  vomer;  17,  Internal  process,  or  point  of  the  premax- 
illary  bone. 


LONGITUDINAL  AND  TRANSVERSK  SEC- 
TION OF  THE  horse's  HEAD,  SHOW- 
ING THE  FLOOR  OF  THE  CRANIAL 
AND  NASAL  CAVITIES,  WITH  THE 
MAXILLARY    SINUSES. 

Condyloid  foramen  ;  2,  Section  of  the 
parieto-tempoi'al  canal ;  3,  Occipito- 
spheno-temporal  hiatus ;  4,  Carotid 
notch  ;  4',  Maxillary  notch.— a, 
Supermaxillary  fissure  ;  6,  Cavernous 
fissure ;  5,  Origin  of  the  supersphe- 
noidal  canals.  — c,  Sella  turcica;  6, 
Optic  fossa;  7,  Portion  of  the 
crista-galli  process;  8,  Cribriform 
plate  of  the  ethmoid  bone ;  9,  Per- 
pendicular plate  of  the  same  bone ; 
10,  10,  Its  lateral  masses;   11.  Inte- 


THE  HEAD.  51 

ties.^     The  third  is  situated  behind  the  maxillary  turbinated  bone,   and 
is  confounded  with  tlic  floor  of  the  nasal  fossa. 

The  turbinated  bones  are  essentially  destined  to  furnish  the  membrane 
of  the  nose  with  a  vast  surface  of  development.  This  membrane,  indeed, 
covers  their  entire  suiierticies,  and  even  penetrates  the  anfractuous  cells  of 
their  lower  compartment. 

9.   Vomer. 

This,  a  single  bone,  elongated  from  above  to  below,  flattened  on  both 
sides,  and  extending  on  the  median  line  from  the  body  of  the  sphenoid  to 
the  premaxillary  bone,  offers  for  study  tivo  lateral  faces,  tioo  borders,  and 
tivo  extremities. 

The  faces  are  smootli,  plane,  and  covered  by  the  nasal  membrane.  The 
anter.ior  border  i^  channeled  ft)r  the  whole  of  its  length  by  a  deep  groove 
■which  receives  the  posterior  border  of  the  cartilaginous  sejitum  of  the 
nose.  The  posYer/or  border  is  sharp  and  smooth  in  its  upper  half,  which 
separates  the  two  guttural  openings  of  the  nasal  cavities :  it  is  thick  and 
slightly  denticulated  for  the  remainder  of  its  extent,  and  rests  on  the 
median  suture  resulting  from  the  union  of  the  two  supermaxillary  bones. 
The  superior  extremity  is  provided,  in  its  middle,  with  a  notch  which  divides 
it  into  two  lateral  jirolongations  shaped  like  a  cat's  ears ;  it  articulates 
with  the  inferior  sphenoid,  ethmoid,  palate,  and  pterygoid  bones.  The 
inferior  extremity  rests  on  the  prolongations  of  the  incisive  bones. 

This  bone  is  entirely  compact,  and  is  developed  from  one  centre  of 
ossification. 

10.  Inferior  Maxillary  Bone. 

The  maxillary  hone  is  not  consolidated  with  any  of  the  preceding  bones, 
and  is  only  united  to  two  of  them,  the  temporals,  by  diarthrodial  articula- 
tion. It  is  a  considerable  bone,  situated  behind  the  upper  jaw,  and  composed 
of  two  symmetrical  branches,  which  are  flattened  on  both  sides,  wider 
above  than  below,  curved  for\\  ards  in  their  upper  third,  joined  at  their  lower 
extremities,  and  separated  superiorly  so  as  to  leave  a  wide  gap  between 
them,  like  the  letter  V  in  shape,  called  the  intramaxillary  space.  Each 
offers  for  study  two  faces,  two  borders,  and  two  extremities. 

Faces. — The  external  face  of  the  maxillary  branches  is  smooth  and 
rounded  in  its  inferior  two-thirds,  and  transformed  superiorly  into  a 
rugged  surface,  in  which  is  implanted  the  fibres  of  the  masseter  muscle. 
The  interned  face  presents,  in  the  corresponding  point,  an  excavated  surface 
on  which  is  remarked  the  superior  orifice  of  the  maxillo- dental  canal,  a  long 
channel  which  descends  between  the  two  plates  of  the  branch,  passing  under 
the  roots  of  the  molar  teeth,  and  insensibly  disappearing  in  the  body  of  the 
bone  after  being  widely  opened  externally  by  the  mental  (or  anterior  maxillary) 
foramen.  In  its  inferior  two-thirds,  the  internal  face  is  smooth,  nearly 
plane,  and  shows  nothing  very  remarkable.  Near  the  alveolar  border  there 
is  a  slightly-projecting  line — the  myloid  ridge ;  and  quite  below,  or  rather 
at  the  very  summit  of  the  re-entering  angle  formed  by  the  separation  of 
the  branches,  there  is  a  slight  rugged  excavation  confounded  with  that  of  the 
opposite  branch,  and  named  the  genial  surface. 

Borders. — The  anterior,  also  named  the  alveolar  border,  exhibits  for 
study  a  straight  or  inferior,  and  a  curved  or  superior  portion.  The  first  is 
hollowed  by  six  alveoli  to  receive  the  inferior  molar  teeth. 

'  The  two  turbinated  bones,  in  being  applied  ngainst  the  excavation  on  the  inner 
face  of  the  supermaxillary,  almost  entirely  close  it,  only  leaving  between  them  a  vertical 
i-lit  which  constitutes  the  opening  mentioned  above. 


52 


TEE  BONES. 


The  second,  thinner,  concave,  and  rugged,  serves  for  muscular  insertion. 
The  posterior  border  is  also  divided  into  straight  aud  curved  portions.  The 
latter  is  convex,  thick,  rugged,  and  margined  on  each  side  by  an  uneven 
lip ;  the  first  is  regularly  rectilinear,  so  that  all  its  points  rest  at  the  same 
time  on  a  horizontal  plane;  it  is  thick  and  roviuded  in  the  young  animal, 
but  becomes  sharp  with  age  ;  an  oblique  aud  transverse  fissure — the  maxillary 
— separates  it  from  the  curved  part.  The  union  of  these  two  portions  forms 
the  angle  of  the  jaw. 

Extremities. — The  superior  extremity  lias  two  eminences  :  a  condyle, 
and  a  long  non-articular  process  named  the  coronoid  process.  The  condyle  is 
elongated  transversely,  aud  convex  in  its  two  diameters;  it  responds,  through 
the  medium  of  a  fibro-cartilaginous  disc,  to  the  articular  surface  of  the  zygo- 
matic process.  The  coronoid  process  is  situated  in  front  of  the  condyle,  from 
which  it  is  separated  by  a  division  called  the  sigmoid  or  corono-condyloid  notch  ; 
it  is  flattened  on  both  sides,  and  curved  backwards  and  slightly  inwards. 


Fig.  24, 


INFERIOR   MAXILLA. 

1,  Mental  foramen ;  1',  Superior  orifice  of  the  maxillo-dental  canal ;  2,  Surface  ot 
implantation  for  the  masseter  muscle ;  3,  Myloid  ridge  j  4,  Coronoid  process ; 
5,  Condyle. 

From  the  union  of  the  branches  of  the  maxillary  bono  at  their  inferior 
extremity  results  a  single  piece,  flattened  before  aud  behind,  and  widened 
like  a  spatula,  which  has  been  designated  the  body  of  the  bone.  This  merits 
a  special  description. 

Its  form  allows  us  to  divide  it  into  an  anterior  or  luccnl  face,  a  p)osterior 
or  labial  face,  and  a  circumference.  The  anterior  face  is  smooth  and  concave, 
is  lined  by  the  buccal  mucous  membrane,  and  supports  the  free  extremity 
of  the  tongue.  The  posterior  face  is  convex,  more  extensive  than  the 
preceding,  and  continuous  with  the  external  face  of  the  branches ;  it  presents : 
1,  On  the  median  line,  a  slight  crest  or  small  groove,  traces  of  its  being 
originally  separated  into  two  pieces ;  2,  On  the  sides  and  above,  the  mental 
foramen,  the  inferior  orifice  of  the  maxillo-dental  canal.  On  a  level  with 
this  foramen,  the  bone  very  markedly  contracts  to  form  the  nech.  The 
circumference  describes  a  parabolic  curve,  the  concavity  being  uppermost, 
and  joins,  by  its  extremities,  the  anterior  border  of  each  branch.  It  is 
excavated  in  its  middle  part  by   the  six  alveoli  for  the  lodgment  of  the 


TEE  HEAD. 


53 


inferior  incisors,  and  behind  these,  in  male  animals  only,  there  is  an 
additional  alveolus  for  the  tusk.  The  portion  included  on  each  side  between 
the  last  incisor  and  first  molar,  forms  a  more  or  less  sharp  ridge,  which 
constitutes  the  inferior  interdental  space  or  bars. 

Structure  and  development. — Formed,  like  all  the  flat  bones,  by  two 
compact  plates  separated  by  spongy  tissue,  the  inferior  maxilla  is  developed 
from  two  centres  of  ossification,  which  correspond  to  each  branch,  and  which 
coalesce  some  time  after  birth. 

11. — The  Hyoid  Bone. 

The  hjoid  bone  constitutes  a  small  and  special  bony  apparatus  which 
serves  to  support  the  tongue,  as  well  as  the  larynx  and  pharynx ;  its 
description  is  placed  immediately  after  that  of  the  bones  of  the  head 
because  of  its  connection  with  that  region,  it  being  situated  between  the  two 
branches  of  the  supermaxillary  bone,  and  suspended  to  the  base  of  the  cra- 
nium in  an  oblique  direction  from  above  to  below,  and  from  before  to  behind. 

This  apparatus  is  comiwsed  of  seven  distinct  pieces,  arranged  in  three 
series :  a  middle,  constituted  by  a  single  bone,  and  named  the  body  ;  two 
lateral,  forming  two  quasi-parallel  branches,  to  the  extremities  of  which  the 
body  is  articulated. 

Body. — The  body  of  the  hyoid  resembles  a  fork  with  two  prongs.  It 
presents :  1,  A  middle  part  flattened  above  and  below,  and  consequently  pro- 
vided with  a  sujjerior  and  an 
inferior  face  ;  2,  A  single  and 
long  prolongation  flattened 
on  both  sides,  which  is  de- 
tached from  the  middle  part, 
and  directed  forward  and 
downward  to  plunge  into  the 
muscular  tissue  of  the 
tongue :  this  is  the  anterior 
appendix  of  the  hyoideal  body ; 
3,  Two  lateral  cornua,  thyroid 
cornua,  or  great  cornua,  pro- 
jecting backwards  and  up- 
wards, articulating  by  their 
extremities  with  the  thyroid 


HYOID   BONE. 

1,  1,  Superior  extremity  of  the  styloid  bones,  2,  Angle 
described  by  their  posterior  border ;  3,  3,  Styloid 
bones ;  4,  4,  Extremities  of  the  thyroid  cornua ;  5, 
Articular  surface  of  the  body  corresponding  with  the 
small  branches ;  6,  Anterior  appendix  of  the  body ; 
7,  7,  Small  branches,  or  styloid  cornua. 


cartilage  of  the  larynx,  and  offering,  at  their  point  of  union  with  the 
middle  part,  two  convex  diarthrodial  facets  looking  upwards,  and  corre- 
sponding with  the  styloid  cornua.  The  body  of  the  hyoid  bone  is  developed 
by  three  centres  of  ossification,  a  middle,  and  two  lateral  for  the  cornua. 

Branches. — The  three  pieces  composing  these  are  articulated  end  to 
end,  by  means  of  a  cartilaginous  substance  that  joins  them  together ;  they 
are  of  very  unequal  dimensions.  The  first,  which  is  in  relation  with  the 
body,  is  of  medium  size,  and  is  named  the  styloid  cornu,  small  cornii,  or  small 
branch.  The  second,  termed  the  styloid  nucleus,  is  the  smallest.  The  third, 
the  largest,  constitutes  the  styloid  process,  or  bone,  or  great  branch. 

1.  The  styloid  cornu  is  a  small  cylindrical  piece  bearing  a  concave 
diarthrodial  surface  on  its  inferior  extremity  to  unite  it  to  the  body  ;  it  is 
very  spongy,  and  is  developed  from  two  ossifying  centres,  one  of  which,  the 
epiphysary,  is  for  the  inferior  extremity. 

2.  The  styloid  nucleus,  which  is  often  absent,  is  imbedded  in  the  uniting 
cartilaginous  substance. 

Y 


54  THE  BONES. 

3.  The  stijlokl  hone,  or  great  hyoideal  branch,  is  long,  tliin,  flcattened 
on  both  sides,  and  dii-ectcd  obliquely  from  above  to  below,  and  before  to 
behind  ;  it  presents  two  faces,  two  borders,  and  two  extremities.  The  faces 
— an  external  and  internal — are  marked  by  some  few  imprints.  The 
anterior  border  is  sharp  and  slightly  concave  in  its  upper  third.  The 
posterior  border  is  thicker,  and  is  divided  into  two  portions  :  a  superior  or 
horizontal,  which  is  very  short,  and  an  inferior  or  vertical,  much  more 
extensive.  The  angle  they  form  at  their  point  of  junction  presents  a 
salient,  and  more  or  less  roughened,  tuberosity.  The  superior  extremity  is 
united  to  the  hyoideal  prolongation  of  the  temporal  bone  by  means  of  a 
cylindrical  fibro-cartilage.  By  its  inferior  extremity,  the  styloid  hone  is 
united  either  to  the  styloid  nucleus  or  the  styloid  cornu,  forming  a  sharp 
elbow  directed  forwards.  The  styloid  bone,  developed  from  a  single 
centre  of  ossification,  is  almost  entirely  formed  of  compact  tissue. 

OF    THE    HEAD    IN    GENERAL. 

From  the  union  of  all  the  bones  which  constitute  the  cranium  and  face 
results  a  quadrangular  pyramid,  whose  summit  is  inverted,  wliich  it  is 
necessaiy  to  study  as  a  whole.  We  will  pass  in  review,  successively,  its 
four  faces,  its  base,  and  its  summit. 

Anterior  jPace.— The  anterior  aspect  of  the  head  has  the  parietal,  frontal, 
and  nasal  bones  for  its  base.  Superiorly,  it  inclines  backwards  and  offers, 
on  each  side  of  the  parietal  ridges,  two  bulging  surfaces  which  form  part 
of  the  temporal  fossse.  For  the  remainder  of  its  extent,  it  presents  a  plane 
surface  which  forms  the  base  of  the  forehead  and  the  middle  portion  of 
the  face.  Wide  above,  this  surface  gradually  tapers  to  the  extremity  of  the 
nasal  spine.     In  well-formed  animals,  it  is  as  straight  and  wide  as  j)ossible. 

Posterior  Face. — This  face,  which  is  extremely  irregular,  presents : 
above,  the  basilar  process,  the  lacerated  foramina,  and  the  base  of  the 
tuberous  portion  of  the  temporal  bones ;  then  the  intramaxillary  space, 
and,  at  the  bottom  of  this,  the  body  of  the  sphenoid  bone,  vidian  fissure, 
superior  orifice  of  the  subsphenoidal  canal,  sphenoidal  process,  palatine 
ridges,  pterygoid  bones,  guttural  openings  of  the  nasal  cavities  sejiarated 
from  one  another  by  the  posterior  border  of  the  vomer,  roof  of  the  palate, 
incisive  openings,  and  the  incisive  foramen. 

Lateral  Faces. — These  exhibit :  behind,  the  external  face  of  the  maxillary 
branches ;  before,  a  surface  more  or  less  convex,  though  sometimes  hollow 
in  old  animals,  presenting  at  its  middle  the  inferior  orifice  of  the  maxillo- 
dental  canal,  and  forming  the  base  of  tlie  lateral  parts  of  the  face ;  above, 
the  zygomatic  ridge  and  arch,  the  orhit.  and  tlie  temporal  fossa.  These 
two  cavities,  in  the  formation  of  which  many  bones  particijjate,  have  been 
hitherto  merely  indicated  ;  this  is  the  place  for  giving  them  a  more  detailed 
description. 

The  orbit  or  orbital  cavity  is  irregulai'ly  circiilar  in  outline,  and 
circumscribed  by  the  orbital  process  of  the  frontal  bone,  the  lachrymal  and 
malar  bones,  and  the  summit  of  the  zygomatic  process.  At  the  bottom, 
which  shows  the  maxillary  and  orbital  hiatus,  it  is  confounded,  in  the 
skeleton,  with  the  temporal  fossa.  ^  It  lodges  the  globe  of  the  eye  and 
the  muscles  which  move  it.     Some  organs,  accessory  to  the  visual  apparatus, 

'  A  fibrous  membrane,  the  ocular  sheath,  isolates  it  from  the  temporal  fossa  in  the 
majority  of  mammifennis  animals.  Only  in  Man  and  the  quadrumana  baa  the  orbital 
cavity  complete  bony  walls. 


THE  HEAD. 


55 


such  as  the  Lichrymal  gland  and  the  membrana  nictitans,  are  also  contained 
in  this  cavity. 

The  temporal  fossa  surmounts  the  orbit,  and  is  incompletely  separated 
from  it  by  the  orbital  arch  (or  process^.  Oval  in  shape,  lying  obliquely  from 
above  to  below,  and  from  within  outwards,  on  the  sides  of  the  cranium  the 
temporal  fossa  is  limited,  within,  by  the  parietal  ridge,  and  outwardly  by 
the  anterior  border  of  the  longitudinal  root  of  the  zygomatic  process.  It 
lodges  the  temporal  muscle. 

Base  or  superior  extremity  of  the  head. — This  presents  the  occipital  pro- 
tuberance, cervical  tuberosity,  occipital  foramen,  mastoidean  ridge  and  fissures 
styloid  processes  of  the  occipital  bone,  stylo-condyloid  notches,  and  the  con- 
dyles. On  a  lower  plane,  and  behind,  the  curved  portion  of  the  posterior 
border  of  the  maxillary  bone  is  remarked. 

Suvimit. — Formed  by  the  premaxillary  bones  and  the  body  of  the  super- 
Fig.  26. 


LATERAL   VIEW    OF    THE    HORSE  S  SKULL. 

1,  Premasillary  bone ;  2,  Upper  incisors ;  3,  Upper  canine  teeth ;  4,  Superior 
ma.xillary  bone ;  5,  Infraorbital  foramen ;  6,  Superior  maxillary  spine ;  7,  Jvasal 
bones;  8,  Lachrymal  bone;  9,  Orbital  cavity;  10,  Lachrymal  fossa;  11,  Malar 
bone;  12,  Upper  molar  teeth;  13,  Frontal  bone;  15,  Zygomatic  process,  or  arch; 
16,  Parietal  bone ;  17,  Occipital  protuberance;  18,  Occipital  crest ;  19,  Occipital 
condyles;  20,  Styloid  processes;  21,  Petrous  bone;  22,  Basilar  process;  23, 
Condyle  of  inferior  maxilla ;  24,  Parietal  crest ;  25,  Inferior  maxilla ;  26,  Inferior 
molars  ;  27,  Anterior  maxillary  foramen ;  28,  Inferior  canine  teeth ;  29,  Inferior 
incisor  teeth. 

maxilla,  the  summit  supports  the  incisor  teeth,  and  presents  a  tuberosity 
more  or  less  rounded,  according  to  the  age  of  the  animal.  In  front,  it  is 
surmounted  by  the  external  opening  of  the  nasal  cavities;  this  opening, 
wliich  is  comprised  between  the  external  process  of  the  premaxillary  bones 
and  the  nasal  spine,  is  divided  in  the  fresh  state  into  two  orifices  which 
constitute  the  nostrils. 

Internally,  the  head  contains  the  nasal  fossce  and  the  cranial  cavity. 
These  will  be  described  when  the  apparatus  belonging  to  them  is  noticed. 
(See  the  respiratory  and  nervous  apptaratus). 

DIFFERENTIAL    CHARACTERS    OF   THE    HEAD    IN   OTHER   THAN    SOLIPED   ANIMALS, 

A.  Head  OF  the  Ox,  Sheep,  and  Goat.— 1.  Occipital  bone.— The  occipital  bone  in 
these  animals  docs  not  show  any  anterior  elbow.     The  cervical  tuberosity,  or  occipital 


56 


THE  BONES. 


protuberance  is  obtuse,  and  gives  rise  on  each  side  to  the  superior  curved  lines ;  in  the 
Sheep,  these  curved  lines  are  very  salient  and  occupy  the  summit  of  the  head. 

The  styloid  processes  are  sliort  and  much  bent  inwards.  The  basilar  process,  wide, 
short,  and  thick,  has  a  groove  in  the  middle  of  its  external  face ;  this  groove  is  sometimea 
absent  in  the  Sheep  and  Goat. 

The  condyloid  foramina  are  double,  sometimes  triple ;  the  superior  foramen  does  not 
pass  directly  into  the  cranium,  but  goes  to  a  vast  conduit  that  opens  behind  on  the  lateral 
maro-in  of  the  occipital  foramen,  and  which  terminates  in  front  by  two  orifices,  one 
entering  the  parieto-temporal  canal,  the  other  opening  on  the  external  surface  of  the 
bone.  The  foramen  lacerum  is  divided  into  an  anterior  and  posterior  foramen  by  the 
mastoid  portion  of  the  temporal  bone. 

Parietal  hone.— The  parietal  bone  in  the  Ox  does  not  occupy  the  anterior  aspect 

Fis:.  27. 


ox's  head;  anterior  face. 
1,    Mastoid   process;    2,  Superciliary,   or  supra-orbital   foramen;    3,   Zygoma;    4, 
Lachrymal  bone ;  5,  Maxillary  spine ;  6,  Inferior  orifice  of  the  supermaxillo-dental 
canal. 

of  the  head,  but  concurs  with  the  occipital  to  form  the  bnse  of  the  neck.  It  represents  a 
very  narrow  osseous  plate,  elongated  transversely,  and  curved  at  its  two  extremities, 
which  descends  into  the  temporal  fossa"  to  rest  ujxju  the  sphenoid  bone.  There  are  no 
parietal  ridges.  The  internal  protuberance  is  only  marked  by  a  slight  elevation  of  the 
internal  plate  ;  for  the  most  part  it  belongs  to  the  occipital  bone. 

The  parietal  bone  of  the  Ox  is  developed  from  three  cfntres  of  ossification,  and  the 
middle  nucleus  is  even  primarily  divided  into  lateral  halves  ;  but  those  centres  are 
consolidated  with  each  other  at  an  early  period,  as  well  as  with  tlie  anterior  portion  of 
the  occipital.  It  does  not  aid  in  the  formation  of  the  pariefo-tenijoral  canal,  and  is 
excavated  internally  by  cavities  which  communiciite  with  the  frontal  sinuses. 

The  parietal  bone  of  the  Sheep  and  Goat  is  relatively  much  larger  than  that  of  the  Ox. 
It  participates  in  the  formation  of  the  paiieto-temporal  canal,  and  has  no  sinuses. 

3.  Frontal  bone. — In  ruminants,  the  frontal  bone  does  not  respond  to  the  temporal 
and  palate  bones. 

In  the  Oz,  this  bone  is  extremely  developed,  by  itself  occupying  the  anterior  half  of  the 


TRE  HEAD. 


57 


face.  It  is  particularly  distinguished  by : — 1,  Its  great  thickness.  2,  The  osseous 
conical  cores  which  support  the  horns.  These  eminences,  more  or  less  long  and  curved, 
very  ruy;ged,  perfovated  by  foramina,  and  grooveii  by  small  vascular  channels,  are 
detached  outwar<ls  from  each  side  of  the  bone,  near  the  summit  of  the  head.  The 
processes  which  form  the  orbital  arches  rest  by  their  summits  on  the  zygomatic  bone. 
The  supra-orbital  foramen  is  transformed  into  a  veritable  and  frequently  multiple  canal; 
its  anterior  orifice  opens  into  a  vasculo-nervous  groove,  which  ascends  towards  the  base 
of  the  horns,  and  descends  to  near  the  lower  border  of  the  bone.  Between  this  groove 
and  the  base  of  the  orbital  arch  is  the  frontal  boss.  The  orbital  foramen  entirely  belongs 
to  tliis  bone.  The  inferior  border  is  deeply  notched  in  its  middle  to  receive  the  nasal 
bones ,  the  frontal  sinuses  are  prolonged  into  the  horn-cores,  the  parietal  bone,  and  even 
into  the  occipital  bone. 

In  the  Sheep  and  Goat,  the  frontal  bone  is  relatively  less  extensive  and  strong  than  in 
the  Ox;  it  does  not  ascend  to  the  summit  of  the  head,  and  the  frontal  sinuses  are  not 
prolonged  beyond  its  superior  border. 


Fig.  28. 


4.  Ethmoid  hone. — In  ruminants, 
the  great  ethmoidal  cell  is  enor- 
mously developed,  and  looks  like  a 
third  turbinated  bone  prolonged  be- 
tween the  usual  two;  it  has  been 
named  the  olfactory  antrum. 

The  ethmoid  bone  is  closely  im- 
prisoned between  the  adjacent  bones, 
in  consequence  of  the  slight  develop- 
ment of  the  sinuses  around  it.  This 
character  otherwise  belongs  to  all 
the  domesticated  animals,  except  soli- 
peds. 

5.  Sphenoid  hone. — In  the  Ox, 
the  subsphenoidal  or  pterypfoid  pro- 
cesses are  large  and  thin.  The  sub- 
sphenoidal canal  is  absent.  The 
sella  turcica  is  deep,  and  the  bony 
projection  separating  it  from  the 
basilar  process  is  very  high.  The 
three  suprasphenoidal  canals  are 
converted  into  a  single,  but  wide 
one.  There  are  no  notches  in  the 
superior  border  for  the  passage  of 
the  internal  carotid  and  spheno- 
spinous  arteries.  That  for  the  in- 
ferior maxillary  nerve  is  converted 
into  a  canal — the  oval  foramen. 

In  the  Sheep,  the  osseous  promi- 
nence that  limits  the  pituitary  fossa 
posteriorly  forms  a  lamina  curv- 
ing forwards  and  prolonged  at  its  ex- 
tremities into  two  points,  which 
constitute  the  posterior  clinoid  pro- 
cesses. 

6.  Temporal  hoyie. — In  the  Ox, 
Sheep,  and  Goat,  the  tuberous  portion 
of  the  temporal  bone  is  always  con- 
solidated with  the  squamous  portion, 
and  the  summit  of  the  zygomatic 
process  only  articulates  with  the 
malar  bone. 

In  the  Ox,  the  condyle  of  the 
zygomatic  process  is  very  wide  and 
convex  in  every  sense.  "The  parieto-temporal  canal  is  very  large  and  entirely  excavated 
m  the  temporal  bone;  its  superior  or  internal  extremity  opens  above  the  petrous  portion 
in  an  excavation  which  represents  the  lateral  cavity  of  the  parietal  protuberance  in  the 
Hor.-e  ;  at  its  inferior  extremity  it  always  shows  several  orifices. 

The  mastoid  process  is  very  salieiit,  and  belongs  to  the  squamous  portion.     The 
mastoid  crest  is  confounded  with  the  upper  root  of  the  zygomatic  process ;  inferiorly,  it 


RAMS  head;  anterior  face. 
1,  Occipital  bone  ;  2,  Parietal  bone ;  3,  Core  of  right 
frontal  bone ;  4,  The  left  core  covered  bv  its  horn ; 
5,  Superciliary  foramen ;  5',  Channel  descending 
from  it;  6,  Lachrymal  bone;  7,  Zygoma;  8,  Nasal 
bone;  9,  Supermaxillary  bone;  10,  Premaxillary 
bone;  10',  Its  internal   process;  11,  Incisive  open- 


58 


TEE  BONES. 


surpasses  the  mastoid  process,  and  is  prolonged  to  the  mastoid  protuberance.  The  latter 
is  very  voluminous.  The  subuliform  proceas  is  larger  aud  stronger  than  in  the  Horse; 
and  there  is  no  mastoid  fissure. 

In  the  Sheep  and  Goaf,  the  mastoid  iJrocess  is  scarcely  distinct  from  the  crest;  aud 
the  mastoid  portion  of  the  bone  is  only  at  a  late  period  consolidated  with  the  petrous 
portion. 

Fig.  29. 


ox's   HEAD;   POSTERIOR   FACE. 

A,  Parietal  bone. — 1,  Occipital  foramen ;  2,  Occipital  condyle ;  3,  Styloid  process 
of  that  bone ;  4,  Condyloid  foramina ;  5,  Mastoid  process ;  6,  Mastoid  protuber- 
ance ;  7,  Subuliform  (temporal)  process ;  8,  Hyoideal  sheath  ;  9,  Stylo-mastoid  ■ 
foramen;  10,  External  auditory  hiatus;  11,  Inferior  orifice  of  the  ])arieto-tem- 
poral  canal;  12,  Temporal  condyle;  13,  Posterior  foramen  lacerum ;  14,  Oval 
foramen;  17,  Subsphenoidal  process;  18,  Orbital  hiatus;  19,  Optic  foramen. — 
B,  Frontal  bone. — 20,  Superciliary  foramen;  21,  Orbital  foramen;  22,  Lachrymal 
protuberance. — C,  Zygoma. — 23,  Pterygoid  bone. — D,  Palate  bone. — 24,  Nasal  fora- 
men ;  25,  Inferior  orifice  of  the  palatine  canal. — E,  Superma.xillary  bone. — 26, 
Maxillary  spine, — G,  Premaxillary  bone. — 27,  Its  internal  process  ;  28,  External 
process ;  29,  Incisive  openings. 

7.  Supermaxillanj  bone. — In  the  Ox,  Sheep,  and  Goaf,  the  maxillary  spine  does  not 
directly  join  the  zygomatic  crest  a  curved  line,  whose  concavity  is  jMisterior,  eficcts  the 
union  l)etween  these  two  parts.  The  inferior  orifice  of  the  supormaxillo-dentul  canal 
or  infraorbital  foramen  is  pierced  above  the  first  molar  tooth.  There  is  no  fissure  for 
the  formation  of  the  palatine  canal.  The  cavity  of  the  sinus  is  more  spacious  than  in 
the  Horse,  and  is  prolonged  (in  the  Ox  only)  between  the  two  laminae  of  the  palatine 
roof.     There  is  no  alveolus  for  the  tusk. 

8.  Premaxillary  bone. — The  inferior  or  principal  portion  of  this  bnne  is  flattened  before 


THE  HEAD. 


50 


ami  behiiKl.  and  deprived  ofaveoliin  its  external 
border;  neither  is  tliero  any  incisive  foramen. 
It  is  rarely  consolidated  with  the  adjacent  bones, 
and  is  never,  in  the  smaller  ruminants,  articu- 
lated with  the  nasal  bone. 

9.  Falate  hone. — This  bone  is  very  developed 
in  the  Ox,  and  noticeable  lor  the  considerable 
extent  of  the  palatine  portion  of  its  external  sur- 
face. The  palatine  canal  is  entirely  chainiekd 
out  in  its  substance.  The  palatine  cnst,  very 
thin  and  elevated,  is  formed  altogether  by  the 
posterior  border  of  tlie  palate  bone,  the  ptery- 
goid, and  the  subsphenoidal  process.  There  is 
no  excavation  for  the  sphenoidal  sinuses;  but, 
instead,  all  that  part  of  the  bone  which  enters 
into  the  roof  of  the  palate  is  hollowed  by  irre- 
gular cavities  which  communicate  with  the  max- 
illary sinus  of  the  same  side.  The  nasal  foramen 
is  very  wide.  In  the  Slieep  and  Goat,  the  maxil- 
lary sinuses  do  not  extend  to  them. 

10.  Fterygoid  bone. — The  pterygoid  of  the  O.r, 
Sheep,  and  Goat  is  very  large,  and  closes  an  aper- 
ture left  between  ti.e  sphenoid  and  palate  bones. 

11.  Zygoma. — The  jugal  bone  oi  Ruminantx  is 
very  devtloped.  The  zygomatic  crest  is  no 
longer  formed  by  the  posterior  border  of  the  bone, 
but  is  carried  to  the  posterior  part  of  the  external 
face,  and  runs  parallel  with  the  eyebrow.  The 
summit  is  bifurcated,  the  anterior  branch  form- 
ing a  buttress  against  the  summit  of  the  orbital 
process  of  the  frontal  bone,  while  the  jjosterior 
articulates  with  the  temporal. 

12.  Lachrymal  hone. — The  lachrymal  bone, 
much  more  extensive  than  that  of  the  Horse,  forms 
in  the  bottom  of  the  orbit  an  enormous  protube- 
rance, hollowed  internally  by  the  maxillary  sinus, 
and  whose  walls  are  so  thin  and  fragile  that  the 
slightest  jar  is  sufficient  to  cause  their  fiacture 
(in  the  skeleton).  It  would  be  convenient  to 
designate  it  the  lachrymal  •protuberance.'^  In  the 
smaller  nmiinants,  the  inferior  region  of  the  exter- 
nal face  shows  a  depression,  the  lachrymal  fossa. 

13.  Nasal  hones. — The  nasal  bones  of  the  Ox 
are  never  consolidated  with  each  other,  nor  yet 
with  tlie  neighbouring  bones.  The  external  border 
only  comes  in  contact  to  a  small  extent  with  the 
supermaxillary  bone;  the  superior  extremity  is 
fixed  in  the  notch  of  the  inferior  border  of  the 
frontal  bone.  At  their  inferior  extremity,  they 
each  present  a  notch  which  divides  them  into  two 
points. 

In  the  Sheep  and  Goat  the  nasal  spine  is 
unifid,  as  in  tiie  Horse. 

14.  Turbinated  hones. — In  the  Ox,  the  eth- 
moidal turbinated  bone  is  very  small,  and  united 
to  the  nasal  bone  by  the  two  borders  of  its  osseous 
plate;  its  internal  cavity  entirely  belongs  to  the 
frontal  sinus.  The  maxillary  turbinated  bone  is 
very  developed,  and  is  joined  to  the  bone  which 
sustains  it  at  a  later  period  than  in  the  Horse. 
The  bony  lamina  of  which  it  is  composed  is  curved 

•  Girard,  who  named  this  eminence  the  orbital 
protuberance,  wrongly  described  it  as  belonging 
to  the  supermaxillary  bone. 


Fiff.  30. 


MEDIAN   AND   VERTICAL   SECTION   OF 
THE    ox's    HEAD. 

1,  Condyloid  foramen;  1',  Posterior  ori- 
fice of  the  occipital  lateral  canal 
joining  the  parieto-temporal  canal 
in  front ;  2,  Internal  auditory  hiatus ; 
3,  Anterior  foramen  lacerum  ;  4,  Pos- 
terior ditto;  5,  Intra-cranial  orifice 
of  the  parieto-temporal  canal ;  6,  6, 
Median  bony  plate  separating  the 
frontal  sinuses;  7,  Lamina  which  iso- 
lates the  sphenoidal  sinus;  8,  Lamina 
partitioning  the  palatine  portion  of 
the  maxillary  sinuses ,  9,  Oval  fora- 
men;  10,  Optic  fossa;  11,  Vomer; 
12,  Pterygoid  bone;  13,  Large  open- 
ing leading  into  the  maxillary  sinuh. 
and  which,  in  the  fresh  state,  is  closed 
by  the  pituitary  membrane ;  14,  Max- 
illary turbinated  bone,  15,  Ethmoidal 
turbinated  bone;  16,  Great  ethmoid:.! 
cell. 


60 


THE  BONES. 


Fig.  31. 


on  itself  in  two  different  directions :  from  before  to  behind  by  its  posterior  border,  and 
behind  to  before  by  its  anterior  border.  It  is  fixed  to  the  supermaxillary  bone  by  its 
middle  part,  through  tlie  medium  of  a  particular  bony  lamina,  and  it  very  incompletely 
closes  the  excavation  which  concurs  to  form  the  maxillury  sinus.  In  the  skeleton 
there  is  also  found  behind,  and  at  the  base  of  this  turbinated  bone,  a  vast  opening  which 
istdtally  closed  in  the  fresh  condition  by  the  pituitary  membrane.  The  maxillary  sinus 
is  not  prolonged  in  its  interior.  In  the  smaller  ruminants,  the  cavity  of  the  sinus  is 
closed  by  the  maxillary  turbinated  bone  in  a  more  complete  manner  than  in  tbe  Ox. 

15.    Vomer. — This  is  a  very  large  tliin  bone,  resting  only  on  the  inferior  half  of  the 
median  suture  of  the  premaxillaries. 

16.  Premaxillary  bone. — In  the  Ox,  the  inferior  part  of  the 
posterior  border  is  convex,  and  cannot  rest  on  a  horizontal 
plane  by  all  its  points  at  the  sume  time.  The  condyle  is 
convex  in  its  small  diameter,  and  slightly  concave  laterally. 
The  coronoid  process  is  bent  backwards  and  outwards.  The 
body  does  not  show  any  alveolu:*  for  the  tusk,  because  this 
tooth  is  absent  in  these  animals;  but  it  is  hollowed  by  eight 
alveoli  for  the  incisor  teeth.  The  two  branches  of  the  bone 
are  never  consolidated,  but  remain  movable  on  each  other 
during  life. 

17.  Hyoid  hone. — The  hyoid  bone  of  Buminants  is  always 
composed  of  seven  pieces ;  the  styloid  nucleus,  whose  presence 
is  not  constant  in  solipeds,  is  never  absent  in  these,  and 
assumes  the  proportions  of  a  second  small  branch.  The 
anterior  appendix  is  very  short  and  thick. 

B.  Head  of  the  Pig. — 1.  Occipital  hone. — The  occipital 
bone  in  this  animal  is  not  bent  anteriorly ;  but  the  transverse 
protuberance  representing  the  curved  lines  forms,  nevertheless, 
as  in  the  Horse,  the  summit  of  the  head.  This  eminence,  which 
is  excavated  on  both  sides  on  the  posterior  face,  iniites  in  front 
with  the  parietal  bone,  which  abuts  on  the  occipital  at  an 
acute  angle.  There  is  no  external  occipital  protuberance, 
properly  speaking,  and  the  styloid  processes  are  very  long  and 
directed  downwards. 

2.  Parietal  hone. — This  bono  is  very  thick,  and  deprived 
of  an  internal  protuberance.  The  process  concurring  to  cir- 
cumscrilje  the  orbit  is  short,  and  joins  neither  the  zygomatic 
or  temporal  bones;  the  orbital  arch  is  completed  by  a  liga- 
ment. The  superciliary  foramen,  disposed  as  in  the  Ox,  opens 
in  front  into  a  channel  that  descends  to  the  nasal  bones.  The 
orbital  foramen  is  formed  by  the  frontal  bone  only.  There 
is  no  mortice  for  the  union  of  the  Irontal  with  the  sphenoid 
bone,  and  the  maxillary  sinus  is  prolonged  into  the  parietal 
bone.  The  frontal  bone  of  the  pig  articulates  with  the  super- 
maxilLiries. 

o.  Frontal  hone. — The  frontal  bone  of  the  Pig  is  very  thick 
and  short,  and  docs  not  join  the  t-  mporal  or  zygomatic  bone  ; 
the  orbital  arch  is  comjileted  by  a  ligament.  The  superciliary 
foramen,  disposed  as  in  the  Ox,  abuts  in  a  channel  that 
descends  on  the  nasal  bones.  The  orbital  foramen  is  fornrcd 
by  the  frontal  bone  only.  There  is  no  mortice  for  the  miion  of 
the  frontal  with  the  sjihenoid  bone  ;  and  the  frontal  sinuses  are 
prolonged  into  the  jiarietal.  The  frontal  bone  of  the  Pig 
articulates  with  the  superraaxillarics. 

4.  Sphenoid  hone. — The  sphen(  lid  of  the  Pijr  is  very  short,  bnt 

the  subsphenoidal  processes  are  extraordinarily  developed  and 

flattened  before  and  behind.    There  is  no  subsphenoidal  canal, 

and  the  sella  turcica  is  deep,  and  limited  behind  by  a  very  salient 

crest.     A  single  canal  replaces  the  foramen  rotundum  and  the 

great  sphenoidal  fissure,  as  in  the  Ox.     The  wings,  slightly 

salient,  are  articulated  by  suture  with  the  frontal  bone. 

5.  Temporal  bone. — The  articular  surface  of  this  bone  resembles  that  of  rodents ;  it  is 

not  limited  posteriorly  by  a   suVicondyloid  eminence,  and,  in  additifm,  oft'ers  a  wider 

transverse  surface.     The  zygomatic  process  articulates  with  the  jugal  bone  by  the  whole 

extent  of  its  posterior  border.     A  crest  leading  from  the  external  auditory  hiatus  to  the 


HEAD  OF  THE  PIG; 
ANTERIOR  FACE. 

1,  Summit  of  occipital  pro- 
tuberance; 2,  Parietal 
bone ;  3,  Frontal  bone. 
— A,  Superciliary  fora- 
men ;  a'  Channel  des- 
cending from  it. — 4, 
Zygomatic  process ;  5, 
i^ygoma^  6,  Lachrymal 
iboffle. — B,  Lachrymal 
•canals. — 7,  Supermax- 
illary bone, — C.  Inferior 
■oa'ifice  of  th«  supermax- 
illo-dental  canal  ;  8, 
Nasal  bone ;  9,  Pre- 
maiillary  bone. 


THE  HEAD. 


61 


Fiff.  32. 


mastoid  protuberance  replacis  the  mastoid  process.     The  mastoid  crest  is,  as  in  the  Ox, 
coutbundetl  with  the  superior  root  of  tiie  zygomatic  process. 

The  prqj.  ction  formed  by  the  mastoid  jtrotuberanee  is  enormous.     The  subuliform 
process  is  little  marked,  and  there  is  no  liyoideal  prolongation  or  parieto-temporal  canal. 

G.  Supennaxillary  bone. — In  the  Pig,  tlie  ex- 
ternal surface  of  this  bone  is  hollowed  in  its  middle, 
and  presents  in  front  a  voluminous  relief  formed 
by  the  alveolus  of  the  canine  tooth,  'llie  cavity 
is  entirely  formed  in  the  supermaxilla.  'I'here  is 
no  alveolar  tuberosity,  and  the  interdental  space 
is  very  short,  while  the  cavity  for  the  sinus  is  little 
developed.  The  lower  orifice  of  the  [lalatiue  canal 
is  even  pierced  in  the  substance  of  the  super- 
maxilla. 

7.  Fremaxillary  hone. — The  external  process  of 
the  premaxillary  bone  is  very  long  und  wide  at  its 
base,  and  consolidated  with  the  nasal  bone  for 
about  the  upper  two-thirds  of  its  length.  Tliere 
is  no  incisive  foramen  or  cavity  for  the  tusk.  The 
incisive  openings  are  oval. 

8.  Falate  bone. — The  palatine  portion  of  the  ex- 
ternal face  is  more  developed  than  in  the  Ox,  but 
the  orbital  portion  is  very  limitc'd.  The  palatine 
crest  is  ri  placed  by  a  tuberosity,  against  which 
rests,  outwardly,  the  subsphenoidal  process,  and 
inwardly,  the  pterygoid  bone.  The  union  of  these 
three  parts  constitutes,  on  the  posterior  surface  of 
the  head,  a  thick  and  very  remarkable  trifid  j^ro- 
jection  or  raamelon. 

9.  Pterygoid  bone. — See  the  description  of  the 
palate  bone. 

10.  Zygomatic  bone. — The  summit  of  this  bone 
in  the  Pig  is  flattened  on  each  side,  and  divided 
into  two  blanches,  between  which  is  wedged  the 
summit  of  the  zygomatic  process ;  the  anterior 
branch  is  very  short,  and  does  not  join  the  frontal 
bone. 

11.  Lachrymal  bone.— In  the  Pig  tliere  are  ob- 
served a  lachrymal  fossa  and  two  lachrymal  canals, 
whit-h  are  pierced  outside  the  orbital  cavity,  and 
soon  coalesce  in  the  substance  of  the  bone  to  consti- 
tute a  single  canal.     The  fossa  is  very  deep. 

12.  Nasal  bones.  — These  bones  are  long  and  nar- 
row, and  traversed  on  tiieir  external  face  by  the 
fissure  tiiat  descends  from  the  superciliary  foramen,    head  of  the  pig  ;  posterior  face 
The  nasal  prolongation  is  short.  1,  Occipital    protuberance;    2,    Occi- 

13.  'J 'urbinated  bones. — Tiie  same    arrangement       pital    foramen;    3,  Occipital    con- 
as  in  the  Sheep  and  Goat,  except  that  they  are 
much  longer  and  less  fragile. 

14.  Inferior  Maxilla. — A  straight  line  leading 
from  the  greater  axis  of  the  alveoli  of  th(^  molar  would 
not  traverse  the  posterior  border  of  the  maxillary 
branches ;  the  bottom  of  these  alveoli  corresponds 
to  the  relief  on  the  inner  face.  The  ■  condyle  is 
compress'  d  on  both  sides,  and  elongated  frt)m  before 
to  behind  ;  while  the  coronoid  process  is  short  and 
wide.  There  is  no  neck ;  the  interdental  spaces 
are  very  short ;  and  the  maxillo-dental  canal  opens 
interiorly  by  multiple  orifices. 

1.5.  Hyoid  bnne.— The  body  is  voluminous  and 
deprived  of  an  appendix;  the  small  branches  are 
short  and  consolidated  with  the  body  ;  while  the  large  branches,  curved  like  an  S,  are  very 
thin,  and  are  united  to  the  small  branches  and  the  temporal  bone  no  longer  by  fibro- 
cartilage,  but  by  veritable  yellow  elastic  ligaments. 

C.  Head  of  Caknivora. — 1.  Occipital  hone. — The  eminence  which  constitutes  the 


dyle  ;  4,  Condyloid  foramen ;  5, 
Basilar  process  ;  6,  6,  Mastoid  crest; 
7,  Styloid  process  of  the  occipital 
bone ;  8,  Articular  surface  of  the 
temporal  bone ;  9,  Mastoid  protu- 
berance;  10,  Foramen  lacerum  ;  11, 
Subsphenoidal  process  —  external 
wing  of  pterygoid  process;  12, 
Palatine  crest ;  13,  Pterygoid  bone 
— mternal  wing  of  the  pterygoid 
process;  14,  Inferior  orifice  of  the 
palatine  canal ;  15,  15,  Incisive 
openings. 


62 


THE  BONES. 


origin  of  the  superior  curved  lines  is  very  elevated  and  strong.  The  cervical  tuberosity 
of  the  external  occipital  protuberance  is  absent  or  little  marked ;  the  styloid  processes 
are  short,  and  well  deserve  tlie  name  of  jugular  eminences.  TJie  foramen  lacerum  is 
divided  into  two  portions  by  the  mastoid  protuberance,  and  the  basilar  process  is  wide, 
long,  and  tliick,  and  hollowed  on  tlie  side  by  a  channel  tliat  joins  a  similar  one  in  the 
temporal  bone  to  form  a  large  venous  canal.  This  last  communicates,  behind,  with  the 
posterior  foramen  lacerum,  and  opens,  in  front,  in  the  cranium,  where  it  is  continuous 
with  the  cavernous  groove  of  the  sphenoid.  The  anterior  angle  forms  a  very  marked 
prominence,  which  is  deeply  fixed  into  the  parietal  bone,  and  partly  constitutes  the 
internal  protuberance  of  that  bone. 

2.  Parietal  hone. — In  the  Bog  the  parietal  bone,  formed  by  two  ossific  centres  only, 
is  distinguished  by  the  great  develo2)ment  of  the  ridges  and  the  parietal  protuberance. 
This  last,  constituted  in  part  by  the  occipital  bone,  does  not  show  any  lateral  excavations 
at  its  base ;  tiiey  are  carried  lower,  near  the  summit  of  tlie  petrous  process,  on  the 
sides  of  the  occipital  bone.  The  parieto-temiwral  canals  are  continued,  notwithstanding, 
to  the  base  of  the  protuberance,  which  they  traverse,  to 
open  into  each  otlier  in  its  interior. 

In  the  Cat  there  are  scarcely  any  parietal  crests,  and 
the  internal  protuberance  is  replaced  by  two  great  trans- 
verse bony  plates  which  separate  the  cavity  of  the  cerebrum 
from  that  of  tlie  cerebellum. 

3.  Frontal  bone. — In  carnivora,  the  external  face  of  this 
bone  presents  in  its  middle  a  more  or  less  marked  de- 
pression. The  orl)ital  arch  is  incomplete,  and  there  is  no 
superciliary  forauien,  or  mortice  on  the  inner  face.  The 
bone  is  united  with  the  supermaxillaries. 

4.  Ethmoid  bone. — The  ethmoidal  fossa  is  very  deep, 
and  the  cells  very  developed  and  diverticulated.  The  per- 
pendicular lamina  is  at  a  late  period  consolidated  with  the 
sphenoid  bone. 

5.  Sphenoid  bone. — The  superior  sphenoid  of  the  Dog  is 
very  short,  and  bears,  laterally,  two  wide  wings  which 
ascend  to  the  temporal  fossa ;  they  correspond  to  those  of  the 
sphenoid  bone  in  Man.  The  inferior  sphenoid  is,  on  the 
contrary,  very  narrow,  and  its  lateral  prolongations,  or  pro- 
cesses of  Ingrassias,  are  reduced  to  very  small  proportions. 
The  sub-sphenoidal  or  pterygoid  process  is  very  short,  and 
the  canal  is  single,  and  communicates  with  the  foramen 
rotundum.  The  pituitary  fossa  is  shallow,  limited  behind 
and  before  by   the  posterior  clinoid  and   anterior   clinoid 

HEAD    OF    DOG ;    ANTERIOR  processes,  so  named  because  of  their  being  compared  to  the 
PACE.  four  posts  of  an  ancient  bed.     The  supersphenoidal  canals 

1  Occipital  protuberance  •  2  are  only  two  in  number :  one  represents  the  great  sphenoidal 
'  Median  spur  of  the  o'cci-  fi'^s^'re.  the  other  the  round  foramen.  The  carotid  notch, 
pital  bone  •  3  Parietal  .l""''"o  ^  similar  one  in  the  temporal  bone,  forms  an  open- 
bone*  4  Orio-in'of  the  pa-  "'»  which  may  be  designated  the  carotid  foramen,  because 
rietal  crests -^5  Zv^omatic  '*  ^ives  passage  to  an  extremely  remarkable  loop  the  in- 
process  of  'the  temporal  ^•^'■iial  carotid  artery  describes  after  passing  through  the 
bone-  6  Frontal  bone*  6'  carotid  canal.  Tlie  oval  foramen  is  the  s;inie  as  in  the  Ox. 
Orbital'  process-  7  'zv-  In  the  Cat  there  is  the  same  disposition,  with  the  ex- 
'      '  ception  of  no  sphenoidal  canal  or  carotid  notch  beini;;  present. 

6.  Temporal  bone. — In  the  carnivora,  the  articular  sur- 
face of  the  zygomatic  i^rocess  merely  forms  a  glenoiil 
cavity,   into    which   the   C"ndyle   of  the   maxillary   bono 

Pre-  e^^ctly  fits.     The  temporal  bone  in  these  animals  is  also 
distinguished  by  the  width  of  the  external  auditory  canal, 


goma ;  8.  Lachrymal  bone ; 
9,  Nasal  bone;  10,  Super- 
maxilla;  11,  inferior  ori- 
fice of  the  .supermaxillo- 
dental  canal ;  1'. 
maxillary  bone. 


the  absence  of  a  hyoid  prolonginent,  the  small  development 
of  the  mastoid  and  styloid  jtrocesses,  the  enormous  volume 
of  the  mastoid  protuberance,  and  the  presence  of  two  pai  ticidar  canals  which  cannot  be 
traced  in  the  other  animals.  One  of  them,  the  carotid  canal,  traverses  the  mastoid 
portion,  and  joins,  superiorly,  the  venous  canal  which  passes  between  the  biisilar 
process  and  the  temporal  bone ;  by  its  inferior  extremity  it  joins  the  carotid  foramen 
which  itself  penetrates  the  cranium,  a  little  beyond  the  venous  canal  just  mentioned. 
The  other  conduit  is  pierced  in  the  petrous  portion  immediately  above  the  carotid  canal  j 
it  affords  a  passage  to  the  fifth  pair  of  encephalic  nerves. 


THE  HEAD. 


63 


7.  Supermaxillary  bone. — In  caraivora,  this  bone  is  very  short ;  its  anterior  border 
offers  a  long  process  analogous  to  the  nasal  spine  of  Man.  It  alone  furnishes  the  alveolus 
of  the  tusk.  The  palatine  c«nal,  pieiced  entirely  in  the  bone  of  that  name,  nevertheless 
opens,  by  its  inferior  extremity,  at  the  junction  of  the  supermaxillary  with  the  palate 
bone.     The  maxillary  sinus  is  not  very  spacio\is.  and  tliere  is  no  maxillary  spin 

8.  Premaxillary  bone. — Of  little  size,  tlie  premaxillary 

of  carnivora  has  no  incisive  foramen  or  alveolar  cavity  (or  Fig.  34 

the  canine  tooth.     The  incisive  openings  are  the  same  as 
in  the  Fig. 

y.  Falate  bone. — In  the  carnivora,  the  palate  bones  are 
of  great  extent  in  their  proper  palatine  portion.  They  have 
jjo  share  in  the  formation  of  the  sphenoidal  sinuses,  but 
furnish  a  small  excavation  to  the  m;ixiilary  sinuses. 

10.  Pterygoid  6«He.— This  bone  is  very  strong  in  car- 
nivora, and  quadrilateral  in  shape. 

11.  Zygoma. — The  zygoma  of  the  Dog  and  Cat  only 
articulates  with  the  supermaxillary  bone  by  its  base.  The 
crest  describes  a  curve  backwards,  and  the  summit  com- 
ports itself  as  in  the  I'ig. 

12.  Lachrymal  bone. — This  bone  in  carnivora  is  ex- 
tremely small.  Its  external  face  entirely  belongs  to  the 
orbit,  and  does  not  descend  beneath  the  margin  of  that 
cavity ;  it  has  no  lachrymal  fossa. 

13.  Nasal  bone. — The  two  bones  of  the  nose  are  little 
developed,  and  are  wider  below  than  above;  they  have 
no  nasal  prolongation,  but  offer  instead  a  semicircular 
notch. 

14.  Turbinated  hones.—  These  bones  in  the  Dog  and  Cat 
are  particularly  distinguished  for  their  numerous  convo- 
lutions. Neither  participate  in  the  formation  of  the  frontal 
or  maxUlary  sinuses :  the  latter  is  not  in  any  way  closed 
by  the  maxillary  turbinated  bone,  but  opens  into  the 
nasal  cavity  by  a  large  gaping  aperture. 

15.  Inferior  maxillury  hone. — In  carnivora,  this  is 
hollowed  at  the  point  corresponding  to  the  insertion  of 
the  masseter  muscle  into  a  somewhat  deep  fossa.  The 
posterior  border  is  disposed  as  in  ruminants,  and  below 
the  condyle  has  a  very  marked  tuberosity.  The  condyle 
rt  presents  an  ovoid  segment,  and  fits  exactly  into  the 
temporal  cavity.  The  coionoid  process  is  very  strcmg, 
elevated,  and  wide.  The  mental  foramina  are  double  or 
treble.  There  are  no  interdental  spaces,  nor  excavated 
surface  on  the  inner  face  of  the  branches ;  and  the  latter 
are  never  consolidated. 

16.  Hyoid  bone. — The  three  pieces  composing  the  body 
of  the  hyoid  in  early  life  are  never  consolidated  in  the 
adult  animal,  but  always  remain  isolated,  as  in  Man. 
The  middle  piece  has  no  anterior  appendix;  the  fibro- 
cartilages  uniting  the  styloid  portions  to  each  other  and 
to  the  temporal  bone  are  very  long  and  flexible. 

COMPARISON    OF   THE   HEAD   OF   MAN   WITH   THAT   OF   THE 
DOMESTICATED   ANI3IALS. 


1.  Occipital  hone. — The  occipital  of  Man  is  large,  flat, 
incurvated  like  a  shell,  and  the  external  protuberance  is 
slightly  developed,  and  united  by  a  ridge  to  the  occipital 
foramen,  which  is  relatively  very  wide.  Two  series  of 
ridges  arise  from  the  external  protuberance  and  pass 
towards  the  circumference  of  the  bone ;  these  are  the 
superior  and  inferior  curved  or  semicircular  lines.  There 
is  an  anterior  and  a  posterior  condyloid  fossa  pierced  by  a 
foramen  at  the  bottom;  and  the  jugular  eminences,  wide  and  slightly  prominent,  re- 
place the  styloid  processes  of  the  domesticated  animals. 

The  internal   face  of  the  occipital   of  ]ilan  corresponds   with   the   cerebrum  and 


dog's  head  ;  POSTERIOE  FACE. 

1,  Occipital  protuberance ;  2, 
Occipital  foramen ;  3,  Occi- 
pital condyle ;  4,  Condyloid 
foramen  ;  5,  Styloid  process 
of  the  occipital ;  6,  Mastoid 
protuberance ;  7,  Concave 
temporo-maxillary  articular 
surface  ;  8,  Supercondy- 
loid  eminence ;  9,  Inferior 
orifice  of  the  parieto-tem- 
poral  canal ;  10,  Lacer- 
ated foramen,  posterior ;  11, 
Ditto,  anterior. — On  the  op- 
posite side  at  a  is  shown 
the  orifice  communicating 
with  the  Eustachian  tube 
and  the  tympanum ;  at  b 
the  passage  for  the  carotid 
convolution. — 12,  Body  of 
the  sphenoid  ;  1 3,  Oval  fora- 
men ;  14,  Inferior  orifice  of 
the  subsphenoidal  canal ; 
15,  Pterygoid  bone;  16, 
Nasal  surface  of  the  palate 
bone;  17,  Palatine  surface 
of   the  same;    18,   Vomer; 

19,  Supermaxillary    bone; 

20,  Incisive  opening. 


C4 


THE  BONES. 


cerebellum ;  and  for  this  purpose  it  shows  four  fossae,  distinjjuished  into  superior  or 
cerebral,  and  inferior  or  cerebellir.  These  fossae  are  separated  by  a  crucial  projection 
whose  most,  developed  portion  forms  the  internal  occipital  protuberance. 

The  union  of  the  oceipilal  with  the  parietal  bones  constitutes  tlie  lambdoidal  suture. 
At  the  point  wliere  tliis  bone  meets  the  parietal  ami  the  squamous  portion  of  the 
temporal,  is  found,  in  the  infant,  <he  lateral  posterior  fontanella. 

2.  I'ai-iital  hones. — The  parietals  are  always  isolated  in  early  life,  nnd  sometimes 
consolidated  with  eacli  other  at  the  adult  age.  Tiiey  are  very  large,  quadrilateral,  and 
occupy  the  summit  and  sides  of  the  cranium. 

The  parietal  crests  are  absent,  but  are  replaced, 
in  certain  individuals,  by  two  faintly-marked 
curved  lines  situated  a  little  above  the  inferior 
border  of  the  bone.  The  middle  portion  of  the 
external  face  is  very  convex. 

On  the  internal  face  there  is  no  parietal  pro- 
tubeiance,  but  in  its  stead  the  internal  occipital 
protuberance.  It  also  exhibits  ramous  channels, 
which  in  disposition  are  analogous  to  the  ribs  of 
a  fig-leaf;  as  well  as  the  parietal  fossa  which  cor- 
responds to  the  parietal  eminence. 

;-5.  Frontal  hone. —  The  frontal  bone  of  Man  forms 
the  upper  part  of  the  face  and  the  anterior  portion 
of  the  cranium.  Convex  from  behind  forward,  then 
vertical  in  its  upper  three-fourths,  the  bone  sud- 
denly benJs  at  the  orbits,  so  as  to  become  hori- 
zontal in  its  lower  fourth. 

The  external  face  offers,  above  the  forehead,  two 

laternl  frontal  eminences,  and  above   the  nose,   a 

miiklle  frontal  boss.     To  the  right  and  left  of  the 

latter  are  two  salient  arches,  the  supraorbital  ridges. 

'J'he  internal  face  entirely  belongs  to  the  cranial 

cavity.     It  offers  on  the  median  line,  the  saggital 

groove  terminated  by  a  frontal  crest ;  and  on  each 

side  of  this  line  the  frontal  fossae,  corresponding 

to  the  eminences  of  that  name,  and  orbital  bosses 

1,  Frontal  bone;  2,  Nasal  tuberosity;    to  match  the  orbital  loofs.     There  is  no  mortice  for 

3,  Supra-orbital    ridge ;    4,   Optic    the  articulation  of  the  sphenoid  bone. 

foramen;     5,    Sphenoidal    fissure;  On  the  middle  portion  of  the  superior   frontal 

6,    Spheno-maxillary    fissure ;     7,    border,   in   young  persons,  is  the  anterior  angle  of 

Lachrymal    fossa ;    8,    Opening    of    the  anterior  fontanella.     The  anterior  border  ex- 

the  nose  divided  by  the  vomer;  9,    hibits  three  supercdiary  foramina  and  the  orbital 

arches. 

4.  Ethmoid  hone. — In  Man,  the  external  face  of 
the  lateral  masses,  formed  by  a  very  thin  lamina, 
termed  the  os  plonum  or  lamina  papyracx,  belongs 
to  the  internal  wall  of  the  orbit. 

5.  Sphenoid  hone. — This  is  distinguished,  in 
suture;  18,  Upper  part  of  the  great  Man,  into  a  body  and  four  wings,  two  large  and 
alaof  the  sphenoid  bone;   19,  Com-    two  small. 

mencemeut  of  the  temporal  ridge;  Tlie  inferior  surface  of  the  body  offers  nothing 

20,  Zygoma  of  the  temporal  bone,  remarkable,  except  the  presence  of  a  conical  pro- 
concurring  to  form  the  temporal  Ionization  named  the  beak  [rodriun]  of  the  sphe- 
arch;  21,  Mastoid  process.  noid.     The  external  face  of  the  greater  wings  forms 

part  of  the  temporal  fossa,  as  also  the  external  wall 
of  the  orbit  At  the  union  of  the  wings  with  the  body  arc  detached  two  bifid  ptery- 
goid processes ;  their  internal  branch  represents  the  pterygoid  bones  of  animals.  There 
is  no  subsphenoidal  canal. 

The  two  lesser  wings  are  very  thin  and  triangular,  and  visible  only  on  the  superior  sur- 
face of  tiie  bone;  they  constitute  the  processes  of  Ingrassias. 

On  the  internal  face  of  the  bone  are  fmnd  : — 1,  A  deep  pituitary  fossa,  limited  by 
four  clinoid  processes:  2,  An  optic  fossa,  shallow,  showing  very  short  optic  canals  trans- 
formed into  foramina  ■  ■  3,  The  sphenoidal  fissure,  which  replaces  the  great  super- 
sphenoidal  canal  in  the  Horse;  4,  The  great f)ramen  rotnndum  :  5,  The  internal  face  of 
the  wings,  much  excavated  ;  6,  The  foramen  ovale,  which  transmits  the  inferior  maxillary 
nerve;  7,  The  small  foramen  rotundum  that  lodges  the  spheuo-spinous  artery. 


FRONT   VIEW   OF   THE   HUMAN 
CRANIUM. 


Infra-orbital  foramen;  10,  Malar 
bone;  11,  Symphysis  of  the  lower 
jaw;  12,  Mental  foramen;  13, 
Ramus  of  the  lower  jaw;  14,  Parie- 
tal bone  ;  15,  Coronal  suture;  16, 
Temporal     bone;      17,    Squamous 


THE  HEAD. 


65 


Fis:.  36. 


6.  Temporal  hone. — In  the  squamous  portion  of  the  temporal  bone  of  Man,  the 
zygomatic  process  only  rests  on  the  malar  bono,  as  in  ruminants.  The  f^h-noid  cavity 
is  concave  in  every  sense,  and  divided  into  two  parts  by  an  oix'tiing  named  tlie  fis-mra 
Glaseri;  the  anterior  portion  only  is  at ticuhir,  tlie  posterior  lying  against  the  external 
auditory  canal,  does  not  belong  to  the  articulation  ;  it  corresponds  to  the  supr..coniiyloid 
eminence  of  the  Horse.  The  tuberous  portion  is  consolidated  witii  the  squamous.  It  is 
divided  into  a  mastoid  and  a  pyrnmidal  portion ;  the  latter  ccmprises,  in  its  turn,  the 
petrous  and  tympanic  portions.  The  mastoid  portion  corresponds  to  the  mastoid  [irocess, 
mastoid  protnberance,  and  superior  border  of  the  petrous  bone  in  the  Horse.  It  pr<  sents' 
a  rugged  mastoid  process;  above  this  is  the  mastoid  canal;  and  above  andbeliind  it,  the 
digastric  groove ;  the  pyramid  forming  a  con- 
siderable projection  in  the  interior  of  the  cra- 
nium. The  styloid  process  or  bone  is  altogether, 
separate  from  the  otnerpieees  of  the  hyoid.  and  in 
the  adult  is  consolidaled  with  the  temporal  bone. 

7.  Supermaxllla. — In  INlan  the  prenjaxilla  is 
no  longer  found  independent,  the  centre  which 
forms  it  coalescing  with  tliesupermaxiilary  bone. 

The  supermaxilla  of  Man  concurs,  for  the 
greater  part  of  its  extent,  to  tbrm  the  floor  of  the 
orbit ;  it  is  also  divided  into  three  faces :  an 
external  or  facial,  a  superior  or  orbital,  and  an 
internal  or  naso-palatine.  The  external  face 
presents,  from  before  to  behind :  1,  A  small 
fossa,  into  which  is  inserted  the  myrtiform 
muscle ;  2,  The  infraorbital,  or  canine  fossa, 
showing  the  inferior  orifice  of  the  infraorbital 
canal;  55,  A  crest  corresponding  to  the  maxillary 
spine  of  solipeds :  4,  The  alveolar  tuberosity. 
This  face  cariies,  in  front,  a  prolongation  that 
forms  the  ascending  process,  also  named,  be- 
cause of  its  relation,  the  Iron  to-nasal  process. 
The  superior  or  orbital  face  oflers  a  fissure  which 
precedes  the  infraorbital  canal,  and,  outwards, 
the  ma'.ar  process.  The  internal  face  is  divided 
by  tlie  palatine  process.  It  shows,  in  front,  the 
half  of  the  anterior  na.sal  spine  and  a  groove 
•which  participates  in  the  formation  of  the  in-  External  or  basilar  surface  of 
cisive  canal.  the  base  of  the  human  sicull. 

8.  Palate  bone.— The  palate  bone  of  Man  is    1,  1,   The  bony   palate;    2,  Incisive,  or 


formed  of  two  osseous  laminse :  one  horizontal, 
the  other  veitical,  which  are  joined  at  a  ri,L;ht 
dngle.  The  first  part  presents*  one-half  of  the 
posterior  nasal  spine,  wliich  is  altogetlier  rudi-- 
mentary,  or  even  null  in  animals;  the  orifice  of 
the  posterior  palatine  canal,  which  belongs 
entirely  to  the  palate  bone:  the  pterygo-palatine 
foramen;  lastly,  the  pterygoid  process,  which 
represents  the  pterygoid  bone  of  animals.  The 
veitical  portion  forms  the  external  wall  of  the 
nasal  cavities  by  its  internal  face,  and  by  its  ex- 
ternal face  concurs  in  the  formation  of  the 
zygomatic  or  temporal  fossa. 

9.  Zygoma. — This  offers  three  faces.  The 
external,  or  cutaneous,  serves  as  a  base  for  the 
most  salient  part  of  the  cheek.  The  superior,  or 
orbital,  forms  part  of  the  external  wall  and  floor 
of  the  orbit;    it    belongs  to   a  long   apophysis. 


anterior  palatine  foramen;  3,  Palatine 
process  of  palate  bone,  with  the  pos- 
terior palatine  foramen ;  4,  Palate 
spine  with  transverse  ridge  ;  5,  Vomer  ; 
6,  Internal  pterygoid  palate;  7,  Sca- 
phoid fossa;  8,  External  pterygoid 
plate,  with  fossa;  9,  Zygomatic  fossa  ; 

10,  Basilar  process  of  occipital  bone  ; 

11,  Foramen  magnum;  14.  Glenoid 
fossa,  15,  Meatus  auditorins  exter- 
nus ;  16,  Foramen  lacerum  anterius; 
17,  Carotid  foramen  of  leftside;  18, 
Foramen  lacerum  posterius,  or  jugular 
foramen;  19,  Styloid  process;  20, 
Stylo-mastoid  foramen,  with  jugular 
tubercle  and  digastric  fossa-,  21,  Mas- 
toid procei's  5  22,  Occipital  bone ;  23, 
Posterior  condvloid  fossa. 


the  orhittil  process,  which  rests  on  tiie  sphenoid 

and  frontal  bones.     The  posterior  face  is  smooth  and  concave  behind,  where  it  aids  to 

form  the  temporal  fossa;  in  front  it  is  uneven,  and  articulates  with  the  supermaxilla. 

The  posterior,  or  masseteric  border,  unites  with  the  zygomatic  process  of  the  temporal 

bone. 

10.  Lachrymal  hone. — This  bone  is  also  called  the  os  unguis  in  ]\Ian,  because  of  its 
likeness  to  the  nail  in  shape  and  tenuity.     It  is  entirely  lodged  in  the  orbit,  and  its 


66 


TEE  BONES. 


external  face  is  divided  into  two  portioiis  by  a  vertical  crest;  the  portion  situated  in  front 
of  this  crest  forms  part  of  the  lachrymal  channel.  By  its  interaal  face,  the  lachrymal 
bone  limits,  outwardly,  the  bottom  of  the  nasal  cavities,  and  covers  tiie  anterior  cells  of  the 
ethmoid ;  by  its  po.^teriur  border,  within  the  orbit,  it  articulates  with  the  os  planum  of 
the  ethmoid. 

11.  Nasal  bone. — The  proper  bones  of  the  nose  of  Man  exhibit  a  great  analogy  to 
those  of  the  Dog.  They  do  not  possess  a  nasal  prolongation,  and  they  articulate  with 
the  lateral  cartilage  of  the  nose. 

li2.   Vomer. — The  same  general  form  and  relations  as  in  solipeds. 

13.  Inferior  maxillary  bone. — This  bone  in  Man  is  in  shape  somewhat  like  a  horse- 
shoe. It  is  nearly  of  the  same  width  throughout  its  whole  extent.  The  symphysis  is 
vertical — a  character  peculiar  to  Man.  Below  this  symphysis  is  a  triangular  ])rojection, 
the  mental  eminence  The  genial  surface  of  the  Horse  is  replaced  by  four  little  tubercles 
termed  the  genial  processes.  The  alveoli  of  the  molar  teeth  form  a  great  projection  on 
the  inner  face  of  the  bone.  The  mylo-hyoid  ridge  is  very  developed.  The  superior 
orifice  of  the  dental  canal  is  covered  by  a  little  sharp  lamina.  From  this  orifice  begins  the 
mylo-hyoidean  groove.  The  coronoid  process  is  short ;  the  condyle  is  bent  towards  the 
median  line,  and  the  sigmoid  notch  is  wide  and  shallow.  The  superior  border  contains 
fourteen  or  sixteen  alveoli. 

Article  III. — The  Thoeax. 

Tlie  thorax  represents  a  conoid  cage,  elongated  from  before  to  behind, 
suspended  under  the  vertebrae  of  the  dorsal  region,  and  destined  to  contain 
the  principal  organs  of  resjiiration  and  circulation.  It  is  composed  of  bony 
arches  named  ribs,  thirty-six  in  number — eighteen  on  each  side — and  a  single 
piece,  the  sternum,  which  serves  for  the  direct  or  indirect  support  of  the 
inferior  extremities  of  the  ribs. 


THE    BONES  OF    THE    THORAX    IN    PARTICULAR. 

1.  Sternum  of  the  Horse. 

This  is  an  osteo-cartilaginous  body,  elongated  from  before  backwards, 
flattened  on  each  side  in  two-thirds  of  its  anterior  extent,  and  from  above 
to  below  in  its  posterior  third,  slightly  curved  on  itself,  and  situated  beneath 
the  thorax  in  an  oblique  direction  from  above  to  below,  and  before  to  behind. 
It  offers  for  study,  a  superior  face,  two  lateral  faces,  three  borders,  and  two 
extremities. 

Fig.  37.  • 


THE   STERNUM. 

1.  The  cervical  prolongation  (or  cariniform  cartilage);  2,  The  xiphoid  appendage  (or  ensiform 
cartilage;  3,  3,  Cavities  for  the  articulation  of  the  sternal  cartilages;  4,  Inferior  border. 

Faces. — The  superior  face,  slightly  concave  longitudinally,  represents  an 
isoscelated,  lengthened  triangle,  the  summit  of  which  is  directed  forwards ; 
it  constitutes  the  floor  of  the  tlioracic  cavity.  Each  lateral  face  comprises 
two  parts — a  superior  and  an  inferior.     The  first  shows  eight  diartbrodial 


THE  THORAX.  67 

cavities,  which  receive  the  inferior  extremity  of  the  cartilages  of  the  true 
ribs.  These  cavities  are  ehingated  vertically,  and  draw  closer  to  each  other 
as  they  extend  backwards.  The  inferior  part,  which  is  more  extensive  before 
than  behind,  offers  to  the  powerful  pectoral  muscles  a  largo  surface  for 
insertion. 

Bordelk. — The  twu  lateral  borders  separate  the  superior  from  the  lateral 
faces  ;  they  are  situatud  above  the  diarthrodial  cavities,  arc  united  anteriorly, 
and  each  gives  attachment  to  a  fibrous  band.  The  inferior  border  is  ojiposite 
the  suj)erior  face  ;  convex,  thin,  and  very  prominent  in  its  anterior  two-thirds, 
it  somewhat  resembles  the  keel  of  a  ship. 

Extremities. — The  anterior  flattened  on  each  side  and  curved  upwards, 
exceeds  to  some  extent  the  first  articular  cavity  of  the  lateral  faces,  and  in 
this  way  constitutes  the  cervical  prolongation  of  the  sternum.  The  posterior 
extremity  is  flattened  superiorly  and  inferiorly,  and  forms  a  large  cartila- 
ginous plate,  very  thin,  concave  above,  convex  below,  which  has  received  the 
name  of  the  abdominal  prolongation  (^ensiform  cartilage^  or  xiphoid  appendage. 

Structure  and  development. — The  sternum  is  one  of  the  parts  of  the  skeleton 
which  do  not  submit  to  complete  osseous  transformation.  It  is  developed, 
in  solii^eds,  from  six  single  centimes  of  sj^ongy  substance,  ranged  one  behind 
the  other,  like  beads  on  a  string.  These  centres  never  coalesce  to  form  a 
solid  piece,  but  remain  separated,  during  the  life  of  the  animal,  by  the 
primitive  cartilaginous  mass.  The  latter  constitutes  the  entire  anterior  pro- 
longation of  the  bone  and  its  carina,  as  well  as  the  xiphoid  appendage.  When 
these  parts  of  the  sternum  become  ossified,  which  is  rare,  it  is  only  partially. 

2.  Tlie  Bibs. 

As  has  been  already  noticed,  on  eacJi  side  of  the  thorax  eignteen  ribs  are 
counted.  These  are  nearly  parallel  to  each  other,  and  separated  by  the 
intervals  termed  the  intercostal  spaces.  Attached  by  their  suijcrior  extremity 
to  the  vertebras  of  the  dorsal  region,  these  bones  terminate  at  their  inferior 
extremity  by  an  elastic  and  flexible  prolongation,  named  the  costal  cartilage, 
by  means  of  which  they  are  brought  into  direct  or  indirect  relations  with 
the  sternum.  The  characters  common  to  all  the  ribs  will  be  first  noticed, 
then  the  special  features  which  serve  to  distinguish  them  from  each  other, 
and,  lastly,  the  differences  they  exhibit  in  other  than  soliped  animals. 

A.  Characters  coiMmon  to  all  the  Eibs. — These  will  be  studied  from  a 
typical  point  of  view,  first  in  the  rib  itself,  and  then  in  its  cartilage. 

1.  Description  of  a  typical  rib. — A  rib  is  an  elongated  symmetrical  bone, 
oblique  from  above  to  below,  and  from  before  to  behind,  flattened  on  both 
sides,  curved  like  a  bow,  and  twisted  on  itself  in  such  a  fashion  that  its  two 
extremities  cannot  rest  on  the  same  horizontal  plane.  It  is  divided  into  a 
middle  portion  and  two  extremities. 

Middle  portion. — This  offers  two  faces  and  two  borders.  The  external 
face  is  convex,  and  hollowed  by  a  wide  groove  in  its  anterior  half;  it  shows 
superiorly,  towards  the  point  corresjionding  to  the  angle  of  the  rib  in  Man, 
some  tubercles  and  muscular  imprints.  The  internal  face  is  concave  and 
smooth,  and  covered  by  the  pleura,  which  separates  it  from  the  lungs.  The 
anterior  border  is  concave,  thin,  and  sharp  ;  the  posterior,  convex,  thick,  and 
covered  with  rugged  eminences,  is  channeled  inwardly  by  a  vasculo-nervous 
fissure,  which  disappears  near  the  middle  of  the  rib. 

Extremities. — The  superior  has  two  eminences,  a  liead  and  a  tuberosity, 
which  serve  for  the  support  of  the  rib  against  the  spine.  The  first  is  formed 
by  two  articular  demi-facets,  placed  one  before  the  other,  and  separated  by  a 


G8 


THE  BONES. 


groove  for  ligamentous  insertion ;  it  is  isolated  from  the  tuberosity  by  a 
narrow  part,  named  the  nccJc,  which  exhibits  a  rugged  fossa  for  the  implanta- 
tion of  a  ligament.  The  second,  situated  behind  the  head,  and  smaller  than 
it,  is  provided  with  imprints  on  its  margin,  and  jn-esents  an  almost,  flat 
diarthrodial  facet  at  the  summit.  Each  rib  articulates  by  its  head  and 
tuberosity  with  two  dorsal  vertebrae ;  the  head  is  received  into»the  inter- 
Fig.  38. 


TYPICAL   RIBS  OF   THE   HORSE. 

A,  Inner  face  of  the  fifth  sternal  rib ;  B,  External  face  of  the  first  asternal  rib. — 
1,  Head  of  the  rib;  2,  Its  fissure;  3,  Neck;  4,  Tuberosity;  5,  Articular  facet; 

6,  Scabrous  fossa  for  the  insertion  of  the  interosseous  costo-transverse  ligament; 

7,  Groove  on  the  external  face ;  8,  Vasculo-nervous  groove  of  the  posterior 
border ;  9,  Prolonging  cartilage ;  10,  A,  Articular  tuberosity  for  union  with  the , 
sternum. 

vertebral  articular  cavity ;  the  tuberosity  corresponds,  by  its  facet,  to  the 
transv.erse  process  of  the  posterior  vertebra. 

The  inferior  extremity  is  tuberous  and  excavated  by  a  shallow  cavity, 
irregular  at  the  bottom,  for  the  reception  of  the  ujiper  end  of  the  costal 
cartilage. 

Structure  and  development. — The  ribs  are  very  spongy  bones,  especially 


TEE  THORAX.  69 

in  tlieir  inferior  moiety,  and  are  developed  at  a  very  early  period  by  three 
centres  of  ossification :  a  principal  for  the  middle  portion  and  inferior 
extremity,  and  two  complementary  for  the  head  and  tuberosity. 

2.  Description  of  a  typical  costal  cartihuje. — The  costal  cartilage  very 
evidently  represeuts  the  inferior  rib  in  birds ;  it  is  a  cylindrical  piece, 
slightly  compressed  at  the  sides,  and  round  and  smooth  on  its  faces  and 
borders.  By  its  superior  extremity,  it  is  united  to  .the  rib  it  serves  to 
lengthen,  and  forms  with  it  an  angle  more  or  less  obtuse,  opening  in  front. 
At  its  inferior  extremity,  it  is  terminated  by  an  articular  enlarge- 
ment, or  by  a  blunt  point.  In  youth,  the  costal  prolongations  are  entirely 
composed  of  cartilaginous  matter,  but  they  are  soon  invaded  by  ossification ; 
so  that  in  the  adult  animal  they  are  already  transformed  into  a  spongy 
substance,  with  large  areolae  which  remain  during  life  sm-rounded  by  a  thin 
layer  of  cartilage. 

B.  Specific  Characters  of  the  Eibs. — The  ribs,  like  the  vertebrae  of  each 
region  of  the  spine,  have  received  numerical  designations  of  first,  second,  third, 
etc.,  computing  them  from  before  to  behind.  (See  Fig.  1.)  Owing  to  the  pre- 
sence of  an  altogether  essential  characteristic,  they  are  naturally  divided  into 
two  great  categories:  the  sternal  or  true  ribs,  and  the  asternal  or  false  ribs. 
The  sternal  ribs,  numbering  eight  (the  first  eight),  have  their  cartilages 
terminating  inferiorly  by  an  articular  enlargement,  which  corresponds  to  one 
of  the  lateral  cavities  of  the  sternum,  and  brings  the  true  ribs  into  direct 
contact  with  this  portion  of  the  skeleton.  The  asternal  ribs,  ten  in  number, 
rest  on  each  other — the  last  on  the  seventeenth,  this  on  the  sixteenth,  and  so 
on — by  the  inferior  exti'emity  of  their  cartilage,  which  ends  in  a  blunt  point. 
The  cartilage  of  the  first  false  rib  is  united  somewhat  closely  to  the  last 
sternal  rib,  and  it  is  through  the  medium  of  this  that  all  the  asternal  ribs  lie 
indirectly  on  the  sternum. 

If,  however,  the  ribs  are  considered  altogether,  with  regard  to  the  differen- 
tial characters  presented  by  them  in  their  length,  width,  and  degree  of 
incurvation,  it  will  be  noted :  1,  That  their  length  increases  from  the  first 
to  the  ninth,  and  from  this  diminishes  progressively  to  the  last ;  2.  That  the 
same  progressive  increase  and  decrease  exists  in  the  cartilages ;  3,  That  they 
become  gi'adually  wider  from  the  fii'st  to  the  sixth  inclusive,  and  then  con- 
tract by  degrees  until  the  eighteenth  is  reached  ;  4,  That  the  curve  described 
by  each  is  shorter  and  more  marked  as  the  rib  is  situated  more  behind.  It 
may  be  added  that  the  channel  on  the  external  face  is  less  conspicuous  in 
proportion  as  the  rib  is  narrow. 

The  first  rib,  considered  individually,  is  always  distinguished  by  the 
absence  of  the  groove  on  its  outer  sxu'face,  the  vasculo-nervous  fissure  on  its 
posterior  border,  and  the  groove  or  notch  intermediate  to  the  two  facets  of 
its  articular  head.  It  is  also  recognised  by  the  deep  muscular  imprints  on 
its  external  face,  the  shortness  and  thickness  of  its  cartilage,  and  particularly 
by  the  articular  facet  which  this  cartilage  exhibits  inwardly,  to  correspond 
to  that  of  the  opposite  rib.  The  last  rib  has  no  channel  on  its  external 
surface  :  the  facet  of  its  tuberosity  is  confounded  with  the  posterior  facet  of 
the  head.  This  last  character  is  also  nearly  always  remarked  in  the 
seventeenth  rib,  and  sometimes  even  in  the  sixteenth. 

In  the  Ais  and  Mule,  all  the  ribs  in  general,  but  particularly  those  most 
posterior,  are  less  curved  than  in  the  Horse.  (In  the  Horse,  a  nineteenth 
pair  of  ribs  is  sometimes  found,  and  this  even  with  five,  and  at  other  times 
with  six  lumbar  vertebras  ;  it  happens  that  the  nineteenth  rib  is  formed  by 
the  transverse  process  of  the  fii-st  lumbar  vertebra,  and  at  times  a  ligament 
8 


70  TRE  BONES. 

is  given  off  from  this  process,  which  joins  it  to  a  pointed  bone  or  a  cartilage 
in  its  vicinity.  If  the  hymn  on  the  "  Sacrifice  of  the  Horse,"  in  the  most 
ancient  collection  of  Aryan  poems,  is  to  be  credited,  the  horses  of  antiquity 
in  Central  Asia  had  only  seventeen  pairs  of  ribs.  The  mobility  of  the  ribs 
is  scarcely  perceptible  in  the  first,  but  increases  until  the  ninth  or  tenth  is 
reached,  after  which  it  gradually  diminishes.) 

THE   THORAX    IN    GENERAL. 

The  description  of  the  interior  of  the  thoracic  cavity  will  be  referred  to 
when  treating  of  the  respiratory  apparatus.  It  is  only  necessary  here  to 
examine  the  external  sui'face  of  this  bony  cage ;  for  this  purpose  it  is 
divided  into  six  regions : — a  superior  plane,  an  inferior  plane,  two  lateral  planes, 
a  base,  and  a  summit. 

Planes, — The  superior  plane  is  separated  into  two  portions  by  the  spinous 
processes  of  the  dorsal  vertebrae  ;  each  forms,  with  these  spinous  processes,  the 
costo-vertehral  furrow,  intended  to  lodge  the  majority  of  the  muscles  belong- 
ing to  the  spinal  region  of  the  back  and  loins.  The  inferior  plane,  less 
extensive  than  the  preceding,  offers:  1,  On  the  median  line,  the  cariniform 
and  xiphoid  cartilages  of  the  sternum ;  2,  On  the  sides,  the  chondro-sternal 
articulations,  and  the  cartilages  of  prolongment  of  the  true  ribs.  The 
lateral  planes  are  convex  and  wider  at  their  middle  part  than  in  front  or 
behind,  and  exhibit  the  intercostal  spaces.  They  serve  to  give  support, 
anteriorly,  to  the  superior  rays  of  the  two  fore-limbs. 

Base. — This  is  circumscribed  by  the  posterior  border  of  the  last  rib,  and 
by  the  cartilages  of  all  the  asternal  ribs ;  it  is  cut  obliquely  from  above  to 
below,  and  from  before  to  behind.  It  gives  attachment,  by  its  internal 
circumference,  to  the  diaphragm,  a  muscle  which  separates  the  thoracic  from 
the  abdominal  cavity. 

Summit. — It  occupies  the  anterior  portion  of  the  thorax,  and  presents  an 
oval  opening,  elongated  vertically,  situated  between  the  two  first  ribs.  This 
opening  constitutes  the  entrance  to  the  chest,  and  gives  admission  to  the 
trachea,  the  oesophagus,  and  important  vessels  and  nerves. 

DIFFERENTIAL   CHARACTERS  OF   THE   THORAX   IN   OTHER   THAN   SOLIPED   ANIMALS. 

1.  Sternum. 

In  all  the  domesticated  animals  except  solipeds,  the  sternum  is  flattened  above  and 
below,  instead  of  from  side  to  side. 

Ruminants. — In  ruminants,  each  piece  is  developed  from  two  lateral  centres  of  ossifica- 
tion. The  bones  which  compose  it  are  seven  in  number;  they  are  mnch  more  compact 
than  those  in  the  sternum  of  the  horse,  and  at  an  early  period  are  united  to  each  other, 
with  the  exception  of  the  first,  which  is  joined  to  the  second  by  a  diarthrodi-al  articula- 
tion that  permits  it  to  execute  lateral  movements.  There  is  no  cervical  prolonojation, 
and  the  xiphoid  cartilage  is  feebly  developed  and  well  detached  from  the  body  of  the 
bone.  In  the  sternum  of  the  Gout  and  Sheep,  the  two  first  pieces  have  no  diarthrodial 
joint,  but  are  simply  united  by  a  layer  of  cartilage  which,  in  old  animals,  becomes 
completely  ossified. 

Pig. — The  sternum  of  this  animal  presents  in  its  general  conformation  the  essential 
features  of  that  of  large  ruminants.  It  is  provided  with  a  well-defined  cervical  prolonga- 
tion, and  is  composed  of  six  pieces  which,  at  least  in  the  four  or  five  last,  are  each 
divided  into  two  lateral  centres. 

Carnivora. — The  sternum  of  the  Doq  and  Cat  is  formed  of  eight  pieces  elongated  from 
before  to  behind,  hollowed  in  their  middle  part,  and  tliick  at  their  ends — formed,  indeed, 
like  the  last  coccygeal  vertebrie  of  the  Horse.    They  are  never  ossified  to  each  other. 


TEE  THOBAX. 


71 


2.  Eibs. 

The  number  of  ribs  varies  like  that  of  the  dorsal  vertebrje.  The  following  table 
indicates  the  number  of  these  bones  in  the  dili'eient  domesticated  animals. 

Pig 11 

Ox 13 

Sheep. 13 

Goat 13 

Dog 13 

Ersrrs-ANTS. — These  animals  have  eight  sternal  and  five  asternal  ribs. 

In  the  Ox,  they  are  longer,  wider,  and  less  arched  than  in  solipeds.  The  articular 
eminences  of  the  superior  extremity  are  volnmiuous  and  well  detached ;  the  neck 
espec;aliy  is  very  long.  The  sternal  ribs  axe  joined  to  their  cartilage  of  prolongment  by 
a  rtal  diaithrodial  articulation.  In  the  last  rib,  and  sometimes  in  the  one  before  it, 
the  tuberosity  is  scarcely  perceptible,  and  has  no  articular  facet.  In  the  Sheep  and  Goat, 
the  sternal  ribs  are  consolidated  with  the  cartilages  (see  fig.  5.) 

Pig. — In  this  animal  there  are  fourteen  pairs  of  ribs,  seven  of  which  are  sternal  and 
seven  asternal.  The  first  are  provided  with  •artilages  of  prolongment  flattened  on  both 
sides,  extremely  wide  and  sharp,  and  convex  on  their  superior  border.  In  the  four  last 
asternal  ribs,  the  facet  of  their  tuberosity  is  confounded  with  the  posterior  facet  of  the 
head.  (Otherwise,  tlie  ribs  of  the  Pig  resemble,  in  their  general  conformation,  those  of 
the  Sheep  or  Goat;  though  more  incurvated  and  wider.; 

Caenivoka. — They  possess   thirteen   ribs  Fig.  39. 

on  each  side — nine  sternal  and  four  asternal.  , 

These  are   very  much  arched,   narrow,  and  "/"Ss 

thick,  and  their  cartilages  rarely  ossify.     In  (j^^^iST^^^S^. 

the  Dog,  the  articular  facet  of  the  tuberosity  /^r 

remains  isolated  from  the  posterior  facet  of  .^^^.^      "S     'i^- 

the  head  in  all  the  ribs.     It  is  absent  in  the  ,i*^Si-^^^i^"  .'O 

three  last  ribs  of  the  Cat. 


OOSrPARISON   OF   THE    THORAX   OF   MAN   WITH 
THAT   OF   THE  DOMESTICATED    ANIMALS. 


1,  Sternum. 

The  sternum  of  IMan  is  flattened  before 
and  behind,  and  diminishes  in  width  from 
above  to  below  The  xiphoid  appendage  is 
narrow,  and  single  or  bifid.  Besides  the 
articular  surfaces  for  the  ribs,  there  are  found 
on  the  upper  end  two  lateral  notches  for 
articulation  with  the  clavicles. 

2.  Eibs. 

Of  the  twelve  ribs  in  INIan,  seven  are 
sternal  s  and  five  astemals.  They  are 
short,  narrow,  and  much  incurvated.  especially 
the  first  ones.  In  each  rib  the  curvature  is 
more  marked  in  the  posterior  fourth  or  fifth 
than  in  the  anterior  three-fourths  or  four- 
fifths  ;  this  sudden  change  of  curvature  is 
indicated  in  the  external  face  by  a  kind  of 
inflexion  and  thickening  called  the  angle  of 
the  ribs.  Tlie  prolonging  cartilages  of  the 
eleventh  and  twelfth  ribs  are  short,  and  are 
lost  in  tlie  texture  of  the  abdominal  parietes; 
for  this  reason  they  are  termed  the  ^oa^m^  (or 
false)  ribs  (see  fig.  39). 


THORAX  OF  MAN;  ANTERIOR  FACE. 

1,  Superior  piece  of  the  sternum;  2, 
Middle  piece,  or  body,  3,  Inferior  piece, 
or  ensiform  cartilage ;  4,  First  dorsal 
vertebra;  5,  Last  dorsal  vertebra;  6, 
First  rib ;  7,  Its  head ;  8,  Its  neck,  rest- 
ing against  the  transverse  process  of  the 
first  dorsal  vertebra ;  9,  Its  tubercle ;  10, 
Seventh,  or  last  true  rib;  11,  Costal  car- 
tilages of  the  true  ribs ;  12,  The  last  two 
false  or  floating  ribs ;  13.  The  groove 
alon?  the  lower  border  of  the  rib. 


Article  IV. — Anterior  Limbs. 
The  anterior  (or  thoracic)  limb  is  divided  into  four  secondary  regions 
the  shoulder,  arm,  fore-arm,  and  fore-foot  or  hand. 


72 


TEE  BONES. 


^-1f^^^»^ 


SHOULDER. 

In  solipeds,  tliis  region  has  for  its  base  a  single  bone,  tlie  sccqmla  or 
omojylat. 

Scapula. 

This  is  a  flat,  triangular,  and  asymmetrical  bone,  prolonged  at  its 
superior   border  by   a   flexible   cartilage,   articulated  interiorly   with   the 

humerus      only,     and     applied 
p,„  40  against  the  lateral  plane  of  the 

thorax  in  an  oblique  direction 
downwards  and  forwards.  It 
has  two  faces,  three  borders,  and 
three  angles. 

Faces. — The  external  face  is 
divided  by  the  scapular  or  acro- 
mian  spine,  into  two  cavities  of 
iniequal  width— the  supra  and 
infraspinous  (or  antea  and  postea 
spinatus)fossse.  The  spine  is  a  very 
salient  crest  which  runs  the  whole 
length  of  the  external  scapular 
surface ;  very  elevated  in  its 
middle  part,  which  shows  au 
ia-regular  enlargement — the  tube' 
rosity  of  the  spine  — it  insensibly 
decreases  towards  its  two  ex- 
tremities. The  supraspinous 
fossa,  the  narrowest,  is  situated 
above,  or  rather  in  front  of  the 
spine ;  it  is  regularly  concave 
from  side  to  side,  and  perfectly 
smooth.  The  infraspinous  fossa 
is  twice  the  width  of  the  pre- 
ceding, and  occupies  all  the  sur- 
face behind  the  spine.  It  ex- 
hibits: 1,  Below,  and  near  the 
posterior  border,  several  rows 
of  roughened  lines  for  muscular 
insertion  ;  2,  Near  the  neck,  the 
nutritious  foramen  of  the  bone, 
and  some  vascular  grooves. 
The  internal  face  is  excavated  in  its  centre  to  form  a  hollow  called  the 
subscapular  fossa,  which  is  prolonged  superiorly  by  three  diverging  points. 
The  median  point  extends  to  the  suj^erior  border  of  the  bone,  and  separates 
two  roughened  triangular  surfaces  destined  for  muscular  implantation. 

Borders. — The  superior  is  indented  by  an  irregular  groove  to  receive  the 
inferior  margin  of  the  cartilage  of  prolongment.  The  latter  is  convex  on  its 
superior  border,  extends  beyond  the  posterior  angle  of  the  bone,  and 
gradually  diminishes  in  thickness  as  it  leaves  its  point  of  attachment. 
In  old  horses  it  is  nearly  always  found  partially  ossified.  The  anterior 
border,  thin  and  sharp,  is  convex  in  its  superior  two-thirds,  and  slightly 
concave  for  the  remainder  of  its  extent.  The  posterior  is  thicker  and  a  little 
concave. 


THE  EIGHT  SCAPULA;    OUTER   SURFACE. 

I,  Antreior  border  ;  2,  Superior  margin  for  insertion 
of  cartilage ;  3,  Tuberosity  of  the  spine  ;  4,  Antea- 
spinatus  fossa ;  5,  Postea-spinatus  fossa ;  6,  Neck 
of  the  scapula ;  7,  Coracoid  process ,  8,  Glenoid 
cavitv. 


THE  AIsTERIOB  LIMBS. 


73 


Angles. — The  antei-ior  or  cervical  angle  is  the  thinnest  of  the  three.  The 
posterior  or  dorsal  angle  is  thick  and  tuberous,  The  inferior  or  humeral 
angle  is  the  most  voluminous,  aud  is  separated  from  the  remainder  of  the 
bone  by  a  slight  constriction,  which  constitutes  the  neck  of  the  scapula.  It 
exhibits :  1,  The  glenoid  cavity,  an  oval  diarthrodial  siu'face,  excavated  to  a 
slight  extent  to  receive  the  head  of  the  humerus,  notched  on  the  inner  side, 
and  bearing  on  the  external  margin  of  the  ridge  which  surrounds  it  a  small 
tubercle  of  insertion ;  2,  The  coracoid  process,  situated  in  front,  and  at  a 
certain  distance  from  the  glenoid  cavity.  This  is  a  large  eminence 
in  which  may  be  distinguished  two  parts  :  the  base,  a  thick  rugged  process ; 
and  the  summit,  a  kind  of  beak  curved  inwards. 

Structure  and  development. — Like  all  the  wide  bones,  the  scapula  is 
formed  of  two  compact  lamellfe  separated  by  spongy  tissue.  The  latter  is 
very  scanty  towards  the  centres  of  the  supra  and  infraspinous  fossae,  where  it 
is  often  altogether  wanting ;  it  is  most  abundant  in  p^^  ^^ 

the  angles.  The  scapula  is  developed  from  two  centi-es 
of  ossification,  one  of  which  forms  the  coracoid  pro- 
cess. 

AEil. 

This  region  has  only  one  bone,  the  Jiumerus. 

Humerus. 

The  Jiumerus  is  a  long  single  bone,  situated  between 
the  scapula  and  the  bone  of  the  fore-arm,  in  an  oblique 
direction  downwards  and  backwards.  Like  all  the  long 
bones,  it  offers  for  study  a  body  and  tuo  extremities. 

Body, — The  body  of  the  hmnerus  looks  as  if  it 
had  been  twisted  on  itself  from  within  to  without  in 
its  superior  extremity,  and  from  without  to  within  at 
the  opposite  end.  It  is  irregularly  prismatic,  and  is 
divided  into  four  faces.  The  anterior  face,  wider 
above  than  below,  has  in  its  middle  and  inferior  por- 
tions some  muscular  imprints.  The  posterior,  smooth 
and  rounded  from  one  side  to  the  other,  becomes 
insensibly  confounded  with  the  neighbouring  faces. 
The  external  is  excavated  by  a  wide  furrow,  which 
entirely  occupies  it,  and  turns  round  the  bone  ob- 
liquely from  above  to  below  and  behind  to  before , 
it  is  to  the  presence  of  this  channel  that  the  humerus 
owes  its  aj^parent  t^^■ist.  and  it  is  in  consequence 
designated  the  furroio  of  torsion  of  the  body  of  the 
humerus. 

This  fiirrow  is  separated  from  the  anterior  face 
by  a  salient  border,  the  anterior  crest  of  the  furrow 
of  torsion,  which  ends  inferiorly  above  the  coronoid 
fossa,  and  superiorly,  towards  the  upper  third  of  the 
bone,  by  the  imprint,  or  deltoid  tuberosity.  This  is  a 
roughened,  very  prominent  eminence,  flattened  before 
and  behind,  and  inclining  towards  the  furrow  of 
torsion  ;  by  its  superior  extremity  it  gives  origin  to 
a  cuiwed  line  which  is  carried  backwards  to  join  the 
base  of  the  articular  head.     Near  the  inferior  extremity,  backwards  and 


AXTERO-EXTERXAL  VIEW 
OF   RIGHT   HUMERUS. 

1,  Trochlear  or  bicipital 
ridges ;  2,  External  or 
deltoid  tuberosity ;  3, 
Head  or  articular  sur- 
face ;  4.  External  tuber- 
cle; 5,  Shaft  or  body  with 
its  twisted  furrow :  6. 7, 
Articular  or  trochlear 
condyles  ;  8,  Ulnar  fossa 
with  a  sulcus  ;  9,  Fossa 
for  the  insertion  of  the 
external  lateral  liga- 
ment. 


74 


THE  BONES. 


Fi2.  42. 


outwards,  is  seen  \}\q posterior  crest  of  the  furrow  of  torsion,  wbicbi  separates  the 
latter  from  the  posterior  face  of  the  bone.  The  internal  face  of  the  body  of 
the  humerus,  rounded  from  side  to  side,  is  not  separated  from  the  anterior 
and  posterior  faces  by  any  marked  line  of  demarcation.  It  offers,  near  its 
middle,  a  depressed  scabrous  process  for  the  insertion  of  the  adductor 
muscles — teres  major  and  great  dorsal — of  the  arm.  Towards  its  inferior 
third  it  shows  the  nutritive  foramen  of  the  bone. 

Extremities. — These  are  distinguished  into  superior  and  inferior.  Both, 
are  slightly  curved,  the  first  backwards,  the  second  forwards,  a  disposition 
which  tends  to  give  to  the  humerus  the  form  of  an  S. 

TJie  superior  extremity  is  the  most  voluminous,  and  has  three  thick 
eminences  ;  a  posterior,  external,  and  internal.  The 
first  constitutes  the  liead  of  the  humerus;  it  is  a 
very  slightly-detached  articular  eminence,  rounded 
like  the  segment  of  a  sphere,  and  corresponding  to 
the  glenoid  cavity  of  the  scapula,  which  is  too  small 
to  receive  it  entirely.  The  external  eminence,  named 
the  trochiter,  large  trochanter,  and  g7-eat  tuherositij,  com- 
prises three  portions,  named  the  summit,  convexity,  and 
crest  of  the  great  tuberosity.  The  internal  eminence, 
the  trochin,  little  trochanter,  or  small  tuberosity,  also 
presents  three  distinct  portions,  which,  by  their  posi- 
tion, correspond  exactly  with  the  three  regions  of 
the  large  trochanter :  these  are  so  many  muscular 
facets. 

The  great  and  small  trochanters  are  separated 
from  one  another  in  front  by  a  channel  called  the 
bicipital  groove,  because  the  superior  tendon  of  the 
biceps  muscle  glides  over  it;  it  consists  of  two 
vertical  grooves  with  a  median  ridge  between 
them. 

The  inferior  extremity  of  the  humerus  has  an 
articular  surface  corresponding  to  the  radius  and  ulna. 
This  surface,  elongated  transversely,  convex  from 
before  backwards,  and  of  greater  extent  within  than 
without,  exhibits  two  trochlea  separated  by  an  antero- 
posterior relief. 

The  median  or  internal  trochlea,  the  deepest,  is 
limited  internally  by  a  kind  of  voluminous  condyle, 
Articular  head  of  the  which  corresponds  to  the  inner  lip  of  the  humeral 
bone;  4,  External  tu-  ti'ochlea  of  Man.  The  external  trochlea  is  bordered 
outwardly  by  a  slightly  salient  lip,  which  corresponds 
to  the  condyle  of  the  humerus  of  Man.  Above  and 
behind  this  articular  surface  is  a  wide  deep  fossa,  the 
olecranian  (or  condyloid),  so  named  because  it  lodges  the 
rostrom  of  the  olecranon  in  the  extension  movements  of  the  fore-arm.  It  is 
bordered  by  two  eminences,  the  external  of  .which  is  less  elevated  than  the 
internal.  The  first  represents  the  epitrochlea,  and  the  second  the  epi- 
condyle,  of  the  humerus  of  Man.  In  front,  and  above  the  inner  trochlea, 
there  is  another,  but  less  spacious  fossa,  which  receives  the  coronoid  pro- 
cess during  extreme  flexion  of  the  fore-arm,  and  which,  for  this  reason,  it 
would  be  convenient  to  designate  as  the  coronoid  fossa.  Lastly,  at  the 
extremities   of  the  transverse  axis    of  the    inferior  articular  sui'face    is 


POSTERIOR   VIEW   OF    THE 
RIGHT    HUMERUS. 

2,  External  tuberosity ;  3, 


bercle  and  ridge ;  5, 
Body  or  shaft  of  the 
bone ;  10,  Condyloid 
fossa. 


THE  ANTERIOR  LIMBS.  75 

remarked :   outwardly,  an  excavation  for  ligamentous  insertion ;  inwardly, 
a  small  tuberosity  intended  for  the  same  purpose.^ 

Structure  and  development. — The  humerus,  like  all  the  long  bones,  is 
only  spongy  at  its  extremities.  It  is  developed  from  six  points  of  ossi- 
fication ;  one  of  which  alone  forms  the  body,  one  the  head  and  the  small 
trochanter,  another  the  large  trochanter,  a  foiu'th  the  inferior  articxilar 
surface,  a  fifth  the  epicoudyle,  and  the  last  for  the  epitrochlea.  The  latter  is 
sometimes  absent. 

FORE -ARM. 

This  region  has  for  its  base  two  bones,  the  radius  and  cubitus  (or  ulna') 
united  into  a  single  piece  at  an  early  period  in  most  of  the  domesticated 
animals. 

1.  Badius. 

This  is  a  long  bone,  placed  in  a  vertical  direction  between  the 
humerus  and  the  first  row  of  carpal  bones,  and  divided  into  a  body  and 
two  extremities. 

Body. — Slightly  arched  and  depressed  from  before  to  behind,  the  body 
presents  for  study  two  faces  and  two  borders.  The  anterior  face  is  convex 
and  perfectly  smooth.  The  posterior,  a  little  concave  from  one  extremity  to 
the  othei-,  offers  :  1,  Near  the  external  border,  a  triangular  surface,  covered 
with  asperities,  elongated  vertically,  very  narrow,  commencing  near  the 
upper  fourth  of  the  bone  and  terminating  in  a  fine  point  towards  the  lower 
fourth :  this  surface  is  brought  into  contact  with  the  anterior  face  of  the 
ulna  by  an  interosseous  ligament,  which  is  completely  ossified  before  the 
animal  reaches  adult  age ;  2,  Above,  there  is  a  wicle,  transverse,  but  shallow 
groove,  which  aids  in  forming  the  radio-iilnar  arch  and  shows,  near  the  point 
where  it  touches  the  preceding  surface,  the  nutrient  foramen  of  the  bone ; 
3,  Near  the  internal  border,  and  towards  the  inferior  third,  there  is  a  ver- 
tically elongated  and  slightly  salient  eminence  of  insertion.  The  two 
borders,  external  and  internal,  are  thick  and  rounded;  they  establish  an 
insensible  transition  between  the  faces. 

Extremities. — The  superior  is  larger  than  the  inferior.  It  has :  1,  An 
articular  surface  elongated  from  one  side  to  the  other,  concave  from  before 
to  behind,  wider  within  than  without,  and  moulded  to  the  articular  surface 
of  the  inferior  extremity  of  the  humerus ;  there  is  also  seen,  outwardly,  a 
double  gorge  which  receives  the  two  lips  of  the  external  trochlea ;  in  the 
middle,  an  antero-jiosterior  ridge  which  is  received  into  the  internal  trochlea  ; 
within,  an  oval  cavity  corresponding  to  the  internal  border  of  the  former ; 
2,  The  external  tuberosity,  placed  at  the  extremity  of  the  great  diameter  of 
the  articular  surface ;  it  is  prominent  and  w  ell  detached  ;  3,  The  internal  or 
bicipital  tuberosity,  a  large,  very  rugged,  and  dej^ressed  process,  situated 
within  and  in  front  of  the  glenoid  cavity ;  4,  A  little  lower,  and  on  the  same 
side,  there  is  a  strong  muscular  and  ligamentous  imprint,  separated  from  the 
preceding  tuberosity  by  a  transverse  groove  intended  for  the  passage  of  a 
tendinous  branch  ;  5,  The  coronoid  process?  a  small  conical  eminence,  at  the 
summit  of  which  terminates,  anteriorly,  the  median  ridge  of  the  articular 

•  The  articular  surfaces  which,  in  veterinary  anatomy,  have  received  the  names  of 
trochlea  and  condyle,  not  being  the  same  as  in  human  anatomy,  there  results  an  annoying 
inversion  of  the  situation  of  the  epitrochlean  and  epicondyloid  eminences,  so  named.  It 
has  tlierefore  been  our  endeavour  to  remedy  the  improper  employment  of  these 
denominations,  which  has  been  a  cause  of  error  in  comparative  anatomy.' 

^  In  Man  this  belongs  to  the  ulna. 


76 


THE  BONES. 


Fis.  43. 


surfixce ;  6,  Two  diartlirodial  facets  elongated  transversely,  cut  on  tho 
posterior  outline  of  tlie  large  articular  surface,  with  which  they  are  con- 
founded by  their  superior  border ;  they  correspond 
to  similar  facets  on  the  ulna ;  7,  Below  these,  a 
roughened  surface  which  extends  to  the  radio- 
ulnar arch,  and  is  in  contact  with  an  analogous 
surface  of  the  same  bone  through  the  medium  of 
an  interosseous  ligament;  iu  the  Horse  this  liga- 
ment rarely  ossifies. 

The  inferior  extremity,  flattened  from  before 
to  behind,  presents :  1,  Below,  an  articular  sur- 
face elongated  transversely  and  somewhat  irregu- 
lar, responding  to  the  four  bones  in  the  upper 
row  of  the  carpus;  2,  On  the  sides,  two  tube- 
rosities for  ligamentous  insertion,  the  internal 
salient  and  well  circumscribed,  the  other  external 
and  excavated  by  a  vertical  fissure,  in  which  jiasses 
a  tendon ;  3,  In  front,  three  grooves  for  the 
gliding  of  tendons  ;  the  external  is  the  largest,  and 
vertical  like  the  median ;  the  internal,  the  nar- 
rowest, is  oblique  downwards  and  inwards;  4, 
Posteriorly,  a  strong  transverse  ridge  which  sur- 
mounts the  articular  surface  and  serves  for  the 
insertion  of  ligaments. 

Structure  and  develnpment.  The  radius  is  a 
very  compact  bone,  and  is  developed  from  three 
centres  of  ossification :  one  for  the  body  and  two 
for  the  extremities. 

2.  Ulna. 

This  is  an  elongated,  asymmetrical  bone,  in 
the  form  of  an  inverted  triangular  pyramid,  applied 
against  the  posterior  face  of  the  radius,  to  which 
it  is  united  in  adult  solipeds.  It  offers  for  des- 
cription a  middle  portion  and  two  extremities. 

Middle   portion. — This  has   three  faces   wider 

above  than  below,  and  three  herders  which  become 

joined  at  the  inferior  extremity  of  the  bone.     The 

6,  Radio-ulnai- articular  sur-   external  face  is  smooth  and  nearly  plane.     The 

faces  for  the  humerus;  7,   internal   is   also   smooth   and    slightly   hollowed. 

Bicipital     tuberosity;     8,    rpj^^  anterior  is  formed  to  correspond  to  the  radius, 

Shaft  or  body  ot  the  radius ;  -,  ,  ,.      ...  i  j.      ii  i 

9,  Grooves  for  tendons.  and  presents  peculiarities  analogous  to  those  of 

the  posterior  face  of  that  bone.     Thus  there  is 

found   in   proceeding   from   above   to   below:    1,  Two   small   diarthrodial 

facets  ;^    2,  A  rough  surface ;    3,  A  transverse  groove  for  the  formation  of 

the  radio-ulnar    arch ;    4,  A  triangular   surface,  studded   with    rugosities, 

which  occupies  the  remainder  of  the  bone  to  its  lower  extremity.    The  lateral 

borders,    external  and  internal,  are  sharp,  and,  like  the  anterior  face,  are  in 

contact  with  the  radius.    The  posterior  harder  is  concave,  rounded,  and  thicker 

than  the  other  two. 

Extremities. — The  superior  extremity  comprises  all  that  portion  which 
exceeds  the  articular  surface  of  the  radius.     It  constitutes  an  enormous 
*  It  is  represented  iu  Man  by  the  smaller  sigmoid  notch. 


KXTERXAL   FACE   OF   THE 
RADIUS   AND   ULNA. 

1,  Ulna;  2,  Point  of  the  ole- 
cranon ;  3,  Beak  of  the  ole- 
cranon ;  4,  Radio-ulnar  arch ; 
Supero-external  tuberosity ; 


TEE  ANTERIOR  LIMBS. 


77 


Fi2.  44. 


process — the  olecranon — flattened  on  both  sides,  and  presenting:  1,  An 
external  face,  sliglitly  convex;  2,  An  internal  excavated  face;  3,  An 
anterior  border,  tbiu  and  sharp  superiorly, 
notched  below  to  for  mthe  sigmoid  cavity  ^  an 
articular  surface  concave  from  above  down- 
wards, rounded  from  one  side  to  the  otlier, 
which  corresponds  -with  the  himieral  cavity, 
and  is  surmounted  by  a  salient  prolongation 
named  the  heak  of  the  olecranon ;  4,  A  con- 
cave and  smooth  posterior  border ;  5,  The 
summit,  a  kind  of  thick  roughened  tuberosity 
which  terminates  the  olecranon  above,  and  into 
which  are  inserted  the  extensor  muscles  of  the 
fore-arm. 

At  its  inferior  extremity,  the  ulna  ends, 
towards  the  lower  fourth  of  the  princijial  por- 
tion of  the  fore-arm,  in  an  acute  point,  and 
sometimes  by  a  small  knob  {capitidum  ulme). 
It  is  not  rare  to  see  it  prolonged,  especially 
in  the  Ass  and  Mule,  to  the  inferior  external 
tuberosity  of  the  radius.  This  tuberosity  then 
appears  to  belong  to  it,  at  least  in  part ;  and 
all  that  portion  which  is  situated  behind  its 
vertical  groove  might  be  justly  considered  as 
belonging  to  the  ulna. 

Structure  and  development. — The  ulna  con- 
tains much  compact  tissue,  even  in  the  region 
of  the  olecranon ;  it  is  also  very  solid.  It  is 
an  imperfect  bone,  developed  from  two  centres 
of  ossification  only,  one  of  these  being  for  the 
apex  of  the  olecranon. 

FOKE-FOOT    OE    HA^•D. 

The  anterior  foot,  or  hand,  is  the  region 
which  presents  the  greatest  difierences  when  it 
is  inspected  in  the  various  individuals  of  the 
animal  series.  Nevertheless,  in  all  the  mam- 
malia tlie  constitution  of  the  hand  is  funda- 
mentally the  same,  and  may  be  divided  into 
three  sections :  the  carpus,  metacarpus,  and 
pJicdangeal  region. 

The  hand  is  formed  by  five  parallel  or  1,  Radius;  2,  Groove  for  the  an- 
quasi-parallel  rays  that  constitute  the  digits,  ^"'^"^  '^*'°'°^  "^  ^^'  P^-''^''^^- 
each  of  which  is  efiectively  or  virtually  com- 
posed of  two  superposed  carpal,  a  metacarpal, 
and  three  phalangeal  hones,  forming  altogether 
the  digit,  properly  so  called.  But  this  typical 
composition,  established  through  the  labours 
of  MM.  Joly  and  Lavocat,  is  rarely  found  to 
be  realised  in  a  complete  manner. 

The  following  is  what  is  presented  in  the  hand  of  Man,  who  is  the  most 

'  The  greater  sigmoid  cavity  of  Man. 


EIGHT   FOEE-FOOT   OF   A   HOESE. 


ges ;  3,  Scaphoides ;  4,  Lunare ; 
5,  Cuneiform  ;  6,  Trapezium  ; 
7,  Magnum ;  8,  Unciform  ;  9, 
Metacarpal ;  10,  Small  meta- 
carpal;  11,  Sesamoid  bone;  12, 
Sutiraginis ;  13,  Coronary;  14, 
Navicular;  15,  Pedal;  16,  Its 
ala. 


78  TEE  BONES. 

perfect  pentadactylous  type.  The  carpus  is  composed  of  eight  bones,  the 
metacarpus  of  live  small,  parallel,  bouy  columns ;  the  phalangeal  region  of  five 
digits — thumb,  index,  medius,  annularis,  and  auricuktris,  formed  each  of  three 
phalanges,  with  the  exception  of  the  thumb,  which  has  only  two. 

In  the  domesticated  animals,  the  constitution  of  the  hand  is  more  or  less 
removed  from  this  type,  in  consequence  of  abortive  development,  which 
diminishes  either  the  number  of  rays,  or  the  number  of  pieces  composing 
these. 

Thus,  in  the  Cat  and  Pig  there  are  eight  bones  in  the  carpus ;  but  in  the 
Dog  and  Horse  there  are  no  more  than  seven ;  in  the  Ox  and  Sheep  there  are 
only  six,  for  in  them  two  or  three  bones  are  fused  together. 

The  metacarpus  of  the  Dog  and  Gat  has  certainly  five  metacarpal  bones, 
but  the  metacarpus  of  the  Pig  has  no  more  than  four,  that  of  the  Horse  three, 
and  that  of  Puminanis  only  two.  In  the  metacarjjus  of  the  Pig  the  fifth  bone 
is  not  developed.  In  the  Horse  it  is  entirely  absent ;  the  fourth  and  first  are 
independent,  and  the  third  and  second  are  confounded  to  form  a  voluminous 
bone  which  has  been  named  the  principal  (or  large)  metacarpal.  In  Ruminants, 
the  fourth  and  fifth  metacarjials  are  quite  imperfect,  the  first  being  arrested 
in  its  development,  and  the  second  and  third  becoming  consolidated  as  in 
the  horse. 

Lastly,  it  is  noted  that  the  digital  region  of  Carnivora  has  five  digits, 
the  Pig  four,  Ruminants  two,  and  Solipeds  only  one.  In  the  Pig,  the  thumb 
is  undeveloped ;  in  ruminants  it  is  completely  absent,  and  the  first  and 
fourth  are  represented  by  two  small  bones  situated  behind  the  metacarpo- 
phalangeal articulation ;  while  in  solipeds  the  single  digit  already  mentioned 
results  from  the  fusion  of  the  auricularis  and  medius. 

From  this  preliminary  synthetical  exposition,  it  will  be  easy  to 
understand  the  description  of  the  bones  composing  the  hand  in  solipeds. 

1.  Carpal  Bones. 

The  carpus  forms  the  base  of  the  hand.  Situated  between  the  inferior 
extremity  of  the  radius  and  the  superior  extremity  of  the  metacarpal  bones, 
it  is  composed  of  several  small  bones  joined  to  each  other  in  the  fresh  state 
by  extremely  solid  articular  bands.  Collectively,  they  form  an  almost 
quadrilateral  mass  in  which  may  be  distinguished  two  faces  and  four 
borders. 

The  anterior  face  is  slightly  convex  from  side  to  side  and  irregular ;  it 
corresponds  to  the  tendons  of  the  extensor  muscles  of  the  metacarpus  and 
phalanges. 

T^he  posterior  face  is  very  unequal  and  converted,  especially  outwardly, 
into  a  groove  in  which  the  tendons  of  the  flexor  muscles  of  the  phalanges 
glide. 

The  superior  harder  articulates  with  the  radius ;  the  inferior  border  with 
tbe  metacarpal  bones. 

The  lateral  borders  are  nearly  level ;  above  and  behind  the  external  border 
is  remarked  a  considerable  eminence,  formed  by  the  bone  which  will  be 
hereafter  studied  as  the  supercarpal  bone  (or  trapezium). 

In  the  carpus  of  the  Horse  are  seven  bones,  which  are  disposed  in  two 
superposed  rows.  The  superior  row  comprises  four  bones  placed  side  by 
side,  and  designated  by  the  numerical  names  of  first,  second,  third,  and  fourth, 
viewing  them  from  without  to  within.  The  inferior  row  has  only  three, 
which  are  named  in  the  same  manner. 


THE  ANTERIOR  LIMBS.  79 

In  applying  to  them  the  names  proposed  by  Liser,  we  have,  in  the  upper 
row: 

1.  The  pisiform,  or  supercarpal  bone  (trapezium); 

2.  The  pyramidal  (or  cuneiform)  bone ; 

3.  The  semilunar  (or  lunare)  bone 

4.  The  scaphoid  bone ; 

In  the  Inferior  row  : 

1.  The  hook  or  unciform  bone  ; 

2.  The  great  bone  or  capitatum  (magnum) ; 

3.  The  trapezoid  bone.^ 

The  description  of  these  bones  is  most  simple,  and  may  be  made  in  a 
general  manner  for  all.  Thus,  with  the  exception  of  the  supercarpal  bone, 
they  are  solids,  nearly  cubical  in  form,  and  exhibit  on  their  periphery : 
1,  Articular  surfaces  ;  2,  Surfaces  of  insertion. 

The  articular  surfaces  represent  small,  flat,  or  slightly-undulating  facets, 
distributed  on  the  superior,  inferior,  and  lateral  surfaces ;  none  are  found  in 
front  or  behind.  The  sujierior  and  inferior  faces  are  entirely  occujDied  by 
a  single  facet  which  responds  either  to  the  radius,  the  metacarpal,  or  to  the 
bone  of  the  other  row.  The  lateral  facets  are  always  multiple  and  in  contact 
with  the  bones  of  the  same  tier  ;  they  do  not  exist,  of  course,  on  the  eccentric 
side. of  the  first  and  third  bones  of  the  superior  or  inferior  rows. 

The  surfaces  of  insertion  are  absent  on  the  superior  and  inferior  faces : 
they  separate,  in  the  form  of  roughened  foss^,  the  lateral  articular  facets. 
Before  and  behind  they  are  covered  by  more  or  less  marked  rugosities. 

Bones  of  the  Upper  or  Antibrachial  Eow. — The  first,  or  os  ■pisiforme, 
is  without  the  I'ow ;  it  is  situated  above  and  behind  the  carpus,  from  whence 
its  name  of  supercarpal  hone,  by  which  it  is  usually  known  in  veterinary 
anatomy.  This  bone,  which  merits  a  sjiecial  description,  represents  a  disc 
flattened  on  both  sides,  offering  for  study  two  faces  and  a  circumference. 
The  external  face  is  convex,  roughened,  and  channeled  anteriorly  by  a 
groove  that  traverses  it  from  above  to  below,  and  in  which  glides  the 
inferior  tendon  of  the  external  flexor  of  the  metacarpus.  Its  internal  face, 
smooth  and  concave,  concurs  to  form  the  external  wall  of  the  carpal  sheath. 
The  circumference  presents,  in  front,  two  articular  facets  :  the  superior, 
concave,  corresponds  to  the  radius ;  the  inferior,  convex,  is  in  contact  with 
the  second  bone  of  the  upper  row. 

The  other  three  bones  of  this  row  increase  in  volume  from  without  to 
within. 

The  second,  or  os  pyramidalis  (or  cuneiform^,  responds  to  the  radius, 
the  first  bone  of  the  lower  row,  the  third  of  the  upper,  and  the  supercarpal 
bone  ;  it  has  in  all  five  articular  facets. 

The  third,  or  os  semilunare  {lunare'),  has  six  facets,  and  is  united  below  to 
the  first  and  second  bones  of  the  second  row. 

'  The  analogue  of  the  trapezium  of  Man  is  not  found  in  the  Horse.  According  to  M. 
Lavocat,  we  ought  to  regard  as  such  a  small  supernumerary  bone  sometimes  seen  articu- 
lating behind  the  third  bone.  We  are  entirely  of  his  opinion.  (Leyh  is  also  of  this 
opinion,  and  states  that  this  supernumerary  bone  is  more  frequently  found  in  large 
common-bred  horses.  Stubbs,  in  his  old,  but  fine  '  Anatomy  of  the  Horse,'  does  not  refer  to 
it,  but  describes  the  seventh  bone  as  the  pisiform.  Percivall  says  the  supernumerary  bone 
is  not  invariably  present,  and  that  sometimes  two  are  found.  He  designates  Stubbs'  and 
Chauveau's  pisiform  bone  as  tlie  trapezium.  Girard  names  the  supernumerary  bone  the 
"pisiform  "  or  pea-shaped.  When  one  or  more  of  these  osseous  nodules  are  present,  they 
represent  the  poUex  and  fifth  digit  of  the  human  hand.) 


80 


TEE  BONES. 


The  fourth,  or  os  scapJiokles,  the  most  voluminous  of  the  row,  has  only 
four  facets,  and  articulates  by  its  inferior  face  with  the  os  maonum  and 
tra^jezoides. 

Collectively,  the  second,  third,  and  fourth  bones  of  the  upper  row  form 
two  articular  surfaces. 

The  superior,  or  radial  articular  surface,  is  very  irregular ;  but  in  ex- 
amining it  from  without  to  within  there  may  be  observed:  1,  A  glenoid 
cavity  on  the  pyramidal  bone ;  2,  In  front,  a  transversely-elongated  condyle 


Fig.  45. 


Ficr.  46. 


POSTERIOR   VIEW   OF   THE   RIGHT 
CARPUS. 

1,  Second  cuneiform,  or  pyramidalis ;  2, 
Third,  or  lunare  ;  3,  Fourth,  or  sca- 
phoides;  4,  First,  supercarpal,  pisiform, 
or  trapezium  ;  5,  First  of  lower  row, 
or  unciform;  6,  Second,  or  magnum; 
7,  Third,  or  trapezoides  ,  *,  *,  Small 
metacarpal  bones. 


FRONT   VIEW  OF   RIGHT   CARPUS, 

1,  Second  of  upper  row,  or  cuneiform ; 
2,  Third,  or  lunare ;  3,  Fourth,  or 
scaphiiides ;  4,  First,  supercarpal,  or 
trapezium ;  5,  First  of  second  row,  or 
unciform ;  6,  Second,  or  magnum ; 
7,  Third,  or  trapezoides. 


on  the  semilunar  and  scaphoid  bones ;  3,  A  groove  placed  behind  the  pre- 
ceding condyle. 

The  inferior  articulating  surface,  which  corresponds  to  the  second  row, 
is  constituted  by  several  imdulated  facets ;  it  is  convex  outwardly  and  in 
front,  concave  posteriorly  and  inwardly. 

Bones  of  the  Inferior  or  Metacarpal  Eow. — The  thickness  of  these 
bones  decreases  from  without  to  within. 

The  first,  unciform,  or  hoolchone  (os  hamatum),  has  four  diarthrodial 
facets,  and  responds,  above,  to  the  two  first  bones  of  the  superior  row ; 
below,  to  the  first  and  second  metacarpals. 

The  second,  os  magnum,  or  os  ccqntatum,  the  largest,  has  seven  articular 
facets,  three  of  which  are  on  the  interno-lateral  face.     It  articulates,  above, 


TUB  AXTEniOR  LIMBS. 


81 


vnth.  the'"  semilunar  and  scaphoides ;  below,  with  the  principal  metacarpal 
and  the  internal  rudimentary  metacariial. 

The  third,  or  trapezoides,  the  smallest,  is  provided  with  five  facets,  and 
is  in  contact  with  the  scaphoides  abovr,  and  the  middle  and  internal  meta- 
cai'pals  below. 

Collectively,  these  bones  of  the  lower  row  form  two  Fig-  47. 

large  diarthrodial  surfaces.     The  upper  surface  resi^onds      ,^  j 

to  the  bones  of  the  upper  row,  and  is  constituted  in  front, 
and  from  without  to  within,  by  a  small  condyle  and  two 
glenoid  cavities ;  behind,  by  two  isolated  condyles, 
formed  by  the  os  magnum  and  the  trapezoides.  The 
inferior  articular  surface  is  only  formed  by  more  or  less 
long  and  plane  facets,  which  incline  towards  each  other. 
It  corresponds  to  the  three  portions  of  the  metacarpus. 

Structure  and  development. — Each  carpal  bone  is 
formed  by  a  nucleus  of  close  sj)ongy  substance  enveloped 
in  a  layer  of  compact  tissue.  Each  is  developed  from 
a  single  centre  of  ossification. 

2.  Metacarpal  Bones. 

In  Solipeds,  the  metacarpus  is  composed  of  three 
bones,  named  the  "  metacarpals,"  standing  parallel  to  each 
other.  These  are  the  principcd  metacarpcd  and  the  two 
rudimentary  metacarpals,  an  external  and  internal. 

Principal  Metacarpal. — This  is  a  long  cylindrical 
bone,  situated  vertically  between  the  carjjus  and  the 
digital  region. 

Body. — The  body  is  a  little  depressed  before  and 
behind,  a  disposition  which  permits  it  to  be  described 
as  "having  two  faces  and  two  borders.  The  anterior  face 
is  perfectly  smooth  and  rouurled  from  side  to  side.  The 
posterior  face  is  flat,  and  exhibits  :  1,  Towards  the  upper 
third,  the  nutritive  foramen  of  the  bone ;  2,  On  the 
sides,  two  narrow,  roughened  surfaces,  parallel  and  elon- 
gated vertically,  commencing  near  the  superior  extremity 
to  disappear  a  little  below  the  middle  of  the  bone  ;  these 
siu'faces  are  held  in  apposition  with  the  rudimentary 
metacarpals  by  means  of  an  interosseous  ligament  which 
is  often  ossified  in  old  horses.  The  borders,  external  and 
internal,  are  very  thick,  round,  and  smooth,  like  the  an- 
terior face. 

Extremities. — The  superior  is  flattened  before  and 
behind,  and  presents :  1,  Above,  an  undulating  articu- 
lately sui-face,  formed  by  the  imion  of  several  flat 
facets  more  or  less  inclined  on  one  another :  they 
respond  to  all  the  lower  row  of  carpal  bones ;  2.  An- 
teriorly and  inwardly,  a  tuberosity  for  muscular  inser- 
tion :  3,  Posteriorly,  and  directly  above  the  roughened 
surfaces  of  the  posterior  face,  four  small  diarthrodial  facets  in  pairs,  and 
running  into  the  larger  articular  surface  by  their  superior  border:  they  are 
adapted  to  similar  facets  on  the  rudimentary  metacarpals.  The  inferior 
extremity,  elongated  transversely,  corresponds  to  the  first  plialanx  and  the 
large  sesamoids  by  an  articular  surface,  convex  fi-om  before  to  behind,  which 


POSTERIOR    VIEW   OF 
EIGHT    METACARPUS. 

1,  Head  of  large  meta- 
carpal bone  for  ar* 
ticulation  with  the 
trapezoides,  mag- 
num, and  unciform ; 
2,  Inner  splint,  or 
small  metacarpal 
bone,  for  articula- 
tion with  the  trape- 
zoides ;  4,  Scabrous 
siirface  for  the  at- 
tachment of  the  sus- 
pensory ligament  ; 
5,  Isutrient  fora- 
men ;  6,  Median 
ridge  separating  the 
two  inferior  con- 
dyles. 


82  THE  BONES. 

is  composed  of  two  lateral  condyles  separated  by  a  median  spine.  The  two 
condyles  would  be  exactly  alike,  if  the  antero-posterior  diameter  of  the 
external  condyle  was  not  less  extensive  than  that  of  the  opj)osite  condyle. 
Both  are  hollowed  on  the  sides  by  an  excavation  for  the  attachment  of 
ligamentous  fasciculi.  • 

Structure  and  development. — The  principal  metacarpal  is  one  of  the 
most  comj^act  bones  in  the  body.  It  is  developed  from  two  centres  of 
ossification,  one  of  which  is  for  the  inferior  extremity. 

EuDiMENTARY  METACARPALS. — The  two  rudimentary  (small)  metacarpal 
(or  splint)  bones  are  elongated,  and  placed  against  the  posterior  face  of  the 
principal  bone,  one  without,  the  other  within.  Each  is  in  the  form  of  an 
inverted  pyramid,  and  exhibits  a  middle  j?a7-t  and  tico  extremities. 

Middle  portion. — Prismatic  and  triangular,  this  offers  :  ],  Three  faces, — an 
external,  smooth  and  rounded  from  one  border  to  the  other ;  an  interval, 
plane,  and  equally  smooth ;  an  anterior,  covered  with  asperities  to  give 
attachment  to  the  interosseous  ligament  uniting  the  lateral  metacarpal  bone 
to  the  median ;  2,  Three  salient  borders  which  markedly  separate  the  faces 
from  each  other. 

Extremities. — The  snpenor,  the  largest,  is  named  the  /ifrt(?,  and  shows :  above, 
a  diarthrodial  facet  which  corresponds  to  one  or  two  bones  of  the  inferior  row 
of  the  carpus ;  in  front,  other  two  small  facets  continuous  with  the  pre- 
ceding, and  in  contact  with  similar  facets  on  the  median  metacarpal  bone ; 
on  the  other  points  of  its  periphery  are  rugosities  for  the  attachment  of 
ligamentous  and  tendinous  fibres.  The  inferior  extremity  only  reaches  to 
abotit  the  lower  fourth  of  the  large  metacarpal  bone,  and  terminates  in  a 
small  enlargement  or  button,  which  is  never  consolidated  with  the  latter. 

The  two  lateral  metacarpals,  although  very  much  alike,  may  yet  be 
easily  distinguished  from  each  other.  For  instance,  the  internal  bone  is 
always  the  thickest  and  often  the  longest ;  besides,  the  superior  articular 
surface  of  its  head  results  from  the  union  of  the  two  facets  corresponding 
to  the  two  last  carpal  bones  of  the  lower  tier. 

Structure  and  development. — Of  a  somewhat  compact  texture,  like  all 
the  long  bones,  these  have  no  medullary  canal,  and  are  developed  from  only 
one  ossific  centre.  Not  unfrequently,  however,  the  tubercle  is  formed  from 
a  special  centre. 

3.  Bones  of  the  Phalangeal  Region  or  Digit. 

Solipeds  have  only  one  digit,  supported  by  the  principal  metacai-pal  bone, 
and  composed  of  three  pieces  placed  end  to  end,  one  upon  another.  The 
first  comprises  three  bones :  a  principal,  the  first  2)h(ihnx,  and  two  com- 
plementary ones,  the  sesamoids.  The  second  is  formed  by  the  second 
phalanx,  and  the  last,  which  terminates  the  limb,  is  constituted  by  the 
third  phalanx  and  an  accessory  bone  which  has  received  the  name  of  the 
small  sesamoid  (navicular  bone). 

FiusT  (proximal)  or  Metacarpal  Phalanx. — The  first  jihalanx  (or 
pastern  bone),  the  smallest  of  all  the  long  bones,  is  situated  in  an  oblique 
direction  from  above  downwards,  and  behind  to  before,  between  the  principal 
metacarpal  and  the  second  phalanx. 

Body. — Depressed  in  front  and  behind,  this  bone  exhibits :  an  anterior 
face,  round  from  one  side  to  the  other,  and  slightly  roughened  above  and 
below ;  a  posterior  face,  flat,  covered  with  ligamentous  imprints  in  the  form 
of  a  triangle  with  the  base  reversed  ;  two  lateral  borders,  thick,  rounded,  and 
provided  with  some  imprints. 


TEE  ANTERIOR  LIMBS. 


83 


Extremities. — The  superior,  the  largest,  presents:  Above,  an  articular 
surface  adapted  to  the  interior  metacarpal  surface,  and  consequently  composed 
of  two  glenoid  cavities  separated  by  a  groove  running  from  front  to  back ; 
laterally,  and  a  little  posteriorly,  a  well-defined  tubercle  of  insertion.  The 
inferior  extremity  has  a  transversely  elongated  articular  surface  to  cor- 
respond to  the  second  phalanx ;  this  surface  is  formed  by  two  condyles 
separated  by  a  middle  groove,  and  sui'muiinted  laterally  by  a  small 
tuberosity  for  ligamentous  insertions.      The  external  condyle   is   smaller 


Fis;.  48. 


Fis.  49. 


LATERAL  VIEW   OP   THE   DIGITAL 
REGION  •,  OUTSIDE   OF   RIGHT   LIMB, 

1,  Large  metacarpal  bone;  2,  3,  Outer 
and  inner  sesamoids  ;  4,  First,  proximal, 
suffraginis  or  metacarpal  phalanx,  5, 
Its  posterior  surface ;  6,  Tuberosity  for 
ligamentous  insertion  ;  7,  Inner  condyle 
of  ditto ;  8,  Eminences  on  second  pha- 
lanx for  attachment  of  lateral  liga- 
ment; 9,  Smooth  surface  for  passage 
of  deep  flexor  tendon  on  second  pha- 
lanx ;  10,  Imprint  for  the  insertion  of 
the  terminal  branch  of  the  perforatus 
tendon;  11,  Navicular  bone;  12.  Third 
phalanx,  pedal,  or  coffin  bone ;  13,  Its 
basilar  process. 


POSTERIOR   VIEW   OF   FRONT   DIGITAL 
REGION. 

1,  Large  metacarpal  bone ;  2,  3,  Outer 
and  inner  splint  bones ;  4,  5,  Sesamoid 
bones ;  6,  Sufl'raginis  ;  7,  8,  Tuberosi- 
ties for  insertion  of  crucial  ligaments ; 
9,  Triangular  space  for  insertion  of 
short  sesamoid  ligament ;  10,  Anterior 
face  of  suftraginis  ;  11,  12,  Tuberosities 
for  ligamentory  insertion ;  13,  Articu- 
lar depression  separating  condyles  ;  14, 
15,  Second  phalanx  ;  Its,  Scabrous  sur- 
face for  ligamentous  attachment ;  17, 
Smooth  surface  for  gliding  of  deep 
flexor  tendon;  18,  Navicular  bone; 
19,  Pedal  bone;  20,  Basilar  process; 
21,  Plantar  foramen. 


than  the  internal,  and  when  the  bone  is  placed  upon  a  horizontal  piano, 
the  anterior  face  turned  upwards,  it  only  touches  by  three  points — the  two 
tubercles  of  the  upper  extremity  and  the  internal  condyle ;  by  pressing  on 
the  external  condyle,  it  is  easy  to  make  the  bone  rock. 

^  The  first  phalanx  is  a  very  compact  bone,  and  is  developed  from  two 
points,  one  of  which  is  for  the  superior  extremity  alone. 


84  THE  BONES'. 

Sesamoids. — These  are  two  small  short  bones  placed  side  by  side  bchiud 
the  superior  extremity  of  the  first  phalanx,  whose  articular  surface  it 
completes,  as  it  has  not  extent  enough  to  be  exactly  adapted  to  the 
metacarpal  surface.  Each  of  these  bones  represents  a  small,  irregularly- 
shaped  polyhedron,  or  rather,  a  short  trifacial  pyramid.  It  otfers :  an 
anterior  face,  which  is  articular,  and  corresponding  to  the  inferior  extremity 
of  the  principal  metacarijal  bone,moulded,  as  it  were,  on  one  of  the  condyles 
and  one  of  the  sides  of  the  median  ridge ;  a  posterior  face,  covered  with 
cartilage  in  the  fresh  state,  and  forming,  with  that  of  the  opposite  bone, 
a  gliding  concave  surface  for  the  flexor  tendons  of  the  phalanges  ;  a  lateral 
face,  studded  with  ligamentous  imprints ;  a  summit,  directed  upwards ;  and  a 
base,  turned  downwards,  and  serving  for  the  attachment  of  several  ligaments. 
Skcond  (or  Middle)  Phalanx  (  Os  Couon^,  Small  Pastern  Bone). — 
This  is  a  short  bone,  situated  in  the  same  oblique  direction  as  the  first 
jihalanx,  and  between  it  and  the  third.  Its  general  form  is  that  of  a  cube 
flattened  before  and  behind,  and  offering  the  following  features  :  an  anterior 
face,  covered  with  some  slight  imprints ;  a  posterior  face,  provided,  above, 
with  a  transversely  elongated  gliding  surface ;  a  s^iperior  face,  channeled 
by  two  glenoid  cavities,  to  match  the  inferior  articulating  surface  of  the 
first  phalanx ;  an  inferior  face,  formed  on  the  same  plan  as  the  last,  being 
occupied  by  two  unequal  condyles  which  articulate  with  the  third  phalanx 
and  the  navicular  bone  ;  two  lateral  faces  exhibiting  a  very  marked  imprint. 
In  the  interior  of  this  bone  is  found  a  nucleus  of  very  condensed  spongy 
substance,  enveloped  in  a  layer  of  compact  tissue.  It  is  usually  developed 
from  a  single  centre  of  ossification ;  though  in  many  subjects  there  is  a 
complementary  nucleus  for  the  superior  articular  surface  and  the  j)Osterior 
gliding  surface. 

Third  (Distal)  Phalanx,  Os  Pedis  (or  Pedal  Bone). — This  is  a  short 
bone  which  terminates  the  digit,  and  sustains  the  hoof'  that  incloses  it  and 
the  navicular  bone.  AVhen  completed  by  a  special  fihro-cartilaginons  apparatus, 
it  represents  the  segment  of  a  very  short  cone,  obliquely  truncated  behind, 
from  the  summit  to  the  base.  It  offers  for  study:  three  faces,  three  borders, 
and  two  lateral  angles 

Faces. — The  anterior,  convex  from  side  to  side,  and  cribbled  by  porosities 
and  vascular    openings,  shows   on  each  side :    1, 
'^"     ■  The  preplantar  finsure,  a  horizontal  groove  more 

or  less  ramified,  which  commences  behind, 
between  the  retrossal  and  basilar  processes,  ter- 
minating in  front  in  one  of  the  foramina  which 
penetrate  the  bone ;  2,  The  patilobe  eminence,  a 
roughened  jirojecting  surface,  situated  between  the 
preceding  fissure  and  the  inferior  border  of  the 
bone.  The  superior  face  is  occujiied  by  an  articu- 
lar surface  formed  by  two  glenoid  cavities  and  a 
slight  median  ridge  ;  it  comes  in  apposition  with 
PLANTAR  SURFACE  OF  THIRD  ^^^^  iiifei'ior  facc  of  the  second  phalanx.  The 
PHALANX.  inferior  (or  solar)  face,  hollowed  out  like  an  arch, 

1,  Lower  face,  or  sole;  2,  3,  is  divided  into  two  regions  by  the  semilunar  crest, 
Wings,  or  retrossal  pro-  j^  salient  line  which  describes  a  curve  forwards. 
cesses;  4,  Internal  border;  rj^j^^  anterior  region  is  perforated  with  very  fine 
5,  Plantar  foramina.  ...  ,   »  i      ,      ,^    ,  .       n    .i 

porosities,   and  corresponds  to  that   part   oi    tne 

hoof  named  the  sole.     The  posterior  region  shows,  immediately  behind  the 
semilunar  crest,  a  median  imprint,  and  two  lateral  channels  designated  the 


THE  ANTERIOR  LIMBS.  85 

plantar  fissures.  These  originate  at  the  root  of  the  basilar  process,  are 
directed  obliquely  downwards  and  inwards,  and  open  into  the  plantar  fora- 
mina, the  external  orifices  of  two  large  canals  which  enter  the  bone  and  unite 
in  its  interior  to  form  the  semilunar  sinus. 

Borders. — The  superior  describes  a  curve,  ■with  the  convexity  forward, 
and  presents :  1,  In  its  middle,  the  pyramidal  eminence  of  the  os  pedis,  a 
single  triangular  process,  flat  before  and  behind,  roughened  on  its  anterior 
aspect,  and  concurring,  by  its  posterior  surface,  to  form  the  articular  surface 
which  responds  to  that  of  the  second  phalanx ,  2,  Laterally,  two  facets  of 
insertion  which  encroach  on  the  anterior  surface,  and  even  advance, 
posteriorly,  nearly  to  the  preplantar  fissure.  The  inferior  harder  is  thin, 
dentated,  convex,  and  semicircular;  it  is  perforated  by  from  five  to  ten 
large  foramina  which  pass  iato  the  bone.  The  posterior  border  is  slightly 
concave  ;  on  it  is  observed  a  very  narrow,  transversely  elongated,  diarthrodial 
facet,  w'liich  becomes  confounded  with  the  superior  large  articular  surface, 
and  is  adapted  to  a  similar  facet  on  the  navicular  bone. 

Lateral  ancjles. — These  are  two  projections  directed  backwards,  on  whose 
summit  the  three  borders  of  the  bone  unite,  and  which  gives  attachment 
to  the  lateiiil  fibro-cartilages.  A  deep  notch,  the  origin  of  the  preplantar 
fissui'e,  separates  each  into  two  particular  eminences  :  one,  the  superior, 
named  by  M.  Bouley  the  basilar  process  ;  the  other,  the  inferior,  prolonged 
behind,  and  designated  by  Bracy  Clark  the  retrossal  process,  from  retro, 
behind,  and  o»»a.  bone. 

Structure. — The  os  pedis  exhibits  in  its  interior  the  semilunar  sinus,  a 
cylindi'ical,  transversely  elongated,  and  semicircular  cavity  resulting  from 
the  arching  anastomoses  of  the  two  plantar  canals.  From  this  cavity  pass 
off  numerous  channels,  which  anastomose  frequently  with  each  other,  and 
open  externally  by  the  foramina  on  the  anterior  face  of  the  bone,  or  by 
thos^  on  its  inferior  border.  The  os  pedis  has  for  its  base  a  nucleus  of 
spongy  substance,  sui'rounded  by  a  layer  of  compact  tissue.  The  latter  is 
thicker  towards  the  pyramidal  eminence  than  elsewhere,  and  sends  into 
the  interior  numerous  prolongations  which  form  the  walls  of  the  semilunar 
sinus,  as  well  as  the  bony  channels  which  spring  from  it. 

Developjment. — The  third  phalanx,  formed  from  a  single  nucleus  of 
ossification,  undergoes  numerous  changes  in  its  configuration  during  life. 
Thus,  in  the  young  animal  the  lateral  angles  are  thick,  obtxise,  and  but 
little  prolonged  posteriorly  ;  but  as  it  grows  older,  they  increase  in  length 
and  become  salient.  The  development  they  then  assume  is  due  to  the 
progressive  ossification  of  the  lateral  cartilages  implanted  on  their  surface. 
It  often  happens,  in  very  old  horses,  that  this  ossifying  process  is  carried 
to  an  extreme  degree,  and  nearly  the  whole  substance  of  these  complementary 
organs  is  invaded.  From  the  commencement,  its  inevitable  result  is  to 
convert  the  notch  which  separates  the  basilar  from  the  retrossal  process 
into  a  foramen. 

The  complementary  fibro-cartilaginotis  apparatus  of  the  os  pedis. — To 
understand  properly  the  disposition  of  this  portion  of  the  foot,  it  is  necessary 
that  a  previous  knowledge  of  the  ligaments  and  tendons  attached  to  the  os 
pedis  should  have  been  obtained  ;  therefore  a  detailed  description  will  only 
be  given  when  the  Horse's  foot  is  studied  as  a  whole.  It  will  be  sufiicient 
here  to  state  that  this  apparatus  consists  of  tw-o  lateral  pieces,  the  fibro- 
cartilages  of  the  OS  pedis,  united  behind  and  below  by  the  plantar  cushion,  a 
fibrous  and  elastic  mass  on  which  rests  the  navicular  bone  through  the 
medium  of  the  perforans  tendon. 
9 


86 


THE  BONES. 


Fis.  51. 


The  Small  Sesamoid  (or  Navicular)  Bone. — This  short  bone  is  annexed 
to  the  third  phalanx,  behind  which  it  is  situated  ;  it  is  elongated  transversely, 
flattened  above  and  below,  and  narrowed  at  its  extremities.  It  offers:  1,  A 
superior  face,  on  which  are  prolonged  the  glenoid  cavities  and  the  median  ridge 
of  the  articular  surface  of  the  os  pedis  ;  it  responds  to  the  second  phalanx ; 

2,  An  inferior  face,  divided  bj  a 
slight  relief  into  two  undulated 
facets,  and  covered  with  cartilage 
-d  to  form  a  gliding  surface ;  3,  An 
anterior  border,  channeled  length- 
ways by  a  groove  of  insertion,  above 
NAVICULAR  BONE.  which  is  remarked  a  diarthrodial 

a,  Upper,  or  articular  surface;  6,  inferior  border;  facet  that  brings  the  small  SCSa- 
c,  Superior  border;  d,  Inferior,  or  posterior  moid  into  Contact  with  the  poS- 
surface ;  e,  The  median  transverse  ridge ;  /,  terior  border  of  the  third  phalanx ; 
Inferior  margin ;  g,  Superior  margin.  4^   ^  posterior   border  and   two   ex- 

tremities, for  ligamentous  insertion.  This  bone,  as  well  as  the  sesamoids, 
originates  from  a  single  centre  of  ossification.  It  is  formed  of  a  layer  of 
compact  tissue  enveloping  a  nucleus  of  very  condensed  spongy  substance. 


DIFFERENTIAL   CHARACTERS   OF   THE   ANTERIOR  LIMB   IN   OTHER   THAN   SOLIPED 

ANIMALS. 

A.  Shoulder. — In  Carnivora  the  shoulder  is  composed  of  two  bones,  these  creatxires 
being  furnished  with  a  clavicle.  This  bone  in  the  Dog  is  a  little  osseous  shell  imbedded 
among  the  muscles  situated  in  front  of  the  scapulo-humeral  angle.  That  of  the  Cat 
constitutes  a  small  styloid  bone,  which  is  joined  to  tlie  acromion  and  sternum  by  two 
ligamentous  cords. 

In  all  the  domesticated  animals  except  Solipeds,  the  coracoid  process  is  immediately 
applied  against  the  glenoid  cavity.  In  all,  also,  with  the  exception  of  the  Fig,  the 
scapular  spine  gradually  rises  from  above  to  below,  and  terminates  in  a  sharp  salient 
point,  the  acromion. 

The  spine  partitions  the  external  face  of  the  bone  into  two  equal  fossae  in  the  Dog, 
and  in  Ruminants  into  two  fossae,  which,  for  extent,  are  as  one  to  three  to  each  other. 
The  scapular  spine  of  the  Pig  is  much  elevated  towards  the  middle  part,  and  bends  more 
or  less  backwards. 

In  the  Carnivora  the  prolonging  cartilage  is  entirely  absent ;  the  anterior  border  of 
the  scapula  is  very  convex,  as  if  the  bone  had  been  curved  downwards.  In  the  other 
domesticated  mammals  the  scapula  is  somewhat  n^gularly  triangular. 

B.  Arm. — Proportionately,  the  humerus  is  longer,  and  more  inflected  like  an  S,  as 
the  number  of  apparent  digits  is  increased.  Therefore  it  is  that  in  the  Carnivora  the 
characters  of  leni<th  and  inflexion  are  most  marked. 

In  the  Ox,  Slieeii,  Fig,  and  Dog,  the  furrow  of  torsion  is  not  so  deep  as  in  the  Horse, 
and  the  deltoid  imprint  is  less  salient.  In  the  Dog  this  imprint  is  represented  by  a  large 
roughened  surface;  in  the  Fig  by  some  asperities  only.  The  nutrient  foramen  is  on 
the  posterior  face.  It  has  been  stated  that  the  medullary  canal  in  the  Ox  is  traversed  by 
an  osseous  band;  but  the  presence  of  this  is  not  constant. 

The  summit  of  the  trochiter  is  very  elevated,  particularly  in  Ruminants,  and  is  thrown 
back  on  the  bicipilal  groove,  which  is  single;  in  the  Dog  and  Fig,  this  groove  is  carried 
inwards  above  tiie  intern  il  face  of  the  humerus. 

The  external  trochlea  in  the  Ox  and  Fig  is  well  marked.  In  Carnivora,  the  inner  lip 
of  this  trochlea  is  very  high,  and  the  external  lip  incomplete;  a  foramen  establishes 
communication  between  the  olecranian  and  coronoid  fossaj.  In  the  Cat  there  is  found,  on 
the  inner  side  of  the  lower  extremity,  a  particular  foramen  that  forms  a  vascular  arch. 

C.  Fore-arm. — Tiie  fore-arm  is  short  in  the  Ox,  i-fliecp,  and  Fig ;  very  long  in  the 
Carnivora.  The  principal  ditferential  characters  that  it  jiresents  are  connected  with  the 
relative  dimensions  of  the  two  bones  and  their  mode  of  union.  Regarding  these,  and  as 
generally  applicable,  the  following  principles  may  be  laid  down  : — 

1.  The  development  of  the  idna  is  in  direct  relation  to  the  division  of  the  foot. — Mono- 
dactylous  animal,  such  as  the  Horse,  Ass,  and  Mule,  have  in  fact  only  a  rudimentary 


THE  ANTEEIOJi  LIMBS. 


87 


ulna.  In  tlie  pentadactylous  animals,  as  Man,  the  Cat,  etc.,  on 
the  contrary,  this  is  a  veritable  long  bone  which  equals,  or  even 
exceeds,  the  radius  in  volume. 

2.  The  closeness  of  union  betioeen  the  radius  and  ulna  is  in 
increased  proportion  as  the  animal  exclusively  employs  its  interior 
extremity  for  standing  or  ivalhing. — Thus,  in  Solipeds  and  llumi- 
nauts,  and  Pacliyderms  in  general,  the  two  bones  are  consolidated, 
or  at  least  united,  by  an  interosseous  ligament,  and  in  so  firm  a 
manner  that  they  can  only  execute  very  obscure  movements  on 
each  other.  The  anterior  limb  of  these  animids  is  indeed  only 
used  to  support  the  body  on  the  ground.  In  those,  on  the  con- 
trary, which  may  employ  it  to  dig  up  the  soil,  climb  on  trees,  etc., 
or  as  an  organ  of  prehension,  the  radius  and  ulna  are  merely 
joined  at  their  extremities  by  an  articulation,  which  permits  them 
to  move  upon  one  another  with  the  greatest  facility.  Rodents,  the 
majority  of  the  Carnivora,  and  the  quudrumana,  are  so  provided ; 
but  it  is  in  Man  that  the  relative  indt  pendence  of  the  two  bones  is 
carried  to  the  highest  degree.  No  animal  can  so  easily  execute 
the  movements  of  pronation  and  supination  of  the  hand,  which 
are  determined  by  the  play  of  the  two  bones  of  the  fore-arm  on 
each  other. 

To  the  indication  of  these  fundamental  characters  may  be 
added  some  details  on  a  few  particular  and  important  points. 

In  all  the  domesticated  animals  other  than  Solipeds,  the  ulna 
is  developed  from  three  ossifying  centres,  extends  the  whole  length 
of  the  radius,  and  concurs  to  form  the  articular  surface  correspond- 
ing to  the  carpal  bones.  It  is  an  elongated  bone  in  Ruminants, 
and  a  long  bone,  hollowed  by  a  medullary  canal,  in  the  Pig  and 
Carnivora. 

The  inferior  articular  surface  of  the  bone  of  the  fore-arm  in 
Buminants  is  cut  obliquely  from  above  to  below,  and  from  with- 
out to  within.'  In  these  animals  we  find  the  radius  very  flat  from 
before  to  behind,  the  bicipital  tuberosity  scarcely  noticeable,  and 
two  radio-ulnar  arcades  uuitt- d  externally  by  a  deep  fissure.  The 
union  of  the  two  bones  is  more  intimate  than  in  the  Horse,  for  the 
ossification  always  finishes  by  invading  that  portion  of  the  inter- 
osseous ligament  placed  above  the  superior  vascular  arcade. 

In  the  Pig,  the  idna  is  flattened  from  before  to  behind,  and 
spread  out  on  the  posterior  face  of  the  radius,  which  it  almost 
completely  covers.  Its  olecranon  is  very  prominent.  In  the  Dog 
and  Cat,  the  two  bones  of  the  foie-arm  are  nearly  equal  in  volume, 
and  are  slightly  cro.^sed  in  an  X  fashion.  The  superior  extremity 
of  the  ulna  is  thicker  than  its  lower  extremity  ;  it  is  nearly  the 
opposite  of  this  in  the  radius.  Movable  on  one  another,  these 
bones  only  touch  by  their  extremities,  and  to  this  ett'ect  offer :  1, 
Alx)ve,  on  the  ulna,  a  concave  articular  surface,  the  small  sig- 
moid cavity,  and  on  tlie  radius  a  rounded  hinge-like  facet;  2, 
Below,  on  the  radius,  a  concave  surface,  and  on  the  ulna  a  convex 
one. 

D.  Fore-foot,  or  hand. — 1.  Carpal  hones. — The  carpus  of  the 
Pig,  like  that  of  Man,  contains  eight  bones— four  in  each  of  the 
rows.  The  second  bone  of  the  upjier  row  corresponds  with  the  ulna, 
and  to  a  small  extent  with  the  radius.  In  the  bones  of  the  lower 
row,  it  is  observed  that  the  first  corresponds  with  the  two  external 
metacarpals,  the  second  with  the  great  internal  metacarpal,  the  third 
with  the  preceding  and  the  small  internal  metacarpal.  The  fourth, 
or  trapezium,  terminates  inferiorly  by  a  blunt  point,  and  has  no 
relations  with  the  metacarpal  bones,  because  the  thumb  is  entirely 
undeveloped  in  this  animal. 


Ficr.  52. 


m 


J 


1,  Olecranon  ;  2,  Body  of  the  ulna ;  3,  Body  of  the  radius  ;  4,  5,  6, 
First,  second,  and  third  bones  of  the  upper  row  of  the  carpus ;  7,  8, 
First  and  second  bones  of  the  lower  row  ;  9,  Rudimentary  nietacar-  fore-arm  axd  FOOT 
pals;  lOj  Principal  metacarpals;  11,  External  digit;  12,  Internal  OF  the  ox;  FRONT 
di^it.  view. 


88 


TEE  BONES. 


In  the  Cat  there  are  also  eight  bones.  The  second,  or  pyramidalis,  of  the  upper  row 
is  very  developed ;  it  occupies  all  the  external  border  of  tlie  carpus,  and  articulates  with 
tlie  ulna,  the  tirst  bone  of  the  second  row,  and  the  first  metacarpal.  The  supercurpal 
bone,  elonjrated,  prismatic,  and  thickened  at  its  extremities,  oifers  in  front  two  coalescing 
articular  facets,  one  to  correspond  with  the  ulna,  the  other  to  join  the  pyramidulis. 
The  bones  of  the  inferior  row  decrease  in  thickness  from  the  first  to  the  fourtli.  and 
correspond:  the  first,  to  the  first  and  second  metacarpals;  the  second,  to  the  metacarpal 
of  the  third  digit ;  the  third,  to  that  of  the  fourth  digit ;  the 
Fig.  53.  fourth,  to  the  metacarpal  of  the  thumb. 

3,  III  the  Dog  there  are  only  seven  bones,  as  the  scaphoid 

and  semilunar  bones  are  united,  but  the  general  disposition 
is  the  same  as  tliat  in  the  Cat. 

Lastly,  in  the  Ox  and  iSheep  the  carpus  is  only  composed 
of  six  bones :  four  in  the  upper  row,  and  only  two  in  the 
lower,  where  the  os  magnum  and  trapezoides  are  consolidated. 
The  snpercarpal  bone  has  no  groove  for  gliding,  and  the 
pyramidalis  articulates  with  the  radius  and  cubitus.  The 
bones  of  the  lower  row  only  aiticulate  with  the  principal 
metacarpal  bone.  (Professor  Gobaux,  in  1865,  e.xhibited 
specimens  which  go  to  prove  that  of  the  two  bones  of  the 
lower  row  in  the  carpus  of  Euminants,  the  internal  really 
represents  two;  so  that  these  animals  actually  have  seven 
carpal  bones  like  the  Horse.) 

2.  Metacarpal  hones. — The  number  of  metacarpal  bones 
varies  much  in  the  domesticated  animals : — 

In  the  Carnivora  there  are 5 

In  the  Pig  there  are  .......     4 

In  Kuminants  there  are 2 

The  five  metacarpals  of  the  Bog  and  Cat  articulate  with 
each  other,  at  tlieir  superior  extremities,  by  lateral  facets; 
they  offer,  at  their  inferior  extremity,  a  couTlyle  prolonged 
backwards  by  an  articular  surface  resembling  that  of  the 
Horse.  The  middle  two  are  always  longer  than  the  two 
lateral.  The  smallest  belongs  to  the  fifth  digit,  or  thumb, 
and  is  terminated  interiorly  by  a  trochlea. 

The  four  metacarpals  of  the  Pig  articulate  with  each  other, 
as  in  the  Carnivora.  The  second  and  third  are  larger  tiiau  the 
first  and  fourth.     The  fifth  metacarpal  is  not  developed. 

In  Ruminants  the  metacarpal  bones  are  two  in  number : 
a  priiacipal,  which  itself  results  from  the  consolidation  of  the 
...     11   ^  second  and  third  metacarpals,  and  another  altogether  rudi- 

"^  CT     3  mentary. 

The  principal  metacarpal  is  channeled  on  its  anterior  face, 
and  for  its  whole  lent;th,  bv  a  deep  vascular  fis>ure — a  trace 
TORE- ARM   AND  FOOT  OF    of  the  primitive  separation  "of  the  bone  in  two  pieces.     This 
THE     DOG  ;     ANTERIOR    fissuro  presents,  interiorly,  the  anterior  orifice  of  a  canal  that 
'^^G^-  completily  traverses  the  bone.     The   posterior   face   is  also 

1,  First  digit;  2,  Second  marked  by  a  very  slight  longituflinal  groove.  Tlie  superior 
digit ;  3,  Third  digit ;  extremity  exhibits,  externally  and  posteriorly,  a  single  diar- 
4,  Fourth  digit ;  5,  throdial  facet  for  the  articulation  of  the  rudimentary  meta- 
Thumb;  G,  7,  8,  9,  First  carpal.  The  inferior  extremity  is  diviiled  by  a  dei-p  notch 
second,  third,  and  fourth  into  two  articular  surfaces,  which  together  resemble  the  single 
bones  of  the  lower  row  surface  in  the  Horse ;  each  corresponds  to  one  of  the  digits ; 
of  carpal  bones ;  10,11,  the  external  is  always  smaller  than  the  internal.  In  the 
First  and  second  bones  foetus,  the  two  long  bones  that  form  the  great  metacarpal 
of  the  upper  row;  12,  are  simply  laid  together,  and  their  medullary  canals  are  sepa- 
Supercarpal  bone  •,  13,  rated  from  each  other  by  the  double  partition  which  results 
Body  of  the  ulna;  14,  from  this  apposition  ;  after  their  coalescence,  however,  the  par- 
Apex  of  the  olecranon  ;  titions  are  completely  destroyed  by  resorption,  and  in  a  short 
15,  Beak  of  the  olecra-  time  there  is  oidy  a  single  medullary  canal  for  the  entire  bone, 
non;    16,  Body  of  the  The  rudimentary  metacarpal  is  only  a  small  osseous  stylet, 

radius.  articulating,  by  a  diarthrodial  facet,  behind  and  to  the  outside 

of  the  superior  extremity  of  the  principal  metacarpal ;  it  is 
sometimes  absent  in  the  Sheep  and  Goat, 


THJi:  ANTERIOR  LULBS. 


89 


8.  Digital  Region. — In  the  domesticated  animals  the  number  of  complete  digits  is  as 
follows : — 

Carnivora 5 

Pig 4 

Euminants 2 

The  five  digits  of  the  Dog  and  Cat  are  exactly  analogous  to  those  of  Man.  Thus,  the 
external  corresponds  to  the  auricularis,  the  second  to  the  annularis,  the  third  to  the 
ruedius.  the  fourth  to  the  index,  and  the  internal  to  the  thumb. — The  latter,  very  small, 
has  only  two  plialanges  and  does  not  cotne  into  contact  witli  the  ground.  Eath  of  the 
first  fuur  is  composeJ:  1,  Of  a  first  phulanx,  to  wliich  are  annexed  two  sesamoids; 
2,  A  second  fhalanx,  which  yet  represents  a  veritable  long  bone;  3.  A  conical  phalan- 
gette, pointed,  bent  downwards,  and  hollowed  at  its  base  by  a  circular  groove,  in  which 
is  lodged  the  matrix  of  the  claw.  The  small  sesamoid  (,or  navicular  bone)  is  absent,  but 
is  replaced  by  a  prominence  of  the  ungual  phahmx.  The  auricularis  and  index  are 
alike,  and  not  so  long  as  the  annularis  and  mediiis,  which  are  the  same  in  length. 

The  Pig  has  four  complete  digits  articulating  from  the  metacarpals;  the  thumb  is 
absent.  The  index  and  auricularis,  or  fourth  and  fifth  digits,  are  short,  and  do  not 
usually  rest  on  the  gruund. 

Huminaiits  certainly  possess  four  digits,  but  only  two  are  perfect— the  medius  and 
annularis — and  these  articulate  with  the  inferior  e.ttremity  of  the  principal  metacarpal. 
The  two  others— the  index  and  auricularis  -  are  in  a  rudimentary  condition,  and  are 
represented  by  two  small  bones  situated  above  and  J^hind  the  naetacarpo-phalangeal 
articulation. 

In  the  Ox,  Sheep,  and  Goat,  each  of  the  perfect  digits  comprises  three  phalanges  and 
three  sesamoids. 

The  ^r*i^/(«?ana;  fairly  represents  the  moiety  p.     r, 

of  the  phalanx  in  the  Horse.    It  has  no  posterior  °' 

imprints,  but  shows  them  on  its  inner  surface 
for  the  attachment  of  several  ligaments.  This 
internal  face  is  plane,  and  the  external  convex ; 

these  characters  are  repeated  in  the  other  two  W^^^^>^  ^-K  H^ ■.„...-...,„.„„  HiB 

phalanges.     It  is  also  remarked  in  all  the  pha-  ^^^^^^»tP^>-~-^  '^'i       -"■/jip 

langeal  bones,  that  the  external  articular  facet  ^peaa^k^-ist-. .. 

of  the  extremities   is  always  larger   than   the  ^* 

internal.  Of  the  two  sesamoids,  the  external  is 
larger  and  less   elongated  than   the  internal.  ^Ifiiit^llS- 

first  particulate  witii  each  other,  and  with  the  '^wE^#'  ■ 

They  halanx  by  small  diarthrodial  facets. 

The  second  phalayix  is  hollowed  internally 
by  a  small  raedullary  cavity.  y^t'-W/'-  ^ ' 

The  ungual  phalanx,  as  a  whole,  resembles  ^V  :   'ft,    '''.//•,  '■■  ^-'•* 

one  of  the  lateral  moitties  of  the  os  pedis  of  Vv '•'  ■  '  ■ '■.    ')/■/ 

solipeds.     This  phalanx  has  no  complementary  ■■* ''  '    ' '"     '/' 

fibro-cartilage,  basilar  process,  or  retrossal  emi- 
neme,  nor  yet  a  cavity  of  insertion  on  the  sides 

of    the  pyramidal   eminence.      The  semilunar  ^rl* 

crest  is  replaced  by  an  obtuse,  thick,  and  rugged 

relief,  which  occupies  quite  the  posterior  limit  %^ 

of  the  inferior  face  of  the  bone.     Three  large  7 

canals  penetrate  the  third  phalanx,  two  to  the  htiman  scapula  ;  external  aspect. 
base  of  the  pyramidal  eminence,  and  one  towards  ^  Supraspinous  fossa;  2,  Infraspinous 
the  origm  of  the  preplantar  fissure.  They  form,  '  ^^  J  ^  ^  .^^.  ^^^.^  ^  ^ 
m  the  interior  of  the  bone,  a  vast  sinus,  gmng  .eapular  notch  ;  5,  Anterior  or  axillary 
rise  to  several  vascular  canals  which  open  on  the  ^J^^^  g  ^^^^  ^^  the  scapular  and 
snrface.  There  is  only  one  foramen  at  the  base  of  j^^^;^'  ^^^.^^.  ^  ^^^^^-^^  ^^  1,  g 
the  pyramidal  eminence  in  the«man€ri?M»Hnan<s.        ^^^^   ^^   ^^^■  \,.^^^i.^.    9^    Posterior 

border;    10,    Spine;    11.    Triangular 

COSIPABISOV  OF  THE  THORACIC  LisiB  OF  MAN  WITH        smooth  surface.  Over  which  the  tendon 

THAT  OF  THE  DOMESTICATED  ANIMALS.  of  the  trapezius  glides,  with  the  tuber- 

J.  Shoilder.— The  shoulder  of  man  (fig.  54)        culum  spina;  scapulae  between  it   and 
has  fnr  its  base  two  well-developed  bones,  the        10;  12,  Acromion  process;  13,  Nutrient 
scapula  and  clavicle.     The  scapula  is  more  dis-        foramen  ,  14,  Coracoid  process, 
tinctly  triangular  than  that  of  all  the  domesti- 
cated animals ;  its  vertebral  border  is  also  more  extensive.    The  scapular  spine,  very 


90 


THE  BONES. 


elevated  is  followed  by  an  acromion  whose  extremity  reaches  to  above  the  scapulo- 
humeral'artioulation.  The  latter  is  separated  from  the  remainder  of  the  spine  by  a 
constriction  called  the  pedicle  of  the  acromion.  The  coracoid  process  is  voluminous,  and 
resembles  a  semi-flexed  finger.  The  clavicle  extends  from  the  acromion  to  the  sternum ; 
it  is  flattened  above  and  below,  and  flexed  like  an  italic  S.  This  inflexion  of  the 
clavicle  is  more  pronounced  in  the  male  than  the  female.  ,.     ,      • 

B.  AiiM.— The  humerus  of  Man  is  much  longer  than  that  of  animals.  Its  diaphysis 
is  prismatic  and  divisible  into  three  faces;  the  deltoid  imprint  has  the  form  of  a  V  with 
its  point  directed  downwards.    The  voluminous  articular  head  is  turned  inwards ;  the 


Fiff. 


fig.  56. 


HUMAN    ARM-BONES  ;   FRONT   VIEW. 

1,  Shaft  of  ulna ;  2,  Greater  sigmoid 
notch;  3,  Lesser  sigmoid  notch;  4  Ole- 
cranon process  ;  5,  Coronoid  process ;  6, 
Nutrient  foramen ;  7,  Ridges  for  inser- 
tion of  interosseous  membrane;  8,  Capi- 
talum  ulna;;  9,  Styloid  process;  10, 
Shaft  of  radius;  11,  Its  head;  12,  Its 
neck ;  13,  Its  tuberosity ;  14,  Oblique 
line;  15,  Lower  end  of  bone;  16,  Styloid 
process. 


EIGHT  HUMAN   HUMERUS;  ANTERIOR 
SURFACE. 

1,  Shaft;  2,  Head;  3,  Neck;  4,  Greater 
tuberosity ;  5,  Lesser  tuberosity  ;  6,  Bici- 
pital groove;  7,  Interior  bicipital  groove; 
8,  Posterior  bicipital  ridge  ;  9,  Rough  sur- 
face for  insertion  of  deltoid  ;  10,  Nutrient 
foramen;  11,  Eminentia  capitata;  12, 
Trochlea;  13,  External  condyle;  14,  In- 
ternal condyle;  15,  External  condyloid 
ridge;  16,  Internal  condyloid  ridge;  17, 
Fossa  for  the  coronoid  process  of  ulna. 

bicipital  groove  is  single,  and  looks  outwards.    The  inferior  articular  surface  resembles 
that  of  animals,  except  that  the  condyle  is  more  distinct. 

C.  FoRE-ARM.— The  two  bones  of  the  fore-arm,  as  we  have  already  seen,  only  articu- 
late by  their  extremities :  they  are  separated  from  one  another  in  their  middle  part. 
The  superior  extremity  of  the  radius  corresponds  to  the  condyle  of  the  humerus ;  that  of 
the  ulna  articulates  with  the  humeral  trochlea.  The  coronoid  process  belongs  to  the 
ulna.  At  the  lower  extremity  of  the  fore-arm  it  is  remarked  :  1,  That  the  radius  cor- 
responds to  the  greater  portion  of  the  carpus,  while  the  ulna  only  articulates  with  the 
pyramidalis ;  2,  That  the  radio-carpal  articulation  is  protected  outwardly  and  inwardly 
by  two  small  osseous  prolongations,  the  styloid  processes  of  the  ulna  and  radius. 

D.  Hand. — 1.  Carptis.— The  carpus  of  Man  is  composed  of  eight  bones— four  in  each 


THE  POSTEBIOB  LIMBS 


91 


Ficr.  57. 


row.  The  three  first  of  the  upper  row  articulate  with  the  radius;  the  fourth  responds 
to  the  ulna.  In  the  bones  of  the  lower  row,  the  trapezium  responds  to  tlie  metacarpal 
of  the  thumb  and  that  of  the  index  the  trapezoide)<  to  the  latter  only,  the  os  magnum 
and  unciform  to  the  metacarpals  of  the  medius,  annularis,  and  little  finger.  The 
pisiform  bone  and  the  cuneiform  process  of  the  unciform  convert  the  posterior  face  of  the 
carpus  into  a  channel. 

2.  Metacarpus. — The  five  metacarpals  of  Man  are  parallel  to  each  other,  and  articulate 
by  their  superior  extremities  with  the  bones  of  the  car- 
pus ;  by  their  inferior  extremities  with  the  phalanges. 
They  are  all  concave  in  their  middle  portion,  and 
thickened  at  their  ends.  The  metacarpal  of  the  thumb 
is  the  shortest  and  strongest.  The  others  diminish  In 
volume  from  the  fourth  to  the  first. 

3.  Digital  Begion. — Here  we  find  five  digits,  earh 
composed  of  three  bony  columnettes,  with  the  exception 
of  the  thumb,  in  which  only  the  second  and  third  pha- 
langes are  present.  They  decrease  in  length  from  the 
third  to  the  first,  and  the  third  to  the  fifth.  The  first 
and  second  phalanges  are  small  semicylindrical  bones, 
slightly  thickened  at  their  extremities.  The  ungueal 
phalanges  are  constricted  in  their  middle,  and  widened 
like  a  horse-shoe  at  their  inferior  extremity ;  the  palmar 
face  is  roughened,  the  dorsal  face  smooth. 

Article  V. — Posterior  Limbs. 

Each  of  these  is  divided,  as  already  noted, 
into  four  secondary  regions :  the  ^pelvis,  thigh, 
leg,  ani  foot. 

PELVIS. 

The  pelvis  is  a  kind  of  bony  cavity  formed 
by  the  union  of  the  sacrum  with  two  lateral 
pieces,  the  coxsb,  vrhich  are  consolidated  with 
each  other  in  the  inferior  median  line.  The 
description  of  the  sacrum  having  been  already 
given,  it  now  remains  to  speak  of  the  coxa. 


PALMAR   SURFACE   OF   LEFT 
HUMAN    HAND. 

1,  Scaphoid  bone;  2,  Semilunare; 
3,  Cuneiform  ;  4,  Pisiform  ;  5, 
Trapezium  ;  6,  Groove  in  tra- 
pezium for  tendon  of  flexor 
carpi  radialis  ;  7,  Trapezoides ; 
8,  Magnum  ;  9,  Unciform  ;   10, 

10,  The  five  metacarpal  bones; 

11,  11,  First  row  of  phalanges  ; 

12,  12,  Second  row;  13,  13, 
Third  row ,-  14,  First  phalanx 
of  the  thumb;  15,  Second  and 
last  phalanx. 


A.  Coxa. 

The  coxa,  also  designated  os  iliaciim,  os  innO' 
minatinn,  is  a  very  irregularly-shaped  flat  bone, 
double  (with  its  fellow  on  the  ojiposite  side), 
and  directed  obliquely  from  above  to  below  and 

before  to  behind.  It  is  contracted  in  its  middle  part,  which  presents  exter- 
nally an  articular  cavity,  the  cotyloid;  anteriorly,  where  it  rests  on  the 
sacrum,  it  becomes  widened,  as  it  also  does  in  its  posterior  portion,  which 
is  inflected  inwards  to  be  united,  on  the  median  line,  with  the  bone  of 
the  opposite  side. 

It  is  divided,  in  the  foetus,  into  three  distinct  pieces,  joined  by  cartilage 
in  the  centre  of  the  cotyloid  cavity,  which  the  three  concur  in  forming. 
Although  they  soon  become  consolidated  into  a  single  piece,  it  is  customary 
to  describe  them  as  so  many  separate  bones  by  the  names  of  ilium,  pubis,  and 
ischium. 

Ilium. — The  ilium,  a  flat  and  triangular  bone,  curved  on  itself,  directed 
obliquely  from  above  to  below,  before  to  behind,  and  within  outwards,  forms 
the  anterior  portion  of  the  coxa  which  corresponds  with  the  sacrum.  It  is 
the  most  considerable  of  the  three  divisions,  and  has  two  faces,  three  borders, 
and  three  angles. 


92 


THE  BONES. 


Faces, — The  €a;ternal  or  superior  face,  studded  with  some  muscular 
imprints,  is  excavated  on  both  sides,  and  is  named  the  external  iliac  fosssa. 
The  internal  or  inferior  face  offers  for  study :  1,  An  external  portion, 
smooth,  and  crossed  by  some  vascular  grooves;  this  is  the  iliac  surface, 
which  is  replaced  in  Man  by  an  excavation  called  the  internal  iliac  fossa  ; 
2,  An  internal  portion,  roughened  and  uneven,  presents,  posteriorly,  the 
auricular  facet,  an  irregular  diarthrodial  surface,  elongated  from  side  to 
side,  a  little  oblique  in  front  and  inwards,  and  responding  to  an  analogous 
surface  on  the  sacrum. 

Borders, — The  anterior  border,  or  crest  of  the  ilium,  is  slightly  concave, 

Fig.  58. 


THE   COX^;   SEEN   FROM   BELOW. 

1,  Iliac  surface;  2,  Auricular  facet;  3,  Angle  or  crest  of  the  ilium;  4,  Angle 
of  the  hauncli'  5,  Cotyloid  cavit^v;  6,  Its  bottom;  7,  One  of  the  imprints 
for  the  insertion  of  the  anterior  straight  muscle  of  the  thigh  (rectus  femoris); 
8.  llio-pectineal  ridge;  9,  Channel  on  the  external  face  of  the  pubes  ;  10,  Oval 
(or  obturator)  foramen;    11,  Ischial  spine  ;  12,  12,  Ischial  arch. 

and  bears  a  roughened  lip  for  muscular  insertion.  The  external  border  is 
thick,  concave,  and  furrowed  by  vascular  fissures  :  it  presents,  inferiorly,  the 
nutrient  foramen  The  internal  border  is  thin  and  concave,  particularly  in 
its  posterior  part,  which  constitutes  the  great  iscJiinfic  notch. 

Angles — The  external  angle,  or  anterior  and  superior  spinous  process,  is 
thick,  wide,  and  flat,  and  bears  four  tuberosities  :  two  superior  and  two 
inferior.  The  internal  angle,  or  posterior  and  superior  spinous  process, 
represents   a    rugged    tuberosity   curved   backwards    and   upwards.^      The 

('  At  the  external  angle  of  the  ilium,  there  is  sometimes  found  in  the  horse  a  process — 
often  a  very  marked  one — directed  downwards,  and  completely  enveloped  by  the  external 
ilio-femorai  muscle.) 


THE  POSTEBIOR  LIMBS. 


93 


posterior  or  cotyloid  angle  is  prismatic  and  very  voluminous.  It  exhibits : 
1,  Behind,  a  wide  concave  articular  facet,  which  forms  part  of  the  cotyloid 
cavity ;  2,  Above  this  cavity,  the  siipracotyloid  crest,  represented  in 
Man  by  the  ischiatic  spine.  This  is  an  eminence  elongated  from  before  to 
behind,  sharp  on  its  summit,  smooth  inwardly,  roughened  outwardly,  and 
continuous  by  its  anterior  extremity  with  the  internal  border  of  the   bone ; 

3,  Outwardly,  two  deep  imprints  for  the  insertion  of  the  rectus  muscle; 

4,  In  front  and  inwards,  the  ilio--pectineal  eminence,  a  small  elongated  pro- 
minence forming  the  most  salient  point  of  a  kind  of  ridge  (lineailio-pectinea) 
that  insensibly  subsides  above  on  the  inner  face  of  the  ilium,  and  is  continued 
below  by  the  anterior  border  of  the  pubis. 

Of  the  three  angles  of  the  ilium,  the  first  is  also  termed  the  angle  of  the 
haunch,  and  the  second  the  angle  of  the  croup. 

Pdbis. — Situated  between  the  ilium  and  ischium,  elongated  from  side  to 

Fi5.  59. 


PELVIS;   FRONT   VIEW. 

1,  Crest  and  anterior  spinous  process  of  the  ilium;  2,  Angle  of  the  croup,  with  the 
auricular  facets  proceeding  from  it  ;  3,  Shaft  of  the  ilium,  with  the  ilio-pectineal 
crest ;  4,  Cotj^loid  cavity  ;  5,  Symphysis  pubis ;   6,  Ischiatic  tuberosity. 

side,  flattened  above  and  below,  and  irregularly  triangular,  the  pubis,  the 
smallest  of  the  three  divisions,  is  divided  for  convenience  of  description  into 
tico  faces,  three  borders,  and  three  angles. 

Faces. — The  superior,  smooth  and  concave,  concurs  in  forming  the  floor 
of  the  pelvis.  It  shows  one  or  two  nutrient  foramina.  The  inferior  is 
roughened,  and  marked  throughout  its  length  by  a  wide  channel  which 
reaches  the  bottom  of  the  cotyloid  cavity.  This  fissure  lodges  the  pubio- 
femoral  ligament  and  a  very  large  vein. 

Borders. — The  anterior  is  constituted  by  a  thin  rugged  lip,  which  is 
curved  upwards.  The  posterior,  thick  and  concave,  circumscribes  anteriorly 
a  wide  opening,  the  oval,  snhpuhic,  or  obturator  foramen  ;  it  is  channeled  near 
the  cotyloid  angle  by  a  fissure  which  runs  obliquely  inwards  and  down- 
wards. The  internal  is  united  with  that  of  the  opposite  pubis  to  form  the 
pubic  portion  of  the  pelvic  symphysis. 


94  THE  BONES. 

Angles. — The  external,  also  named  tlie  cotyloid  angle,  is  the  thickest  of  the 
three.  To  it  chiefly  belongs  the  rugged  depressed  surface  that  constitutes 
the  bottom  of  the  cotyloid  cavity.  The  internal  unites  with  the  analogous 
anc'le  of  the  opposite  pubis.  The  posterior  is  consolidated  at  an  early  period 
with  the  antero-internal  angle  of  the  ischium,  to  inclose,  inwardly,  the  oval 
foramen. 

Ischium.— This  is  the  mean,  in  volume,  of  the  three  pieces  of  the  coxa. 
Situated  behind  the  pubis  and  iUum,  it  is  flattened  above  and  below,  and  of 
a  quadrilateral  form.  It  ofiers  for  study:  two  faces,  four  borders,  and  four 
angles. 

Faces.— The  superior  is  smooth  and  nearly  plane,  and  forms  part  of  the 
floor  of  the  pelvic  cavity.  It  has  a  small  nutritious  foramen  directed  out- 
wards.    The  inferior  presents  some  rugosities   clustered  particulaidy  about 

the  symphysis. 

Fig.  60. 


6' 
PELVIS;  LATERAL  VIEW. 

1,  Crest  of  the  ilium  ;  2,  Angle  of  the  croup ;  3,  Shaft  of  the  ilium  ;  4,  Cotyloid 
cavity,  or  acetabulum  ;  6,  Ischial  spine. 

Borders. — The  anterior,  thick  and  concave,  circumscribes  the  oval  foramen 
posteriorly.  The  poderior,  straight  and  directed  obliquely  forwards  and 
inwards,  forms,  with  the  analogous  border  of  the  opposite  bone,  a  large 
notch  named  the  ischiatic  arch.  It  exhibits,  throughout  its  extent,  a  I'ugged 
depressed  lip  (the  spine),  arising  from  the  side  of  the  inferior  face.  The  ex- 
ternal, thick  and  concave,  constitutes  the  lesser  ischiatic  notch.  The  internal 
is  joined  to  the  ischium  of  the  other  side  to  constitute  a  portion  of  the  pelvic 
symphysis. 

Angles. — The  antero-erternal  or  cotyloidean  is  the  most  voluminous  of  the 
four,  and  affords  for  study  :  1,  An  excavated  diarthrodial  facet,  making  part 
of  the  cotyloid  cavity  ;  2,  The  posterior  extremity  of  the  super-cotyloidean 
crest,  limited  by  a  small  transverse  fissure  which  separates  it  from  the 
external  border  of  the  bono.  The  antero-internal  angle  is  consolidated  with 
the  posterior  angle  of  the  pubis.  The  postero-cvternal  angle  forms  the 
ischiatic  tuherositji.  Tliis  is  a  large  prismatic  process  which  looks  upwards, 
and  is  prolonged  by  a  salient  ridge,  elongated  from  before  to  behind,  with 
its  sharp  border  turned  outwards  and  downwards.    The  postero-internal  angle 


THE  POSTERIOR  LIMBS.  96 

forms,  "with  tliat  of  the  other  ischium,  the  summit  of  the  triangular  space 
which  coustitutes  the  ischiatic  arch,  or  pubic  arch  of  some  species. 

The  Coxa  in  General. — The  bone  whose  three  constituent  parts  we  have 
just  been  studying,  presents  for  consideration,  as  a  whole,  a  middle  portion 
and  two  extremities.  The  middle,  very  much  contracted,  offers,  outwards 
and  downwards,  the  cotyloid  cavity  (or  acetabulum),  which  has  not  yet  been 
described,  because  its  study  does  not  properly  pertain  to  either  of  the  three 
regions  of  the  coxa.  This  cavity  is  intended  to  receive  the  articulating  head 
of  the  femur,  and  represents  the  segment  of  a  hollow  sphere  ;  it  is  circum- 
scribed by  a  very  salient  rim  which  is  thin  at  its  free  margin  and  widely 
notched  on  the  inner  side.  The  deeper  portion  is  occupied  by  the  rough- 
ened  and  depressed  surface  already  designated  as  the  bottom  of  the  cotyloid 
cavity  {fundus  acetabuli),  and  which  communicates  by  the  internal  notch  of 
the  rim  with  the  inferior  groove  of  the  pubis.  The  anterior  extremity,, 
flattened  on  both  sides,  and  formed  by  the  ilium,  rests,  as  has  been  shown, 
on  the  sacrum.  The  posterior  extremity,  flattened  in  an  inverse  sense  to  the 
preceding,  is  constituted  by  the  pubis  and  the  ischium,  and  traversed,  from 
above  to  below,  by  the  sub-pubic  (or  obturator)  foramen,  the  large  oval 
aperture  which  separates  these  two  bones  from  one  another,  and  perforates 
the  floor  of  the  pelvis ;  this  opening  is  closed  in  the  fresh  state  by  muscles. 

The  two  coxae,  by  uniting  in  their  posterior  part,  form  the  articulation 
to  which  has  been  given  the  name  of  iscliio-pubic  or  pelvic  synqihysis ;  thus 
united,  the  two  bones  represent  something  like  a  V  with  the  o2)ening  in 
front ;  a  circumstance  which  makes  the  lateral  diameter  of  the  pelvis  greater 
in  front  than  behind. 

Structure  axd  Development  of  the  Coxa. — To  the  three  centres  of 
ossification  which  constitute  the  coxa,  are  added  two  complementary 
centres  :  one  for  the  anterior  spinous  process  and  sjiine  of  the  iliimi,  another 
for  the  ischiatic  tuberosity. 

In  youth,  the  different  parts  of  the  coxa  are  very  thick,  and  the  spongy 
tissue  is  abundant,  while  the  compact  is  rare.  The  pubis  is  always  convex 
on  its  two  faces,  and  the  middle  part  of  the  coxa — that  adjoining  the  cotyloid 
cavity — is  of  considerable  thickness,  a  feature  which  much  diminishes  the 
extent  of  the  pelvic  reservoir.  As  the  animal  advances  in  age,  however, 
the  layers  of  compact  tissue  increase  in  thickness,  approaching  each 
other  as  the  spongy  substance  is  lessened.  The  pubis  becomes  thinnest,  and 
at  an  advanced  period  of  life  is  sometimes  even  translucid. 

The  compact  tissue  is  always  abundant  in  the  neighboui'hood  of  the 
cotyloid  cavity,  as  this  is  the  centre  on  which  converge  all  the  impulsive 
efforts  communicated  to  the  trunk  by  the  posterior  limbs.  It  is  also  in  this 
cavity  that  ossification  commences. 

B.  The  Pelvis  in  General. 

1.  Exteenal  and  Internal  Conformation  op  the  Pelvis. — The  pelvis  is  a 
kind  of  rear  cavity  in  the  form  of  a  cone,  which  prolongs  the  abdominal  cavity. 

It  occupies  the  posterior  part  of  the  trunk,  and  -ndth  regard  to  its 
conformation,  presents  for  study  an  external  and  an  internal  surface. 

External  surface. — This  may  be  resolved  into  four  regions  or  faces. 

The  superior  rerjion  is  slightly  oblique  from  above  to  below,  and  before 
to  behind ;  its  degree  of  obliquity  varies.  It  is  contracted  from  before  to 
behind,  and  shows:  1,  On  the  median  line,  the  spinous  processes  of  the 
sacral  and  the  first  coccygeal  vertebras  ;  2.  On  each  side  the  sacral  grooves, 
at  the  bottom  of  which  open  the  supersacraJ  canals. 


96  THE  BONES. 

The  inferior  region  is  nearly  horizontal.  Formed  by  the  pubes  and  ischia, 
it  presents  from  before  to  behind :  1,  In  the  middle,  the  ischio-pubic 
symphysis;  2,  On  each  side  the  subpubic  groove,  the  oval  foramina,  and 
the  inferior  face  of  the  ischia  ;  3,  Quite  externally,  the  cotyloid  cavities,  by 
which  the  pelvis  rests  on  the  posterior  limbs. 

The  lateral  regions  are  oblique  from  above  to  below  and  within  to 
without,  and  wider  in  front  than  behind.  They  exhibit :  1,  The  spine  of 
the  ilium  and  the  two  anterior  spinous  processes ;  2,  The  external  iliao 
fossa ;  3,  The  ischiatic  arch ;  4,  The  sujiercutyloid  crest  or  ischiatic  spine, 
which  presents  outwardly  the  surface  of  insertion  for  the  internal  or  deep 
gluteus  muscles;  5,  The  lesser  ischiatic  notch  ;  6,  The  ischiatic  tuberosity. 

Infernal  surface. — The  internal  surface  of  the  Horse's  pelvis  cannot  be 
divided  into  two  portions  as  in  Man,  because  the  inner  aspect  of  the  iliac  bones 
is  not  hollowed  out  to  form  an  anterior  cavity. 

The  pelvis  of  Solipeds  is,  therefore,  a  simple  conoid  cavity,  in  which  are  dis- 
tinguished four  regions  or  faces,  and  two  apertures  called  the  inlet,  and  outlet. 

The  anterior  opening  or  inlet  is  nearly  circular,  especially  in  the  Mare, 
and  a  little  oblique  downwards  and  biackwards.  It  is  limited  above  by  the 
inferior  face  of  the  base  of  the  sacrum ;  inferiorly,  by  the  anterior  border  of 
the  pubis  :  and  on  the  sides  by  a  portion  of  the  inner  face  of  the  iliac  bones, 
and  also  the  internal  aspect  of  the  pectineal  crests. 

The  inlet  presents  four  diameters :  a  vertical,  horizontal,  and  two 
oblique.  The  first  extends  from  the  inferior  face  of  the  sacrum  to  the 
anterior  border  of  the  pubic  symphysis ;  its  mean  length  is  81-  inches. 
The  second  is  measured  from  one  pectineal  crest  or  eminence  to  another ; 
the  mean  of  this  is  Sy^^-  inches.  The  two  last  diameters  are  estimated  from 
the  inferior  face  of  the  sacro-iliac  articulation  of  one  side  to  the  ilio-pectineal 
eminence  of  the  other ;  this  is  on  an  average  8/^  inches.  These  measurements 
irrefutably  demonstrate  that  the  inlet  is  not  elliptical  in  the  vertical  direction. 

The  posterior  aperture  or  outlet,  situated  at  the  posterior  end  of  the  pelvic 
cavity,  gives  exit  to  the  rectum  and  genital  organs.  As  the  pelvis  of  the 
horse  is  horizontal,  the  outlet  should  bo  considered  as  limited^  we  think,  by 
the  inferior  face  of  the  summit  of  the  sacrum,  the  superior  face  of  the  ischia, 
the  supercotyloid  crest  or  ischiatic  spine,  and  the  internal  face  of  the 
sacro-ischiatic  ligaments.  At  the  outlet  only  two  diameters  are  recognised  : 
a  vertical  and  a  horizontal.  The  vertical  measures  on  an  average  6/^  inches  ; 
it  exteuds  from  the  inferior  face  of  the  sacrum  to  the  superior  face  of  the 
ischial  symphysis.  The  horizontal  diameter,  comprised  between  the  two 
supercotyloid  crests,  is  7/^  inches. 

The  superior  region  of  the  pelvic  cavity  is  a  little  concave  from  before 
to  behind ;  it  has  for  base  the  sacrum,  which  pi-esents  on  each  side  of  the 
median  line  the  subsacral  foramina.  This  part  is  also  called  the  sacral 
plane  or  roof  of  tlie  pelvis. 

The  inferior  region,  or  ischio-pubic  plane,  is  formed  by  the  pubis  and 
the  ischia.  It  is  concave  from  side  to  side ;  its  anterior  border  is  nearly 
straight,  and  its  posterior  border  is  scooped  out  by  a  wide  notch  to  form  the 
arch  of  the  ischium. 

It  has  been  remarked  by  M.  Gobaux,  that  the  portion  of  this  plane  corre- 
sponding to  the  pubis  presents  numerous  varieties.  The  superior  face  of  the 
pubis  may  be  convex  in  its  anterior  moiety  and  concave  in  its  posterior ;  or 
it  may  be  concave  before  and  convex  behind,  the  concavity  being  separated 
from  the  convexity  by  a  transverse  ridge.  This  ridge  is  sometimes  represented 
by  a  series  of  small  conical  eminences ,    at  other  times  this  ui^jior  face  is 


THE  POSTERIOR  LIMBS, 


97 


disposed  as  a  smooth  inclined  plane,  directed  backwards  and  upwards,  and 
a  kind  of  rim  siirmotmts  the  anterior  contour  of  the  oval  foramen. 

With  regard  to  the  lateral  regions,  they  are  formed  by  a  small  portion 
of  the  inner  face  of  the  ilia,  and  in  great  part  by  the  sacro- sciatic  ligaments. 

2.  Differences  in  the  Pelvis  of  the  Sexes. — The  pelvis  of  the  Mare 
exceeds  that  of  the  Horse  in  all  its  dimensions,  but  the  difference  is  most 
marked  in  the  transverse  diameters. 

The  anterior  inlet  forms  a  vast  circumference  when  compared  with  that  of 
the  male  ;  the  pectineal  crests  are  widely  apart,  and  the  distance  separating  the 
anterior  border  of  thepubis  from  the  lower  face  of  the  sacrum  is  considerable. 

If  the  pelvis  be  viewed  in  its  superior  plane,  it  is  found  that  in  the 
Mare  the  ischiatic  notches  are  very  deep ;  that  the  internal  border  of  the 
ilium  forms  a  regularly  curved  and  very  concave  line  ;  and  that  the  supracoty- 
loid  crests,  or  ischiatic  spines,  are  widely  separated  from  each  other.  It  is 
also  noticed  tliat  the  floor  of  the  pelvis  is  wide,  and  that  the  bones  com- 
posing it  tend  towards  the  same  horizontal  jjlane. 

In  the  male,  the  ischiatic  border  is  only  represented  by  a  very  curved 
line ;  this  line  is  composed  of  two  almost  straight  portions,  which  join  at 
an  obtuse  angle  at  the  origin  of  the  neck  of  the  ilium  ;  the  supracotyloid 
crests  are  relatively  near  each  other,  and  bent  towards  the  longitudinal  axis  ; 
while  the  two  moieties  of  the  pelvic  floor  are  directed  very  obliquely  down- 
wards and  inwards. 

In  the  Mare,  the  ischial  arch  is  larger  than  in  the  male,  and  forms  a 
regular  curve  uniting  the  two  tuberosities  of  the  same  name.  In  the  Horse, 
the  two  ischiatic  tuberosities  are  but  little  apart  from  each  other,  and  the 
ischial  arch  forms  a  somewhat  aciite  angle  whose  borders  are  nearly  straight. 

Lastly,  when  the  pelvis  i#  examined  in  its  inferior  plane,  in  addition  to 
the  features  already  indicated  in  the  ischiatic  arch,  it  is  found  that  in  the 
Mare  the  obturator  foramina  are  large  and  nearly  circular,  while  in  the 
Horse  they  are  ellij^tical ;  the  cotyloid  cavities  are  also  fui'ther  removed  from 
the  ischio-pubic  symphysis  in  the  female  than  the  male. 

The  sacrum  of  the  Mare  has  apjieared  to  us,  in  some  individuals,  to  be  a 
little  more  arched  from  before  to  behind  than  that  of  the  Horse ;  but  this 
character  is  not  constant. 

The  following  figures  relating  to  the  capacity  of  the  pelvis  in  the  Mare 
and  Horse  confirm  what  has  just  been  enunciated. 


MARE. 
Horizontal  Diameters. 


Between  the  Pectineal 
Crests. 


Between  the  Supercoty- 
loid  Crests. 


HORSE. 
Horizontal  Diameters. 


Between  the  Pectineal      Between  the  Supercoty- 
Crests.  loid  Crests. 


Inches. 
9i 


Inches. 
7i 


Inches. 
8i^ 


Inches. 


MARE. 
Vertical  Diameters. 


HORSE. 
Vertical  Diameters. 


Between  the  Sacrum  and  Between  the  Sacrum  and  Between  the  Sacrum  and 
Pubis.  Ischium.  I  Pubis. 


Between  the  Sdcrum  and 
Ischium. 


Inches. 


Inches. 

"TTi 


Inches. 
8 


Inches. 
6^ 


98  THE  BONES. 

To  recapitulate,  there  is  observed  in  the  pelvis  of  the  Mare: 

1.  A  great  increase  in  the  transverse  diameters; 

2.  A  deep  and  regularly  concave  ischiatic  notch; 

3.  A  wide  and  concave  ischial  arch  ; 

4.  Circular  obturator  foramina ; 

5.  The  cotyloid  cavities  distant  from  the  pubic  symphysis. 

THIGH. 

This  has  for  its  base  one  bone,  the  femur. 

Femur. 

The  femur  is  a  long,  pair  bone,  situated  in  an  oblique  direction  down- 
wards and  forwards,  between  the  coxa  and  the  principal  bone  of  the  leg ;  it 
is  divided  into  a  body  and  two  extremities. 

Body. — It  is  irregularly  cylindrical,  and  presents  for  study /o?<r /aces. 
The  external,  internal,  and  anterior,  confounded  with  one  anotlier,  are 
regularly  rounded  and  almost  smooth,  showing  only  some  slight  imjjrints 
and  vascular  grooves.  The  posterior,  nearly  plane,  and  wider  above  than 
below,  oflfers :  1,  Outwardly  and  towards  the  superior  third,  an  uneven 
circular  surface ;  2,  On  the  same  level,  and  inwardly,  a  slight  crest,  oblique 
downwards  and  outwards ;  3,  In  the  middle,  a  very  extensive  roughened 
surface,  having  the  form  of  an  obliquely  angular  parallelogram,  for  the 
attachment  of  the  great  adductor  muscle  of  the  thigh ;  4,  Below  this 
surface,  a  large  vascular  groove  running  obliquely  outwards  and  downwards. 

On  the  limit  of  the  posterior  and  external  faces  are  found,  towards  the 
upper  third,  a  large  rugged,  flattened  eminence,  curved  in  front,  and  tenned 
the  suhtroclianterian  crest,^  because  of  its  position  under  the  trochanter ;  below,  a 
deep  fossa,  named  the  subcondyloid,  garnished  at  its  bottom  with  asperities 
and  bordered  in  front  by  an  uneven  lip.  On  the  limit  of  the  posterior  and 
internal  face,  there  is  observed  from  above  to  below  :  1,  The  small  troclianter, 
a  large  scabrous  tuberosity,  elongated  in  conformity  with  the  bone,  and 
situated  near  its  upper  fourth ;  2,  A  marked  longitudinal  imprint  for 
the  attachment  of  the  pectineus  ;  behind,  it  is  confounded  with  the  surface 
for  the  insertion  of  the  great  adductor  muscle  of  the  thigh,  and  presents,  in 
front,  the  nutrient  foramen  of  the  bone;  3,  Tlie  origin  of  the  great 
posterior  fissure  ;  4,  Quite  below,  a  collection  of  large  tubercles  which  form 
the  supracondyloid  crest. 

Extremities. — The  superior  extremity  is  sensibly  flattened  before  and 
behind,  and  shows :  1,  Inwardly,  an  articular  head  which  is  received  into  the 
cavity  of  the  acetabulum.  This  head  is  separated  from  the  other  portion  of 
the  body  by  a  neck,  which  is,  however,  not  well  jnarked  in  the  Horse,  and 
forms  two-thirds  of  a  sphere,  excavated  in  its  internal  part  by  a  very  deep 
cavity  for  ligamentous  insertion  ,  2,  Outwardly,  a  very  large  eminence,  the 
trochanter,  or  great  (external)  trochanter,  in  which  is  recognised,  as  in  the 
trochlea  of  the  humerus :  a  summit,  much  more  elevated  than  the  articular 
head  and  slightly  bent  inwards;  a  co7ire.Ti7?/,  incrusted  witli  cartilage  and 
anterior  to  the  summit,  from  which  it  is  separated  by  a  narrow  and  deep 
notch ;  a  crest  situated  under  the  convexity,  and  formed  by  a  tuberculous 
surface  on  which  one  of  the  tendons  of  the  middle  gluteus  muscle  becomes 

'  This  is  the  third  trochanter  of  Cuvier,  and  takes  the  place  of  the  external  and 
superior  branch  of  the  linea  ospera  of  Man.  (It  is  the  external  8m,uU  tivchaiiter  of 
Percivall  and  the  middle  trothanter  of  Leyh. j 


THE  POSTERIOR  LIMBS. 


99 


inserted,  after  gliding  over  the  convexity;  3,  Posteriorly,  the /ossa  of  the 
trochanter,  or  digital  fossa,  a  deep  cavity  studded  with  imprints  and 
circumscribed,  outwardly,  by  a  salient  lip  which  descends  vertically  from  the 
summit  of  the  trochauter  to  the  posterior  face  of  the  bone,  where  it 
gradually  subsides. 

The  inferior  extremity  is  flattened  on  both  sides ;  consequently,  its  larger 
axis  crosses  at  a  right  augle  that  of  the  upper  extremity.     It  is  distinguished 


Fig.  61, 


Fis.  62, 


LEFT   FEMUR  ;   ANTERIOR   VIEW. 

1,  Head  ;  2,  2,  Trochanter  major,  with  its 
crest ;  3,  Trochanter  minor  externus,  sub- 
trochanterian  crest,  or  third  trochanter; 
4,  Lesser,  or  internal  trochanter;  5,  Notch 
for  insertion  of  ligamentum  teres  ■,  7,  8, 
Tuberosities  for  tendinous  and  ligamentous 
insertion  j  9,  Trochlea. 


LEFT  FEMUR;  POSTERIOR  VIEW. 
1,  Head ;  2,  Great  trochanter ;  3,  Third,  or 
trochanter  minor  externus;  4,  Lesser,  or 
internal  trochanter :  5,  Fossa  for  insertion 
of  ligamentum  teres;  6,  Trochanterian 
fossa ;  7,  8,  Tuberosities ;  9,  Fossa  for  the 
insertion  of  the  external  meniscus;  10, 
Supracondyloid  fossa;  11,  Condyles. 


"by  the  presence  of  two  condyles  and  a  trochlea.  The  tvco  condyles,  placed  one 
beside,  the  other  behind,  correspond  to  the  superior  extremity  of  the  tibia. 
They  are  separated  by  a  deep  depression  designated  the  intercoiuhjloid  fossa, 
which  lodges  the  spine  of  the  tibia  and  the  interosseous  ligaments  of  the 
femoro-tibial  articulation.  The  external  condyle  bears  outwardly  two  fossfe : 
one  superior,  for  ligamentous  insertion;  the  other,  inferior,  fur  muscular 


100 


TEE  BONES. 


Fis.  63. 


attachment.  The  internal  condyle  presents,  posteriorly  and  inwardly,  near 
the  posterior  extremity  of  the  intercondyloid  notch,  a  roughened  deju-ession 
for  the  insertion  of  the  fibro-cartilaginous  meniscus  interposed  between  the 
external  condyle  and  the  corresponding  articular  plane  of  the  tibia.  It  is 
surmounted  outwardly,  i.e.,  on  the  side  opposite  to  the  intercondyloid 
notch,  by  a  large  tubercle  of  insertion.  The  trochlea,  a  wide  pulley  on 
which  the  patella  glides,  is  situated  in  front  of  the  condyles.  It  is  slightly 
oblique  downwards  and  inwards,  and  appears  to  continue  in  front  the  inter- 
condyloid notch.  Of  the  two  lips  which  border  its  cavity  laterally,  the 
internal  is  the  thickest  and  the  most  prominent. 
Between  the  external  and  the  corresponding  con- 
dyle is  seen  a  digital  fossa  for  muscular  insertion. 
Structure  and  development. — The  femur,  very 
spongy  at  its  extremities,  is  developed  from  four 
principal  centres  of  ossification  :  one  for  the  body, 
another  for  the  articular  head,  the  third  for  the 
trochanter,  and  the  last  for  the  inferior  extremity 
alone. 

LEG, 

This  has  for  its  base  three  bones :  the  tibia, 
peroneus  (or  fibula),  and  the  rotula  (or  patella). 


SECTION    OF   LEFT   FEMUR, 
SHOWING   ITS   STRUCTURE. 


1.  Tibia. 

The  tibia  is  a  long,  prismatic  bone,  thicker  at 
the  superior  than  the  opposite  extremity,  and 
situated  between  the  femur  and  the  astragalus, 
in  an  oblique  direction  downwards  and  backwards, 
constituting  the  principal  portion  of  the  leg. 

Body. — This  offers  for  study  three  faces  and 
three  borders.  The  faces  are  wider  above  than 
below.  The  external  is  almost  smooth,  and  is 
concave  in  its  superior  part  and  convex  below, 
where  it  deviates  to  become  the  anterior.  The 
internal,  slightly  convex  on  both  sides,  presents,  superiorly,  deep  imprints 
for  the  attachment  of  the  adductor  muscles  of  the  thigh  and  the  semi- 
tendinosus.  The  posterior,  nearly  plane,  is  divided  into  two  triangular 
surfaces  :  one,  superior,  slightly  roughened,  serves  for  the  attacliment  of  the 
popliteus  muscle  ,  the  other,  inferior,  much  more  extensive,  is  furrowed  into 
numerous  longitudinal  crests  which  give  attachment  to  the  perforans 
muscle.  On  the  limit  of  these  two  s^rfaces  is  remarked  the  nutrient  foramen 
of  the  bone.  The  borders  are  distinguished  as  anterior,  external,  and  internal. 
The  first  is  rounded,  and  not  very  salient  in  its  inferior  two-thirds ;  it  forms 
in  its  superior  third,  a  curved  crest,  with  the  concavity  external,  whicli  joins 
the  anterior  and  superior  tuberosity  of  the  bone ;  this  has  received  the  name 
of  the  tibial  crest.  The  external  border  is  very  thick  and  concave  above, 
where  it  constitutes,  in  common  with  the  fibula,  the  tibial  arch.  The 
internal  is  also  very  thick,  straight,  and  provided  superiorly  with  some 
salient  tubercles  to  which  the  popliteus  is  attached. 

Extremities.  — 'ilae  superior  extremity,  the  most  voluminous,  is  formed  by 
three  tuberosities,  an  anterior  and  two  lateral,  which  are  external  and 
internal.  The  first,  the  smallest,  is  a  rugged  process  continuous  with 
the  tibial  crest,  and  separated  from  the  external  tuberosity  by  a  wide  and 


THE  POSTERIOR  LIMBS. 


101 


Ficr.  64. 


deep  groove  in  which  passes  a  tendinous  cord ;  it  is  excavated,  in  front,  by  a 
vertically  elongated  fossa  which  lodges  the  middle  ligament  of  the  patella. 
The  external  tuberosifi/,  medium  in  size  and  the  most  detached,  has  outwardly 
an  articular  facet  for  the  head  of  the  fibula.  The 
internal  tuberosity,  the  largest  and  least  detached, 
presents  :  on  the  sides,  ligamentous  imprints  ;  behind, 
a  small  tubercle  which  gives  attachment  to  the  pos- 
terior crucial  ligament  of  the  femoro-tibial  articu- 
lation. The  superior  face  of  the  two  lateral  tube- 
rosities is  occui^ied  by  two  large  irregular  and 
undulated  articular  siu-faces,  which  respond  to  the 
condyles  of  the  femur  through  the  medium  of  the 
two  meniscus- shaped  fibre -cartilages  interposed  be- 
tween the  two  bones.  Of  these  two  surfaces  the 
external  is  always  the  widest,  because  it  serves,  by 
its  posterior  part,  for  the  gliding  movements  of  the 
popliteal  tendon.  They  are  separated  from  each 
other  by  the  tibial  spine,  a  conical  articular  eminence 
divided  into  two  lateral  parts  by  a  groove  of  inser- 
tion excavated  at  its  base,  and  in  front  by  two  lateral 
facets  for  the  insertion,  anteriorly,  of  the  two  inter- 
articular  cartilages ;  it  is  bordered  beliind  by  another 
fossa  which  receives  the  posterior  insertion  of  the 
internal  meniscus. 

The  inferior  extremity,  flattened  behind  and  before, 
exhibits  an  articular  surface  moulded  on  the  pulley 
of  the  astragalus,  and  two  lateral  tuberosities.  The 
articular  surface  is  formed  by  two  deep  cavities  oblique 
from  behind  to  before  and  within  outwards,  and 
separated  by  a  median  tenon  which  terminates  pos- 
teriorly by  a  very  prominent  projection  on  which  the 
bone  rests  when  it  is  made  to  stand  vertically  on 
a  horizontal  plane.  1"he  external  tuherosity^  projects 
but  little,  and  is  traversed  in  its  middle  by  a  vertical 
fissure.  The  internal  tuberosity^^  better  defined,  is 
margined  posteriorly  by  an  oblique  channel. 

Structure  and  development.  — The  tibia  is  very 
compact  in  its  inferior  portion,  and  is  developed  from 
four  chief  centres  of  ossification.  The  body  is  formed 
by  one  and  the  superior  extremity  by  two,  the  anterior 
tuberosity  taking  one  of  these  ;  the  last  develops  the 
whole  of  the  inferior  extremity.  It  is  rare  to  see 
the  external  tuberosity  of  this  extremity  formed  from 
a  separate  nucleus. 


2.  Fibula  (or  Peroneus). 

A  small,  undeveloped  bone,  elongated  and  sty- 
loid in  shape,  situated  outside  the  tibia,  and  extend- 
ing from  the  superior  extremity  of  that  bone  to  the 
middle  or  lower  third  of  its  body. 

^  The  middle  portion  of  the  fibula  is  thin  and  cylin- 
drical, and  forms  above,  in  common  with  the  external  border  of  the  larger 
1  The  external  malleolus  of  Mau.  =  q^he  internal  vialleolus. 

10 


POSTERIOR   VIEW   OF 
RIGHT   TIBIA. 

1,  Tibial  spine ;  2,  Fossa 
for  the  insertion  of  the 
internal  meniscus ;  3, 
External  tuberosity  with 
articulation  for  the  fib- 
ula ;  4,  Fossa  for  the 
insertion  of  external 
meniscus ;  5,  Fibula, 
forming  with  the  tibia 
the  tibial  arch ;  6,  Shaft, 
or  body  of  the  tibia; 
7,  8,  External  and  in- 
ternal malleoli,  inferior 
tuberosities,  or  lateral 
processes  of  the  tibia ; 
9,  Articular  trochlese 
with  a  median  ridge, 
for  articulation  with  the 
astragalus. 


102  TEE  BONES. 

bone,  the  tibial  arch.  Its  superior  extremity,  wide  and  flattened  on  both 
sides,  lias  received  the  name  of  head ;  it  offers,  on  its  internal  face,  a 
diarthrodial  facet  to  articulate  ■with  the  external  and  superior  tuberosity 
of  the  tibia;  on  its  external  face  it  shows  ligamentous  imprints.  The 
inferior  extremity  of  the  fibula  terminates  in  a  blunt  point,  and  gives 
attacliment  to  the  ligamentous  fibres  that  unite  it  to  the  tibia. 

The  fibula  is  sometimes  continued  to  the  external  inferior  tuberosity 
of  the  latter  bone,  with  which  it  is  confounded ;  and  as  it  is  particularly 
under  such  circumstances  that  this  tuberosity  has  been  noticed  to  be  deve- 
loped from  a  special  nucleus,  it  seems  quite  natural,  having  regard  to 
the  disposition  observed  in  pachyderms  and  carnivores,  to  consider  it  as 
the  inferior  extremity  of  the  fibula  joined  to  the  tibia.  With  these  animals, 
indeed,  the  tuberosity  or  external  malleolus  is  foimed  by  the  inferior  ex- 
tremity of  the  fibula. 

StruHure  and  development. — This  bone  is  very  compact,  and  developed 
from  a  single  nucleus  of  ossification. 

3.  Patella. 

A  small,  short,  and  very  compact  bone,  situated  in  front  of  the  femoral 
trochlea,  and  annexed  to  the  tibia,  to  which  it  is  attached  by  three  extremely 
solid  ligamentous  bands. 

The  small  polyhedron  which  it  represents  only  offers  for  observation 
three  faces :  the  superior,  roughened,  and  serving  for  the  insertion  of  the 
triceps  cruralis  and  rectus  muscles;  the  anterior,  convex  and  irregular  ;  and 
the  third,  the  posterior,  moulded  on  the  femoral  trochlea,  to  which  it  is  but 
imperfectly  adapted.  In  the  fresh  state,  however,  the  articular  surface 
formed  by  the  latter  face  is  completed  by  a  fibro-cartilaginous  apparatus, 
which  will  be  noticed  when  describing  the  femoro-tibial  articulation.  This 
articular  surface  is  composed :  1,  Of  a  median  ridge,  which  occupies  the 
bottom  of  the  trochlear  cavity  ;  2,  Of  two  depressed,  gliding,  lateral  facets 
on  the  sides  of  this  cavity ;  the  internal  facet  is  always  larger  than  the 
external,  a  disposition  which  permits  the  patella  of  one  limb  to  be  distin- 
guished from  that  of  the  other. 

POSTERIOR   FOOT. 

This  region,  which  bears  the  greatest  resemblance  to  the  same  region  in 
the  anterior  limb,  comprises  three  subdivisions :  the  tarsus,  metatarsus, 
and  the  digital  region. 

1.  Bones  of  the  Tarsus. 

These  are  short,  very  compact  bones,  six  or  seven  in  number,  and 
situated  between  the  inferior  extremity  of  the  tibia  and  the  superior 
extremity  of  the  metatarsal  bones ;  they  are  arranged,  like  the  bones  of 
the  carpus,  in  two  tiers — a  superior  and  an  inferior. 

The  su])f3rior  row  only  comprises  two  bones,  the  largest ;  these  are  the 
astragalus  and  the  cnh.aneus  (or  calcis).  The  inferior  row  is  formed,  oiit- 
wardly,  by  the  cuboides  alone ;  inwardly  and  anteriorly,  it  is  subdivided 
int )  two  secondary  rows,  the  superior  of  which  is  constituted  by  the 
scaphoides,  and  the  inferior  by  the  large  and  small  cuneiform  bones.  The 
last  is  sometimes  divided  into  two,  in  which  case  there  are  three  cuneiforms ; 
then  the  total  number  of  the  bones  is  seven. 

Astragalus.— An    irregular    cubical    bone,    situated    in    front   of    the 


TEE  POSTERIOR  LIMBS. 


103 


calcaneus,  between  tlie  tibia  and  the  scaphoid,  and  divided  into  five  faces  : — 

1,  A  superior  and  anterior^  formed  as  an 
articular  pulley  to  correspond  to  the  in- 
ferior extremity  of  the  tibia;  this  pulley, 
obliq^ue  from  above  downwards,  forwards, 
and  outwards,  may  be  considered  as  the 
type  of  the  most  perfect  trochlea  in  the 
organism ;  its  groove  receives  the  median 
tenon  of  the  tibia,  and  its  two  ridges  or  lips 
fit  into   the   lateral    furrows  of  that  bone. 

2,  An  inferior  face,  occupied  by  a  slightly 
convex  articular  sui-face  responding  to  the 
scaphoid  ;  this  surface  is  notched  outwardly 
by  an  excavation  for  ligamentous  insertion. 

3,  A  posterior  face,  irregular,  cut  into  three 
or  four  diarthrodial  facets  adajited  for 
similar  facets  on  the  calcaneus,  and  which 
are  separated  by  a  wide,  rugged  excavation. 

4,  An  external  face,  covered  with  imprints. 

5,  An  internal  face,  provided  below  with 
a  small  tubercle  of  insertion. 

Calcaneus. — A  bone  vertically  elongated, 
flattened  on  both  sides,  and  presenting  two 
faces,  two  borders,  and  two  extremities. 

The  external  face  is  smooth  and  nearly 
plane.  The  internal  face  is  excavated  into 
a  gliding  groove  to  form  the  tarsal  arch,  in 
which  passes  the  tendon  of  the  perforans. 
The  anterior  border  is  slightly  concave. 
The  posterior  border  is  thicker,  straight, 
and  rugged.  The  superior  extremity, 
slightly  tuberous,  constitutes  the  summit 
of  the  calcaneus,  and  is  divided  into  three 
parts :  a  middle,  which  gives  attachment  to 
the  tendon  of  the  gastrocnemius ;  the  other, 
the  anterior,  is  a  smooth  surface  on  which 
this  tendon  rests  when  the  foot  is  much 
flexed ;  the  third,  altogether  posterior,  also 
constitutes  a  gliding  surface  for  the  tendon 
of  the  perforatus.  The  inferior  extremity, 
wide  and  voluminous,  shows  in  front  three 
or  four  articular  facets  which  correspond 
to  the  astragalus,  and  are  separated,  like 
those  of  the  last  bone,  by  an  irregular  and 
slightly  excavated  surface  of  insertion. 
Below,  it  shows  for  articulation  with  the 
cuboid  a  fifth  facet,  continuous  with  one  of 
8,  Small  metatarsal  bone;  9.  Suf-    the  preceding. 

Development. — The  calcaneus  is  deve- 
loped from  two  nuclei  of  ossification,  one  of 
which  is  for  the  summit. 

Cuboid  bone. — This  little  bone,  situated 
at  the  external  side  of  the  scaphoid  and  the 


LEFT   HIKD   FOOT;   EXTERNAL 
ASPECT. 

1,  Tibia  ;  2,  Summit  of  calcis  or  cal- 
caneus ;  3,  Astragalus  ;  4,  Cuboid  ; 
5,  Scaphoid;  6,  Cuneiform  mag- 
num ;    7,   Large  metatarsal   bone , 


fraginis,  proximal,  or  first  phalanx  ; 
10,  Sesamoid  bones  ;  11,  Coronary, 
second,  or  middle  phalanx :  12, 
Pedal  bone,  or  third  or  distal 
phalanx 5  14,  Navicular  bone;  15, 
Basilar  process  of  pedal  bone. 


104 


TEE  BONES. 


large  cuneiform  bone,  between  the  calcaneus  and  two  of  the  metatarsals,  does 
not  resemble  a  cube,  but  a  parellelopiped  elongated  from  before  to  behind. 
It  offers  six  faces :  a  superior,  an  articular  face,  and  in  contact  with  the 
calcaneus ;  an  inferior,  also  articular,  responding  to  the  principal  and  external 
rudimentary  metatarsal  bones ;  an  internal,  furnished  with  three  facets  for 
contact  with  the  scaphoid  and  great  cuneiform,  and  crossed  from  before 
to  behind  by  a  fissure,  which  forms  with  these  two  bones  a  vascular  canal ; 
an  external,  an  anterior,  and  a  posterior,  covered  with  imprints. 

Scaphoid  hone  (the  lat-ge  cuneiform  of  Percivall). — Flattened  above  and 
below,  it  is  described  as  having  two  faces  and  a  circumference.  The /aces, 
both  articular,  are  furrowed  by  a  channel  of  insertion,  and  are  distinguished 
as  superior  and  inferior.  The  first  is  concave,  and  responds  to  the  astra- 
galus ;  the  second  is  convex  and  in  contact  with  the  two  cuneiform  bones. 
The  circumference  offers,  outwardly,  two  small  facets  which  are  adapted  to 
similar  facets  on  the  cuboid  bone.  For  the  remainder  of  its  extent,  it  is 
covered  with  imprints. 

Great  Cuneiform  hone  (the  middle  cuneiform  of  Percivall). — Flattened 
above  and  below,  and  triangular  in  shape,  this  bone  is  much  smaller  than 
the  scaphoid,  though  resembling  it  in  a  striking  manner.  Its  superior  face 
is  in  contact  with  the  latter  bone,  and  its  inferior  face  articulates  with  the 
middle  and  internal  lateral  metatarsal  bones.  Its  external  horder  is 
provided  with  one  or  two  facets  to  correspond  with  the  cuboid  bone ;  and  its 
internal  horder  also  offers  one,  which  is  in  contact  with  another  on  the  small 
cuneiform.     Its  anterior  horder  is  roughened  throughout  its  extent. 


Fig.  66. 


Fig.  67. 


LEFT  HOCK  ;  FRONT  VIEW.  LEFT  HOCK  ;  INTERNAL  ASPECT. 

1,  Apex  of  calcaneus ;    2,  Astragalus,   inner       1,    Apex    of  calcaneus ;    2,  Inner   articular 
ridge;    3,  Scaphoid;    4,  Cuneiform   mag-  ridge  of  astragalus;  3,  Navicular,  scaphoid, 

num  ;  5,  Cuboides.  or  cuneiform  medium;    4,  Cuneiform  mag- 

num ;  5,  Cuboides  ;   6,  Cuneifoi-m  parvum. 

Small  Cuneiform  hone. — Situated  at  the  inner  side  of  the  tarsus,  this 
bone,  the  smallest  of  any  yet  examined,  is  elongated  from  before  to  behind, 
flattened  on  both  sides,  and  wedged  in  between  the  os  scaphoides,  the  large 
cuneiform  bone,  and  the  large  and  internal  small  rudimentary  metatarsal 
bones,  with  which  it  corresponds  by  four  articular  facets :  a  superior,  two 
inferior,  and  one  internal.  When  this  bone  is  in  two  portions,  there  are 
then  three  cuneiforms,  which  may  be  distinguished,  as  in  Man,  by  naming 
ih^xa  first,  second,  and  third. 


THE  POSTERIOR  LIMBS. 


105 


Ficr. 


2.  Bones  of  the  Metatarsus. 

These  bones  are  three  in  number,  a  median  and  two  lateral,  and  oflfer  the 
greatest  analogy  to  the  metacarpal  bones.  This  enables  us  to  dispense  with 
a  general  description  of  them,  and  to  confine  oiu-selves  only  to  indicating 
the  differential  characters  which  distinguish  them  from  the  corresponding 
bones  in  the  anterior  limb. 

The  p-incipal,  or  median  metatarsal  bone,  is  longer  than  the  same 
metacarpal,  and  its  body,  instead  of  being  slightly  compressed  before  and 
behind,  is  nearly  a  regular  cylinder.  It  presents  out- 
wardly a  fissure  which  is  directed  at  first  obliquely 
backwards  and  downwards,  and  afterwards  descends 
vertically  along  the  lateral  external  metatarsal  bone. 
The  articular  surface  of  the  superior  extremity  is  ex- 
cavated in  its  centre  by  a  large  fossa  of  insertion.  The 
inferior  extremity  is  at  the  same  time  wider  and  thicker 
than  that  of  the  metacarpus. 

Of  the  two  rudimentary  (digital)  or  lateral  metatarsal 
hones,  the  external  is  always  longest  and  thickest.  The 
internal  bears  on  the  superior  face  of  its  head  three 
articular  facets,  two  of  which  respond  to  the  small 
cuneiform,  and  the  third  to  the  large  bone  of  that  name. 

3.  Bones  of  tJie  Digital  Region. 

The  digital  region  of  the  posterior  closely  resembles 
that  of  the   anterior  limb.     The  analogy  in  the  con- 
formation of   these  bones  is  even  pushed  so  far,  that  Mtl  Itj 
it  becomes  very  difficult  to  distinguish  them  from  one 
another. 

It  is  remarked,  nevertheless :  1,  That  the  first  pha- 
lanx is  not  so  long  as  in  the  anterior  limb,  and  less  K^M  ;  '|(] 
wide  and  thick  at  its  inferior  extremity,  but  is,  on  the 
contrary,  wider  and  thicker  at  its  superior  extremity  ;  2, 
That   the   lateral   diameter  of  the  second   phalanx   is 
shorter ;    3,  That   the   third  phalanx,   less  spread  out 
towards  its  inferior  border,  has  more  the  shape  of  a  V, 
and  that  its  inferior  face  is  more  concave ;  4,  That  the   posterior  aspect  of 
sesamoids  are  less  voluminous;  5,  That  the  navicular     ^^ft  metatarsus. 
bone  is  shorter  and  narrower.                                                 1?  Head  of  principal 

metatarsal  bone ;  2, 

3,  External  and  in- 
ternal splint  bones, 
or  metatarsals  of  the 
rudimentary  digits ', 

4,  Rough  surface  for 
insertion  of  suspen- 
sory ligament ;  5, 
Nutrient  foramen; 
6,  Middle  ridge  of 
inferior  articular 
surface. 


DrPFEBENTIAL  CHARACTERS  OF  THE   POSTERIOR  LIMB  IN 
OTHER   THAN   SOLIPED   ANIMALS. 

A.  Pelvis. — It  is  remarked:  1,  That  in  all  the  dome&ticated 
animals,  with  the  exception  of  Solipeds,  the  direction  of  the  cnx?3 
is  nearly  horizontal ;  2,  That  in  all,  except  Solipeds,  the  ilium 
tends  to  assume  a  vertical  direction ;  3,  That  in  all  the  trans- 
verse diameter  of  the  pelvis  is  relatively  less  extensive. 

In  the  Ox,  Sheep,  and  Goat,  the  space  between  the  two  coxeb 
is  scarcely  so  great  in  front  as  behind ;  the  ilium  is  not  volumi- 
nous, and  has  only  three  processes  on  the  superexternal  iliac 
spine.  There  is  no  furrow  on  the  lower  face  of  the  pubis,  and 
its  upper  face,  like  that  of  the  ischium,  is  very  concave.  Three  eminences  are  spen  on 
the  postero-external  angle  of  the  ischium.  In  early  life,  the  ischio-pubic  symphysis 
shows  an  epiphysary  nucleus  in  the  middle  of  its  inferior  face.  (The  epiphysis  on 
the  inner  border  of  the  ischium  has  been  considered  by  some  anatomists  as  an  inde- 
pendent bone,  and  described  by  them  as  the  interischial  bone.) 


106  THE  BONES. 

The  rim  of  the  cotyloid  cavity  has  also  three  notches,  and  the  supracotyloid  crest,  or 
ischiatic  spine,  is  very  elevated  and  sharp,  and  but  little  roughened  outwardly. 

The  externiil  iliac  fossa  of  the  Sheep  and  Goat  is  separated  into  two  portions  by  a  small 
longitudinal  crest. 

The  pelvis  of  the  Pig  closely  resembles  that  of  the  smaller  ruminants;  though  the 
crest  of  the  ilium  is  convex,  and  there  is  no  protuberance  outside  the  iachio-pubic 
symphysis. 

In  Carnivora  the  lateral  diameter  of  the  pelvis  is  greater  behind  than  in  front.  The 
ilium  is  nearly  vertical,  and  its  external  face  is  much  depressed.  The  notch  forming  tlie 
ischial  arcli  occupies  no  more  than  the  internal  moiety  of  the  posterior  border  of  the 
ischium  ;  between  this  arch  and  the  ischiatic  tuberosity  is  a  rugged  lip  directed  down- 
wards.    There  is  no  furrow  on  the  la\ver  face  of  the  pubis. 

B.  Thigh. — In  ail  the  domesticated  animals  except  Solipeds,the/emMr  tends  to  become 
curved,  prismatic,  and  triangular  *,  the  posterior  tace  contracts,  and  the  surfaces  of  insertion 
that  it  presents  gradually  approach  each  other  until  they  become  confounded  and  form  the 
linea  aspera  in  certain  species.  The  head  is  more  distinct ,  the  small  trochanter  is  a 
rough  tubercle,  and  is  joined  to  the  large  trochanter  by  an  obliijue  osseous  lip ;  the  latter 
trochanter  subsides  and  forms  a  single  ninss  whose  summit  and  convexity  are  con- 
founded ;  the  third  trochanter,  the  fossa,  and  the  supracondyloid  crest  are  more  or  less 
effaced. 

In  the  Ox,  there  is  no  subtrochanterian  crest ;  the  supracondyloid  fossa  is  shallow, 
and  the  crest  little  noticeable.  The  head  is  well  detached  and  1  as  its  centre  ex- 
cavated by  a  shallow  fossa  of  insertion.  The  trochlea  is  narrow,  and  its  inner  border 
ascends  much  higher  on  the  anterior  face  of  the  bone  than  the  external. 

In  the  Sheep  and  Goat,  the  general  form  of  the  femur  resembles  that  of  the  Ox.  It  is 
observed,  however,  that  the  body  is  slightly  curved  backwards ;  that  the  supracondyloid 
fossa  is  nearly  obliterated;  that  the  trochanter  has  subsided  nearly  to  a  level  with  the 
articular  head,  and  that  the  trochlea  is  circumscribed  by  two  equal-sized  lips. 

In  the  femur  of  the  Pig  there  is  also  noticed  a  supracondyloid  fossa,  but  it  is  wide 
and  shallow;  the  rugosities  of  the  posterior  face  are  replaced  by  some  salient  lines;  the 
trochanter  is  on  a  level  with  the  liead ;  the  latter  is  supported  by  a  somewhat  constricted 
necii,  and  is  situated  within  and  in  front  of  the  great  trochanter.  This  latter  disposition 
changes  the  direction  of  the  great  axis  of  the  superior  extremity,  which  obliquely  crosses 
that  of  the  inferior  extremity. 

In  the  Dog  and  Cat,  the  femur  is  long  and  curved  like  a  bow.  The  rugged  surfaces 
of  the  posterior  face  are  confounded,  and  form  two  crests  representing  the  linea  aspera  of 
the  human  femur.  These  crests  do  not  lie  against  eacii  otlur  in  the  middle  portion  of 
the  bone;  they  are  merely  parallel,  then  they  diverge  above  and  below,  to  terminate  ' 
beneath  the  great  and  small  trochanters,  and  above  the  two  condyles.  The  great  tro- 
chanter is  not  so  high  as  the  articular  head.  The  femur  of  Carnivora  is  also  distin- 
guished :  1,  By  the  complete  absence  of  the  third  trochanter  and  the  supracondyloid 
fossa — this  last  being  replaced  by  a  small  tubercle  which  terminates  below  the  external 
branch  of  the  linea  aspera;  2,  By  the  m.trked  constriction  and  length  of  the  neck  sup- 
porting the  articular  head;  3,  By  the  depth  of  the  digital  fossa,  which  is  bordered  by  an 
oblique  lip  extending  from  tlie  great  to  the  small  trochanter. 

C.  Leg. — In  the  leg-bone  there  is  observed,  in  the  various  domesticated  animals,  differ- 
ences analogous  to  those  mentioned  as  existing  in  \he  fore-arm  of  the  thoracic  liml).  More 
particularly  is  this  the  case  with  regard  to  the  development  of  the  fibula ;  in  Kuminants 
this  bone  is  reduced  to  its  inferior  nucleus.  In  these  animals  the  patella  is  also  very 
narrow ;  and  in  all  the  domesticated  species  except  Solipcds,  the  articular  grooves  in  the 
lower  end  of  the  tibia  are  directed  immediately  from  before  to  behind. 

In  the  Ox,  the  tibia  is  short ;  it  is  longer  in  the  Goat  and  the  Sheep.  The  tihia  of 
these  animals  is  remarkable  for:  1,  The  absence  of  the  lateral  facet  on  the  supero- 
external  tuberosity;  2,  The  absence  of  a  vertical  fossa  on  the  anterior  tuberosity; 
3,  The  absence  of  roughened  lines  on  the  posterior  face ;  the  obliquity  downwards  and 
inwards  of  the  inferior  articular  surface.  The  most  salient  point  of  this  surface  is  the 
anterior  extremity  of  the  middle  tenon. 

The  body  of  the  fibula  and  its  upper  extremity  are  replaced  by  a  fibrous  cord  which 
is  sometimes  ossified  wholly  or  in  part. 

In  the  Pig,  the  fibula  is  flattened  on  both  sides,  extends  the  whole  length  of  the  leg, 
and  is  united  to  the  tibia  by  its  two  extremities  :  above,  by  a  diarthrodial  facet  below, 
by  an  interosseous  ligament.  It  is  developed  from  three  ossific  centres;  the  inferior 
articulates  with  the  calcaneus  and  astragalus,  and  forms  a  prominence  resembling  the 
external  malleolus. 

In  Carnivora,  the  tibia  is  long  and  slender,  and  presents  a  salient  anterior  crest.    The 


THE  POSTERIOR  LIMBS.  107 

fibula  is  also  as  long  as  the  tibia,  and  is  united  to  that  bone  at  three  points :  at  the  two 
extremities  by  articular  surfaces,  in  the  inferior  third  and  middle  by  an  interosseous 
ligament. 

D.  Posterior  Foot. — 1.  Boms  of  the  tarsus. — The  number  of  tarsal  bones  varies  a 
little  in  the  domesticated  animals,  as  the  following  list  will  show  : 

Carnivora  and  Pig 7 

Ox,  Sheep,  and  Goat 5 

In  the  Dog,  Cat,  and  Pig.  there  are  three  cunetfoi-m  bones,  and  in  the  Ox  and  Sheep, 
in  addition  to  there  being  only  two  cuneiforms,  the  scaphoid  and  cuboid  bones  are  «on- 
solidated  into  one  piece. 

The  astragalus  of  the  carnivora  articulates  with  the  scaphoid  by  means  of  a  veritable 
head,  separated  from  the  rest  of  the  bone  by  a  constriction  termed  the  nf  ck  of  the  astra- 
galus.    The  cuboid  and  the  cuneiform  bones  respond  to  all  the  metatarsals. 

In  the  Pig,  the  astragalus  and  calcaneus  are  very  long.  The  cuneiforms  and  cuboid 
respond  to  the  four  perfect  digits. 

The  tarsus  of  the  domesticated  Ruminants  is  slender  above.  The  astragalus  is  elongated 
from  above  to  below,  and  is  united  to  the  scaphoid  by  an  antero-posterior  groove,  and  to 
the  calcaneus  by  a  more  superficial  vertical  gi'oove.  The  calcaneus  is  long  and  tiin; 
the  posterior  gliding  surface  on  the  summit  is  excavated  into  a  channel ;  the  small 
cuneiform  is  pisiform  and  but  slii,'htly  developed. 

2.  Pones  of  the  7netatarms. — The  metatarsus  is  also  a  region  in  which  the  niunber  of 
bones  varies  in  the  domesticated  animals.  Thus  in  the  Carnivora  and  Pig  there  are 
five,  and  only  two  in  PiImixants. 

The  metatarsals  of  the  Carnivora  and  Pig  are  exactly  like  the  same  bones  in  the 
anterior  limb.     Those  of  Buminants  are  slightly  diflerent. 

In  the  Dog  and  Cat  are  one  rudimentary  and  four  perfect  metatarsals.  The  former 
is  articulated  with  the  internal  cuneiform,  and  represents  tlie  vestige  of  the  thumb. 

The  Pig  has  four  perfect  metatarsals,  and  an  internal  rudimentary  one.  The  latter 
is  a  small  bone  flattened  on  both  sides,  articulating  by  means  of  a  diarthrodial  facet,  and 
sometimes  consolidated  behind  the  upper  end  of  the  fourth  metatarsal. 

In  the  Ox,  Sheep,  and  Goat,  is  found  a  principal  and  a  rudimentary  metatarsal  bone. 
The  latter  is  like  the  rudimentary  metacarpal  bone,  bat  the  former  dillers  from  the 
principal  metacarpal  bone  in  being  longer,  quadrilateral  in  form,  and  having  a  vascular 
canal  traversing  the  posterior  face  of  its  upper  extremity. 

3.  Bones  of  the  digital  region. — In  all  the  domesticated  animals,  the  posterior  digits 
comport  themselves  exactly  like  the  anterior.  The  Carnivora  alone  ofl'er  a  notable  ditfer- 
ence;  in  them,  in  reality,  the  thumb  does  not  exist,  or  rather,  it  is  only  represented  by 
the  rudimentary  metatarsal  bone  alluded  to  above.  Nevertheless,  it  fr(  quent  i  y  occurs 
that  a  completely  developed  thumb  is  found  in  this  animal ;  and  in  this  case  the  rudi- 
mentary metatarsal  is  ordinarily  followed  by  a  ligamentous  cord,  to  which  is  suspendi  d  a 
bony  stylet  that  represents  either  the  inferior  extremity  of  the  metatarsal,  or  the  fiitt 
phalanx ;  it  is  to  this  stylet  that  are  found  articulated  in  succession  the  second  and  third 
phalanges. 

(Professor  Fuchs,  of  Carisruhe,  found,  in  a  Newfoundland  dog,  four  true  claws  and 
two  false:  the  internal  of  the  latter  corresponded  to  a  well-developed,  small  metatarsal 
bone,  while  the  external  was  only  rudimentiiry,  terminating  in  a  point,  and  bound  to  the 
tarsus  by  a  simple  ligament.) 

COMPARISON   OF   THE    ABDOMINAL   LIMB    OF   MAN    WITH   THAT   OP  ANIMALS. 

A.  Pelvis. — The  longitudinal  axis  of  the  pelvis  of  Man  forms,  with  the  horizon,  an 
angle  of  about  40". 

The  bones  which  compose  it  are  proportionately  larger  and  stronger  t'  an  in  all  the 
domesticated  animals. 

The  two  faces  of  the  ilium,  and  especially  the  inner  fa^e,  are  much  hoUoweil ;  the 
iliac  crest  has  the  form  of  an  italic  ,S'. 

The  pubis  alone  participates  in  the  formation  of  the  pelvic  symphysis,  and  ihe  con- 
cavity which,  in  the  Oomtsticated  animals,  is  called  the  ischial  arch,  is  designated  in  ^lan 
the  pubic  arch. 

Ill  consequence  of  the  excavation  on  the  inner  face  of  the  ilium,  the  pelvic  cavity 
may  be  divided  into  the  great  and  lesser  pelvis  In  the  latter  are  lodged  the  gCiiital 
and  urinary  organs,  as  well  as  the  extremity  (  f  th'?  d!g,_-.-tive  tube. 

B.  Thigh. — The  femui-  of  Man  is  nearly  vertical,  and  situated  in  a  direction  slightly 


lOS 


THE  BONES. 


oblique  downwards  and  inwards ;  it  presents  a  curvature  forwards.  The  body  of  the  bone 
is  prismatic  and  triangular  in  its  middle  part ;  the  posterior  border  of  tiiis  prism  forms  a 
somewhat  salient  crest,  which  takes  the  plaue  of  all  the  insertion  eminences  on  the  pos- 
terior aspect  of  the  femur  in  animals,  and  is  designated  the  littea  asptra.  This  line 
bifurcates  above  and  below ;  below,  the  branches  margin  a  triangular  or  popliteal  space. 


Ficr.  69. 


HUMAN   PELVIS;   FEMALE. 

1,  Last  lumbar  vertebra;  2,  2,  Intervertebral  substance;  3,  Promontory  of  the 
sacrum  ;  4.  Anterior  surface  of  the  sacrum  ;  5,  Coccyx  ;  6,  Iliac  fossce  ;  7,  Antero- 
superior  spinous  process;  8,  Antero-inferior  spinous  process;  9,  Acetabulum. — 
a,  Its  notch ;  6,  Body  of  ischium ;  c.  Its  tuberosity ;  d,  Its  spine ;  e,  Pubis ;  /, 
Symphysis  pubis  ;  g,  Arch  of  the  pubes ;  h,  Angle  of  os  pubis ;  i,  Spine  of  pubes, 
with  crest  Ijetvveen  it  and  h ;  k,  k,  Pectineal  line ;  I,  I,  llio-pectineal  hue,  with  its 
prolongation,  m,  m ;  n,  llio-pectineal  eminence;  o,  Smooth  surface  for  femoral 
vessels  ;  p,  p,  Great  sacro-ischiatic  notch. 


The  head  is  supported  by  a  long  neck,  inserted  obliquely  into  the  superior  extremity. 
The  two  condyles  are  joined  together  in  front  by  tlie  trochlea,  which  is  wide  and 
shallow. 

C.  Leg. — Three  bones :  the  tibia,  fibula,  and  patella. 

The  tibia  is  very  long  ;  its  crest  (or  spinous  process)  is  mucli  more  developed  than  in 
any  of  the  domesticated  animals,  and  describes  a  kind  of  curve  like  an  italic  S.  On  the 
inner  aspect  of  the  inferior  extremity  is  seen  a  voluminous  process  which  occupies,  inwardly, 
a  portion  of  the  tibio  tarsal  articulation:  this  is  the  internal  malleolus.  The  articular 
surface  is  not  exactly  formed  to  correspond  with  the  whole  articular  surface  of  the 
astragalus. 

The  fibula  is  as  long  as  the  tibia.  It  is  prismatic,  and  slightly  twisted  on  itself.  It 
articulates  above  and  below  with  the  tibia.  The  lower  extremity  responds  to  the  astra- 
galus, and  forms  a  prominence  named  the  external  malleolus. 

There  is  nothing  particular  to  note  in  the  patella. 

D.  Foot. — The /oof  of  Man  is  situated  in  a  horizontal  direction.  Its  upper  aspect  is 
convex ;  its  inferior  face  is  excavated,  and  it  rests  on  the  ground  by  its  two  extremities. 

1.  Tarsus.— In  the  tarsus  there  are  seven  bones,  three  of  wliich  are  cuneiform  The 
astragalus  articulates  with  the  tibia  and  fibula;  it  responds  to  the  scaphoid  by  a  well 
detached  convex  articular  surface,  named  the  head. 

In  the  bones  of  the  lower  row,  it  is  remarked  that  the  cuboid  responds  to  the  fifth 
and  fourth  metatarsals  :  the  first  cuneiform  to  the  third;  the  second  cuneiform  to  the 
second  metatarsal,  and  the  third  to  the  first. 

2.  Mefatarstis. — The  metatarsus  is  comiioscd  of  five  bony  columns,  nearly  parallel  to 
each  other.  They  are  enumerated  from  without  to  within,  and  increase  in  length  from 
the  first  to  the  fourth;  tlie  fifth  is  the  shortest  and  most  voluiidnous. 


THE  LIMBS  ly  GENERAL. 


109 


3.  Digital  region. — This  comprises  five  digits  or  toes.  The  phalanges  of  these  toes 
are  aualogous  to  those  of  the  fingers,  from  which  they  are  distinguished  by  their  small 
size.     They  increase  in  volume  from  the  first  to  the  fifth  digit. 


Fig. 


Fig.  7}. 


Fi?.  72. 


RIGHT   HUMAN   FEMUR*, 
ANTERIOR   ASPECT. 

1,  Shaft;  2,  Head;  3, 
Neck ;  4,  Great  tro- 
chanter ;  5,  Anterior 
intertrochanteric  line ; 
6,  Lesser  trochanter ;  7, 
External  condyle  ;  8,  In- 
ternal condyle ;  9,  Tu- 
berosity for  attachment 
of  external  lateral  liga- 
ment ;  10,  Fossa  for  ten- 
don of  origin  of  popliteus 
muscle;  11,  Tuberosity 
for  attachment  of  in- 
ternal lateral  ligament. 


HUMAN  TIBIA.  AND  FIB- 
ULA OF  RIGHT  LEG; 
ANTERIOR   ASPECT. 

1,  Shaft  of  tibia ;  2,  Inner 
tuberosity ;  3,  Outer 
tuberosity ;  4,  Spinous 
process ;  5,  Tubercle  ;  6, 
Internal  surface  of  shaft ; 
7,  Lower  extremity  of 
tibia;  8,  Internal  mal- 
leolus; 9,  Shaft  of  fib- 
ula ;  10,  Its  upper  ex- 
tremity; 11,  Its  lower 
extremity;  between  1 
and  6  is  the  sharp  crest 
of  the  tibia. 


DORSAL  SURFACE  OF  LEFT 
HUMAN   FOOT. 

1,  Astragalus;  2,  Its  An- 
terior extremity  articu- 
lating with  the  cuboid 
bene,  4;  3,  3,  Calcis; 
4,  Scaphoid;  5,  Inter- 
nal cuneiform  bone  ;  6, 
Middle  cuneiform  bone ; 
7,  External  cuneitorm 
bone;    8,  Cuboid  bone; 

9,  Metatarsal  bones  of 
first    and    second    toes; 

10,  First  phalanx  of 
great  toe;  11,  Second 
dittc;  1-2,  13,  14.  Pha- 
langes of  second  toe. 


Article  YI. — The  Limbs  in  General  and  their  Parallelish. 

A.  The  Limbs  in  General. — The  interrupted  columns  which  compose 
the  limbs  are  destined  not  only  to  support  the  trunk  in  a  stationary  attitude, 
but  also  to  transport  it  during  progression.  This  double  destination  gives  rise 
to  a  difference  between  the  anterior  and  posterior  members.   The  front  limbs, 


no  THE  BONES. 

being  nearer  the  centre  of  gravity  than  those  behind,  have  to  sustain  the 
largest  share  of  the  weight.  They  ought,  consequently,  to  be  sj^ccially 
organised  as  organs  of  support.  Therefore  it  is  that  the  four  princij^al  rays 
composing  each  of  them — shoulder,  arm,  fore-arm,  and  foot — although  flexed, 
or  disposed  to  be  flexed,  in  an  inverse  sense  to  one  another,  oppose  to  the 
pressure  of  the  weight  of  the  trunk,  which  tends  incessantly  to  throw  them 
down,  obstacles  purely  mechanical,  and  of  such  energy  that  we  may  still 
understand  how  the  body  can  be  sustained  on  the  anterior  limbs,  if  we 
suppose  all  the  muscular  masses  surrounding  these  bony  rays  removed  except 
one. 

Thus,  the  weight  of  the  body  is  at  first  transmitted  to  the  scapula  through 
the  muscles  that  attach  that  bone  to  the  trunk.  It  then  passes  to  the 
humerus,  aud  from  thence  to  the  radius,  to  be  thrown,  finally,  on  the  different 
pieces  composing  the  foot.  Now  the  humerus  forming  with  the  scapula  an 
angle  which  is  open  behind,  and  with  the  bones  of  the  fore-arm  another  angle 
open  in  front,  the  weight  of  the  body  pressing  continually  on  these  angles  tends 
to  close  them,  and  thus  cause  the  flexion  of  the  bony  rays.  But  this  result  is 
prevented  by  the  combined  action  of  two  muscular  powers — the  biceps  and 
the  extensors  of  the  fore-arm.  With  regard  to  the  radius,  carpus,  and 
metacarpus,  owing  to  their  vertical  direction  they  themselves  support  the 
pressure  of  the  weight  of  the  body  without  requiring  any  muscular  aid.  But 
the  digital  region,  being  directed  obliquely  forward  and  downward,  forms, 
with  the  principal  metacarpal,  a  third  angle  open  in  front,  for  the  sustenance 
of  which  nature  has  given  solid,  inert,  or  contractile  mechanical  bands. 

The  anterior  limbs  are  also  agents  of  trausjiort,  for  they  can  elevate  the 
trunk  by  the  spring  of  their  bony  rays,  and  fix  themselves  on  the  ground  by 
their  free  extremity. 

The  posterior  limbs  are  less  favourably  disposed  than  those  in  front  to 
assinne  the  function  of  columns  of  support,  as  their  rays  are  for  the  most 
part  in  a  state  of  permanent  flexion,  and  joined  in  an  angular  manner  to  one 
another,  as  may  be  seen  by  glancing  at  the  skeleton  (See  Figs.  1,  2,  3,  4, 
5),  It  is  therefore  necessary  that  muscular  agency  should  prevent  the 
breaking-down  of  these  rays.  Though  defective  as  supporting  columns, 
they  are  nevertheless  admirably  designed  to  serve  as  agents  of  locomotion. 
The  slightest  erection  of  these  inclined  rays  propels  the  mass  of  the  body 
forward,  and  this  impulsion  is  almost  wholly  transmitted  to  the  trunk  in 
consequence  of  the  very  intimate  union  of  the  pelvis  with  the  vertebral 
column. 

B.  Parallel  between  the  Anterior  and  Posterior  Limbs. — After 
what  has  just  been  said,  it  will  be  seen  that  the  anterior  limbs  are  more  par- 
ticulai'ly  destined  for  the  support  of  the  body,  while  the  jDosterior  ones  more 
especially  play  the  part  of  impulsive  agents  in  the  locomotory  acts. 

Notwithstanding  this  difference  in  the  functions  assigned  them,  these  two 
columns  offer  in  their  conformation  such  striking  resemblances  to  each  other, 
that  some  authors  have  been  inclined  to  consider  the  posterior  as  an  exact 
repetition  of  the  anterior  limb.  The  following  is  a  brief  analysis  of  the 
analogies  existing  between  them. 

At  the  end  of  the  last  century,  Winslow  and  Vicq-d'Azyr,  and  nearer  our 
own  time,  Cuvier,  Flourens,  Paul  Gervais,  Martins,  Gegenbaur.  and  Lavocat, 
have  occupied  themselves  with  the  parallelism  existing  between  the  anterior  and 
the  posterior  members.  All  these  anatomists  did  not  absolutely  arrive  at  the 
same  conclusion  ;  for  several  of  them,  forgetting  that  the  question  should  be 
examined  in   the  whole  animal  series,  made  Man  alone  the  subject  of  their 


THE  LIMBS  IN  GENERAL.  Ill 

meditations.  In  such  a  matter,  it  must  not  be  forgotten  that  the  limbs  are 
constructed  with  a  view  to  their  physiological  functions,  and  that  the 
differences  remarked  in  examining  them  in  several  species  are  dictated  by 
the  kind  of  life  the  animals  are  intended  to  lead. 

A'icq-d'AzyrandCuvier  recommend  that  the  anterior  and  posterior  limbs 
of  opposite  sides  should  be  compared.  Martins  and  Gegenbaur,  allo^\ing  a 
torsion  of  the  humerus  of  ISO'^,  advise  that  the  two  members  of  the  same 
side  should  be  collated,  care  being  taken  to  make  allowance  for  the 
untwisting  of  the  180^  contortion  at  the  lower  end  of  the  humerus. 
Lastly,  Flourens  and  Lavocat  contrast  the  two  members  of  the  same  pair 
with  each  other,  after  placing  the  hand  in  a  position  of  natural  pronation  by 
rotation  of  the  radius  on  the  ulna,  and  without  turning  either  limb  or  ray,  or 
even  a  portion  of  a  ray,  no  matter  what  kind  of  animal  may  be  under 
examination.  We  will  adopt  the  latter  proceeding,  as  it  is  the  simplest  and 
most  natural. 

Parallel  between  the  coxa  and  scapula. — The  analogies  existing  between 
these  two  bones  are  but  little  striking  at  first  sight ;  nevertheless,  with  atten- 
tion there  is  no  difficulty  in  finding  in  the  coxa  the  three  pieces  that  enter 
into  the  composition  of  the  shoukler. 

The  ilium  represents  the  scapula.  The  external  iliac  fossa  reminds  one 
of  the  supra-  and  subspinous  fossse.  Occasionally,  there  is  met  with  in  the 
Horse  a  rudiment  of  the  crest  dividing  the  iliac  fossa  into  two  parts,  and,  in 
some  animals— the  Pig,  Sheep,  and  Goat — this  crest,  which  is  the  trace 
of  the  scapular  spine,  becomes  constant  and  very  evident. 

With  regard  to  the  cotyloid  cavity,  it  repeats  in  the  posterior  limb  the 
glenoid  cavity  of  the  scapula.  There  remains  to  determine  in  the  latter 
bone  the  portions  analogous  to  the  ischium  and  pubis.  If  we  rely  upon  the 
evidence  afforded  by  the  muscular  insertions,  we  come  to  the  conclusion  that 
the  ischium  corresponds  to  the  coracoid  process,  and  the  pubis  to  the  clavicle 
of  animals  which  are  provided  with  one.  It  will  also  be  remarked  that  the 
coxa  is  directed  backwards,  while  the  scapula  inclines  obliquely  forwards ; 
this  opposition  in  the  direction  of  the  bones  in  no  way  alters  their  analogies ; 
the  functions  of  the  members  to  which  they  correspond  require  this  inverse 
position. 

Parallel  heticeen  the  femur  and  humerus. — The  resemblance  between 
these  two  bones  is  remarkable.  Thus  there  is  found  in  the  first :  1,  An 
articular  head,  better  detached  than  that  of  the  humerus,  but  shaped  in  the 
same  manner ;  2,  A  trochanter  analogous  to  the  great  tuberosity,  and  also 
like  it  decomposable  into  three  distinct  parts — summit,  crest,  and  convexity  ; 
3,  A  lesser  trochanter,  representing  the  smaller  tuberosity  :  4,  An  eminence 
for  the  insertion  of  the  superficial  gluteus  muscle,  which  takes  the  place  of 
the  deltoid  imprint ;  5,  An  inferior  articular  pulley  continued  between  the 
two  condyles  by  a  non-articulai*  groove ;  this  trochlea  certainly  corresponds 
to  the  median  groove  of  the  inferior  humeral  face. 

There  are,  no  doubt,  differences  between  the  two  bones,  but  they  have 
no  bearing  upon  the  result  just  indicated.  Thus  the  linea  aspera  of  the 
femur  is  situated  behind;  that  of  the  humerus  in  front.  In  the  femur  the 
two  condyles  of  the  inferior  extremity  are  placed  behind  the  trochlea  ;  the 
contrary  holds  in  the  humerus.  These  modifications  are  necessary  in  order 
to  give  the  movements  of  the  limbs  a  convenient  direction.  The  leg  is 
flexed  backward  on  the  thigh,  while  the  fore-arm  is  flexed  in  front  on  the 
humerus. 

Parallel  letiteen  the  hones  of  the  leg  and  those  of  the  fore-arm. — It  is 


112  TEE  BONES. 

more  particularly  in  these  two  regions  that  the  question  of  analogies  has 
been  resolved  in  a  contradictory  manner  by  anatomists.  It  would  have 
appeared  less  complicated  had  it  been  studied  in  a  large  number  of  species. 

It  has  been  j^retended  that  the  patella  and  the  upper  part  of  the  tibia 
represent  the  superior  extremity  of  the  ulna  and  radius;  and  that  the 
inferior  portion  of  the  ulna  is  represented  by  the  fibula,  and  the  lower  part 
of  the  radius  by  that  of  the  tibia.  This  opinion  is  erroneous.  It  is  true 
that  in  Man  the  tibia  and  patella  articulate  with  the  femur,  as  the  superior 
extremity  of  the  ulna  and  radius  responds  to  the  humerus.  But  in  quad- 
rupeds, whose  thoracic  members  are  destined  to  sustain  the  weight  of  the 
body,  this  disposition  is  no  longer  observed ;  the  radius  is  seen  to  give 
support  to  all  the  humeral  surface,  just  as  the  tibia  receives  the  femoral 
surface ;  and,  besides,  the  ulna  becomes  only  a  simple  complement  to  the 
elbow  articulation,  as  the  fibula  does  to  the  femoro-tibial  articulation. 

The  tibia,  therefore,  corresponds  to  the  radius,  and  the  fibula  to  the  ulna. 

The  olecranon  is  rej)resented  by  the  superior  nucleus  of  the  fibula,  and 
not  by  the  patella.  The  latter  bone  is  nothing  more  than  a  kind  of  sesamoid, 
intended  to  facilitate  the  action  of  the  extensor  muscles  of  the  leg.  It 
might  be  objected  to  this  comparison  that,  in  the  anterior  limb,  the  extensor 
muscles  are  attached  to  the  olecranon.  But  we  reply  that  it  matters  little 
where  the  muscles  which  move  the  leg  or  arm  are  fixed  on  one  or  other 
of  the  two  bones  of  these  regions,  because  these  bones  act  conjointly  in  the 
movements  of  flexion  and  extension. 

Parallel  hetween  tJie  hones  of  the  posterior  and  those  of  the  anterior  foot. — 
The  analogy  becomes  so  marked  when  these  two  regions  are  compared,  that 
it  is  scarcely  necessary  to  allude  to  it.  The  tarsal  bones  are  to  the  posterior 
limb  what  the  carpals  are  to  the  anterior  one ;  it  is  even  possible  to  compare, 
one  by  one,  the  several  pieces  in  these  regions.  The  metatarsals  are  but  a 
repetition  of  the  metacarpals ;  while  the  digital  bones  are  so  much  alike  that 
it  is  difficult  to  distinguish  the  anterior  from  the  posterior  phalanges. 


CHAPTEE  III. 

THE   BONES   IN   BIEDS. 

These  animals,  destined  for  the  most  part  to  sustain  themselves  in  the  air,  should 
exhibit  in  the  conformation  of  their  skeleton  all  the  conditions  which  may  favour  ajrial 
locomotion ;  from  this  arise  the  differences  which  distinguish  their  skeleton  from  that 
of  mammalia, — differences  which  will  now  be  rapidly  traced. 

Vertebral  CoLrMN. —  Cervical  vertehrx. — The  cervical  stalk  represents  in  the  bird, 
as  in  the  mammal,  a  kind  of  balancing  pole  curved  like  an  S,  which  snpjjorts  the  head, 
and  by  its  changes  of  form  and  direction  varies  tlie  centre  of  gravity.  When  a  bird 
rises  in  the  air  and  flies  rapidly,  it  lengthens  the  neck  and  stretches  out  the  head  to 
carry  the  centre  of  gravity  forwards.  But  when  it  rests  on  the  ground,  it  makes  the 
balancing-pole  assume  the  natural  and  more  or  less  graceful  inflection,  by  throwing  the 
head  backwards,  and  transferring  the  greater  portion  of  the  weight  of  its  body  to  the 
columns  of  support  formed  by  the  posterior  members.  These  displacements  of  tlie  centre 
of  gravity  are  executed  in  birds  on  a  more  extensive  scale  than  in  mammalia ;  the 
vertebral  stalk  in  the  former  is  also  longer,  lighter,  and  enjoys  an  excessive  mobility. 

The  vertebrae  composing  it  number  fourteen  in  fou-h,  twelve  in  the  pigeon,  fifteen  in 
the  diich,  and  eighteen  in  the  goose ,  in  the  swan  twenty-three  have  been  counted : — a 
curious  variety  wliich  singularly  contrasts  with  the  nimierical  unity  noticed  as  one  of 
the  most  remarkable  characters  in  mammalia !  These  vertebrae  are  generally  longer 
than  in  the  latter  class,  and  are  particularly  distinguished  by  the  configuration  of  the 


THE  BONES  IN  BIBDS. 


113 


articuiai-  surfaces  of  the  inferior  part  or  body.    These  are  diarthrodial  facets  convex  in 
oue  sense  and  concave  in  the  other,  articulating  the  vertebral  bodies  by  a  veritable  and 


Fig.  73. 


gKELETON   OF   A   FOWL, 

From  A  to  B,  Cervical  Vertebrs.— 1.  Spinous  process  of  the  third  vertebra  ;  2,  Inferior 
ridge  on  body  of  the  same  ;  3,  Styloid  prolongation  of  the  transverse  process  cf 


114  TSE  BONES. 

reciprooal  clampinf;:.  In  this  manner,  the  anterior  head  of  the  body  of  each  vertebra  is 
replaced  by  a  facet  concave  from  one  side  to  the  other,  and  convex  vertically  ;  while  the 
posterior  extremity  of  the  bone  bears,  instead  of  a  concavity,  a  facet  convex  in  the  lateral 
£e:ise,  and  concave  from  above  to  below.  The  inferior  crest  of  the  body  (fig.  73,  2,  2  ) 
only  exists  in  the  first  and  last  vertebrre,  but  it  forms  a  veritable  spine,  analogous  to 
that  observed  in  the  lumbar  vertebrsB  of  the  rabbit.  The  spinous  process  (tig.  73,  1,  1') 
only  forms  a  simple  crest  in  the  middle  part  of  the  neck ,  it  becomes  more  salient  in 
the  vertebrae  which  occupy  the  two  extremities  of  tliis  region.  The  transverse  process 
represents  on  the  side  of  the  vertebra  a  thick,  obtuse,  and  irregular  tubercle,  situated 
under  the  anterior  articular  process,  and  pierced  at  its  b.ise  by  a  large  vertebral  foramen 
(tio-.  73,  4,  4').  It  is  most  frequently  furnished  with  a  small  styloid  prolongation 
(fij;.  73,  3,  3')  directed  backwards  and  downwards,  forming  an  epiphysis  at  an  early 
period,  and  representing  a  real  undeveloped  rib. 

The  atlas  has  no  transverse  processes.  Tliis  vertebra  is  shaped  like  a  thin  ring, 
and  is  excavated  on  its  anterior  contour  by  a  small  cavity  into  which  is  received  the 
single  condyle  of  the  occipital  bone. 

Tiie  axis  shows  a  very  marked  odontoid  process  with  a  single  facet  under  that 
eminence. 

Dorsal  vertehrx  (Fig.  73.  B,  c). — These  are  seven  in  the  Fowl  and  Pigeon,  and  nine  in 
the  Goose  and  Ditck ,  they  are  marly  always  consolidated  into  a  single  piece  to  which  the 
trunk  is  fixed,  and  which  gives  the  wings  a  solid  support  in  the  violent  efforts  that  flight 
demands.  The  two  or  three  last  are  often  even  covered  by  the  wing-bones,  and  joined 
to  them.  The  inferior,  crest  of  the  body  forms  a  very  long  spine,  especially  in  the  first 
vertebrae.  Tne  spinous  processes,  flat,  wide,  short,  and  consolidated  with  each  other  by 
their  opposite  boniers,  constitute  a  long  crest  extending  fiom  the  last  cervical  vertebra  to 
the  bones  of  the  wings  (fig.  73,  7).  Tne  transverse  processes  widen  to  their  summit;  in 
the  fowl  they  are  nearly  constantly  fused  with  eacii  other. 

Lumbar  ami  sacral  vertehnv. — All  tliese  vertebrae  are  foi-med  exactly  on  the  same 
type;  so  that  it  becomes  ditticult,  if  not  impussible,  to  fix  tiie  point  where  the  lumbar 
region  ends  or  the  sacral  begins.  At  first  independent  of  each  other,  these  vertebrae, 
numbering  fourteen,  soon  become  consolidated  with  one  another  and  with  the  ribs ;  but 
their  primitive  separation  is  always  indicated  by  the  lateral  septa  wliich  form,  on  their 
inferior  face,  the  vestiges  of  the  transverse  processes.  Tiie  former  are  closely  united  to 
the  latter  in  the  dorsal  region. 

Coccygeal  vtrteJirse. — In  the  coccygeal  region,  the  spine  recovers  its  mobility.  The 
tail  of  the  bird,  indeed,  fulfils  the  office  of  a  rudJer  to  direct  it  during  flight;  and  it  is 
absolutely  necessary  that  the  vertebrae  which  serve  as  a  base  fur  the  steering  feathers 
should  preserve  their  independence,  so  as  to  allow  these  to  be  carried  to  the  right,  left, 
downwards,  or  upwards.  These  vertebrae,  teven  in  number,  present  spinous  processes 
which  are  often  bifurcated,  traiLsverse  processes  very  developed,  and  sometimes  even 
spines  more  or  less  long  on  the  inferior  surface  of  tlieir  bodies.  The  last  vertebra  is 
always  the  most  voluminous ;  it  is  flattened  on  both  sides,  and  terminates  in  a  curved-up 
point. 

Hkad  (Fig.  73,  p.  G.). — The  head  of  the  bird  is  small,  and  of  a  conical  form.  The 
anterior  extremity  is  elongated,  and  terminated  by  a  pointed  or  flattened  beak,  which 
allows  the  animal  to  cut  the  air  with  more  facility. 


the  same;  4,  Vertebral  foramen  of  the  same;  1',  2',  3',  4',  The  same  parts  in  the 
twelfth  vertebra. — From  B  to  C,  Dorsal  Vertebrce. — 6,  Spinous  processof  the  tirst ; 
7,  Crest  formed  by  the  union  of  the  other  spinous  processes. — From  d  to  e.  Coccy- 
geal Vertebrae. — f,  g.  Head. — 8,  Interorbital  septum  ;  9,  Foramen  of  communica- 
tion between  the  two  orbits;  10,  Premaxillary  bone ;  10',  External  openings  of 
the  nose;  11,  Maxilla;  12,  Square  bone;  13,  Jugal  bone. — H,  Sternum. — 14, 
Brisket  or  keel;  15,  Episternal  process;  16,  Internal  lateral  process;  17,  Lateral 
external  process;  18,  Membrane  which  closes  the  internal  notch;  19,  Membrane 
of  the  external  notch. — i,  etc.,  Superior  ribs. — 20,  Posterior  process  of  the 
fifth. — J,  Inferior  ribs;  K,  Scapula;  L,  Coracoid  bone;  M,  Furculum. — m,  m,  Its 
two  branches. — N,  Humerus  ;  O,  Ulna. — o,  Radius. — p,  v',  Bones  of  carpus ; 
Q,  q',  Bones  of  metacarpus;  R,  First  phalanx  of  the  large  digit  of  the  wing.— r. 
Second  phalanx  of  the  same. — r'.  Phalanx  of  thumb;  s,  Ilium;  s'.  Ischium;  s". 
Pubis. — 21,  Sciatic  foramen;  22,  Foramen  ovale. — T,  Femur;  u.  Patella;  V, 
Tibia ;  X,  Fibula. — y,  Single  bone  of  tarsus. — Y,  Jletatarsus. — 23,  Superior  process 
representing  a  united  uietatarsal  bone;  24,  Process  supporting  the  claw. — 
z,  etc.,  Digits. 


THE  BONES  IN  BIRDS.  115 

Bonfis  of  the  cranium. — The  bones  which  compose  the  cranium  are,  as  in  mnmmulia, 
an  occii>ital,  parietal,  frontal,  ethmoid,  sj)henoiii,  and  two  temporals.  The.se  bones  are 
net  isolated  from  each  other,  excepting  during  early  life  in  the  shell,  and  the  ossifying 
process  which  unites  them  is  so  rapid,  that  the  cranium,  shortly  after  hatching,  is 
alrea  iy  a  single  piece.  No  detailed  description  of  the  separate  bones  will  be  given  here, 
but  only  a  few  brief  observations  which  may  be  of  some  utility. 

Thus,  the  occipital  b(me  shows  for  articulation  with  the  spine  only  a  single  condyle, 
situated  under  the  occipital  foramen,  and  excavateil  by  a  slight  groove.  In  palmipedes, 
this  bone  is  pierced,  behind  the  crests  which  give  attachment  to  the  extensor  muscles, 
by  two  foramina  which  pt-mtrate  the  cranium,  and  represent  permanent  fontanella. 
The  parietal  bone  is  feebly  developed,  and  formed  from  only  two  primary  nuclei. 
The  frontal  is  the  largest  bone  of  the  cranium ;  its  orbital  process  is  supported 
by  a  particular  piece  which  is  generally  considered  as  belonging  to  tlie  large  wing 
of  the  sphenoid.  The  perjiendicular  lamina  of  the  ethmoid  is  considerable,  and 
forms  between  the  two  orbits  a  thin  vertical  septum  ( fig.  73,  8).  Its  posterior  border  is 
notehtd  opposite  to  the  optic  foramen,  and  thus  constitutes  an  opening  which  com- 
municates between  the  two  orbital  cavities  (fig.  73,  9).  It  is  also  channeled,  near  its 
upper  border,  by  a  fissure  which  terminates  by  two  openings  at  its  extremities,  one 
entering  the  cranium,  the  other  the  nasal  cavities.  This  fissure  and  these  foramina 
permit  the  passage  of  the  ethmoidal  nerve,  which  in  this  wiiy  traverses  tlie  orbit  before 
arriving  at  its  destination.  The  ethmoidal  cells  are  more  membranous  than  bony  ;  their 
base  is  attached  to  a  very  delicate  transverse  pLite,  which  is  often  mendoranous  and  not 
cribbled,  a:id  forms  part  of  the  anterior  orbital  wall.  These  cells  rejilae,  at  the  same 
time,  the  lateral  masses  of  the  ethmoid  and  turbinated  bones  of  mammalia.  The 
sphenoid  appears  to  be  formed  of  a  single  piece,  and  shows  on  its  sides  two  diarlhrodial 
facets  corresponding  to  the  pterygoids.  It  is  pierced  by  one  foramen  for  the  passage  of 
the  optic  nerves ;  but  this  foramen  opens  on  the  outer  and  opposite  side  of  the  posterior 
notch  of  the  interorbital  septum,  and  thus  allows  each  of  the  nerves  passing  through  it 
to  reach  the  eye  for  which  it  was  intended. 

It  is  worthy  of  remark,  thut  an  analogous  disposition  is  also  noticed  in  the  rabbit.' 
The  temporal  bones  present  at  their  base  an  articular  surface  corresponding  to  the  square 
bone.  In  the  fowl  species,  the  zj'gomatic  process  forms  a  small  flattened  tongue, 
directed  forwards,  sometimes  free,  and  at  other  times  united  by  its  superior  border 
to  the  summit  of  the  orbital  process.  These  two  eminences  are  exceedingly  short 
in  pigeons.  In  j;«i»itpef7es  they  are  consolidated  and  conlbunded  so  intimately,  that  it 
becomes  impossible  to  distingui.-h  them  from  one  another.  From  this  union  results  a 
long  and  strong  process,  which  inclines  forward  and  meets  a  particular  prolongation  of 
the  OS  unguis,  forming  with  it  areal  bony  arch.  This  arch  limits,  below  and  outwardly, 
the  orbital  cavity. 

Bones  of  the  face. — The  supermaxilla  c  mprises ;  a  premaxilla,  two  nasal,  two 
lachrymal,  two  palate,  two  pterygoid,  two  zygomatic  bones,  and  a  vomer.  The  inferior 
jaw  has  for  its  base  a  maxillary  bone,  which  articulates  with  the  cranium  by  means  of 
two  supplementary  pieces  named  the  square  bones.  The  premaxiUary  hone  is  found, 
before  hatching  is  completed,  of  two  lateral  pieces,  which  represent  the  two  small 
premaxillaries  of  mammals.  This  bone  is  very  considerable,  and  of  itself  forms  the  base 
of  the  upper  beak,  whose  form  it  determines ,  it  is  pointed  and  conical  in  the  gallinacea, 
and  wide  and  flattened  above  and  below  in  palmipedes.  In  front  it  circumscribes  the 
external  openings  of  the  nose,  and  is  prolonged  superiorly  into  two  lengthy  processes 
which  dovetail  between  the  nasal  bones.  Two  inferior  processes  belonging  idso  to  this 
bone  concur  in  the  formation  of  the  palatine  roof.  The  supermaxillaries,  analogues  of 
the  supermaxillaries  of  mammals,  are  two  rudimenlary  bones  situated  on  the  sides  and 
at  the  base  of  the  beak.  They  form  a  part  of  the  palatine  roof  and  the  walls  of  the 
nasal  cavities.  The  nasal  hones  circumscribe  above,  inwardly,  and  even  outwardly,  the 
external  orifices  of  these  civities.  The  palate  hones  encircle,  as  in  mammals,  the  guttural 
openings  of  the  nose,  and  constitute  in  great  part  the  roof  of  the  palate  ;  their  p(>sterior 
extremity  lies  against  the  pterygoids ;  the  anterior  joins  the  supermaxillaries  and  the 
inferior  process  of  the  premaxillary  bone.  The  pterygoids  extend  obliquely  from  the 
sphenoid  to  the  square  bones,  and  are  united  to  the  sphenoid  by  diarthrodial  articulation, 


'  This  analogy  is  really  striking,  and  might,  in  our  opinion,  serve  as  a  basis  for 
a  new  determination  of  the  interorbital  septum.  We  are  tempted,  indeed,  to  consider 
this  bony  lamina  as  the  inferior  sphenoid  and  the  middle  portion  of  the  ethmoid  of  birds. 
This  manner  of  viewing  it  tends  to  confirm  the  ideas  of  M.  Tabourin  on  the  inferior 
sphenoid  and  the  ethmoid  of  mammals. 


116  THE  BONES. 

The  zygomatic  hones  have  the  form  of  two  very  thin  stylets,  and  are  united  to  the  square 
bone  by  their  posterior,  and  consolidated  with  the  snpermaxillary  by  their  anterior 
extremity.     The  vomer  separates  the  guttural  openings  of  the  nose  from  one  another. 

Tlie  bones  of  the  upper  jaw  are  not  fused  with  eacii  other  so  rapidly  as  the  b(jne3  of 
the  cranium.  The  ascending  processes  of  the  premaxillary  and  nasal  bones  even  remain 
for  a  long  time  united  to  the  frontal  bone  by  a  simple  synarthrodia!  articulation.  This 
arrangement  allows  the  upper  beak  to  execute  a  certain  elevating  movement,  of  which 
we  will  speak  when  describing  the  articulations. 

The  inferior  maxillary  hone  is  originally  formed  of  a  great  number  of  distinct  seg- 
ments which  are  soon  united  into  a  solid  piece.  The  square,  petrous,  or  hone  of  the 
tympanum  ought  to  be  considered  as  detached  from  tlie  temporal.  It  is  prismatic  in 
shape,  and  provided  on  its  upper  surface  with  a  diarthrodial  facet  which  unites  it  to  the 
temporal,  and  on  its  lower  face  with  another  facet  articulating  with  the  branch  of  the 
maxilla.  Outwards  it  joins  the  zygomatic  bone,  and  inwards  with  the  pterygoid. 
Behind,  it  gives  attachment  to  the  membrane  of  the  tympanum;  and  in  front  it 
presents  a  small  eminence  of  insertion  which  Meckel  considered  a  second  zygomatic 
process. 

Thorax. — Sternum  (fig.  73,  h). — The  sternum  of  birds,  serving  as  a  basis  of  support  to 
the  muscles  moving  the  wings,  should  offer,  and  does  in  fact  show,  a  remarkable  degree 
of  strength,  because  of  the  extraordinary  volume  of  these  muscles.  And  these  being  more 
powerfid  and  energetic  as  the  bird  exhibits  a  greater  degree  of  aptitude  for  flight,  it  results 
that  the  structure  of  the  sternum  is  solid  in  proportion  as  the  bird  is  strong  on  the  wing. 
For  this  reason  we  may  infallibly  pronounce  as  to  the  extent  and  power  of  a  bird's  flight 
by  an  inspection  of  the  sternum  of  individuals  of  its  species.  In  this  respect,  however,  we 
only  announce  what  is  well  known  to  be  a  particular  application  of  the  rules  established 
by  the  great  law  of  concordance  between  the  anatomical  disposition  of  organs  and  their 
physiological  finality. 

Studied  in  Palmipedes,  which  will  serve  as  a  type  for  description,  the  sternum  presents 
itself  in  the  form  of  a  large  rectangular  cuirass,  elongate!  from  before  to  behind,  of  itself 
constituting  the  inferior  wall  of  the  thoracic  cavity,  and  also  largely  protecting  the 
abdominal  cavity.  Its  superior  face  is  concave,  wliile  the  inferior  is  convex,  and  entirely 
occupied  by  tlie  insertion  of  the  pectoral  muscles.  It  presents,  on  the  median  line,  a 
tliin  and  very  salient  ridge,  named  the  hrisket  (or  keel),  which  in  a  remarkable  manner 
multiplies  the  points  of  attachment  of  these  muscles.  The  anterior  border  offers  in  its 
middle  a  small  eminence  of  insertion,  the  episternal.  Laterally,  two  articular  grooves 
are  seen  which  correspond  to  the  coracoids.  The  posterior  border  is  cut  by  two  notches 
which  are  often  converted  into  foramina.  On  the  lateral  borders  are  observed  small 
double  articular  facets  answering  to  the  inferior  riba.  The  angles  which  separate  these 
two  borders  from  the  anterior  are  both  prolonged  into  a  little  eminence,  named  by  some 
authors  the  costal  process. 

In  the  Fowl,  the  sternum  is  not  so  strong  as  in  the  Goose  or  Duck.  On  each  side  of 
the  biisket  it  shows  two  wide  notches,  which  greatly  reduce  its  substance.  These 
notches,  closed  in  the  fresh  state  by  membranes,  are  distinguished  as  external  and 
internal.  The  latter,  of  greater  size  than  tlie  former,  extends  nearly  to  the  extremity  of 
the  bone.  From  this  division  of  the  lateral  plates  of  the  sternum  result  two  long  and 
slender  processes  directed  backwards.  The  external  terminates  by  becoming  widened, 
and  forming  a  kind  of  bony  plate,  whicli  covers  the  last  inferior  ribs. 

The  sternum  of  Pigeons  is  distinguished  by  the  enormous  development  of  the  brisket. 
The  two  notches  of  the  fowl  are  also"  met  with  in  these  birds,  but  the  internal  is  nearly 
always  converted  into  a  narrow  foramen. 

This  comparative  study  of  the  sternum  in  the  chief  domesticated  birds  leads  us  to 
appreciate  the  correctness  of  the  principles  just  enunciated,  with  regard  to  the  form  and 
extent  this  bone  may  exhibit.  The  Gallinaceous  Birds,  properly  so  called,  which  fly 
little  and  badly,  have  the  sternum  singularly  weakened  by  the  deep  notches  cut  in  its 
lateral  parts.  With  Palmipedes,  the  sternum  is  wide  and  but  slightly  notched,  so  that 
the  goose  and  duck,  which  waddle  along  so  awkwardly  in  our  poultry  yards,  are  capable 
of  sustaining  long  and  rapid  flight,  like  that  of  the  wild  individuals  of  the  same  species. 
With  regard  to  Pigeons,  which  are  well  known  to  be  swift  and  powerful  flyers,  may  this 
advantage  not  be  due  to  the  extraordinary  development  of  the  keel  which  constitutes  th€ 
brisket  ? 

Bibs. — In  the  Fowl  and  Pigeon  there  are  seven  pairs  of  ribs  ;  and  in  the  Buck  nine 
pairs.  Articulated  superiorly  with  the  dorsal  vertebrpe,  as  in  mammals,  these  bones  are 
provided  near  their  middle  with  a  flat  eminence  which  commences  at  the  posterior 
border,  and  is  directed  backwards  and  upwards  to  rest  liy  its  free  extremity  on  the 
external  face  of  the  next  rib.    These  eminences  (Fig.  73,  20)  form  an  epiphysis  at  an 


THE  BONES  IN  BIBDS.  117 

early  period,  and  are  usually  absent  in  the  first  and  last  ribs.      They  concur  in  an 
efficacious  manner  to  increase  the  solidity  of  the  thorax. 

The  costal  cartilages  in  mammalia  are  in  birds  often  transformed  into  veritable 
inferior  ribs,  joined  to  the  superior  ribs  by  a  diartbrodial  articulation  (Fig.  73,  i).  These 
pieces  are  long  and  strong,  and  all  ti^rminate  at  their  lower  extremity  by  a  double 
facet  -which  articulates  with  the  lateral  border  of  the  sternum;  they  are  nearly  always 
absent  in  the  two  first  ribs.  It  is  not  rare  to  see  the  last  united  to  the  one  before  it, 
instead  of  passing  directly  to  the  sternum;  in  which  case  it  comports  itself  like  the 
asternal  ribs  of  the  mammalia. 

Anterior  Members. — Shoulder-hone. — The  shoulder  comprises ;  a  scapula  ,  a  par- 
ticular bone  named  the  coracoid  by  Cuvier ;  and  a  clavicle,  which  forms,  in  coalescing 
with  that  of  the  opposite  side,  a  single  bone  called  the  fork  (fnrculum),  or  os  furculare. 
The  scapula  is  narrow,  elongated,  and  falciform,  and  shows  no  trace  of  a  spine.  Its 
anterior  extremity  only  forms  a  portion  of  the  glenoid  cavity,  and  is  united  by  means  of 
a  fibro-cartilage  with  the  fork  of  the  coracoid  bone.  The  latter  is  so  named  because  it 
represents  the  coracoid  process  of  mammals,  and  is  a  long  prismatic  bone,  directed 
obliquely  from  above  downwards,  and  before  to  behind.  Its  superior  extremity  is  often 
fused  with  the  scapula,  and  united  at  an  acute  angle  with  that  bone  to  form  a  portion  of 
the  articular  cavity  which  receives  the  head  of  the  humerus.  Its  inferior  extremity  is 
flattened  from  before  to  behind,  and  responds  by  a  diarthrodial  articulation  to  the 
anterior  border  of  the  sternum.  The  coracoid  is  long  in  birds  which  fly  slowly  ;  it  is,  on 
the  contrary,  short,  thick,  and  therefore  very  solid  in  quick  flyers.  The  fork  is  a  single 
bone,  shaped  like  a  V  or  U,  situated  at  the  base  of  the  two  wings,  in  front  of  the  trunk, 
and  in  an. oblique  direction  downwards  and  backwards.  The  two  branches  which  form 
it  represent  the  clavicles;  Ihey  meet  and  are  united  at  their  inferior  extremities,  where 
they  describe  a  curvilinear  angle  more  or  less  open,  attached  to  the  brisket  by  means  of 
a  membranous  ligament.  Their  superior  extremity  rests  within,  and  opposite  to  the 
glenoid  cavity,  against  the  scapula  and  coracoid,  forming  with  these  bones  a  remarkable 
foramen,  through  which  passes  the  tendon  of  the  elevator  muscle  of  the  wing  (Fig.  73, 
A,  4,  B,  6).  The  fork  plays  the  part  of  an  elastic  spring,  whose  office  it  is  to  prevent  the 
wings  coming  towards  each  other  during  contraction  of  the  depressor  muscles.  The 
conformation  of  this  bone  is,  therefore,  like  the  sternum,  related  to  the  extent  and  power  of 
flight ;  and  for  this  reason  it  is  that,  in  swift  flyers,  the  two  blanches  of  the  fuiculum  are 
thick,  solid,  widely  separated,  and  curved  like  a  U ;  while  in  those  which  fly  heavily  and 
with  difficulty,  these  branches  are  thin  and  weak,  and  joined  at  an  acute  angle.  The 
latter  formation  greatly  diminishes  its  strength,  and  lessens,  in  a  singular  manner, 
the  reactionary  power  of  the  bony  arch  it  represents. 

Bone  of  the  arm. — The  humerus  offers  an  articular  oval-shaped  head,  and  an  air- 
opening  placed  beneath  this  eminence.  It  is  long  in  Palmipedes,  ordinarily  so  in  the 
GaUinacx  proper,  and  very  short  in  Pigeons. 

Bones  of  the  fore-arm. — The  radius  is  much  less  volximinous  than  the  ulna.  The 
latter  has  an  extremely  short  olecranon  ;  and  the  two  bones  are  separated  from  one 
another  in  their  middle  part  to  meet  again  at  tlieir  extremities,  where  they  are  united 
by  ligamentous  bands  in  such  a  way  as  to  render  the  movements  of  pronation  and 
supination  impossible.  This  mode  of  fastening,  which  nevertheless  does  not  prevent  the  two 
bones  from  gliding  slightly  on  each  other  in  the  direction  of  their  length,  has  been  wisely 
adopted  by  nature  in  order  that  the  wing  might  strike  the  air,  like  an  oar,  by  its  inferior 
face  ;  otherwise,  the  resistance  of  the  aerial  medium  would  make  these  two  bones  pivot, 
and  cause  the  wing  to  present  itself  to  the  air  in  a  wrong  direction. 

Bones  of  the  carpus. — These  are  only  two,  and  are  distinguished  by  the  names  of 
radius  and  ulna,  in  consequence  of  their  corresponding  more  particularly  to  these  bones 
in  other  animals. 

Bones  of  the  metacarpus. — These  also  number  only  two,  and  are  separated  at  their 
middle  portion,  to  be  consolidated  at  their  extremities. 

Bones  of  the  digital  region. — The  wing  of  a  bird  is  composed  of  three  digits.  One 
of  them,  which  resembles  the  thumb  and  forms  the  basis  of  the  false  wing,  is  composed 
of  a  single  styloid-shaped  phalanx,  articulated  at  the  base  of  a  small  particular  process 
belonging  to  the  superior  extremity  of  tlie  largest  metacarpal  bone.  The  largest  digit 
comprises  two  phalanges  which  succeed  the  last  bone.  The  third  digit  is  represented  by 
a  small  rudimentary  phalanx,  which  corresponds  to  the  inferior  extremity  of  the  small 
metacarpal  bone,  and  lies  beside  the  first  phalanx  of  the  large  digit  in  the  closest  manner. 

It  is  well  to  remark  that  the  hand  and  the  fore-arm  are  longer  in  proportion  to  the 
quality  of  flight ;  those  two  regions  of  the  wing,  for  example,  are  very  short  in  Gallinaceous 
Birds. 

PosTERiOB  Members. — Coxa  or  os  iliac. — This  is  a  voluminous  and  very  solid  piece, 
11 


118  THE  BONES. 

particularly  in  vralking  birds,  and  composed,  as  in  the  mammalia,  of  an  ilium,  iscliium, 
and  pubis.  The  ilium  is  consolidated  with  the  last  dorsal,  the  lumbar,  and  thu  sacral 
vertebrae;  it  is  excavated  on  its  internal  face.  The  ischium  partly  incloses  the  side  of 
the  pelvic  cavity ;  between  its  internal  border  and  the  external  border  of  the  ilium  is  an 
orifice  which  replaces  the  great  i&chiatic  notch.  Its  Inferior  border  is  united  to  the  pubis. 
The  latter  is  thin  and  elongated,  and  follows  tlie  direction  of  the  inferior  border  of  the 
ischium,  with  it  circumscribing  an  ocal  openinq  more  or  less  spacious.  Its  inferior 
extremity  extends  beyond  tiie  ischium  to  curve  inwards  towards  that  of  the  opposite  .side, 
but  without  uniting  witii  it.  We  do  not,  therefore,  find  the  pelvic  symphysis  in  birds, 
and  the  pelvis  is  widely  open  below,  a  circumstance  which  iavours  the  passage  of  the 
egg  through  the  cavity  and  out  of  tlie  cloaca.  The  cotyloid  cavity  is  perforated  by  an 
opening  at  the  bottom  which  traverses  tlie  bone. 

Thigh  hone. — The  femur  is  articulated  inferiorly  with  the  patella,  tibia,  and  fibula.  In 
all  walking  birds,  like  the  galiinacae,  it  is  long  and  strong,  as  well  as  the  rays  "below  it. 

Leg  hones. — The  patella  is  wide  auii  thin.  The  tibia  terminates,  below,  by  two  con- 
dyles separated  by  a  groove  which  becomes  articular  behind.  The  fibula  articulates 
by  its  head  with  the  external  condyle  of  the  femur,  and  is  consolidated  with  the  tibia ; 
it  never  descends  to  the  inferior  extremity  of  that  bone. 

Tarsal  hones. — The  tarsus  appears  to  be  altogether  absent  in  birds.  Nevertheless 
we  may  venture  to  consider,  as  a  vestige  of  the  bones  of  this  region,  a  small  bony  nucleus 
buried  in  a  fibrocartilaginous  mass  which  glides  on  the  posterior  pulley  of  the  tibia. 
This  nucleus  represents  the  calcaneus  of  mammals. 

Metatarsal  bone.— A.  single  metatarsal  bone  is  found  in  birds,  articulating  superiorly 
with  the  inferior  extremity  of  the  tibia,  and  terminating  inferiorly  by  three  pulleys 
which  support  the  three  principal  digits.  This  bone  shows  in  the  Fowl,  near  its  inferior 
third,  a  conical  process  turned  backwards,  which  serves  as  a  base  for  the  spur.  Behind 
its  superior  extremity,  it  exhibits  another  which  may  be  considered  as  a  consolidated 
metatarsal  bone. 

Bones  of  the  digital  region. — All  the  domesticated  birds  have  four  digits  on  the  inferior 
members :  three  principal,  directed  forwards,  and  one  rudimentary,  carried  backwards. 
The  first,  designated  as  internal,  median,  and  external,  articulate  with  the  inferior 
pulleys  of  the  metatarsal  bones.  The  internal  is  formed  by  three  phalanges,  the  second 
has  four,  and  the  tlurd  five.  These  phalan2;es  are  formed  something  like  those  of  the 
cariiivora :  the  last  is  pointed,  conical,  and  enveloped  in  a  horny  slieath.  The  fourth 
digit,  or  thumb,  is  composed  of  three  pieces :  one  of  these,  the  fir:^t,  is  generally  con- 
sidered as  a  rudimentary  metatarsal  bone.  It  is  attached  by  fibro-cartilaginous  tissue 
to  the  inner  and  posterior  aspect  of  the  inferior  extremity  of  the  principal  metatarsal 
bone. 


CHAPTER  IV. 

THEORY  OF  THE  VERTEBRAL  CONSTITUTION  OF  THE  SKELETON. 

In  the  series  of  vertebrated  animals  tlie  bony  pieces  of  the  trunk  bearing 
the  name  of  vertebras  are  those  which  offer  the  highest  degree  of  fixity,  and 
io  which  the  existence  or  the  arrangement  of  the  others  appears  to  be  subor- 
-dinate.  This  feature  in  organisation,  recognised  by  E.  Geoffroy  Saint- 
Hilaire  and  Professor  Owen,  has  caused  these  men  of  science  to  assert  that 
the  type  of  construction  of  vertebrated  animals  is  the  vertebra. 

After  E.  Geoffroy  Saint-Hilaire  and  Professor  Owen,  several  German, 
English,  and  French  anatomists  have  studied  the  vertebral  composition  of 
the  skeleton ;  and  among  the  works  published  in  France  on  this  subject  must 
be  specially  noticed  those  of  M.  Lavocat.^  In  principle,  all  the  writers 
have  arrived  at  the  same  conclusions,  and  only  difter  in  some  few  details. 

It  is  certain  that  the  base  of  the  vertebral  column  is  formed  by  a  series 
of  bony  segments.  Each  of  these  segments  is  called  an  osteodesm,  and  each 
osteodesm  represents  the  body  or  centrum  of  a  vertebra. 

('  The  distinguished  anatomist  and  Director  of  the  Imperial  Veterinary  School  of 
ToulousB.J 


THE  VERTEBRAL  CONSTITUTION  OF  THE  SKELETON.  119 

In  examining  the  dorsal  region,  it  is  evident  that  to  the  body  or  centrum 
of  a  vertebra  are  added  two  complete  osseous  arches,  a  superior  and  an 
inferior.  The  superior  arch  is  formed  by  the  vertebral  lamina ;  the  inferior 
by  the  ribs,  the  cartilages,  and  a  portion  of  the  sternum.  The  tu'st  is  desig- 
nated the  neural  arch,  because  it  furnishes  a  protecting  sheath  for  the 
nervous  centres ;  and  the  second,  which  more  particularly  protects  the 
vascular  system,  is  called  the  hcemal  arch  (see  Fig.  10). 

The  haemal  arch  may  have  prolongations  or  appendices  more  or  less 
developed,  and  comparable  to  the  apophysary  jirolongations  of  the  ribs  in 
birds  and  some  fishes. 

Such  is  the  general  composition  of  a  typical  vertebra ;  but  there  are 
also  to  be  distinguished  in  the  neural  and  htemal  arches  the  following 
parts : — 

NEVRAL    ARCH.  '  H^MAL    ARCH. 

1.  Xeiiral     parapophysis  =  the     posterior       1.  Hremal   parapoplnsis  =  the   tuberosity 

costal  cupola.  of  the  rib. 

2.  Neural    metapophysis  =  the    anterior      2.  Ha?mal  metapophysis  =  the  head  of  the 

costal  cupola.  rib. 

3.  Neural  diapophysis  =  the  summit  of  the   [    3.  Hsemal  diapopliysis  =  the  rib  proper. 

transver.-e  process.  4.  Heumapophysis  =  the  costal  cartilage. 

4.  Neurapophysis  =  the  vertebral  lamina.     '    5.  Hsemal      spine   =  the      corresponding 

5.  Neural     spine  =  the     summit    of    tiiC  sternal  portion. 

spinous  process.  ; 

The  vertebras  sometimes  depart  more  or  less  from  the  model  just 
described.  They  may  vary  not  only  from  one  species  to  another,  but  also 
in  the  same  animal,  and  even  in  the  same  region.  Thus  the  neural  arch 
may  be  absent,  as  has  been  observed  in  certain  coccygeal  vertebrae ;  or  the 
haemal  arch  is  incomplete  or  null,  as  in  the  cervical  or  lumbar  vertebrte ;  or, 
lastly,  the  arches  are  often  unequal ;  though  this  inequality  is  of  no  import- 
ance, since  their  size  is  in  relation  to  the  volume  of  the  pai'ts  they  should 
protect. 

Notwitstanding  these  differences  and  variations,  or  the  transformations 
experienced  by  certain  parts,  there  is  not  a  bone  in  the  skeleton  which  can- 
not be  included  in  the  vertebral  type 

The  vertebra  being  admitted  as  the  type  of  construction  of  the  skeleton, 
it  is  easy  to  find  it  in  all  the  regions  of  the  bony  framework.  In  the 
thoraco-abdominal  region,  the  centrum,  neural  arch,  and  hfemal  arch  are 
readily  perceived  ;  in  the  lumbar  vertebrae,  the  enormously  developed  trans- 
verse process  indicates  the  existence  of  an  infravertebral  arch. 

In  the  sacral  region,  the  bony  girdle  of  the  pelvis  represents  the  hfemal 
arch.  The  posterior  limbs,  articulating  with  the  bones  of  the  pelvis,  belong 
to  the  haemal  arch,  and  should  be  considered  as  appendices  of  this  arch, 
analogous  to  the  costal  ajipendices  of  birds. 

The  cervical  region  may  be  compared  to  the  sacral  region ,  as  in  it  the 
inferior  haemal  arch  is  represented  by  the  osseous  ring  supporting  the 
anterior  limbs — the  scapnlo-clavicular  cincture.  The  limbs  themselves  are 
appendices  of  the  cervical  hsemal  arch. 

Difliculties  begin  to  appear  when  the  extremities  of  the  trunk — the  head 
and  coccyx — come  to  be  examined.  Nevertheless,  the  composition  of  the 
coccyx  is  revealed  when  the  caudal  vertebrae  of  certain  fishes,  especially 
those  of  the  pleuronectidae,  in  which  the  neural  and  haemal  arches  are  com 
plete,  are  examined.  But  the  vertebral  constitution  of  the  head  remained 
for  a   long  time  an  insoluble  question,  or  was  solved  in   a  contradictory 


120 


TEE  BONES. 


manner  by  the  naturalists  who  attempted  it.  Some  admitted  a  single 
cei^lialic  vertebra;  others  admitted  three  or  four;  while  others  again  arrived 
at  six  or  seven. 

These  difficulties  and  contradictory  results  may  be  understood,  when  it  is 


.  a 

P     o 


PL,  tH 


<    -° 


borne   in  mind  what  profound  modifications  the  vertebrge  must  have  ex- 
perienced to  constitute  the  bones  of  the  head  ♦ 

At  present  the  problem  appears  solved.  The  head  is  composed  of  four 
vertebras,  in  which  are  found  the  various  parts  enumerated  in  the  description^ 
of  the  typical  vertebra. 


TEE  VERTEBRAL  CONSTITUTION  OF  THE  SKELETON. 


121 


In  the  four  classes  of  vertebrata,  the  head  is  constantly  formed  of  four 
vertebrae,  which  ai'e  determined  as  follows :"  * 


VERTEBRJi.                      CENTRUM.         i           NEURAL  ARCH.                 H.EMAL  ARCH. 

Oecipito-hyoide;il.          Basilar    process  ;  Occipital  (3  pieces).        !  Hyoideal   appa- 
1     of  the  Uccipi-      Mastoid    walls   of  the  |     ratus (5 pieces). 
I     tal.                            Tympanum.                   i 

Parieto-maxillary. 

Body  of  the  pos-  i  Wing    and    pterygoid 
teiior       Sphe-  i     process    of   the    pos 
noid.                    i     terior  Sphfenoid. 

Squamous  portion  and 
zygomatic   process  of 
1    the  Temporal. 
Parietal. 

Inferior  IM axilla 
5  pieces). 

Fronto-mandibular. 

Body      of     the     Wing    and    pterygoid      Jugal. 
Anterior  Sphe-        process  of  the  anterior      Lachrymal, 
noid.                        Sphenoid.                         Palatine. 

]  Posterior  Frontal   and  ,  Supenuaxillary. 

its  orbital  process.         i  Premaxillarv. 
:  Frontal.                            { 

1 
Naso-turbiuaL                 Vomer,                     Ethmoid.                          1  Turbinated 

Nasal.                              1  SubetLimoidal. 

The  number  of  cephalic  vertebrte  is  invariable,  as  each  is  destined  to 
lodge  the  organs  of  one  of  the  four  senses.  The  occipito-hyoideal  lodges  the 
principal  organs  of  hearing ;  the  parieto-maxillary  osteodesm  protects  the 
sense  of  taste ;  finally,  the  organs  of  vision  are  sustained  by  the  fronto-man- 
dibular vertebra,  while  the  naso-turbinal  contains  the  sense  of  smell. 

It  was  therefore  with  reason  that  GeofFroy  Saiut-Hilaire  and  Professor 
Owen  proclaimed  that  the  type  of  construction  of  the  vertebrated  animals  is 
the  vertebra- 


SECOND    SECTIOK 
The  Articulations. 


CHAPTER  I. 

THE   ARTICULATIONS    IN   GENERAL. 

The  different  pieces  constituting  the  solid  framework  of  the  animal  body 
are,  as  has  been  said,  united  in  such  a  manner  that  they  can  move  one  upon 
the  other  From  this  union  results  the  articulations  or  articular  joints,  whose 
construction  will  now  be  referred  to  in  a  general  manner,  before  commencing 
a  particular  description  of  each 

To  form  articulations,  the  bones  correspond  to  each   other  by  certain 
points  of  their  periphery,  which  are  named  articular  surfaces.     Every  articu- 

'  Lavocat^ '  Nouvelles  e'tudes  sur  le  systeme  verte'bral,'  1S60. 


122 


THE  ABTICULATIONS. 


lation  IS,  therefore,  essentially  constituted  by  two  opposite  osseous  surfaces, 
which  are  moulded  to  each  other.  These  are  either  contiguous,  independent, 
and  very  movable — continuous  with  each  other  by  means  of  a  cartilaginous 
substance  which  condemns  them,  if  not  to  total  immobility,  at  least  to  very 


Yis- 


PLANS   OP    THE    DIFFERENT    GLASSES    OF    ARTICULATIONS. 

A,  Suture. — 1,  Periosteum;  2,  Sutural  ligament. — B,  Amphiarthrosis ;  a.  First 
degree. — 1,  Periosteum  ;  2,  Articular  cartilage  ;  3,  Interarticular  ligament. — 6, 
Second  degree  ;  4,  Single  cavity  in  the  interarticular  ligament. — c,  Tliird  degree  ; 
5,  Double  cavity  in  the  interarticular  ligament. — C,  Diarthrosis  ;  6,  Simple 
diartlirosis. — 1,  Periosteum;  2,  Articular  cartilage;  3,  Epithelial  layer  of  the 
synovial  membrane — dotted  line;  4.  P^ibrous  capsule;  5,  Cul-de-sac  of  the  syno- 
vial membrane  ;  6,  Fibrous  layer  of  the  synovial  membrane. — c,  Double  diarthrosis  ; 
7,  Interarticular  meniscus  ;  8,  9,  Cavities  of  the  two  synovial  membranes. 

limited  movements  :  or  united  by  a  fibro-cartilage  whose  elasticity  permits  a 
certain  degree  of  displacement  between  the  bnnes  wliich  are  in  contact. 

In  the  first  case,  the  articulations  are  classed  as  diarihroses,  or  movable 
articulations. 

In  the  second,  they  are  designated  synarthroses,  sutures,  or  immovable 
articulations. 


THE  ARTICULATIONS  IN  GENERAL.  123 

In  the  third,  they  are  amphiarthroses,  or  mixed  articulations ;  so  termed 
because  they  participate  in  the  movements  of  the  other  two  classes  ;  synar- 
throses, by  the  continuity  established  between  the  articular  surfaces ,  and 
diarthroses,  by  the  extensive  motion  they  j^ermit. 

The  general  characters  that  distinguish  each  of  these  three  great  classes 
of  articulations  will  be  successively  studied. 

(The  study  of  the  articulations,  or  rather  of  the  ligaments,  is  termed 
syndesmology — from  avv,  together,  and  Secr/Aos,  bond  ;  or  arthrology — from 
apdpov,  a  joint,  and  Xdyos,  a  description.) 

GENERAL    CHARACTERS  OF  DIARTHROSES. 

We  ought  to  consider  in  the  diarthrodial  articulations :  1,  The  con 
tiguous  bony  surfaces  which  form  them  ;  2,  The  cartilaginous  layer  {cartilages 
of  incrustation)  which  cover  these  ;  3,  The  fibro-cartilaginous  tissue  (articular 
Jibro-cariilages)  which  complete  them,  when  they  are  not  shaped  so  as  to  be 
reciprocally  adapted  to  each  other  ;  4,  The  ligaments  which  maintain  tbem 
in  contact ;  5,  The  serous  membranes  (synovial  capsules)  that  cover  the 
internal  face  of  the  latter,  and  which  secrete  the  synovia,  a  kind  of  animal 
oil  that  facilitates  the  gliding  of  the  articular  surfaces;  6,  The  movements 
of  which  these  articulations  may  be  the  seat ;  7,  Their  methodical  classifica- 
tion ;  8,  Their  nomenclature. 

Articular  Surfaces. — These  surfaces  have  the  common  character  of 
being  destitute  of  asperities,  so  that  they  can  glide  with  the  greatest  facility 
on  each  other.  They  are  designated,  according  to  their  form,  by  the  names 
of  facets,  heads,  condyles,  cotyles,  glenes,  p>^dleys,  etc.  There  is  no  need  to 
revert  to  their  general  description,  as  they  have  already  been  sufficiently 
studied  in  the  osteology;  so  we  will  confine  ourselves  to  repeating  that 
they  are  found  at  the  extremities  of  long  bones,  on  the  faces  of  short  bones, 
and  on  the  angles  of  ^vide  bones.  We  may  mention  also  that  they  are  often 
excavated  by  one  or  several  hollows  named  synovial  fossce,  a  sort  of  natural 
reservoirs  which  receive  the  unctuous  fluid  secreted  by  the  interarticular 
serous  membranes 

Cartilages  of  Incrustation. — This  designation  is  given  to  the  layers  of 
cartilaginous  matter  which,  as  it  were,  varnish  the  articular  surfaces  they 
adhere  to  by  their  inner  face;  their  free  surface  is  distinguished  by  a 
remarkable  polish  and  brilliancy  Thicker  towards  the  centre  than  at  the 
circumference  when  they  cover  bony  eminences,  these  cartilages  show  an 
inverse  disposition  when  they  line  cavities  They  are  elastic,  of  a  pearly 
whiteness,  and  resisting,  though  they  are  soft  enough  to  be  cut  by  a  sharp 
instrimient ;  in  a  word,  they  possess  all  the  physical  characteristics  of  the 
primary  cartilage  of  bones  They  appear  to  be  formed  of  parallel  fibres 
placed  perpendicular  to  the  bony  surfaces,  and  implanted  ii^  these  by  one  of 
their  extremities  :  the  opposite  extremity  corresponding  to  the  free  surface 
of  the  cartilage.  Viewed  by  the  microscope,  they  are  found  to  consist  of  a 
fundamental  substance  excavated  by  small  cavities  The  cartilage  of 
incrustation  therefore  belongs  to  the  group  of  true  or  hyaline  cartilages. 

The  fundamental  matter  is  amorphous  and  homogeneous,  and  more  or 
less  transparent,  according  to  its  thicloiess.  It  is  transformed  into  chondrine 
by  boiling  in  water. 

The  cavities  are  irregular,  and  more  or  less  wide.  They  contain  from 
one  to  five  cells  whose  walls  are  very  thin,  and  their  contents  slightly  gran^ 
ular;   in  the  centre  of  each  cell  is  a  nucleus  with  a  nucleolus.     These 


124 


TEE  ARTICULATIONS. 


Fi2.  76. 


cavities  are  elongated  and  directed  almost  perpendicularly  towards  tlie 
articular  surface  in  the  deep  layer ,  in  the  middle  layer  they  are  oblique, 
and  are  parallel  to  the  surface  of  friction  in  the  superficial  layer. 

(Under  a  high  magnifying  power 
the  fundamental  substance,  or  matrix, 
loses  its  homogeneous  and  amorphous 
character,  and  appears  to  be  granular 
or  faintly  striated.  In  the  midst  of 
this  granular  matrix,  the  lacun89  or 
cavities  are  observed  to  contain  from 
one  to  six  different-sized  cells.  It 
has  been  stated  that  a  membrane  lines 
these  spaces.  In  addition  to  the 
granular  matter  observed  in  the  cells, 
it  is  not  rare  to  find  fat  globules. 
The  nuclei  of  the  cells  vary  from 
to 


^^QQ  of  an  inch  in  diameter. 


SECTION    OF    BRANCHIAL   CARTILAGE    OF 
TADPOLE. 

a,  Group  of  four  cells  separating  from  each 
other  ;  6,  Pair  of  cells  in  apposition ;  c,  c, 
Nuclei  of  cartilage-cells ;  d.  Cavity  con- 
taining three  cells.  These  cells  are  im- 
bedded in  the  finely-granular  matrix,  or 
fundamental  substance. 


4000  

The  cells  multiply  endogenously.) 

Tlie  cartilage  cells  are  insoluble 
in  boiling  water ;  consequently,  so  far 
as  their  chemical  composition  is  con- 
cerned, they  are  distinct  from  the 
fundamental  substance. 

The  diarthrodial  cartilages  receive 
neither  vessels  nor  nerves.  The 
presence  of  cartilages  of  incrustation  in  the  articulations  is  of  the  greatest 
importance.  When  they  are  worn,  absorbed,  or  transformed  into  bone  in 
consequence  of  certain  articular  maladies,  the  movements  become  painful  and 
very  difficult.  With  regard  to  the  part  they  play  in  the  economy,  it  may 
be  said  that"  1,  They  favour,  by  their  smoothness,  the  gliding  and  displace- 
ment of  the  bones ,  2,  They  attenuate,  by  their  suppleness  and  elasticity, 
the  violent  shocks  to  which  the  articulations  are  exposed ;  3,  They  resist  the 
wear  and  deformation  of  the  articular  surfaces. 

Complementary  Fibro-cartilages. — There  are  several  kinds  of  com- 
plementary fibro -cartilages  : — Some  (interosseous)  represent  circular  cushions 
which  bolster  the  margins  of  certain  cavities,  filling  up  the  notches  which 
might  render  them  imperfect.     They  increase  the  depth  of  these  cavities 

Fig.  77. 


FIBRO-CARTILAGE ;  MAGNIFIED  155  TIMES.     Showing  interlacement  of  fibrous 
fasciculi,  with  scattered  groups  of  cartilage-cells. 

and    protect   their  borders  from   injury.     Others  (inter articular)  are  inter- 
posed between  articulaz'  surfaces  when  these  do  not  exactly  fit  each  other,  as 


TEE  ARTICULATIONS  IN  GENERAL 


125 


when  two  opposing  extremities  are  convex.  It  may  be  remembered  that  the 
lateral  tuberosities  of  each  tibial  surface  present,  for  articulation  with  the 
condyles  of  the  femur,  two  convex  diarthrodial  faces  whose  coaptation  is 
rendered  perfect  by  the  interposition  between  each  condyle  and  correspond- 
ing tibial  surface  of  a  crescent-shaped  fibro-cartilage,  which  for  this  reason 
has  been  named  a  meniscus.  In  other  joints  these  interarticular  fibro- 
cartilages  are  shaped  like  discs  or  biconcave  lenses.  There  then  result 
double  diarthroses  : — example,  the  temporo-maxillary  articulation.  (Fibro- 
cartilage  also  covers  bony  surfaces  over  which  tendons  play,  as  on  the 
trochlear  surface  of  the  humerus,  postero-inferior  face  of  the  navicular  bone, 
and  elsewhere.  In  these  situations  it  is  named  stratiform  fibro-cartilage.^ 
These  organs  are  formed,  as  their  name  indicates,  by  fibrous  and  car- 
tilaginous tissue ;  their  mode  of  association  need  not  be  referred  to  here, 
though  it  may  be  observed  that  the  cartilage  is  more  particularly  found  in 
all  those  points  where  there  is  most  articular  friction.  They  receive  vessels, 
and  sometimes  nerves. 

Ligaments. — These  are  bands  which  unite  contiguous  diarthrodial 
surfaces.  They  are  sometimes  formed  of  white  fibrous  tissue,  and  some- 
times of  yellow ;  from  whence  their  division  into  two  great  classes  of  white 
and   yellow   ligaments. 

a.  The  white  ligaments  are  distinguished  by  the  pearly  whiteness  of 
their  tissue  and  want  of  elasticity.     Those  which  are  found  on  the  outer 


Fiff  78 


Fig  79. 


I^^     '' 

.,  ^  .  ^  '1 

1^ 

t«. 

WHITE   OR   NON-ELASTIC   FIBROUS 

TISSUE, 


YELLOW   OR   ELASTIC   FIBROUS   TISSUE,   FROM 
THE   LIGAMENTUM   NUCH^. 


aspect  of  the  articulations  are  termed  peripheral,  and  those  in  their  interior 
are  designated  interosseous  or  interarticular  ligaments. 

The  peripheral  ligaments  are  generally  composed  of  parallel  fibres 
collected  in  fasciculi,  or  spread  out  as  membranes.  In  the  first  they  are 
called  funicular,  or  ribbon-shaped ;  in  the  second,  they  are  termed  mem- 
hraniform,  or  capsular.  The  funicular  ligaments  constitute  short,  round,  or 
flattened  bands,  attached  by  their  extremities  to  the  two  bones  they  unite ; 
they  are  lined  on  their  inner  aspect  by  the  synovial  capsule,  and  covered 
externally  by  tendons,  aponeuroses,  muscles,  vessels,  or  nerves.  The 
capsular  ligaments  are  often  complete — that  is  to  say,  they  envelope  the 
whole  articulation  like  a  sack.     At  other  times  they  are  incomplete,  and 


126  TEE  ARTICULATIONS. 

then  they  are  simple  membranes,  binding  together  the  different  funicular 
bands  of  a  joint. 

The  interosseous  ligaments,  less  numerous  than  the  preceding,  are  often 
formed  of  interlacing  fibres ;  they  are  always  funicular,  and  fixed  by  their 
extremities  into  excavations  in  the  centre  of  articular  surfaces. 

h.  The  yellow  ligaments  arc  all  peripheral,  funicular,  or  membranous,  and 
enjoy  a  marked  degree  of  elasticity,  which  permits  them  mechanically  to 
bring  back  to  their  usual  position  the  bony  levers  which  have  been  momen- 
tarily displaced.  These  ligaments,  which  are  powerful  auxiliaries  to  the 
muscular  forces,  are  destined  to  give  equilibrium  in  a  permanent  manner  to 
the  weight  of  certain  parts  of  the  body  which  incessantly  tend  to  fall  to  the 
ground. 

Synovial.  Capsules. — These  are  very  thin  membranes  of  a  serous  nature, 
intended  to  secrete  the  synovia.  They  are  composed  of  two  layers  :  a  deep, 
formed  by  fasciculi  of  the  connective  tissue ;  the  other,  superficial,  is  of 
an  epithelial  character.  The  first  sometimes  adheres  intimately  to  the  inner 
face  of  the  funicular  or  membranous  ligaments  of  the  articulation  ;  at  other 
times  it  is  loosely  attached  to  them  by  an  abundance  of  connective  tissue. 
The  second  layer  is  constituted  by  a  single  row  of  flattened  polygonal  cells. 

It  is  generally  admitted  that  the  synovial  membranes  comport  themselves 
like  the  other  serous  membranes,  by  forming  sacs  which  are  everywhere 
closed.  According  to  this  admission,  a  synovial  membrane,  after  covering 
the  internal  face  of  the  peripheral  ligaments  of  a  diarthrodial  articulation, 
ought  to  be  prolonged  on  the  free  surface  of  the  cartilages  of  incrustation, 
and  should  give  them  their  brilliancy  and  polish.  But  it  is  necessary  to 
state  that  this  is  a  pure  hypothesis,  against  which  rises  a  multitude  of  care- 
fully-observed facts.  The  discussion  of  these  belongs  to  general  anatomy, 
but  they  will  be  referred  to  here  as  briefly  as  possible. 

1.  If  direct  observation  be  consulted,  it  gives  on  this  debated  subject 
the  most  precise  information ;  the  cartilages  are  uncovered,  and  there  is 
no  synovial  membrane  on  their  face.  The  anatomists  who  have  mistaken  for 
this  membrane  the  thin  pellicle  which  it  is  possible  to  render  evident  on  the 
cartilages  in  obliquely  cutting  their  substance  and  separating  morsels  by 
tearing  it  off,  were  evidently  deceived.  This  pellicle  has  nothing  of  a  serous 
nature  in  its  texture ;  it  is  not  vascular,  for  it  has  never  been  possible  to 
inject  vessels  on  the  surface  of  cartilages,  nor  yet  in  their  thickness ;  it  is 
not  covered  by  epithelium ;  and  submitted  to  microscopical  examination,  it 
exhibits  -all  the  characters  of  the  amorjihous  matter  of  cartilage.  It  ought, 
then,  to  be  considered  as  a  cartilaginous  pellicle,  detached  from  the  super- 
ficial layers  of  the  articular  surface — a  pellicle  which  it  has  always  been 
impossible  to  find  on  cartilages  which  are  quite  fresh ;  and  it  has  never 
been  possible  to  observe  it  without  giving,  by  a  preliminary  desiccation,  a 
certain  degree  of  tenacity  to  the  cartilaginous  substance  about  to  be 
examined. 

2.  Pathological  facts  prove  nothing  in  favour  of  the  existence  of  a 
synovial  membrane  on  the  cartilages.  Hypertrophy  of  this  pretended 
membrane  has  never  been  witnessed  ;  the  fungosities  looked  upon  as  a  result  of 
this  hypertrophy  are  derived  from  another  source.  It  has  been  demonstrated 
that  they  extend,  in  certain  cases,  from  the  articular  margins  of  the  cartila- 
ginous surface,  whence  their  successive  invasions  may  often  be  followed.  In 
other  cases,  the  vegetating  membrane  which  constitutes  them  appears  in  the 
centre  of  the  articular  surfaces,  at  points  deprived  of  cartilage ;  they  after- 
wards extend  to  a  certain  distance  on  the  remaining  cartilage. 


THE  ARTICULATIONS  IN  GENERAL.  127 

3.  It  may  be  asked  of  the  partisans  of  the  opinion  now  combated,  how 
they  can  believe  in  the  existence  of  a  serous  membrane  between  two 
articular  surfaces,  without  its  being  exposed  to  bruises  and  destruction  a 
thousand  times  in  the  day?  Do  they  take  into  account  tbe  amount  of 
pressure  sustained  by  certain  articulations,  and  the  intense  friction  to  which 
their  surfaces  are  submitted  ?  Have  they  compared  the  intensity  of  these 
destructive  influences,  with  the  delicate  texture  of  the  serous  membranes, 
and  their  great  inflammatory  susceptibility  ?  It  is  sufficient  to  lightly  touch 
in  this  way  the  weak  side  of  our  adversaries'  argument,  and  to  conclude  the 
third  portion  of  this  discussion :  There  is  friction  between  the  cartilages 
of  the  two  opposed  articular  surfaces,  therefore  there  must  be  wear ,  this  is 
a  physical  law  which  no  body  escapes,  let  it  be  as  hard  as  the  diamond,  or  as 
soft  as  caoutchouc.  And  if  there  is  wear  between  these  rubbing  surfaces, 
there  cannot  be  an  irritable  and  sensitive  membrane  lying  on  the  inert  and 
insensible  strata  which  constitute  them.  In  fine,  a  synovial  membrane, 
after  being  fixed  to  the  margin  of  the  articular  cartilage  of  a  diarthrodial 
joint,  is  reflected  in  every  direction  to  cover  the  inner  aspect  of  the  liga- 
ments, and  becomes  attached  to  the  periphery  of  the  diarthrodial  surface 
corresponding  to  the  first. 

There  are  generally  found  within  articulations  little  masses  of  fat  which 
push  the  synovial  membrane  enveloping  them  inwards.  Erroneously  con- 
sidered by  Clopton  Havers  as  glands  for  the  secretion  of  synovia,  tliese 
accumulations  of  fat  have  been  named  synovial  fringes.  They  are  more  par- 
ticularly numerous  in  the  neighbourhood  of  the  articular  margins :  that  is, 
on  the  edges  of  diarthrodial  surfaces. 

The  synovia  is  a  viscid,  colourless,  or  slightly  yellow  fluid,  in  its  physical 
characters  somewhat  resembling  oil ;  it  does  not  possess  them,  however, 
so  far  as  its  composition  is  concerned,  for  chemical  analysis  has  not 
demonstrated  the  presence  of  fatty  principles.  It  is  the  albumen  it  contains 
which  gives  it  its  viscidity,  and  which  fits  it  for  lubricating  the  articular 
surfaces  over  which  it  is  spread.  Its  use  in  the  animal  economy  is 
absolutely  identical  with  that  of  the  greasy  substances  employed  to  lubricate 
the  axles  of  carriages. 

MovEiMENTS. — The  movements  peculiar  to  diarthrodial  articulations  are 
divided  into  seven  principal  classes  : 

1.  Simple  gliding,  the  only  movement  possible  between  two  plane  or 

undulating  facets. 

2.  Flexion,  which  brings  two  bony  pieces  nearer  each  other  by  closing 

more  or  less  their  angle  of  union. 

3.  Extension,   the   inverse    movement,   during   which   the   bones    are 

straightened  on  each  other. 

4.  Adduction,  which  brings  the  inferior  extremity  of  the  movable  bone 

towards  the  median  line. 

5  Abduction,  the  contrary  movement  to  the  preceding 

6  Circumduction,  or  the  sling  movement,  during  which  the  bone  passes 

successively  through  the  last  four  positions 
7,  Rotation,  in  which  one  bone  pivots  on  another 

Classification  of  the  Diarthroses. — The  basis  of  this  classification  is 
founded  on  the  configuration  of  the  articular  surfaces  and  tlie  nature  of  the 
movements  they  permit.  This  double  base  serves  to  establish  five  kinds  of 
diarthrodial  articulation 

1.  Enartlirosis,  characterised  by  the  reception  of  an  articular  head  within 


128  TEE  ARTICULATIONS. 

a  cavity  of  appropriate  form.  This  articulation  may  be  the  seat  of  the  most 
extensive  and  varied  movements :  flexion,  extension,  abduction,  adduction, 
circumduction,  and  rotation.     Example  :  the  coxo-femoral  articulation. 

2.  The  trochlean,  angular  ginglymoid,  or  perfect  hinge  articulation, 
when  the  articular  surfaces  are  formed  into  trochlea,  recii)rocally  fitting 
into  each  other,  and  whose  movements — flexion  and .  extension  only — are 
executed  with  the  precision  of  a  hinge.  Example :  the  tibio-tarsal  ar- 
ticulation. 

3.  The  condyloid,  or  imperfect  hinge  articulation,  which  permits,  like  the 
preceding,  the  two  principal  movements  of  extension  and  flexion,  and.  the 
accessory  movements  of  rotation  or  lateral  inclination.  The  articular 
surfaces,  fhough  very  diversely  shaped,  nevertheless  exhibit  in  all  the 
articulations  one  or  more  condyles  opposed  to  an  equal  number  of  oval 
excavations.     Example  :  the  femoro-tibial  articulation. 

4.  The  pivot,  trochoid,  or  lateral  ginglymoid  articulation,  is  a  diarthrosis 
formed  by  a  pivot  which  turns  in  a  semi-cylindrical  cavity.  Rotation 
is  the  only  movement.     Example  ;  the  atlo-axoid  articulation. 

5.  Arthrodia,  or  planiform  diarthrosis,  is  constituted  by  plane,  or  nearly 
plane  facets.  Gliding  is  the  only  possible  movement.  Example  :  the  carpo- 
metacarpal articulation. 

Nomenclature. — The  names  of  the  articulations  are  usually  those  of 
the  bones  which  form  them.  For  instance,  the  scapido-humcral  articulation 
is  the  joint  between  the  scapula  and  humerus  ;  the  intervertebral  articulations 
join  to  each  other  the  various  pieces  constituting  the  spine.  When  the 
qualifying  name  of  an  articulation  is  composed  of  two  elements,  as  in  the 
first  instance,  it  is  well  to  place  first  the  word  which  indicates  the  bone 
usually  most  fixed. 

GENERAL    CHARACTERS    OF   THE    SYNARTHROSES. 

Sutures  are  the  temporary  articulations  which  exist  only  at  an  early 
period  of  life.  They  nearly  all  disappear  in  the  adult  animal,  in  con- 
sequence of  the  bones  forming  them  becoming  consolidated.  They  belong 
almost  exclusively  to  the  bones  of  the  head. 

Articdlar  Surfaces. — The  bones  forming  these  come  in  contact  by  their 
borders  or  angles,  which,  for  this  purpose,  generally  present  very  anfractuous 
surfaces. 

Sometimes  they  are  cut  perpendicularly  and  simply  roughened ;  at 
other  times  they  are  bevelled  and  joined  by  means  of  fine  laminas  or  trifling 
inequalities ;  again,  they  are  notched  into  deep  and  sinuous  dentations ; 
and  lastly,  one  bone  is  fixed  into  a  groove  cut  in  the  other.  It  will  be 
understood  that  such  conformations  of  the  articular  surfaces  ought  to  limit 
their  movements  and  assure  the  solidity  of  their  union. 

Modes  of  Union. — Cartilage  interposed  between  these  synarthrodial 
surfaces  directly  unites  them  to  each  other.  It  absolutely  possesses  the 
same  texture  as  the  primary  cartilage  of  the  bones,  and  like  it,  has  the 
property  of  becoming  ossified  after  having  been  vascularised.  This  ossi- 
fication, which  causes  the  disappearance  of  the  sutures,  occurs  earlier 
inwards  than  outwards.  The  periosteum,  in  passing  from  one  bone  to 
another,  adheres  intimately  to  the  sutural  cartilage,  and  also  aids  in  bringing 
about  a  more  complete  synarthroses.  It  should,  therefore,  be  included  in 
their  means  of  union. 

Movements. — These  are  very  obscure,  and  only  noticeable  in  young 


ABTICULATIONS  OF  MAMMALIA  IX  FARTICULAB.  129 

animals  by  the  elasticity  they  communicate  to  the  bony  walls  of  the  cranium 
or  face.     In  the  adult,  they  may  be  said  to  be  null. 

Classification. — There  arc  four  principal  descriptions  of  sutures  : 
1,  When  two  viide  bones  corresj)ond  by  means  of  deuticulatious  fitting 
into  each  other,  the  suture  is  named  true  or  dentated.  Example :  the 
articulations  uniting  the  three  portions  of  the  parietal  bone.  2.  If  the 
opposed  borders  of  two  bones  in  contact  are  widely  bevelled,  one  inwards, 
the  other  outwards,  it  forms  a  scaly  or  squamous  suture.  Example :  the 
parieto-temporal  articulations.  3.  When  the  union  of  bones  takes  place 
by  plane  or  roughened  surfaces,  cut  perpendicularly  on  their  borders  or 
angles,  this  constitutes  the  harmonia  suture,  ov  suture  by  juxtaposition  (or  appo- 
sition). Example  :  the  occipito-temporal  articulations.  4.  The  schindylesis, 
or  mortised  suture,  results  from  the  reception  of  a  bony  plate  into  a  groove 
more  or  less  deep  in  another  bone.  Example :  the  spheno-frontal  and 
supermaxillo-nasal  articulations. 

GENERAL    CHARACTERS    OF    THE    AMPHIARTHROSES    OR    STSIPHTSES. 

Articular  Surfaces. — They  are  frequently  smooth,  and  formed  almost 
on  the  same  model  as  the  diarthrodial  surfaces.  They  are  covered  by  a 
thin  layer  of  cartilage,  but  instead  of  being  smooth  and  polished,  they  are 
more  or  less  rugged,  without,  however,  presenting  the  anfractuous  disposition 
of  the  majority  of  synarthrodial  surfaces. 

Modes  of  Union. — The  organs  which  perform  this  office  are :  1,  The 
fibro-cartilage  which  establishes  continuity  between  the  articular  surfaces  ; 
2,  Eibbon-shaped  or  j)eripheral  ligaments.  These  latter  do  not  differ  from 
the  analogous  bands  attaching  the  diarthrodial  articulations.  With  regai'd 
to  the  fibro-cartilage,  it  is  distinguished  from  the  complementary  discs  of 
these  same  articulations  by  a  less  intimate  mixture  of  the  cartilaginous  and 
fibrous  elements  entering  into  its  composition.  The  last  may  be  sometimes 
absent,  as  well  as  the  peripheral  bands  ;  and  then  the  articulation  only  differs 
from  the  synarthroses  by  the  extent  of  motion  it  permits  Occasionally  the 
interarticular  fibro-cartilages  are  excavated  by  one  or  two  little  narrow  cavities  : 
but  these  are  never  lined  by  a  synovial  membrane  like  the  diarthrodial 
cavities. 

Movements. — The  amphiarthroses  only  permit  of  a  see-saw  or  swinging 
movement,  the  extent  of  which  depends  on  the  thickness  of  the  intermediate 
fibro-cartilage. 

Classification. — Only  one  kind  of  amphiarthrosis  is  recognised,  the 
most  remarkable  example  of  which  is  found  in  the  articulations  between  the 
bodies  of  the  vertebree. 


CHAPTER  II. 
AETICULATIONS    OF    MAMMALIA   IN   PAETICULAR. 

In  the  special  study  of  the  articulations,  the  same  order  will  be  followed 
as  for  the  bones ;  the  articulations  of  the  spine  will  be  fii'st  noticed,  then 
those  of  the  head,  thorax,  and  anterior  and  posterior  limbs. 

Preparation. — The  preparation  of  the  bones  which  have  been  described 
has  not  been  made  the  subject  of  any  particular  recommendation,  because 
it  suffices,  in  order  to  study  them,  to  remove  the  soft  parts  by  which  they 


130  TEE  ARTICULATIONS. 

are  surrounded  either  by  boiling,  maceration,  or  scraping.  But  when  we 
come  to  examine  the  soft  textures,  in  order  to  do  so  profitably  it  is  necessary 
to  learn  beforehand  the  rules  which  should  be  fullowed  in  their  preijaratiou. 
The  following  are  laid  down  with  regard  to  the  study  of  the  articulations : 

1.  To  prepare  the  articulations,  young  subjects  are  chosen  in  preference  to  those  ad- 
vanced in  years,  because  the  density  of  the  cellular  tissue  in  them  is  uot  so  great,  and  this 
tissue  is  easily  removed  from  around  the  ligaments.  As  these  are  prepared  with  difficulty 
when  the  external  surface  is  in  a  dry  state,  care  should  be  taken  before  dissecting  them 
to  have  them  excluded  from  the  air  by  covering  them  with  damp  cloths,  or  with  the 
skin  of  the  animal. 

2.  It  is  convenient  to  separate  the  articulation  we  wish  to  dissect  by  sawing  through 
the  bones  at  a  certain  distance  from  the  articular  surfaces.  The  manipulation  of  the 
part  is  then  rendered  easier,  and  its  dissection  can  be  made  under  the  most  favourable 
conditions. 

3.  It  is  necessary  to  preserve  as  carefully  as  possible  the  muscles  surrounding  the 
articulations,  in  order  to  be  able  to  study  their  relations  with  the  ligaments  whicli  bind 
these.  If  it  be  absolutely  necessary  to  remove  them,  their  insertions  corresponding  to 
the  articulation  should  always  be  retained. 

4.  The  capsular  ligaments  should  be  the  first  studied,  as  these  have  soon  to  be 
removed  the  better  to  show  the  funicular  ligaments.  These,  in  their  turn,  must  be 
sacrificed  in  order  to  display,  by  different  sections,  the  interosseous  cords,  when  these  exist. 
Lastly,  the  two  articular  surfaces  should  be  completely  separated,  so  as  to  examine 
their  conformation. 

5.  The  synovial  membranes,  with  their  different  culs-de-sac,  being  a  very  important 
study,  with  reference  to  the  diagnosis  and  treatment  of  articular  tumours,  it  is  convenient 
to  devote  a  special  piece  to  the  examination  of  these  serous  membranes.  It  is  very 
useful  to  inject  their  interior  with  plaster  or  tallow  coloured  black,  in  order  to  distend 
their  cavities,  and  thus  aid  the  study  of  their  relations  Avith  ligaments,  tendons,  or 
muscles. 

For  the  preparation  of  each  articulation  it  is  not  necessary  to  give  any  directions; 
a  glance  at  the  figures  accompanying  the  description  will  suffice  to  dispel  any  embarass- 
ment  the  student  may  experience,  while  he  always  requires  particul  ir  indications. 

(Notwithstanding  the  above  remarks  with  regard  to  the  preparation  of  the  ligaments, 
I  have  thought  it  advisable  to  follow  the  example  given  in  the  last  edition  of  '  Leyh'a 
Anatomy'  by  Zundel,  and  briefly  indicate  the  readiest  method  of  demonstrating  these 
organs,  for  the  special  benefit  of  the  student.) 

Article  I. — Articulations  of  the  Spine. 

(Preparation. — Remove  all  the  soft  parts  surrounding  the  vertebral  column,  taking 
care  not  to  injure  the  inferior  longitudinal  ligament  in  cutting  away  the  pillars  of  the 
diaphragm  and  the  psoas  muscles ;  nor  the  ligaments  uniting  the  articular  processes  to  each 
other  and  the  transverse  processes  of  the  dorsal  vertebra;  to  the  ribs,  in  removing  the 
supercostal  and  transverse  spinal  muscles.  To  expose  the  common  superior  longitudinal 
ligament,  separate  the  bodies  of  the  vertebrfe  from  their  annular  portions  by  the  saw  or 
chisel,  and  remove  the  spinal  cord  and  dura  mater ;  in  doing  this  the  inferior  face  of  the 
interannular  ligaments  will  be  also  removed.  Examine  an  intervertebral  fibro-cartilage 
by  two  sections — a  transverse  at  an  equal  distance  from  the  two  vertebrae,  and  a  longi- 
tudinal through  the  middle  line  of  the  bodies.) 

These  articulations  are  intrinsic  and  extrinsic.  The  first  comprises  all 
the  articulations  of  the  vertebrse  with  each  other ;  the  second  those  of  the 
spine  with  the  head,  the  ribs,  and  the  coxse. 

Intervertebral  Articulations. 

The  vertebrae  correspond  :  1,  By  their  bodies ;  2,  By  their  spinal  or 
annular  portion.  There  results  from  this  union  two  kinds  of  articulation, 
which  must  be  studied  separately,  as  they  do  not  belong  to  the  same 
class.  It  is  well  to  mention,  however,  that  the  general  details  into  which 
this  study  leads  us  apply  only  to   the   articulations  uniting  the  last  six 


AUTICULATIONS  OF  THE  SFWE.  131 

cervical  vertebras,  all  the  dorsal  and  lumbar  vertebrae,  and  tbe  first  sacral 
vertebra. 

Union  of  the  Vertebra  by  their  Bobies. — The  articulations  forniing  this 
union  are  so  many  ami^biarthroses. 

Articular  surfaces. — Tbe  vertebral  bodies  come  into  contact  by  the 
surfaces  which  terminate  them  before  and  behind.  In  the  cervical  region 
these  surfaces  represent,  anteriorly,  a  veritable  head,  posteriorly,  a  cotyloid 
cavity  which  receives  the  head  of  the  next  vertebra.  Beginning  from  the 
first  dorsal  vertebra  and  passiug  on  to  the  sacrum,  these  tend  to  become 
effaced  and  more  and  more  plane,  though  they  still  preserve  their  convexity 
and  concavity. 

Modes  of  union.  — 1,  By  fibro-cartilages  interposed  between  the  articular 
surfaces ;  2,  By  a  common  superior  vertebral  ligament ;  3,  By  a  common 
inferior  vertebral  ligament. 

a.  Intervertebral  fihro-cartilages  (Fig.  80,  1,  1). — These  are  circular  or 
elliptical  discs,  convex  in  front,  concave  behind,  and  solidly  fixed  by  their 
faces  to  the  articular  planes  which  they  separate.  The  fibro-cartilaginous 
substance  composing  them  consists  of  concentric  layers,  which  become  denser 
and  closer  to  each  other  as  they  near  the  circumference ;  they  even  disappear 
towards  the  centre  of  the  disc,  where  this  substance  becomes  pulpy  and 
assumes  the  histological  characters  of  pure  cartilage.  It  may  be  remarked, 
that  each  of  these  layers  is  made  up  of  a  collection  of  thick  parallel  filaments, 
which  cross  with  those  of  other  layers  like  an  X,  and  are  attached  by  their 
extremities  to  the  articular  surfaces.  From  this  arrangement  results  so  inti- 
mate an  adherence  between  the  vertebral  bodies  and  their  intermediate  fibro- 
cartilages,  that  an  attempt  to  disunite  them  is  more  likely  to  determine  a 
fracture  of  the  former.  The  fibro-cartilages,  thicker  in  the  cervical  and 
lumbar  regions  than  in  the  dorsal,  respond  by  their  circumference  to  the 
two  common  ligaments.  Those  which  sejjarate  the  vertebriB  of  the  back 
concur  to  form  the  intervertebral  cavities,  \\  hich  are  destined  for  the  reception 
of  the  heads  of  the  ribs,  and  give  attachment  to  the  interosseous  costo- 
vertebral ligaments. 

(Leyh  designates  the  superficial  fibres  of  the  excentric  layer  of  these 
fibro-cartilages  as  intervertebral  ligaments.  Luschka  has  shown  that  the 
cartilages  are  in  reality  articular  capsules.) 

h.  Common  superior  vertebral  ligament  (Fig  83,  1). — This  ligament 
extends  from  the  axis  to  the  sacrum,  and  is  lodged  in  the  spinal  canal  ;  it 
represents  a  long  fibrous  band  cut  on  its  borders  into  wide  festoons.  (The 
wide  portions  correspond  to  the  discs.) 

By  its  inferior  face,  it  is  attached  to  the  intervertebral  discs  and  the 
triangular  imprints  on  the  upper  faces  of  the  bodies  of  the  vertebrae.  Its 
superior  face  is  in  contact  with  the  dura  mater  thi'ough  the  medium  of  an 
abundant  cellulo-adipose  tissue.  Its  borders  are  margined  by  the  intra- 
vertebral  venous  sinuses  (vence  hasium  vertebrariuni). 

c.  Common  inferior  vertebral  ligament  (Fig.  84, 5). — Situated  under  the  spine, 
this  ligament  is  absent  in  the  cervical  and  the  anterior  third  of  thedorsal  region. 
It  only  really  begins  about  the  sixth  or  eighth  vertebra  of  the  latter  region, 
and  is  prolonged  in  the  form  of  a  cord,  at  first  narrow,  then  gradually 
widening  until  it  reaches  the  sacrum,  on  the  inferior  surface  of  which  it 
terminates  by  a  decreasing  expansion.  From  its  commencement,  it  is 
attached  to  the  inferior  crest  of  the  bodies  of  the  vertebras  and  the  interver- 
tebral discs.     By  its  inferior  face,  it  responds  to  the  posterior  aorta. 

(Leyh  commences  this  ligament  at  the  seventh  cervical  vertebra,  and  says 


132  THE  ARTICULATIONS. 

that  it  adheres  to  the  crests  on  the  bodies  of  the  dorsal  and  lumbar  vertebrae, 
as  well  as  to  the  lower  face  of  the  sacrum  and  coccyx.  At  the  fifth  dorsal 
vertebra  it  widens  and  thickens,  and  in  the  lumbar  region  is  bound  ui>  with 
the  pillars  of  the  diaphragm  and  confounded  on  each  side  ^ith  the  large 
ligaments  of  the  pelvis.) 

Union  of  the  Vertebra  by  their  Spinal  Portions — Each  vertebra, 
in  uniting  by  its  annular  portion  with  that  which  follows  or  precedes  it, 
forms  a  double  arthrodial  joint. 

Articular  surfaces. — These  are  the  facets  cut  on  the  anterior  or  posterior 
articular  processes,  and  which  have  been  described  when  speaking  of  the 
vertebrae  themselves.      They  are  covered  by  a  thin  layer  of  cartilage. 

Modes  of  union. — 1,  A  common  superspinous  ligament;  2,  Interspinous 
ligaments  ;  3,  Interlamellar  ligaments  ;  4,  Ligamentous  capsvdes,  proper 
to  the  articular  processes. 

a.  Commoa  superspinous  ligament. — This  ligament,  whose  name  suf- 
ficiently indicates  its  situation,  extends  from  the  sacrum  to  the  occipital  bone 
and  is  divided  into  two  portions  :  one  posterior,  or  superspinous  dorso-lumbar 
ligament;  the  other  anterior,  or  superspinous  cervical  ligament.  These  two 
ligaments,  although  continuous  with  one  another,  yet  differ  so  strikingly 
in  form  and  structure  that  they  are  best  described  separately. 

1.  Superdorso-lumhar  ligament  (Fig.  80,  2).— This  is  a  cord  of  white 
fibrous  tissue,  which  cormnences  behind  on  the  sacral  spine  and  ceases  in 
fi-ont  about  the  inferior  third  of  the  dorsal  region  by  insensibly  assuming 
the  texture  and  elasticity  of  the  cervical  ligament,  with  which  it  is  continuous. 
It  is  attached  in  its  course  to  the  summits  of  all  the  lumbar  spinous  processes 
and  to  the  ten  or  twelve  last  dorsal.  On  the  sacral  spine,  it  is  confounded 
with  the  superior  ilio-sacral  ligaments.  In  the  lumbar  region,  it  is  united 
on  each  side  to  the  aponeuroses  of  the  common  mass  of  muscles. 

2.  Superspinous  cervical,  or  simply  cervical  ligament  (Fig.  104,  1,  2). — 
This  ligiimenfc  is  entirely  formed  of  yellow  fibrous  tissue,  and  constitutes, 
in  the  median  plane  of  the  body,  a  very  remarkable  elastic  apparatus  which 
separates  the  superior  cervical  muscles  of  the  right  side  from  those  of  the 
left,  and  plays  the  part  not  entirely  of  an  articular  band,  but  rather  of  a 
permanent  stay  charged  to  balance  the  weight  of  the  head. 

In  the  cervical  ligament  there  is  distinguished  a  funicular  and  a  lamellar 
portion.  The  first,  usually  called  the  cord  of  the  cervical  ligament,  is  a 
wide  funiculus  which  extends  directly  from  the  first  dorsal  spinous  processes 
to  the  summit  of  the  head.  Divided  into  two  lateral  lips  by  a  median  groove, 
this  cord  is  continued  posteriorly  with  the  dorso-lumbar  ligament,  and  is 
inserted  forwards  into  the  cervical  tuberosity  of  the  occipital  bone.  It  is 
covered  above  by  a  mass  of  fibro -adipose  tissue  which,  in  certain  common- 
bred  horses,  is  very  abundant.  Below,  it  gives  rise,  in  its  posterior  two- 
thirds,  to  the  majority  of  the  fibres  belonging  to  the  lamellar  portion.  On 
the  sides,  it  receives  the  insertions  of  several  cervical  muscles.  The  lamellar 
portion,  comprised  between  the  funicular  portion,  the  spinous  processes  of  the 
second  dorsal  vertebra,  and  the  cervical  stalk,  constitutes  a  vast  triangular 
and  vertical  septum,  which  itself  results  from  the  apposition  of  the  two 
laminae  which  lie  back  to  back,  and  are  imited  by  cellular  tissue ;  they  are 
bordered  above  by  the  two  lateral  lips  of  the  cord.  The  elastic  fibres  which 
enter  into  their  composition  are  given  off  either  from  the  latter,  or  from  the 
spinous  processes  of  the  second  and  third  dorsal  vertebrae  ;  they  are  directed 
downwards  or  forwards,  and  reach  the  spinous  processes  of  the  last  six 
cervical   vertebraB,  into  which  they  are  inserted  by  so  many  digitatious, 


ARTICULATIONS  OF  THE  SPINE. 


133 


Ficr.  80. 


becoming  confounded  with  the  interspinous  ligaments  of  the  neck.  The 
fibres  of  the  two  hist  digitations  are  lew  in  number,  widely  separated  from 
one  another,  and  united  by  many  anastomosing  brandies,  which  make  them 
appear  as  a  kind  of  wide  network.  The  lamiuas  of  the  cervical  ligament  are 
in  relation,  outwardly,  with  the  superior  branch  of  the  ilio-spinal  ligament, 
the  transverse  sjiiuous  muscle  of  the  neck,  and  the  great  complcxus. 

(This  important  structure,  which  is  in  reality  the  mechanical  stay  and 
support  of  the  heavy  head  and  neck  of  quadrupeds,  and  is  usually  termed  the 
ligamentum  nuchce,  is  all  but  abseut  in  Man,  being  represented  in  him  by  a  thin 
narrow  band,  or  rather  two  thin  planes  of  fibres,  the  ligamenta  suhflava.  It  is 
described  by  Leyh  as  if  there  were  not  two  portions,  and  that  excellent 
anatomist  does  not  appear  to  insist  sufficiently  on  the  difierence  between  the 
dorso-nuchal  and  the  dorso-lumbar  divisions.  Percivall,  who  almost  entirely 
neglects  the  ligaments,  also  makes  no  distinction.  The  dilference  in  structure, 
elasticity,  and  situation,  warrants  the  distinction  made  by  Chauveau.  As 
already  indicated,  the  function  of  this  ligament,  and  more  particularly  of  its 
nuchal  division,  is  to  maintain  the  head  and  neck  in  their  natural  position 
dm-ing  repose,  and  to  allow  the  most  extensive  movements  at  other 
times.) 

b.  Interspinous  ligaments  (Fig.  80,  3). — Fibrous  laminfe  fill  the  inter- 
spinous spaces,  and  are  attached,  before  and  behind,  to  the  opposite  borders 
of  the  spinous  processes  which  they  unite  ;  they 
are  continued  below  by  the  interlamellar  liga- 
ments, forming  two  lateral  planes  which  are 
applied  against  each  other,  like  the  laminae  of  the 
cervical  ligament,  and  covered  outwardly  by  the 
transverse  spinous  (dorsalis  colli)  mixscle. 

In  the  region  of  the  neck,  the  interspinous 
ligaments  are  yellow  and  elastic.  In  the  dorso- 
lumbar  region,  they  are  formed  by  fasciculi  of 
white  fibrous  tissue,  loosely  united  to  each  other 
at  their  extremities,  and  directed  very  obliquely 
backwards  and  downwards.  In  consequence  of 
this  disposition,  and  notwithstanding  their  in- 
extensibility,  they  permit  the  separation  of  the 
spinous  processes.  Their  lateral  surfaces  are 
divided  by  a  layer  of  grey  elastic  fibres,  which 
cross  like  an  X  the  direction  of  the  preceding 
fasciculi.  Very  abundant  in  the  anterior  moiety 
of  the  dorsal  region,  these  fibres  operate,  by  their 
proper  elasticity,  in  bringing  the  spinous  pro- 
cesses towards  each  other. 

c.  Interlamellar,  or  interannular  ligaments. — 
Situated,  as  their  name  indicates,  between  the 
vertebral  laminae,  and  divided  into  two  lateral 
moieties,  these  ligaments  appear  to  be  produced 
by  the  two  fibrous  planes  of  the  preceding  ligaments,  which,  on  arriving 
at  the  base  of  the  spinous  processes,  separate  from  one  another  to  be  carried 
outwards.  Their  anterior  border  is  inserted  into  the  posterior  margin  of  the 
vertebral  lamina  in  front.  Their  posterior  border  is  fixed  to  the  anterior 
border  and  inferior  face  of  the  lamina  behind.  Their  superior  face  is  in 
relation  with  some  spinal  muscles,  and  their  inferior  face  is  in  contact  with 
the  dura  mater.     Outwardly,  they  are  confounded  with  the  capsules  proper 

12 


INTEKVERTEBRAL    ARTICULA- 
TIONS. 

A,  B,  c,  Bodies  of  three  dorsal 
vertebras  divided  longitudi- 
nally and  vertically  to  show 
(1,  1)  a  section  of  the  in- 
tervertebral discs;  2,  Super- 
spinous  dorso-lumbar  liga- 
ment ;  3,  Interspinous  liga- 
ment ;  4,  Fibrous  fascia,  con- 
stituting the  proper  capsule 
to  the  articular  processes 
in  the  dorsal  region. 


134  THE  ARTICULATIONS. 

to  the  articular  processes.  Yellow  and  elastic  in  the  cervical  region,  these 
ligaments  are  white  and  inelastic  in  the  dorso-lumbar  region. 

d.  Capsules  p-oper  to  the  articular  processes  (Fig.  81,  5). — Each  anterior 
articular  process  is  maintained  against  the  corresponding  posterior  process 
by  a  dii'ect  band :  this  is  a  perii^heric  capsule  attached  around  the 
diarthrodial  facets,  doubled  internally  by  a  synovial  membrane  -which 
facilitates  their  gliding,  and  covered,  outwardly,  by  the  insertions  of  some 
spinal  muscles.  These  capsules,  yellow  and  elastic  in  the  cervical,  are 
composed  of  white  fibrous  tissue  in  the  dorso-lumbar  region.  Very  developed 
at  the  neck,  in  consequence  of  the  thickness  of  the  articular  tubercles  they 
envelope,  they  become  reduced,  near  the  middle  of  the  back,  to  some  fibres 
which  cover,  outwardly,  the  diarthrodial  facets  in  contact. 

Characters  proper  to  some  Intervertebral  Articulations. — 1.  Inter- 
coccygeal  and  sacro-coccygeal  articulations. — These  are  constructed  after  the 
same  type  as  the  other  spinal  articulations,  except  that  they  are  appropriate  to 
the  rudimentary  state  of  the  vertebrae  they  unite.  The  coccygeal  bones  only 
come  in  contact  by  their  bodies,  their  spinal  laminae  being  reduced  to  the 
merest  traces,  or  are  altogether  absent.  The  anterior  and  posterior  articular 
surfaces  of  each  vertebra  are  convex,  and  the  interarticular  fibro-cartilages, 
hollow  on  both  faces,  resemble  a  biconcave  lense.  With  regard  to  the 
peripheral  bands,  they  are  represented  by  a  bundle  of  longitudinal  fibres 
spread  over  the  surface  of  the  bones,  which  they  envelope  in  a  common  sheath. 

2.  Intersacral  articulations. — The  sacral  vertebrae  being  fused  into  one 
piece — the  os  sacrum — there  is  no  occasion  to  study  the  true  articulations  in 
this  region.  It  may  be  remarked,  however,  that  the  superspinous  dorso- 
lumbar  ligament  is  continued  on  the  sacral  spine,  and  tljat  there  exist  be- 
tween the  processes  formed  by  this  spine  veritable  interspinous  ligaments. 

3.  Sacro-Iumhar  articidatiun. — In  this  articulation,  the  great  thickness  of 
the  fibro-cartilage  is  to  be  remarked  ;  and,  in  addition,  that  the  last  lumbar 
vertebra  corresponds  with  the  sacrum  not  only  by  its  body  and  articular 
processeSy^  but  also  by  the  oval  and  slightly  concave  facets  shown  on  the 
posterior  border  of  its  transverse  processes,  which  are  adapted  to  analogous 
slightly-convex  facets  on  the  sides  of  the  base  of  the  sacrum.  The 
bundles  of  fibres  thrown  from  one  bone  to  another  from  around  these  sacra- 
transversals  (real  planiforra  diarthroses)  maintain  the  articular  surfaces  in 
contact,  and  cover,  outwardly,  the  synovial  membrane  which  facilitates  their 
gliding. 

4.  Articidation  of  the  two  last  lumbar  vertebrse. — This  is  distinguished  by 
the  presence,  between  the  transverse  processes,  of  a  planiform  diurthrosis 
like  that  of  the  sacro-transversal  just  noticed.  These  two  articulations  are 
only  found  in  Solipcds. 

5.  Atlo-axoid  articulation. — This  is  so  far  removed  by  its  conformation 
and  special  uses  from  the  other  intervertebral  articulations,  that  it  will  be 
described  as  an  extrinsic  articulation  of  the  head  and  spine.  (See  the 
Articidations  of  the  Head. ) 

The  Movements  of  the  Spine  in  general. — Each  intervertebral  articula- 
tion is  the  seat  of  very  obscure  movements,  whose  separate  study  oficrs  little 
interest.  But  these  movements,  when  conjoined  with  those  of  the  other 
articulations,  result  in  bending  the  whole  sjunal  stalk  in  a  somewhat 
marked  manner,  and  producing  either  the  flexion,  extension,  or  lateral 
inclination  of  this  flexuons  column. 

When  flexion  takes  place,  the  spine  is  arched  upwards,  the  common 
inferior   ligament   is   relaxed,   tlie    spinous   processes    separate   from  one 


ARTICULATIONS  OF  THE  HEAD.  135 

another,  and  the  superspinous  ligament,  becoming  very  tense,  soon  imposes 
limits  to  this  movement. 

Extension  is  etiected  by  an  inverse  mechanism,  and  is  checked  by  the 
tension  of  the  common  inferior  ligament  and  the  meeting  of  the  spinous 
processes. 

Lateral  inclination  takes  place  when  the  spine  bends  to  one  side.  This 
movement  is  very  easily  executed  in  the  cervical  and  coccygeal  regions,  but 
is  arrested  by  the  ribs  and  the  costiform  processes  in  the  dorso-lumbar 
region, 

A  circumflex  movement  is  possible  at  the  two  extremities  of  the  vertebral 
column — neck  and  tail ;  for  they  pass  easily  from  extension  to  lateral 
inclination,  and  from  this  to  flexion,  etc. 

Owing  to  the  elasticity  of  the  intervertebral  fibro-cartilages.  the  spine 
is  endowed  with  a  very  limited  amount  of  rotation,  or  rather  of  torsion. 

For  the  special  study  of  the  movements  of  each  spinal  region,  reference 
must  be  made  to  what  has  been  already  said  (page  29)  regarding  the 
mobility  of  this  column. 

In  the  Ox  the  intervertebral  discs  are  much  thicter  than  in  the  Horse.  The  common 
inferior  vertebral  ligament  is  very  strong  in  the  lumbar  region.  The  superspinous 
dorso-lumbar  ligament  is  composed  of  yellow  elastic  tissue.  Tlie  cervical  ligament 
13  much  more  developed  than  in  Solipeds,  in  consequence  of  the  greater  weight  of 
the  head ;  and  it  presents  a  conformation  altogether  special,  which  M.  Lecoq  has  made 
known  in  the  following  terms :  "  On  leaving  the  withers,  the  superspinous  ligament 
ceases  to  cover  the  head  of  the  spinous  processes,  and  extends  from  each  side  ia  a  wide 
and  strong  band,  taking  points  of  attachment  on  the  sides  of  the  processes,  and  becoming 
separated,  on  leaving  that  of  the  first  dorsal  vertebra,  into  two  parts — a  superior  and 
inferior.  The  first  reaches  the  cervical  tuberosity  in  the  form  of  a  thick  cord  united  to 
the  cord  of  the  opposite ;  the  other  thins  oft"  into  a  baud  which  is  attached  to  the  posterior 
half  of  the  spinous  process  of  the  axis  and  to  that  of  the  third  and  fourth  vertebra.  A 
production  of  tlie  same  nature,  an  auxiliary  to  the  principal  portion,  leaves  the  anterior 
border  of  the  spinous  process  of  the  first  dorsal  vertebra,  and  is  attached  to  that  of  the 
fourth,  fifth,  sixth,  and  seventh  vertebra.  The  superior  border  of  this  auxiliary  liga- 
mentous prodiiction  is  concealed  between  the  two  lamina  of  the  principal  ligament."  ' 

The  Pig.  remarkable  for  the  shortness  of  its  neck  and  the  limited  movements  of  this 
region,  does  not  show  any  cervical  ligament,  properly  so  called.  It  is  replaced  by  a 
superficial  fibrous  raphe'  extending  from  the  occipital  bone  to  the  spinous  process  of  the 
first  dorsal  vertebra. 

The  Cat  has  no  cervical  ligament,  and  shows,  instead,  a  raphe  like  the  Pig.  In 
the  Bog  the  ligament  is  reduced  to  a  simple  cord,  continued  from  the  dorso-lumbar 
ligament,  and  which  goes  no  further  than  behind  the  spinous  process  of  the  axis.  In 
the  Cat  the  interspinous  ligaments  are  replaced  by  small  muscular  fasciculi ;  with  the 
Dog  this  substitution  only  takes  place  in  the  cervical  region.  The  laminse  of  the  first 
coccygeal  vertebrae  possess  the  principal  characters  which  distinguish  perfect  vertebr». 
and  are  imited  by  vestiges  of  the  articular  bands  which  exist  in  the  other  regions  of 
the  spiue. 

Article  II. — ABTiCTJiiATioxs  of  the  Head. 

We  will  first  study  the  two  extrinsic  ai'ticulations  which,  are  the  centre 
of  the  movements  of  the  head  on  the  spine — the  atlo-axoid  and  occipito-atloid 
articulations.  Afterwards,  we  will  pass  to  the  examination  of  the  joints  which 
unite  the  different  bones  of  the  head. 

1.  Atlo-axoid  Articulation. 

{Preparaiion. — It  suffices  to  remove  the  soft  parts  from  around  the  articulation  to 
expose  the  interannular,  the  interspinous,  and  the  inferior  odontoid  ligament.    To  examine 


'  Joiurnal  de  Me'decine  Ve'te'rinaire '  (Lyons,  1848;,  p.  122. 


136  THE  ARTICULATIONS. 

the  superior  odontoid  ligament  and  the  synovial  membrane,  one  half  the  atlas  and  axis 
must  be  separated  by  sawing  longitudinally  through  them  from  one  side  to  the  other.) 

This  may  be  considered  as  tlie  type  of  the  troclioides. 

Articular  surfaces. — To  form  this  articulation,  the  axis  offers  its  odontoid 
pivot  and  the  undulated  diarthrodial  facets  at  its  base.  The  atlas  opposes 
to  the  pivot  the  concave  semicylindi-ical  surface  hollowed  on  the  superior 
face  of  its  body ;  and  for  the  lateral  undulated  facets  it  has  analogous  facets 
which  are  cut  on  the  transverse  processes,  on  each  side  of  the  vertebral  canal. 

3Iode  of  union. — 1.  An  odontoid,  or  odonto-atloid  ligament ;  2.  An 
inferior  atlo-axoid  ligament ;  3.  A  superior  ditto  ;  4.  A  fibrous  capsule. 

a.  Odontoid  ligament  (Fig.  81,  3). — Continued  to  the  common  superior 
vertebral  ligament,  very  short  and  strong,  flattened  from  above  to  below, 
and  triangular  in  shape,  the  odontoid  ligament  is  composed  of  glistening 
white  fibres,  fixed  behind  in  the  superior  channel  of  the  odontoid  process, 
and  inserted  in  front  on  the  transverse  ridge  which  separates  the  superior 
face  from  the  inferior  arch  of  the  atlas,  as  well  as  on  the  imprints  situated 
in  front  of  this  ridge.  This  ligament  is  covered,  on  its  lower  face,  by  the 
synovial  membrane  of  the  articulation ;  and  by  its  upper  surface  is  in 
contact  with  the  spinal  dura  mater.  It  sends  some  bands  within  the 
condyles  of  the  occipital  bone. 

b.  Inferior  atlo-axoid  ligament. — This  is  a  wide,  thin,  and  nacrous- 
looking  band,  extending  from  the  inferior  face  of  the  axis  to  the  inferior 
tubercle  of  the  atlas,  and  covered  by  the  long  muscle  of  the  neck ;  it  is 
united  to  the  synovial  membrane  by  its  deep  face,  and  confounded  on  its 
borders  with  the  fibrous  capsule  to  be  immediately  described. 

c.  Superior  atlo-axoid  ligament.— This  exactly  represents  the  inter- 
spinous  ligaments  of  the  other  cervical  articulations.  Yellow,  elastic,  and 
formed  like  the  two  lateral  bands,  it  is  continuous,  laterally,  with  the 
capsular  ligament. 

d.  Capsular  ligament. — This,  it  may  be  said,  is  only  the  interlamellar 
ligament  proper  to  the  atlo-axoid  articulation.  It  commences  from  the 
sides  of  the  preceding  ligament,  and  becomes  united  to  the  inferior  atlo- 
axoid  one,  after  contracting  adhesions  with  the  borders  of  the  odontoid 
ligament.  In  this  way  it  encloses  the  articulation  and  the  spinal  canal. 
Before  and  behind,  it  is  attached  to  the  anterior  or  posterior  margin  of 
the  bones  it  unites.  Its  external  face  is  in  contact  with  the  great  oblique 
muscle  of  the  head ;  its  internal  responds,  in  its  inferior  half,  to  the  articular 
synovial  membrane,  and  its  superior  moiety  to  the  spinal  dura  mater. 
(Leyli  describes  this  ligament  as  the  interannular.) 

Synovicd  membrane. — This  lines  the  odontoid  ligament,  the  atlo-axoid 
ligament,  and  the  articular  portion  of  the  perijiheral  capsule. 

Movements. — Botation,  the  only  movement  possible  in  the  atlo-axoid 
articulation,  is  effected  in  the  following  manner :  the  axis  remains  fixed, 
and  the  first  vertebra,  drawn  to  one  side  chiefly  by  the  great  oblique 
muscle,  rotates  on  the  odontoid  pivot,  carrying  the  head  with  it. 

In  the  Dog  and  Cat  the  odontoid  ligament  is  replaced  by  Ihree  particular  ligaments  : 
1,  Two  lateral  cords,  rising  in  common  from  tlie  summit  of  the  odontoid  process,  and 
inserted,  each  on  its  own  side,  within  the  condyles  of  the  oceijiital  bone ;  2,  A  transverse 
ligament,  passing  over  the  odontoid  process,  which  it  maintains  in  its  place  against  the 
inferior  arch  of  the  atlas,  and  is  attached  by  its  extremities  to  the  superior  face  of  the 
latter.  A  small  synovial  capsule  facilitates  the  gliding  of  the  odontoid  process  beneath 
this  ligament.  The  articular  synovial  membrane  always  communicates  with  that  of  the 
occipito-atloid  articulation. 

In  the  Pig  the  disposition  is  nearly  the  same  as  in  the  Caruivora 


ARTICULATIONS  OF  THE  HEAD. 


137 


2.  OccipHo-atloid  Articulation. 

(Preparation. — Dissect  away  all  the  soft  parts  that  pass  from  the  neck  to  the  head 
and  cover  the  articulation,  and  more  particularly  the  flexor, 
the  recti,  and  the  small  oblique  muscles  of  the  head.     To  pig_  g^^ 

expose  the  synovial  membranes,  open  the  sides  of  the  capsular 
ligament.) 

This  is  a  condyloid  articulation. 

Articular  surfaces. — In  the  atlas,  the  two  cavities 
which  replace  the  anterior  articular  processes  and 
the  heads  of  the  other  vertebrfe ;  in  the  occipital 
bone,  the  two  condyles  flanking  the  sides  of  the  occi- 
pital foramen. 

Mode  of  union. — A  single  capsular  ligament  en- 
velopes the  entu-e  articulation ;  it  is  attached  by  its 
anterior  border  to  the  margin  of  the  occipital  con- 
dyles, and  by  its  posterior  to  the  anterior  contour  of  the 
atlas.  Thin  and  slightly  elastic  in  its  inferior  half, 
this  ligament  presents,  superiorly,  foui*  reinforcing 
fasciculi :  two  middle,  which  intercross  in  X — from 
whence  the  name  "  cruciform,"  sometimes  given  to  this 
ligament  (Fig.  81,  1,  1)  ;  and  two  lateral,  which  pass 
from  the  sides  of  the  atlas  to  the  base  of  the  styloid 
processes  (Fig.  81,  2,  2).  It  is  lined  within  by  the 
synovial  membranes,,  and  is  enveloped  externally  by  a 
large  number  of  muscles,  which  protect  the  articu- 
lation and  greatly  strengthen  it  everywhere.  Among 
these  may  be  particularly  noticed  the  straight  muscles 
of  the  head,  the  small  oblique,  and  the  great  com- 
plexus.  There  is  also  the  cord  of  the  cervical  liga- 
ment. 

Synovial  membranes. — These  membranes  are  two 
in  number,  one  for  each  condyle  and  corresponding 
rtloid  cavity.  Sustained  above,  below,  and  outwardly 
by  the  capsular  ligament,  they  are  related  inwardly 
to  the  dm-a  mater  and  to  the  fibrous  tractus  which, 
from  the  odontoid  ligament,  is  carried  to  the  in- 
ternal face  of  the  occipital  condyles. 

Movements.^-Extension,  flexion,  lateral  inclination, 
and  circumduction,  ai'e  the  possible  movements  of  the 
occipito-atloid  articulation. 

In  the  Pig,  Dog,  and  Cat  this  articulation,  strengthened 
as  it  is  by  the  capsular  and  odontoido-occipital  ligaments 
already  mentioned,  has  only  one  synovial  capsule. 

3.  Articulations  of  the  Bones  of  the  Head. 

If  we  except  the  articulation  which  unites  the 
inferior  jaw  to  the  cranium — the  temporo-maxillary — 
and  the  hyoideal  articulations,  it  will  be  found  that 
all  the  bones  of  the  cranium  and  face  are  united  to 
each  other  by  synarthrosis,  forming  the  diiferent 
kinds  of  sutures  already  generally  described  (page  128). 
Nothing  is  to  be  gained  by  entering  into  more  detail 


ATLO-OXOID  AND  OCCIPI- 
TO-ATLOID ARTICULA- 
TIONS. The  upper  arch 
of  the  atlas  has  been 
removed  to  show  the 
odontoid  ligament. 

1,  1,  Middle  accessory  fas- 
ciculi ;  2.  2,  Lateral 
fasciculi  of  the  capsular 
ligament  of  the  occipito- 
atloid  articulation  •,  3, 
Odontoid  ligament ;  4, 
Interspinous  ligament 
uniting  the  second  and 
third  vertebraj  of  the 
neck  ;  5,  Fibrous  capsule 
uniting  the  articular 
processes  of  these  verte- 
bra;.— A,  Anterior  in- 
ternal foramen  of  the 
atlas  converted  into  a 
groove  by  the  section  of 
the  bone  ;  B,  B,  Verte- 
bral foramina  of  the 
atlas  •  C,  C,  Foramina 
replacing  the  anterior 
notches  of  the  axis. 


Fi^.  82. 


138  THE  ARTICULATIONS. 

with  regard  to  these  articulations,  as  it  will  be  found  sufficient  to  call  to  mind 
the  topographical  description  of  each  piece  entering  into  their  formation. 

4.  Temporo-maxillary  Articulation. 

{Preparation. — Eemove  the  masseter  muscle  and  the  parotid  gland.  Saw  through  the 
head  about  the  middle  line.  Open  the  articulation  externally  to  exhibit  tlie  inter- 
arlicular  meniscus.) 

The   lower  jaw,  in   its   imion  with  the  cranium,  constitutes  a  double 
condyloid  articulation. 

Articular  surfaces. — With  the  temporal  bone,  these  are  the  condyle,  the 
glenoid  cavity,  and  the  supracondyloid  process  which  exists  at  the  base  of 
the  zygomatic  process.  The  glenoid  cavity  is  not  lined  by  cartilage,  and 
appears  to  be  merely  covered  by  synovial  membrane.  With  the  maxillary 
bone  there  is  the  oblong  condyle  situated  in  front  of  the  coronoid  process. 
Interarticular  fibro-cartilage. — The  articular  surfaces  just  named  are 
far  from  fitting  each  other  accurately ;  this  is 
only  accomplished  by  the  interposition  of  a 
fibro-cartilaginous  disc  between  the  temporal 
and  maxillary  bones.  This  disc  is  a  kind  of 
irregular  plate,  flattened  above  and  below, 
thicker  before  than  behind,  and  moulded  on 
each  of  the  diarthrodial  surfaces  it  separates. 
Its  superior  face,  therefore,  presents :  in  front, 
a  cavity  to  receive  the  condyle  of  the  temporal 
bone;  behind,  a  boss  which  is  lodged  in  the 
glenoid  cavity.  The  inferior  face  is  hollowed 
by  an  oblong  fossa  in  which  the  maxillary  con- 
dyle is  lodged. 

Mode  of  union. — A  fibrous  envelope — a  true 
capsular  ligament — surrounds  the  articulation, 
and  is  attached  by  its  borders  to  the  margin  of 
1,  InterarticulLi^fibro-cartilage ;  the  articular  surfaces  it  unites.  Formed,  out- 
2,  External  fasciculus  of  the  wardly,  by  a  thick  fasciculus  of  white  vertical 
capsular  ligament. — A,  Base  of  fibres  (Fig.  82,  2),  this  ligament  becomes  grey- 
the  coronoid  process ;  J.^Neck  igj^.^oloured  and  elastic  for  the  remainder  of 
MasLid  'JJoceiT  DrExteraal  its  extent,  and  greatly  diminishes  in  thickness, 
auditory  hiatus.  especially  in  front.     Its  inner  lace  is  Imed  by 

the  synovial  capsules,  and  adheres  to  the  cir- 
cumference of  the  interarticular  fibro-cartilage.  Its  external  face  responds, 
in  fi*ont,  to  the  temporal  and  masseter  muscles;  behind,  to  the  parotid 
gland;  inwardly,  to  the  external  pterygoid  muscle;  and  outwardly,  to  a 
fibrous  expansion  which  separates  it  from  the  skin.  (Leyh  mentions  a 
lateral  external  and  a  posterior  ligament  for  this  articulation,  but  Chauveau 
and  Eigot  evidently  look  upon  these  as  portions  of  the  capsular.) 

Synovial  membranes. --This  articulation  has  two  synovial  sacs,  one  above 
the  other,  which  are  separated  by  the  fibro-cartilaginous  disc. 

Movements. — The  temporo-maxillary  articulation  is  the  centre  of  all  the 
movements  performed  by  the  lower  jaw.  These  are :  depression,  elevation, 
lateral  motion,  and  horizontal  gliding. 

The  lower  jaw  is  depressed  when  it  separates  from  the  superior  one,  and 
is  elevated  when  it  approaches  this.  These  two  opposite  movements  are 
executed  by  a  mechanism  of  such  great  simplicity  that   it   need  not  be 


TEMPORO-MAXILLARY    ARTICU- 
LATION. 


ARTICULATIONS  OF  THE  HEAD.  139 

described  here.  Lateral  movements  take  place  when  the  inferior  extremity  of 
the  jaw  is  carried  alternately  to  the  right  and  left.  It  then  happens  that 
one  of  the  maxiUary  condyles,  taking  with  it  the  hbro-eartilage,  is  brougbt 
into  contact  with  the  temporal  condyle,  while  the  other  is  imbedded  in  the 
glenoid  cavity  of  the  opposite  side.  The  horizontal  tjliding  is  effected  from 
behind  to  before,  or  vice  versa.  In  the  first  case,  the  two  maxillary  condyles 
are  carried  at  the  same  time  under  the  temporal  condyles,  bear  in  cr  with 
them  the  fibro-cartilages.  In  the  second  case,  they  are  drawn  into  the 
glenoid  cavities,  and  rest  against  the  supracondyloid  eminence,  which 
prevents  their  going  further.  It  will  be  understood,  after  tliis  brief 
description,  that  the  presence  of  the  fibro-cartilages  singularly  favours  the 
lateral  movements  and  horizontal  gliding  of  the  lower  jaw. 

In  the  Pig  the  temporo-masillary  articulation  is  formed  after  the  same  type  as  that 
of  rodents,  and  allows  very  extensive  movements  from  before  to  behind ;  a  circmnstance 
due  to  the  complete  absence  of  the  supracondyloid  eminence. 

In  the  Dog  and  Cat  the  maxillary  condyle  is  exactly  fitted  into  the  temporal  cavity. 
This  disposition,  in  giving  gi-eat  precision  to  the  movements  of  depression  and  elevation, 
restrains  in  a  singular  manner  the  lateral  and  horizontal  gliding  motions.  The  inter- 
articular  tibro-cartilage  is  extremely  thin  in  these  animals. 

5.  Hyoideal  Articulations. 

(Preparation. — Disarticulate  the  lower  jaw,  and  dissect  away  from  the  right  of  each 
articulation  the  muscles  that  may  conceal  the  view.) 

These  are  of  two  kinds :  extriiisic  and  intrinsic.  The  first  comprise  the 
two  temporohyoideal  articulations  ;  to  the  second  belong  the  joints  which 
unite  the  different  pieces  of  the  hyoid  bone — the  interhijoideal  articulations. 

TEMroKo-HYOiDEAL  AuTicuLATioxs.— These  are  two  amphiarthrodial 
joints,  in  the  formation  of  which  each  great  branch  of  the*  hyoid  bone 
opposes  its  upper  extremity  to  the  hyoideal  prolongation  lodf^ed  in  the 
vaginal  sheath  of  the  temporal  bone.  An  elastic  cartilage,  from  i-lOths  to 
6-lOths  of  an  inch  in  length,  unites  the  two  bones  in  a  solid  manner ;  and 
it  is  owing  to  the  flexibility  of  this  cartilage  that  the  hyoid  bone  can  move 
entirely  on  the  temporal  bones. 

Interhtoideal  ARTICUL.A.TIONS. — A.  The  great  branch  articulates  with 
the  small  one  by  an  amphi arthrosis  analogous  to  the  preceding.  To  form 
this  articulation,  these  two  pieces  of  bone  are  joined  at  an  acute  ano-le 
through  the  medium  of  a  more  or  less  thick  cartilaginous  band,  in  the 
centre  of  which  there  is  often  a  little  bony  nucleus.  This  cartilage  is  elastic 
and  flexible,  and  permits  the  opening  and  closing  of  the  articular  ancfle  at 
the  summit  of  which  it  is  jilaced. 

B.  Each  small  branch  is  united  to  the  body  of  the  hyoid  bone  by  an 
arthrodial  articulation.  The  articular  surfaces  are  :  for  the  hyoideal  branch, 
the  small  cavity  terminating  its  inferior  extremity ;  for  the  body,  the 
rounded  lateral  facet  situated  at  the  origin  of  the  comu.  These  surfaces 
are  covered  by  cartilage,  and  enveloped  by  a  small  synovial  sac  and  a 
peripheral  fibrous  capsule.  They  can  glide  on  each  other  in  nearly  every 
direction.  (Median  and  superior  hyoideal  capsular  ligaments  are  described 
by  Leyh  as  sometimes  present.  The  latter  imites  the  upper  and  middle 
branches,  and  the  former  the  middle  with  the  inferior  branches.  They  are 
absent  when  these  branches  are  confounded  with  the  superior  ones. j 


HO 


THE  ARTICULATIONS. 


Article  III. — Articulations  of  the  Thorax. 

These  are  also  divided  into  extrinsic  and  intrinsic.  The  jSrst,  named 
costo-vertebral,  unite  the  ribs  to  the  spine.  The  second  join  the  different 
pieces  of  the  thorax  together ;  they  comprise :  1,  The  chondro-sternal 
articulations ;  2,  Chondro-costai  articulations ;  3,  The  articulations  of  the 
costal  cartilages  with  each  other ;  4,  The  sternal  articulation  peculiar  to 
the  larger  Euminants  and  the  Pig.  All  these  joints  will  be  first  studied  in  a 
particular  manner,  then  examined  in  a  general  way  as  to  their  movements. 

1.  Articulations  of  the  Bihs  with  the  Vertebral  Column,  or  Costo-vertebral 

Articulations. 

Each  rib  responds  to  the  vertebral  column  by  two  points— its  head  and 
its  tuberosity.  The  first  is  received  into  one  of  the  intervertebral  cavities 
hollowed  out  on  the  sides  of  the  spine,  and  is  therefore  in  contact  with  two 
dorsal  vertebrae ;  the  second  rests  against  the  transverse  process  of  the 
posterior  vertebra.  From  this  arrangement  arises  two  particular  articulations 
belonging  to  the  arthrodial  class,  which  are  named  costo-vertebral  and  costo- 
transverse. 

CosTO- VERTEBRAL  ARTICULATIONS. — Articular  surfaces. —  Pertaining  to 
the  rib,  we  have  the  two  convex  facets  of  the  head,  separated  from  each 
other  by  a  gi'oove  of  insertion  and  covered  by  a  thin  layer  of  cartilage. 
On  the  vertebrae,  the  concave  facets  which  by  their  union  form  the  inter- 
vertebral cavity ;  these  facets  are  also  covered  with  cartilage,  and  separated, 
at  the  bottom  of  the  cavity  by  the  corresponding  intervertebral  disc. 

Mode  of  union. — 1.  An  interarticular  ligament  (Figs.  83,  2 ;  84,  1),  im- 
planted in  the  groove  of  insertion  of  the  head  of  the  rib,  and  attached  to 


Fig.  83. 


Fifr.  84-. 


ARTICULATIONS  OF  THE  RIBS  WITH  THE  VER- 
TEBR.«,  AND  OP  THESE  WITH  EACH  OTHER 
(UPPER    plane). 

1,  Spinal  canal,  upper  face,  showing  the 
common  superior  ligament ;  2,  Interar- 
ticular costo-vertebi-al  ligament;  3,  Inter- 
osseous costo-ti'ansverse  ligament ;  t.  Pos- 
terior costo-transverse  ligament. 


ARTICULATIONS  OF  THE  RIBS  WITH  THE  VER- 
TEBR.E,  AND  OF  THESE  WITH  EACH  OTHER 
(INFERIOR   PLANE). 

1,  Interarticular  costo-vertebral  ligament; 
2,  3,  4,  Fasciculi  of  the  stellate,  or  in- 
ferior costo-vertebral  ligament ;  5,  Common 
inferior  vertebral  ligament. 


the  superior  border  of  the  intervertebral  disc,  which  it  encircles  upwards 
and  inwards,  to  unite  on  the  median  line  with  the  ligament  of  the  opposite 
side.  2.  An  inferior  periphera  i  ligament  (Fig.  84,  2,  3,  4),  flat  above  and 
below,  thin  and  radiating  (whence  it  is  often  named  the  stellate  ligament), 
formed  of  three  fasciculi  which  are  fixed  in  common  on  the  inferior  face  of 


ARTICULATIONS  OF  THE  THOBAX.  141 

the  head  of  the  rib,  and  in  diverging  are  carried  over  the  bodies  of  the  two 
vertebrfB  and  the  intervertebral  disc.  Lined  above  by  the  synovial  mem- 
branes, this  ligament  is  covered  below  by  the  pleura.  (Loyh  inchides  a 
capsular  ligament  for  the  head  of  the  rib  and  another  for  the  costal 
tuberosity.  He  probably  viewed  the  synovial  membrane  of  these  articula- 
tions as  such.) 

Synovial  membranes. — Two  in  number,  these  are  distinguished  into 
anterior  and  posterior,  lying  against  each  other,  and  separated  in  part 
by  the  interarticiilar  ligament  they  cover.  Supported  below  by  the  stellate 
ligament,  above  they  are  directly  in  contact  with  the  small  supercostal 
muscles,  and  with  vessels  and  nerves. 

CosTO-TRANSVERSE  ARTICULATIONS. — Articular  surfaces. — In  the  rib,  the 
diarthrodial  facet  cut  on  the  tuberosity.  In  the  vertebra,  the  analogous 
facet  on  the  outside  of  the  transverse  process. 

Mode  of  union. — Two  ligaments  bind  this  articulation  :  1,  The  posterior 
costo-transverse  ligament  (Fig.  83,  4),  a  white  fibrous  band  attached  by  its 
extremities  behind  the  tranverse  process  and  the  costal  tuberosity,  lined  by 
synovial  membrane,  and  covered  by  the  transverse  insertions  of  several 
spinal  muscles ;  2,  The  anterior  costo-transverse,  or  interosseous  ligament 
(Fig.  83,  3),  a  fasciculus  of  short,  thick,  white  fibres,  fixed  on  the  anterior 
siu'face  of  the  transverse  process  near  its  base,  and  in  the  rugged  excavation 
on  the  neck  of  the  rib.  This  ligament  is  invested,  posteriorly,  by  the 
synovial  membrane,  and  covered  in  front  by  pads  of  adipose  tissue  which 
separate  it  from  the  costo-vertebral  articulation. 

Synovial  membrane. — This  is  a  small  particular  capsule  kept  apart  from 
the  posterior  synovial  membrane  of  the  costo-vertebral  articulation  by  the 
costo-transverse  interosseous  ligament. 

Characters  peculiar  to  some  Costo-vertebral  Articulations.— 
1.  The  first,  and  sometimes  the  second,  costo-vertebral  articulation  has  no 
interosseous  ligament,  and  only  exhibits  one  synovial  membrane.  The 
intervertebral  cavity  which  concurs  in  forming  the  first  is  often  excavated 
between  the  last  cervical  and  first  dorsal  vertebrae. 

2.  The  two  or  three  last  costo-transverse  articulations  are  confounded 
with  the  corresi)ondiug  costo-vertebral  joints.  They  have  no  proper  serous 
membrane,  but  the  posterior  synovial  membrane  of  the  latter  is  prolonged 
around  their  articular  surfaces. 

2.   The  Chondro-sternal  or  Costo-sternal  Articulations. 

{Preparation. — To  show  the  articulation  of  the  ribs  with  the  cartilages,  these  with 
the  sternum,  and  the  cartilages  with  each  other,  carefully  remove  the  pleura,  the 
triangular  muscle  of  the  sternum,  the  diaphragm,  the  transverse  muscle  of  the  abdomen, 
then  the  pectorals,  the  great  oblique,  the  transversalis  of  the  ribs,  and  the  intercostal 
muscles.) 

The  first  eight  ribs,  in  resting  upon  the  sternum  by  the  inferior  extremity 
of  their  cartilages,  form  eight  similar  arthrodial  articulations. 

Articular  surfaces. — Each  sternal  cartilage  opposes  to  one  of  the  lateral 
cavities  of  the  sternum  the  convex  and  oblong  facet  at  its  lower  extremity. 

Mode  of  union.— The  diarthrosis  resulting  from  the  union  of  these  two 
surfaces  is  enveloped  everywhere  by  bundles  of  white,  radiating,  fibrous 
tissue,  which  constitute  a  veritable  ligamentous  capsule.  The  superior  part 
of  this  capsule,  known  as  the  stellate  or  superior  costo-sternal  ligament,  is 
covered  by  the  triangular  (sterno-costalis  internus)  muscle ;  it  is  joined 
.to  a  fibrous  cord  lying  on  the  superior  face  of  the  sternum,  and  which 


112  THE  ARTICULATIONS. 

is  confounded  in  front  with  that  of  the  opposite  side.  The  inferior 
portion,  the  inferior  stellate  or  costo-sternal  ligament,  is  in  relation  with. the 
pectoral  muscles. 

Si/novial  capsule. — There  is  one  for  each  articulation. 

Characters  proper  to  the  first  costo-sternal  articulation. — The  first  costo- 
sternal  articulation  is  not  separated  from  its  fellow  of  the  opposite  side  ;  so 
that  these  two  joints  are,  in  reality,  only  one,  and  the  two  cartilages  lying 
close  to  each  other  cori-espond  by  a  small  diarthrodial  facet,  continuous  with 
that  for  the  sternum.  The  two  sternal  facets  are  inclined  upwards,  and 
confounded  with  one  another.  Only  one  synovial  cavity  exists  for  this 
complex  articulation,  which  unites  the  two  first  ribs  to  each  other  and  to  the 
sternum. 

3.  Chrondo-costal  Articulations  uniting  the  Bibs  to  their  Cartilages. 

These  are  synarthrodia!  articulations  whose  movements  are  very  obscure. 
They  are  formed  by  the  imi^lantation  of  the  cartilages  in  the  rugged  cavities 
the  ribs  present  at  their  inferior  extremities.  The  solidity  of  these  articu- 
lations is  assured  by  the  adherence  of  the  fibro-cartilage  to  the  proi)er 
substance  of  the  ribs,  and  by  the  periosteum  which,  in  passing  from  the 
bone  to  the  cartilage,  plays  the  part  of  a  powerful  peripheral  band. 

In  the  Ox,  the  sternal  ribs,  in  uniting  with  their  cartilages,  form  a  veritable 
ginglymoid  diarthrosis,  whose  movement  is  facilitated  by  a  small  synovial  cai^sule. 

4.  Articulations  of  the  Costal  Cartilages  with  each  other. 

The  ribs,  attached  to  each  other  by  means  of  the  intercostal  muscles,  are 
not  united  by  real  articulations ;  neither  are  their  cartilages  of  prolougment. 
But  the  asternal  cartilages  are  bound  together  by  a  small  yellow  elastic 
ligament,  which  is  carried  from  the  free  extremity  of  each  to  the  posterior 
border  of  the  preceding  cartilage  ;  the  anterior  border  of  the  first  asternal 
cartilage  is  directly  united  to  the  posterior  border  of  the  last  sternal  cartilage, 
through  the  medium  of  the  perichondrium  and  very  short  ligamentous  bands. 
Tliis  same  asternal  cartilage  is  also  bound  to  the  inferior  face  of  the  xiphoid 
appendage  by  a  small  white  ligament  (the  chondro-xiphoid),  under  which 
passes  the  anterior  abdominal  artery. 

5.  Sternal  Articulation  peculiar  to  the  Ox  and  Pig. 

It  has  been  already  shown  that  in  tliese  animals  the  anterior  piece  of  the  sternum  is 
not  consolidated  with  the  second  portion.  The  two  are  united  by  a  diarthrodial 
articulation ;  and  for  this  purpose  the  anterior  presents  a  concave  surface,  the  posterior 
a  convex  one.  Bundles  of  peripheral  fibres  firmly  bind  them  to  each  other,  and  a  special 
small  synovial  capsule  facilitates  their  movements,  which  are  very  limited. 

6.  The  Articulations  of  the  TJiorax  considered  in  a  general  manner  in  regard  to 

Movements. 

The  thorax  can  increase  or  diminish  in  diameter  in  an  antero-posterior 
and  a  transverse  direction ;  whence  arises  the  dilatation  and  contraction 
of  this  cavity :  the  inspiratory  movements  accompanying  the  entrance  of  the 
external  air  into  the  kings,  and  the  expiratory  movements  expelling  the  air 
contained  in  these  organs. 

The  variations  in  the  antero-posterior  diameter  of  the  chest  being  due  to 
changes  in  the  figure  of  the  diaphragm,  need  not  be  noticed  here.  But  the 
transverse  variations  being  the  result  of  the  play  of  the  costal  arches  on  the 


ABTICULATIOXS  OF  THE  ASTERIOR  LUIBS.  143 

spine  and  sternum,  it  is  advantageous  to  study  the  mechaiiism  whicli  presides 
in  the  execution  of  their  movements. 

The  costal  arches  being  inclined  backwards  on  the  middle  plane,  the 
space  they  inclose  in  their  concavity  is  not  nearly  so  extensive  as  if  they 
had  been  perpendicular  to  this  plane.  Owing  to  their  double  arthrodial 
joints,  the  ribs  are  movable  on  the  spine,  and  their  inferior  extremity,  also 
movable,  rests  either  directly  or  indirectly  on  the  sternum.  Therefore  it  is 
that,  when  they  are  drawn  forward  by  their  middle  portions,  they  pivot  on 
their  extremities,  and  tend  to  assume  a  perpendicuhir  direction,  which  is  the 
most  favoui-able  for  the  largest  increase  of  the  space  they  limit ;  then  there 
is  enlargement  of  the  lateral  diameter  of  the  thorax,  which  signifies  dilatation 
of  its  cavity.  The  inverse  movement,  by  an  opposite  mechanism,  causes 
the  contraction  of  the  chest. 

The  ribs  are  said  to  be  elevated  during  the  forward  movement,  and 
depressed  when  they  fall  backwai'ds.  These  expressions,  though  perfectly 
applicable  to  Man,  who  stands  in  a  vertical  position,  are  not  correct  when 
employed  in  veterinary  anatomy. 

AbTICLE    IY. — APvTICrLATIOXS    OF    THE    AXTERIOR   LlMBS. 

1.  Scapula-humeral  Articulation. 

{Preparation. — ^Detach  the  limb  from  the  trunk.  Eemove  from  the  upper  extremity 
those  muscles  whicli  are  inserted  in  the  vicinity  of  the  glenoid  cavity  of  the  scapula ; 
turn  down  from  its  lower  extremity  those  which  are  inserted  into  the'  superior  end  of 
the  humerus  or  a  little  below,  preserving  the  attachments  of  their  tendons  with  the 
capsular  hgament.  The  thin  scapulo-humeralis  muscle  may  be  allowed  to  remain  in 
order  to  show  its  relations.) 

To  constitute  this  enarthrodial  articulation,  the  scapula  is  united  to  the 
humerus,  and  forms  an  obtuse  angle  which  is  open  behind. 

Articular  surfaces. — In  the  scapula  there  is  the  glenoid  cavity,  the 
shallow,  oval  fossa,  elongated  in  an  antero-posterior  direction,  notched  in- 
wardly, and  excavated  at  its  centre  or  near  the  internal  notch  by  a  small  synovial 
fossette.  A  ligamentous  band,  attached  to  the  brim  of  the  cavity,  tills  up 
this  notch,  and  is  the  vestige  of  the  glenoid  ligament  of  man.  In  the 
humerus,  the  articular  head,  fixed  between  the  large  and  small  tuberosities, 
is  often  excavated  by  a  shallow  synovial  fossette. 

Mode  of  union. — One  capsular  ligament  (Fig.  85,  1),  a  kind  of  sac  having 
two  openings :  one  inferior,  embracing  the  head  of  the  humerus ;  the 
superior,  inserted  into  the  mai'gia  of  the  glenoid  cavity.  This  capsule  pre- 
sents in  front  two  supporting  fasciculi,  which  diverge  as  they  descend  from 
the  coracoid  process  to  the  great  and  small  tuberosities.  The  aponeurotic 
expansion  thus  formed  is  very  thin  and  loose,  so  as  to  allow  the  two  bones  to 
separate  to  the  extent  of  from  yt-  to  y%  of  an  inch ;  but  it  is  far  from 
being  sufficiently  strong  to  bind  them  fii-mly  together.  The  articulation  is, 
therefore,  consolidated  by  the  powerful  muscles  which  surround  it,  among 
which  may  be  noticed:  1,  In  front,  the  coraco-radial  (flexor  brachii  i, 
separated  from  the  fibrous  capsule  by  an  adipose  cushion  ;  2,  Behind,  the 
large  extensor  of  the  fore-arm  and  thin  scapulo-humeral  (teres  minor) 
muscles,  whose  office  appears  to  be  to  pull  up  this  capsule  during  the  move- 
ments of  flexion,  so  as  to  prevent  its  being  pinched  between  the  articular 
surfaces ;  3,  Outwards,  the  short  abductor  of  the  arm  and  the  subspinous 
(postea  spinatus  j  tendon ;  ■!,  Inwards,  the  wide  and  strong  tendon  of  the 
subscapular  muscle.      In  addition  to  these  powerful   retaining   appai-atus, 


144  THE  ABTICULATIONS. 

there  is  the  atmospheric  pressure,  whose  influence  is  of  a  certain  impor- 
tance. This  may  be  proved  by  removing  all  the  surrounding  muscles,  when 
it  will  be  found  that  the  capsule  is  not  relaxed,  nor  are  the  articular  surfaces 
separated ;  to  etfect  this,  it  is  necessary  to  make  an  opening  in  the  capsule, 
so  as  to  allow  the  air  to  enter  its  cavity,  when  the  surfaces  immediately 
separate. 

Synovial  capsule. — This  is  very  loose,  and  entirely  enveloped  by  the 
peripheral  capsule,  whose  internal  surface  it  lines. 

Movements. — Like  all  the  enarthrodial  articulations,  the  scapulo-humeral 
permits  extension,  flexion,  abduction,  adduction,  circumduction,  and  rotation. 
These  various  movements,  however,  are  far  from  being  so  extensive  as  in 
Man,  the  arm  in  the  domesticated  animals  not  being  detached  from  the 
trunk,  but  being,  on  the  contrary,  fixed  with  the  shoulder  against  the  lateral 
parietes  of  the  thorax.  Flexion  and  extension  are  the  least  limited  and  the 
most  frequently  repeated  movements;  their  execution  always  demands  a 
displacement  of  the  two  bones,  which  are  almost  equally  movable.  Inflexion, 
the  scapulo-humeral  angle  is  closed,  not  only  because  the  inferior  extremity 
of  the  humerus  is  carried  backwards  and  upwards,  but  also  because  the 
scapula  pivots  on  its  superior  attachments  in  such  a  manner  as  to  throw  its 
glenoid  angle  forward  and  upward.  Extension  is  produced  by  an  inverse 
mechanism.  During  the  execution  of  the  other  movements,  the  scapula 
remains  fixed,  and  the  humerus  alone  is  displaced,  bringing  with  it  the 
inferior  rays  of  the  limbs.  If  it  is  carried  outwards,  we  have  abduction^ 
or  inwai'ds,  addaction  ;  if  the  member  passes  successively  from  flexion  to 
abduction,  anil  from  that  to  extension,  etc.,  in  describing  a  circle  by  its 
lower  extremity,  then  there  is  circumduction ;  if  it  pivots  from  left  to  right, 
or  right  to  left,  we  have  rotation. 

In  the  Plfi,  Doj,  and  Cat,  the  synovial  membrane  is  not  exactly  inclosed  by  the 
fibrous  capsule,  but  forms  in  front  a  cul-de-sac,  which  descends  in  the  bicipital  groove  to 
favour  the  gliding  of  the  coraco- radial  tendon. 

In  Man,  the  scapulo-humeral  articulation  is  disposed  as  in  animals,  but  it  is  also 
protected  above  by  the  coraco -acromion  roof.  For  the  reasons  noted  above,  this 
articulat'on  allows  of  more  extensive  motion  tlian  in  animals.  As  remarked  by 
Cruveilhier,  of  all  the  joints  in  the  human  body,  the  scapulo-humeral  is  that  which  has 
the  most  extensive  motion;  in  movements  forward  and  outward,  the  humerus  can 
become  horizontal;  in  those  of  circumduction  it  describes  a  comj^lete  cone,  which  is 
more  extensive  in  front  and  laterally  than  behind  and  inwardly. 

2.   Kumero-radial,  or  Elboiv  Articulation. 

(Preparation. — Turn  down  the  inferior  extremity  of  the  flexors  of  the  fore-arm, 
remove  the  olecranian,  epicondyloid,  and  epitrochlean  muscles,  taking  care  not  to 
damage  the  ligaments  to  which  they  somewhat  closely  adhere.) 

Three  bones  concur  to  form  this  articulation,  which  presents  a  remark- 
able example  of  an  angular  ginglymus  :  the  hinnerus,  by  its  inferior  ex- 
tremity, and  the  two  bones  of  the  arm  by  their  upper  extremities. 

Articular  surfaces. — The  humeral  surface,  already  described  at  page  74, 
is  transversely  elongated,  and  convex  from  before  to  behind.  It  jiresents  : 
1,  A  median  groove  excavated  by  a  synovial  fossette  ;  2,  An  external  groove 
(humeral  trochlea)  not  so  deep  as  the  preceding ;  3,  A  kind  of  voluminous 
condyle  which  borders,  inwardly,  the  internal  pulley,  and  whose  antero- 
posterior diameter  is  much  greater  than  that  of  the  external  lip  of  the 
trochlea  of  the  opposite  side.  The  antibracJiicd  surface,  divided  into  two 
portions,  is  moulded  to  the  humeral  surface  ;  it  is,  therefore,  concave  before 
and  behind,  and  is  composed :  1,  Of  a  double  external  groove ;  2,  Of  an 


ARTICULATIONS  OF  TEE  ANTERIOR  LIMBS. 


145 


Fi2.  85. 


internal  glenoid  cavity,  both  excavated,  on  the  superior  extremity  of  the 
radius  ;  3,  A  middle  ridge  re- 
sponding to  the  middle  groove 
of  the  humerus,  separating  the 
two  preceding  sm-faces,  and 
prolonged  on  the  ulnar  beak, 
where  it  forms  the  sygmoid 
notch.  This  ridge  shows  a 
small  synovial  fossette  hol- 
lowed out  on  the  radius  and 
ulna. 

Mode  of  union. — Three 
ligaments  :  two  lateral  and  an 
anterior. 

a.  The  external  lateral  liga- 
ment (Fig.  85,  8)  is  a  thick, 
short,  and  strong  funicle,  at- 
tached above  to  the  crest  limit- 
ing outwardly  and  posteriorly 
the  furrow  of  torsion,  and  in 
the  small  cavity  placed  at  the 
external  side  of  the  humeral 
articular  surface.  Below,  it  is 
inserted  into  the  supero-ex- 
ternal  tuberosity  of  the  radius. 
Its  anterior  border  is  con- 
founded with  the  capsular  liga- 
ment, and  is  margined  by  the 
principal  extensor  of  the  pha- 
langes, which  derives  from  it 
numerous  points  of  attach- 
ment. By  its  posterior  border 
it  is  in  contact  with  the  ex- 
ternal flexor  of  the  metacarpus. 
Its  internal  face   is  lined  by 

synovial   membrane,    and    its 
external  face  is  only  separated 

from   the    skin   by   the    anti- 

brachial  aponeurosis  and  some 

of  the  fasciculi  from  the  origin 

of  the  lateral  extensor  muscle 

of  the  phalanges.     Its  super- 
ficial fibres  are  vertical,  and  are 

continuous,   behind,  with   the 

arciform     ligamentous    bands 

which  stretch  from  the  ulna  to 

the  radius.     Its  deep  fibres  are 

slightly    oblique     downwards 

and  forwards. 

h.  The  lateral  internal  liga- 
ment, also  funicular,  is  longer, 


scapitlo-hujieral  and  hu5ier0-radial  aeticxt- 
latioxs,  with  the  muscles  surrounding  them 
(external  face). 

1,  Scapulo-humeral  capsular  ligament ;  2,  Short  ab- 
ductor muscle  of  the  arm ;  3,  Its  insertion  in  the 
humerus;  4,  Insertion  of  the  subspinous  muscle 
on  the  crest  of  the  great  tuberosity ;  5,  Coraco- 
radial  muscle;  6,  Its  tendon  of  origin  attached  to 
the  coracoid  process;  7,  Its  radial  insertion  con- 
founded with  the  anterior  ligament  of  the  ulnar 
articulation ;  8,  8,  External  lateral  ligament  of  that 
articulation;  9,  Anterior  ligament ;  10,  Aconeus,  or 
small  extensor  of  the  fore-arm;  11,  Origin  of  the 
external  flexor  muscle  of  the  metacarpus  ;  12,  Short 
flexor  muscle  of  the  fore-arm. — A,  Tuberosity  or 
the  scapular  spine. — B,  Superspmous  fossa. — C,  Sub- 
spinous fossa. — D,  Convexity  of  the  small  trochan- 
ter.— E,  Summit  of  the  trochanter. 


but  not  SO  strong  as  the  pre- 
ceding.    It    arises  from   the   small  tuberosity   on  the  inner   side    of  the 


146  THE  ARTICULATIONS. 

superior  articular  face  of  the  humerus  and,  widening  as  it  descends,  reaches 
the  radius.  Its  median  fibres,  which  are  the  longest,  are  directed  vertically 
downwards  to  reach  the  imprints  situated  below  the  bicipital  tuberosity ; 
its  anterior  fibres,  curved  forwards,  are  united  to  the  tendon  of  the  coraco- 
radial  muscle,  or  are  confounded  with  the  anterior  ligament ;  the  posterior 
are  turned  backwards,  near  their  inferior  extremities,  to  join  the  arcifurm 
fibrous  fasciculi  which  inwardly  unite  the  ulna  to  the  radius.  The  middle 
fibres  of  this  ligament  cover  the  inferior  insertion  of  the  short  flexor  of  the 
fore-arm  and,  in  part  only,  that  of  the  long  flexor.  It  is  covered  by  the 
ulna-plantar  nerve  and  the  posterior  radial  artery  and  vein. 

c.  The  anterior  or  capsular  ligament  (Fig.  85,  9)  is  a  membraniform  band, 
attached  by  its  superior  border  above  the  humeral  articular  surface,  and  by 
its  inferior  to  the  anterior  margin  of  the  radial  surface.  By  its  lateral 
borders,  it  is  confoimded  with  the  funicular  ligaments.  Its  internal  half 
is  formed  of  vertical  fibres  which  descend  from  the  humerus  and  expand 
over  the  radius,  where  they  become  united  with  the  inferior  tendon  of  the 
coraco-radial  muscle.  In  its  external  moiety  it  is  extremely  thin,  and 
composed  of  fibres  crossed  in  various  directions.  Lined  internally  by 
synovial  membrane,  this  ligament  is  in  contact,  by  its  external  surface,  with 
the  anterior  radial  vessels  and  nerves,  the  two  flexor  muscles  of  the  fore-arm, 
the  anterior  extensor  of  the  metacarpus,  and  anterior  extensor  of  the 
phalanges.  The  two  latter  muscles  are  even  attached  to  it  in  a  very  evident 
manner.  The  elbow  articulation,  closed  in  front  and  on  the  sides  by  the 
three  ligaments  just  described,  has  no  particular  ligaments  posteriorly  ;  but 
it  is  powerfully  consolidated  there  by  the  olecranian  insertion  of  the  extensor 
muscles  of  the  fore-arm,  and  by  the  tendons  of  origin  of  the  five  flexor 
muscles  of  the  metacarpus  or  phalanges. 

Synovial  membrane.— Thin  membrane  is  very  extensive  and,  stretched 
out  on  the  internal  face  of  the  before-mentioned  ligaments,  forms  behind 
three  great  culs-de-sac  of  prolongment :  a  superior,  occupying  the  olecranian 
fossa,  and  covered  by  a  fatty  cushion,  as  well  as  by  the  small  extensor 
muscle  of  the  fore-arm  ;^  two  lateral,  which  descend  from  each  side  of  the 
ulnar  beak,  and  are  distinguished  as  internal  and  external ;  the  first  lines 
the  tendon  of  the  external  flexor  of  the  metacarpus  ;  the  second  facilitates 
the  play  on  the  upper  radial  extremity  of  the  four  flexor  muscles  of  the  foot 
or  dibits,  and  which  are  attached  in  common  to  the  epitrochlea.  This  synovial 
sac  also'  furnishes  the  radio-ulnar  articulation  with  a  diverticulum  which 
descends  between  the  bones  of  the  fore-arm  to  below  the  adjacent  diar- 
throdial  facets. 

Movements. — Flexion  and  extension. 

In  flexion,  the  two  bones  do  not  approach  each  other  directly,  the  inferior 
extremity  of  the  radius  deviating  a  little  outwards.  This  is  due  more  to 
the  slight  obliquity  of  the  articular  grooves  than  to  the  difference  in 
thickness  existing  between  the  external  and  internal  extremities  of  the 
humeral  surface. 

Extension  is  limited  by  the  reception  of  the  beak  of  the  olecranon  in  its 
fossa,  and  by  the  tension  of  the  lateral  ligaments ;  so  that  the  two  rays 
cannot  be  straightened  on  one  another  in  a  complete  manner,  or  placed  on 
the  same  line. 

In  the  Dog  and  Cat,  the  external  lateral  ligament  is  very  thick,  and  forms  in  its 

>  Some  grey  elastic  fibres  wliich  cover  this  cul-de-sac  externally,  have  been  wrongly 
described  as  a  posterior  membraniform  ligament. 


ARTICULATIONS  OF  THE  ANTERIOR  LIMBS.  147 

inferior  moiety  a  fibro-cartilaginous  cap  which  is  fixed  on  the  ulna  and  radius,  and  united 
in  trout  to  tlie  annular  ligament  of  the  superior  radio-ulnar  joint.  This  cap,  with  the  last- 
named  ligament,  complcti  s  the  osteo-fibrous  ring  iu  which  the  superior  extremity  of  the 
radius  turns.  The  internal  lateral  ligament  is  inserted  by  two  very  short  fasciculi  into 
the  ulna  and  inner  side  of  the  head  of  the  radius.  A  third  fasciculus,  deeper  and  median, 
much  more  developed  than  tlie  first,  and  covered  by  the  inferior  insertion  of  the  flexors 
of  the  fore-arm,  descends  between  the  radius  and  ulna  to  tlie  posterior  face  of  the 
former,  and  is  there  inserted  near  the  inferior  attachment  of  the  external  ligament, 
whicii  it  appears  as  if  about  to  join. 

In  Man.  tiie  elbow  articulation  is  formed  nearly  on  the  same  plan  as  that  of  the  Dog 
and  Cat.  The  radius  and  ulua  move  together  when  the  fore-arm  is  flexed  and  extended 
on  the  humerus. 

3.  Badio-iilnar  Articulation. 

Articular  surfaces. — The  two  bones  of  the  fore-arm  correspond  by 
diartliroclial  and  synarthrodia!  surfaces. 

a.  The  diarthrudial  surfaces  consist  of*  four  undulated,  transversely 
elongated  facets,  two  of  which  are  radial  and  two  ulnar.  The  first  border, 
posteriorly,  the  great  articulai*  surface  forming  the  elbow  joint ;  the  second 
are  situated  beneath  the  sigmoid  notch. 

h.  The  synartkrodial  surfaces  are  plane  and  roughened,  and  are  also  two 
on  each  bone :  one,  superior,  extends  below  the  diarthrudial  facets  to  the 
radio-ulnar  arch ;  the  other,  inferior,  more  extensive,  occupies  all  the 
anterior  face  of  the  ulna  frnm  this  arch ;  on  the  radius  it  forms  a  very 
elongated  triangular  imprint  which  descends  to  the  lower  fourth  of  the  bone. 
See  pages  75,  76. 

Mode  of  union. — Two  interosseous  and  two  peripheral  ligaments. 

a.  The  interosseous  ligaments,  interposed  between  the  syuarthrodial 
surfaces,  are  composed  of  extremely  short  white  fibres  passing  from  one  to 
the  other  surface,  and  which  are  endowed  with  a  very  remarkable  power 
of  resistance.  The  inferior  always  ossifies  a  long  time  before  the  animal 
is  full  grown  :  a  circumstance  which  caused  the  older  veterinary  anatomists 
to  describe,  and  with  some  show  of  reason,  the  radius  and  ulna  as  a  single 
bone.     Ossification  of  the  superior  ligament  is  very  rare. 

6.  The  peripheral  bands  are  bundles  of  arciform  fibres  which,  from  the 
beak  of  the  olecranon  to  the  radio-ulnar  arch,  leave  the  lateral  faces  of 
the  ulna  to  pass,  some  inwards,  others  outwards,  to  the  posterior  face 
of  the  radius.  The  fibres  of  the  external  ligament  are  confounded  with  the 
external  humero-radial  ligament.  The  internal  fibres  are  united  to  the 
internal  hiunero-radial  ligament,  and  to  the  small  ulnar  tendon  belonging 
to  the  short  flexor  of  the  tore-ann.  Analogous  fibres  are  found  beneath  the 
radio-ulnar  arch ;  but  they  are  much  shorter  and  less  apparent  (This  is 
the  externcd  transverse  radio-ulnar  ligament  of  Leyh.) 

Movements. — Very  obscure  in  youth ;  nearly  null  when  consolidation  of 
the  two  bones  takes  place. 

In  the  Ox,  ossification  of  the  superior  interosseous  ligament  is  constant  at  adult 
age. 

In  the  Dog  and  Cat,  we  have  already  seen  fp.  87)  that  the  radius  and  ulna  are  not 
fused  to  each  other,  but  remain  independent  during  life.  They  are  united  in  their 
middle  portion  by  an  interosseous  ligament,  and  join  by  diarthrosis  at  their  two 
extremities.  These  animals  therefore  exhibit:  1,  An  interosseous  ligament,  2,  A 
superior  radio-ulnar  articulation ;  3,  An  inferior  radio-ulnar  articulation. 

Interosseous  ligament. — It  is  composed  of  very  resisting  white  fibres,  attached  by 
their  extremities  to  the  bodies  of  the  bones.  Notwithstanding  their  shortness,  they  are 
loose  enough  to  allow  movements  talking  place  between  tlie  radio-ulnar  articulations. 

Superior  radio-ulnar  artindalion. — This  is  a  trochoid  articulation,  which  only  allows 
movements  of  rotation  or  pivoting. 


148  THE  ARTICULATIONS. 

The  articular  surfaces  which  form  this  articulation  are:  in  the  ulna,  the  small 
sigmoid  cavity,  a  surface  excavated  in  the  lateral  sense,  and  semicircular ;  in  the  radius, 
a  cylindi'ical  half-hinge  received  into  the  preceding  cavity. 

To  unite  these  there  is  an  annular  ligament,  a  kind  of  fibrous  web  thrown  around 
the  superior  extremity  of  the  radius,  lixed  inwardly  on  the  ulna  near  the  inner 
extremity  of  the  small  sigmoid  cavity,  attached  outwardly  to  the  external  lateral 
ligament  of  the  elbow  articulation,  and  confounded  superiorly  with  the  anterior 
ligament  of  the  same  articulation.  Tliis  fibrous  web,  in  uniting  with  tlie  fibro- 
cartilaginous cap  of  the  external  humero-radial  ligament,  and  joining  the  small  sigmoid 
cavity  by  its  internal  extremity,  transforms  this  last  into  a  complete  ring,  covered  with 
cartilage  in  its  bony  portion,  and  lined  by  synovial  memijraue — that  of  the  elbow 
articulation — in  its  ligamentous  portion.  The  liead  or  superior  extremity  of  the  radius 
is  also  incrusted  over  its  entire  contour  with  a  layer  of  cartilage :  a  disposition  which 
permits  it  to  glide  not  only  in  the  concave  face  of  the  small  sigmoid  cavity,  but  also  on 
the  internal  face  of  the  two  ligaments  which  complete  this  cavity. 

Inferior  radio-ulnar  articulation. — This  is  also  a  trochoid  articulation  analogous  to 
the  preceding,  but  inversely  disposed.  Thus,  the  concave  articular  surface  is  hollowed 
on  the  radius,  outside  the  inferior  extremity ;  the  convex  surface  lies  within  the  ulna. 
These  two  facets  are  very  small,  and  are  maintained  in  contact  by  a  diminutive 
peiiplieral  fibrous  capsule.  A  strong  interosseous  ligament,  situated  imder  the 
articular  facets,  also  consolidates  this  diarthrosis,  and  concurs  by  its  inferior  border  to 
form  the  antibrachial  surface  of  the  radio-cari:)al  articulation.  A  small  synovial 
capsule  is  specially  devoted  to  this  articulation. 

Mechanism  of  the  radio-ulnar  joints. — The  play  of  these  two  articulations  is 
simultaneous,  and  tends  to  the  ?ame  end;  that  is,  to  the  execution  of  the  double 
rotatory  movement  which  constitutes  supination  and  pronation. 

Sujrination  is  when  the  ulna  remains  fixed,  and  the  radius  pivots  on  it  in  such  a 
manner  as  to  carry  its  anterior  face  outwards.  Its  superior  extremity  then  turns  from 
within  forwards,  and  even  from  before  outwards  if  the  movement  is  exaggerated,  in  the 
articular  girdle  formed  by  the  small  sigmoid  cavity  of  the  ulna  and  the  ligaments  which 
complete  it.  The  inferior  extremity  also  rolls  on  the  ulnar  facet  in  describing  a  similar 
movement,  and  the  internal  tuberosity  of  this  extremity  is  carried  forwards. 

In  the  movement  of  pronation,  this  tuberosity  is  brought  inwards,  and  the  anterior 
face  of  the  radius  comes  forward  by  an  opposite  mechanism. 

The  inferior  ray  of  the  anterior  member  being  articulated  in  a  hinge-like  manner 
with  the  radius,  it  follows  that  bone  in  its  rotatory  movements,  the  anterior  face  of  the 
metacarpus  looking  outwards  during  supination  and  forwards  in  pronation. 

The  radio-ulnar  articulation  in  Man  resembles  that  of  the  Dog  and  Cat,  the  articular 
surfaces  only  being  larger  and  the  movements  more  extensive.  In  supination,  tlie 
palmar  face  is  turned  forward,  and  the  radius,  situated  on  the  outer  side  of  the  ulna,  is 
in  the  same  direction  as  the  latter.  In  pronation,  on  the  contrary,  the  palmar  face  of 
the  hand  looks  backwards,  and  the  radius,  remaining  outwards  in  its  upper  part,  crosses 
the  ulna  in  front  in  such  a  manner  that  its  lower  extremity  is  placed  within  the  ulna. 

4.  Articulations  of  the  Carpus. 

(Preparation. — Kemove  the  tendons  from  around  the  articulation,  detaching  their 
sheaths,  but  taking  care  of  the  ligaments.) 

These  comprise :  1,  The  articulations  uniting  the  carpal  bones  of  the 
first  row  to  each  other ;  2,  The  analoszous  articulations  of  the  second  row ; 
3,  The  radio-carpal  articulation  ;  4,  The  articulation  of  the  two  rows  with 
each  other  ;  5,  The  carpo-metacarpal  articulation. 

Akticulations  which  unite  the  Bones  of  the  First  Eow  to  each 
OTHEU. — These  bones,  four  in  number,  are  joined  by  the  diarthi'odial  facets 
on  their  lateral  faces  and  form  small  arthrodial  articulations.'^  They  are 
maintained  in  contact  by  sis  ligaments,  three  anterior,  and  three  interosseous. 
The  anterior  ligaments  are  small  flattened  bands  carried  from  the  fourth  bone 
to  the  first,  from  the  first  to  the  second,  and  from  that  to  the  third.  The 
first,  placed  outside  rather  than  in  front  of  the  carpus,  is  covered  by  the 

'  The  facet  uniting  the  supercarpal  to  the  first  bone  is  not  situated  on  one  of  its 
faces,  but  rather  on  the  anterior  part  of  its  circumference. 


ARTICULATIONS  OF  THE  ANTERIOR  LIMBS.  149 

external  lateral  ligament  and  the  inferior  tendon  of  the  external  flexor  of 
the  metacurpui? ;  the  others  adhere  to  the  eapsidur  ligament.  The  inter- 
osseous lujaments  are  implanted  in  the  grooves  of  insertion  which  separate 
the  diarthrodial  facets.  One  of  them,  derived  from  the  common  superior 
ligament,  unites  the  first  to  the  second  bone.  The  two  others,  situated 
between  the  three  last  carpal  bones,  are  confounded  with  the  corresponding 
anterior  ligaments. 

Articulations  uniting  the  Carpal  Bones  of  the  Second  Eow. — 
These  are  arthrodial  articulations,  like  the  preceding,  but  numbering  only 
two.  Tliey  are  fixed  by  tivo  ankrior  and  two  interosseous  ligaments.  One  of 
the  anterior  ligaments  joins  the  first  bone  to  the  second,  and  strongly  adheres 
to  the  capsular  ligament ;  the  other  is  entirely  covered  by  the  lateral  internal 
ligament,  and  attaches  the  two  last  bones  to  each  other.  Of  the  two  inter- 
osseous ligaments,  the  second  alone  is  confounded  with  the  corresponding 
anterior  ligament.  That  which  is  situated  between  the  two  first  bones  is 
separated  from  the  anterior  ligament  by  one  of  the  diarthrodial  facets  between 
these  bones. 

Eadio-carpal  Articulation. — The  inferior  extremity  of  the  radius,  in 
becoming  united  to  the  upper  row  of  carpal  bones,  constitutes  a  diarthrosis 
which,  from  the  nature  of  the  movements  it  permits,  may  be  considered  as 
an  imperfect  hinge  joint. 

Articular  surfaces. — The  radial  surface,  elongated  transversely  and  very 
irregular,  presents :  1,  Outwardly,  a  wide  groove,  limited  in  front  by  a 
small  glenoid  cavity,  and  bounded,  posteriorly,  by  a  non-articular  excavation 
which  receives  a  prolongation  of  the  second  bone  in  the  movement  of  flexion  , 
2,  Inwardly,  a  condyle,  with  a  more  extensive  curvature  than  that  of  the 
preceding  groove  and,  like  it,  completed  by  a  small  anterior  glenoid  cavity. 
The  carj)al  surface,  moulded  exactly  on  tLe  radial,  oifers  depressions  corre- 
sponding to  the  projections  on  it,  and  vice  versci. 

3Iode  of  union. — The  radio-carpal  articulation  is  bound  by  three  liga- 
ments which  entirely  belong  to  it,  and  by  four  strong  ligaments  that  are 
common  to  it  and  articulations  which  will  be  studied  hereafter. 

Of  the  three  ligaments  proper  belonging  to  the  radio-carpal  articulation, 
one  forms  a  thick,  rounded  funicle,  extending  from  the  radius  to  the  fourth 
bone  in  an  oblique  direction  downwards  and  inwards,  and  concealed  by  the 
common  posterior  ligament.  The  second  (Fig.  87.  5),  much  smaller,  is 
carried  from  the  supercarpal  bone  to  the  external  side  of  the  inferior 
extremity  of  the  radius,  and  is  partly  covered  by  the  common  external 
ligament.  When  tbe  synovial  capsule  is  distended  by  dropsy,  it  may  form 
a  hernia  at  the  outer  side  of  the  carpus,  by  passing  between  this  small 
ligament  and  the  common  posterior  ligament.  The  third,  very  delicate,  but 
always  present,  is  deeply  situated  beneath  the  last ;  it  is  inserted,  for  one 
part,  into  the  radius  near  the  first  proper  ligament,  and  for  the  other,  into 
the  second  bone  and  the  interosseous  ligament  which  unites  the  supercarpal 
to  the  second  bone. 

Synovial  membrane. — After  lining  these  three  ligaments  and  the  four 
great  ligaments  yet  to  be  described,  this  membrane  is  prolonged  between 
the  three  first  carpal  bones  to  cover  the  superior  face  of  the  interosseous 
ligaments  which  unite  them.  It  even  more  frequently  descends  into  the 
articulation  which  joins  the  supercarpal  to  the  fiirst  bone ;  though  it  also 
sometimes  happens  that  this  has  a  particular  synovial  capsule  of  its  own. 

Articulation   of  the  Two   Rows   between   Each   Other. — Like   the 
preceding,  this  is  an  imperfect  hinge  articulation. 
13 


150 


THE  ARTICULATIONS. 


Ficr.  86. 


Articular  surfaces. — These  are  two,  and  are  both  transversely  elongated, 
very  irregular  in  tlieir  configuration,  and  divided  into  three  portions.  The 
inferior  shows  :  behind,  three  small  condyles  placed  side  by  side ;  in  front, 
two  slightly  concave  facets.  The  superior  corresponds  to  the  first  by  three 
glenoid  cavities  aud  two  convex  facets. 

Mode  of  union. — For  this  articulation,  besides  the  common  great  liga- 
ments, there  are  three  particular  ligaments.  Two  of  these  are  very  short, 
and  are  situated  behind  the  carpus,  underneath  the  great  common  posterior 
ligament.  They  are  readily  perceived  by  removing  the  capsular  ligament, 
and  strongly  flexing  the  carpus.  "  The  strongest  extends  vertically  from 
the  internal  bone  of  the  superior  row  to  the  second  and  third  bones  of  the 
metacarpal  row ;  the  other  descends  obliquely  from  the  first  bone  of  the 
antibrachial  row  to  the  second  of  the  inferior  row," — Bigot.  The  third 
licrament  proper,  much  stronger  than  the  other  two,  reaches  from  the 
supercarpal  to  the  first  bone  of  the  inferior  row  and  the  head  of  the  external 
metacarpal  bone.  It  is  confounded,  outwardly,  with  the  great  external 
lateral  ligament ;  inwardly,  with  the  common  posterior  ligament.  Its 
posterior  border  gives  attachment  to  the  fibrous  arch  which  completes  the 
carpal  sheath.  This  ligament  has  also  a  branch  which  is  fixed  on  the 
second  bone  of  the  upper  row  (Fig.  87,  4). 

Synovial  membrane. — This  lines  all  the  ligaments,  and  is  prolonged 
above  and  below,  between  the  carpal  bones,  to  facilitate 
the  gliding  of  their  articular  facets.  Two  upper  pro- 
longations ascend  between  the  three  first  bones  of  the 
antibrachial  row  to  cover  the  inferior  face  of  the  inter- 
osseous ligaments  uniting  them.  Two  other  prolong- 
ations descend  between  the  carpal  bones  of  the  second 
row ;  the  external,  after  covering  the  first  interosseous 
ligament,  passes  between  it  and  the  corresponding  an- 
terior ligament,  and  communicates  with  the  synovial 
capsule  of  the  carpo-metacarpal  articulation.  The  in- 
ternal forms  a  cul-de-sac  which  rests  on  the  inter- 
osseous ligament 

Caepo-Metacarpal  Articulation. — The  carpal 
bones  of  the  second  row  articulate  with  the  superior 
extremity  of  the  metacarpal  bones,  constituting  a  plani- 
form  diarthrosis. 

Articular  surfaces. — These  are,  on  each  side,  plane 
facets  more  or  less  inclined  one  on  the  another,  and 
continued  between  each  other  The  largest  is  in  the 
carpal  bones  of  each  mifidie,  and  is  generally  hollowed  by  a  small,  shallow, 
row;   2,  2,  Anterior  •   i  i>         xi. 

ligaments  proper  to    Sjnovial  fossette. 

the    carpo-metacar-  Jilode  of  union. — There  are  the  four  great  common 

pal  articulation;  3,   ligaments,  and  also  six  special  ligaments :  two  anterior, 
Common      external   two  posterior,  and  two  interosseous. 

moTinternai    hZ'.      .  P^  *^?^'  ^'''^  anterior  ligaments  (Fig.  86,  2,  2),  one  is 

ment.  divided  into  two  distinct  bands,  and   unites  the  second 

bone  to  the  princij)al  metacarpal ;  the  other,  concealed 

by  the  external  lateral  ligament,  attaches  the  first  bone  to  the  head  of  the 

external  metacarpal  bone. 

The  two  posterior  ligaments  described  by  Rigot  do  not  appear  to  us  to 

be  sufiiciently  distinct  from  the  great  ligament  to  merit  a  sjiecial  description. 

The   two   interosseous    ligaments,   completely   overlooked   by  that   able 


CARPAL  ARTICULA 

TIONS;    FRONT    VIEW. 

1,    1,    Anterior    liga^ 
ments    uniting    the 


ABTICULATIONS  OF  THE  ANTERIOR  LLUBS. 


151 


Ficr.  87. 


anatomist,  start  from  tlie  interstices  which  separate  the  median  metacarpal 
bone  from  the  lateral  metacarpals,  and  join  the  interosseous  ligaments  of  the 
second  row  ;  they  are  thick  and  short.  ^\  e  have  sometimes  noted  one  or 
other  of  them  to  be  absent. 

Synovial  membrane. — This  communicates,  as  indicated  above,  with  the 
synovial  capsule  of  the  preceding  ai-ticulation.  It  furnishes  a  superior  cul- 
de-sac  which  rests  on  the  interosseous  ligament  interposed  between  the  two 
last  carpal  bones  of  the  second  row.  Two  inferior  culs-de-sac  descend  into 
the  intermetacarpal  arthrodial  articulations. 

Ligaments    common    to    the   three    preceding    Articulations.  —  As 
before  mentioned,  these  are  fom*  in  number     two  lateral, 
one  anterior,  and  one  posterior. 

a.  The  external  lateral  ligament  (Figs.  86  and  87,  3)  is  a 
thick  funicular  cord  composed  of  two  orders  of  fibres — a  deep- 
seated  and  a  superficial  order,  slightly  crossed.  It  leaves 
the  external  and  inferior  tuberosity  of  the  radius,  descends 
vertically  to  the  side  of  the  carpus,  transmits  a  fasciculus 
to  the  first  bone  of  the  upper  row,  gives  off  another  fasci- 
culus which  stops  at  the  external  bone  of  the  second  row, 
and  terminates  on  the  head  of  the  corresponding  metacar- 
pal bone.  Traversed  obliquely  by  the  lateral  extensor  of 
the  phalanges,  this  ligament  covers  the  external  carpal 
bones.  In  front,  it  is  united  to  the  capsiilar  ligament; 
near  its  inferior  extremity,  it  is  confounded  with  the  strong 
ligament  which  joins  the  supercarpal  bone  to  the  first  bone 
of  the  inferior  row  and  to  the  head  of  the  external  meta- 
carpal bone. 

h.  The  internal  lateral  ligament  (Fig.  86,  4 ),  analogous  l,  1,  Anterior  liga. 
to  the  preceding  and  situated  on  the  opposite  side,  is  wider  ments  uniting 
and  thicker  than  it.  It  commences  on  the  internal  tube- 
rosity of  the  radius,  and  terminates  on  the  upper  extremity 
of  the  middle  and  internal  metacarpal  bones,  after  being 
attached,  by  two  distinct  fasciculi,  to  the  third  carpal  bone 
of  the  upper  row,  and  the  two  last  of  the  metacarpal  row 
In  contact  by  its  external  face  with  the  tendon  of  the 
oblique  extensor  muscle  of  the  metacarpus,  this  ligament 
responds,  by  its  deep  face,  to  the  synovial  membranes  of 
the  carpus  and  to  the  bones  to  which  it  is  attached.  By 
its  anterior  border  it  is  united  to  the  capsular  ligament , 
the  opposite  border  is  intimately  confounded  with  the  pos- 
terior ligament,  from  which  it  is  impossible  to  distinguish 
it. 

c.  The  anterior,  or  capsular  ligament,  is  a  membranous 
band  covering  the  anterior  face  of  the  carpal  articulations. 
Its  superior  border  is  attached  to  the  radius  ,  the  inferior 
is  inserted  into  the  superior  extremity  of  the  principal 
metacarpal  bone.  The  two  right  and  left  borders  are 
united  with  the  lateral  ligaments.  Its  external  face  is  in 
contact  with  the  tendons  of  the  anterior  extensor  muscles 
of  the  metacarpus  and  phalanges.  The  internal  fiice  is 
lined  at  certain  points  by  synovial  membrane,  and  adheres 
in  others  to  the  carpal  bones  and  the  anterior  ligaments 
binding  these   to  one  another.     This  ligament  is  composed  of  ti-ansverse 


LATERAL  VIEW  OF 
THE  CARPAL  AR- 
TICULATIONS. 


the  two  rows  ot 
carpal  bones ;  2, 
2,  Anterior  liga- 
ments proper  to 
the  carpo-meta- 
carpal  articula- 
tion; 3,  Common 
external  liga- 
ment ;  4,  One  ot 
the  ligaments 
proper  to  the 
articulation  of 
the  two  rows 
(metacarpo  -  su- 
pracarpal) ;  5, 
One  of  the  liga- 
ments proper  to 
the  radio-carpal 
articulation  (ra- 
dio -  supracar- 
pal). — A,  Groove 
on  the  external 
surface  of  the  su- 
pra carpi  1  bone 
for  the  passage 
of  the  external 
flexor  of  the  me- 
tacarpus. 


152  THE  ARTICULATIONS. 

fibres  more  or  less  oblique,  and  arranged  crosswise;  by  its  amplitude  it 
can  adapt  itself  to  tbe  movements  of  flexion  of  the  knee. 

d.  The  posterior  ligament,  one  of  the  strongest  in  the  animal  economy, 
covers  the  posterior  face  of  the  carpus,  filling  up  the  asperities  which 
roughen  it.  It  is  inserted :  above,  on  the  transverse  crest  surmounting  the 
articular  surface  of  the  radius ;  by  its  middle  portion  into  all  the  carpal  bones  ; 
below,  into  the  head  of  the  principal  metacarpal  bone.  Confounded  inwardly 
with  the  internal  lateral  ligament,  united  outwardly  to  the  band  which  attaches 
the  supercarpal  to  the  external  metacarpal  and  the  second  carpal  bone  of  the 
upper  row,  this  ligament  is  continued,  by  its  inferior  extremity,  with  the 
carpal  stay  (or  check  ligament)  which  sustains  the  perforans  tendon.  Its 
posterior  face  is  perfectly  smooth,  and  is  covered  by  the  synovial  membrane 
of  the  carpal  sheath. 

Movements  of  the  Carpal  Articulations. — The  carpus  is  the  seat  of 
two  very  extensive  and  opposite  movements — flexion  and  extension  ;  to  which 
are  added  three  very  limited  accessory  movements — adduction,  abduction,  and 
cii'cumduction. 

All  the  carpal  articulations  do  not  take  an  equal  part  in  the  execu- 
tion of  these  movements ,  for  it  is  easy  to  discover  that  they  are  chiefly 
jierformed  in  the  radio-carpal  diarthrosis,  and  in  the  imperfect  hinge 
articulation  uniting  the  two  rows  of  carpal  bones.  Each  of  these  articula- 
tions participates  in  the  movements  of  the  carpus  in  nearly  the  same  pro- 
portions, and  both  act  in  an  identical  manner.  Their  mechanism  is  most 
simple. 

In  flexion,  the  first  tier  of  bones  rolls  backwards  on  the  radius,  the  inferior 
row  moves  in  the  same  sense  on  the  upper,  the  metacarpus  is  carried  back- 
wards and  uj)wards,  the  common  posterior  ligament  is  relaxed,  the  capsular 
ligament  becomes  tense,  and  the  articular  surfaces,  particularly  those  of  the 
second  joint,  separate  from  each  other  in  front.  In  extension,  the  metacarpus 
is  carried  downwards  and  forwards  by  an  inverse  mechanism.  This  move- 
ment stops  when  the  ray  of  the  fore-arm  and  that  of  the  metacarpus  are  in 
the  same  vertical  line.  In  flexion,  these  rays  never  directly  approach  each 
other  ;  the  inferior  extremity  of  the  metacarpus  lacing  always  carried  outwards. 
It  may  also  be  remarked,  that  the  slight  movements  of  abduction,  adduction, 
and  circumduction  of  the  carpus  are  only  possible  at  the  moment  when  the 
foot  is  flexed  on  the  fore-arm. 

With  regard  to  the  planiform  diarthrosis  articulating  the  carpal  bones  of 
the  same  row,  they  only  allow  a  simple  gliding  between  the  surfaces  in 
contact ;  and  with  the  carpo-metacarpal  arthrodia  it  is  absolutely  the  same. 
The  restricted  mobility  of  these  various  articulations  has  but  a  very  secondary 
influence  on  the  general  movements  of  the  carpus ;  but  it  nevertheless  favoiu'S 
them  by  permitting  the  carpal  bones  to  change  their  reciprocal  relaticms, 
and  adapt  themselves,  during  the  play  of  the  radio-carpal  and  intercarpal 
lunges,  to  a  more  exact  coaptation  of  the  articular  planes  which  they  form. 

In  the  other  animals,  the  carpal  articulations  have  the  s-ame  essential  characteristics 
we  have  noticed  in  Solipeds.  I'he  four  principal  peripheral  bands  differ  but  Httle  in 
them ;  though  in  the  Bog  and  Cat  they  are  lax  enough  to  allow  somewhat  extensive 
lateral  movements. 

5.  Intermetacarpal  Articulations.  I 

Each  lateral  metacarpal  bone  articulates  with  the  middle  one  by  means 
of  diarthrodial  and  synarthrodial  surfaces,  for  the  description  of  which  refer 
to  page  82.     An  interosseous  ligament,  composed  of  very  short  and  strong 


ASTICULATIONS  OF  THE  ANTERIOR  LIMBS.  153 

fasciculi,  is  interposed  between  the  synarthrodia!  surfaces,  and  binds  them 
firmly  together.  Its  ossification  is  not  rare.  The  diarthrodial  facets  are 
maintained  in  contact  by  the  preceding  ligament,  and  by  the  carpal  ligaments 
inserted  into  the  head  of  the  lateral  metacarpal  bones.  The  intermetacarpal 
ai'ticulations  only  allow  a  very  obscure,  vertical,  gliding  movement. 

In  the  Ox,  there  is  only  one  intermetacarpal  articulation,  which  is  much  simpler 
than  tliose  in  the  Horse. 

In  the  Pig,  the  four  metacarpal  bones  correspond,  at  their  upper  extremity,  by  means 
of  small  diarthrodial  facets  on  their  sides.  Fibrous  fasciculi,  derived  from  tlie  great 
anterior  and  posterior  ligaments  of  the  carpus,  protect  tliese  intermetacarpal  articula- 
tions before  and  behind.  Other  fibres,  situated  between  the  adjacent  faces  of  the 
metacarpal  bones,  are  real  interosseous  ligaments. 

In  the  DcH]  and  Cat,  the  four  great  metacarpal  bones  articulate  \n.th  each  other  in 
almost  the  same  manner  as  iu  the  Pig,  but  their  mobility  is  greater. 

6,  Metacarpo-phalangeal  Articulation. 

{Preparation. — Turndown  the  anterior  and  lateral  extensor  tendons  of  the  phalanges, 
after  carefully  cutting  tlirough  their  attachment  with  the  capsular  ligament.  Lay  open 
the  metacarpo-phalangeal  sheath  from  above  to  below,  and  txura  down  the  flexor 
tendons.  J 

This  is  a  perfect  hinge-joint,  formed  by  the  inferior  extremity  of  the 
median  metacarpal  bone  on  the  one  part,  and  the  superior  extremity  of  the 
upper  ]>halanx  and  sesamoids  on  the  other. 

Articular  surfaces. — For  the  metacarpal  bone,  there  are  two  lateral 
condyles  and  a  median  antero-posterior  eminence ;  for  the  first  phalanx,  two 
glenoid  cavities  and  an  intermediate  groove  prolonged  posteriorly  on  the 
anterior  face  of  the  two  sesamoids.  Divided  in  this  manner  into  three  por- 
tions, the  digital  surface  is  well  constituted  for  solidity,  because  the  pressure 
transmitted  to  this  region  is  diminished  and  diffused  by  the  natural  elasticity 
of  the  bands  which  tmite  these  three  pieces  to  each  other. 

Mode  of  union.    The  means  of  union  may  be  divided  into  two  categories: 

1,  Those  which  join   together  the  several  bones  of  the  inferior  surface; 

2,  Those  which  maintain  in  contact  the  two  opposed  articular  surfaces. 

A.  The  first  have  received  the  generic  name  of  sesamoid  li(jaments,  and 
are  six  in  number;  an  intersesamoid  ligament,  which  keeps  together  the  two 
complementary  bones  of  the  digital  surface ;  three  inferior  and  tico  lateral 
sesamoid  ligaments,  which  unite  these  bones  to  the  fu-st  phalanx. 

a.  The  intersesamoid  ligament  is  composed  of  fibro-cartilaginous  substance 
which  appears  to  be  the  matrix  in  which  the  two  sesamoids  were  developed, 
as  it  is  spread  around  these  bones,  after  being  solidly  fixed  on  their  internal 
face.  Behind,  this  ligament,  in  common  with  the  posterior  face  of  the  sesa- 
moids, forms  the  channel  (Fig.  89,  5)  in  which  the  flexor  tendons  glide. 
In  front,  it  occupies  the  bottom  of  the  intersesamoid  articular  groove. 

6.  The  inferior  sesamoid  ligaments,  situated  at  the  iwsterior  face  of  the 
first  phalanx,  are  distinguished  as  superficial,  middle,  and  deep. 

The  superficial  ligament  (Fig.  89,  8),  the  longest  of  the  three,  is  a  narrow 
band  flattened  before  and  behind.  It  arises  from  the  middle  of  the  fibro- 
cartilaginous mass  which  completes,  posteriorly,  the  superior  articular 
surface  of  the  second  phalanx,  and  slightly  \v4dening,  ascends  to  the  base  of 
the  sesamoids,  into  which  it  is  inserted  by  becoming  confounded  with  the 
intersesamoid  ligament.  Its  posterior  face,  lined  by  the  synovial  membrane  of 
the  so-called  sesamoid  sheath,  is  covered  by  the  flexor  tendons ;  it  partly 
covers  the  middle  ligament. 

The  middle  ligament,  triangular   and  radiating,  is  composed  of  three 


154  THE  ABHCVLAT10N8. 

particular  fasciculi :  two  lateral  (seen  on  each  side  of  the  superficial  liga- 
ment in  Fig.  89,  8),  and  a  median  which  has  been  generally  confounded 
with  the  superficial  ligament,  although  it  is  clearly  distinguished  from  it 
by  its  inferior  insertion.  Fixed  in  common  to  the  posterior  imprints  of  the 
first  phalanx,  these  three  fasciculi  diverge  in  ascending  to  the  base  of  the 
sesamoids,  where  they  have  their  upper  insertion. 

The  deep  lujament  is  constituted  by  two  small  bands  concealed  beneath 
the  middle  ligament.  Thin,  short,  flattened  before  and  behind,  and  inter- 
crossed, these  bands  are  fixed  to  the  base  of  tho  sesamoids  in  one  direction, 
and  in  the  other  to  the  superior  extremity  of  the  first  phalanx,  near  the 
margin  of  its  articular  surface.  This  ligament  is  lined  on  its  anterior  face 
by  the  synovial  membrane  of  the  articulation.' 

c.  The  lateral  sesamoid  ligaments  are  two  thin  layers  extending  from  the 
external  face  of  each  sesamoid  to  the  tubercle  of  insertion  on  the  side  of 
the  superior  extremity  of  the  first  phalanx.  They  are  covered  by  the  digital 
vessels  and  nerves,  by  the  fibrous  stay  detached  from  the  suspensory  liga- 
ment to  the  anterior  extensor  tendon  of  the  phalanges,  and  by  the  superficial 
fasciculus  of  the  lateral  metacarpo-phalangeal  ligament ;  they  are  covered  by 
synovial  membrane  on  their  internal  face. 

B.  The  ligaments  destined  to  unite  the  two  articular  surfiices  of  the  meta- 
carpo-phalangeal  joint  are  four :  two  lateral,  one  anterior,  and  one  posterior. 

a.  Each  lateral  ligament  comprises  two  fasciculi,  a  superficial  and  a 
deep,  firmly  united  by  their  adjacent  faces.  The  superficial  fasciculus 
commences  on  the  button  of  the  lateral  metacarpal  bone,  attaches  itself  to 
the  median  metacarpal,  and  descends  vertically  to  terminate  at  the  superior 
extremity  of  the  first  phalaux.  It  covers  the  phalangeal  insertion  of  the 
lateral  sesamoid  ligament  and  the  deep  fasciculus.  The  latter,  attached 
suiDcriorly  in  the  lateral  excavation  of  the  inferior  extremity  of  the  jirincipal 
metacarpal,  radiates  as  it  reaches  the  sesamoid  and  the  superior  extremity 
of  the  first  phalanx,  where  it  is  fixed  by  mixing  its  fibres  with  those  of  the 
lateral  sesamoid  ligament.  The  inner  face  of  this  fasciculus  is  lined  by  the 
articular  synovial  membrane. 

h.  The  anterior  ligament  belongs  to  the  class  of  capsular  ligaments.  It 
is  a  very  resisting  membraniform  expansion  which  envelops  the  anterior  face 
of  the  articulation.  Attached  by  its  upper  border  to  the  anterior  margin  of 
the  metacarpal  surface,  and  by  its  inferior  border  to  the  first  phalanx,  this 
expansion  is  confounded  at  its  sides  with  the  lateral  ligaments.  It  is  covered 
by  the  extensor  tendons  of  tlie  phalanges,  which  glide  on  its  sui-face  by  means 
of  small  serous  sacs.  Its  internal  face  adheres  throughout  its  whole  extent 
to  the  synovial  capsule. 

c.  The  posterior  ligament,'^  very  appropiately  nan>ed  the  suspensory  ligament 
of  the  fetlock  (Figs.  88  ,  89,  4),  is  a  long  and  powerful  bi-ace,  composed  of  white 
fibrous  tissue,  and  often  containing  fasciculi  of  fleshy  fibres  in  its  texture. 
Lodged  behind  the  median  metacarpal,  and  between  the  two  lateral  meta- 
carpal bones,  this  brace  is  quite  thin  at  its  origin,  but  it  soon  becomes 
enlarged,  and  preserves  its  great  thickness  to  the  extent  of  its  upper  fourth. 
Examined  in  section,  it  appears  to  be  formed  of  two  superposed  portions  which 
are  closely  adherent  to  each  other.  The  superficial  portion,  the  thinnest, 
commences  by  three  small  branches,  which  are  fixed  to  the  first  and  second 

*  The  two  bands  described  by  Kigot  as  forming  part  of  this  ligament,  belong  to  the 
lateral  fasciculi  of  the  middle  ligament. 

*  It  corresponds  to  the  two  muscles  which,  iu  Man,  lie  alongside  the  interosseous 
metacarpal  muscles.     See  the  Mvscles  of  the  foot. 


ABTICULATIOXS  OF  THE  ANTERIOR  LIMBS. 


155 


Fisj.  88. 


bones  of  the  lower  carpal  row ;  the  deep  portion,  much  thicker,  is  attached 
to  the  posterior  face  of  the  principal  metacarpal  foi-  about  8-lOths  of  an  inch. 
Jt  has  been  wrongly  asserted  that  the  suspensory  ligament  of  the  fetlock  is 
continuous  with  the  common  posterior  ligament  of  the  carpus ;  it  is,  on  the 
contrary,  quite  distinct  from  it.  The  carpal  stay  or  deep  palmar  aponeu- 
rosis of  Man,  is  alone  in  direct  continuity  with  the  common  posterior  liga- 
ment of  the  carpus.  The  suspensory  ligament  of 
the  fetlock  is  bifid  at  its  inferior  extremity ;  its 
two  branches,  after  being  fixed  into  the  summits 
of  the  sesamoid  bones,  give  origin  to  two  fibrous 
bands  which  pass  downwards  and  forwards  to 
become  united  on  each  side  to  the  anterior  ex- 
tensor tendon  of  the  phalanges.  It  is  in  relation, 
by  its  posterior  face,  with  the  perforans  tendon  and 
its  carpal  stay  ;  by  its  anterior  face,  with  the 
median  metacarpal  bone,  and  arteries  and  veins ; 
by  its  borders,  with  two  small  interosseous  muscles, 
the  lateral  metacarpal  bones,  and  the  digital 
vessels  and  nerves. 

Synovial  membrane. — This  membrane  is  pro- 
longed as  a  cul-de-sac  between  the  terminal 
branches  of  the  preceding  ligament.  It  is  the 
distention  of  this  sac  which  causes  the  articular 
swellings  vulgarly  designated  "windgalls." 

Movements. — The  metacarpo-phalangeal  articu- 
lation permits  the  extension  and  flexion  of  the  digit, 
and  some  slight  lateral  motion  wlien  the  movable 
osseous  ray  is  carried  to  the  limits  of  flexion. 


SECTION  OF  THK  INFERIOR 
ROW  OF  CARPAL  BONES, 
THE  METACARPAL,  AND  THE 
SUSPENSORY  LIGAMENT  OF 
THE   FETLOCK. 

1,  Os  magnum ;  2,  Common 
posterior  ligament  of  the 
carpus;  3,  Stay,  or  band 
for  the  perforans  tendon ; 
4,  Suspensory  ligament  of 
the  fetlock ;  5,  Its  super- 
ficial layer;  6,  Its  deep 
fasciculus ,  7,  Principal 
metacarpal  bone. 


In  the  Ox,  Slieep,  and  Goat,  this  articulation  consti. 
tutes  a  double  hinge  which  resembles  the  simple  gin- 
glymus  of  monodactyles. 

They  have  tliree  intersesamoid  ligaments  two  lateral 
to  unite  the  large  sesamoids  of  each  digit,  and  a  median 
■which  unites  the  internal  sesamoids.  The  inferior  sesa- 
moidean  ligamentous  apparatus  is  far  from  showing  the  same 
degree  of  development  as  in  the  Horse ;  it  is  reduced  for 
each  diiiit  to  four  small  bands,  which  remind  one  very 
much  of  the  deep  ligament  of  the  latter  animal,  as  it  has 
been  described  by  Kigot :  two  lateral  bands  pass  directly 
from  the  sesamoids  lo  the  upper  extremity  of  the  first 
phalanx ;  the  other  two,  situnted  between  the  first,  inter- 
cross and  are  confounded  with  the  latter  by  their  ex- 
tremities.— A  lateral  sesamoid  ligament  unites  the  first  phalanx  to  the  external  sesamoid. 

For  each  digit  there  are  two  lateral  metacarpo-phalangeal  ligaments  an  external, 
analogous  to  that  of  the  Hor^e,  but  less  complicated,  is  attaciied  by  its  inferior  extremity 
to  the  first  plialanx  only ;  the  other,  internal,  fixed  superiorly  in  the  bottom  of  the  inter- 
articular  notch  of  the  metacarpal  bone,  is  inserted  into  the  inner  face  of  the  first 
phalanx  in  mixing  its  fibres  with  those  of  the  superior  interdigital  ligament.  This 
latter  is  situated  between  the  two  first  phalanges,  and  is  composed  of  short,  intercrossed 
fibres,  attached  to  the  imprints  which  in  part  cover  the  internal  face  of  the  two  first 
phalangeal  bones.  In  the  Sheep  there  are  only  traces  of  this  interdigital  ligament,  and 
each  internal  metacarpo-phalangeal  ligament  gives  rise,  near  its  phalangeal  insertion,  to 
a  fibrous  branch  which  is  directed  backwards  from  the  interdigital  space,  and  ia 
terminated  in  the  bone  of  the  ergot  (or  posterior  rudimentary  digit),  which  it  sustains. 
The  anterior  or  capsular  ligament,  single  as  in  Solipeds,  unites  the  two  external  lateral 
ligaments.  The  suspensory  ligament,  single  superiorly,  is  divided  inferiorly  into  eight 
branches,  two  of  which  are  joined  to  the  perforatus  tendon  to  form  with  it  the  double 
ling  through  which  the  two  branches  of  the  perforans  pass.     Four  other  branches,  in 


156 


TEE  ABTICULATIONS. 


Fig. 


pairs,  extend  to  the  summits  of  the  sesamoids.  That  which  is  sent  to  each  external 
sesamoid  gives  off,  on  the  side  of  the  first  phalanx,  a  reinforcing  band  to  the  proper 
extensor  of  the  digit.  The  two  last,  profound  and  median,  dcsooiid 
into  the  interarticular  notch  of  the  metacarpal  bone,  after  becoming 
a  single  fasciculus ,  afterwards,  they  pass  between  the  two  internal 
metacarpo-phalangeal  ligaments,  and  separate  from  each  other  in 
passing  downwards  and  forwards  on  the  inner  side  of  the  first 
phalanx,  to  join  the  proper  extensor  tendon  of  each  digit. 

In  the  Pig,  Dog,  and  Cat,  for  each  metacarpo-phalangeal  there 
is :  a  proper  synovial  membrane ;  an  intersesamoid  ligament ;  au 
inferior  sesamoid  ligament  composed  of  two  cross-bands ;  two  small 
lateral  sesamoid  ligaments;  two  lateral  metacarpo-phalangeal  liga- 
ments, attached  inferiorly  to  the  first  phalanx  and  the  sesamoids ; 
an  anterior  capsular  ligament,  in  the  centre  of  which  is  found  a 
small  bony  nucleus,  a  kind  of  anterior  sesamoid,  over  which  glides 
one  of  the  branches  of  the  common  extensor  of  the  digits.  The 
suspensory  ligament  is  replaced  by  real  palmar  interosseous  muscles 
(see  the  iluscles  of  the  fore-foot).  Some  fibres  situated  between  the 
first  phalanges  of  the  great  digits  in  the  Pig,  remind  one  of  the 
superior  interdigital  ligament  of  the  Ox. 

In  Man,  the  cavity  in  the  upper  extremity  of  the  first  phalanx 
is  completed  by  a  glenoid  ligament.  The  glenoid  ligaments  of  tlie 
four  first  digits  are  united  to  each  other  by  a  transverse  ligament 
of  the  metacarpus.  The  articulaticms  are  consolidated  by  two 
lateral  ligaments.  The  metacarpo-phalangeal  articulations  allow 
flexion  and  extension  movements,  as  well  as  those  of  abduction 
and  adduction  ;  but  the  latter  are  limited  by  the  lateral  ligaments. 


/'\' 


J 


7.  Articulation  of  the  First  loith  the  Second  Phalanx,  or 
First  Ivterphalangenl  Articulation. 

{Preparation. — Remove  the  extensor  tendon;  throw  open  the 
metacarjJO-phalangeal  sheath,  and  turn  down  the  flexor  tendons.) 

This  is  an  imperfect  hiuge-joint. 

Articular  surfaces. — On  the  inferior  extremity  of  the 
fii'st  phahxnx,  there  are  two  lateral  condyles  separated  by  a 
groove.  On  the  superior  surface  of  the  second  phalanx,  tliere 
are  two  glenoid  cavities  and  an  an tero- posterior  ridge. 

The  latter  surface  is  completed  behind  by  a  glenoidal 
Ji.hr o-cartilage,  very  dense  and  thick,  which  also  acts  as 
a  ligament.  It  is  attached,  in  one  direction,  to  the 
second  phalanx,  between  the  superior  articular  surface 
and  the  kind  of  fixed  sesamoid  which  margins  it  behind  ; 
in  the  other,  it  is  inserted  into  the  first  phalanx  by  means 
of  six  fibrous  bands :  two  superior,  which  embrace  the 
GEAL  AETicuLA-  inferior,  middle,  and  superficial  sesamoid  ligaments ;  two 
TioNs  ;  RIGHT  ^j-^j^jjq  ^j^^j  ^wo  inferior,  which  extend  to  the  sides  of  the 
1  3  Outer  and  inner  inferior  extremity  of  the  first  phalanx.  This  fibro-car- 
'  rudimentary  me-  tilage  is  moulded,  in  front,  to  the  articular  surface  of  the 
tatarsal  bones ;  2,  latter  bone,  aud  forms,  by  its  posterior  face,  a  gliding 
Perforans    tendon 

and  its  check  ligament ;  4,  Suspensory  ligament ;  5,  Gliding  surface,  or  sheath  for  the 
flexor  tendons,  formed  by  the  posterior  face  of  the  sesamoid  bones,  and  intersesamoid, 
transverse,  and  annular  ligaments ;  6,  Section  of  lateral  sesamoid  ligament ;  7,  Lateral 
fasciculus  of  the  middle  inferior  sesamoid  ligament ;  8,  Inferior  superficial  sesamoid 
ligament-  9,  Lateral  ligament  of  the  first  interphalangeal  articulation;  10,  Section 
of  the  terminal  branch  of  the  perforatus  tendon;  11,  Section  of  the  lateral  cartilage 
of  the  foot-  12,  Postero-inferior  surface  of  navicular  bone;  13,  Section  of  latei-al  car- 
tilage, plantar  cushion,  and  wing  of  pedal  bone ;  14,  Perforatus  tendon ;  15,  Perforans 
tendon. 


POSTKRIOR  VIEW  OF 
THE  METACARPO- 
PHALANGEAL AND 
INTER  -  PHALAN- 


ARTICULATIONS  OF  THE  ANTERIOR  LIMBS.  157 

surface  for  the  perforans  tendon  (Fig.  89,  5).  It  is  confounded,  laterally, 
•with  the  two  branches  of  the  perfuratus,  aud  receives  in  the  middle  of  its 
superior  border  the  insertion  of  the  inferior  superlicial  sesamoid  ligament. 

Mode  of  union. — Tico  lateral  ligaments,  to  which  are  added,  behind,  the 
fibro-cartilage  just  described,  aud  in  front  the  tendon  of  the  anterior 
extensor  of  the  phalanges  These  ligaments  are  large  and  thick,  and  passing 
obliquely  downwards  and  backwards,  are  inserted,  superiorly,  into  the 
lateral  tubercles  on  the  inferior  extremity  of  the  first  phalanx.  They  are 
attached,  beneath,  to  the  sides  of  the  second  phalanx.  Their  most  inferior 
fibres  are  even  prolonged  below  that  point  to  reach  the  extremities  of  the 
navicular  bone,  and  constitute  the  posterior  lateral  ligaments  of  the  pedal 
articulation. 

Synovial  rnemhrane. — This  covers  the  tendon  of  the  anterior  extensor  of  the 
phalanges,  the  lateral  ligaments,  and  the  glenoid  fibro-cartilage.  Behind,  it 
forms  a  cul-de-sac  which  extends  between  the  latter  and  the  posterior  face  of 
the  fii'st  phalanx. 

Movements.  This  imperfect  hinge  is  the  seat  of  two  principal  movements: 
extension  and  flexion.  It  also  allows  the  second  jihalanx  to  pivot  on  the  first, 
aud  permits  some  lateral  movements. 

la  the  Ox,  Sheep,  and  Goat,  the  glenoid  f3bro-cartilage  is  confounded  with  the  per- 
foratus  tendon,  and  is  only  attached  to  the  first  phalanx  by  two  lateral  bands.  The 
internal  lateral  Ugament  comprises  two  fasciculi :  one,  very  short,  which  terminates  in 
the  second  phalanx ;  and  another,  very  long,  descending  to  the  internal  face  of  the  third 
phalanx.  The  external  is  very  thin,  and  is  also  prolonged  to  the  terminal  phalanx;  so 
that  the  two  last  iuterphalungeal  articulations  of  each  digit  are  fixed  by  two  common 
lateral  ligaments  which  correspond  exactly,  by  their  position  and  inferior  attachments, 
to  the  anterior  lateral  ligaments  of  the  pedal  joint  of  Solipeds. 

In  the  Dog  and  Cat,  the  glenoid  cartilage,  also  confounded  by  its  posterior  face 
with  the  perforatus  tendon,  only  adlieres  to  the  first  phalanx  by  some  cellular  bands. 
The  two  lateral  ligaments  pass  from  the  inferior  extremity  of  the  first  phalanx  to  the 
superior  extremity  of  the  second. 

In  the  Pig,  there  is  somewhat  the  same  arrangement  as  in  Carnivora.  The  external 
lateral  ligament  is,  nevertheless,  more  like  that  of  the  Horse,  in  its  most  anterior  fasciculi 
being  prolonged  to  the  external  extremity  of  the  navicular  bone. 

8.  Articulation  of  the  Second  Phalanx  icith  the  Third,  Second  Interphalangeal 
Articulation,  or  Articulation  of  the  Foot. 

To  form  this  imperfect  hinge-joint,  the  second  phalanx  is  opposed  to  the 
third,  and  to  the  navicular  bone. 

Articular  surfaces.  — On  the  inferior  face  of  the  second  phalanx  there  are 
two  lateral  condyles  and  a  median  groove.  On  the  superior  face  of  the 
third  phalanx  and  the  navicular  bone,  are  two  glenoid  cavities  separated  by 
an  antero-posterior  ridge.  The  two  bones  which  form  this  last  sm-face  arti- 
culate with  each  other  by  an  arthrodia ;  the  navicular  bone  presents  for  this 
purpose  an  elongated  facet  on  its  anterior  border ;  the  os  pedis  also  ofiers 
an  analogous  facet  on  the  posterior  contour  of  the  principal  articular  surface. 

Mode  of  union. — Five  ligaments :  a  single  interosseous  one  which  joins 
the  navicular  to  the  pedal  bone;  and  four  lateral  pairs,  distinguished  as 
anterior  and  posterior. 

a.  Interosseous  ligament. — This  is  formed  of  very  short  fibres  which  are 
inserted,  behind,  into  the  anterior  groove  of  the  navicular  bone;  and  in 
front,  into  the  posterior  border  and  inferior  face  of  the  third  phalanx.  This 
ligament  is  lined,  on  its  superior  surface,  by  the  synovial  membrane,  and  on 
its  iuferior  face  is  covered  by  the  navicular  sheath, 

h.  Anterior   lateral   ligaments. — These  are  two  thick,  short,   and   wide 


158  THE  ARTICULATIONS. 

fasciculi,  attached  by  their  superior  extremities  to  the  lateral  imprints  of  the 
second  phalanx,  and  by  their  inferior  extremities  into  the  two  cavities  at  the 
base  of  the  pyramidal  eminence  of  the  os  pedis.  Each  ligament  is  partly 
covered  by  the  complementary  fibro-cartilage  of  that  bone,  and  appears  to 
form  a  portion  of  it.  Its  anterior  border  is  continuous  with  the  common 
extensor  tendon  of  the  phalanges ;  its  internal  face  is  covered  by  the 
synovial  membrane,  which  adheres  closely  to  it. 

c.  Posterior  lateral  ligaments. — These  have  been  already  noticed. 
Each  is  composed  of  the  lowermost  fibres  of  the  lateral  ligament  of  the  first 
interjihalangeal  articulation ;  these  fibres,  after  being  attached  to  the 
second  phalanx,  unite  into  a  sensibly  elastic  fibrous  cord,  which  is  chiefly 
fixed  into  the  extremity  and  superior  border  of  the  navicular  bone,  where  the 
ligaments  join  each  other,  and  in  this  way  form  a  kind  of  complementary 
cushion  which  increases  the  navicular  articular  surface.  It  also  sends  off 
a  short  fasciculus  to  the  retrossal  process,  and  a  small  band  to  the  internal 
face  of  the  lateral  fibro-cartilage.  Partly  concealed  by  the  latter  and  the 
plantar  cushion,  this  ligament  is  covered  inwardly  by  the  articular 
synovial  membrane. 

(For  full  details  as  to  the  manner  in  which  the  navicular  is  attached  to 
the  pedal  bone,  the  student  is  referred  to  the  series  of  papers  on  the  Horse's 
Foot,  published  by  me  in  the  '  Veterinarian '  for  1870.  It  is  only  necessary 
to  refer  here  to  the  intimate  connection  there  exists  between  the  lateral  and 
interosseous  ligaments,  and  the  stratiform  fibro-cartilage  covering  the  pos- 
terior face  of  this  sesamoid :  a  connection,  or  rather  unification,  which  has 
been  strangely  overlooked  by  hippotomists  and  hippo-pathologists,  but 
which  has  undoubtedly  a  most  important  bearing  on  the  genesis  of  that 
very  prevalent  and  formidable  malady  of  the  anterior  foot  of  the  Horse 
— navicularthritis.) 

Synovial  membrane. — This  descends  below  the  facets  which  unite  the 
navicular  to  the  pedal  bone.  It  offers,  posteriorly,  a  vast  cul-de-mc  which 
reaches  the  posterior  face  of  the  second  phalanx,  and  lies  against  the  two 
navicular  sheaths.  It  also  forms  another  much  smaller,  by  being  prolonged 
between  the  two  lateral  ligaments  of  the  same  side.  This  is  very  often  dis- 
tended, and  it  is  liable  to  be  opened  in  the  operation  for  diseased  cartilages. 

Movements. — The  same  as  those  of  the  fii'st  interphalangeal  articulation. 

In  the  Sheep  are  found  :  1,  An  interosseniis  ligament  to  unite  the  navicular  bone  to 
the  third  phalanx;  2,  Two  anterior  lateral  ligaments  commencing,  as  already  stated,  at 
the  first  phalanx  ;  3,  Two  lateral  posterior  ligaments,  passing  to  the  posterior  face  of  the 
second  phalanx  and  the  navicular  bone  (the  internal  is  yellow  and  elastic);  4,  A  single, 
.anterior,  elastic  ligament,  attached  above  to  the  superior  extremity  of  the  second 
phalanx,  and  fixed  below  into  the  third,  between  the  insertion  of  tlie  common  extensor 
of  the  digits  and  tliat  of  the  internal  anterior  lateral  ligament;  an  interior  interdigital 
ligament,  situated  between  the  uugueal  phalanges,  whose  scjjaration  from  each  otiier  it 
limits.  This  ligament  is  comfiosed  of  parallel  fibres,  wliinh  extend  transversely  from  tiie 
one  navicular  bone  to  the  otlier,  and  is  covered  on  its  inferior  face  by  the  skin  of  the 
interdigital  space.     Its  upper  face  is  in  contact  with  an  adipose  cushion. 

In  the  Ox,  the  external  anterior  lateral  ligament,  wide  and  expanding,  is  almost 
entirely  covered  by  the  long  branch  of  the  proper  extensor  of  the  digit,  to  which  it  is 
intimately  adherent.  The  interdigital  ligament  has  a  much  more  complicated  character 
than  that  of  the  Sheep.  It  is  formed  of  fibres  intercrossed  on  the  median  line,  and 
divided  at  its  extremities  into  two  fasciculi:  a  superior  passes  over  the  perforans  ti-ndon, 
to  which  it  serves  as  a  restraining  band,  and  is  fixed  to  the  outside  of  the  inferior 
extremity  of  the  first  phalanx,  after  contracting  very  close  adhesions  with  a  strong  fibrous 
■web  which  descends  from  tlie  posterior  metacarpal  region,  and  which  will  be  more  fully 
noticed  when  descriliing  the  muscles;  an  inferior,  shorter  than  the  preceding,  attached 
to  the  internal  extremity  of  the  navicular  bone  and  the  internal  face  of  the  third  phalanx, 


ARTICULATIONS  OF  THE  POSTERIOR  LIMBS.  159 

becoming  confounded  with  the  perforans  tendon,  the  plantar  cushion,  and  the  kera- 
togenous  membrane. 

In  tlie  Fig,  for  the  maintenance  of  the  second  interphalangeal  articulation,  there 
are  :  1,  Two  lateral  ligaments,  carried  from  the  lateral  fiices  of  the  second  phalanx  to 
the  external  and  internal  faces  of  the  third;  2,  A  third  ligament,  exactly  resembling  one 
of  tlie  posterior  lateral  ligaments  of  the  pedal  articulation  of  the  Horse;  this  ligament 
descends  from  the  inferior  extremity  of  the  first  phalanx  to  the  internal  extremity  of  the 
navicular  bone.  Its  analogue  of  the  inner  side  appears  to  be  altogether  absent;  but 
in  tlie  large  digits  there  is  an  anterior  yellow  elastic  ligament  like  that  of  Ruminants. 

In  the"Do<7,  the  two  last  phalanges  are  united  by  two  lateral  ligaments,  very  simply 
arranged.  A  third  ligament,  formed  of  elastic  tissue,  divided  into  two  lateral  portions, 
ami  situated  in  front  of  the  articulation,  plays  the  part  of  a  spring,  which  mechanically 
produces  the  retraction  of  the  claw  when  the  flexor  muscles  cease  to  contract.  In  the 
Cat,  this  yellow  ligament  is  very  strong;  and  this  animal  also  exhibits  a  very  striking 
obliquity  of  the  articular  pulleys  by  which  the  two  phalanges  correspond :  an  arrange- 
ment which  permits  the  claw  to  be  lodged  between  two  digits  when  they  are  raised,  and 
thus  favour  its  retraction. 

The  second  interphalangeal  articulation  of  the  Dog  and  Cat  is  also  distinguished 
by  another  essential  arrangement.  The  articular  surface  of  the  third  phalanx  is  com- 
pleted by  a  glenoid  fibro-cartilage  analogous  to  that  of  the  first  articulation,  but  much 
thicker."  This  fibro-cartilage  (see  iVIiscLES  of  the  h.and)  is  fixed  into  thu  posterior 
projeetion  of  the  third  phalanx,  and  serves,  by  its  inferior  face,  as  a  pulley  for  the  per- 
forans tendon  and,  with,  the  projection  just  named,  plays  the  part  of  the  navicular  bona 
in  other  animals. 

The  interphalangeal  articulations  of  Man  are  formed  on  the  same  plan  as  the 
metacarpo-phalangeal  articulations.  They  are  eonsolidated  by  a  glenoid  and  lateral 
ligaments,  and  possess  only  the  two  movements  o(  flexion  and  extension. 

Article  V. — Articulations  of  the  Posterior  Limbs. 
1.  Articulations  of  the  Pelvis. 

{Preparation. — These  ligaments  are  all  exposed  to  view  by  carefully  removing  the  soft 
parts  connected  with  the  sacrum  and  coxae.) 

A.  Sacro-iliac  Articulation  (Fig.  90). — This  is  a  pair  articulation 
whicli  establishes  the  union  of  the  posterior  limb  with  the  spine,  and  is 
formed  by  the  sacrum  and  coxa.     It  belongs  to  the  arthrodial  class. 

Articular  surfaces. — On  the  sacrum,  the  irregular  diarthrodial  facet 
named  the  "  auricular,"  cut  on  the  sides  and  near  the  base  of  the  bone.  For 
the  coxa,  the  analogous  facet  on  the  internal  face  of  the  ilium. 

3Iode  of  union. — By  four  ligaments,  which,  after  the  example  of  Eigot, 
we  will  name  sacro-iliac,  superior  ilio-sacral,  inferior  ilio-sacral,  and  the 
sacro-ischiatic. 

a.  Sacro-iliac  ligament. — This  is  composed  of  thick  fibrous  fasciculi, 
which  envelope  the  whole  articulation  in  being  firmly  attached  by  their 
extremities  to  the  imijrints  around  the  diarthrodial  facets.  The  inferior 
moiety  of  this  ligament  is  covered  by  the  psoas-iliacus  (iliacus)  muscle.  Its 
posterior  half  ^  is  much  stronger,  is  hidden  by  the  ilium,  and  gives  attach- 
ment to  the  ilio-spinalis  (longissimus  dorsi)  muscle. 

b.  Superior  ilio-sacral  ligament. — A  thick  and  short  funicle  which, 
rising  from  the  internal  angle  of  the  ilium,  is  carried  backwards  to  be  fixed 
to  the  sacral  spine,  where  its  fibres  are  confounded  with  those  of  the  sujser- 
spinous  dorso-lumbar  ligament. 

c.  Inferior  ilio-sacral  ligament. — This  is  a  very  resisting,  triangular, 
membranous  band,  formed  of  parallel  fibres  passing  obliquely  downwards 
and  backwards.     It  is  attached,  by  its  anterior  margin,  to  the  upper  half  of 

'  It  represents  the  interosseous  sacro-iliac  ligament  of  Man.  The  inferior  half  corre- 
sponds to  the  anterior  sacro-iliac  ligament. 


160  THE  AETICCLATIONS. 

the  ischiatic  border  and  the  internal  angle  of  the  ilium,  in  becoming 
confounded  with  the  pi'eccding  ligament.  Its  inferior  margin  is  inserted 
into  tlie  rugged  lip  which  borders  the  sacrum  laterally.  Its  posterior  border 
is  united  to  the  aponeurosis  covering  the  coccygeal  muscles,  and  its  external 
face  is  in  contact  with  the  principal  gluteal  and  the  long  vastus  muscles ; 
while  the  internal  corresponds  to  the  lateral  sacro-coccygeal  muscle. 

d.  Sacro-sciatic  or  ischiatic  ligament  (Fig.  90,  2). — This  is  a  vast  mem- 
branous expansion  situated  on  the  side  of  the  pelvis,  between  the  sacrum 
and  the  coxa,  and  serves  more  as  a  means  for  inclosing  this  portion  of  the 
pelvic  cavity  than  to  assure  the  solidity  of  the  sacro-iliac  articulation.  Its 
form  is  irregularly  quadrilateral,  and  permits  its  circumference  to  be  divided 
into  four  borders :  a  superior,  attached  to  the  rugged  lateral  ridge  of  the 
sacrum ;  an  inferior,  fi.\;ed  to  the  supercotyloid  ridge,  as  well  as  the  ischial 
tuberosity,  and  forming  by  the  portion  comprised  between  these  two  in- 
sertions, with  the  small  ischiatic  notch,  the  opening  by  which  the  internal 
obturator  and  pyramidal  muscles  leave  the  pelvis ;  an  anterior,  imperfectly 
limited,  along  with  the  great  ischiatic  notch,  circumscribes  the  ojiening 
through  which  the  gluteal  vessels  and  nerves,  and  the  sciatic  nerves  pass ;  a 
posterior,  doubled  in  the  form  of  two  laminte  which  embrace  the  semi- 
membranosus muscle,  and  is  confounded  superiorly  with  the  aponeurosis 
enveloi)ing  the  coccygeal  muscles.  The  external  face  of  this  ligament  is 
traversed  by  the  sciatic  nerves,  and  is  covered  by  the  long  vastus  and  the 
semitendinosus  muscles,  which  derive  numerous  insertions  from  it.  Its 
internal  face  is  covered,  in  front,  by  the  peritoneum,  and  posteriorly  is  in 
contact  with  the  ischio-coccygeal  and  ischio-anal  muscles,  to  which  it  gives 
attachment. 

Synovial  membrane. — This  lines  tlie  sacro-iliac  ligament,  but  only 
furnishes  a  small  quantity  of  synovia. 

Movements. — The  two  sacro-iliac  articulations  being  the  centres  towards 
which  all  the  impulsive  efforts  communicated  to  the  trunk  by  the  posterior 
limbs  converge,  they  do  not  offer  much  mobility,  as  that  would  oppose 
the  integral  transmission  of  the  quantity  of  movement.  So  that  they 
permit  only  a  very  restricted  gliding  of  the  articular  surfaces ;  and  the 
union  of  the  sacrum  and  coxa  by  diarthrosis  appears  to  be  exclusively 
designed  to  prevent  the  fractures  to  which  these  bones  would  be  incessantly 
exposed  if  they  were  fixed  together  in  a  more  intimate  manner. 

B.  Articulation  of  the  Two  Cox^,  or  Ischio-pubic  Symphysis. — The 
two  coxae  are  united  to  each  other  throughout  the  whole  extent  of  the  inner 
border  of  the  pubis  and  the  ischial  bones.  In  youth,  this  is  a  veritable 
amphiarthrosis,  fixed  by  an  interosseous  cartilage  and  bundles  of  peripheral 
fibres. 

The  cartilage  is  solidly  fixed  to  the  small  rugged  eminences  which  cover 
the  adjacent  articular  surfaces,  and  becomes  ossified,  like  the  sutural 
cartilages,  as  the  animal  advances  in  age.  In  adult  Solipeds  the  coxre  are 
always  fused  with  each  other. 

The  peripheral  fibrous  fasciculi  extend  tranverscly  from  one  bone  to 
the  other,  above  and  below  the  symphysis ;  those  on  the  inferior  face  are 
incomparably  stronger  and  more  abundant  than  the  others. 

The  movements  of  this  articulation  are  most  restricted,  and  depend 
solely  upon  the  elasticity  of  the  interosseous  cartilage.  They  cease  after  its 
ossification. 

The  fusion  of  the  two  coxse  proceeds  very  slowly  in  the  female  of  the  Cat,  Dog,  Pig, 
Ox,  Sheep,  and  Goat  species. 


ARTICULATIONS  OF  THE  POSTERIOB  LIMBS. 


161 


2.   Coxo-femoral  Articulation. 

(Preparation. — Remove  the  muscles  surroiiiniiug  the  articulation.  To  view  the 
interior,  divide  the  capsular  ligament  by  a  circular  incision.) 

This  is  an  enarthrosis,  formed  by  the  reception  of  the  head  of  the 
femur  into  the  cotyloid  cavity  of  the  coxa. 

Articular  surfaces. — As  already  shown,  the  cotyloid  cavity  represents 
the  segment  of  a  hollow  sphere,  deeply  notched  on  the  inner  side,  and 

Flo;.  90. 


SACRO-ILIAC    AND   COXO-FEMORAL    ARTICULATIONS,    WITH    THE    SMALL   DEEP 
MUSCLES   SURROUNDING    THE    LATTER. 

1,  Saci'o-lliac  ligament ;  2,  Sacro-ischiatic  ligament ;  3,  Great  ischiatic  notch ;  4, 
Anterior  portion  of  the  capsular  ligament  of  the  coxo-femoral  articulation ;  5, 
Internal  band  of  cotyloid  ligament ;  6,  Coxo-femoral  ligament ;  7,  Pubio-femoral 
ligament;  8,  Its  insertion  into  the  femur;  9,  Small  gluteal  muscle;  10,  Origin 
of  the  straight  anterior  muscle  of  the  thigh  (rectus);  11,  Anterior  thin  muscle 
(rectus  parvus);  12,  Pyramidal  muscle  of  the  pelvis;  13,  External  obturator 
muscle;  14,  Square  crural  muscle  (quadratus  femoris);  15,  Inferior  sacro- 
coccygeal muscle. 

provided  at  the  bottom  with  a  wide  depression,  the  internal  moiety  of  which 
is  destined  for  the  insertion  of  one  of  the  interosseous  ligaments,  while  the 
external  half  plays  the  part  of  a  synovial  fossa.  This  depression  is  not 
covered  by  cartilage,  and  communicates  by  the  internal  notch  with  the 
inferior  furrow  on  the  pubis.  The  lip  of  the  cotyloid  cavity  is  covered  by 
a  complementary  fibro-cartilage — the  cotyloid  ligament.  This  fibro-cartilage 
is  not  interrupted  at  the  notch  just  mentioned,  but  passes  over  it,  forming  a 
remarkable  band  (Fig.  90,  5)  that  converts  it  into  a  foramen,  through  which 
pass  the  pubio-  or  ilio-femoral  ligament  and  the  vessels  of  the  articulation. 


162  THE  AR  TICULA  TIOXS. 

Fixed  by  its  adhercut  border  to  the  margiu  of  the  cotyloid  cavity,  this 
ligament  is  lined  by  synovial  membrane  on  its  faces  and  free  border.  It  is 
thickest  in  front  and  within. 

Witli  regard  to  tlie  head  of  the  femur,  it  will  be  remembered  that  it  is 
exactly  moulded  to  the  cavity,  and,  like  it,  is  excavated  by  a  rugged  fossa 
which  is  entirely  occupied  by  the  insertion  of  the  interarticular  ligaments. 

3Ijde  of  union. — This  joint  is  maintained  by  a  peripheral  ca^jsule,  and 
by  two  interarticular  bands  constituting  the  coxo-femoral  and  pubio-femoral 
ligaments. 

a.  Capsular  ligament  (Fig  90,  4). — This  is  a  membranous  sac,  like  that 
of  the  scapulo-humei-al  articulation,  embracing  the  head  of  the  femur  by  its 
inferior  oj^ening,  and  attached  by  its  opjjosite  aperture  to  the  margin  of  the 
cotyloid  cavity  and  its  protecting  fibro-cartilage.  This  ligament  is  com- 
posed of  intercrossed  fibres,  and  is  strengthened  in  front  by  an  oblique 
fasciculus  which  descends  to  the  body  of  the  femur,  along  with  the  anterior 
thin  muscle,  near  wliich  it  is  fixed.  Its  internal  face  is  covered  by  the  articular 
synovial  membrane,  and  its  external  face  is  in  contact,  through  the  medium 
of  adipose  cushions,  with  :  in  front,  the  anterior  thin  muscle  (crureus)  and 
the  straight  muscle  (rectus)  of  the  thigh ;  behind,  to  the  gemini,  the  intex'nal 
oblrurator,  and  the  pyramidal  muscles ;  outwards  and  upwards,  to  the  small 
gluteal  muscle ;  within  and  below,  to  the  external  obturator. 

h.  Coxo-femoral  ligament  (ligamentum  teres.  Fig.  90,  6).^ — ^A  thick  and 
short  funicle  of  a  triangular  shape,  deeply  situated  between  the  two  bony 
surfaces,  which  it  cannot,  notwithstanding  its  shortness,  maintain  exactly  in 
contact  without  the  other  muscular  or  ligamentous  structures  enveloping  the 
articulation.  Its  upper  insertion  occupies  the  internal  moiety  of  the  bottom 
of  the  cotyloid  cavity ;  and  its  inferior  extremity  is  confounded  with  the 
pubio-femoral  ligament,  being  fixed  with  it  into  the  rough  fossa  in  the  head 
of  the  femur.     It  is  enveloped  by  the  synovial  membrane. 

c.  Pablo  femoral  ligament  (Fig.  90,  7,  8). — This  ligament,  longer  and 
stronger  than  the  last,  originates  from  the  pubic  tendon  of  the  abdominal 
muscles  and  the  anterior  border  of  the  pubis.  Lodged  in  the  inferior 
channel  of  that  bone,  it  passes  outwards,  enters  the  internal  notch  of  the 
cotyloid  cavity,  is  inflected  downwards  on  the  fibrous  band  which  converts 
that  notch  into  a  foramen,  and  goes  witli  the  preceding  ligament  to  be 
inserted  into  the  fossa  in  the  head  of  the  femur.  Its  pubic  portion  lies 
between  the  two  branches  of  the  pectineus,  while  its  interarticular  surface 
is  covered  by  synovial  membrane. 

Synovial  membrane. — This  membrane  is  very  extensive;  it  lines  the 
internal  face  of  the  capsular  and  cotyloid  ligaments,  and  is  reflected  on  the 
interarticular  ligaments  to  form  around  them  a  serous  vaginal  covering.  It 
is  even  prolonged  into  the  synovial  fossa  occupying  the  centre  of  the  cotyloid 
cavity. 

Movements. — The  coxo-femoral  articulation  is  one  of  the  joints  wdiich  is 
endowed  with  the  most  varied  and  extensive  movements.  It  permits  the 
flexion,  extension,  abduction,  adduction,  circumduction,  and  rotation  of  the  thigh 
on  the  pelvis.  The  mechanism  of  these  movements  is  so  simple,  that  they 
need  no  particular  consideration. 

The  domesticated  animals  other  than  Snlipcds,  are  distinguished  by  the  complete  absence 
of  the  pubio-femoral  lijj;amf'nt;  so  that  in  tliem  the  movements  of  abduction,  which  are 
limited  in  Solipeds  by  tlie  tension  of  this  liizament.  are  much  more  extensive;  anil  it  is 
the  absence  of  the  liijament  in  question,  which  explains  the  facility  with  which  the  larger 
Rumiuanis  arc  enabled  to  strike  sideways,  a  movement  known  as  a  "  cow's  kick." 


ARTICULATIONS  OF  THE  POSTERIOR  LUIBS.  163 

In  Man,  the  head  of  the  femur  is  more  detached  than  in  the  domesticated  animal:?,  and 
the  Cotyloid  cavity,  encircled  by  the  cotyloid  lii.'aii)ent,  is  deeper.  The  femur  is  united 
to  the  coxa  :  1,  By  a  capsular  ligament ;  '2,  By  a  triangular  ligament,  tixed  above,  to  the 
cotyloid  ligament  at  the  notch,  and  IjcIow,  iuto  the  depression  in  tiie  head  of  the  femur. 
Al^o,  as  the  brothers  Weber  have  shown,  the  atmospheric  pressure  is  a  powerful  adjunct 
to  these  means  of  union. 

The  cuxu-femoral  articulation  of  Man  permits  more  extensive  movements  than  that  of 
animals,  and  especially  abduction  and  adductiun,  which  can  be  carried  to  90  degrees. 

3.  Femoro-tibial  Articulation} 

(Preparation. — Remove  the  soft  parts  surrounding  the  articulation,  taking  care  not  to 
wound  the  synovial  membrane.  To  expose  the  ciuci;d  ligaments,  make  an  antero- 
posterior vertical  section  vi  the  femur  in  such  a  way  as  to  separate  the  condyles.) 

This  is  the  most  complicated  joint  in  the  body,  and  is  formed  by  the 
union  of  the  femiu'  with  two  of  the  thigh  bones — the  tibia  and  iiateUa.  It 
represents  an  imj^erfect  hinge-joint. 

Articular  surfaces. — To  form  this  articulation,  the  femur  opposes  its  two 
condyles  to  the  wide,  convex,  and  undulated  facets  on  the  superior  face  of 
the  lateral  tuberosities  of  the  tibia,  and  its  articular  pulley  to  the  posterior 
face  of  the  patella. 

The  femoral  faces  have  ah-eady  been  described  in  detail  at  page  98  ;  but 
it  may  be  repeated  that  the  two  condyles,  placed  side  by  side,  are  elongated 
in  an  antero-posterior  direction,  and  are  separated  by  a  non-articular  notch 
called  the  intercondyloid ;  also,  that  the  femoral  trochlea  situated  in  front 
of  these  two  condyles  appears  to  continue  the  preceding  notch,  and  that  its 
internal  border  is  much  more  elevated  than  the  external ;  an  arrangement 
which  explains  why  it  is  so  difficult,  if  not  impossible,  for  the  patella  to  be 
dislocated  inwards. 

The  tibial  facets  ascend  on  each  side  to  the  lateral  faces  of  the  tibial 
spine.  They  are  seimrated  from  one  another  by  the  antero-posterior  groove 
cut  on  the  summit  of  that  bone,  and  by  the  fossas  of  insertion  sitiiated  at  its 
base  before  and  behind.  The  external  facet,  wider  than  the  internal,  is 
devoted  in  part  to  the  gliding  of  the  originating  tendon  of  the  popliteal 
muscle.  (See  page  100. j 

The  2)atellar  surface,  moulded  on  the  femoral  pulley,  fits  it  in  an  imper- 
fect manner.  It  is  bordered,  outwardly,  by  a  small  fibro-cartilaginous  ring, 
which  is  united  to  the  fibrous  capsule  of  the  femoro-patellar  articulation 
(Fig.  92,  1).  Inwardly,  it  is  completed  by  the  insertion  of  the  internal 
patellar  ligament,  to  be  noticed  immediately. 

Interarticnlar  meniscii  (semilunar  jihro-cartilages) — (Figs.  91,  No.  1,  2, 
3.  4;  and  1'2,  5,  6.  7,  8). — By  this  designation  is  known  the  two  fibro- 
cartilages  interposed  between  tlie  condyles  of  the  femur  and  the  tibial  facets, 
to  assure  their  coaptation.  They  are  crescent  shaped  bodies,  and  present : 
an  internal,  concave,  thin  and  sharp  border,  embracing  the  tibial  spine ;  an 
external,  thick,  and  convex  border  ;  a  superior  face,  excavated  and  moulded  to 
one  of  the  condyles ;  an  inferior  face,  nearly  plane,  gliding  on  the  tibia ;  and 
two  extremities  terminated  by  ligaments,  and  fixed  to  the  bones  in  apposition. 
The  articular  surfaces  are  not  entirely  separated  throughout  their  extent  by 

*  By  this  name  is  understood  the  joint  uniting  the  femur  to  the  tibia,  and  that  which 
articulates  it  with  tlie  patella.  Followin<r  the  example  of  anthropotomists,  it  has  not 
been  deemed  necessary  to  describe  a  femor(>p:itellar  articulation  distinct  from  the 
femom-tihiul,  properly  so  called.  This  innovation  appears  to  le  just  tied  by  the  com- 
munity of  the  principal  articular  bands  which  bind  these  two  joints,  and  by  the  reciprocal 
dependence  of  their  movements. 


164 


THE  AMTICULATI0N8. 


these  complementary  meniscii,  for  the  tibial  spine  rubs  directly  against  the 
inner  sides  of  the  femoral  condyles.  The  internal  semilunar  fihro-cartilage, 
the  widest  and  thickest,  is  inserted  by  its  anterior  extremity  into  one  of  the 
excavations  situated  in  front  of  the  spine  ;  its  posterior  extremity  is  attached 
in  the  fossa  behind  that  eminence.  The  external  semilunar  fihro-cartilage  is 
fixed,  in  front,  near  the  anterior  insertion  of  the  opposite  fibro-cartilage  ; 
its  posterior  extremity  gives  origin  to  two  slips  or  cords,  one  superior,  the 
other  inferior.  The  first,  the  strongest  and  longest,  terminates  in  the  fossa 
near  the  posterior  extremity  of  the  intercondyloid  notch.  The  second,  thin 
and  flat,  is  inserter)  on  the  posterior  outline  of  the  external  tibial  facet. 


Fis;.  91. 


No.  1 


No.  2. 


FEMORO-TIBIAL   ARTICULATION. 

No.  1.  Posterioi-  face  :  the  posterior  ligament  has  been  removed. — 1,  External  menis- 
cus; 2,  Fibrous  fasciculi  fixing  it  to  the  femur;  3,  Fibrous  fascia  which  attaches 
it  to  the  posterior  contour  of  the  tibial  surface ;  4,  Internal  meniscus ;  5,  Tibial 
insertion  of  the  posterior  crucial  ligament  j  6,  External  lateral  ligament ;  7, 
Internal  lateral  ligament. 

No.  2.  External  face  :  the  external  condyle  of  the  femur  and  the  meniscus  have  been 
removed  to  show  the  crucial  ligaments. — 1,  Anterior  crucial  ligament ;  2,  Posterior 
ditto  5  3,  Fibular  insertion  of  the  external  lateral  ligament ;  4,  Anterior  patellar 
ligaments. — A,  Internal  meniscus  ;  b,  Anterior  insertion  of  the  external  meniscus  •, 
C,  Passage  for  the  tendinous  cord  common  to  the  flexor  of  the  metatarsus  and  the 
anterior  extensor  of  the  phalanges ;  D,  Anterior  and  superior  tuberosity  of  the 
tibia  5  E,  Tibial  crest. 

The  external  border  of  this  meniscus  is  separated  from  the  external  lateral 
ligament  by  the  tendon  of  the  popliteus  muscle,  and  acts,  with  regard  to  this 
tendon,  as  a  pulley. 

Mode  of  union. — The  bands  which  bind  this  complicated  articulation  are 
very  numerous.  They  will  be  successively  described  as :  1,  Those  which 
attach  the  patella  to  the  tibia  ;  2,  Those  which  unite  the  femur  with  the  tibia. 

A.  Ligaments  attaching  the  jJatella  to  the  tibia. — The  patella  is  bound  to 
the  tibia  by  three  funicular  ligaments,  designated  by  the  generic  epithet  of 
"  patellar."     They  are  situated  in  front  of  the  articulation,  and  are  charged 


ARTICULATIONS  OF  THE  POSTERIOR  LIMBS.  1G5 

witli  the  duty  of  transmitting  to  the  leg  the  action  of  the  muscles  which  are 
attached  to  the  patella.  They  are  distinguished  according  to  their  position, 
as  external,  internal,  and  middle.  (Fig.  92,  2,  3,  4.) 

a.  The  external  imteUar  ligament,  the  largest  and  most  powerful,  is  a 
flattened  band,  attached,  by  its  lower  extremity,  to  the  cuhuinating  point  of 
the  anterior  tuberosity  of  the  tibia.  Its  upper  extremity  is  lixed  to  the 
anterior  face  of  the  patella,  and  is  confounded  with  the  patellar  insertion  of 
the  long  vastus  muscle.  It  is  joined  to  the  internal  ligament  by  a  very 
resisting  aponeurotic  expansion,  a  dependency  of  the  fascia  lata. 

b.  The  internal  patellar  ligament  also  forms  a  flattened  band,  longer,  but 
not  so  wide  or  thick  as  tlie  preceding.  Its  inferior  extremity  is  attached  to 
the  inner  side  of  the  anterior  tuberosity  of  the  tibia.  Its  superior  extremity 
becomes  much  thickened  and  fibro-cartilaginous,  and  is  inserted  into  a 
prominence  inside  the  patella.  This  fibro-cartilaginous  portion  (Fig.  92,  3') 
of  the  ligament  glides  on  the  internal  border  of  the  femoral  trochlea,  and 
may  justly  be  considered  as  a  comi)lementary  apparatus  of  the  patellar 
surface.  The  ligament,  joined  to  the  preceding  by  the  fibrous  fascia  already 
mentioned,  is  mixed  up,  inwardly,  with  the  aponeurosis  of  the  adductor 
muscles  of  the  leg. 

c.  The  middle  patellar  ligatnent  is  a  round  cord,  situated,  as  its  name 
indicates,  between  the  other  two,  concealed  beneath  the  aponeurosis  which 
unites  these,  and  in  the  middle  of  the  adipose  tissue  protecting  the  synovial 
capsules  in  front.  It  leaves  the  anterior  face  of  the  patella,  and  descends 
vertically  to  the  tibia,  to  be  lodged  in  the  fossa  in  the  middle  of  the  anterior 
tuberosity,  where  a  small  synovial  bursa  facilitates  its  movements. 
Its  inferior  extremity  is  inserted  into  the  most  declivitous  part  of  this 
excavation. 

!b.  Ligaments  ichich  attach  the  thigh  and  leg  hones. — These  are  six  in 
number :  1 ,  A  femoro-patellar  capsule  maintaining  the  patella  against  the 
femoral  trochlea  ;  2,  Five  femoro-tibial  ligaments,  as  follows :  two  lateral, 
two  external  and  internal ;  a  posterior ;  and  two  interarticular,  distinguished 
with  reference  to  their  inferior  insertion  into  anterior  and  posterior. 

a.  The  femoro-patellar  capsule  is  a  membranous  expansion  which  covers, 
above  and  laterally,  the  superior  synovial  membrane.  This  capsule  is 
attached  by  its  borders  around  the  femoral  trochlea  and  the  periphery  of  the 
patellar  surface.  It  is  extremely  thin  in  its  superior  part ;  but  laterally  it 
is  thicker,  and  constitutes  two  wide  fibrous  fasciculi  which  bind  the  patella 
to  the  eccentric  sides  of  the  two  condyles,  and  is  described  in  several  works 
as  two  special  ligaments.  Its  external  face  is  covered  by  the  insertion  of 
the  long  vastus  and  the  crural  triceps. 

6.  The  lateral  ligaments  are  two  ribbon -shaped  cords  situated  at  the 
extremities  of  the  transversal  axis  of  the  articulation,  more  behind  than 
before  ;  they  are  relaxed  during  flexion,  and  very  tense  in  extension. 

The  external,  the  shortest  and  strongest,  proceeds  from  one  of  the  hollow 
facets  on  the  external  condyle  of  the  femur,  and  is  inserted  into  the  head  of 
the  fibula  by  its  inferior  extremity,  after  gliding  over  the  external  tuberosity 
of  the  tibia  by  means  of  a  special  synovial  bursa.  It  is  covered  by  the 
crural  or  tibial  aponeurosis,  and  covers  the  tendon  of  the  popliteus,  from 
whicli  it  is  sometimes  separated  by  a  vesicular  synovial  membrane. 

The  internal  is  attached,  superiorly,  to  the  eminence   of  insertion  that 

surmounts  the  eccentric  face  of  the  internal  condyle,  and  descends  vertically 

to  the  tibia,  gliding  over  the  margin  of  its  articular  surface  by  means  of  a 

email  facet  covered  with  cartilage,  and  a   cul-de-sac   prolongation  of  the 

14 


166  THE  ARTICULATIONS.] 

internal  synovial  membrane.     It  is  fixed  by  its  inferior  extremity  to  the 
imprints  which  cover  the  internal  tibial  tuberosity. 

Its  fibres  are  disposed  in  two  layers,  which  slightly  intercross  in  X  fashion ; 
those  jiassing  downwards  and  forwards  adhere  to  the  border  of  the  internal 
meniscus.  Covered  by  the  aponeurosis  of  the  adductor  muscles  of  the  leg, 
this  ligament  adheres  by  its  deep  face  to  the  internal  meniscus. 

c.  The  posterior  ligament  belongs  to  the  class  of  membranous  or  capsular 
ligaments.  It  is  formed  of  two  aponeurotic  laminaa  separated  superiorly, 
but  confounded  infcriorly.  The  superficial  lamina  is  composed  of  strong, 
fibrous,  intercrossed  fasciculi,  perftu-ated  with  vascular  openings.  It  is  fixed, 
above,  to  the  posterior  face  of  the  femur,  below  the  external  gastrocnemius 
muscle.  The  deep  lamina  envelopes,  like  a  cap,  the  femoral  condyles. 
After  becoming  united,  these  two  laminfe  are  attached  to  the  posterior  face 
of  the  tibia,  closa  to  the  superior  articular  face  of  that  bone.  Its  external 
face  is  in  contact  with  the  popliteal  vessels,  and  the  external  gastrocnemius 
muscle.  Its  internal  face  is  covered  throughout  nearly  the  whole  of  its  extent 
by  the  lateral  synovial  membranes,  embraces  the  condyles  of  the  femur,  and 
adheres  to  the  posterior  crucial  ligament,  as  well  as  to  the  interarticular 
meniscii. 

d.  The  interosseous  ligaments  are  two  funicular  bands  lodged  in  the  inter- 
condyloid  notch.  They  are  more  commonly  designated  crucial  ligaments, 
becanse  they  cross  each  other  at  their  middle  j)art,  like  the  letter  X. 
(Fig.  91.) 

The  anterior,  oblique  downwards  and  forwards,  is  attached  by  its  superior 
extremity  to  the  bottom  of  the  intercondyloid  notch,  and  inwardly  to  the 
external  condyle.  Its  inferior  extremity  is  fixed  in  the  groove  on  the  summit 
of  the  tibial  spine.  The  fibres  entering  into  its  formation  are  not  parallel, 
but  slightly  twisted  in  a  spiral  manner. 

The  posterior,  longer  than  the  preceding,  and  oblique  in  the  opposite 
direction,  is  inserted,  inferiorly,  into  the  little  eminence  behind  the  internal 
tibial  facet ;  whence  it  goes  to  the  bottom  of  the  intercondyloid  notch,  to  bo 
attached  by  its  superior  extremity  within  the  internal  condyle. 

Synovial  memhranes. — For  this  articulation  there  are  three  synovial 
membranes  :  a  superior  and  two  lateral.  The  first,  very  large  and  sustained 
by  the  femoro-patellar  capsule,  facilitates  the  gliding  of  the  patella  on  the 
femoral  pulley ;  it  is  prolonged  in  a  cul-de-sac  below  the  insertion  of  the 
crural  triceps.  The  other  two,  which  lubricate  the  articular  surfaces  of  the 
projier  femoro-tibial  joint,  include  the  crucial  ligaments  between  them,  and 
cover  the  posterior  ligament,  the  lateral  ligaments,  and  the  fibrous  fasciculi 
for  the  attachment  of  the  meniscii.  The  external  covers,  in  addition,  the 
tendon  of  the  popliteus  muscle,  and  furnishes  a  vast  cwZ-f/e-sac  which  descends 
in  the  anterior  groove  of  the  tibia  to  envelop  the  tendon  common  to  the 
anterior  extensor  of  the  phalanges  and  the  flexor  of  the  metatarsus.  These 
two  femoro-tibial  synovial  membranes  lie  against  that  of  the  femoro-patellar 
articulation,  in  front  of  the  condyles  and  the  notch  which  separates  them, 
and  if  not  always,  at  least  not  unfrequently,  they  communicate  with  it.  The 
three  are  separated  from  the  ligaments  of  the  patella  by  a  considerable  mass 
of  adipose  tissue  which  is  prolonged  into  the  intercondyloid  notch,  at  the 
bottom  of  which  it  appears  to  be  fixed. 

Movements. — This  imperfect  hinge  joint  can  execute  the  two  principal  and 
opposite  movements  of  ^/Zex/on  and  extension,  sinCi  a  somewhat  limited  acces- 
sory movement  of  rotation.  The  mechanism  of  these  movements  being 
simple  enough  to  be  readily  understood  without  any  preliminary  explanation, 


AETICULATIOXS  OF  TEE  POSTERIOR  LUIBS.  167 

they  will  not  be  detailed  here ;  but  some  remarks  will  be  made  with  regard 
to  the  displacement  the  tibro-cartilages  undergo  when  the  articulation  is  in 
motion. 

During  flexion  and  extension,  tliese  bodies,  fixed  on  the  tibial  facets,  which 
they  transform  into  glenoid   cavities, 

move  with  them  on  the  condyles  of  the  Fig.  92. 

femur,  from  before  to  behinil,or  behind  ^*'-  1-  ^o.  2. 

to  before,  according  to  the  movement 
executed.  But  at  the  same  time  they 
also  gli<le  in  an  inverse  direction,  and 
to  a  very  appreciable  degree,  on  the 
superior  extremity  of  the  tibia.  There- 
fore, during  flexion,  they  pass  from 
behind  forward  on  this  extremity,  and 
are  drawn  backwards  during  exten- 
sion. 

In  rotation,  which  may  take  place 
from  within  to  without,  or  from  with- 
out to  within,  the  movement  is  pro- 
duced not  only  by  the  pivoting  of  the 
condyles  in  their  glenoid  cavities,  but 
also  by  a  sensible  displacement  of  the 
meniscii  on  the  tibial  surfaces. 

In  the  Bog  and  Cat,  the  meniscii  are 
joined  together  near  their  anterior  insertion 
by  a  transverse  fibrous  baud.  There  is  only 
one  patellar  ligament,  and  the  posterior  liga- 
ment shows  in  its  thickness  two  small  sesa- 
moid bones  against  which  the  condyles  of 
the  femur  play  inwardly,  and  which  give 
attachment,  outwardly,  to  the  originaiing 
branches  of  the  external  gastrocnemius  mus- 
cle. There  is  no  femoro-pati^lar  capsule,  and 
only  one  sjTiovial  membrane  for  the  whole 
articulation. 

In  the  Pig  and  Sheep,  there  is  also  only 
one  ligament  and  one  synovial  capsule. 


4.   Tibio-flbular  Articulation. 

This  articulation  represents  a  small 
planiform  diarthrosis,  whose  move- 
ments are  very  limited  and  obscure. 
It  is  formed  by  the  union  of  the  irre- 
gular diarthrodial  facet  which  occupies 
the  internal  face  of  tbe  head  of  the 
fibula,  with  the  analogous  facet  on  the 
external  superior  tuberosity  of  the 
tibia.  Short  and  strong  interosseous 
or  pei'ipheral  fibres  envelop  these 
facets  on  every  side,  and  maintain  them 
firmly  in  contact. 

The  fibula  is  also  attached  to  the  tibia:  "1,  Above,  by  two  small  liga- 
mentfjus  fasciculi  crossed  like  the  letter  X,  which  form  the  superior  part  of 
the  great  arch  through  which  pass  the  anterior  tibial  artery  and  vein  (Fig. 
92,  12) ;  2,  In  the  middle,  by  a  kind  of  aponeurotic  membrane,  whose  width 


LIGAJIEXTS   ATTACHING  THE   THREE   BONES 
OF    THE    LEG. 

No.  1.  Posterior  face. — No.  2.  Anterior  face. 
— 1,  Complementary  fibro-cartilaginous 
pad  of  the  patellar  surfoce ;  2,  External 
patellar  ligament;  2',  Insertion  of  the  long 
vastus  into  this  ligament ;  3,  Internal 
patelhir  ligament ;  3',  Its  upper  insertion 
transformed  into  a  complementary  appa- 
ratus of  the  patellar  surface  ;  4,  Jliddle 
patellar  ligament ;  5,  External  meniscus 
of  the  tibia ;  6,  Its  branch  of  insertion 
into  the  fenmr  cut  off  at  its  origm :  7,  Its 
posterior  tibial  insertion  ;  8,  External  me- 
niscus; 9,  Insertion  of  the  anterior  crucial 
ligament  into  the  fossa  of  the  tibial  sjjine; 
10,  Tibial  insertion  of  the  posterior  crucial 
ligament ;  11,  Inferior  insertion  of  the  ex- 
ternal femoro-tibial  ligament;  12,  13,  14, 
Tibio-fibular  ligaments. — a,  Tibial  arch; 
B,  Surface  of  insertion  of  the  popliteus 
muscle;  C,  Surface  of  insertion  for  the 
perforans  muscle. 


168  THE  ARTICULATIONS. 

diminislies  from  above  to  below,  like  that  of  the  space  it  fills  (Fig.  92,  13)  ; 
3,  Below,  by  a  ligamentous  cord  (Fig.  92,  14)  which  prolongs  the  fibula  to 
the  external  tuberosity  of  the  inferior  extremity  of  the  tibia,  where  this  cord 
bifurcates,  and  is  united  to  the  two  external  lateral  ligaments  of  the  tibio- 
tarsal  articulation." — Bigot. 

In  till-  Or,  Sheep,  and  Goaf,  the  fibula  being  replaced  by  a  ligament,  there  is  no 
proper  tiliio-fibnlur  articulation. 

J  u  the  Dog  and  Cat,  the  two  principal  bones  of  the  log  are  united  at  their  extremitie» 
and  mil li lie  part: 

1.  At  tluir  superior  extremity,  by  means  of  a  small  arthrodial  articulation,  analogous 
to  that  of  the  Horse,  and,  like  it,  provided  with  a  particular  synovial  bursa  ; 

2.  At  their  inferior  extremity,  by  means  of  a  second  arthrodial  articulation,  whose 
action  is  facilitated  by  a  prolongation  of  tiie  tibio-tarsal  synovial  membrane ; 

3.  By  their  midille  jjart,  through  the  interposition,  between  the  two  bones,  of  an 
interosseous  ligament,  which  is  wide  and  membranous  in  its  upper  two-thirds,  and  formed 
of  extremely  short  and  strong  fibres  at  its  lower  third. 

In  the  Pig,  the  arrangement  is  somewhat  the  same  as  in  Carnivora.  It  may  be  noted, 
however,  that  the  facet  of  the  upper  extremity  of  tlie  fibula  is  joined  to  the  tibia  by  a 
small  interosseous  ligament,  and  that  the  articulation  which  results  should  be  looked 
upon  as  a  small  ampliiarthrosis. 

In  Man,  as  in  the  Dog  there  are  two  feroneo-iihial  arlhrodix:  a  superior  and  inferior. 

5.  Articulations  of  the  Tarsus  or  Hock. 

[Freparation. — Eemove  the  tendons  from  around  the  articulation,  and  incise,  layer 
after  layer,  the  superficial  fibres  of  the  lateral  ligaments.) 

These  comprise:  1,  The  tibio-tarsal  articulation;  2,  The  articulation  of 
the  first  row  of  bones — the  astragalus  and  calcis  ;  3,  Those  which  unite  the 
bones  of  the  lower  row ;  4,  The  articulation  of  the  two  rows  with  each 
other ;  5,  The  tarso-metatarsal  articulation.  The  first  is  a  perfect  gingly- 
moid  and  the  only  joint  really  movable  ;  all  the  others  are  arthrodial,  and 
their  action  is  so  restricted  that  they  appear  to  be  condemned  to  almost 
absolute  immobility.  This  intimate  union  of  the  tarsal  and  metatarsal 
bones  is  evidently  chiefly  intended  to  guarantee  precision  in  the  movements 
of  the  tibio-tarsal  articidation. 

TiBio-TAHSAii  Articulation. — Two  bones  alone  concur  in  the  formation 
of  this  angular  gingiymoid  joint  :  these  are  the  tibia  and  astragalus. 

Artiadar  surfaces. — For  the  tibia  :  1,  The  two  deep  grooves,  oblique 
forwards  and  outwards,  channeled  in  the  inferior  extremity  of  the  bone  ;  2, 
The  salient  tenon  which  separates  these  grooves,  and  on  which  there  is  often 
a  small  synovial  fossette. — For  the  astragalus,  the  pulley  occujiying  its 
anterior  face  (see  page  103). 

3Inde  of  union. — Seven  ligaments  bind  these  articulations  :  two  external 
lateral,  three  internal  lateral,  an  anterior  and  a  posterior. 

«.  External  lateral  ligaments. — These  are  distinguished,  according  to  their 
relative  position,  into  superficial  and  deep. 

The  external  superficial  ligament  (Figs.  93,  2 ;  94,  2),  is  a  thick 
funicular  cord,  flattened  in  its  inferior  half.  It  commences  above  on  the 
eyternal  tuberosity  of  the  tibia,  behind  the  groove  which  divides  this  tube- 
rosity into  two  parts  ;  from  thence  it  descends  almost  vertically,  fixing  itself 
successively  to  the  astragalus,  calcaneus,  cuboides,  middle  metatarsal  bone, 
and  the  external  rudimentary  metatarsal  bone.  Passing  in  front  with,  and 
partly  covered  by,  the  lateral  extensor  of  the  phalanges,  to  which  it 
supplies  a  retaining  band  (Fig.  94,  2),  this  ligament  is  confounded  behind, 
and  near  its  inferior  extremity,  with  the  calcaneo-metatarsal  ligament.     It 


ARTICULATIONS  OF  THE  POSTFTiTOU  LmPS. 


169 


Fig.  93. 


covers  the  external  and  deep  ligament,  the  short  band  which  constitutes  the 
external  calcaueo-astragaloid  ligament,  the  insertion  of  one  of  the  branches 
of  the  flexor  of  the  metatarsus,  and  the  small  cuboido-cimean  (cuneiform) 
ligament. 

The  external  deep  ligament  (Figs.  93 ;  94,  1),  much  shorter  than  the 
preceding,  is  attached,  superiorly,  to  the  anterior  part 
of  the  external  tuberosity  of  the  tibia,  and  is  directed 
obliquely  backwards  and  downwards,  to  be  fixed  by 
two  fasciculi  at  the  external  side  of  the  astragalus 
and  calcis.  This  ligament,  covered  by  the  preceding, 
which  crosses  it  like  an  X.  is  lined  un  its  inner  face 
by  the  synovial  membrane  of  the  articulation. 

h.  Interna^  lateral  ligaments. — These  are  also  three 
funic  uhu'  bands  superposed  on  one  another,  and  are 
consequently  designated  as  superficial,  middle,  and 
deeji. 

The  infernal  superficial  ligament  (Fig.  93,  6),  the 
strongest  and  longest  of  the  three,  proceeds  from 
the  internal  and  inferior  tuberosity  of  the  tibia, 
diminishing  as  it  descends  on  the  inner  side  of  the 
tarsus.  It  is  fixed,  in  mixiug  with  the  astragalo- 
metatarsal  ligament  and  with  the  posterior  tarso- 
metatarsal ligamentous  arrangement,  to  the  tuberosity 
of  the  astragalus,  the  scaphoid,  the  two  cuneiform,  the 
superior  extremity  of  the  principal  metatarsal,  and  •  taesal  articclations; 
that  of  the  internal  rudimentarv  metatarsal  bones.  ^^^^  ^  ^^^  * 

The  internal  middle  ligament  (Fig.  93,  5)  is  com-  1'  External  deep  ligament 
posed  ot  two  funicular  cords,  attached  m  common  ticulation-  2  2.  Ex- 
beneath  the  preceding  ligament  to  the  internal  tibial 
tuberosity.  These  two  fasciculi,  exactly  resembling 
those  of  the  external  deep  ligament,  are  directed 
do«"nward  and  backward,  and  terminate,  one  at  the 
astragalus,  the  other  at  the  calcis. 

The  internal  deep  ligament  (Fig.  93,  4)  is  an  ex- 
tremely slender  fasciculus,  enveloped  by  the  synovial 
membrane ;  it  is  often  reduced  to  a  thin  shred, 
scarcely  distinct  from  the  serous  covering  surround- 
ing it.  It  is  attached,  in  one  direction,  to  the  tibia 
below  the  middle  ligament ;  in  the  other  to  the 
astragalus,  and  nearly  at  the  same  point  as  the 
superior  fasciculus  of  the  middle  ligament. 

c.  Anterior  ligament. — This  is  a  membraniform  band  formed  of  inter- 
crossed fibres,  stronger  outwards  than  inwards,  attached  by  its  upper  border 
above  and  in  front  of  the  tibial  surface,  fixed  by  its  inferior  border  to  the 
astragalus,  the  scaphoid  and  gi-eat  cuneiform  bones,  and  the  astragalo- 
metatarsal  ligament ;  it  is  confounded  at  its  sides  with  the  two  sui)erficial 
lateral  ligaments.  Its  internal  face  is  lined  by  articular  synovial  mem- 
bi-ane,  while  the  external  is  covered  by  the  flexor  of  the  metatarsus,  the 
anterior  extensor  of  the  phalanges,  the  anterior  tibial  artery,  and  several 
lai'ge  anastomosing  veins  from  whose  junction  arises  the  anterior  tibial 
vein. 

d.  Posterior  ligament. — This  is  the  second  membraniform  or  capsular 
band  which  protects  the  ai-ticulation  posteriorly.     It  presents,  in  its  centre, 


ternal  superficial  liga- 
ment ;  4,  Internal  deep 
ligament ;  5,  Internal 
middle  ligament ;  6,  In- 
ternal superficial  liga- 
ment ;  7,  Astragalo- 
metatarsal  ligament ;  8, 
Small  cuboido-cunean 
ligament. — A,  Pulley  of 
the  astragalus  ;  B,  Cu- 
boidal  insertion  belong- 
ing to  the  tendinous  cord 
of  the  flexor  of  the  me- 
tatarsus ;  C,  Vascular 
canal  of  the  tarsus. 


170  THE  ARTICULATIONS. 

a  fibro-cartilaginous  thickening,  on  which  glides  the  perforans  tendon.  It 
is  attached,  above,  to  the  tibia,  below,  to  the  astragalus  and  calcis ;  at  its  sides 
it  is  mixed  with  the  two  superficial  lateral  ligaments,  and  the  astragalian 
fasciculus  of  the  middle  internal  ligament.  Its  internal  face  is  lined  by- 
articular  synovial  membrane ;  the  external  is  covered  and  lubricated  by  the 
vaginal  serous  membrane  which  facilitates  the  gliding  of  the  perforans 
tendon  in  the  tarsal  sheath. 

Synovial  membrane. — This  membrane  is  developed  at  the  internal  face 
of  the  two  capsular  ligaments,  nearly  covers  the  three  internal  ligaments, 
and  lines  the  external  deep  ligament.  It  communicates,  in  front  and  below, 
with  the  synovial  membrane  proper  to  the  articulation  of  the  two  rows  of 
tarsal  bones.  When  it  becomes  the  seat  of  dropsical  effusion,  it  is  always 
distended  forwards  and  inwards,  because  it  is  only  sustained  at  that  place 
by  the  anterior  capsular  ligament.  But  the  effusion  may  also  raise  the 
posterior  ligament  and  produce  hernia  in  the  hollow  of  the  hock,  behind  the 
lateral  ligaments.  It  is  not,  therefore,  absolutely  correct  to  attribute  all  the 
synovial  tumours  in  the  hollow  of  the  hock  to  dilatation  of  the  tarsal 
tendinous  sheath. 

Movements. — Nothing  can  be  less  complicated  than  the  mechanism  of  the 
tibio-tarsal  articulation  ;  this  joint  only  permitting  two  opposite  movements, 
those  oi  flexion  and  extension,  which  are  so  simple  and  precise  that  we  may 
disjjense  with  a  description  of  the  manner  in  which  they  are  executed.  It 
may  only  be  remarked  that,  in  order  to  prevent  contact  between  the  leg 
and  foot  during  flexion,  the  latter  fraction  of  the  limb  deviates  a  little 
outwards,  owing  to  the  marked  obliquity  of  the  articular  grooves. 

Articulation  of  the  Bones  of  the  First  Row,  or  Calcaneo- 
ASTRAGALOiD  ARTICULATION. —This  is  a  compound  arthrodial  joint,  resulting 
from  the  coaptation  of  the  three  or  four  articular  facets  of  the  posterior  face 
of  the  astragalus  with  the  analogous  facets  of  the  calcis. 

This  joint  is  maintained  by  the  lateral  ligaments  of  the  tibio-tarsal 
articulation,  and  by  four  calcaneo-astragaloid  ligaments — a  superior,  external, 
internal,  and  the  last  interosseous. 

The  superior  calcaneo-astragaloid  ligament  is  formed  of  short  parallel 
fibres  thrown  across  from  one  bone  to  the  other,  and  is  situated  towards  the 
superior  extremity  of  the  pulley  of  the  astragalus  ;  it  is  lined  superiorly  by 
the  synovial  membrane  of  the  tibio-tarsal  articulation. 

The  lateral  ligaments  are  two  very  thin  fasciculi  concealed  by  the 
ligaments  which  bind,  laterally,  the  tibia  to  the  tarsal  bone. 

The  interosseous  ligament  is  very  strong,  and  occupies  a  great  portion  of 
the  rugged  excavation  which  separates  the  articular  facets. 

This  articulation  does  not  usually  possess  proper  synovial  capsules. 
Two  prolongations  of  the  synovial  membrane  of  the  two  rows,  in  ascending 
between  the  calcis  and  astragalus,  facilitate  the  gliding  of  the  two  inferior 
facets.  An  analogous  prolongation  of  the  tibio-tarsal  synovial  membrane  is 
effected  for  the  superior  facets,  and  it  is  not  rare  to  find  this  prolongation 
form  a  distinct  capsule. 

Movements  nearly  null 

Articulation  of  the  Bones  op  the  Second  Row  with  each  other. — 
These  bones,  four  in  number,  are  brought  into  contact  in  the  following 
manner  : — The  cuboides  responds  to  the  scaphoid  by  two  facets,  one  anterior, 
the  other  posterior ;  it  articulates  with  the  great  cuneiform  by  two  similar 
facets,  the  posterior  of  which  is  not  always  present.  The  scaphoid  is  united 
to  the  two  cuneiforms  by  the  large  convex  facet  occupying  its  entire  lower 


ARTICULATIOXS  OF  THE  POSTERIOR  LIMBS. 


171 


¥is.  94. 


face.      The   two   cuneiforms   are  joined   by   means   of  a   small   articular 
surface. 

The  fibrous  fasciculi  wbicli  maintain  the  diartbrodial  surfaces  in  contact 
are  somewhat  numerous.     They  are  as  follows ; 

1.  The  astragalo-metatarsal  ligament  and  tarso-metatarsal  apparatus, 
which  will  be  described  hereafter ;  these  two  bands  do  not  properly  belong 
to  the  articulations  of  the  second  row  of  bones. 

2.  Two  anterior  ligaments,  named  cuhoido-scapJioid  and  ciiboido-cunean 
(Figs.  93,  8 ;  94,  5),  which  are  carried  from  the  cuboid  to  the  scaphoid 
and  to  the  great  cuneiform  bone,  one  above, 
the  other  below  the  vascular  channel  formed 
between  these  three  bones. 

3.  Two  interosseoiis  ligaments  analogous 
to  the  preceding  two,  forming  the  sui^erior  and 
inferior  walls  of  the  aforesaid  channel. 

4.  An  interosseous  scaphoido-cunean  liga- 
ment, passing  from  the  scaphoid  to  the  two 
cuneiform  bones. 

5.  An  interosseous  ligament,  named  the 
intercunean,  is  directed  from  one  cuneiform 
bone  to  the  other,  and  is  confounded  with  the 
preceding  ligament. 

The  disposition  of  the  lubricating  mem- 
branes varies  with  that  of  the  articular  facets. 
The  following  is  what  is  most  generally 
observed : — A  proper  synovial  membrane  is 
specially  destined  for  the  facets  by  which  the 
scaphoid  and  great  cuneiform  bones  correspond ; 
this  synovial  membrane  belongs  also  to  the  two 
cuboido-scaphoid  and  posterior  cuboido-cunean 
arthrodije.  The  anterior  cuboido-scaphoid  diai'- 
throsis  receives  a  jn-olongation  from  the  syno- 
vial membrane  of  the  two  rows.  The  play  of 
the  anterior  cuboido-cunean  and  intercunean 
facets  is  facilitated  by  two  prolongations  of 
the  tarso-metatarsal  synovial  membrane. 

Movements  almost  null. 

Aeticulation  of  the  two  Eows  with  each 
OTHER. — This  arthrodial  joint  is  formed  by  the 
union  of  the  calcis  and  the  astragalus,  on  the 
one  side,  with  the  scaphoid  and  cuboid  bones 
on  the  other.  Its  solidity  is  assured  by  six 
princdpal  bands : 

1.  The  two  lateral  superficial  ligaments  of 
the  tibio-tarsal  articulation. 

2.  The  calcaneo-metatarsal  ligament  (Fig. 
94,  3),  a  strong  fibrous  brace  which  unites  the 
posterior  border  of  the  calcis  to  the  cuboides.  and  to  the  head  of  the  external 
rudimentary  metatarsal  bone.  It  is  confounded,  outwardly,  with  the  external 
and  superficial  tibio-tarsal  ligament ;  inwardly,  with  the  posterior  tarso- 
metatarsal band. 

3.  The  asfragalo-metafarsal  ligament  (Fig.  93,  7),  a  radiating  fasciculus 
whose  fibres  leave  the  internal  tuberosity  of  the  astragalus,  become  mixed 


ARTICULATIONS  OF   THE    TARSUS; 
LATERAL   VIEW. 

1,  External  deep  ligament ;  2, 
External  superficial  ligament ; 
2',  Ring  furnished  by  the  latter 
ligament  for  the  passage  of  the 
lateral  extensor  tendon  of  the 
phalanges ;  3,  Calcaneo-meta- 
tarsal ligament ;  4,  Astragalo- 
metatarsal  ligament ;  5,  Small 
cuboido-cunean  ligament. — A, 
Cuboidal  insertion  of  the  flexor 
muscle  of  the  metatarsus;  B, 
Anterior  orifice  of  the  vascular 
conduit  of  the  tarsus ;  c,  Groove 
on  the  external  tuberosity  of 
the  tibia  for  the  gliding  of  the 
lateral  extensor  of  the  pha- 
langes ;  D,  Insertion  of  the  gas- 
trocnemius tendon  of  the  leg 
into  the  os  calcis ;  E,  Gliding 
surface  for  that  tendon. 


172  THE  ARTICULATIONS. 

up  with  the  internal  and  superficial  tibio-tarsal  ligaments  in  diverging  down- 
wards to  the  scaphoides,  the  great  cuneiform  bone,  and  the  upi)er  extremity 
of  the  priucipal  metatarsal  bone. 

4.  The  posterior  iarso-metatarsal  ligament  is  a  vast,  very  strong,  and  very 
comiDlicated  fibrous  arrangement,  which  binds,  posteriorly,  all  tlie  tarsal 
bones,  and  also  fixes  them  to  the  three  portions  of  the  metatarsus.  This 
band,  which  is  crossed  by  several  tendons  aud  by  the  artery  and  vein  lodged 
in  the  cuboido-scaphoido-cunean  canal,  is  continued  below  by  the  tarsal 
stay  of  the  perforaus  tendon.  It  therefore  closely  resembles  the  posterior 
carpal  ligameut.  Its  posterior  face  is  covei-ed  by  the  tendinous  synovial 
membraue  lining  the  tarsal  sheath  for  the  passage  of  the  perforans  tendons. 
It  is  confounded,  on  its  sides,  with  the  calcaneo-metatarsal,  and  the  internal 
and  superficial  tibio-tarsal  ligaments. 

5.  An  interosseous  ligament,  attached  to  the  four  bones  composing  this 
articulation. 

It  is  provided  with  a  particular  synovial  membrane  which  always 
communicates,  in  front,  with  the  tibio-tarsal  capsule.  This  membrane  is 
prolonged,  superiorly,  between  the  calcis  and  astragalus,  to  lubrify  two  of 
the  facets  by  which  these  bones  come  into  contact ;  and,  in  addition,  it 
descends  between  the  cuboid  and  scaphoid  bones  to  form  a  third  pro- 
longation for  the  anterior  cuboido-scaphoid  arthrodia. 

Movements  almost  null. 

Tarso-metatarsal  Articulation. — This  joint,  formed  by  the  meeting  of 
the  three  tarsal  bones — the  cuboid  and  the  two  cuneiforms — with  the  three 
bones  of  the  metatarsus,  is  fixed  by  the  lateral  superficial  ligaments  of  the 
tibio-tarsal  articulation,  the  calcaneo-metatarsal  ligament,  those  which  have 
been  named  the  astragalo-metatarsal  and  tarsometatarsal,  aud  by  a  strong 
interosseous  ligameut  which  naturally  forms  three  fasciculi. 

The  synovial  membraue  proper  to  this  joint  ascends  into  the  small 
anterior  cuboido-cunean  arthrodia,  and  into  that  which  unites  the  two 
cuneiform  bones ;  it  descends  to  the  intermetatarsal  articulations. 

Movements  nearly  null. 

In  all  tlie  domesticated  animals  except  Solipeds,  the  tarsal  artionlations  offer  some  diffe- 
rential peculiarities  whose  study  is  without  interest,  as  it  is  without  utility.  It  is  only 
necessary  to  remark  that  the  immobility  of  the  tarsal  joints,  properly  called,  is  less 
absolute  than  in  Solipeds,  owing  to  the  peculiar  con  figuration  of  the  articular  surfaces  of 
some  of  the  bones  composing  them.  Thus,  in  the  O.r,  Sheep,  Goat,  and  Fig,  the  calcis 
is  joined  to  the  astragalus  by  a  real  trochlear  articulation,  and  the  latter  bone  is  united 
to  the  scaphoid  by  a  diarthrodial  joint  of  the  same  kind;  a  mode  of  articulation  much 
more  favourable  to  motion  than  that  of  tlie  planiform  diarthrodial  joint.  In  the  Dog  and 
Cat,  the  same  result  is  obtained  by  the  reception  of  the  head  of  the  astragalus  into  the 
superior  cavity  of  the  scaplioids. 

In  Itmninanis  and  the  Fig,  it  is  also  observed  that  the  tibio-tarsal  articulation  is 
formed  by  the  tibia  and  fibula  in  the  one  direction,  and  by  the  astragalus  and  os  calcis 
in  the  other. 


CHAPTEK  III. 

OF   THE   ARTICULATIONS   IN   BIRDS. 

The  study  of  the  articulations  in  birds  will  only  arrest  us  for  a  few  moments,  as  it 
will  be  confined  to  some  remarks  on  the  intervertebral  oceipito-atloid  and  tcmporo- 
maxillary  joints,  the  only  ones  exhibiting  a  special  conformation  worthy  of  attention. 

Intervertebral  articuhtions. — The  great  mobility  of  the  n(ck  of  birds  is  not  only  due 
to  the  fact  of  its  length,  relatively  considcn d.  but  also  to  the  peculiar  manner  in  which 
the  vertebraj  of  this  portion  of  the  spinal  stalk  are  articulated.    It  will  be  remarked  that 


ARTICULATIOXS  IX  BIRDS.  173 

these  do  not  unite  by  their  bodies  in  the  form  of  a  continuous  series  of  amphiarthroses, 

as  in  the  domesticated  mammals;  but  that  instead  of  these  mixed  articulations  there  are 
veritable  diarthroses,  which  may  be  included  in  the  Class  created  by  Cruveilhier  imder 
the  title  of  articulation  by  reciprocal  ball  and  socket,  each  veitebra  becoming  connected 
•with  the  adjact-nt  vertebne  by  means  of  facets  convex  in  one  sense  and  concave  in  the 
sense  perjieudiciilar  to  the  first.  These  facets  are  manifestly  covered  by  c.irtilai^e  of 
incrustation ;  and  it  appears  that,  instead  of  their  being  applied  directly  against  the 
opposite  facets,  which  pieseut  a  precisely  inverse  conforraatiou,  they  are  separated  bv 
an  extremely  tliin  fibro-cartilaginous  disc,  which  resembles  the  interosseous  meniscus  of 
the  temjioro-maxillary  articulntiou  in  the  Carnivora  of  the  Cat  species.  Two  loose 
synovial  capsules,  separated  by  tliis  interarticular  lamina,  complete  the  framework  of 
each  articulation,  and  favour  the  play  of  the  vertebrse  on  one  another.  This  arrange- 
ment has  only,  so  far  as  we  are  aware,  been  observed  in  the  swan,  and  that  very 
imperfectly;  but  it  probably  belongs  t.)  the  entire  class  of  birds,  for  until  now  we  have 
met  with  it  in  all  the  individuals  submitted  to  examination. 

In  its  dorso-lumbar  and  sacral  porlicm,  the  spine  is  a  single  piece,  in  consequence  of 
the  consolidation  of  the  vertebrae,  and  does  not  show  any  projjer  articulations. 

In  the  coccygeal  region,  the  mobility  of  the  :*pine  re-appears ;  but  it  is  far  from  being 
60  marked  as  in  the  cervical  region ;  the  vertebrae  here  are  united  by  amphiarthrosis,  and 
not  l>y  reciprocal  ball  and  socket. 

Oecipito-atloid  articulation.~lt  has  been  sbown  that  there  is  only  one  more  or  less 
spheroidal  condyle  of  the  occipital  bone,  and  a  single  cavity  on  the  interior  margin  of 
tlie  spinal  canal  of  the  atlas.  The  oecipito-atloid  articulation  is  Iherelore  a  true  enar- 
throsis,  with  varied  and  very  extensive  movements;  a  disposition  which  accounts  for 
the  facility  with  which  birds  can  pivot  their  heads  on  the  superior  extremity  of  the 
vertebral  stalk. 

Temporo-maxillary  articulation. — The  play  of  this  articulation  offers  one  peculiarity 
in  that  it  causes,  during  the  separation  of  the  mandibles,  not  only  the  depression  of  the 
inferior,  but  also  the  elevation  of  the  superior  mandible.  The  arrangement  which  permits 
this  movement  has  been  aheady  made  known ;  but  yet  it  is  dithcult  to  understand,  be- 
cause there  is  no  active  agent,  no  proper  muscle  to  directly  eflect  it.  Nevertheless,  the 
meclmnism  which  executes  it  is  most  simjile,  and  may  be  given  in  a  few  words:  Thus, 
We  know  that  the  square  bone,  interposed  betwii-u  the  temporal  nnd  maxillary  bones, 
like  the  interarticular  n.eniscus  of  mammals,  is  united  outwardly  with  the  jugiil  bone, 
and  inwardly  with  the  pterygoid.  We  know  also  that  the  latter  rests,  by  means  of  a 
diarthrodial  facet,  on  the  body  of  the  sphenoid,  and  that  it  abuts  against  the  posterior 
extremity  of  the  palate  bones ;  while  the  first,  the  zygomaticus,  is  joined  directly 
to  the  supermaxillary  bone.  The  superior  jaw,  it  is  also  known,  is  movable  on 
the  cranium,  because  of  the  flexibility  of  the  cartilages  or  bony  plates  uniting  these  two 
portions  of  the  head.  It  may  then  be  added,  that  the  square  bone  receives  on  its  anterior 
process  one  or  two  small  muscles  which  are  attached  to  the  base  of  the  cranium,  and  that 
these  bones  may  be  pushed,  or  rather  drawn  forward,  by  ti.e  contraction  of  the.<e  muscular 
fasciculi.  It  is  this  projecting,  or  pushing,  transmitted  to  the  upper  mandible  through 
the  medium  of  the  jugal  bone  on  the  one  side,  and  the  pterygoid  bone  on  the  other,  thi.t 
produces  the  elevation  of  that  mandible. 

Nothing  is  easier  than  to  prove  it  :  it  is  only  necessary  to  take  the  head  of  a  bird, 
denude  it  of  all  its  tolt  parts,  and  press  with  the  fingers  I  ehind  the  two  square  bones, 
to  imitate  the  action  of  tiie  elevator  muscles;  we  then  see  tlie  internal  extremity  of  the 
pterygoid  bone  glide  on  the  tacet  of  the  sphenoid,  and  push  before  it  the  palatine  bone, 
during  which  the  zygomatic  bone  acts  in  the  same  manner  on  the  maxillary ;  and  in  this 
way  is  produced,  through  the  influence  ot  this  postero-auterior  propulsion,  the  ascending 
movement  we  undertook  to  explain. 


THIRD  SECTION. 
The  Muscles. 

After  the  study  of  the  bony  levers  and  their  articulations,  comes  the 
description  of  the  agents  whose  function  it  is  to  move  them.  Tlicse  are  the 
muscles,  fibrous  organs  possessing  the  property  of  contracting  under  the 
influence  of  a  stimulus. 


174  THE  MUSCLES. 

They  arc  distinguished  as  striated  (or  striped)  and  non-striated  (or 
unstriped)  muscles,  accoi'ding  to  the  character  of  the  anatomical  element 
composing  them. 

The  non-striated  (or  unstriped)  muscles  are  removed  from  the  influence  of 
the  will,  and  belong  to  the  organs  of  vegetative  life.  They  are  also 
designated  as  internal  muscles,  or  muscles  of  onjanic  life. 

The  striated  (or  striped)  muscles,  ditFer  ivova.  the  first  in  that,  with  the 
exception  of  the  fleshy  tissue  of  the  heart,  their  contractile  power  is 
immediately  placed  under  the  influence  of  the  will.  They  are  more 
particularly  concerned  in  the  execution  of  the  functions  of  relation, 
which  causes  them  to  be  named  the  external  muscles,  or  muscles  of  animal 
life.  These  muscles  are  nearly  all  attached  to  the  skeleton,  and  represent 
the  active  agents  in  the  movements  of  the  osseous  framework ;  they  will, 
therefore,  be  the  only  ones  referred  to  in  this  place,  in  studying  the 
locomotory  apparatus. 

But  before  entering  upon  the  particular  description  of  each  muscle,  we 
will  allude  to  the  general  considerations  relative  to  their  history. 


CHAPTER  I. 

GENERAL   CONSIDERATIONS   ON   THE   STRIATED  MUSCLES. 
THE    STRIATED   MUSCLES    IN    GENERAL. 

In  this  first  paragraph,  we  will  survey  in  a  general  manner  the  volume, 
situation,  form,  direction,  attachments,  relations,  and  names  of  the  muscles 
belonging  to  the  locomotory  apparatus. 

A.  Volume. — Nothing  is  more  variable  than  the  respective  volume  of 
the  external  muscles.  What  a  difi"erence  there  is,  for  example,  between  the 
small  scapiilo-humeral  muscle  and  the  long  vastus  or  ilio-spinalis  (longissimus 
dorsi) !  and  what  a  number  of  intermediate  sizes  between  these  three  points 
of  comparison !  There  are  consequently  very  great,  great,  medium,  small, 
and  very  small  muscles. 

The  weight  of  the  total  mass  of  these  organs  varies  according  to  the 
species,  age,  sex,  and  state  of  health ;  but  taking  a  general  average,  it  will 
be  found  that  it  represents  nearly  one-half  the  entire  weight  of  the  body. 

B.  Situation. — There  is  no  need  to  insist  upon  the  fact,  that  a  knowledge 
of  the  situation  of  the  muscles  is  one  of  the  fii'st  objects  to  be  acquired  with 
regard  to  their  disposition. 

They  may,  like  the  bones,  be  described  in  two  ways. 

1.  In  relation  to  the  median  plane  of  the  body,  from  whence  their  division 
into  ]>airs  and  single  muscles.  The  last,  very  few  in  number,  are  far  from 
exhibiting  the  symmetry  which  exists  in  the  bones  of  this  division,  as  may 
be  seen  in  the  diaphragm. 

2.  In  relation  to  the  other  organs,  such  as  the  bones  and  surrounding 
muscles. 

C.  Form. — With  regard  to  their  absolute  form,  the  muscles,  again,  like 
the  bones,  are  classed  as  long,  wide,  and  short. 

Long  muscles. — These  muscles  are  more  particularly  met  with  in  the 
limbs.  Provided  with  a  principal  axis,  to  which  we  may  ascribe  the  eficct 
of  their  contraction,  they  present  a  middle  portion — usually  protuberant,  and 


GENERAL  CONSIDERATIONS  ON  THE  STRIPED  MUSCLES.         175 

two  extremities  of  unequal  thickness ;  the  most  voluminous,  always  turned 
upwards,  is  metaphorically  designated  the  head,  the  other  the  tail.  They 
are  most  frequently  fusiform,  sometimes  conical,  but  rarely  cylindrical, 
prismatic  or  flattened  into  thin  bands. 

"  There  is  a  particular  kind  of  long  muscles  which  have  no  analogy  with 
those  of  the  extremities,  except  in  their  external  appearance.  They  are 
those  which  lie  below,  but  more  particularly  above,  the  spine.  Although 
at  the  first  glance  they  appear  simple,  yet  they  present  as  many  distinct 
fasciculi  as  there  are  vertebrte.  The  transverse  spinous  [spinalis  dorsi),  etc., 
is  no  doubt  an  elongated  fasciculus  like  the  sartorious.  etc.,  but  the  structure 
of  this  fasciculus  has  nothing  in  common  with  that  of  the  latter  muscle  : 
it  is  a  series  of  small  fasciculi  which  have  each  their  distinct  origin  and 
termination,  and  only  appear  as  a  single  muscle  because  they  are  in  juxta- 
position."— Bichat,  '  Anatomie  Generale.' 

Wide  muscles. — Wide  muscles  are  those  which  have  two  princii^al 
axes,  and  are  stretched  beneath  the  skin,  or  around  the  great  cavities  of  the 
trunk,  which  they  concur  in  inclosing  and  separating  from  one  another. 
They  are  elliptical,  quadrilateral,  triangular,  trapezoid,  etc. 

Short  muscles. — These  are  found  chiefly  around  the  short  bones,  or  at 
the  periphery  of  the  articulations  which  are  deeply  buried  under  enormous 
muscular  masses.  Although  their  name  indicates  that  their  three  axes  offer 
nearly  the  same  dimensions,  yet  there  is  most  frequently  one,  and  even  two, 
which  predominate.  They  may  therefore  be  assimilated,  in  this  respect,  to 
the  long  or  wide  muscles. 

D.  Direction. — Cruveilhier  has  justly  remarked,  that  the  direction 
of  a  muscle  is  one  of  the  most  important  features  in  its  history ;  for 
it  allows  the  determination  of  the  angle  of  incidence  of  the  muscle  on 
its  arm  of  the  lever,  the  power  of  its  action,  and  the  nature  of  its  uses. 

With  regard  to  the  direction  of  the  muscles,  we  may  observe :  1,  The 
form  of  their  principal  axis;  2,  The  relation  of  this  axis  to  the  plumb- 
line  ;  3,  Its  comparison  with  the  axis  of  the  bony  levers  which  the  muscles 
surround  or  move. 

a.  A  muscle  is  termed  rectilinear  when  its  principal  axis  is  straight ; 
it  is  curvilinear,  or  circular,  if  this  axis  describes  a  cui-ve  more  or  less 
marked ;  it  becomes  inflected  when  it  proceeds  in  a  certain  direction,  and 
afterwards  turns  on  a  bony  or  cartilaginous  pulley  in  another  direction  : 
that  is  to  say,  when  its  principal  axis  is  broken  into  several  lines.  If  the 
muscle  offers  two  axes,  it  will  be  flat  or  concave,  these  being  one  or  the 
other,  or  straight  or  curvilinear. 

h.  With  regard  to  the  direction  of  the  muscles  to  that  of  the  plumb-line, 
it  is  either  vertical,  horizontal,  or  oblique,  expressions  which  carry  their  own 
definition  and  require  no  explanation. 

c.  If  the  direction  of  the  muscles  be  compared  with  that  of  the  bony 
levers  they  surround  and  move,  it  will  be  found  that  they  are  either  parallel 
to  these  levers,  or  form  with  them  angles  more  or  less  acute.  The  proper 
direction  of  the  bones  being  known,  it  is  sufficient  to  indicate  that  of  the 
muscles  to  clearly  establish  this  comparison.  For  instance,  in  saying  that 
the  majority  of  the  muscles  of  the  shoulder  are  oblique  from  above  to  below, 
and  from  before  to  behind,  it  is  understood  that  these  muscles  are  parallel 
to  the  scapula,  and  that  their  incidence  on  the  humerus  takes  place  at  a 
right  angle. 

E.  Attachments  or  Insertions. — This  is  undoubtedly  the  most  essential 
part  of  the  study  of  the  muscles ;  for  with  the  knowledge  of  their  insertions 


176  TEE  MUSCLES. 

we  may  determine  their  extent  and  direction,  and  even  their  relations  and 
uses. 

By  the  term  attachment,  fixed  insertion,  or  origin,  is  meant  the  point  of 
the  muscle  which  most  usually  remains  lixed  while  that  organ  contracts ; 
the  attachment,  movable  insertion,  or  termination  is  the  name  given  to  that 
portion  which  corresponds  to  the  lever  displaced  hy  the  muscular  contraction. 
Muscles  are  frequently  met  with  whose  two  insertions  are  alternately  fixed 
or  movable ;  and  in  such  cases  care  is  taken  not  to  give  these  insertions  one 
or  other  of  the  designations. 

The  fixed  insertion  is  often  confounded  with  that  of  other  muscles ;  the 
movable  insertion  is  generally  free  and  independent. 

The  muscles  are  sometimes  directly  attached  to  the  bones  by  the  ex- 
tremities of  their  fleshy  fibres ;  but  most  frequently  they  are  fixed  to  these 
inert  levers  through  the  medium  of  a  tendon  or  an  aponeurosis,  whose 
volume  is  less  considerable  than  that  of  the  fibres.  Without  this  latter 
disposition,  the  surface  of  the  skeleton  would  not  have  been  suflicieutly 
extensive  to  give  insertion  to  all  the  external  muscles. 

The  attachment  of  the  muscles  to  the  bony  levers  is  effected  by  a 
kind  of  fusion  between  the  fleshy  or  tendinous  fibres,  and  the  periosteum. 

F.  Relations. — The  indication  of  the  relations  of  the  muscles  completes 
the  idea  of  their  situation,  and  is  of  great  importance  in  a  surgical  point 
of  view.  They  should,  therefore,  be  studied  with  all  the  precision 
possible. 

The  muscles  entertain  relations  either  with  the  skin,  the  bones,  other 
muscles,  or  with  vessels  and  nerves. 

a.  It  is  only,  properly  speaking,  the  subcutaneous  muscles,  such  as  the 
panniculus  caruosus  and  the  muscles  of  the  face,  which  are  really  in  im- 
mediate contact  with  the  skin.  The  others  are  separated  from  it  by  the 
aponeurotic  fascia  which  will  be  described  as  the  appendices  of  the  muscular 
system. 

h.  The  superficial  muscles  are  only  related  to  the  bones  by  their  ex- 
tremities. Those  which  are  deeply  situated  are  immediately  applied  by 
their  bodies  against  the  bones  of  the  skeleton. 

c.  The  muscles  are  related  to  each  other  in  a  more  or  less  intimate 
manner.  Sometimes  they  adhere  closely  to  one  another ;  and  at  other  times 
they  are  separated  by  interstices  filled  with  fat  or  cellular  tissue,  and 
generally  traversed  by  vessels  and  nerves. 

d.  The  connections  of  the  muscles  with  the  latter  organs  sometimes 
assume  a  remarkable  character ;  this  is  when  one  of  them  accompanies, 
like  a  satellite,  the  vascular  and  nervous  trunks  concealed  beneath  its  deep 
face.  There  is  in  this  circumstance  an  important  fact  with  regard  to 
surgical  anatomy. 

G.  Nomenclature.— Before  the  time  of  Sylvius,  the  muscles  had  not 
received  particidar  names.  Since  the  days  of  Galen  they  had  been  dis- 
tinguished by  the  numerical  epithets  oi  first,  second,  third,  aid.,  to  iM^iciLiQ 
their  place  and  their  order  of  superposition  in  the  regions  to  which  tliey 
belonged.  It  is  in  this  fashion  that  they  are  designated  in  the  Italian  work 
on  the  Anatomy  of  the  Horse  by  Ruini. 

Sylvius  was  the  first  to  give  the  muscles  real  names ;  and  his  example 
being  followed  by  succeeding  anthropotomists,  the  nomenclature  of  these 
organs  was  soon  completed.  But  no  general  view,  no  methodic  spirit  guided 
Sylvius  and  his  successors  ;  it  was  sometimes  their  form,  and  sometimes  their 
direction,  position,  uses,  etc.    to   which  the  muscles  owed  their  names. 


GENERAL  CONSIDERATIONS  ON  THE  STRIFE D  MUSCLES.  ]77 

Bourgelat  applied  this  nomenclature  to  the  horse,  but  modified  it  in  many 
points. 

Chaussier,  struck  by  the  imperfections  of  the  nomenclature  introduced 
into  scien(^e  by  Sylvius,  sought  to  substitute  for  it  another  much  more  philo- 
sophical. This  anatomist  gave  to  each  muscle  a  name  formed  by  two  words 
indicating  the  insertions  of  the  organ.  Girard  imported  this  ingenious 
idea  into  veterinary  anatomy. 

Nevertheless,  notwithstanding  its  advantages,  tbis  new  nomenclature 
did  not  supersede  the  old  one ;  because  it  ceased  to  be  correct  when  applied 
to  comparative  anatomy,  the  same  muscles  not  having  the  same  insertions 
in  all  the  species.^ 

'  It  is  not,  however,  that  the  ancient  nomenclature  has  more  advantages  in  this 
respect  thnn  the  new.  Wliat  can  be  more  improper,  for  example,  than  the  names  of 
deltoid,  splenius,  solens,  digastricus,  etc.  ?  Do  tiie  muscles  which  receive  these  desig- 
nations, considered  in  mammals  only,  offer  in  all  species  the  foim  or  the  structure  which 
justifies  the  employment  of  these  names  in  the  human  species?  Are  the  distinctive 
epithets  of  great,  medium,  little,  etc.,  given  to  many  of  them,  reasonably  applicable  in 
every  case  ?  May  not  the  same  objection  be  urged  against  the  majority  of  the  names 
derived  from  their  uses,  comiilications.  etc.  ? 

No  system  of  m\ological  nomenclature  is  really  philosophical,  and  we  are  of  those 
■who  believe  it  to  be  indispensably  necessary  to  create  one ;  indeed,  we  are  inclined  to  think 
that  it  would  be  simple  and  easy  to  attain  this  resnlt  in  starting  from  a  basis  whose 
fixity  and  invariability  should  be  well  defined.  And  this  basis  is,  in  our  opinion,  already 
discovered ;  it  is  the  principle  of  coinections  founded  by  E.  Geoffroy  b'aint-Hilaire  in  his 
immortal '  Philosophie  Anatomique,'  a  principle  to  which  modern  science  certainly  owes  its 
finest  conquests. 

This  is  a  subject  which  it  is  our  intention  to  treat  in  a  special  work  ;  but  we  may, 
nevertht'less,  indicate  here  the  manner  in  which  it  presents  itself  to  us. 

We  are  desirous  that  the  viyolo(jicctl  nomenclature  should  rest  entirely,  in  the  first  place, 
on  the  relations  of  the  muscles  icitli  the  pieces  of  the  skeleton,  or  loith  other  organs  equally 
fixed  and  very  important ;  in  the  second  place,  on  the  reciprocal  connections  of  the  muscles. 

Such  is  our  plan ;  and  it  is  not  precisely  new.  for  the  old  anatomists  were  often 
inspired  with  it,  though  unwittingly,  as  the  jirinciple  on  which  it  is  founded  was  to 
them  entirely  unknown;  this  circumstance,  however,  immi  diately  leads  us  to  an  appre- 
ciation of  its  value.  For  instance,  what  could  be  hajipier  tl  an  the  name  of  intercostals 
given  to  the  muscles  situated  between  the  ribs,  and  their  distinction  into  external  and 
internal  V  Here  we  have  names  wliich  indicate  the  relations  of  the  muscles  they  desig- 
nate ivith  the  portions  of  the  skeleton  and  the  reciprocal  connections  of  these  muscles.  It 
can  also  be  applied  in  an  equally  rigorous  manner  to  every  species.  We  may  also  cite 
the  snpiacostals,  the  intertransverse,  the  transverse  spinous,  the  subscapularis,  the 
supraspinous,  the  subspinous,  etc.,  as  they  are  found  in  a  greater  or  less  marked  degree 
in  identical  conditions. 

Other  muscles  have  received  names  derived  in  part  from  their  situation,  and  in  part 
from  their  volume.  These  names  are  far  from  being  as  convenient  as  the  iirst ;  as  may 
be  judged  from  the  following  examples  : 

In  the  majority  of  vertebrate  animals,  there  are  three  important  muscles  sitnated 
above  and  behind  the  pelvis,  and  forming  the  basis  of  the  buttock ;  they  have  beeu 
designated  gluteals,  and  this  name  is  convenient,  because  it  designates  their  situation. 
But  to  distinguish  them  from  each  other,  regard  has  been  had  to  their  volume  ;  so  that 
there  is  a  great,  a  medium,  and  a  small  gluteus.  This  is  an  error,  however,  for  the  volume 
of  the  muscles  is  subject  to  the  greatest  variations,  and  a  voluiuinous  muscle  in  one 
species  may  be  a  very  small  one  in  another,  and  vice  versa.  The  muscle  analogous  to  the 
gluteus  maximus  in  Man  has  been  described  by  Bourgelat  as  the  minimus,  and  by  Lafosse 
and  Rigot  as  the  medius.  With  regard  to  the  gluteus  medius  of  Man,  its  representative 
in  the  lower  animals  has  been  designated  as  the  maximus  by  the  majority  of  veterinary 
anatomists.  What  confusion !  And  how  easy  it  was  to  evade  it  by  distinguishing  these 
muscles,  not  by  their  volume,  but  by  their  reciprocal  connections,  which  are  the  same  in 
every  species !  Is  it  not,  indeed,  more  natural  to  substitute  the  names  of  superficia], 
middle,  and  deep  gluteals,  for  tho? e  of  great,  etc  ? 

The  same  remark  is  applicable  to  the  muscles  which,  in  Man,  cover  the  anterior 
aspect  of  the  chest.  Designated  in  common,  and  justly  so,  as  pectorals,  these  muscles 
are  wrongly   distinguished  into  great  and  little;    for  the  last,  which  is  already  an 


178 


THE  MUSCLES. 


In  this  work  we  will  follow  the  nomenclature  of  Bourgelat,  which  will 
however,  be  submitted  to  some  change.  But  as  the  names  given  by  Girard 
are,  in  our  opinion,  of  some  assistance  to  students,  care  will  be  taken  to 
include  them  in  the  synonymy. 

(It  only  remains  for  me  to  add  that  Chauveau's  nomenclature  will 
be  follo\ved  as  closely  as  possible.  It  possesses  advantages  which  are 
greatly  superior  to  that  adopted  by  Percivall ;  and  as,  in  my  opinion,  the 
names  and  terms  imjjorted  into  science  should  be  as  nearly  alike  in  all 
languages  as  may  be  compatible  with  circumstances,  in  order  to  facilitate 
study,  comparison,  and  reference,  I  the  more  readily  venture  to  take  this 
step.  Percivall's  nomenclature  will,  however,  be  added  in  brackets  to  the 
synonyms,  as  well  as  that  of  Leyh  and  Gurlt  when  occasion  appears  to 
demand  it.) 

STEUCTURE    OF   THE    STRIPED    MUSCLES. 

There  enter  into  the  structure  of  muscles :  1,  Muscular  tissue,  properly 
so-called ;  2,  Conjunctival  tissue  in  the  form  of  delicate 
lamellfe,  aponeuroses,  or  tendons ;  3,  Vessels  and  nerves. 
A.  Muscular  Tissue. — This  tissue  is  composed  of 
prismatic  fasciculi,  which  it  is  jiossible  to  divide  and 
subdivide  into  several  smaller  and  smaller  fasciculi, 
until  the  muscular  fibre  ov  primitive  fasciculus  is  reached. 
The  muscular  fibre  is  a  kind  of  irregular  polyhedron, 
with  rounded  angles,  and  extremities  terminating  in  a 
blunt  point.  It  is  sometimes  straight,  sometimes 
wrinkled,  but  always  striped  either  in  a  longitudinal  or 
transversal  direction,  or  both  at  once. 

This  fibre  is  formed  by  an  envelope  and  contents. 
The  envelope  is  a  very  delicate,  structureless  mem- 
brane of  an  elastic   nature,  named   the  sarcolemma  or 
hio-hlymao-nified,  its   myolemma.     Nuclei  in  greater  or   less  number  can  be 
myolemma  being  so   seen  on  its  inner  face. 

The  contents  are  resolved  into  contractile  fihrillce  and 
an  interstitial  substance. 

The  contractile  fibrilla  constitutes  the  primary  ele- 
ment of  striped  muscle.  It  is  a  minute  column  whose 
surface,  according  to  Eouget,  exhibits  the  alternate  prominences  and 
depressions  of  the  turns  of  a  more  or  less  fine  screw ;  and  which,  according 

to  Bowman,  is  formed  by  a  mass  of 
small  discs,  named  by  him  the  sarcous 
elements. 

The  interstitial  substance,  granular 
and  nucleated,  unites  the  fibrillaj  in 
the  interior  of  the  sarcolemma  and, 
in  addition,  according  to  Bowman's 

MUSCULAR    FIBRE    BROKEN     ACROSS      SHOWING     J^  t^^^gj         thc     disCS     CUteriug     iutO 

THE     UNTORN      SARCOLEMMA      CONNECTING     •"Jl'"''  5  O 

THE  FRAGMENTS.  "iG  compositiou  01  cach  nbrilJa. 

The   aggregation  of  the  fibrillas 
produces  the  longitudinal  striation :  the  transverse  striation  is  the  result 


B,     ULTIMATE      FIIJRIL 

OF  MUSCLE,  accord- 
ing to  Bowman. 
Muscular  fibre  more 


c, 


thin  and  transparent 
as  to  allow  the  ulti- 
mate fibrilL-c  to  be 
seen. 


96. 


enormous  muscle  in  the  smaller  Ruminants,  is  represented  in  Solipeds  by  two  consider- 
able mu.SL-les,  mucb  more  voluminous  than  the  muscle  analogous  to  the  great  pectoral. 
It  is  only  necessary,  in  this  case,  to  change  their  names  into  superficial  and  deep 
pectorals. 


GENERAL  CONSIDERATIONS  ON  THE  STRIPED  MUSCLES. 


179 


Fi?.  97. 


either  of  the  helicoid  disposition  of  the  fibrillse,  or  of  the  fusion  of  the 
sarcous  elements  which  compose  the  hitter,  according  to  the  admitted  opinion 
as  to  the  structure  of  the  contractile  element. 

The  muscular  fibres  are  united  parallel  to  each  other  to  form  secondary- 
fasciculi,  which  are  surrounded  by  a  con- 
junctival sheath — the  perimysium.  The 
secondary  fasciculi  are  lai(i  together  to 
constitute  more  voluminous  fasciculi 
which,  in  their  turn,  form  the  entire 
muscle.  The  conjunctival  sheath  enve- 
loping the  muscle  is  named  the  external 
perimysium. 

B.  Tendons  and  Aponeuroses.— The 
tendons  are  white,  nacreous,  round,  or 
flattened  cords  fixed  to  the  extremities  of 
the  long  muscles.  They  are  composed 
of  fasciculi  of  condensed  conjunctival 
tissue,  afiectiug  a  parallel  direction,  and 
united  to  one  another  by  connective 
sheaths. 

The  aponeuroses  belong  almost  ex- 
clusively to  the  wide  muscles  ;  they  are 
formed  of  several  planes  of  parallel  fibres 
which  are  not  intercrossed  in  their 
middle  part ;  at  their  superficies,  how- 
ever, the  fibrous  fasciculi  are  matted  toge- 
ther in  a  more  or  less  inextricable  manner. 

It  is  very  interesting  to  study  the 
mode  of  union  of  the  muscular  fibres 
with  the  tissue  of  the  aponeuroses  and 
tendons,  as  well  as  the  reciprocal  rela- 
tions of  these  two  parts. 

The  muscular  fibre  may  be  found  passing  in  the  same  direction  as  the 
tendon,  or  it  may  fall  upon  the  latter  obliquely.  In  both  cases  there  is  no 
insensible  transition  between  the  muscular  fibre  and  the  fasciculus  of  the 
fibrous  tissue  ;  on  the  contrary,  the  contractile  fibre  terminates  by  a  rounded 
extremity,  which  is  buried  in  a  corresponding  depression  in  the  tendon  or 
aponeurosis.  The  union  of  the  muscular  with  the  fibrous  tissue  is  very 
intimate  ;  when  the  muscles  are  submitted  to  a  degree  of  traction  sufficient  to 
cause  a  rupture,  this  never  happens  at  the  point  of  union. 

The  tendons  commence  sometimes  by  a  hollow  cone,  which  receives  on 
its  internal  face  the  insertions  of  its  muscular  fibres ;  and  sometimes  by  a 
thin  point,  often  divided,  wdiich  is  plunged  into  the  substance  of  the  muscle. 
It  is  worthy  of  remark  that  a  muscle  provided  with  two  tendons  shows  the 
first-named  arrangement  at  one  of  its  extremities,  and  the  other  at  its  oppo- 
site extremity ;  so  that  all  the  fibres  which  comjiose  the  muscle  offer  nearly 
the  same  length,  those  which  leave  the  summit  of  the  internal  tendon  being 
fixed  to  the  bottom  of  the  hollow  cone  formed  by  the  second  tendon,  and  so 
on  reciprocally. 

The  muscular  fibres  which  are  continued  by  the  fibrous  fasciculi  may  be 
divergent  or  parallel.  In  the  first  case — the  diaphragm,  for  example — the 
connective  fibres  run  in  the  same  direction  as  the  muscular  fil>res.  In  the 
second  case,  several  arrangements  may  be  observed : 


TRANSVERSE  SECTION  OF  FROZEN  MUSCLE, 
MAGNIFIED    400    DIAMETERS. 

N,  Nerve ;  M,  Muscular  fibre,  surrounded 
by  portions  of  six  others. — a,  Nucleus 
of  the  nerve  sheath  ;  b,  Nucleus  of  the 
sarcolemma ;  c,  Section  of  nucleus  of 
terminal  plate  of  nerve  ;  d,  Transverse 
section  of  terminal  plate;  surrounded 
by  granular  material ;  e,  Transverse 
section  of  muscle  nuclei ;  /,  Fine  fat 
drops.  The  angular  dark  particles  are 
sections  of  sarcous  elements  :  the  clear 
intervening  spaces  represent  the  fluid 
isotropal  part  of  the  muscle  substance. 


180 


THE  MUSCLES. 


Fi?.  98. 


1.  Tendons  may  pass  in  the  same  direction  as  the  muscular  fibres.  This 
is  the  most  simple  manner.  But  the  muscle  may  be  divided  into  two  bodies 
or  bellies  by  a  middle  tendon ;  it  is  then  called  a  digastric  muscle. 

2.  Muscular  fasciculi,  passing  altogether  from  the  same  side  to  become 
anited  into  a  tendinous  cord,  constitute  a  semi-penniform  muscle. 

3.  Muscular  fasciculi  may  be  implanted  to  right  and  left  of  the  tendon, 
and  form  a  pennated  or  penniform  muscle. 

"  This  arrangement  of  fibres  demonstrates  that  the  length  of  the  muscle, 
the  length  of  its  belly,  and  the  length  of  its  muscular  fibres,  should  be  care- 
fully distinguished.  The  first  term  is  applicable  to  the  whole  of  the  muscle, 
the  tendon  included ;  the  second,  to  the  fleshy  body  of  the  muscle,  with  the 
exception  of  the  tendon ;  the  third,  to  the  muscidar  fasciculi  constituting 
this  fleshy  body :  the  latter  idea  is  the  most  important,  for  it  alone  indicates 

the  amount  of  conti-action  a  muscle  is  sus- 
ceptible of,  and  consequently  the  possible  ex- 
tent of  movement  it  is  capable  of  effecting." — 
Beaunis  and  Bouchard. 

C.  Vessels  and  Nerves. — -The  muscular 
tissue  receives  much  blood ;  the  fibrous  tissue 
very  little.  The  arteries  are  large,  numerous, 
and  each  is  acccompanied  by  two  veins.  The 
capillary  vessels  anastomose  in  such  a  manner 
as  to  form  rectangular  meshes,  whose  greatest 
diameter  is  directed  towards  the  length  of  the 
muscle. 

The  lymphatic  vessels  of  the   muscles    are 
few ;  they  sometimes  j^enetrate  their  interior  in 
following  the  capillaries ;  at  other  times  they  remain  on  the  surface,  in  the 

external  perimysium.  The  exist- 
ence of  lymjihatics  has  not  yet  been 
demonstrated  in  tendons,  aponeu- 
roses, or  synovial  membranes. 

The  nerves  emanate  from  the 
cerebro-spinal  centre.  At  their 
terminal  extremity  they  offer  a 
small  enlargement,  called  by 
Rouget  the  terminal  motor  plate, 
and  by  Doyere  and  Kiihne  the  ner- 
vous  colline  (hillock).  It  is  ad- 
mitted that  the  motor  tube  traverses 
the  sarcolemma,  losing  its  enve- 
lope ;  and  tliat  the  substance  of  the 
cylinder  is  spread  over  the  surface 
of  the  muscular  fibrillfe  to  form  the 


distribution  op  capillaries 
In  muscle. 


Fi?.  99. 


PORTION  OF  AN  ELEMENTARY  MUSCULAR  FIBRE, 
WITH  FOUR  DARK-BORDERED  FIBRES  (a)  CROSS- 
ING ITS  SURFACE ;  after  Beale. 

b,  Capillary  blood-vessel,  with  fine  nerve-fibres ;  motor  plate  or  nervous  colline, 
a  few  only  of  the  transverse  markings  of  the 
muscle  are  represented ;  c,  Two  of  the  dark- 
bordered  nerve-fibres  passing  over  the  ele- 
mentary fibre  to  be  distributed  to  adjacent 
fibres.  This  arrangement,  in  which  a  dark- 
bordered  nerve-fibre,  distributed  to  muscle, 
divides  into  branches,  one  of  which  passes  to 
a  vessel,  while  the  other  ramifies  upon  a 
muscle,  is  frequent.   Magnified  700  diameters. 


PHTSICO-CHEMICAL   PROPERTIES    OP 
STRIPED    MUSCLES. 

Muscles  arc  soft  organs,  re- 
markable for  their  more  or  loss 
deep-red  colour,  which  varies  with 
the  species,  and  even  in  these  with 
the  age  and  health  of  the  animals. 


GENERAL  CONSIDERATIONS  ON  TEE  STRIFED  MUSCLES. 


181 


By  desiccation,  muscles  become  hard  and  bro'wn  ;  by  repeated  wasliing 
tliey  assume  a  straw-yellow  tint. 

Muscles  are  extensible  and  elastic ;  they  are  also  tenacious,  and  their 
tenacity  is  more  marked  during  life  than  after  death. 

It  has  been  remarked  that  the  juice  impregnating  the  muscular  tissue  is 
distinguished  from  the  serum  of  the  blood  by  an  acid  reaction.  (The  iluid  or 
"  muscle  plasma "  obtained  by  pressing  flesh,  is  either  neutral  or  slightly 
alkaline.  It  soon  coagulates  and  separates  into  two  portions — a  semi-solid 
portion,  "  myosin,"  and  the  fluid  serum  that  at  ordinary  temi^eratures  quickly 
acquires  an  acid  reaction.)  It  holds  in  solution  a  variable  quantity  of 
albumen,  casein,  fat,  a  little  creatine,  creatinine,  and  a  somewhat  large 
proportion  of  lactic  acid.  The  solid  substance  of  the  muscle  may  be  partly 
transformed  into  gelatine  by  boiling  in  water ;  but  its  largest  portion  is  a 
nitrogenous  substance,  soluble  in  dilute  hydrochloric  acid,  called  "'  syntonine," 
or  muscular  fibrine ;  it  differs  but  little  from  the  fibrine  of  the  blood. 

PHYSIOLOGICAL   PROPEETIES   OF    THE    STRIPED   MUSCLES. 

In  this  paragraph  will  only  be  discussed  the  development  of  the  muscles, 
muscular  contractility,  and  the  part  the  muscles  assume  in  locomotion. 

A,  Development  of  the  Muscles. — A  muscle  is  derived  from  a  mass  of 
embryonic  cells.  Each  cell  becomes  considerably  elongated,  and  its  nucleus 
becomes  multiple,  to  constitute  a  muscular  fibre.  The  membrane  of  the  cell, 
enormously  developed,  forms  the  sarcolemma,  while  the  contents  of  the  cell, 
becoming  more  dense,  divide  longitudinally  and  give  rise  to  the  contractile 
fibrillte.  Lastly,  when  the  muscles  are  formed,  they  grow  by  the  augmenta- 
tion in  length  and  thickness  of  the  primary  fasciculi  or  muscular  fibres. 

B.  Muscular  Contractibility. — Muscles  possess  the  property  of  con- 
tracting under  the  influence  of  a  natural  or  artificial  stimulus.  Muscular 
contraction  is  the  phenomenon  resulting  from  the  operation  of  this  property. 
Muscles  in  a  state  of  contraction  are  the  seat  of  physical  and  chemical 
phenomena  ;  they  change  their  form  and  consistency,  and  become  the  theatre 
of  a  relatively  abundant  production  of  carbonic  acid,  creatinine,  and  inosinic 
acid.  During  contraction,  it  has  been  remarked  that  the  muscular  fibres 
contract  by  increasing  in  volume,  like  an  india-rubber  tube  left  to  itself  after 
being  extended  :  the  zig-zag  doubling  mentioned  by  Prevost  and  Dxmias  has 
not  been  observed. 

But  these  physical  and  chemical  modifications,  important  as  they  are  in 

Fig.  100. 


MUSCCXAR  FIBRE  IN  A  STATE  OF  CONTRACTION  IN  THE  CENTRE;  THE  STRI.IT 
APPROXIMATED ;  THE  BREADTH  OF  THE  FIBRE  INCREASED  ;  AND  THE  MYO- 
LEiniA   RAISED   IN   VESICLES  ON   ITS   SURFACE. 

a  physiological  point  of  view,  cannot  longer  be  dwelt  upon  here.    It  is  parti- 
cularly important  to  speak  of  muscular  contraction. 

A  muscle  that  contracts  becomes  shortened  ;  its  two  extremities  approach 
each  other  if  they  are  free  ;  or  one  draws  near  the  other  if  the  latter  is  fixed 
15 


182  THE  MUSCLES. 

to  an  immovable  point.  If  tlie  extremities  of  a  muscle  are  attached  to  two 
movable  levers,  its  contraction  will  bring  about  the  displacement  of  one  or 
other  of  these  ;  from  this  a  movement  is  produced. 

The  degree  of  shortening  of  a  muscle  varies,  according  to  its  being 
entirely  free,  or  having  a  resistance  to  overcome.  The  mean  limit  of  this 
shortening  is  about  one-fourth  the  length  of  the  muscular  fibres ;  from  tliis  it 
will  be  understood  that  the  movement  produced  by  the  contraction  will  be 
in  proportion  to  the  length  of  the  fibres ;  though  in  this  appreciation  it  will 
be  necessary  to  keep  in  mind  the  density  and  energy  of  the  fibre,  as  well  as 
the  intensity  of  the  contractile  stimulant. 

As  each  fibre  represents  a  force  independent  in  its  action,  it  results  that 
we  may  judge  of  the  power  of  a  muscle  by  the  number  of  its  fibres,  or  its 
volume. 

Muscles  are  often  aided  in  their  action  by  mechanical  conditions :  such  as 
the  disposition  of  the  levers  on  which  they  act,  the  direction  of  the  muscular 
fibres  in  connection  with  these  levers,  and,  lastly,  by  the  presence  of  lamellae 
or  elastic  cords. 

C.  Uses  of  Muscles. — There  are  flexor,  extensor,  abductor,  adductor, 
rotator,  and  other  muscles,  for  all  the  movements  of  which  the  articulations 
are  the  centre. 

To  determine  the  functions  or  uses  of  the  muscle,  it  is  sufficient  to  know 
their  insertions,  and  the  mode  in  which  the  bones  furnishing  these  insertions 
articulate  with  each  other. 

The  result  of  muscular  contraction,  being  influenced  by  the  form  of  their 
principal  axis,  and  the  length  and  direction  of  their  levers,  it  is  necessary  to 
briefly  examine  these  two  points  ; 

1.  The  immediate  effect  of  the  contraction  of  rectilinear  muscles  is  the  ap- 
proximation of  the  bones  to  which  they  are  attached.  This  approximation 
is  usually  brought  about  by  the  displacement  of  a  single  ray :  that  which 
receives  the  movable  insertion  of  the  muscle.  Sometimes,  however,  the  two 
rays  move  simultaneously,  or  they  are  alternately  fixed  and  movable. 

The  first  result  produced  by  a  curvilinear  muscle  is  the  straightening  of 
its  component  fibres  ;  after  which  it  may  act  on  the  bony  levers  as  do  the 
rectilinear  muscles,  if  its  contractile  power  be  not  entirely  expended.  When 
a  muscle  is  quite  circular,  its  only  action  is  to  contract  the  opening  it  circum- 
scribes. 

With  regard  to  the  inflected  muscles,  their  action  can  only  be  estimated 
from  their  point  of  inflexion  ;  they  operate  as  if  this  point  represented  their 
origin  or  fixed  insertion. 

2.  The  muscular  powers  are  submitted  to  the  statical  and  dynamical  laws 
which  govern  the  theory  of  levers  ,  for  the  bony  rays  are  only  levers  moved 
by  the  muscles. 

In  the  locomotory  apparatus  we  find  the  three  kinds  of  lever  recognised 
by  physicists.  Thus  the  head,  extended  by  the  great  complexus  muscle, 
represents  an  interflxed,  or  lever  of  the  first  class  ;  the  foot,  extended  by  the 
gastrocnemii  muscles,  offers  an  example  of  the  interresisting,  or  second  kind, 
when  this  member  remains  fixed  on  the  ground  ;  lastly,  the  lower  jaw  raised 
towards  the  upper  by  the  masseter  muscle,  forms  an  interpuissant  or  third 
kind. 

It  is  worthy  of  remark  that  the  arm  of  resistance  in  the  bony  levers  is 
always  extremely  long ;  a  circumstance  which  favours  speed  and  the  extent  of 
movement  at  the  expense  of  power. 

On  the  other  hand,  muscles  are  rarely  perpendicular  to  the  arm  of  their 


GEXEBAL  COXSIDEBATIOXS  ON  TEE  STEEPED  MUSCLES.         183 

levers,  at  least  at  the  commencement  of  their  action  ;  another  ciroumstance 
which  again  diminishes  their  energy. 

APPENDAGES    OF   THE   MTSCLES. 

These  are :  1,  The  enveloping  or  contentive  aponeuroses ;  2,  The 
serous  or  mucous  bursje ;  3,  The  tendinous  and  synovial  sheaths. 

A.  CoxTE>-TivE  Aponeuroses. — These  are  layers  of  white  fibrous  tissue, 
which  envelop,  in  common,  all  the  muscles  6f  one  or  several  adjoining 
regions,  principally  those  of  the  inferior  rays  of  the  limbs,  where  they  con- 
stitute a  kind  of  hollow  cylinder. 

These  aponeuroses  are  formed  by  very  resisting  interwoven  fibres,  which 
are  attached  to  the  bones  at  nvmierous  points.  At  their  periphery  they 
receive  the  insertion  of  one  or  several  muscles,  which  keep  them  more  or  less 
tense.  Their  external  face  responds  to  a  thin  fibro-cellular  layer  that 
separates  them  from  the  skin.  The  internal  face  sends  lamellar  prolong- 
ations between  the  muscles,  which  are  destined  to  isolate  these  organs  in 
special  sheaths. 

The  aponeuroses  maintain  the  muscles  in  their  position,  and  sustain 
them  during  their  contraction. 

B.  Seeocs  Buks^. — The  serous  or  mucous  bursas  are  small  cavities,  filled 
with  a  serous  fluid,  which  are  met  with  at  those  points  where  the  muscles 
glide  over  resisting  surfaces.  They  are  generally  orbicular  or  rounded,  and 
their  interior  is  often  divided  by  fibrous  bands. 

Their  walls  are  formed  by  slightly  condensed  conjunctival  tissue,  and 
may  be  lined  by  a  pavement  epithelium ;  in  which  case  it  is  believed  that 
the  serous  bursa  is  produced  by  the  simple  dilatation  of  one  of  the  con- 
junctival meshes. 

C.  TENDixors  Sheaths  axd  Synovial  Membbaxes. — Tendinous  sheaths 
is  the  name  given  to  the  half-bony,  half-fibrous,  sometimes  exclusively  fibrous, 
gliding  grooves  into  which  the  tendons  pass  when  they  are  inflected  to  change 
their  direction. 

The  tendinous  synodal  membranes  are  serous  membranes  lining  the  ten- 
dinous sheaths  and  covering  the  tendons  at  the  points  where  these  tn^o  parts 
correspond.    They  secrete  a  synovial  fluid  quite  like  that  of  the  articulations. 

When  they  almost  completely  envelop  the  tendon,  and  are  afterwards 
carried  to  the  walls  of  the  sheath,  they  are  termed  vaginal. 

Their  walls  are  composed  of:  1,  A  very  fine  conjunctival  membrane,  con- 
founded by  its  external  face  with  the  tendinous  sheath,  by  the  other  face  with 
the  tendon ;  2,  A  simple  layer  composed  of  pavement  epithelium,  extended 
over  the  whole  or  a  part  of  the  internal  face  of  the  conjunctival  membrane. 

manner  op  studying  the  muscles. 

A.  Classification. — To  facilitate  the  study  of  the  muscles,  two  methods 
may  be  employed  in  grouping  them.  The  first  consists  in  classifying  them 
according  to  their  uses  ;  describing,  for  example,  all  the  flexors,  extensors,  etc., 
of  the  same  region.  In  the  second  method,  the  uses  of  the  muscles  are  not 
taken  into  account,  their  relations  only  being  considered;  and  they  are 
divided  into  groups  or  regions,  which  comprise  all  the  muscles  situated 
around  a  bony  ray.  The  latter  is  the  method  now  adopted,  because  it  is 
the  most  convenient,  useful,  and  rational. 

(Leyh  describes  the  muscles  by  layers,  or  according  to  their  situation, 


184  THE  MUSCLES. 

which,  he  asserts,  facilitates  the  study  of  anatomy  in  a   surgical  point  of 
view}. 

B.  Peepaeation. — We  will  limit  ourselves  to  some  general  remarks  on  the  following 
points : 

Choice  of  a  subject. — If  there  is  for  disposal  a  certain  number  of  subjects  from  among 
which  it  is  possible  to  make  a  selection,  the  preference  should  be  given  to  those  thiit 
have  the  muscular  system  best  developed ;  not  that  large,  soft,  l}'mphatic  liorses  witli 
enormous  masses  of  muscle  should  be  chosen,  for  tliese  animals  are  always  less 
convenient  than  small  or  middle-sized,  well-bred  horses.  Asses  and  mules,  when  very 
emaciated,  answer  well  for  tlie  preparation  of  the  muscles. 

Position  of  the  suhject. — It  is  necessary  to  place  the  subject,  immediately  after  death, 
in  a  convenient  jDosition,  in  order  that  the  cadaveric  rigidity  may  set  in  while  it  is  in  tliat 
attitude.  Without  this  precaution,  the  various  parts  of  the  body  may  assume  an  incon- 
venient shape  or  direction,  and  all  attempts  to  amend  them  will  prove  almost  unavailing, 
particularly  in  the  larger  animals. 

Three  principal  positions  may  be  given  to  subjects : 

1.  The  animal  is  in  the  first  position  when  it  is  placed  on  its  back,  the  four  ex- 
tremities in  the  air,  and  maintained  in  that  posture  by  means  of  long  cords  passed 
round  the  pasterns  and  fixed  to  the  movable  rings  which  terminate  the  extremity  of  the 
fom-  bars  of  the  wheeled-table  on  which  the  subject  is  laid.  The  head  should  be  beyond 
the  end  of  the  table  and  rest  upon  a  stool.  The  animal  should  always  be  placed  in  such 
a  manner  that  the  head  be  opjiosite  the  forepart  of  the  table,  so  tliat  the  movements  of 
the  pole  or  shaft  be  not  impeded  during  the  displacement  of  the  apparatus.  In  order 
that  the  neck  be  not  twisted  to  the  right  or  left,  in  attaching  the  fore-limbs  the  siiliject 
should  be  raised  so  that  the  withers  rest  lightly  on  the  table.  According  to  the  bulk  of 
the  animal  and  the  length  uf  the  bars,  the  ropes  should  be  passed  around  either  the 
pasterns,  above  the  fetlocks,  or  even  above  the  knees. 

2.  To  place  the  animal  iu  the  second  'position,  it  is  turned  on  the  belly,  the  two 
thighs  flexed,  the  extremities  carried  beyond  the  table,  and  the  head  fixed  between  two 
bars  by  means  of  a  rope  passed  under  the  zygomatic  arches. 

3.  The  subject  is  in  the  third  position  wlien  it  rests  on  its  side. 

Rules  to  be  observed  during  the  preparation.— \.  By  no  means,  if  possible,  remove  the 
skin  from  the  regions  to  be  dissected  until  quite  ready  to  begin  the  dissection.  I  f  this  is 
impossible,  then  take  the  precauti  »n  of  enveloping  these  regions  in  damp  cloths,  or  in 
the  animal's  skin,  to  prevent  desiccation  of  tlie  aponeuroses  and  tlie  superficial  muscles. 

2.  To  dissect  a  muscle,  it  is  necessary  to  remove  the  aponeuroses  or  the  other 
muscles  which  cover  it,  the  cellular  tissue  enveloping  it,  and  the  fat,  glands,  vessels,  and 
nerves  lodged  in  the  neighbouring  interstices.  The  aponeuroses  should  be  removed  in 
shreds  by  making  tliem  very  tense  with  the  forceps,  but  without  raising  them,  and 
causing  the  blade  of  tlie  scalpel  to  glide  between  the  fibrous  and  muscular  surfaces, 
keeping  it  always  parallel  to  these  two  planes.  The  covering  muscles  slinuld  not  be 
entirely  excised,  but  ought  to  be  cut  through  the  middle,  across  their  fibres,  and  the 
ends  thrown  back ;  in  this  way  it  is  always  possible  to  replace  a  muscle  by  bringing  the 
two  portions  together ;  the  study  of  its  relations  is  then  much  more  easy.  The  cellular 
tissue  is  got  rid  of  by  removing  it  with  the  forceps,  and  carrying  the  edge  of  the  scalpel 
in  the  re-entering  angle  formed  by  the  cellular  layer  and  the  surface  of  the  muscle. 
This  method  also  suffices  for  removing  aponeiuoses  when  they  are  slightly  adherent  to 
the  muscular  fibres.  But  when  they  give  attachment  to  these  by  their  under  face,  as 
may  be  noticed  in  the  external  scapular  aponeurosis,  it  is  necessary  to  have  recourse  to 
the  method  indicated  above.  To  remove  fat,  glands,  etc.,  scissors  will  be  found  very 
advantageous. 

Order  to  follow  in  preparing  all  the  muscles  of  the  same  subject,  and  to  derive  most 
advantage  therefrom. — 1.  Place  the  subject  in  the  first  position,  and  commence  by  study- 
ing the  muscles  of  the  inferior  abdominal  region.  Then  excise  them,  leaving  the  posti'rior 
extremity  of  the  great  pectoral  muscle,  the  prepubic  tendon,  and  the  crural  arch  intact. 
The  abdominal  cavity  having  been  emptied  of  the  viscera  it  contnins,  dissect  and  study 
successively  the  diai)hragm,  the  internal  crural  region,  except  the  deep  muscles,  the 
Bublumbar  region,  the  femoral  and  posterior  crural  regions,  the  superficial  muscles  of 
the  inferior  cervical  region,  and  the  pectoral  region. 

2.  After  detaching  for  future  use  one  of  the  anterior  limbs,  the  animal  is  plnced  in  the 
second  positinn,  and  one  after  another  may  be  dissected  the  muscles  of  the  ear.  those  of 
the  superior  cervical  region,  the  croup  and  costal  regions,  except  the  triangular  muscle, 
and  the  spinal  region  of  the  back  and  loina. 


GENERAL  CONSIDERATIONS  ON  THE  STRIPED  MUSCLES.         185 

3.  The  regions  of  the  anterior  limb  may  be  prepared  at  the  same  time,  or  immediately 
afterwards. 

4.  Separate  the  two  posterior  limbs  by  sawing  the  femurs  through  their  middle,  and 
proceed  to  the  dissection  of  the  muscles  of  the  posterior  leg  and  foot. 

5.  By  means  of  another  application  of  the  saw  across  the  middle  of  the  loins,  the 
pelvis  is  completely  isolated  for  the  preparatum  of  the  coccygeal  muscles,  and  the  deep 
muscles  of  the  internal  crural  region,  nearly  as  they  are  represented  in  figures  9U 
and  131. 

6.  The  animal  being  placed  on  its  side,  the  pectoral  cavity  is  opened  by  sawing 
through  the  ribs  near  their  extremities ;  on  the  two  particular  portions  thus  obtained 
may  be  studied,  in  one  part,  the  triangularis  of  the  sternum,  and  in  the  other  the  deep 
muscles  of  the  inftrior  cervical  region,  including  the  long  muscle  of  the  neck  and 
the  anterior  and  lateral  straight  muscles  of  the  head. 

7.  Lastly,  the  head  is  disarticulated  and  the  muscles  of  this  region  are  prepared 
The  subject  may  afterwards  serve  for  the  study  of  nearly  all  tlie  articulations. 
Freser  rat  ion  of  the  muscles. — The  muscles  maybe  preserved  by  immersing  them  in 

appropriate  fluids,  and  the  muscular  preparations  by  drying  them. 

A  large  number  of  liquids  preserve  muscles  from  putrefaction.  We  may  mention 
alcohol ;  a  mixture  of  alcohol  and  spirits  of  turpentine ;  alcohol,  water,  and  chloroform  ;  a 
solution  of  siUphate  of  iron,  bichloride  of  mercury,  or  arsenious  acid.  The  best  preservative 
fluid,  however,  is  nitric  acid  diluted  with  water,  in  the  proportion  of  one  of  the  former 
to  three  of  the  latter.  The  acid  hardens  the  muscles  and  softens  the  conjunctival 
tissue ;  this  allows  all  the  interstices  to  be  completely  cleared  out,  and  even  permits  the 
primitive  muscular  fasciculi  which  have  been  concealed  by  the  white  tissues  to  be  exposed. 
Desiccation,  after  immersion  in  a  bath  of  arsenious  acid  or  sulphate  of  iron,  causes 
the  muscles  to  become  hardened  and  deformed.     It  is  therefore  a  bad  procedure. 

(A  careful  dissection  of  the  muscles,  with  regard  to  their  origin,  insertion,  action,  and 
relations,  is  of  infinite  importance  to  the  student  of  human  anatomy ;  to  the  Veterinary 
Student  it  is  no  less  important,  and  more  particularly  with  reference  to  the  muscles  of  the 
limbs.  A  correct  knowledge  of  their  situation,  attachments,  and  functions  is  often  the 
only  guide  the  Veterinary  Surgeon  can  rely  upon  in  the  diagnosis  of  those  api^arently 
obscure  cases  of  lameness  which  are  of  such  comparatively  frequent  occurence.  In  the 
words  of  Mr.  Henry  Gray,  we  may  repeat  that  "  an  accurate  knowledge  of  the  points  of 
attachment  of  the  muscles  is  of  great  importance  in  the  determination  of  their  action. 
By  a  knowledge  of  the  action  of  the  muscles,  the  surgeon  is  able  at  once  to  explain  the 
causes  of  displacement  in  the  various  forms  of  fracture,  or  the  causes  which  produce 
distortion  in  the  various  forms  of  deformities,  and,  consequently,  to  adopt  appropriate 
treatment  in  each  case.  The  relations  also  of  some  of  the  muscles,  especially  those  in 
immediate  apposition  with  the  larger  bloodvessels,  and  the  surface  markings*  they  pro- 
duce, should  be  especially  remembered,  as  they  form  most  useful  guides  to  the  surgeon 
in  the  application  of  a  ligatm-e  to  these  vessels." — '  Anatomy,  Descriptive  and  Surgical.' 

An  accurate  knowledge  of  the  muscular  system  is  also  of  great  service  to  the 
Veterinary  Surgeon  in  estimating  the  value  to  be  placed  upon  the  external  conformation 
presented  by  animals  intended  for  different  kinds  of  labour. 

"  In  dissecting,"  says  Mr.  Holden,  "  there  are  four  principal  objects  to  be  constantly 
borne  in  mind  by  the  student :  1st,  The  impression  on  the  memory  of  those  facts  of 
general  anatomy  taught  in  the  lectures.  2nd,  The  study  of  those  parts  of  the  body 
more  especially  concerned  in  surgical  atfections  and  operations.  3rd,  The  education  of 
the  sense  of  touch,  and  of  the  hand  in  the  use  of  instruments  ;  and  4th,  The  education 
of  the  eye  in  the  knowledge  of  the  several  tissues  of  the  body,  in  various  positions,  and 
varying  circumstances.  .  .  .  The  education  of  the  eye  is  a  gradual  and  tedious  process, 
but  one  which  is  pretty  certain  to  be  satisfactorily  accomplished  if  the  student  do  but 
use  his  hands  properly,  and  therefore  a  few  words  on  the  manual  part  of  dissection  may 
not  be  out  of  place. 

"  First,  as  to  the  instruments  requisite  for  dissection.  A  case,  containing  six  or  eight 
scalpels,  two  pairs  of  scissors,  a  pair  of  dissecting  forceps,  a  set  of  chain-hooks,  a  blow- 
pipe, and  a  probe,  will  enable  the  student  to  make  all  requisite  dissections,  supposing 
that  he  is  allowed  the  use  of  a  saw  and  chisel  in  the  dissecting-room.  Great  variety 
exists  in  dissecting-cases,  both  as  to  form  and  expense,  but  so  long  as  the  instruments 
themselves  are  strong  and  good,  the  simpler  the  case  the  better.  Scalpels  for  dissection 
are  made  of  two  principal  shapes ;  in  one,  the  edge  is  bevelled  to  the  point,  the  back 
being  straight;  in  the  other,  both  back  and  edge  are  bevelled  to  a  point  midway 
between  the  two.  The  latter  form  is  preferable  for  most  purposes.  The  blade  should 
not  be  more  than  an  inch  and  a  half  long,  and  never  double  edged  ;  but  the  material  of 
which  the  handle  is  constructed  is  a  matter  of  indifferencer 


186  THE  MUSCLES. 

"  For  all  ordinary  dissection,  it  will  be  found  most  convenient  to  hold  the  scalpel 
like  a  pen;  but  for  cleaning  the  fascia  off  muscles,  and  following  out  small  nerves,  it  is 
better  to  hold  it  reversed,  so  that  the  hack  of  the  knife  may  be  against  the  tissue  which 
is  to  be  preserved.  In  making  the  first  incision  through  the  skin  of  a  limb,  or  in  any 
other  position  where  a  long  incision  is  required,  the  knife  may,  with  advantage,  be  held 
under  the  hand,  by  which  the  wrist  has  more  play,  and  the  student  has  the  opportunity 
of  practising  a  mode  of  holding  the  knife,  which  he  will  find  very  useful  when  operating 
on  the  living  body. 

"The  forceps  should  be  broad  at  the  extremities  and  coarsely  serrated,  so  that  it  may 
retain  a  firm  hold  on  small  portions  of  tissue.  It  is  very  important  that  the  forceps 
should  not  be  too  strong  in  the  spring,  for  in  that  case  it  becomes  so  fatiguing  to  the 
hand  that  it  is  impossible  to  continue  its  use  for  any  length  of  time.  The  forceps 
should  be  held  lightly  between  the  thumb  and  the  first  and  second  fingers  of  the  left 
hand,  which  may  be  steadied  by  resting  the  little  finger  on  a  neighbouring  part. 

"  The  chain-hooks  should  be  strong,  and  bent  in  the  direction  of  the  thickness  and 
not  of  the  breadth  of  the  steel,  as  is  sometimes  done.  These  latter  are  very  inferior, 
being  liable  to  be  unbent  imder  any  considerable  strain.  Care  should  be  taken  that  the 
chains  are  firmly  linked,  and  that  the  central  ring  is  sufficiently  stout  to  bear  any  force 
that  may  be  applied.  The  scissors  should  be  large  and  strong,  and  it  will  be  found 
advantageous  to  have  one  curved  pair,  which  is  very  useful  in  preparing  the  ligaments. 

"  The  student  will  do  well  to  bear  in  mind  that  he  will  probably  be  called  upon  in 
ftfter  life  to  operate  on  the  living  body,  the  only  true  preparation  for  which  is  careful 
dissection;  he  should  therefore,  as  "far  as  possible,  conduct  all  his  dissections  as 
methodically,  and  with  as  much  care,  as  if  operating  on  tiie  living  body. 

"  The  student  should  bear  in  mind  that  his  manual  lalx)ur  is  only  a  part  of  his  duty, 
and  will  be  thrown  away,  unless  he  at  the  same  time  study  the  description  of  the  part 
upon  which  he  is  engaged ;  he  should  not,  therefore,  carry  the  dissection  further  than  he 
can  learn  the  description  on  the  same  day,  and  at  the  subject,  and  should,  if  possible, 
re-peruse  the  description  in  the  evening,  and  always  on  the  next  morning,  before 
carrying  the  dissection  any  further.") 


CHAPTER  II. 
.    THE  MUSCLES   OF   MAMMALIA. 

Aktiole  I. — Muscles  of  the  Trunk. 

SUBCUTANEOUS    EEGION. 

This  only  comprises  a  single  muscle,  the  fleshy  panniculus  (pannicidus 
carnosus),  destined  to  move  the  skin  covering  the  trunk.  Strictly  si^eaking, 
however,  we  may  describe  as  dermal  muscles  all  those  which  are  attached  to 
the  inner  surface  of  the  superficial  integument — the  muscles  of  the  face,  for 
example; 

Fleshy  Panniculus. 

Preparation. — Place  the  animal  on  its  side,  and  carefully  remove  the  skin,  allowing 
the  cuticular  muscle  to  remain  on  the  subjacent  muscles. 

Situation — Form — Extent. — Situated  on  the  inner  surface  of  the  skin  cover- 
ing the  sides  of  the  thorax  and  abdomen,  the  fleshy  panniculus  is  an  immense 
broad  muscle,  irregularly  triangular  in  shape,  thin  at  its  borders,  and 
thicker  in  the  middle  than  elsewhere. 

The  upper  border  corresponds  to  a  curved  line,  convex  superiorly,  and 
extending  obliquely  from  the  flank  to  the  withers.  The  inferior  border  is 
carried  horizontally  from  the  flank  to  the  j)osterior  border  of  the  olecranian 
mass  of  muscles,  passing  along  the  upper  margin  of  the  great  pectoral 
muscle,  which  it  covers,  and  to  which  it  adheres  somewhat  closely.    The 


MUSCLES  OF  THE  TRUNK.  187 

anterior  border  descends  from  tlie  superior  extremity  of  the  shoulder  on  to 
the  muscles  of  the  fore-ai-m. 

Structure — Attachments. — The  fleshy  fibres  entering  into  the  composition 
of  this  muscle  are  dii'ected  forward  for  its  posterior  two-thirds ;  but  on 
arriving  on  the  shoulder  they  gradually  straighten  and  become  vertical. 
They  are  continued,  on  the  margins  of  the  muscle,  by  aponem-oses  which 
attach  it  either  to  the  internal  surface  of  the  skin  or  to  the  fibrous  fasciaj 
of  the  superficial  muscles. 

This  muscle  has,  besides,  a  very  remarkable  insertion  into  the  hiunerus, 
which  was  noticed  by  G.  Cuvier,  in  his  'Lecons  d' Anatomic  Comparee,' 
and  which  appears  to  have  been  omitted,  at  least  so  far  as  Solipeds  are 
concerned,  in  every  treatise  on  Veterinary  Anatomy.  The  following  is  what 
we  have  often  observed  in  this  respect : — On  reaching  the  posterior  border  of 
the  ulnar  mass  of  muscles,  the  panniculus  divides  into  two  superposed 
layers  :  one,  superficial,  is  carried  to  the  muscles  of  the  anterior  member ; 
the  other,  deep,  soon  terminates  by  an  aponeurosis  which  is  united  to  the 
great  pectoral  muscle,  and  is  bordered  at  its  upper  margin  by  a  nacrous 
aponeurotic  band,  which  penetrates  between  the  thorax  and  the  muscles  of 
the  arm  to  be  fixed  to  the  small  trochanter. 

JRelations. — By  its  superficial  face, ,  with  the  skin,  to  which  it  closely 
adheres ;  by  its  deep  face,  with  the  great  dorsal,  the  dorsal  portion  of  the 
trapezius,  the  abdominal  tunic,  the  great  oblique  muscle  of  the  abdomen,  the 
great  serratus,  some  external  intercostals,  the  spur  vein,  and  the  superficial 
muscles  of  the  shoulder  and  arm. 

Action. —  The  animal,  in  contracting  this  muscle,  shakes  the  whole  of  the 
cutaneous  integument  which  covers  it :  thus  preventing  insects  from  alighting 
on  the  surface  of  the  body,  or  tormenting  by  their  bites  or  stings. 

In  the  Bog,  the  panniculus  camosus  is  prolonged  over  the  croup,  and  is  united  along 
the  dorso-lumbar  spine  to  that  of  the  opposite  side.     It  is  very  developed  in  the  Cat. 

CERVICAL    REGION. 

This  region  comprises  all  the  muscles  grouped  around  the  cervical 
vertebrse — muscles  which  are  conspicuous  by  their  volume  and  the  important 
part  they  play  in  the  animal  economy.  There  are  described  a  superior  and 
an  inferior  cervical. 

A.  Superior  Cervical,  or  Spinal  Begton  of  the  Neck. 
This  includes  seventeen  pairs  of  muscles,  which  are :  the  cervical  portion 
of  the  trapezius^  rhomhoideus,  amjularis  of  the  scapula,  splenius,  great  complexus, 
small  complexus,  transverse  spinous  of  the  neck,  the  six  intertransverse  muscles  of 
the  neck,  great  oblique  muscle  of  the  head,  great  posterior  rectus,  and  small  pos- 
terior rectus.  These  form  fom-  superposed  layers  on  each  side  of  the  cervical 
ligament,  and  occupy  the  triangular  space  circumscribed  by  the  upper 
border  of  that  ligament,  the  transverse  processes  of  the  vertebrae  of  the  neck, 
and  the  spinous  process  of  the  second  dorsal  vertebra. 

Freparation.—'Place  the  subject  in  the  second  position  and  dissect  in  succession  the 
four  layers  of  the  region.  To  study  the  first  layer,  which  is  formed  by  the  cervical  portion 
of  the  trapezius,  remove  the  skin,  cellular  tissue,  and  the  fibrous  fascia  covering  that 
muscle  (See  fig.  102).  The  prej  aration  and  study  of  the  second  layer,  composed  of  the 
rhomboideus.  angtxlaiis.  and  splenius.  is  Ciirried  out  in  two  stages.  In  the  first,  the 
trapeziiun  and  the  mastoido-hutueralis  is  removed,  leaving  only  the  cer\ical  insertions 


For  the  description  of  this  muscle,  see  the  Spinal  Kegion  of  the  back  and  loins. 


188 


THE  MUSCLES. 


of  the  latter  muscle  ;  then  the  limb  is  removed  by  sawing  through  the  scapula  beneath 
the  insertions  of  tlie  angularis  and  great  serrated  muscles,  as  in  figure  105.  But  as 
neither  the  cervical  or  dorsal  insertions  of  the  sjilenius  are  exposed,  it  is  necessary  to 
proceed  to  the  second  part  of  the  operation  by  removing  the  rhomboideus,  angularis, 
and  the  superior  extremity  of  the  shoulder.  To  prepare  the  third  layer,  which  com- 
prises the  great  and  small  complexus,  it  is  sufficient  to  excise  the  splenius,  in  following 
the  direction  of  the  neck,  and  to  turn  upwards  and  downwards  the  two  portions  of  the 
muscle  (^See  fig.  100).  Lastly,  the  deep  layer — the  transverse  spinous,  intertransverse, 
oblique,  and  jDosterior  straight  muscles,  as  well  as  the  cervical  ligament — is  exposed  by 
removing  the  two  complexus  and  the  ilio-spiualis  muscles  (See  fig.  104). 

1.  Bhomhoideus.    (Figs.  101,  6;  104,  1,  2.) 

Synonyms. — Described  by  Bourgelat  as  two  muscles,  the  proper  elevator  of  the 
shoulder  and  the  rhomboideus,  these  were  termed  by  Girard  the  cervico-subscapularis 
and  dorso-subscapularia.  (This  is  the  rhomboideus  longus  and  brevis  of  Percivall,  and 
the  dorso-scapularis  and  cervico-subscapularis  of  Leyh.) 

Form — Situation — Direction. — This  muscle  has  the  form  of  a  very 
elongated  triangle,  and  is  situated  at  the  inner  as2:)ect  of  the  cervical 
trapezius  and  the  scapular  cartilage,  beneath  the  cervical  ligament,  whose 
direction  it  follows. 

Fig.  101. 


LATERAL   VIEW   OF   THE   NECK;   SUPERFICIAL  MUSCLES. 

1,  1,  Parotid  gland;  2,  Sterno-maxillaris  and,  14,  Its  junction  with  its  fellow  of  the 
opposite  side;  3,  4,  ]\Iastoido-humeralis,  or  levator  humeri;  5,  Splenius;  6, 
Ehoniboideus ;  7,  Funicular  portion  of  the  cervical  ligament,  or  ligamentum 
colli;  8,  Angularis  of  the  scapula;  9,  Supra-,  or  antea-spinatus ;  10,  Trapezius; 
11,  Infra-,  or  postea-spinatus ;  12,  Jugular  vein;  13,  Subscapulo-hyoideus ; 
15,  Trachea. 


Structure — Attachments. — It  is  composed  of  thick,  fleshy  fasciculi,  the 
anterior  of  which  are  oblique  downwards  and  backwards,  the  posterior 
passing  directly  downwards.  These  fasciculi  are  fixed  by  tlieir  superior 
extremity  to  the  funicular  portion  of  the  cervical  ligament  and  the  summits 
of  the  spinous  processes  of  the  four  or  five  dorsal  vertebra3  succeeding  the 


MUSCLES  OF  THE  TBUXK.  189 

first — fixed  insertion ;  by  their  inferior  extremity,  to  the  inner  aspect  of  the 
scapular  cartilage,  where  the  anterior  fasciculi  are  confounded  with  those  of 
the  angularis. 

Relations. — Covered  by  the  cervical  portion  of  the  trapezius,  the  scapular 
cartilage,  and  the  aponeurosis  of  the  great  dorsal  miiscle,  the  rhomboideus 
covers  the  sphenius,  which  is  excavated  near  its  superior  border  for  its 
reception,  as  well  as  the  aponeurosis  of  the  anterior  small  serrated  muscle 
thi'ough  the  medium  of  a  yellow  elastic  lamina. 

Action. — It  draws  the  shoulder  upwards  and  forwards. 

2.  Anguhns  Muscle  of  the  Scajmla.     (Figs.  102,  4;  105,  3.) 

Synonyms. — Trachelo-subscapularis — Girard.  Portion  of  the  serratus  magnua 
— Bourgelat.  Elevator  of  tlie  scapula — Cuvier.  (Anterior  portion  of  the  serratus 
magnus  of  PercivaU.     The  levator  anguli  scapulis  of  Man.) 

Situation — Form — Structure. — This  is  a  very  strong  muscle,  situated  in 
front  of  the  shoulder,  triangular,  flattened  on  both  sides,  thin  at  its  superior 
border,  thick  behind  and  below,  and  almost  entirely  fleshy. 

Attachments. — It  takes  its  origin  from  the  transverse  processes  of  the  five 
last  cervical  vertebrte  by  five  distinct  portions,  which  are  directed  towards 
the  scapula  in  converging  towards  each  other,  and  soon  join  to  form  a  single 
muscular  body,  which  is  inserted  into  the  internal  face  of  the  scapula,  on  its 
anterior  triangular  surface. 

Eekitions. — This  mtiscle  is  confounded  at  its  inferior  border  with  the 
serratus  magnus.  It  is  covered  by  the  cervical  trapezius,  the  mastoido- 
humeralis,  and  the  small  pectoral  muscle.  It  covers  the  splenius,  the  in- 
ferior branch  of  the  ilio-spinalis,  and  the  common  intercostal  muscle.  Near 
its  junction  with  the  serratus  magnus,  its  internal  face  adheres  very 
closely  to  the  transverse  processes  of  the  three  first  dorsal  vertebrte. 

Action. — It  draws  forward  the  superior  extremity  of  the  scapula,  while 
the  humeral  angle  is  carried  backwards.  If  the  shoulder  becomes  the  fi-sed 
point,  it  can  act  in  the  extension  or  lateral  inclination  of  the  neck. 

3.  S})lenius.     (Figs.  105,  4,  5  ;  106,  5.) 
Synonyms. — Cervico-trachelian — Girard. 

Form — Situation. — A  considerable  muscle,  flattened  on  both  sides, 
triangular,  and  comprised  between  the  cord  of  the  cervical  ligament,  the 
inferior  branch  of  the  ilio-spinalis  muscle,  and  the  transverse  processes  of  the 
four  first  cervical  ribs. 

Structure. — The  splenius,  aponeurotic  only  at  its  periphery,  is  composed 
of  thick  fleshy  fasciculi  which  are  all  directed  forwards  and  upwards,  to 
reach  the  head  and  the  first  cervical  vertebrje. 

Attachments. — It  is  fixed,  by  its  posterior  border,  to  the  lip  of  the 
cervical  ligament  and  the  summits  of  the  spinous  processes  of  the  first 
dorsal  vertebrae,  by  means  of  an  aponeurosis  which  is  continuous  behind 
with  that  of  the  small  anterior  serratus,  and  confounded,  by  its  inner  surface, 
with  that  of  the  great  complexus.  Its  anterior  border  is  cut  into  four  or 
five  digitations  which  constitute  the  movable  insertions  of  the  muscle : 
a.  The  superior  digitation  is  the  widest  and  thinnest,  and  terminates  in  an 
aponeurosis  (Fig.  105,  5),  which  unites  it  to  the  mastoid  tendon  of  the  small 
complexus,  and  passes  to  the  mastoid  crest,  b.  The  second  joins  a  very 
strong  tendon  common  to  the  splenius,  the  small  complexus,  and  the 
mastoido-hmneralis,  which  tendon  is  attached  to  the  transverse  process  of 


190 


THE  MUSCLES. 


the  atlas  (Fig.  105,  9).  c,  d.  The  two  or  three  others  are  dii-ectly  inserted 
into  the  transverse  processes  of  the  third,  foui'th,  and  fifth  cervical 
vertebrsB. 

Belations. — The  splenius  is  related,  outwardly,  to  the  rhoniboideus,  the 
angularis,  cervical  trapezius,  and  mastoido-humeralis ;  inwardly,  to  the  two 
complexus  and  two  oblique  muscles  of  the  head ;  by  its  inferior  border,  to 
the  superior  margin  of  the  inferior  branch  of  the  ilio-spinalis  (longissimus 
dorsi). 

Action.— li  extends  the  head  and  neck  in  inclining  them  to  one  side.  If 
the  two  act  in  concert,  the  extension  is  direct. 

Fig.  102. 


SUPERFICIAL  MUSCLES  OF   THE   NECK   AND   SPINAL   REGION   OF   THE   RACK   AND   LOINS. 

1,  Dorsal  trapezius;  2,  Great  dorsal;  3,  Cervical  trapezius;  4,  Levator  anguli 
scapulae;  5,  Spleaius;  6,  Anterior,  or  superficial  portion  of  the  mastoido-hume- 
ralis ;  7,  Its  humeral  insertion;  7'  Its  mastoid  insertion ;  8,  The  thin  aponeurosis 
uniting  this  insertion  to  the  sterno-maxillary  muscle;  8',  Posterior  portion  of  the 
mastoido-humeralis ;  9,  Its  inferior  aponeurosis  inserted  into  the  interstice  of  the 
long  abductor  of  the  arm  ;  10,  Sterno-maxillaris ;  11,  Subscapulo-hyoideus;  12, 
Porlion  of  the  dermal  muscle  of  the  neck;  13,  Portion  of  the  great  extensor  of 
the  fore-arm;  14,  Posterior  belly  of  the  long  abductor  of  the  arm;  15,  Great 
pectoi'al  muscle. 


MUSCLES  OF  THE  TRUNK.  191 

4.  The  Ch-eat  Complexus.     (Fig.  106,  6,  7.) 
Synonyms. — Dorso-occipitalis —  Girard.    (Complexus  major — Percivall.') 

Situation — Direction — Form. — A  powerful  muscle,  included  between  the 
internal  surface  of  the  splenius  and  the  cervical  ligament,  whose  oblique 
direction  forwards  and  upwards  it  follows  ;  it  is  triangular,  flattened  on  both 
sides,  elongated  from  before  to  behind,  and  divided  longitudinally  into  two 
unequal  portions — a  posterior  and  anterior. 

Structure. — The  posterior  portion  (Fig.  106,  6),  the  most  considerable, 
is  aponeurotic  at  its  origin,  intersected  by  linear  fibrous  bands  which  obliquely 
cross  its  direction,  and  is  formed  of  fleshy  fibres  directed  forwards.  Those 
which  compose  the  anterior  portion  (Fig.  106,  7),  intermixed  with  some 
tendinous  fasciculi,  are  directed  upwards,  and  appear  to  be  inserted  into  the 
preceding.  It  is  this  difference  in  the  direction  of  the  fibres  of  the  two 
portions  of  the  great  complexus  which  allows  them  to  be  distinguished  from 
one  another ;  the  two  being  only  really  separated  by  an  interstice  near  their 
inferior  extremity.  Superiorly,  the  muscle  is  constricted  to  form  the 
summit  of  the  elongated  triangle  it  represents,  and  terminates  by  a  strong 
tendon. 

Fixed  insertions. — The  posterior  portion  derives  its  origin :  1,  From  the 
summit  of  the  spinous  processes  of  the  first  dorsal  vertebrae,  by  a  strong 
aponeurosis  which  is  confounded  with  that  of  the  splenius  and  the  anterior 
small  serratus ;  2,  From  the  transverse  processes  of  the  four  or  five  dorsal 
vertebrae  which  follow  the  second,  by  as  many  aponeurotic  digitations  united 
by  their  margins.  The  anterior  portion  is  fixed :  1,  To  the  transverse 
processes  of  the  two  first  dorsal  vertebra,  by  two  tendinous  digitations 
analogous  to  those  of  the  posterior  portion ;  2,  To  the  articular  tubercles  of 
the  cervical  vertebrae,  by  the  inferior  extremity  of  its  fleshy  fasciculi. 

Movable  insertion. — The  movable  insertion  of  the  great  complexus  is 
effected  through  its  superior  tendon,  which  is  fixed  to  the  posterior  face  of 
the  occipital  protuberance,  beside  the  cervical  tuberosity. 

Relations. — It  is  covered  by  the  splenius  and  the  small  complexus.  It 
covers  the  cervical  ligament,  the  upper  branch  of  the  ilio-spinalis,  the  trans- 
verse spinous  of  the  neck,  and  the  oblique  and  posterior  straight  muscles  of 
the  head.  The  aponeurotic  digitations  which  attach  it  to  the  dorsal  trans- 
verse processes  are  comprised  between  the  two  branches  of  the  ilio-spinalis. 
The  interstice  which  separates,  inferiorly,  the  two  portions  of  the  muscle 
affords  a  passage  to  the  superior  cervical  artery. 

Action. — It  is  a  powerful  extensor  of  the  head. 

5.  Small  Complexus.    (Figs.  105,  6,  7 ;  106,  8,  9.) 
Synonyms. — Dorso-mastoideus— (remrd.    (JTrachelo-mastoideus — Percivall.') 

Situation — Direction. — Situated  at  the  internal  face  of  the  splenius,  in  an 
oblique  direction  upwards  and  forwards,  this  muscle  lies  along  the  anterior 
border  of  the  great  complexus,  and  follows  the  inferior  branch  of  the  ilio- 
si)inalis,  which  it  appears  to  continue  to  the  head. 

Form — Structure. — The  small  complexus  is  a  long  muscle,  divided  into 
two  fleshy,  fusiform,  and  parallel  portions — anterior  and  posterior — which  we 
might  strictly  consider  as  two  distinct  muscles.  Both  are  composed  of 
successive  fasciculi,  which  become  longer  as  they  are  superficial,  and 
terminate  by  a  tendon  at  their  superior  extremity.  The  tendon  of  the 
posterior  muscle  is  flattened,  and  joins  the  mastoid  aponeurosis  of  the 


192 


TEE  MUSCLES. 


splenius.  That  of  the  anterior  muscle  is  funicular,  and  receives,  before  its 
insertion,  a  digitation  from  the  sj)lenius  (fig.  106,  10),  and  another  from  the 
mastoido-humeralis  (fig.  106). 

Fixed  attachments. — The  two  fleshy  portions  of  the  small  complexus  have 
their  fixed  insertion  in  common  with  the  anterior  portion  of  the  great  com- 
plexus :  1,  On  the  transverse  processes  of  the  two  first  dorsal  vertebrte, 
through  the  medium  of  aponeurotic  digitations  which  serve  as  an  origin  to 
the  last-named  muscle ;  2,  On  the  articular  tubercles  of  the  cervical  vertebrae, 
by  the  inferior  extremity  of  their  component  fasciculi. 

Movable  attachments. — The  terminal  tendon  of  the  posterior  muscle 
passes  to  the  mastoid  process  of  the  temporal  bone.  The  anterior  passes  to 
the  transverse  process  of  the  atlas. 

Fis.  103. 


LATERAL   VIEW   OF   THE   NECK;   MIDDLE   LAYER   OF   MUSCLES. 

1,  Funicular  portion  of  the  cei-vical  ligament ;  2,  Complexus  major ;  3,  Complexus 
minor;  4,  Rectus  capitis  posticus  major;  5,  Rectus  capitis  posticus  minor;  6, 
Stylo-maxillaris ;  7,  Carotid  artery ;  8,  Pneumogastric  nerve  and  branch  of 
sympathetic;  9,  Longus  colli;  10,  Recurrent  nerve;  11,  Inferior  scalenus;  12, 
Spinalis,  or  trausversalis  colli ;  13,  Incision  through  rhomboideus  and  trapezius  ; 
14,  Trachea. 

Belations. — Outwardly,  with  the  splenius;  inwardly,  with  the  great 
eomplexus  and  the  oblique  muscles  of  the  head.  The  tendon  of  the  posterior 
fleshy  portion  is  covered  by  the  mastoid  aponeurosis  of  the  mastoido- 
humeralis. 

Action. — The  small  complexus  inclines  to  its  side  the  head  and  upper 
part  of  the  neck.     It  also  acts  as  an  extensor  of  the  head.* 

'  Bourgelat  has  described,  by  the  name  of  long  transversal,  the  anterior  portion  of  this 
miiscle,  and  attached  it  to  the  posterior  portion  of  the  splenius.  We  do  not  know 
where  to  find  one  or  other  of  these  in  Ihe  crude  description  of  Lafosse  and  Vitet.  Girard 
considered  them,  like  ourselves,  as  a  single  muscle,  which  he  designates  tlie  dorso- 
mastoideus.  Rigot  has  united  them  with  the  anterior  portion  of  the  great  complexus  and 
the  foremost  fasciculi  of  the  short  transverse  muscle  (inferior  branch  of  the  ilio-spinalis), 
to  make  his  long  transversal;  in  doing  so  he  has  only  complicated  their  description. 
These  two  muscular  fasciculi,  being,  to  oiu-  view,  exactly  represented,  the  posterior,  at 


MUSCLES  OF  THE  TBUSK.  193 

6.  Tramverse  Sjnnoiis  Muscle  of  the  Nech     (Fig.  104,  4.) 

Synonyms. — Short  spinous — Boimjelat.     Dorso-spinalis — Girard.     (^Spinalis  coUi — 
Percicall.     Transversal  is  colli  of  Man.) 

Situat{o7i. — Between  the  great  complexiis  and  the  cervical  ligament,  on 
the  laniinte  of  the  last  five  vertebrae  of  the  neck. 

Form — Structure — Attachments. — This  muscle,  a  continuation  in  the 
cervical  region  of  that  of  the  back  and  loins,  is  generally  formed  of  five 
thick  and  short  fasciculi,  strongly  aponeurotic,  directed  forwards,  upwards, 
and  inwards. 

These  fasciculi,  attached  by  their  posterior  extremities — fixed  insertion — to 
the  five  last  articular  tubercles  of  the  cervical  region,  are  fixed  by  their 
anterior  or  superior  extremities — movable  insertion — into  the  sixth,  fifth,  foui"th, 
third,  and  second  spinous  processes  of  that  region. 

Relations. — Outwards,  with  the  great  complexus ;  inwards,  with  the 
superior  branch  of  the  ilio-spinalis  and  the  cervical  ligament.  By  its 
anterior  face,  with  the  laminae  of  the  cervical  vertebrae  and  the  interlamellar 
ligaments. 

Action. — An  extensor  and  flexor  of  the  cervical  spine. 

7.  Intertransversal  Muscles  of  the  Nech.     (Fig.  104,  9.) 

Synonyms. — Intercervicals — Girard.  (The  intertraiisversales  oi  Man.  Not  mentioned 
by  Percivall.) 

These  are  six  small,  short,  and  very  tendinous  fasciculi,  each  of  which 
is  doubled  into  two  secondary  fasciculi,  a  suj^erior  and  inferior.  They  are 
lodged  in  the  lateral  excavations  comprised  '«ithin  the  transverse  and  artic- 
idar  processes  of  the  cervical  vertebrae,  and  are  carried  from  one  vertebra 
to  another,  except  from  the  first  to  the  second.  Covered  by  the  cervical 
attachments  of  the  majority  of  the  muscles  of  the  neck,  they  cover  the 
vertebrae  to  which  they  are  attached,  as  well  as  the  vertebral  arteries  and 
veins,  and  the  intervertebral  foramen.     They  incline  the  neck  to  the  side. 

8.  Great  Oblique  Muscle  of  the  Head.     (Fig.  104,  7.) 
Synonyms. — Axoido-atloideus — Girard.    {Obliquus  capitis  inferior — Percivall.) 

Form — Direction — Situation. — A  short,  thick,  and  broad  muscle,  oblique 
forwards  and  outwardly,  and  applied  to  the  superior  face  of  the  two  fii-st 
vertebrte  of  the  neck. 

Structure  and  Attachments. — Its  fibres  are  nearly  all  fleshy,  parallel  to 
each  other,  and  longer  as  they  become  superficial ;  they  are  attached  by  their 
posterior  extremity — fixed  insertion — to  the  external  face  of  the  spinous 
process  of  the  axis,  and  by  their  anterior  extremity — movable  insertion — to  the 
superior  surface  of  the  transverse  process  of  the  atlas. 

Relations. — Outwards,  with  the  splenius,  the  great  and  little  complexus  ; 
inwards,  with  the  atlas,  the  axis,  and  the  atlo-axoid  articulation ;  above. 


least,  by  the  smxiU  complexus  of  anthropfitomists,  we  have  thought  it  proper  to  give  it 
that  name.  With  regard  to  the  muscle  generally  termed  the  small  complexus  by 
veterinary  anatomists,  following  the  example  of  Meckel  we  will  describe  it  as  a  portion 
of  the  great  posterior  straight  muscle  of  the  head. 

(Percivall  names  Girard's  axoido-occipitalis  longus  the  "  complexus  minor,"  and  his 
dorsoinastoideus  the  "  trachelo-maatoideus."  Leyh,  following  Girard,  designates  the 
latter  muscle  the  dorso-mastoideus.) 


194 


TEE  MUSCLES. 


with  the  posterior  straight  muscles  of  the  head ;  below,  with  the  anterior 
great  straight  muscle. 

Action. — It  pivots  the  atlas  on  the  odontoid  process  of  the  axis  ;  it  is 
therefore,  the  special  rotator  of  the  head. 


Fiff.  104. 


CERVICAL   LIGAMENT   AND   DEEP   MUSCLES  OF   THE   NECK. 

1,  Lamellar  portion  of  the  cervical  ligameat ;  2,  Funicular  portion  ;  3,  3.  The 
transversales  muscle  of  the  back  and  loins  ;  4,  4,  Transversales  of  the  neck  ;  5, 
Posterior  great  straight  muscle  of  the  head ;  6,  Small  ditto ;  7,  Great  oblique 
muscle  of  the  head ;  8,  Small  ditto ;  9,  9,  Intertransversales  of  the  neck ; 
10,  Anterior  great  straight  muscle  of  the  head;  11,  Inferior  scalenus  muscle; 
12,  Superior  ditto. 


9.  Small  Oblique.     (Fig.  104,  8.) 

Synonyms. — Atloido-mastoideiis — Girard.      (Ohliquus    capitis     superior — Percivall. 
Lateral  atloido-occipitaUs  of  Loyh.     Olliquus  superior  of  Man.) 

A  short,    thick,  quadrilateral,  and  strongly  aponeurotic  miiscle.     Its 
fibres  are  fixed  posteriorly — origin — to  the  lip  bordering  the  transverse  process 


MUSCLES  OF  THE  TRUNK  195 

of  the  atlas ;  they  are  carried  from  thence  forward,  upward,  and  inward,  to 
to  be  attached — termination — 1,  To  the  styloid  process  of  the  occipital  bones  ; 
2,  To  the  external  sm-face  of  that  bone,  on  the  imprints  which  border  the 
mastoid  crest  posteriorly ;  3,  To  the  mastoid  crest  itself.  This  muscle  is 
covered  by  the  mastoid  tendon  of  the  small  complexus,  by  the  superior 
aponeurosis  of  the  splenius,  and  that  of  the  mastoido-humeralis.  It  cuvers 
the  occipito-atloid  articulation,  the  occipital  insertion  of  the  posterior 
straight  muscles  of  the  head,  and  the  origin  of  the  occipito-styloid  and 
digastric  muscles.     It  inclines  the  head  on  the  atlas,  and  slightly  extends  it. 

10.  Posterior  Great  Straight  Muscle  of  the  Head.     (Fig.  104,  5.) 

Synonym^.— SxaaW  complexus  and  great  posterior  straight  muscle — Bourgelat.  Long 
and  short  axoido-occipitalis— (r/Vard.  {Complexus  minor  and  rectus  capitis  posticus 
major. — Perciiall.  Leyh  gives  this  muscle  the  same  designations  as  Girard.  It  is  the 
rectus  capitis  posticus  major  and  medius  of  Man.) 

Form — Structure — Situation. — Elongated,  prismatic,  easily  divisible  into 
two  fasciculi — one  superficial,  the  comj)le.rus  miiwr  of  Bourgelat  (and  Per- 
civall)  ;  the  other  deep,  the  great  posterior  straight  muscle  of  Bourgelat  (and 
the  rectus  capitis  posticus  major  of  Percivall) — entirely  fleshy,  and  formed  of 
parallel  fibres,  this  muscle  is  lodged,  with  the  small  posterior  straight 
muscle,  in  a  triangular  space  circumscribed  by  the  cord  of  the  cervical  liga- 
ment and  the  internal  border  of  the  oblique  muscles. 

Attachments. — It  is  attached,  by  its  superior  extremity,  to  the  whole 
extent  of  the  uneven  lip  which  terminates  the  spinous  process  of  the  axis — 
fixed  insertion.  Its  anterior  extremity  is  insinuated  beneath  the  small 
oblique  muscle,  and  is  fixed  to  the  occipital  bone,  behind  the  superior 
insertion  of  the  great  complexus,  whose  tendon  receives  some  of  the  fibres 
of  the  superficial  fasciculus — movable  insertion. 

Helations. — Above,  with  the  great  complexus ;  below,  with  the  small 
straight  muscle  ;  inwards,  with  the  cord  of  the  cervical  ligament  and  the 
analogous  muscle  of  the  opposite  side ;  outwards,  with  the  oblique  muscles. 

Action. — This  muscle,  a  congener  of  the  great  complexus,  aids  in 
extending  the  head. 

11.  Small  Posterior  Straight  Muscle.     (Fig.  104,  6.) 

Synonyms. — Atloido-occipitalis— G/rarrf.  (Rectus  capitis  posticus  minor— PercivalL 
The  Atioido-occipitalis  superior  of  Leyh.     The  rectus  capitis  posticus  minor  of  Man.) 

A  very  small,  wide,  and  triangular  muscle,  flat  above  and  below,  and  lying 
immediately  upon  the  fibrous  capsule  of  the  occipito-atloid  articulation.  It 
is  attached,  posteriorly,  to  the  superior  face  of  the  atlas — origin  ;  in  front,  to 
the  external  surface  of  the  occipital  bone,  below  the  preceding  muscle,  whose 
action  it  shares. 

B.  Inferior  Cervical  or  Trachelian  Begion. 

The  muscles  composing  this  region  are  situated  in  front  of  the  cervical 
vertebrae,  and  are,  for  the  most  part,  grouped  aruund  the  trachea,  which  they 
envelop  as  in  a  kind  of  sheath.  They  are  eleven  in  number  :  the  cuticular 
muscle  of  the  neck,  the  mastoido-humeralis,  sterno-maxillaris,  sterno-hyoideus, 
sterno-thyroideus,  omo-  or  suhscajndu-hyoideus,  the  great  and  small  anterior 
straight  muscles  of  the  head,  the  small  straight  lateral  muscle,  the  scalenus,  and 
the  long  muscle  of  the  neck. 


196  THE  MUSCLES. 

Preparation. — 1.  Place  the  animal  in  the  first  position.  2.  Remove  the  skin  of  this 
region,  in  order  to  expose  and  study  the  cuticular  muscle.  3.  Remove  that  muscle 
and  the  parotid  gland  to  prepare  the  mastoido-humeralis/  the  stylo-maxillaris,  sterno- 
hyoideus,  and  sterno-thyroideus.  4.  Transversely  cut  through  tiie  mastoido-humeralis 
near  the  angle  of  the  shoulder,  and  isolate  it  from  the  subscapulo-hyoidens  to  exjjose 
this  muscle ;  taking  care  to  preserve  the  jugular  vein  and  parotid  gland,  in  order  to  study 
their  relations  witii  it.  5.  Kemove  the  fore  limbs  ;  open  the  thoracic  cavity  by  sawing 
through  the  eight  first  ribs  near  their  suiDerior  extremity  ;  take  out  the  viscera  contained 
in  this  cavity,  as  well  as  the  trachea,  cesoi^hagus,  jiharynx,  and  larynx,  to  expose  the 
long  muscle  of  the  neck,  the  scalenus,  and  the  straight  muscles  of  the  head. 

1.  Subcutaneous  Muscle  of  the  Neck.     (Figs.  102,  12  ;  114,  1.) 

Si/noHymx. — It  has  been  described  by  Bourgelat,  and  the  majority  of  veterinary 
anatomists  wlio  have  followed  him,  as  two  muscles  :  the  cuticularis  of  the  neck  and  the 
face.     (Percivall  includes  this  muscle  in  his  description  of  the  paniiiculus  carnosus.) 

This  is  a  membraniform  expansion,  partly  fleshy,  partly  aponeurotic, 
which  covers  the  muscles  of  the  neck,  the  intermaxillary  space,  and  the 
face. 

The  fleshy  fibres  form,  in  front  of  the  neck,  a  thin  band,  which  is  united, 
through  the  medium  of  a  fibrous  raphe,  to  that  of  the  opjwsite  side.  This 
baud  is  in  contact  with  the  sterno-maxillary,  steruo-hyoid,  subscapulo-hyoid, 
and  sterno-thyroid  muscles,  as  well  as  the  jugular  vein :  enveloping  them 
all  as  in  a  sort  of  gutter.  It  gradually  thins  from  below  uj)wards,  in  such  a 
manner  that  around  the  upper  part  of  the  throat  it  is  only  composed  of  some 
scattered  fibres.  In  the  intermaxillary  sjiace,  and  on  the  expanding  borders 
of  the  maxillary  branches,  the  fleshy  fibres  appear  agam  of  a  certain 
thickness,  but  only  to  become  attenuated  on  the  external  sm'face  of  the 
cheeks. 

These  fleshy  fibres  leave  the  anterior  prolongment  of  the  sternum^  and 
intermediate  middle  raj^h^  of  the  two  muscles,  and  directing  their  course 
outwards  and  upwards,  soon  become  confounded  with  the  aponeurosis.  The 
latter,  extremely  thin,  is  spread  over  the  mastoido-humeralis,  the  sujierior 
cervical  muscles,  parotid  region,  and  the  cheeks,  and  is  finally  attached  to 
the  zygomatic  crest.  On  arriving  near  the  commissure  of  the  lips,  the 
cuticular  muscle  is  united  to  the  alveolo-labialis  (or  buccinator  muscle)  by 
a  fleshy  fasciculus  named,  in  Man,  the  risorius  santorini  (Fig.  110,  24). 

The  cuticularis  colli  braces  the  muscles  it  covers  during  their  contraction 
and  pulls  backwards  the  commissures  of  the  lips.  We  doubt  very  much 
whether  it  has,  in  the  cervical  region  at  least,  any  action  on  the  skin,  for  it 
adheres  but  very  slightly  to  its  inner  surface. 

2.  Mastoido-humeralis.     (Figs.  102,  105,  106,  114.) 

Synonyms. — The  muscle  common  to  the  arm,  neck,  and  head — Bourgelat.  Eepre- 
Benting  the  cleido-mastoid,  and  the  clavicular  portions  of  the  trapezius  and  deltoid  of 


'  The  mastoido-humeralis  may  be  dissected  at  the  same  time  as  the  trapezius,  the 
subject  being  placed  in  the  second  position.  This  conveniently  permits  the  superior 
insertions  of  the  muscle  to  be  studied.     (See  fig.  102). 

-  It  wdl  be  seen,  on  referring  to  figure  114  and  its  legend,  that  we  restore  to  the 
cuticular  muscle  of  the  neck  the  sternal  band  attributed  until  now  to  the  mastoido- 
humeralis.  These  arc  the  considerations  wliich  induce  us  to  make  this  modification  : 
I,  This  band  is  not  distinct  from  the  cuticularis  of  the  neck  ;  a  separation  between  the 
two  muscles  can  only  be  artificially  obtained.  2,  In  dissecting  this  band  with  care,  we 
can  see  that  its  fibres,  like  those  of  the  cuticularis,  are  not  mixed  with  those  of  the 
mastoido-humeralis  (superficial  portion)  ;  they  pass  along  the  external  surface  of  that 
muscle,  to  which  they  intimately  adhere,  it  is  true,  but  they  can  easily  be  separated,  and 
are  continuous  with  the  aponeurosis  of  the  first. 


MUSCLES  OF  THE  TBUNK.  197 

Man,  and  the  trachelo-acromialis  peculiar  to  quadruped  mammals' — G.  Cuvier,  '  Lemons 
d'Anatuiiiie  Compare'e,'  2nd  edition.  (This  is  the  muscle  which  Percivall  names  the 
levator  humeri.  The  above  is  the  designation  given  to  it  by  Girard  and  Chauveau. 
Leyh  gives  it  the  same  designation  as  Bourgelat.) 

Extent — Situation — Direction — Composition. — This  muscle  extends  from 
tlie  summit  of  the  head  to  tlie  inferior  part  of  the  arm,  and  is  applied  to  the 
scapulo-humeral  angle  at  the  side  of  the  neck,  in  an  oblique  direction  down- 
wards and  backwards.  it  is  composed  of  two  portions  lying  longitudi- 
nally and  somewhat  intimately  united,  and  distinguished  into  anterior  and 
posterior. 

Form — Structure — Attachments. — A.  The  anterior  or  superficial  portion 
(Fig.  106,  6)  constitutes  a  long  fleshy  band,  which  appears  to  bo  united,  by 
its  anterior  border,  to  the  cuticular  muscle  of  the  neck.  Its  sui)erior 
extremity,  thin  and  wide,  is  attached  to  the  mastoid  process  and  crest  by  an 
ajjoneurosis  (Fig.  102,  7),  which  is  united,  in  front,  to  the  tendon  of  the 
sterno-maxillaris  by  a  very  thin  cellulo-aponeurotic  fascia.  Its  inferior  ex- 
tremity, thicker  than  the  superior,  is  inserted  by  means  of  a  very  short 
aponeurosis  into  the  humerus,  on  the  salient  border  descending  from  the 
deltoid  imprint,  and  which  limits,  in  front,  the  fm-row  of  torsion  on  the 
body  of  that  bone  (Fig.  102,  7). 

B.  The  posterior  or  deep  ptort ion  (Fig.  102,  9)  is  a  second  muscular  band, 
shorter  and  stronger  than  the  preceding.  It  is  attached,  above,  to  the 
transverse  processes  of  the  first  four  cervical  vertebrte  by  as  many  fleshy  bands 
(Fig.  102,  8'),  which  cover  the  superficial  portion.  The  upper  digitation, 
given  ofl:'  to  tnu  atlas,  is  united  to  the  tendon  common  to  the  small  complexus 
and  splenius  (Figs.  105,  9 ;  106,  9',  10,  11).  The  inferior  extremity  of  this 
portion  of  the  muscle  widens  on  the  scapulo-liumeral  angle,  which  it 
envelops  in  becoming  closely  united  to  the  anterior  portion,  terminating 
with  it  on  the  humerus.  An  aponeurosis,  which  is  confounded  with  that  of 
the  trapezius,  and  sends  oif  a  septum  into  the  interstice  between  the  two 
portions  of  the  long  abductor  of  the  arm,  concurs  to  fix  this  extremity  by 
spreading  over  the  muscles  of  the  arm. 

Relations. — It  is  covered,  near  its  mastoid  insertion,  by  the  parotid  gland 
and  the  cervico-auricularis  muscles  ;  for  the  remainder  of  its  extent,  by  the 
aponeurosis  of  the  cuticularis  colli,  from  which  it  is  separated  by  a  thin 
fascia  continuous  with  that  which  extends  over  the  trapezius.  It  covers  the 
splenius,  the  small  comjdexus,  the  oblique  muscles  of  the  head,  subscapulo- 
hyoideus  (to  which  it  adheres  intimately),  the  digastricus,  long  flexor  of  the 
head,  the  angularis,  scalenus,  small  pectoral,  supra-  and  infraspinatus,  the 
long  abductor  of  the  arm,  and  the  coraco-radialis. 

1  At  first  sight  we  might  hesitate  to  admit  that  this  muscle  is  formed  of  such  varied 
and  complicated  elements  as  are  enumerated  above.  Nevertheless,  it  is  a  scientific  fact; 
and  we  will  give  a  demonstration,  as  simple  as  it  is  clear,  that  such  is  the  case — the 
idea  we  owe  to  J.  F.  Meckel.  If  we  take  the  Dog,  for  example,  and  suppose  it  to  be 
possessed  of  a  clavicle  extcndinir  from  the  anterior  extremity  of  the  sternum  to  the 
acromion ;  this  clavicle  would  cnt,  transversely,  the  inferior  portion  of  the  mastoido- 
humeralis,  which  would  thus  be  divided  into  two  portions,  a  superior  ami  an  inferior. 
The  fii  st,  extending  from  the  clavicle  to  the  mastoid  process,  on  this  side,  and  on  the 
other  to  the  mastoid  crest,  as  well  as  to  the  cervical  ligament,  where  it  is  confounded  with 
the  trapezius,  would  exactly  represent  the  clavicular  portion  of  the  latter  muscle,  and 
the  cleidn-masfoideits.  With  resi  ect  to  the  interior  portion,  it  perfectly  resembles,  by  its 
attachments,  the  clavicular  portion  of  the  deltoid.  But,  on  the  contrary,  if  we  suppose 
Man  deprived  of  a  clavicle,  the  three  muscular  fasciculi  indicated,  in  becoming  con- 
founded with  each  other,  would  form  the  mastoido-humeralis  of  the  Dog,  minus  the 
posterior  portion,  or  the  trachelo-acromialis,  which  is  not  reijresented  in  Man. 
16 


198  THE  JIUSCLES. 

Action. — When  the  superior  is  the  fixed  point,  it  carries  the  entire 
anterior  limb  forward.  This  muscle,  therefore,  plays  a  very  important 
part  in  locomotion ;  as  it  is  called  into  action  when  the  animal  raises  the 
fore-limb  in  getting  over  the  groxmd.  If  the  fixed  point  of  the  muscle 
is  the  limb,  it  inclines  the  head  and  neck  to  one  side. 

3.  Sterno-maxillaris.    (Figs.  102,  10;  114,  4.) 
Synonym. — The  sterno-mastoiJeiis  of  IVIan  and  a  large  number  of  the  lower  animals. 

Form — Structure — Situation — Direction — Attachments. — A  long  narrow- 
muscle,  almost  entirely  fleshy,  and  terminated  at  its  upper  extremity  by  a  flat- 
tened tendon ;  situated  in  front  of  the  neck,  beneath  the  cuticularis,  and 
parallel  to  the  anterior  border  of  the  superficial  portion  of  the  mastoido- 
humeralis,  from  which  it  is  separated  by  a  space  that  lodges  the  jugular 
vein ;  attached,  inferiorly,  to  the  cariniform  cartilage  of  the  sternum — fixed 
insertion  ;  and  sui^eriorly — movable  insertion — to  the  curved  portion  of  the 
posterior  border  of  the  maxillary  bone  by  its  terminal  tendon. 

Belations. — The  muscle  is  covered  by  the  cuticularis  colli,  and  the 
parotid  gland.  It  covers  the  trachea,  the  subscapulo-hyoideus,  sterno- 
hyoideus,  sterno-thyroideus,  and  the  maxillary  gland.  Its  external  border, 
parallel  to  the  anterior  border  of  the  mastoido-humeralis,  forms  with  it  a 
longitudinal  depression  termed  the  jugular  furroio,  because  it  lodges  the 
vein  of  that  name.  Its  inner  border  is  intimately  united,  in  its  lower  third, 
to  that  of  the  opposite  muscle. 

Action. — It  directly  flexes  the  head,  when  acting  in  concert  with  its 
congener  ;  but  alone  it  turns  it  to  one  side.  Lafosse  and  Rigot  have  wrongly 
considered  this  muscle  as  a  depressor  of  the  lower  jaw.  Bourgelat  has 
correctly  stated  that  it  cannot  move  this  jaw  independently.  (Percivall  says 
that  the  pair  will  assist  in  opening  the  mouth ;  and  Leyh  asserts  that  when 
the  mouth  is  closed,  each  muscle  will  act  as  a  flexor  to  the  head.) 

4.  Sterno-hyoideus. — 5.  Sterno-thyroideus.     (Fig.  114,  6,  7.) 
(^Synonym. — The  sterno-thyro-hyoideus  of  Percivall.) 

Form — Structure — Situation — Attachments. — Small,  ribbon-shaped,  long, 
and  slender  muscles  ;  digastric  ;  situated  in  front  of  the  trachea  ;  confounded 
at  their  inferior  extremity  and  united  to  those  of  the  opposite  side,  so  as  to 
form  a  single  fasciculus  which  is  attached  to  the  cariniform  cartilage  of  the 
sternum — fixed  insertion  ;  isolated  from  each  other  above  the  tendon  which 
makes  them  digastric,  and  terminating  by  their  superior  extremity — movable 
insertion  :  the  first,  on  the  inferior  surface  of  the  body  of  the  hyoid  bone  in 
common  with  the  subscapulo-hyoideus ;  the  second,  on  the  posterior  border 
of  the  thyroid  cartilage. 

Belations. — Covered  by  the  sterno-maxillaris  and  the  cuticularis  muscle, 
they  cover  the  anterior  face  of  the  trachea. 

Action. — Depressors  of  the  hyoid  bone  and  larynx. 

6.  Omo-hjoideus  or  Suhscapulo-hjoideus.  (Figs.  102,  11;   114,  5.) 
Synonyms, — Hyoideus — Boiirrjelat.     {Subscapulo-hyoideus — Percivall.) 

Form — Structure— Situation — Direction. — This  muscle  forms  a  thin  and 
wide  band,  almost  entirely  fleshy,  oblique  forwards  and  upwards,  extending 
from  the  scapulo- humeral  angle  to  the  intermaxillary  space,  and  applied  to 
the  side  of  the  trachea,  whose  direction  it  slightly  crosses. 


MUSCLES  OF  TEE  TEFXK.  199 

Attachments. — It  derives  its  fixed  insertion  from  the  inner  surface  of  the 
subscixpularis,  by  an  aponeurosis  which  is  detached  from  that  covering  the 
latter  muscle.  Its  movable  insertion  is  into  the  body  of  the  hyoid  bone,  in 
becoming  confounded  vdth.  the  sterno-hyoideus,  and  in  being  intimately 
united  to  the  muscles  of  the  opposite  side. 

Belations. — Outwsirdly,  with  the  subscapularis,  supraspinatus,  small 
pectoral,  mastoido-humeralis^ which  closely  adheres  to  it,  the  jugular  vein, 
the  sterno-maxillaris,  and  the  cuticularis.  Inwardly,  with  the  scalenus,  the 
large  anterior  straight  muscle  of  the  head,  the  main  trunk  of  the  carotid 
artery  and  the  nerves  accompanying  it,  the  trachea,  thyroid  gland,  and  the 
inferior  face  of  the  larynx.  The  jugular  vein  is  entirely  separated  fi-om 
the  carotid  artery  by  this  muscle  in  the  upper  haK  of  the  neck. 

Action. — It  is  a  depressor  of  the  hyoid  bone  and  its  appendages. 

7.  Great  Anterior  Straight  Muscle  of  the  Head.     (Figs.  104  and  105,  10; 

106,  13.) 

Synonyms. — Long  flexor  of  the  hend—Bourgelat.  Trachelo-suboccipitalis — Girard. 
{Bectus  capitis  anticis  major — Percicall.     TracheJo-occlpitalis — Leyh.) 

Form — Structure — Situation — Direction. —  A  long,  flat  muscle,  fescicu- 
lated  in  its  posterior  half,  terminated  in  a  tendinous  cone  at  its  anterioi' 
extremity,  and  passing  along  the  first  cervical  vertebrae  in  front. 

Attachments. — Behind,  to  the  transverse  processes  of  the  third,  fourth, 
and  fifth  cervical  vertebrje  by  as  many  fleshy  digitations,  the  most  inferior 
of  which  are  the  longest — jixed  insertion.  In  front,  into  the  imprints  on  the 
body  of  the  sphenoid  bone  and  the  basilar  process,  by  its  terminal  tendon — 
moiohle  insertion. 

Belations. — Outwardly,  with  the  mastoido-hnmeralis,  the  subscapulo- 
hyoideus,  and  the  small  anterior  straight  muscle.  Inwardly,  with  the  long 
muscle  of  the  neck  and  the  muscle  of  the  opposite  side.  In  front,  with  the 
common  carotid,  the  nerves  accompanying  this  artery,  and  the  guttural 
pouch,  which  lines  it  near  its  movable  insertion.  Behind,  with  the  great 
oblique  muscle  of  the  head  and  the  occipito-atloid  articulation. 

Action. — It  either  directly  flexes  the  head  or  carries  it  to  one  side, 
according  as  it  acts  alone  or  with  its  fellow  of  the  opposite  side. 

8.   Small  Anterior  Straight  Muscle  of  the  Head. 

Synonyms. — Flexor  capitis  brevis — Bourgelat.  AtL  dilo-suboccipitalis — Girard. 
(^Rectus  capitis  anticus  minor — Percivall.     Atloido-occipitalis  inferior — Ltyh.) 

A  small,  entirely  fleshy,  prismatic  fasciculus,  lying  to  the  external  side 
of  the  preceding  muscle  ;  attached,  posteriorly,  to  the  inferior  face  of  the 
body  of  the  atlas  :  in  front,  to  the  body  of  the  sphenoid  heme  and  the  basilar 
process,  beside  the  great  anterior  straight  muscle.  It  is  covered  by  the 
guttural  pouch,  and  covers  the  occipito-atloid  articulation.  It  concurs  in 
flexing  the  head. 

9.  Small  Lateral  Straight  Muscle. 

Synonyms. — Flexor  capitis  parvus — Bourgelat.  Atloido-styloideus — Girard.  'Ohli' 
quus  capitis  anticus — PercivaJt.     The  rectus  capitis  tateralis  of  Man.) 

Yet  smaller  than  the  preceding,  and  prismatic  and  entirely  fleshy,  like  it 
this  muscle  lies  on  the  side  of  the  occipito-atloid  articulation  :  it  is  attached 
to  the  atlas,  outside  the  small  anterior  straight  muscle — fxed  insertion  ;  and 
to  the  inner  face  of  the  styloid  process  of  the  occipital  bone — movable  insertion. 
It  is  the  congener  of  the  two  anterior  straight  muscles  of  the  head. 


200  THE  MUSCLES. 

10.  Scalenus.    (Figs.  104,  105, 106.) 
Synomjms. — Costo-tracheleus — Girard.     (Scalenus  anticus  and  posticus  of  Man.) 

Situation  —  Direction — Composition. — Deeply  situated  at  the  inferior 
part  of  tlae  neck,  in  an  oblique  direction  downwards  and  backwards,  this 
muscle  comprises  two  portions  of  unequal  dimensions,  placed  one  above 
another. 

Form — Structure — Attachments.  —  A.  The  superior  portion  (scalenus  posti- 
cus of  Man),  the  smallest,  is  composed  of  three  or  four  fleshy  fasciculi,  attached 
by  their  extremities  to  the  transverse  processes  of  the  last  three  or  four 
cervical  vertebrte.  The  last  terminates  at  the  superior  extremity  of  the 
first  rib. 

B.  The  inferior  (scalenus  anticus  of  Man),  the  most  considerable,  is 
flattened  on  both  sides,  thick  and  wide  posteriorly,  thin  and  narrow 
anteriorly,  and  is  comj)osed  almost  entirely  of  fleshy  fibres  which  are  longest 
as  they  are  inferior.  It  is  attached  :  1 ,  To  the  transverse  processes  of  the 
last  four  cervical  vertebrae  by  short  fasciculi  scarcely  distinct  from  one 
another,  the  first  of  which  is  crossed  by  the  last  digitation  of  the  great 
anterior  straight  muscle ;  2,  To  the  anterior  border  and  external  face  of  the 
first  rib,  where  all  its  fibres  end. 

Belations. — The  scalenus  responds :  by  its  external  face,  to  the  sub- 
scapulo-hyoideus,  raastoido-humeralis,  and  the  sterno-i>rescapularis ;  by  its 
internal  face,  to  the  longus  colli,  trachea,  common  carotid  artery  and  its 
accompanying  nerves,  and — on  the  left  side  only — to  the  oesophagus ;  by  its 
inferior  border,  to  the  jugular  vein.  The  two  portions  of  the  scalenus  are 
separated  from  one  another,  in  front  of  the  first  rib,  by  an  interspace 
traversed  by  the  nerves  of  the  brachial  plexus. 

Action. — When  the  first  rib  is  the  fixed  point,  this  muscle  either  directly 
flexes  the  neck  or  inclines  it  to  one  side.  When  the  neck  is  the  fixed  point, 
it  draws  forward  the  first  rib  and  fixes  it  in  this  position  during  the 
dilatation  of  the  chest,  in  order  to  aid  the  inspiratory  action  of  the  external 
intercostal  muscles. 

11.  Long  Muscle  of  the  NecJc. 

Symnyms.— Flexor  longus  colli — Bourgelat.  Subdorso-atloideus — Girard.  {Longus 
colli — Percivall.    Dorso-atloideus — Leyh.) 

Situation — Composition. — A  single  and  considerable  muscle,  immediately 
covering  the  inferior  aspect  of  all  the  cervical  and  the  first  six  dorsal 
vertebra3,  and  composed  of  two  lateral  portions  which  are  united  on  the 
median  line,  and  constitute,  in  certain  animals,  two  distinct  muscles. 

Structure — Attachments.— 'Each,  lateral  portion  of  the  longus  colli  is 
composed  of  a  succession  of  very  tendinous  fasciculi.  The  most  posterior  of 
these  is  attached  to  the  inferior  face  of  the  bodies  of  the  first  six  dorsal 
vertebrte,  and  proceeds  directly  forward  to  reach  the  inferior  tubercle  of  the 
sixth  cervical  vertebra,  into* which  it  is  inserted  by  a  strong  tendon.  The 
other  fasciculi,  less  considerable,  and  confounded  outwardly  with  the  inter- 
transversales  of  the  neck,  are  carried  from  one  cervical  vertebra  to  another, 
and  are  directed  forwards,  upwards,  and  inwards,  in  convei'ging  towards  those 
of  the  ojjposite  side.  They  are  attached  successively  :  outwardly,  to  the 
transverse  processes  of  the  last  six  cervical  vertebrae;  inwardly,  to  the 
inferior  ridge  on  the  bodies  of  the  first  six.  The  most  anterior  fasciculus 
passes  to  the  inferior  tubercle  of  the  atlas,  into  which  it  is  inserted  by  a 


MUSCLES  OF  THE  TRUNK.  201 

tendon  common  to  it  and  the  fasciculus  of  the  opposite  side,  and  which 
receives  the  most  supcrliciul  libres  of  the  three  or  four  preceding  fasciculi. 

Relations. — Above  and  behind,  with  the  vertebras  which  it  covers,  ag 
well  as  their  intervertebral  discs ;  below  and  iu  front,  with  the  trachea 
and  cesoi)hagus,  and  the  vessels  and  nerves  accompauying  those  two  tubes ; 
on  the  sides,  with  the  great  anterior  straight  and  the  scalenus  muscles  in  its 
cervical  portion,  and  in  its  intrathoracic  portion,  with  the  pleurfe,  and 
important  vessels  and  nerves. 

Action. — It  flexes  the  whole  neck,  and  the  cervical  vertebrae  on  one 
another. 

DIFFERENTIAL  CHABACTEBS  OF   THE   MUSCLES   OF   THE  CERVICAL    REGION   IN    OTHER    THAN 

SOLIPED   ANIMALS. 

A.  Superior  Cervical  Region. 

1.  RuJiiNANTS. — In  the  Ox,  the  angularis  arises  by  six  digitations  from  all  the  cervical 
vertebrffi  except  the  first ;  the  splenius  is  little  developed,  and  is  not  attached  to  either 
the  third  or  fourth  cervical  vertebra. 

2.  Pig. — The  muscles  of  the  superior  cervical  region  in  tliis  animal  are  generally 
very  developed.  The  rltomboideus  is  divided  into  two  fleshy  bodies,  one  of  which  proceeds 
to  the  occipital  protuberance,  and  the  other  to  the  rudimentary  cervical  ligament  and 
the  first  dorsal  vertebrae.  The  angularis  is  attached,  as  in  Ruminants,  to  tlie  six  cervical 
vertebrae  ;  sometimes  it  even  shows  a  digitation  that  descends  to  the  atlas.  The  s2Aenius 
only  terminates  anteriorly  by  three  fleshy  bodies;  but  they  are  voluminous,  and  are 
inserted,  one  into  the  atla.s,  another  into  tlie  mastoid  crest,  and  the  third  into  the  occipital 
protuberance.  In  the  great  complexus,  tlie  two  jDortions  are  completely  separated  from 
each  other,  except  at  their  upper  extremity,  by  the  interspace  lodging  the  superior 
cervical  artery.  The  aponeurosis  attaching  the  muscle  to  the  spinous  processes  of  the 
first  dorsal  vertebrae  is  not  confoumled  with  that  of  the  splenius  or  the  small  anterior 
serrated  respiratory  muscle.  The  atloidean  fleshy  body  of  the  small  complexus  is  scarcely 
distinct  from  the  superior  branch  of  the  ilio-spinalis  and  the  intertransver.-ales.  Lastly, 
it  is  diflicult  to  distinguish  the  small  poderior  straight  muscle  from  the  deep  fasciculus 
of  the  great  straight  muscle. 

3.  Carnivora. — In  these  animals  the  muscles  of  the  superior  cervical  region  are 
nearly  all  voluminous,  as  in  the  Pig.  The  rhomhoideus  is  bifid  at  its  origin,  and  its 
anterior  branch  arises  from  the  mastoid  crest.  The  angularis  is  also  attached  to  the  la^t 
six  cervical  vertebrae.  Very  thick  and  bnad,  the  splenius  only  passes  to  the  atlas  and 
mastoid  crest.  The  oblique  and  straight  posterior  muscles  of  the  head  are  also  remarkably 
thick. 

B.  Inferior  Cervical  or  Trachelian  Region. 

1.  EuMiNANTS — In  the  Ox  and  Sheep,  the  disposition  of  the  cuticularis  colli  offers  a 
very  considerable  difterenco  from  that  observed  in  Solipeds.  The  fleshy  portion  is 
absent,  or  appears  to  be  absent,  in  the  cervical  region ;  the  anterior  muscles  of  the  neck 
are  only  covered  by  a  thin  fascia  developed  on  the  sides  of  the  neck.  "When  this 
fascia  reaches  the  face,  it  becomes  continuous  with  the  fleshy  fibres;  a  fasciculus  of 
these  fibres  comports  itself  as  in  the  Horse,  and  goes  to  join  the  alveo-labialis;  an  ither 
is  intercrossed  in  the  maxillary  space  by  the  analogous  fasciculus  of  the  opposite 
side. 

The  cervical  cuticularis  muscle  of  the  Ox  is  also  distinguished  by  an  extremely 
remarliable  peculiarity  which  it  is  necessary  to  allude  to  here  : — The  fleshy  cervical  ban(l, 
altogether  absent  in  the  Sheep,  is  not  so  in  the  Ox ;  we  have  found  it  forming,  beneath 
the  above-mentioned  aponeurotic  fascia,  the  long,  thick  strip  which  has  been  described 
by  veterinary  anatomists  ao  the  analogue  of  the  sterno-maxillaris  in  the  Horse.  1  his 
strip  is  attached,  like  the  muscular  band  Avhich  represents  it  in  Solipeds,  to  the  anterior 
point  of  the  sternum.  But  its  fibres,  instead  of  being  spread  outwards  over  the  mastoido- 
humeralis,  ascend,  perfectly  isolated  from  that  muscle,  to  the  posterior  border  of  the 
maxillaris.  There  it  terminates  (Fig.  112, 18 )  by  a  flattened  tendon  which,  after  reaching 
the  anterior  lionler  of  tlie  massetsr,  is  confounded  with  the  aponeurosis  of  that  muscle, 
and  sends  some  fibrous  bands  over  the  muscles  of  the  face. 

The  two  portions  of  the  ma4nid(i-humeralis  of  Ruminants  are  better  defined,  and  more 
oblique  on  one  another,  than  iu  the  Horse.    The  superficial  portion  receives  on  its  iuuer 


202  TEE  3IUSCLES. 

fa«e  a  small,  bright-red,  fimicniar  fasciculus,  which  proceeds  from  tlie  cartilage  of  the 
first  rib,  and  which  Meckel  is  inclined  to  consider  as  tiie  vestige  of  the  subclavius.  It 
is  divided,  superiorly,  into  two  branches :  one,  the  clavicular  portion  of  the  traptzius, 
very  wide,  passes  to  the  mastoid  process,  the  curved  line  of  the  occipital  bone,  and  to  the 
cervical  ligament,  in  becoming  confounded  with  the  trapezium  (Fig.  112,  22);  the  otiier, 
the  cleido-mastoideus,  terminates  in  a  tendon  that  joins  the  sterno-suboccipitalis,  and  la 
inserted  into  the  basilar  process,  after  receiving  the  fibres  of  tlie  long  flexor  of  the  head 
(Fif.  112,21).  The  upper  extremity  of  tlie  deep  portion  of  the  mastoido-humeralis  is 
insCTted  into  the  atlas  by  a  flattened  tendon  alone,  which  is  quite  distinct  from  the  atloid 
insertions  of  the  splenius  and  the  small  complexus. 

In  the  Sheep  aiid  Goat,  tiie  costal  band  that  joins  the  superficial  portion  is  absent. 
The  latter  is  divided  at  its  inferior  extremity  into  two  branches,  between  which  pass  the 
biceps.     The  upper  branch  passes  to  the  epitrochlea. 

The  sterno-maxillury  muscle,  instead  of  heing  inserted  into  the  inferior  maxilla,  is 
united  to  the  suboccipital  branch  of  the  mastoido-humeralis,  to  be  attached  to  the  l>asilar 
process.  At  another  time  we  will  discuss  the  determination  of  this  muscle,  and  that  of 
the  fleshy  bund  here  considered  as  belonging  to  the  first  (see  Spinal  Nerve). 

The  sterno-hyoid  and  sterna-thyroid  muscles  are  thicker  than  in  the  Horse,  and  not 
digastric. 

The  sid)scapulo-hyoideus  of  Ruminants  is  but  slightly  developed,  and  might  be  termed 
the  trachelu-hyoideiis ;  as  it  proceeds  to  the  transverse  process  of  the  third  or  fourth 
cervical  vertebra.  In  its  passage  beneath  the  basilar  branch  of  the  mastoido-humeralis 
and  sterno-suboccipitalis  (sterno-maxillaris),  it  contracts  adhesions  with  the  fibres  of  these 
two  muscles. 

Tiie  great  anterior  straight  muscle  of  the  head  descends  to  the  sixth  cervical  vertebra. 
Its  cervical  insertions  are  covered  by  a  very  strong  muscular  fasciculus,  which  is  annexed 
to  it.  Like  it,  this  fasciculus  leaves  the  sixth  cervical  vertebra,  and  is  attached  to  tlie 
transverse  processes  of  the  four  vertebrse  preceding  the  last,  by  becoming  confounded 
with  the  intertransversales,  and  finally  terminating  at  the  tracheal  process  of  the  atlas  by 
fleshy  and  aponeurotic  fibres.  This  muscular  fasciculus  singularly  strengthens  tlie  neck 
when  it  is  inclined  to  one  side.  In  consequence  of  its  attachments,  it  might  be  named  the 
trachelo-atloideus  (Fig.  112,  24). 

Lastly,  in  Ruminants  the  superior  scalenus  is  very  developed,  being  a  flattened  band 
which,  gradually  expanding,  is  prolonge  1  to  the  surface  of  the  serratus  magnus. 

2.  Pig. — In  this  animal,  the  cuticularis  colli  is  in  two  portions :  an  inferior,  which 
comes  from  the  point  of  the  sternum ;  and  a  superior,  from  the  external  scapular  region. 
They  unite  in  front,  and  are  prolonged  in  common  on  the  muscles  of  the  face,  con- 
tracting adhesions  with  the  external  aspect  of  the  body  and  the  branches  of  the  maxillary 
bone. 

The  other  muscles  of  the  inferior  cervical  region  are  not  unlike  those  of  Ruminants. 

Of  the  two  portions  of  the  uiastoido-humeralis,  the  superficial  is  bifid  at  its  superior 
extremity.  The  posterior  branch,  the  clavicular  portion  of  the  trapezius,  is  attacheil  to 
the  side  of  the  occipital  protuberance ;  the  anterior  branch,  the  cleido-mastoideus,  goes 
beneath  the  external  auditory  hiatus,  to  the  crest  that  replaces  the  mastoid  process ;  the 
deep  portion  is  attached  above  to  the  atlas  only. 

In  the  Pig,  the  sterno-maxillaris  exactly  represents  the  sterno-mastoideus,  as  its 
tendon  passes  directly  to  the  mastoid  process. 

'i'he  sterno-thyroideus  is  double ;  the  supjjlementary  branch  going  to  the  inferior  face 
of  the  thyroideus. 

The  siihscapulo-hyoideus  and  great  anterior  straight  muscle  of  the  head,  resemble  those 
of  the  Ox.  The  small  straight  lateral  muscle  is  scarcely  distinct  from  the  small  oblique. 
The  superior  scalenus  extends  to  the  third  rib.  The  two  lateral  portions  of  the  long 
muscU  of  the  neck  are  separate,  and  form  two  distinct  muscles. 

3.  Cabmvora. — In  the  Dog,  each  cuticularis  is  doubled  into  two  portions,  as  in  the 
Pig.  The  fibres  from  the  breast  are  directed  in  a  diverging  manner  over  the  face,  the  sub- 
maxillary space,  and  the  parotid  gland,  where  they  form  the  parotido-auricularis  muscle. 
The  portion  coming  from  the  external  scapular  region  is  thicker  and  wider;  it  covers 
the  lateral  parts  of  the  neck,  the  parotid  gland,  the  parotido-auricularis,  passes  above  the 
preceding,  and  terminates  on  the  face  and  in  the  submaxillary  space,  where  its  fibres 
join  those  of  the  opposite  side. 

The  mastoido-humeralis  comports  itself  somewhat  as  in  Ruminants  and  the  Pig.  The 
superficial  portion  is  bifid  superiorly ;  one  of  its  branches  is  fixed  into  the  mastoid  process — 
the  cleido-mastoideus  ;  the  other  into  the  mastoid  crest  and  cervical  ligament,  in  uniting 
by  aponeurosis  with  the  trapezius — the  clavicular  portion  of  the  trapezius.  The  deep 
portion  passes  from  the  atlas  to  the  scapular  spine. 


MUSCLES  OF  THE  TRUNK.  203 

The  tendon  of  the  sterno-maxillaris  goes  to  the  mastoid  process.  The  sterno-hi/oideus 
and  thyroideiis  are  thick  and  not  digastric,  and  commence  from  the  cartilage  of  the  first 
rib. 

The  Carnivora  have  no  subscapulo-hi/oideus ;  but  they  possess  a  very  long  scalenus, 
which  passes  to  the  cightli  rib,  and  a  long  muscle  of  the  neck,  which  tends  to  become 
divided  into  two  lateral  portions. 

SPINAL    REGION    OP    THE   BACK    AND    LOINS. 

This  offers  for  study  eight  pairs  of  muscles,  nearly  all  of  which  have 
their  insertions  extended  over  the  dorso-lurabar  spine,  and  are  disposed  in 
Beveral  layers  on  each  side  of  this  long  multitidious  crest.  These  muscles 
are,  enumerating  them  according  to  their  order  of  superposition :  1,  The 
trapezius ;  2,  Great  dorsal ;  3,  Small  anterior  respiratory  serratus ;  4,  Small 
posterior  serratus;  5,  Ilio-spinalis  (longissimus  dorsi)  ;  6,  Common  intercostal; 
7,  Transver sales  of  the  hack  and  loins  {semispinalis  doisi  and  lumhorum). 

Preparation. — 1.  Place  the  animal  in  the  second  position.  2.  Remove  the  skin 
with  the  panniculus  and  tlie  mass  of  olecranian  muscles,  to  show,  in  a  first  operation,  the 
trapezius  and  great  dorsal  muscles  (Fig.  102).  3.  In  a  second  operation,  remove  tlie 
entire  fore-limb,  with  the  great  dorsal  muscle,  whose  mode  of  termination  may  then  be 
studied ;  then  prepare  the  two  small  serrated  muscles.  4.  Remove  these  two  muscles,  as 
well  as  the  angularis  of  the  sfapula  and  the  splenius,  to  expose  the  common  intercostal 
and  ilio-spinalis  (Fig.  1 06).  The  superior  branch  of  tlie  latter  remaining  covered  by  the 
great  complexus,  excise  tliis  muscle,  leaving  only  its  insertions  into  the  transverse 
processes  of  the  dorsal  vertebra},  to  show  liow  tliey  are  fixed  between  the  two  branches 
of  the  ilio-spinalis  (longissimus  dorsi).  5.  Dissect  the  transversales  (semispinalis)  by 
removing  the  ilio-spinalis  and  the  internal  angle  of  the  ilium. 

1.  Trapezius.     (Fig.  102,  1,  3.) 
Synonym. — Dorso-  and  cervico-acromialis — Girard. 

Situation — Form — Structure. — This  is  a  superficial  membranous  muscle, 
situated  on  the  sides  of  the  neck  and  withers.  Its  shape  is  that  of  a  triangle 
whose  base  is  ujjwards.  It  is  aponeurotic  at  its  upper  border  and  in  its 
centre,  which  allows  it  to  be  distinguished,  especially  in  emaciated  subjects, 
into  a  cervical  and  a  dorsal  portion.  The  fleshy  fibres  of  the  first  are 
du-ected  downwards  and  backwards;  those  of  the  second  are  oblique 
forwards. 

Attachments. — By  its  superior  aponeurosis,  it  is  fixed  to  the  cervical  cord 
and  to  the  siunmits  of  the  transverse  ijrocesses  of  the  first  dorsal  vertebrfe, 
where  it  adheres  to  the  external  face  of  the  great  dorsal  muscle.  By 
its  central  aponeurosis  and  that  of  its  summit,  it  is  attached  to  the  tuberosity 
of  the  olecranian  spine  and  the  external  scapular  aponeurosis. 

Melalions. — This  muscle  is  covered  by  two  aponeurotic  planes,  whose 
fibres  cross  its  own  at  a  right  angle.  Inwardly,  it  responds  to  the  rhom- 
boideus,  splenius,  angularis,  steruo-prescapularis,  the  supra-  and  infra- 
S2)inatus,  and  the  great  dorsal. 

Action. — It  raises  the  shoulder,  and  carries  it  forward  or  backward, 
according  as  one  or  other  of  its  muscular  portions  contract. 

2.  Ch-eat  Dorsal.     (Fig.  102,  2.) 
Synonyms. — Dorso-himieralis —  Girard.    (Latissimue  dorsi — Percivall.) 

Form — Situation — Structure — Attachments. — A  very  broad  triangular 
muscle,  extended  over  the  loins,  back,  and  side  of  the  thorax,  and  formed  of 
an  aponeurotic  and  a  muscular  portion. 

The  aponeurosis  is  attached,  by  its  superior  border,  to   the   summits 


204 


THE  MUSCLES. 


of  the  spinous  processes  of  all  the  lumbar  and  the  last  fourteen  or  fifteen 
dorsal  vertebrse — fixed  insertion  of  the  muscle. 

The  fibres  of  the  fleshy  portion  are  detached  from  the  inferior  border 
of  the  aponeurosis,  at  the  twelth  or  thirteenth  ribs,  to  the  cartilage  of 
the  scapula.  They  are  directed  forwards  and  downwards,  and  all  converge 
into  a  flat  tendon  which  is  inserted  into  the  internal  tuberosity  on  the 
body  of  the  humerus — movable  insertion.  This  tendon  is  remarkable,  at  its 
termination,  for  being  placed  at  the  external  face  of  the  teres  magnus  or 
adductor  of  the  arm,  from  which  it  receives  fibres,  and  between  it  and  the 
long  extensor  of  the  fore-arm ;  it  then  turns  inwards,  on  the  inferior 
extremity  of  the  first,  in  such  a  manner  that  this  extremity  is  comprised 

Fig.  105. 


MUSCLES  OF   THE   SPINAL   REGION   OF   THE   NECK,    EACK,   AND   LOINS,   MIDDLE   LAYER; 
AND   OF    THE    COSTAL    AND    ABDOMINAL   REGION,    SUPERFICIAL   LAYER. 

1,  2,  Rhomboideus  ;  3,  Angular  muscle  of  the  scapula ;  4,  Splenitis  ;  5,  Its  mastoid 
aponeurosis;  6,  Mastoid  portion  of  the  small  complexus;  7,  Its  tendon;  8,  Cer- 
vical insertions  of  the  mastoido-humeralis  ;  9,  Atloidean  tendon  common  to  the 
mastoido-humeralis,  splenius,  and  small  complexus;  10,  Great  anterior  straight 
muscle  of  the  head;  11,  Inferior  scalenus;  12,  Superior  scalenus;  13,  Small 
anterior  serratus ;  14,  Posterior  ditto;  15,  Great  serratus;  16,  Transverse 
muscle  of  the  ribs;  17,  One  of  the  external  intercostals ;  18,  Great  oblique 
muscle  of  the  abdomen;  20,  Straight  muscle  of  the  abdomen;  21,  Stylo-maxil- 
lary portion  of  the  digastric  muscle. 

within  a  duplicature  of  the  membranous  tendon   of  the   latissimus   dorsi 
(Fig.  121). 

Belations. — This  muscle  is  covered  by  the  skin,  panniculus  carnosus, 
dorsal  portion  of  the  trapezius,  and  the  mass  of  olecranian  muscles.  It 
covers  the  infraspinatus ;  the  cartilage  of  the  scapula ;  the  rhomboideus ; 
the  small  anterior  and  posterior  serrated  muscles,  whose  aponeurosis  is 
directly  joined  to  its  own ;  the  ilio-spinalis ;  the  principal  gluteal ;  a  portion 
of  the'  external  surface  of  the  last  ribs,  to  which  its  aponeurosis  strongly 
adheres ;  as  well  as  the  corresponding  external  intercostals,  and  the  great 
serrated  muscle.     Between  the  last  rib  and  the  external  angle  of  the  ilium, 


MUSCLES  OF  TEE  TRUNK.  205 

the  ajioneurosis  unites  with  the  small  obliiiue,  but  more  particularly  with 
the  great  oblique,  muscle  of  the  abdomen  ;  it  is  prolonged,  posteriorly,  on 
the  muscles  of  the  croup  to  constitute  the  gluteal  aponeurosis. 

Action. — It  carries  the  arm  backwards  and  ujiwards ;  and  it  may, 
r.ccordiug  to  a  great  number  of  authors,  serve  as  an  auxiliary  in  insj^iration 
when  its  uxcd  point  is  the  liumcrus.  According  to  others,  but  in  whose 
opinion  we  do  not  share,  it  is  an  expiratory  muscle. 

3,  Small  Anterior  Serrated  Muscle.    (Fig.  105,  13.) 

Synonyms. — Dorso-costalis — Girard.  Anterior  portion  of  the  long  serrated  muscle 
— Bvunjelat..  (^Supcrjjcialis  costarum — Percivall.  Anterior  serrated  muscle  of  Leyh. 
Serratus  posticus  superior  of  Man.) 

Form — Situation. — This  is  a  flat,  thin,  and  quadrilateral  muscle,  situated 
beneath  the  rhomboideus  and  the  great  dorsal  muscle. 

Structure. — It  is  composed  of  an  aponeurotic  and  a  fleshy  portion.  The 
first  is  confounded,  in  front,  with  the  aponeurosis  of  the  sjjlenius,  and  is 
insinuated,  behind,  underneatb  that  of  the  posterior  small  serratus,  with 
which  it  soon  becomes  imited.  Its  inferior  border  gives  origin  to  the  muscular 
portion,  a  little  above  the  interval  which  separates  the  common  intercostal 
and  the  ilio-sjDinalis.  Narrow  and  elongated  antero-posteriorly,  the  muscular 
portion  is  composed  of  bright-red  fibres  directed  obliquely  backwards  and 
downwards,  and  which  form  at  the  inferior  border  irregular,  and  sometimes 
but  faintly  marked,  festoons. 

Attachments. — It  takes  its  fixed  insertion,  by  the  superior  border  of  its 
aponeurosis,  from  the  summits  of  the  anterior  dorsal  spines,  with  the 
exception  of  the  first,  to  the  thirteenth  inclusive.  The  movable  insertion 
takes  place  on  the  external  surface  and  anterior  border  of  the  nine  ribs 
succeeding  the  fourth,  by  means  of  the  digitations  of  the  fleshy  portion. 
This  muscle  is  also  attached  to  the  external  surface  of  these  ribs  by  a  short 
fibrous  band,  which,  is  detached  from  the  internal  face  of  the  aponeurosis, 
near  its  inferior  border,  and  penetrates  the  space  between  the  ilio-spinalis 
and  the  common  intercostal  muscle. 

Relations. — Outwards,  with  the  rhomboideus,  great  serratus,  gi"eat  dorsal, 
and  the  posterior  small  serratus,  which  covers  its  three  last  festoons ; 
inwards,  with  the  ilio-spinalis,  the  common  intercostal,  and  the  external 
intercostals. 

Action. — This  is  an  inspiratory  muscle,  and  it  also  serves  as  a  check  to 
the  deep  spinal  muscles. 

4.  Small  Posterior  Serrated  3Iuscle.     (Fig  105,  14.) 

Synonyms. — Lumbo-costalis — Girard.  Posterior  portion  of  the  long  serrated  muscle 
— Bourgelat.  {Superficial is  costarum — Fercivall.  The  posterior  serrated  muscle  of  Leyh. 
The  serratus  posticus  inferior  of  Man.) 

Situation. — Situated  behind  the  preceding,  which  it  follows,  and  jiresent- 
ing  the  same  form  and  arrangement,  this  muscle  also  offers  the  following 
particular  features  for  study  : 

1.  Structure.— Its  muscular  portion,  which  is  thicker  and  of  a  deep-red 
colour,  is  cut  into  nine  well-defined  digitations.^  The  fibres  which  compose 
it  run  in  an  almost  vertical  direction. 

2.  Attachments. — Its  aponeurosis,  closely  united  to  that  of  the  gi-eat  dorsal 
muscle,  which  covers  it,  is  attached  to  the  spinous  processes  of  the  dorsal 

*  It  frequently  happens  that  only  eight  digitations  are  found. 


206  THE  MUSCLES. 

vertebrfe  after   tlie  tenth,  and  to  some  lumbar  vertebrae.     Its  digitations 
are  fixed  to  the  posterior  border  and  external  face  of  the  nine  last  ribs. 

3.  Relations.  — Outwards,  with  the  great  dorsal ;  inwards,  with  the 
small  anterior  serratus,  the  ilio-si)iualis,  common  intercostal,  and  the 
external  intercostals.  Some  of  its  posterior  digitations  are  partly  con- 
cealed by  those  of  the  great  oblique  muscle  of  the  abdomen;  the  last, 
indeed,  is  entirely  covered  by  that  muscle. 

4.  Action. — This  is  an  expiratory  muscle,  in  consequence  of  its  drawing 
the  ribs  backwards  and  upwards, 

5.  The  Uio-spinalis  Muscle.     (Fig.  106.) 

Synonyms. — It  represents  the  long  dorsal,  short  transversal,  and  long  spinous  of 
Bourgelat.  Cuvier  and  others  have  described  it  as  consisting  generally,  in  mammalia, 
of  live  particular  muscles,  designated  as  longissimus  dorsi,  transversalis  cervicis,  semi- 
spiiialis  dorsi,  and  semispinalis  colli.  It  corresponds  to  the  longissimus  dorsi,  and  trans- 
versalis cervicis  of  Man. 

(Percivall  designates  this  important  muscle  the  longissimus-dorsi — the  name  given  to 
its  analogue  in  Man.     By  Girard,  Leyh,  and  Chauveau,  it  is  styled  the  ilio-spinalis.) 

Extent — Situation. — This,  the  most  powerful  and  complex  of  all  the 
muscles  in  the  body,  extends  along  the  dorso-lumbar  spine,  above  the 
costal  arches,  from  the  anterior  border  of  the  ilium  to  the  middle  of  the 
cervical  stalk. 

Form. — It  is  elongated  from  before  to  behind,  and  flattened  above 
and  below  in  its  posterior  half,  which  rei)resents  the  common  mass  in  Man  ; 
this  mass  is  prismatic  in  form,  thick  inwards,  and  thin  outwards.  Anteriorly, 
it  is  flat  on  both  sides,  and  bifurcates  into  two  voluminous  branches,  a 
superior  and  inferior,  between  which  pass  the  insertions  of  the  complexus 
to  be  fixed  into  the  transverse  processes  of  the  first  dorsal  vertebras. 

Attachments. — 1,  Uj)on  the  lumbar  border,  the  external  angle  and 
internal  surface  of  the  ilium,  the  sacro-iliac  ligament,  and  the  sacrum ; 
2,  To  the  spinous  processes  of  all  the  lumbar  and  dorsal,  and  last  four 
cervical  vertebrje  ;  3,  To  the  articular  tubercles  of  the  lumbar  vertebrae  and 
the  transverse  processes  of  all  the  dorsal,  and  the  last  fom-  cervical  vertebrte  ; 
4,  To  the  costiform  processes  of  the  lumbar  vertebrae,  and  the  external 
surface  of  the  fifteen  or  sixteen  last  ribs. 

Structure. — If  this  muscle  is  examined  posteriorly,  in  the  part  which 
forms  the  common  mass,  it  will  be  found  to  be  composed  of  very  compact 
fleshy  fibres,  covered  in  common  by  a  thick  ajjoneurosis.  Tliese  fibres 
commence  at  the  jjosterior  extremity  of  the  muscle,  and  all  proceed  forward, 
stopping  to  take  successive  insertions  on  the  various  bony  eminences 
in  its  track,  and  forming  three  different  orders  of  fasciculi,  which  are 
more  or  less  tendinous  at  their  anterior  or  terminal  extremity.  These 
fasciculi  are  internal  and  .supei-ficial,  internal  and  dcei),  and  external. 

The  internal  and  superficial,  or  spinal  fasciculi,  pass  to  the  summits  of 
the  spinous  jirocesses  already  noticed  when  speaking  of  the  attachments. 
These  fasciculi  are  little,  if  at  all  distinct  posteriorly  ;  but  they  become 
more  so  anteriorly.  About  the  sixth  dorsal  vertebra,  they  separate  from 
the  other  fasciculi  to  form  the  superior  branch  of  the  muscle  (Fig.  106,  3). 

The  internal  and  profound,  or  transverse  fasciculi,  are  those  which  attach 
the  muscle  to  the  articular  tubercles  of  the  lumbar  vertebrfe  and  transverse 
processes  of  the  back  and  neck.  They  are  well  detached  from  each 
other,  even  posteriorly,  and  are  very  tendinous.  Anteriorly,  they  pass 
into  the  inferior  branch  of  the  ilio-spinalis,  which  they,  in  common  with 


MUSCLES  OF  THE  TRUNK. 


207 


Fis.  106, 


1,  2,  3,  4,  Ilio-spinalis ;  5,  Com- 
mon intercostal ;  6,  Principal 
portion  of  the  great  complexus ; 

7,  Anterior  portion  of  the  same  ; 

8,  Mastoid  tascicnlus  of  the 
small  complexus;  8',  Its  ten- 
don ;  9,  Atloid  fasciculus  of  that 
muscle;  9',  Its  tendon;  10.  At- 
loid insertion  of  the  splenius 
turned  forward;  11,  Ditto  of 
the  mastoido-humeralis ;  12, 
Intertransversales  of  the  neck  ; 
13.  Long  tlexorofthe  head;  14, 
Inferior  scalenus;  15,  Superior 
scalenus ;  16,  Internal  inter- 
costals;  1",  Dependent  fasci- 
culus of  the  small  oblique,  form- 
ing the  retractor  of  the  last  rib, 
according  to  German  anatom- 
ists; 17'.  Small  oblique  muscle 
of  the  abdomen  ;  18,  Transverse 
muscle  of  the  abdomen. 


DEEP  MUSCLES  OF   THE   SPIXAL   REGION   OF   THE   XECK,   BACK,    A>"D   LOIXS,   AXD 
THE   COSTAL   A>"D   I>"FEF.IOB   ABD03IIXAL   EEGI0X3. 


20S  TEE  MUSCLES. 

tlie  external  fasciculi,  go  to  form.  From  profound,  they  now  become 
superficial ;  and  they  are  seen  springing  up  between  the  others,  which 
appear  to  separate  to  allow  them  to  pass  (Fig.  106,  4,  4). 

The  external,  or  costal  fasciculi,  turn  a  little  outwards  to  reach  the  ribs 
and  costiform  processes  of  the  lumbar  region  ;  they  are  not  very  apparent 
in  this  direction  (Fig  106,  2,  2). 

It  will  be  easily  understood  that  all  these  fasciculi  do  not  come  from 
the  common  mass,  which  would  be  expended  long  before  its  termination  at 
the  neck,  in  consequence  of  the  successive  emissions  of  the  fasciculi 
composing  it.  To  prevent  this  expenditure,  there  are  continually  added  to 
it  numerous  reinforcing  bundles  of  fibres,  which  arise  either  from  its 
aponeurotic  envelope,  or  from  the  bones  on  which  the  primary  fasciculi 
terminate,  and  comport  themselves  absolutely  like  these,  which  they  are 
charged  to  continue  to  the  neck. 

Belations. — The  ilio-spinalis  is  covered  by  the  pyramidal  point  of  the 
principal  gluteal  muscle,  which  it  receives  in  a  particular  excavation,  and  by 
the  aponeurosis  of  the  great  dorsal  and  the  small  serrated  muscles.  It 
covers  the  intertransversales  of  the  himbar  region,  the  transversales  of  the 
back  and  loins,  the  supercostals  (levatores  costarum)  and  the  external 
intercostals.     Outwards,  it  is  bordered  by  the  common  intercostal. 

The  superior  branch  is  covered  by  the  great  complexus  and  the  trans- 
versales colli.  Inwardly,  it  responds  to  the  cervical  ligament  and  the  analo- 
gous branch  of  the  opposite  muscle. 

The  inferior  branch  responds,  outwardly,  to  the  angularis  of  the  scapula ; 
it  covers  some  intertransversales  colli,  and  the  aponeurotic  digitations  which 
attach  the  great  complexus  to  the  transverse  processes  of  the  first  dorsal 
vertehrae.  From  these  digitations  it  even  detaches  a  number  of  muscular 
fasciculi,  which  go  to  strengthen  this  branch  of  the  ilio-spinalis. 

Action. — It  is  a  powerful  extensor  of  the  vertebral  column,  which,  when 
it  acts  singly,  it  inclines  to  one  side.     It  may  also  take  part  in  expiration. 


6.  Common  Intercostal  Muscle.     (Fig.  106,  5.) 

Synonyms. — Trachelo-costalis — Girard,  The  sacro-luvibalis  of  Man.  {Transrersalis 
costarum — Percivall.) 

Form — Situation. — A  long,  narrow,  and  thin  muscle — particularly  at  its 
extremities — situated  along  the  external  border  of  the  preceding  muscle, 
with  which  it  is  confounded  behind  the  last  rib. 

Structure — Attachments. — This  muscle,  whose  structure  has  been  com- 
plicated at  will  by  so  many  anatomists,  is  yet  extremely  simple.  It  is  formed 
of  a  series  of  fasciculi,  directed  obliquely  forwards,  downwards,  and  out- 
wards, tendinous  at  their  extremities,  and  originating  and  ternruating 
successively  on  tlie  external  surface  of  the  ribs.  The  most  posterior  leave 
the  external  border  and  inferior  face  of  the  common  mass.  The  tendinous 
digitation  of  the  anterior  fasciculus  is  inserted  into  the  transverse  process 
of  the  last  cervical  vertebra,  in  common  with  the  inferior  branch  of  the  ilio- 
spinalis. 

Belations. — Outwards,  with  the  great  and  small  scrratus  ;  inwards,  with 
the  external  intercostals. 

Action. — It  depresses  the  ribs,  and  may  extend  the  dorsal  portion  of  the 
spine. 


MUSCLES  OF  TEE  TRUNK.  209 

7.  Transverse  Spinous  Muscle  of  the  Bach  and  Loins.     (Fig.  106,  3.) 

Sytionymx. — Transverso-spinous— Girarrf.  Dorso-lumbar  portion  of  the  semispinalis 
of  Miiu.     (The  spinalis  and  semispinalis  dorsi — Percivall.) 

Situation — Extent. — This  is  a  very  long  muscle,  directly  applied  to  the 
supersacral  and  dorso  lumbar  spine,  and  cuntiuuous,  in  front,  with  the 
trausversales  colli ;  these  two  muscles,  therefore,  meat^ure  nearly  the  whole 
length  of  the  spine. 

Structure. — It  is  formed  of  an  assemblage  of  short  fasciculi,  whicli  are 
flattened  on  both  sides,  tendinous  at  their  extremities,  directed  obliquely 
forwards  and  downwards,  and  a  little  inwards,  thus  crossing  at  a  right  angle 
the  spinous  processes  they  cover. 

Attachments. — These  fasciculi  are  attached,  below,  to  the  lateral  lip  of 
the  sacrum,  the  articular  tubercles  of  the  lumbar  vertebrte,  and  the  trans- 
verse processes  of  the  dorsal  vertebras — origin.  They  are  fixed,  above,  to  the 
spinous  processes  of  the  sacral,  lumbar,  and  dorsal  vertebra?,  and  into  that  of 
the  last  cervical  vertebra — termination.  It  is  to  be  remarked  that  they  do 
not  attain  the  summits  of  these  spinous  processes  in  the  first  half  of  the 
dorsal  region. 

Belations. — Outwards,  with  the  lateral  sacro-coccygeal  and  ilio-spinalis 
muscles,  which  are  confounded  with  it  near  its  posterior  extremity  ;  inwards. 
with  the  sacral  spine  and  the  spines  of  the  lumbar  and  dorsal  vertebras,  and 
with  the  interspinous  ligaments  of  these  three  regions. 

Action. — It  is  an  extensor  of  the  spine. 

DIFFEBEXTIAL   CHARACTERS   OP   THE   MUSCLES   IN   THE   SPINAL   REGION   OF   THE   BACK   AND 
LOrS'S   IN   OTHER   THAN   SOLIPED   ANIMALS. 

1.  KuMiNANTS. — In  the  Ox,  Sheep,  and  Goat,  the  trapezim  is  thick  and  very  broad. 
The  anterior  small  serrated  musde  is  inserted,  by  its  last  digitution,  into  the  ninth  rib. 

The  posterior  serrated  is  fixed  into  the  four  last  ribs. 

2.  Pig. — Its  trapezius  is  well  developed.  The  great  dorsal  is  voluminous,  and  ia 
attached  to  the  surface  of  the  ribs,  which  it  covers  by  digitations  from  its  fleshy  portion. 
It  is  fixed  near  the  small  trochanter  to  the  lip  of  the  bicipital  groove.  The  inferior 
branch  of  the  ilio-spinalis  of  this  animal  is  easily  divided  into  two  portions,  traces  of 
which  are  found  in  the  Horse:  one  is  formed  by  the  costal  fascicidi,  the  other  by  the 
transversal  fasciculi.  The  latter  constitutes  the  muscle  to  which  Bourgelat  has  given  the 
name  of  short  transversal. 

3.  Caenivora. — Several  of  the  spinal  muscles  in  the  Doq  resemble  those  of  the  Pig ; 
sitcli  are  the  trapezium,  the  great  dorsal,  and  the  ■ilio-spi7ialis.  In  animals  of  this  group, 
it  is  remarked  that  the  anterior  serrated  is  very  thick  and  very  developcil,  atul  that  it  is 
attached  to  the  eight  ribs  succeeding  the  second  by  as  many  well-marked  festoons.  The 
posterior  has  only  three  digitations,  which  are  attached  to  the  three  last  ribs.  The  common 
intercostal  exactly  resembles  the  sacro-lumbalis  of  Man  ;  behind  the  last  rib,  it  constitutes 
a  tliick  fleshy  bod)',  separated  by  a  fissure  from  the  ilio-spinalis,  witli  which  it  is  attached 
to  the  coxa.  Lastly,  the  transverse  spinal  muscle  of  the  hack  and  loins  is  very  strong  in 
the  lumbar  region,  and  is  prolonged  on  the  coccygeal  vertebrse. 

(According  to  Leyh,  tlie  interspinales  muscles  are  absent  in  the  Horse  and  Euminants ; 
they  are  found  in  the  Pig  between  the  spinous  processes  of  the  dorsal  and  lumbar 
vertebrae,  and  in  Camivora  between  the  spinous  processes  of  the  cervical  vertebrae.) 

comparison  OF  THE  MUSCLES  OF  THE  BACK  AND  NECK  IN  MAN  WITH  THE  ANALOGOUS 
MUSCLES   IN   THE   DOMESTICATED   ANIMALS. 

It  is  usual,  in  human  anatomy,  to  describe  by  the  name  of  muscles  of  the  back  and 
neck  those  which  correspond  to  the  superior  cervical  region,  and  those  of  the  spinal  region 
of  the  back  and  loins  of  the  domesticated  animals.  The  muscles  of  the  inferior  cervical 
region  are  described  in  Man  as  muscles  of  the  neck,  with  the  hyoid  muscles  and  the 
scalemis. 


210 


THE  MUSCLES. 


A,  Muscles  of  the  Back  and  Cervix. 

In  the  trapezius  of  Man,  a  cervical  and  a  dorsal  portion  can  no  longer  be  distinguished. 
Above,  it  is  attached  to  the  superior  occipital  curved  line ;  below,  it  is  fixed  to  tlio 
external  tlurd  of  the  upper  border  of  the  clavicle,  and  to  the  acromion  and  scapular  spine. 

Fig.  107. 


FIRST,   SECOND,    AND   PART   OF   THIRD   LAYER  OF    MUSCLES  OF   THE   BACK   OF   MAN; 
THE   FIRST   LAYER   OCCUPIES   THE    RIGHT,   THE   SECOND   THE   LEFT   SIDE. 

1,  Trapezius ;  2,  Tendinous  portion,  forming,  with  a  corresponding  part  of  the 
opposite  muscle,  the  tendinous  ellipse  on  the  back  of  the  neck ;  3,  Acromion 
process  and  spine  of  scapula;  4,  Latissimus  dorsi ;  5,  Deltoid;  6,  IMuscles  of 
dorsum  of  the  scapula:  infraspinatus,  teres  minor,  and  teres  major;  7,  Obliquus 
esternus ;  8,  Gluteus  medius ;  9,  Glutei  maximi ;  10,  Levator  anguli  scapulae ; 
11,  Rhomboideus  minor;  12,  Rhomboideus  major;  13,  S^denius  capitis,  overlying 
the  splenius,  above;  14,  Splenius  colli,  partially  seen:  the  common  origin  of  the 
splenius  is  attached  to  the  spinous  processes  below  the  origin  of  the  rhomboideus 
major;  15,  Vertebral  aponeurosis;  16,  Serratus  posticus  inferior;  17,  Supra- 
spinatus;  18,  Infraspinatus;  19,  Teres  minor;  20,  Teres  major;  21,  Long  head 
of  triceps,  passing  between  teres  minor  and  maior  to  the  arm ;  22,  Serratus 
magnus,  proceeding  forwards  from  its  origin  at  the  base  of  the  scapula;  23, 
Obliquus  internus  abdominis. 

The  fibres  of  the  trapezius  which  are  fixed  into  the  clavicle,  represent  a  portion  of  the 
mastoido-humcralis  of  quadrupeds. 

The  fireat  dorsal  resembles  that  of  the  Dog  and  Pig,  its  fleshy  portion  being  very 
developed ;  it  is  attached  to  the  exteriiid  face  of  the  four  last  ribs  by  muscular  digitations, 
and  terminates  ou  the  border  of  the  bicipital  groove. 


MUSCLES  OF  THE  TRUNK.  211 

The  rliomhoideus  is  bifid,  as  in  tlie  smaller  quadrupeds.  Less  developed  than  in  these 
animals,  tiie  angulark  is  only  fixal  in  front  to  the  four  first  cervical  vertebrse. 

In  Man,  the  splenius  is  larjie,  but  bj'  its  insertions  it  resembles  that  of  Solipeds.  The 
great  complexus,  thick  iind  broad  alwve,  is  incompletely  divided  into  two  fleshy  bodies, 
which  are  attached,  suprriorly,  to  the  sides  of  the  external  occipital  crest.  The  small 
complexus  is  not  fixed  into  the  axis  and  atlas,  its  superior  extremity  passing  directly  to 
tlie  mastoid  process. 

There  is  nothing  particular  to  note  regarding  the  straight  posterior  and  oblique  muscles 
of  the  head;  the  differences  ihey  ofler  in  their  form  are  allied  to  the  conformation  of  the 
bones  in  this  region. 

Of  the  two  small  serrated  muscles,  that  which  corresponds  to  the  anterior  serrated  of 
animals  rises  very  high ;  for  it  is  attached  by  an  aponeurosis  to  the  spinous  processes  of 
the  three  first  dorsal  vertebrae,  the  seventh  cervical,  and  the  cervical  ligament. 

There  are  found  in  ]Man,  lying  along  the  vertebral  furrows,  several  muscles  which 
represent  the  ilio-spinalis  and  the  common  intercostal  of  Solipeds.  Thus  the  common 
vias<  covering  the  lumbar  vertebrae  behind,  is  prolonged  by  two  series  of  flesh)^  and  ten- 
dinous fasciculi :  one  forms  the  sacro-lumbalis,  which  resembles  the  common  intercostal 
of  animals ;  the  other,  the  long  dorsal,  represents  the  infericjr  branch  of  the  ilio-spinalis. 
The  superior  branch  of  the  latter  is  found  in  the  transrerscdis  colli. 

Lastly,  there  are  also  seen  in  Man  a  transverse  spinal  and  intertransverse  muscles, 
which  correspond:  the  first,  to  the  transverse  s2)inous  of  the  back  and  loins  and  transverse 
spinous  of  the  neck  ;  the  second,  to  the  intertrunsversales  of  the  loins  of  the  domesticated 
species. 

B.  Muscles  of  the  Neck. 

The  mastoido-humeralis  is  not  present  in  Man,  bt-ing  peculiar  to  quadrupeds;  but  we 
should  see  a  portion  of  its  fasciculi  in  the  cleido-mastoideus  niuscle,  and  in  the  clavicular 
portions  of  the  trapezius  and  deltoid. 

The  sterno-mastoideus  corresponds  to  the  sterno-maxillaris  of  animals ;  as  in  the  Dog, 
it  is  inserted  into  the  external  face  of  the  mastoid  process  and  the  external  two-thirds  of 
the  superior  occipital  curved  line.  Below,  it  commences  by  two  fasciculi— one  from  tlie 
sternum,  the  other  from  the  clavicle.  We  have  already  alluded  to  this  clavicular 
fasciculus. 

The  sterno-hyoideus  and  sterno-thyroideus  are  large  and  well  developed,  resembling  in 
their  disposition  those  of  the  smaller  animals.  It  is  to  be  noted  that  the  sterno-hyoideus 
leaves  the  sternum,  the  first  costal  cartilage,  and  the  internal  extremity  of  the  clavicle. 
The  scapulo-hyoideus  is  digastric.  The  anterior  great  straight  muscle  of  the  head  is 
attached  to  tour  cervical  vertebra;,  as  in  Ruminants  and  the  Pig.  The  anterior  small 
straight,  the  lateral  small  straight,  and  the  long  muscle  of  the  neck,  comport  themselves  as 
in  the  smaller  animals.  The  anterior  scalenus  is  very  developed,  for  it  is  attached  to  the 
six  last  cervical  vertebrae. 

SUBLUMBAR,    OR   INFERIOR   LUMBAR   REGION. 

The  muscles  of  this  region  are  deeply  situated  at  the  inferior  face  of  the 
lumbar  vertebrae  and  the  ilium,  concurring  to  form  the  roof  of  the  abdominal 
cavity,  and  are  in  more  or  less  direct  contact  with  the  viscera  contained  in 
that  cavity.  They  are  nine  pairs.  Three  have  received  the  generic  name  of 
psoas,  and  are  of  large  volume  ;  they  are  maintained  by  a  strong  aponeurosis, 
the  iliac  fascia,  and  are  distinguished  as  the  great  psoas,  iliac  psoas,  and  stuall 
psoas.  A  fourth  is  named  the  square  muscle  of  the  loins  (quadratus  lumhorum), 
The  other  five,  placed  between  the  transverse  processes  of  the  lumbar  vertebrae, 
represent,  in  consequence  of  their  connection  with  these  kind  of  fixed  ribs, 
veritable  intercostal  muscles ;  these  are  the  intertransverse  muscles  of  tlie  loins. 

Preparation. — 1.  Place  the  subject  in  the  first  position  ;  open  the  abdominal  cavity  by 
completely  removing  its  inferior  walls  ;  empty  the  cavity  of  the  viscera  it  contains,  and 
excise  the  diaphragm,  as  that  muscle  prevents  the  anterior  extremity  of  the  great  and 
small  psoas  muscles  being  seen.  2.  First  study  the  iliac  fascia,  its  form,  relations  with 
the  long  abiluctor  of  the  leg.  its  attachments,  its  continuity  with  tlie  tendon  of  the  small 
psoas,  and  the  expansion  reflected  from  the  aponeurosis  of  the  great  abdominal  oblique 
muscle.  3.  Expose  the  three  psoas  muscles  by  removing  the  iliac  fascia,  the  two  adduc- 
tors of  the  leg,  and  the  three  adductors  of  the  thigh.  4.  Remove  the  psoas  muscles  for 
the  dissection  of  the  quadratus  and  intertransversales. 


212  TEE  MUSCLES 

1.  Hiac  Fascia  or  Liimho-iliac  Aponeurosis.     (Fig.  108,  a.) 

This  is  a  very  resisting  fibrous  expansion,  covering  the  great  and  iliac 
psoas  muscles.  Attached,  inwardly,  to  the  tendon  of  the  small  psoas,  out- 
wardly to  the  angle  and  external  border  of  the  ilium,  this  aponeurosis,  as  it 
extends  forwards  over  the  great  psoas,  degenerates  into  cellular  tissue. 
Behind,  it  also  becomes  attenuated  in  accompanying  the  two  muscles  it 
covers  until  near  their  insertion  into  the  internal  trochanter  of  the  femur. 
Its  external  or  inferior  face  receives,  posteriorly,  the  insertion  of  the  crural 
arch,  and  gives  attachment  to  the  long  adductor  of  the  leg ;  for  the  re- 
mainder of  its  extent,  it  is  covered  by  the  peritoneum. 

2.  Great  Psoas  Muscle.     (Fig.  108,  1.) 

Synonyms. — Subliitnbo-trochantineus — Glrard.  Psoas — Bour(jelat.  (Lumho-femoral- 
Leyh.     Psoas  magnus — PercivalL] 

Form — Situation. — This  is  a  long  muscle,  flattened  above  and  below  at  its 
anterior  extremity,  prismatic  in  its  middle,  and  terminated  in  a  cone  at  its 
posterior  extremity.  It  lies  beneath  the  transverse  processes  of  the  lumbar 
vertebrae. 

Structure. — Almost  entirely  fleshy,  this  muscle  is  formed  of  fasciculi, 
very  delicate  in  texture,  directed  backwards,  and  long  in  proportion  to  their 
superficial  and  deep  situation.  They  all  converge  to  a  tendon  which  is 
enveloped  by  the  iliac  muscle,  and  is  confounded  with  it. 

Attachments. — The  great  psoas  is  attached:  1,  By  the  anterior  extremity 
of  its  fleshy  fasciculi  to  the  bodies  of  the  last  two  dorsal  and  the  lumbar 
vertebrae,  except  the  hindermost,  and  to  the  inferior  face  of  the  two  last  ribs 
and  the  transverse  processes  of  the  lumbar  vertebrte  ;  2,  By  its  posterior 
tendon  to  the  internal  trochanter,  in  common  with  the  j^soas  iliacus. 

Belations. — Below,  with  the  pleura,  the  superior  border  of  the  diaphragm, 
the  lumbo-iliac  aponeurosis,  which  separates  it  from  the  peritoneum  and 
the  abdominal  viscera  situated  in  the  sublumbar  region ;  above,  with  the 
two  last  internal  intercostals,  the  quadratus,  and  the  intertransversales 
muscles ;  inwardly,  with  the  small  psoas  and  the  internal  branch  of  the 
iliac  psoas ;  outwardly,  for  its  posterior  third,  with  the  principal  branch  of 
the  latter  muscle. 

Action. — A  flexor  and  rotator  of  the  thigh  outwards  when  its  fixed  point 
is  the  loins,  this  muscle  also  flexes  the  lumbar  region  when  the  thigh  is 
a  fixed  point.  It  is,  therefore,  one  of  the  agents  which  determine  the  arching 
of  the  loins,  and  which  operate,  during  exaggerated  rearing  or  pr.incing,  in 
bringing  the  animal  into  a  quadrupedal  position  again. 

3.  Hiac  Psoas  Muscle.     (Fig.  108,  3,  4.) 

Synonyms. — Ilio-trochantineus — Girard.  (Leyh  divides  this  muscle  into  two  j)or- 
tions.  wliich  Ik;  describes  as  the  qreat  and  middle  ilio-femoralis.      Iliacus — PercivalL) 

Form — Situation — Direction. — This  is  a  very  strong,  thick,  and  prismatic 
muscle,  incompletely  divided  into  two  unequal  portions  by  the  groove  for 
the  reception  of  the  tendon  of  the  great  psoas :  an  external  portion,  somewhat 
considerable  in  size ;  and  an  internal,  small.  These  two  muscular  portions 
lie  at  the  entrance  to  the  pelvis,  on  the  inner  face  of  the  ilium,  in  an  oblique 
direction  downwards,  backwards,  and  inwards. 

Structure. — It  is  almost  entirely  fleshy.     The  fasciculi  forming  it  are 


MUSCLES  OF  THE  TRUNK. 


213 


spread  ont  in  front,  and  collected  behind,  where  they  become  slightly  fibrous, 
and  unite  with  the  tendon  of  the  great  psoas. 

Attachments. — It  has  its  fixed  insertion  on  the  whole  of  the  iliac  surface, 
on  the  external  angle  of  the  ilium,  the  sacro-iliac  ligament,  and  the  ilio- 


MUSCLES   OF   THE   SUBLUilBAE,    PATELLAE,    AND   INTERNAL   CRTJEAL   REGIONS 

1,  Psoas  magnus;  1',  Its  terminal  tendon;  2,  Psoas  parvus;  3,  Iliac  psoas;  4,  Its 
small  internal  portion  ;  5,  Muscle  of  the  fascia  lata  ;  6,  Anterior  straight  muscle 
of  the  thigh;  7,  Vastus  internus  ;  8,  Long  adductor  of  the  leg;  9,  Short  adductor 
of  the  leg  ;  11,  Pectineus;  12,  Great  adductor  of  the  thigh;  12',  Small  adductor 
of  the  thigh-,  13,  Semimembranosis ;  14,  Semitendinosis. — a.  Portion  of  the 
fascia  iliaca ;  B,  Portion  of  the  membrane  reflected  from  the  aponeurosis  of  the 
abdominal  great  oblique  muscle,  forming  the  crural  arch  (Poupart's  ligament); 
C,  Pubic  tendon  of  the  abdominal  muscles;  D,  Origin  of  the  pubio-femoral 
ligament. 

pectineal  crest.     Its  movable  insertion  is  into  the  small  internal  trochanter, 
in  common  with  the  great  psoas. 

Eelations. — Above,  with  the  ilium ;  below,  with  the  iliac  fascia  and  the 
long  adductor  of  the  leg ;  outwardly,  with  the  muscle  of  the  fascia  lata  and 
17 


214 


THE  MUSCLES. 


the  origin  of  the  anterior  straight  muscle  of  the  thigh,  from  which  it  is 
separated  by  a  space  filled  with  fat ;  inwardly,  with  the  crural  vessels.  It 
passes  between  the  vastus  internus  and  the  pectineus,  to  reach  the 
trochanter. 

Actions. — It  is  a  flexor  and  rotator  outwards  of  the  thigh. 

4.  Small  Psoas  Muscle.     (Fig.  108,  2.) 

Synonyms. — Psoas  of  the  loins — Bourgelat.  Sublumto-pubialis,  or  sublumbo-iliacus, 
according  to  Girard.     {Psoas  parvus — Percivall,    The  ktmbo-iliacus  of  Leyh.) 

Situation — Form — Structure. — Placed  at  the  inner  side  of  the  great  psoas, 
very  much  elongated,  and  semipenniform  in  shape,  this  muscle  is  terminated 
behind  by  a  flattened  tendon,  and  is  composed  of  fleshy  fibres,  the  longest  of 
which  ai"e  anterior.  These  fasciculi  are  all  directed  backwards  and  outwards 
to  gain  the  tendon. 

Attachments. — 1,  To  the  bodies  of  the  three  or  four  last  dorsal,  and  to  all 
the  lumbar  vertebras,  by  the  anterior  extremity  of  its  fleshy  fibres ;  2,  To 
the  ilio-pectineal  eminence  and  the  lumbo-iliac  aponeurosis,  by  the  posterior 
extremity  of  its  tendon. 

Belations. — By  its  inferior  face  with  the  pleura,  the  superior  border  of  the 
diaphragm,  the  aorta  or  posterior  vena  cava,  and  the  great  sympathetic 
nerve ;  by  its  upper  face,  with  the  psoas  magnus.  It  is  traversed,  near  its 
vertebral  insertions,  by  numerous  vascular  and  nervous  branches. 

Actions. — It  flexes  the  pelvis  on  the  sj^ine,  when  the  loins  are  the  fixed 
point ;  but  should  the  pelvis  be  fixed,  it  arches  or  laterally  inclines  the  lumbar 
region.     It  is  also  the  tensor  muscle  of  the  lumbo-iliac  aponeurosis. 

5.  Square  Muscle  of  the  Loins. 
(Fig.  109,  "l.) 

Synonyms.  —  Sacro-costalis  — 
Girard.  {Sacro-lmnbalis — Ferclvall. 
Quadratus  lumborum  of  Man.) 

Situation — Form —  Structure 
— Attachments. — This  muscle  is 
comprised  between  the  trans- 
verse processes  of  the  lumbar 
region  and  the  great  psoas,  and 
is  elongated  from  before  to  be- 
hind, flattened  above  and  below, 
and  divided  into  several  very 
tendinous  fasciculi.  The  prin- 
cipal fiisciculus,  situated  out- 
wardly, takes  its  origin  from 
the  sacro-iliac  ligament,  near 
the  angle  of  the  sacrum,  and  ex- 
tends directly  forward  to  gain 
the  posterior  border  of  the  last 
rib,  after  being  attached  by  its 
upper  face  to  the  summits  of  the 
transverse  processes  of  the  lum- 
bar vertebrae.  The  other  fasci- 
culi are  longer  as  they  are  an- 
terior; they  leave  the  internal 
border  of  the  first,  and  are  directed  oblic^uely  forward  and  inward,  to  be 


DEEP   MUSCLES   OF   THE   SUnLUMBAR   REGION. 

Quadratus  lumborum ;  2,  2,  Intertransversales ; 
3,  Small  retractor  muscle  of  the  last  rib — a  de- 
pendent of  the  small  oblique  of  the  abdomen. 


MUSCLES  OF  THE  TRUNK  215 

fixed  into  the  transverse  processes  of  tlie  majority  of  the  lumbar  vertebrte 
and  the  inner  face  of  the  two  or  three  last  ribs. 

Belations. — By  its  upper  face,  with  the  intertransversales,  the  small 
retractor  of  the  last  rib,  and  the  fibrous  fascia  which  unites  that  muscle  to 
the  small  oblique  of  the  abdomen.     By  its  inferior  face,  to  the  great  psoas. 

Actions. — It  draws  the  last  ribs  backwards,  and  inclines  the  lumbar  spine 
to  one  side. 

6.  Intertransverse  Muscles  of  the  Loins.     (Fig.  109,  2,  2.) 
(Synonym — Intertransversales  lumborum — Percitall.) 

These  are  very  small  flat  muscles  which  fill  the  intervals  between  the 
transverse  processes  of  the  lumbar  vertebrte.  The  muscular  fibres  entering 
into  their  composition  are  mixed  with  tendinous  fibres,  and  are  carried  from 
the  anterior  border  of  one  transverse  process  to  the  posterior  border  of  the 
other. 

They  respond,  by  theii-  superior  face,  to  the  ilio-spinalis  (longissimus 
dorsi),  and  by  their  inferior  face  to  the  quadratus,  as  well  as  the  psoas 
magnus.     They  act  by  inclining  the  lumbar  region  to  one  side. 

DIFFEREKTI.\L    CHARACTERS    OF   THE    MUSCLES    OF   THE    SUELOIBAK    REGIOX   IN   OTHER 
THAN    SOLIPED   AXDIALS. 

In  Hiiminants  and  the  Pig,  the  muscles  of  this  region  so  closely  resemble  those  of 
Solipeds,  that  a  special  description  is  unnecessary. 

In  the  Bog,  the  great  psoas  is  little  developed,  and  only  commences  at  the  third,  or 
even  the  fourth  Imubar  vertebra;  the  iliac  psoas  is  very  slender,  particularly  in  its 
external  portion :  otherwise  it  is  scarcely  distinct  from  the  great  psoas,  with  which  it  may 
be  said  to  form  one  muscle  ;  the  small  psoas  is  relatively  larger  than  the  great;  it  is  not 
prolonged  into  the  pectoral  cavity,  and  its  anterior  extremity  is  confounded  with  the 
quadratus  lumborum,  which  is  longer  and  stronger  than  in  all  the  other  animals. 

COMPARISON  OF   THE   SCBLOIBAR  MUSCLES   OP  MAN  WITH  THOSE   OF  ANMALS. 

In  human  anatomy,  by  the  names  of  psoas  and  iliacus  are  described  the  great  psoas 
and  iliac  psoas  of  animals.  The  psoas  magnus  of  Man  is  distinguished  from  that  of 
Solipeds  by  its  superior  insertions,  which  do  not  go  beyond  the  last  dorsal  vertebrse. 

The  small  psod-s  is  often  absent ;  when  present,  it  is  attached,  above,  to  the  bodies  of 
the  twelve  dorsal  vertebrae,  below,  to  the  ilio-pectineal  crest. 

The  intertransversales  have  been  studied  with  the  muscles  of  the  back.  The 
quadratus  of  the  loins,  classed  by  anthropotomists  with  the  abdominal  muscles,  is 
distinctly  divided  into  three  series  of  fasciculi :  ilio-costal  fasciculi,  which  pass  from  the 
upper  border  of  the  ilium  to  the  twelfth  rib ;  lumho-costal  fasiculi.  passing  from  the 
transverse  processtr-s  of  the  three  or  four  last  lumbar  vertebrae  to  the  twelfth  rib,  and  ilio- 
lumhar  fasciculi,  going  from  the  iliac  crest  to  the  posterior  face  of  the  transverse  processes 
of  all  the  lumbar  vertebrai. 

COCCTGEAL   EEGION. 

This  region  is  composed  of  four  pairs  of  muscles  destined  for  the 
movements  of  the  tail :  three,  named  the  sacro-coccygeal,  are  disposed 
longitudinally  around  the  coccygeal  vertebrte,  which  they  completely 
envelop  ;    the  fourth  is  designated  the  iscliio-coccygeus. 

1.  Sacro-coccygeal  Muscles.     (Fig.  131,  1,  2,  3.) 

These  three  muscles  are  inclosed,  with  those  of  the  opposite  side,  in  a 
common  aponeurotic  sheath  which  is  continuous  with  the  inferior  ilio-sacral 
and  sacro-ischiatic  ligaments.  They  commence  on  the  sacrum,  are  directed 
backwards  and  parallel  AA-ith  the  coccyx,  gradually  diminishing  in  thickness, 
and  are  decomposed  into  several  successive  fasciculi  terminated  by  small 


216  THE  MUSCLES. 

tendons,  which  are  inserted  into  each  of  the  coccygeal  bones.  With  regard 
to  their  situation,  these  muscles  are  distinguished  as  sacro-coccygeus  superior, 
sacro-coccygeus  inferior,  and  sacro-coccygeus  lateralis. 

a.  Sacro-coccygeus  Superior. 
(^Synonym. — Erector  coccygis — Percivall. ) 

The  fasciculi  which  form  this  muscle  lake  their  fixed  insertion  either 
from  the  summits  and  sides  of  the  three  or  four  last  processes  of  the  super- 
sacral  spine,  or  from  the  coccygeal  vertebrae  themselves.  'J'he  tendons 
through  which  they  effect  their  movable  insertion  into  these  vertebrge  are 
always  very  short. 

This  muscle,  covered  by  the  coccygeal  aponeurosis,  in  turn  covers  the 
vertebrae  it  is  designed  to  move.  It  responds ;  inwardly,  to  the  analogous 
muscle  of  the  opposite  side  ;  outwardly,  to  the  lateral  sacra-coccygeus,  and, 
near  its  anterior  extremity,  to  a  very  strong  aponeurotic  expansion  which 
separates  it  from  the  transverse  spinous  muscle.  It  directly  elevates  the  tail, 
or  pulls  it  to  one  side,  according  as  it  acts  in  concert  with  its  fellow  or 
singly. 

h.  Sacro-coccygeus  Inferior. 
(Synonym. — Depressor  coccygis — Percivall.) 

This  muscle  is  thicker  than  the  preceding;  its  constituent  fasciculi 
take  their  origin  from  the  inferior  surface  of  the  sacrum,  towards  the  third 
vertebra,  and  from  the  internal  face  of  the  sacro-ischiatic  ligament  and  the 
coccygeal  bones.  It  readily  divides  into  two  parallel  portions,  which 
Bourgelat  has  described  as  two  separate  muscles.  The  fasciculi  of  the 
internal  portion  are  inserted,  by  their  posterior  extremity,  into  the  inferior 
face  of  the  first  coccygeal  vertebrae.  Those  of  the  external  portion  are  all 
furnished  with  strong  superficial  tendons,  nearly  all  of  which  are  for  the 
bones  of  the  tail. 

This  muscle  responds  :  outwardly,  to  the  ischiatic  ligament,  the  ischio- 
coccygeus  and  coccygeal  aponeurosis  ;  inwardly,  to  the  muscle  of  the  opposite 
side,  and  to  the  coccygeal  attachment  of  the  rectum ;  above,  to  the  sacrum, 
the  bones  of  the  tail,  and  the  lateral  muscle ;  below,  to  the  rectum  and  the 
coccygeal  aponeurosis. 

It  either  directly  depresses  the  tail  or  inclines  it  to  one  side. 

c.  Sacro-coccygeus  Lateralis. 
{Synonym. — Curvator  coccygis — Percivall.') 

This  muscle  may  be  considered  as  the  transverse  spinous  of  the  coccygeal 
region ;  indeed,  it  is  confounded  with  that  muscle  of  the  back  and  loins 
by  its  anterior  extremity,  and  appears  to  continue  it  to  the  inferior 
extremity  of  the  tail. 

The  fasciculi  composing  it  have  their  origin  from  the  spinous  processes 
of  the  last  lumbar  vertebrae,  through  the  medium  of  the  transverse  spinous,  and 
from  the  coccygeal  bones.  The  tendons  terminating  these  fasciculi  are  deep 
and  not  very  distinct. 

It  responds ;  outwardly,  at  the  posterior  extremity  of  the  ilio-spinalis,  to 
the  inferior  ilio-sacral  ligament  and  the  coccygeal  aponeurosis;  inwardly, 
to  the  transverse  spinous  and  the  coccygeal  vertebrae ;  above,  to  the  superior 
muscle ;    below    to   the   inferior   muscle,   from   which   it  is  nevertheless 


MISCLES  OF  THE  HEAD.  217 

separated  by  several  small  independent  muscular  fasciculi,  which  are  carried 
from  one  coccygeal  vertebra  to  another.  (Leyh  designates  these  the  inter 
transversales  of  the  tail.)     It  inclines  the  tail  to  one  side. 

2.  Ischio-coccygeus.     (Fig  131,  41.) 
\^Synonym. — Compressor  coccygis — I'trcicall.) 

A  small,  thin,  wide,  and  triangular  muscle,  situated  against  the  lateral 
wall  of  the  pelvis,  at  the  internal  face  of  the  sacro-ischiatic  ligament. 

It  is  attached,  by  an  aponeurosis,  to  that  ligament  and  to  the  ischiatic 
crest ;  it  is  then  directed  upwards  to  be  fixed,  by  its  muscular  fibres,  to  the 
side  of  the  last  sacral  vertebra  and  the  first  two  coccygeal  bones. 

It  is  related,  outwardly,  vnih  the  sacro-ischiatic  ligament,  and  inwardly  to 
the  lateral  sacro-coccygeus  and  the  rectum. 

It  depresses  the  entire  caudal  appendage. 

REGION    OF    THE    HKAS. 

The  head  comprises  a  large  number  of  muscles,  of  which  only  those 
covering  the  bones  of  the  face,  and  those  which  move  the  lower  jaw  and  os 
hyoides,  will  be  described.  The  others  will  be  studied  with  the  apparatus 
to  which  they  belong. 

A..    Facial  Region. 

This  region  includes  those  muscles  of  the  head  which  form  a  part  of  the 
framework  of  the  lips,  cheeks,  and  nostrils :  that  is,  all  those  which  are 
grouped  around  the  face,  properly  called.  Authors  are  far  from  being 
unanimous  with  regard  to  the  nomenclature  and  description  of  these  muscles. 
Girard  recognised  eleven,  to  which  he  gave  the  following  names :  labialis. 
alveolo-labialis,  zygomatico-labialis,  lachrymo-lahialis,  supernaso-lahialis,  super- 
maxillo-labialis,  siqyerma.iillo-nasalis  magnus.  sii]3erma.Tillo-nasalis  parvus, 
transversalis  7msi,  ma.viUo-labialis,  mento  labialis.  To  these  eleven  muscles, 
three  of  which  are  single,  two  others  are  added ;  these  were  described  by 
Bourgelat  as  the  middle  (intermediate)  anterior  and  middle  (intermediate)  pos- 
terior muscles,  which  Girard  wrongly  considered  as  belonging  to  the  labial. 

1.  Labialis,  or  Orbicularis  of  the  lAps.     (Fig.  110,  27.) 
(Synonym. — Orbicularis  oris — PercivaU.) 

rreparntiiin.—Fievaoxe  with  scissors  the  skin  covering  the  two  portions  of  this 
muscle  :  afterwards  the  buccal  mucous  membrane  and  subjacent  glands  within  the  lips,  to 
expose  its  internal  face. 

The  labialis.  disposed  as  a  sphincter  around  the  anterior  opening  of  the 
mouth,  is  regarded  as  the  intrinsic  muscle  of  the  lips,  and  is  composed  of 
two  portions  or  fasciculi,  one  for  the  upper,  the  other  for  the  lower  lip. 
United  to  each  other  at  the  commissures  of  the  mouth,  and  confounded  with 
the  superficial  layer  of  the  alveolo-labialis,  which  they  appear  to  continue, 
these  two  muscular  portions  also  receive  a  large  portion  of  the  fibres 
belonging  to  the  majority  of  the  extrinsic  muscles,  such  as  the  supermaxillo- 
nasalis  magnus  and  supcrnaso-labialis. 

The  orbicularis  is  not  attached  to  the  neighbouring  bone ;  its  component 
fibres  afiecting  a  circular  form,  have,  consequently,  neither  beginning  nor 
ending,  except  in  being  continuous  with  other  fibres. 

The  internal  face  of  the  superior  fasciculus  responds  to  a  layer  of  salivary 


218 


THE  MUSCLES. 


glands,  which  in  part  separate  it  from  the  buccal  mucous  memhrane.  The 
external,  covered  by  the  skin,  adheres  to  it  in  the  most  intimate  manner,  and 
is  found  isolated  from  it  only  on  the  median  line,  at  first  by  the  aponeui'otic 
expansion  of  the  suiiermaxillo-labialis,  then  by  a  musculo-fibrous  layer 
analogous  to  that  which  forms  the  mento-labialis. 

By  its  internal  face,  the  inferior  fasciculus  likewise  responds  to  the  buccal 
mucous  membrane,  and  to  some  salivary  glands.     By  its  external  face,  it 

Fi?.  110. 


SUPERFICIAL   MUSCLES   OF   THE   FACE   AND   HEAD. 

1,  Temporo-auricularis  e.xternus,  or  attollens  maximus ;  2,  Levator  palpebrre,  or 
corrugator  supercilii ;  3,  Temporo-auricularis  internus,  or  attollens  posterior; 
4,  5,  Zygomatico-auricularis,  or  attollens  anterior ;  6,  Orbicularis  palpebrarum ; 
7,  Parotido-aurieularis,  or  deprimens  aurem  ;  8,  Parotid  gland  ;  9,  Temporal,  or 
subzygomatlc  vein;  10,  Ditto,  artery;  11,  12,  Superior  and  inferior  maxillary 
nerves;  13,  Fascia  of  the  masseter  muscle;  14,  Nasal  bones;  15,  Supernaso- 
labialis,  or  levator  labii  superioris  alaique  nasi ;  16,  Supermaxillo-labialis,  or 
nasalis  longus  labii  superioris ;  17,  External  maxillary  or  facial  artery ;  18, 
Facial  vein ;  19,  Supermaxillo-nasalis  magnus,  or  dilatator  naris  lateralis ;  20, 
Superior  maxillary  nerve  ;  21,  Zygomatico-labialis,  or  zygomaticus ;  22,  Parotid, 
or  Stenon's  duct ;  23,  Masseter ;  24,  Alveolo-labialis,  or  buccinator ;  25,  Super- 
maxillo-nasalis parvus,  or  nasalis  brevis  labii  superioris;  27,  Labialis,  or  orbicu- 
laris oris ;  28,  Maxillo-labialis,  or  depi-essor  labii  inferioris ;  29,  Mento-labialis, 
or  levator  menti. 

forms  an  intimate  union  with  the  cutaneous  integument,  like  the  superior 
fasciculus. 

This  muscle  plays  the  part  of  a  constrictor  of  the  anterior  opening  of  the 
mouth,  and  has  complex  functions  to  perform  in  suction,  the  prehension  of 
food,  and  in  mastication. 


2.  Aheolo-laUalis.     (Fig.  110,  24.) 

Synonyms.— M.o\&r\ii  externiis  et  internus — Bourgehd.  {Buccinator — Percivall.  Leyh 
divides  this  muscle  into  two  portions ;  its  superlicial  plane  he  designates  the  buccinator, 
and  the  deep  plane  the  molaris.) 

Preparation.— Proceed  to  the  ablation  of  the  masseter  ;  dissect  the  external  surface  of 
the  muscle,  takinp;  care  of  the  risoiius  Santorini  and  zygomaticus,  which  are  confounded 
with  it.  Then  divide  it  in  the  middle,  as  far  as  the  commissure  of  the  lips;  turn 
down  each  strip  on  the  jaw.s,  and  remove  the  mucous  membrane,  in  order  to  study  the 
inner  face  of  the  muscle  and  the  attachments  of  the  superficial  plane  to  the  maxillary 
bones. 


MUSCLES  OF  THE  HEAD.  219 

Situation — Form. — Situated  on  the  sides  of  the  face,  partly  concealed  by 
the  masseter  muscle,  and  applied  to  the  mucous  membrane  of  the  cheeks,  the 
alveolo-labialis  is  a  flat,  thin  muscle,  elongated  in  the  direction  of  the  head, 
and  formed  of  two  superposed  jilanes. 

Extent — Structure — Attachments. — The  deep  plane,  the  longest  and  least 
wide,  is  narrower  at  its  extremities  than  its  middle,  and  is  formed  of  strongly 
aponeurotic  muscular  fasciculi,  which  are  attached,  posteriorly :  1,  To  the 
alveolar  tuberosity  ;  2,  To  the  external  surface  of  the  superior  maxillary 
bone,  above  the  last  three  molar  teeth;  3,  To  the  anterior  border  of  the 
inferior  maxillary  bone,  behind  the  sixth  molar,  in  common  with  the  maxillo- 
labialis.  On  reaching  the  commissm-e  of  the  lips,  this  muscular  layer 
appears  to  be  continued  by  small  tendons  with  the  fibres  of  the  orbicularis. 

The  superficial  plane  only  begins  about  the  middle  of  the  deep  one,  whose 
anterior  half  it  entirely  covers.  Its  fibres,  less  tendinous  than  those  of  the 
latter,  extend  from  a  median  raphe  which  also  divides  the  deep  layer  in  its 
length,  and  are  directed,  some  forwards,  some  backwards,  to  terminate  in  the 
following  manner  :  the  first  are  inserted  into  the  external  face  of  the  super- 
maxillary  bone,  above  the  first  molar  tooth  and  the  superior  interdental 
space  ;  the  second  are  attached  to  the  inferior  interdental  space  alone. 

Relations. — Externally,  with  the  masseter,  zygomatico-labialis,  cuticularis, 
great  supermaxillo-nasalis,  supernaso-labialis,  the  parotid  duct,  which  crosses 
it  to  enter  the  mouth,  and  the  facial  artery  and  veins ;  internally,  with  the 
buccal  mucous  membrane.  The  deep  plane  is  accompanied  and  covered  at  its 
anterior  border  by  the  upper  molar  glands ;  its  posterior  border  is  margined 
by  the  inferior  molar  teeth,  which  it  partially  covers.  The  superficial  layer 
is  distinctly  separated  from  the  deep  one  in  its  anterior  part,  which  is  attached 
to  the  superior  maxillary  bone.  Behind,  these  two  planes  adhere  more 
intimately  to  one  another,  though  they  are  found  completely  isolated  by  an 
interstice  in  which  one  or  two  large  veins  pass. 

Actions. — The  function  of  the  alveolo-labialis  is  particularly  related  to 
mastication  :  this  muscle,  in  fact,  pushes  between  the  molar  teeth  the  portions 
of  food  which  fall  outside  the  alveolar  arches  ;  but  it  cannot  aid  in  bringing 
the  two  jaws  together,  as  M.  Lecoq  has  correctly  observed. 


3.  Zygomatico-labialis.     (Fig.  110,  21.) 

Synonyms. — Portion  of  the  cuticularis  of  Bourgelat.     The  zygomaticus  major  of  Man. 
(^Zygomaticus — Percivall.) 

A  very  small,  pale,  and  thin  ribbon-like  muscle,  arising  from  the  surface 
of  the  masseter,  near  the  maxillary  spine,  by  an  aponeurosis  which  is  con- 
founded with  the  cuticularis ;  it  terminates  on  the  surface  of  the  alveolo- 
labialis,  at  a  short  distance  from  the  commissure  of  the  lijjs.  Covered  by 
the  skin,  it  covers  the  alveolo-labialis  muscle,  and  some  of  the  superior  molar 
glands,  vessels,  and  nerves. 

This  muscle  pulls  backwards  the  commissure  of  the  lips  when  it  is  in  a 
state  of  contraction. 

In  Solipeds  there  is  also  sometimes  found  a  muscle  resembling  the 
zygomaticus  minor  of  Man.  It  is  a  very  small  fasciculus  situated  under  the 
preceding  muscle,  near  its  superior  extremity.  It  appears  that  this  fasciculus 
is  continued,  above,  by  the  fibres  of  the  lachrymo-labialis,  and  is  lost,  below, 
on  the  alveolo -labial  surface,  a  little  beneath  the  carotid  canal. 


220  THE  MUSCLES. 

4.  Laclirymo-ldbial,  or  Lachrymal  Muscle. 
(^Synonym, — ^Not  mentioned  by  Percivall.    It  is  the  inferior  palpebral  muscle  of  Leyh.) 

A  wide  and  very  thin  muscle,  situated  superficially  below  the  eye  :  it  is 
continuous,  in  front,  with  tlie  supernaso-labialis ;  behind,  with  the  cu- 
ticularis;  above,  with  the  orbicularis  of  the  eyelids.  Its  fibres,  partly 
muscular  and  partly  aponeurotic,  leave  the  external  surface  of  the  lachrymal 
and  zygomatic  bones,  are  directed  downwards,  and  become  lost  in  a  cellular 
fascia  which  covers  the  alveolo-labialis  ;  some  pass  beneath  the  zygomatico- 
labialis  and  form  the  zygomaticus  minor,  when  this  is  present. 

This  muscle  is  supposed  to  corrugate  and  twitch  the  skin  below  the 
eye. 

5.  Supernaso-labialis.    (Fig.  110,  15.) 

Synonyms. — ^The  maxillaris  of  Bourgelat.  The  levator  lahii  superioris  alasque  nasi  of 
Man.     (Levator  lahii  superioris  alxque  nasi — Percivall.     Fronto-labialis — Leyh.) 

Situation — Direction — Form — Structure. — Situated  on  the  side  of  the 
face,  in  an  oblique  direction  downwards  and  backwards,^  the  supernaso- 
labialis  is  a  wide  muscle,  flattened  on  both  sides,  elongated  from  below  to 
above,  aponeurotic  at  its  superior  extremity,  and  divided  inferiorly  into  two 
unequal  branches,  between  which  passes  the  great  supermaxillo-nasalis. 

Attachments. — It  has  its  origin,  by  its  superior  aponeurosis,  from  the 
frontal  and  nasal  bones,  and  unites  on  the  median  line  with  the  muscle  of 
the  opposite  side.  Its  anterior  branch,  the  widest  and  thickest,  goes  to  the 
external  ala  of  the  nose  and  to  the  upper  lip,  where  its  fibres  are  confounded 
with  those  of  the  orbicularis.  The  posterior  branch  terminates  at  the 
commissure  of  the  lips. 

Belations.—Oiitwiirds,  with  the  skin;  inwards,  with  the . supermaxillo- 
labialis,  the  posterior  portion  of  the  small  supermaxillo-nasalis,  and  vessels 
and  nerves.  Its  posterior  branch  covers  the  great  supermaxillo-nasalis, 
and  the  anterior  is  covered  by  that  muscle. 

Actions. — It  elevates  the  external  ala  of  the  nose,  the  upper  lip,  and  the 
commissure  of  the  lips. 

6.  Supermaxillo-lahialis.     (Fig.  110,  16.) 

Synonyms. — Levator  lahii  superioris  of  Bourgelat.  The  levator  lahii  superioris  proprii  of 
Man.     (Nasalis  longtcs  lahii  superioris — Percivall.) 

Situation — Direction — Form  —  Structure. — Lying  vertically  on  the  side 
of  the  face,  below  the  supernaso-labialis,  this  muscle  is  a  thick  and  conical 
fleshy  mass,  terminated  inferiorly  by  a  tendon. 

Attachments. — It  is  attached,  by  the  upper  extremity  of  its  fleshy  body, 
to  the  external  surface  of  the  supermaxillary  and  zygomatic  bones — origin. 
Its  terminal  tendon  passes  over  the  transverse  muscle  of  the  nose,  to  unite 
with  that  of  the  opposite  side,  and  with  it  to  form  a  single  aponeurotic 
expansion,  which  dips  by  small  fibres  into  the  subcutaneous  musculo-fibrous 
tissue  of  the  upper  lip. 

Belations. — Covered  by  the  lachrymal  and  supernaso-labialis  muscles, 
this  muscle  in  turn  covers  the  supermaxillary  bone,  the  bottom  of  the  false 
nostril,  the  small  supermaxillo-nasalis,  and  the  transversalis  nasi. 

Actions. — It  raises  the  upper  lip,  either  directly  or  to  one  side,  as  it  acts 
singly  or  in  concert  with  its  congener. 

'  It  is  to  be  remembered  that  we  suppose  the  head  maintained  in  a  vertical  position. 


MUSCLES  OF  THE  HEAD.  221 

7.  Great  Supermaxillo-nasalis.     (Fig.  110,  19,) 

Synonyms. — The  pyramidalis-nasi  of  Bourgelat.  The  canfnusof  Man.  f Dilatator  naris 
lateralis — Percivall.') 

Situation — Direction — Form — Structure. — This  muscle,  situated  on  the 
side  of  the  face,  between  tht  two  branches  of  the  supernaso-labialis,  in  an 
almost  vertical  direction,  is  of  a  triangular  form,  and  slightly  tendinous  at  its 
summit. 

Attachme7its. — It  has  its  origin,  by  the  aponeurotic  fibres  of  its  summit, 
from  the  external  face  of  the  supermaxillary  bone,  below  its  ridge. — It 
terminates,  by  its  base,  on  the  skin  covering  the  external  wing  of  the  nostril, 
its  most  posterior  fibres  being  confounded  with  those  of  the  orbicularis  of 
the  lips. 

Belations. — Outwardly,  with  the  skin  and  the  inferior  branch  of  the 
supernaso-labialis ;  inwardly,  vrith  the  anterior  branch  of  that  muscle,  and 
with  vessels  and  nerves. 

Actions. — It  dilates  the  external  orifice  of  the  nasal  cavity,  by  pulling 
outwards  the  external  wrng  of  the  nostril. 

8.  Small  Su]3erma.xiUo-nasalis.     (Fig.  110,  25.) 

Synonyms. — The  nasalis  brevis,  and  portion  of  the  subcutaneous  muscle  of  Bourgelat. 
(Nasalis  brevis  labii  superioris — Percivall.) 

Girard  has  described,  by  the  above  name,  a  small,  thick,  and  short 
musciilar  fasciculus  which  covers  the  external  process  of  the  premaxillary 
bone,  and  whose  fibres,  either  originating  from  that,  the  supermaxillary 
bone,  or  the  internal  face  of  the  supernaso-labialis  muscle,  terminate  in  the 
skin  of  the  false  nostril,  and  the  appendix  of  the  inferior  turbinated  bone. 

Eigot  has  attached  to  this  muscle  that  described  by  Boui'gelat  as  the 
short  muscle.  The  latter  is  composed  of  short,  transverse  fibres,  applied  to 
the  expansion  of  the  cartilaginous  septum  of  the  nose  which  projects 
laterally  beyond  the  nasal  spine.  These  fibres  abut,  by  their  most  eccentric 
extremities,  against  the  skin  of  the  false  nostril  and  the  appendix  of  the 
superior  turbinated  bone. 

In  adopting  Eigot's  description,  it  is  found  that  the  small  supermaxillo- 
nasalis  is  composed  of  two  portions,  which  border  the  re-enteriug  angle 
formed  by  the  large  process  of  the  premaxillary  bone  and  the  nasal  spine. 
These  two  portions,  posterior  and  anterior,  unite  at  their  upper  extremities. 
The  first  appears  to  be  confounded,  below,  -with  the  middle  anterior 
(depressor  alfe  nasi),  the  second  is  continuous  with  the  transversalis  nasi. 
When  they  contract,  they  concur  in  the  dilatation  of  the  false  nostril  and 
the  proper  nasal  cavity. 

9.  T)-ansversalis  Nasi. 
Synonym. — [Dilatator  naris  anterior — Percivall) 

A  single,  short,  and  quadrilateral  muscle,  flattened  before  and  behind, 
applied  to  the  widened  portion  of  the  nasal  cartilages,  and  composed  of 
transverse  fibres  proceeding  from  one  cartilage  to  the  other.  Covered  by  the 
skin  and  the  aponeurotic  expansion  of  the  two  elevator  muscles  of  the  upper 
lip,  the  transverse  muscle  of  the  nose  covers  the  cartilages  to  which  it  is 
attached,  and  is  confounded  below  with  the  orbicularis  of  the  lips. 

Designed  to  bring  together  the  internal  alfe  of  the  nose,  this  muscle 
ought  to  be  considered  more  particulai-ly  as  the  dilator  of  the  nostrils. 


222  THE  MUSCLES. 

10.  The  Middle  (Intermediate)  Anterior  Muscle. 

Synonyms. — Medius  aniarior—Bourgelat.  Myrtiformis  of  Man.  (Depreesor  labii 
superior i—1'ercivall.  Incisive  muscle  of  the  upper  lip — Leyh.  A  portion  of  the 
orbicularis,  according  to  Rigot.) 

Bourgelat  thus  names  a  deeply-situated  muscle  which  is  fixed  to  the 
inner  face  of  the  premaxillary  bone,  above  the  incisor  teeth,  and  whose 
fibres  ascend  to  meet  those  of  the  posterior  portion  of  the  small  super- 
maxillo-nasalis  muscle,  to  terminate  with  them  on  the  anterior  appendix  of 
the  inferior  turbinated  bone ;  some  fibres  become  lost  in  the  lip.  It  is 
regarded  as  a  dilator  of  the  entrance  to  the  nasal  fossa. 

To  study  this  muscle,  it  is  necessary  to  raise  the  upper  lip  and  remove  the  mucous 
membrane  covering  it.  It  may  be  dissected  at  the  same  time  as  the  bony  attachments  of 
the  superficial  plane  of  the  alveolo-labialis  muscle. 

11.  Maxillo-lahialis.     (Fig.  110,  28.) 

Synonyms. — Depressor  labii  inferioris — Rigot.  A  dependency  of  the  buccinator  of 
Man.  (Depressor  lahii  inferioris — Percivall.  Inferior  maxillo-lahialis — Leyh.  Depressor 
anguli  oris  of  Man.) 

Situation — Direction — Form — Structure. — Situated  along  the  inferior 
border  of  the  alveolo-labialis,  whose  direction  it  follows,  this  muscle  forms  a 
long  narrow  fasciculus,  terminating  inferiorly  by  an  expanded  tendon. 

Attachments. — 1,  By  its  superiol*  extremity,  to  the  anterior  border  of 
the  lower  jaw,  in  common  with  the  deep  plane  of  the  alveolo  labialis — fixed 
origin  ;  2,  By  its  terminal  tendon,  to  the  skin  of  the  lower  lip — movable 
insertion. 

Relations. — Outwardly,  with  the  masseter  and  the  facial  portion  of 
cuticularis  of  the  neck ;  inwardly,  with  the  maxillary  bone ;  in  front,  with 
the  alveolo-labialis  muscle,  with  which  it  is  directly  united  in  its  upper  two- 
thirds. 

Actions. — It  separates  the  lower  from  the  upper  lip,  and  pulls  it  to  the 
side  if  one  alone  acts. 

12.  Mento-lahialis  or  Muscle  of  the  Chin.     (Fig.  110,  29.) 

(jSj/Honj/ms.— Percivall  appears  to  describe  this  and  the  next  muscle  as  one.  It  is  the 
quadratus  menti  of  Man.) 

This  name  is  given  to  a  musculo-fibrous  nucleus,  forming  the  base  of  the 
rounded  protuberance  beneath  the  lower  lip  in  front  of  the  beard.  This 
single  nucleus  is  confounded,  in  front,  with  the  orbicularis  of  the  lijjs,  and 
receives  into  its  upper  face  the  insertion  of  the  two  posterior  middle  muscles 
(levatores  menti). 

13.  Middle  (Intermediate)  Posterior  Muscle. 

Synonyms.- -Medina  posterior — Bourgelat.  {Levator  menti — Percivall.  Incisive  musde 
of  the  lower  lip — Leyh.) 

Bourgelat  describes,  by  this  name,  a  small  muscular  fasciculus,  analogous 
in  every  respect  to  the  medius  anterior.  This  little  muscle  takes  its  origia 
from  the  external  surface  of  the  body  of  the  lower  jaw,  beneath  the  inter- 
mediate and  corner  incisors ;  from  thence  it  descends  into  the  texture  of  the 
lip,  to  unite  with  that  of  the  opposite  side  on  the  upper  face  of  the  mento- 
labialis.    Several  authors  have  described  it  as  a  dependent  of  the  last  muscle. 


MUSCLES  OF  THE  HEAD.  223 

It  is  an  energetic  elevator  of  the  lower  lip. 

To  dissect  this  muscle,  tlie  directions  given  for  the  preparation  of  the  anterior  medius 
will  suffice. 

B.  Masseteric  or  Temporo-maxillary  Region. 

This  pair  region  comprises  five  muscles  lor  the  movement  of  the  lower 
Jaw.  These  are  :  the  masseter,  temporal,  internal  pterygoid,  external  pterygoid, 
and  digastricus. 

Preparation. — 1.  First  study  the  digastricus  and  its  stylo  maxillary  portion,  with  the 
internal  pterygoid,  in  preparing  the  hyoid  muscles  as  they  are  represented  in  fig.  111. 
2.  Expose  the  pterygoideus  externus,  by  removing  in  this  preparation  the  hyoid  bone  and 
its  dependencies,  as  well  as  the  two  preceding  muscles.  3.  To  dissect  the  temporalis, 
excise  the  external  pterygoideus  from  its  inferior  border,  an  operation  which  exposes  the 
orbital  fasciculus  of  the  temporalis ;  then  turn  over  the  piece,  saw  oif  the  orbital  process 
at  each  end,  and  remove  the  eye  and  auricular  muscles.  4.  Dissect  the  masseter  in 
clearing  away  from  its  external  surface  the  cuticularis  and  the  vessels  and  nerves  which 
cover  it. 

1.  Masseter.     (Fig.  110,  23.) 
Synonijms. — Zygomatico-maxillaris — Girard.    (^The  zygomatico  maxillaris  of  Leyh.) 

Situation — Form  —Structure. — Aj)plied  against  the  external  face  of  the 
lower  jaw,  the  masseter  is  a  short,  wide,  and  very  thick  muscle,  flattened  on 
both  sides,  irregularly  quadrilateral,  and  formed  of  several  super2)osed  planes, 
two  of  which  are  perfectly  distinct  towards  the  temporo-maxillary  articula- 
tion, by  the  somewhat  different  direction  of  their  fibres.  These  are  divided 
by  a  considerable  number  of  intersections,  and  are  covered  by  a  strong 
aponeui'otic  layer,  which  becomes  gradually  thinner  backwards  and  down- 
wards. 

Attachments. — The  fasciculi  of  the  masseter  have  their  fixed  insertion  on 
the  zygomatic  crest. — Their  movable  insertion  is  on  the  imjjrints  which 
cover  the  upj)er  half  of  the  inferior  maxillary  branch. 

Melations. — It  responds,  by  its  superficial  face,  to  the  facial  portion  of 
cuticularis  colli,  to  the  nerves  of  the  zygomatic  plexus,  and  several  venous 
and  arterial  vessels  ;  by  its  deep  face,  to  the  inferior  maxillary  bone,  the 
alveolo-labialis  and  maxillo-labialis  muscles,  the  superior  molar  glands,  and 
two  large  venous  branches ;  by  its  inferior  border,  with  the  parotid  canal, 
and  the  glosso-facial  artery  and  vein  ;  by  its  superior  and  posterior  border, 
to  the  parotid  gland.  Its  deep  plane  responds,  anteriorly,  with  the  temporo- 
maxillary  articulation,  and  is  so  intimately  confounded  with  the  temporalis, 
that  it  is  impossible  to  define  the  respective  limits  of  the  two  muscles. 

Action. — This  muscle,  the  special  elevator  of  the  lower  jaw,  plays  an 
imj)ortant  part  in  mastication.  It  always  acts  as  a  lever  of  the  third  class, 
the  middle  line,  which  represents  the  resultant  of  all  its  constituent  fibres, 
passing  behind  the  last  molar. 

2.  Temporal  or  Crotaphitic  Muscle. 
5j/no?!?/ms.— Temporomaxillaris— G/rard.     (The  temporo-maxillaris  of  Leyh.) 

Situcdion — Form — Structure. — Situated  in  the  temporal  fossa,  to  which 
it  is  moulded,  and  which  it  fills,  this  muscle  is  flattened  from  above  to 
below,  divided  by  strong  tendinous  intersections,  and  covered  by  a  nacrous 
aponeurotic  layer. 

Attachaents. — It  takes  its  origin:  1,  In  the  temporal  fossa  and  on  the 


221  THE  MUSCLES. 

bony  crests  wtich  margin  it ;  2,  By  a  wide  fasciculus,  paler  than  the  other 
portion  of  the  muscle,  but  not  unconnected  with  it,  from  the  imprints 
situated  behind  the  crest  sui-mounting  the  orbital  hiatus.  It  terminates  on 
the  coronoid  process  and  the  anterior  border  of  the  branch  of  the  lower 
jaw. 

Eclations. — This  muscle  covers  the  temporal  fossa,  and  is  covered  by  the 
temporo-auricularis  muscles,  scutiform  cartilage,  internal  scuto-auricularis, 
the  fatty  cushion  at  the  base  of  the  ear,  and  by  another  adijiose  mass  which 
separates  it  from  the  ocular  sheath.  Its  deep  fasciculus  responds,  by  its 
internal  face,  to  the  two  pterygoid  muscles. 

Action. — It  brings  the  lower  jaw  in  contact  with  the  upper,  by  acting  as 
a  lever  of  the  first  kind ;  but  the  orbital  portion  of  the  muscle  elevates  tho 
inferior  maxilla  and  moves  it  laterally  by  a  lever  of  the  third  class. 

3.  Internal  Pterygoid. 

Synonyms. — Portion  of  the  spheno-maxilliris  of  Bourgelat.  (The pterygoideus  intermts 
of  Percivall.  Leyh  designates  the  pterygoideus  internus  and  externus  as  one  muscle,  the 
spheno-maxillaris  or  internal  masseter.) 

Situation — Form — Structure. — Situated  in  the  intermaxillary  space, 
opposite  the  masseter,  the  pterygoideus  internus,  although  not  so  strong  as 
that  muscle,  yet  so  closely  resembles  it  in  form  and  structure  as  to  be 
named  by  Winslow  the  internal  masseter. 

Attachments. — 1.  To  the  palatine  crest  and  subsphenoidal  process — fixed 
insertion :  2.  In  the  hollow  excavated  on  the  inner  face  of  the  branch  of  the 
lower  jaw — movable  insertion. 

Melations. — Outwardly,  with  the  pterygoideus-externus.  the  orbital 
fasciculus  of  the  temporal,  the  maxillo- dental  nerves,  mylo-hyoideal,  and 
lingual  muscles,  arteries  and  veins,  and  the  inner  surface  of  the  bone  which 
receives  its  movable  insertion.  Inwardly,  with  the  tensors  palati — external 
and  internal,  the  guttural  pouch,  the  hyoideus  magnus,  hyoid  bone,  digastricus, 
the  hypoglossal  and  glosso-pharyngeal  nerves,  glosso-facial  artery  and  vein, 
the  hyoglossus  longus  and  brevis  muscles,  the  laryngo-pharyngeal  aj)paratus, 
the  Stenonian  duct,  and  the  submaxillary  glands. 

Action. — It  is  an  elevator  of  the  lower  jaw,  and  also  gives  it  a  very 
marked  lateral  or  deductive  motion.  If  the  left  muscle  acts,  this  movement 
carries  the  inferior  extremity  of  the  lower  jaw  to  the  right ;  and  if  it  be 
the  right  muscle,  then  in  the  contrary  direction. 

4.  External  Pterygoid. 
Synonym. — ^Portion  of  the  spheno-maxillaris  of  Bourgelat. 

Form — Situation — Structure — Attachments. — A  small,  short,  and  very 
thick  muscle,  situated  within  and  in  front  of  the  temporo-maxillary 
articulation,  formed  of  slightly  tendinous  fasciculi  which  leave  the  inferior 
face  of  the  si)henoid  hone  and  the  subsphenoidal  process,  and  are  directed 
backwards  and  upwards  to  be  fixed  to  the  neck  of  the  inferior  maxill  iry 
condyle. 

Belations. — Outwardly,  with  the  orbital  fasciculus  of  the  temporal 
muscle,  and  the  temporo-maxillary  articulation.  Inwardly,  with  the 
numerous  nerves  emanating  from  the  inferior  maxillary  branch,  and  with 
the  internal  pterygoid  and  tensors  palati. 

Action. — When  the  two  external  pterygoids  act  in  concert,  the  inferior 
maxilla  is  pulled  forward;    but  if  only  one   contract,  the  propulsion  is 


MUSCLES  OF  THE  HEAD.  225 

accompanied  by  a  lateral  m<  )vement,  dui-ing  wliich  the  extremity  of  the  jaw 
is  carried  to  the  opposite  side. 

5.  Digastncus. 

Synonyms. — Boursrelat  has  made  two  distinct  muscles  of  this — the  digastncus  and 
stylo-maxillaris.  Girard  has  described  it  as  the  stylo-maxillaris.  (Percivall  has 
evidently  followed  Bourirtlat's  example,  and  divided  tlie  muscle  into  digadricm  and 
stylo-maxUlaris.     Leyh  adopts  the  same  course.) 

Form — Structure — Situation — Direction. — Composed  of  two  fleshy  bodies 
more  or  less  divided  by  intersections,  and  united  at  their  extremities  by  a 
median  tendon,  this  muscle  is  situated  in  the  intermaxillary  space,  and 
extends  from  the  occiput  to  near  the  symphysis  of  the  chin,  describing  a 
cui've  upwards. 

Attachments. — It  takes  its  origin  from  the  styloid  process  of  the  occipital 
bone,  by  its  superior  fleshy  body.  It  terminates  :  1,  On  the  curved  portion 
of  the  posterior  border  of  the  lower  jaw  by  a  considerable  fasciculus,  which 
is  detached  from  the  superior  fleshy  body  ;i  2,  On  the  internal  face  of  the 
same  bone  and  the  straight  portion  of  its  posterior  border,  by  aponeurotic 
digitations  which  succeed  the  muscular  fibres  of  the  inferior  fleshy  body. 

Belations. — The  superior  belly  of  the  muscle  responds,  superficially,  to 
the  parotid  gland  and  the  tendon  of  insertion  of  the  sterno-maxillaris ; 
deeply,  to  the  guttural  pouch,  the  submaxillary  gland,  and  the  larynx  and 
pharynx.  The  median  tendon  passes  through  the  ring  of  the  hyoideus 
magnus.  The  lower  belly  is  in  contact,  outwards,  with  the  ramus  of  the 
inferior  maxilla ;  inwards,  with  the  mylo-hyoideus  muscle. 

Action. — When  this  muscle  contracts,  it  acts  at  the  same  time  on  the 
hyoid  bone,  which  it  raises  in  becoming  straight,  and  on  the  lower  jaw, 
which  it  pulls  backwards  and  depresses  at  the  same  time. 

C.  Hyoideal  Region. 

This  region  includes  six  muscles  grouped  around  the  os  hyoides,  which 
they  move.  Five  of  these  are  pairs  :  the  mylo-hyoideus.  genio-hyoideus,  sfylo- 
hyoideus,  herato  hyoideus,  and  the  occipito-styloideus.  The  single  one  is  the 
transversalis  hyoiclei. 

Preparation. — Separate  the  head  from  the  trunk,  and  remove  the  muscles  of  the 
cheeks  on  one  side,  with  the  parotid  gland.  2.  The  branch  of  the  inferior  maxilla  being 
thus  exposed,  it  is  sawn  through  in  two  places ;  at  first  behind  the  last  molar,  then  in 
front  of  the  first.  3.  After  having  separated  the  pterygoids  and  the  stylo-maxillaris 
from  the  upper  fragment  or  condyle,  and  the  coronoid  process,  it  is  torn  ofl"  by  pulling 
it  backwards ;  then  the  pterygoiiis  and  the  digastricus  are  excised.  4.  The  inferior  fragment 
of  the  jaw  bearing  the  molar  teeth  is  turned  down  V)y  isolating  the  mylo-hyoideus  from  the 
mucous  membrane.  5.  Carefully  remove  the  tongue  by  separating  its  extrinsic  muscles 
from  the  genio-hyoideus,  the  anterior  appendix  of  the  hyoid  bone,  the  transverse  muscle, 
and  the  small  hyoideus. 

The  dissection  having  been  performed  in  this  manner,  the  large  hyoideal  branch  may 
be  separated  from  the  small,  by  sawing  thronuh  the  head  longitudinally,  leaving  the 
symphysis  menti  intact,  and  turning  down  the  corresponding  half  to  the  side  already 
dissected,  as  well  as  the  great  hyoid  branch,  the  pharynx,  larynx,  and  soft  palate. 

1.  Mylo-hyoideus. 

Form — Situation — Structure. — A  membranous  muscle  situated  in  the 
intermaxillary  space,  flattened  from  side  to  side,  elongated  in  the  dii-ection 


>  This  is  the  fasciculus  which  Bourgelat  has  described  as  a  distinct  muscle,  and 
named  the  stylo-maxiUaris, 


226 


THE  MUSCLES. 


of  the  head,  thinner  and  narrower  below  than  above,  and  formed  entirely  of 
fleshy  fibres  which  extend  transversely  from  its  anterior  to  its  posterior 
border.  Inferiorly,  it  is  composed  of  a  small  fasciculus,  which  is 
distinguished  from  the  princiijal  portion  by  the  slightly  different  direction 
of  its  fibres,  and  which  covers  in  part  the  external  surface  of  the  muscle. 

Fig.  11] 


HYOIDEAL    AND    PHARYNGEAL    REGIONS. 

1,  Neck  of  inferior  maxilla  ;  2,  Hard  palate  ;  3,  Molar  teeth  ;  4,  Buccal  membrane  ;  5, 
Submaxillary  glands;  6,  Soft  palate;  7,  Tendon  of  hyoideus  magnus  through 
which  the  tendon,  8,  of  ;he  digastricus  passes;  9,  Lower  portion  of  digastncus; 
10,  Stylo-hyoideus ;  11,  Buccal  nerve;  12,  Zygomatic  arch ,  13,  Orbital  branch 
of  fifth  pair  of  nerves ;  14,  Articular  process  of  temporal  bone ;  15,  Right  cornu  of 
hyoid  bone  ;  16,  Hyo-glossus  longus,  or  Kerato-glossus  ;  17,  Lingual  nerve  ;  18,  18, 
Tongue ;  19,  Angle  of  left  branch  of  mferior  maxilla ;  20,  Submaxillai-y  gland, 
left  side;  21,  Subscapulo-hyoideus ;  22,  Great  hypoglossal  nerve;  23,  Hyo- 
thyroideus ;  24,  Sterno-hyoideus ;  25,  Stei'no-thyroideus ;  26,  Subscapulo  hyoi- 
deus ;  27,  Thyroid  gland  ;  28,  External  carotid  artery  ;  29,  Pneumogastric  nerve ; 
30,  Stylo-hyoideus  ;  31,  Genio-hyoideus. 


Attachments. — It  originates  from  the  mylo-hyoid  line  by  the  anterior 
extremities  of  its  fibres.  Its  movable  insertion  takes  place  on  the  inferior 
face  of  the  hyoid  body,  on  its  anterior  appendix,  and  on  a  fibrous  raphe  which 
extends  from  the  free  extremity  of  this  appen-dix  to  near  the  genial  surface, 
and  which  unites,  on  the  median  line,  the  two  mylo-hyoideau  muscles. 

JRelations. — By  its  external  face,  with  the  inferior  maxilla,  the  digastric 
muscle,  and  the  submaxillary  lymphatic  glands,  B}'  its  internal  face,  with 
the  sublingual  gland,  the  Whartonian  duct,  the  hypoglossal  and  lingual 
nerves,  the  genio-glossus,  hyo-glossus  longus  and  brevis,  and  genio-hyoideus. 
Its  superior  border  responds  to  the  internal  pterygoid. 

Action. — In  uniting  on  the  median  line  with  that  of  the  opposite  side, 
this  muscle  forms  a  kind  of  wide  band  or  brace  on  which  the  tongue  rests. 
When  it  contracts,  it  elevates  this  organ,  or  rather  applies  it  against  the 
palate. 

2.    Genio-hyoideus. 

Form — Structure — Situation. — A  fleshy,  elongated,  and  fusiform  body, 
tendinous  at  its  extremities,  but  especially  at  the  inferior  one,  and  applied, 
with  its  fellow  of  the  opposite  side,  to  the  mylo-hyoidean  brace. 


MUSCLES  OF  THE  HEAD.  227 

Attachments. — By  its  inferior  extremity  it  is  fixed  to  the  genial  surface — 
origin  ;  by  its  superior,  it  reaches  the  free  extremity  of  the  anterior  appendix 
of  the  hyoid  body — tenninadon. 

Belations. — Outn-ards  and  downwards,  with  the  mylo-hyoideus  ;  inwards, 
with  its  fellow,  which  is  parallel  to  it ;  above,  with  the  genio-glossus. 

Action. — It  draws  the  hyoid  bone  towards  the  anterior  and  inferior  part 
of  the  intermaxillary  space. 

3.  Sfylo-hyoideus. 
(^Synonyms. — The  hyoideus  magnus  o/Percivall.    The  kerato-hyoideus  magnus  of  Leyh.) 

Form  —  Structure  —  Situation  —  Direction  —  Thin  and  fusiform,  this 
muscle,  smaller  than  the  preceding,  and,  like  it,  tendinous  at  both  its 
extremities,  is  situated  on  the  side  of  the  laryngo-pharyngeal  ai:)paratus  and 
the  guttural  pouch,  behind  the  large  branch  of  the  hyoid  bone,  whose 
direction  it  follows. 

Attachments. — Above,  to  the  superior  and  posterior  angle  of  the  styloid 
hone^Ji.ved  insertion;  below,  to  the  base  of  the  cornu  of  the  os  hyoides 
— movahJe  insertion. 

Belations. — Outwards,  with  the  pterygoideus  internus;  inwards,  with 
the  guttural  pouch,  the  pharynx,  and  hypoglossal  nerve.  Its  anterior 
border  is  separated  from  the  posterior  border  of  the  styloid  bone  by  the 
glosso-facial  artery  and  glosso-pharyngeal  nerve ;  along  the  posterior 
border  lies  the  upper  belly  of  the  digastricus.  Its  inferior  tendon  is 
perforated  by  a  ring  for  the  passage  of  the  cord  intermediate  to  the  two 
portions  of  the  latter  muscle. 

Action. — It  is  antagonistic  to  the  preceding  muscle,  drawing  the  body  of 
the  hyoid  bone  backwards  and  upwards. 

4.  Kerato-hyoideus. 

{Synonyms.— This  is  the  hyoideus  parvus  of  Percivall,  and  the  smdl  kerato-hyoideus  of 
Leyh) 

A  very  small  fasciculus,  triangular  in  shape,  and  flattened  on  both  sides. 
Inserted,  on  one  side,  into  the  posterior  border  of  the  styloid  cornu  and  the 
inferior  extremity  of  the  styloid  bone ;  and  on  the  other,  to  the  superior 
border  of  the  thyroid  cornu.  It  responds,  outwardly,  to  the  basio-glossus 
and  the  lingual  artery ;  inwardly,  to  the  buccal  mucous  membrane. 

It  approximates  the  cornua  of  the  os  hyoides  to  each  other. 

5.  Occipito-styloideus. 

Synonyms. — Tliis  is  the  muscle  which,  up  to  the  present  time,  has  been  described  by 
veterinary  anatomists  as  the  siyh-hyoidem.  This  name  has  been  given  to  the  muscle 
nam£d  by  Girard  the  kerato-hyoideus  magnus. 

A  small,  flat,  and  triangular  muscle  like  the  preceding,  yet  thicker  and 
more  spread,  filling  the  space  comprised  between  the  styloid  process  of  the 
occipital  and  the  horizontal  portion  of  the  posterior  border  of  the  styloid 
bone.  Its  fasciculi  become  longer  as  they  are  situated  posteriorly,  are 
rather  tendinous,  and  are  carried  from  one  of  these  bones  to  the  other. 
Outwardly,  it  responds  to  the  parotid  gland ;  inwardly,  to  the  guttural 
pouch,  which  it  covers  for  its  whole  extent ;  its  posterior  border  is  largely 
confounded  with  the  superior  insertion  of  the  digastricus.  "When  this 
muscle  acts,  it  causes  the  os  hyoides  to  swing,  carrying  its  inferior  extremity 
backwards  and  downwards. 


228 


THE  MUSCLE 
6.  Transversalis  Hyoidei. 


By  this  name  Bourgelat  has  described  a  short  riband  of  parallel  muscular 
fibres,  which  unites  the  superior  extremities  of  the  styloid  coruua,  and 
approximates  them  to  each  other. 

DIFFERENTIAL   CHARACTERS  OF  THE  MUSCLES  OF  THE   HEAD   IN  OTHER   THAN   SOLIPED 

ANIMALS. 

A.  Facial  Region. 
EuMiNANTS. — There  are  found  in  the  Ox  . 

1.  An  orbicular  muscle  of  the  lips,  analogous  to  that  in  the  Horse. 

2.  An  alveolo-labialis  of  the  same  kind  (fig.  112,  5). 

3.  A  zyqomaticus  or  zygomatico-lahiahs,  stronger  and  redder  than  in  Solipeds. 
Its  aponeurosis  of  origin,  covered  by  the  cuticularis  muscle  of  the  face,  extends  upon, 
the  surface  of  the  masseter  muscle  as  far  back  as  the  zygomatic  arch,  to  which  it  is 
attached  (fig.  112,  7). 

Fi2.  112. 


SUPERFICIAL   MUSCLES   OF   THE   OX's    HEAD. 

1,  Supermaxillo-labialis ;  1,  1',  Accessory  fasciculi  of  the  superma.xillo-labialis ; 
2,  Supermaxillo-nasalis  inas;nus ;  3,  Supernaso-labialis ;  4  Lachrymalis ;  5, 
Alveolo-labialis;  (3.  Maxillo-labialis  confounded  with  the  preceding;  7,  Zygo- 
matico-labialis ;  8,  Frontal,  or  cuticularis  muscle  of  the  forehead ;  9,  Orbicular 
muscle  of  the  eyelids;  10,  Zygomatico-auricularis  ;  11,  External  temporo-auricu- 
laris;  12,  Scutiform  cartilage;  1,5,  External  scuto-auricularis ;  14,  Mastoid 
process;  15,  Masseter;  16,  Stylo-hyoideus ;  17,  Digastricus ;  18,  Sterno-maxil- 
lary  fasciculus  belonging  to  the  cuticularis  muscle  of  the  neck ;  19,  Trachelo- 
hyoideus  (subscapulo-hyoideus) ;  20,  Sterno-suboccipitalis  (sterno-maxillaris, 
or  mastoideus);  21,  Anterior  branch  of  the  superficial  portion  of  the  mastoido- 
humeralis  (levator  humeri);  22,  Superior  branch  of  ditto;  23,  Deep  portion  of 
same  muscle;  24,  Trachelo-atloideus,  peculiar  to  Ruminants  and  Pachyderms; 
25,  Great  anterior  straight  muscle  of  the  head. 


MUSCLES  OF  TEE  HEAD.  229 

4.  A  laclirymalis,  thicker  and  more  developed  than  in  the  Horse.  Its  most  anterior 
fibres  glide  beneath  the  zygomaticus.  and  are  lost  on  the  alveolo-labialis  surface :  tlie 
most  posterior  pass  over  the  aponeurotic  tendon  of  the  zygomatico-labialis,  and  are 
confounded  M'ith  those  of  the  cuticuhiris.  Above,  it  joins  the  orbicularis  of  the  eyelids 
in  a  still  more  intimate  manner  than  in  the  Horse ;  so  that  it  is  ahnost  impossible  to 
distinguish  the  limits  of  the  two  muscles  (iig.  112,  4). 

5.  A  swpernaso-lahialis  continued,  above,  with  tlie  inferior  border  of  the  frontal  or 
fronto-cuticularis  muscle;  and  divided,  inferiorly,  into  two  branches,  which  comprise 
between  them  the  supermaxillo-labialis  and  the  pyramidalis-na^alis.  These  two 
branches,  however,  are  not  disposed  as  in  Solipeds,  the  anterior  covering  the  preceding 
muscles,  and  the  posterior,  of  but  little  importance,  passing  beneath  them  to  lose  itself 
in  the  substance  of  the  upijcr  lip  (fig.  112,  3). 

6.  A  sirpermaxiUo-Iabiah's,  Avliicli  gains  the  middle  of  the  muzzle  by  jjassing  along 
the  inner  side  of  the  nostrils  (tig.  112.  1). 

7.  Two  additional  t<uperntaxiUo-lahialis  muscles,  considered  as  accessories  to  the 
first,  and  wliich  originate  with  it.  Each  terminates  by  a  ramifying  tendon  that  jmsses 
mider  the  nostril  to  mix  in  the  tissue  of  the  upper  lip  (tig.  112,  l',l'). 

8.  A  pyramidalis  or  great  super maxiUo-nasulls,  situated  between  the  supermaxillo- 
labialis  and  its  two  accessory  muscles,  and  deriving  its  origin,  in  common  with  these 
tkree  muscles,  in  front  of  the  maxillary  spine  (fig.  112,  2). 

9.  A  maxillo-lahialis,  confounded  with  the  alveolo-labialis,  and  having  no  terminal 
tendon. 

10.  A  mento-lah'alis,  attached  to  the  body  of  the  inferior  maxillary  bone,  as  in  the 
Horse,  by  two  middle  posterior  muscles.  No  anterior  middle  muscle  has  been  found  by 
us;  and  it  is  certain  that  there  is  no  naso-transversalis  or  small  supermaxillo-nasalis 
present. 

In  the  Sheep,  the  supernaso-labialis  does  not  exist ;  apart  from  this  peculiarity, 
there  is  no  diflference  between  the  facial  muscles  of  this  animal  and  the  Ox. 

Pig. — This  animal  has  neither  the  laclirymalis,  supernaso-labiali»,  or  naso-transver- 
salis muscles.  The  small  supermaxillo-nasalis  is  present ;  it  is  short,  very  thick,  and 
situated  near  the  margin  of  the  nostrils.  The  supermaxillo-lahialis  and  the  great 
supermaxillo-nasalis  are  replaced  by  three  fleshy  bodies,  nearly  parallel,  lying  on  the 
side  of  the  face.  The  superior  originates  in  the  lachrymal  fossa,  and  terminates  by  a 
tendon  in  the  middle  of  the  snout.  The  inferior,  with  the  middle,  leaves  the  imprints 
in  front  of  the  zygomatic  riilge,  and  is  continued  at  its  inferior  extremity  by  a  tendon 
divided  into  several  fibrillse,  which  pass  below  the  nostril  to  be  united  to  the  tendon  of 
the  superior  portion  :  this  is  done  in  such  a  manner  that  the  external  opening  of  the 
nose  is  encircled  on  the  inner  side  by  a  kind  of  fibrous  cravat  which,  when  these  two 
muscles  contract,  carries  this  opening  outwards.  It  will  also  be  understood  that  the 
superior  fleshy  body,  acting  alone,  ought  to  elevate  the  snout,  while  the  inferior 
depresses  it  in  drawing  it  to  one  side.  With  regard  to  the  intermediate  fleshy  mass,  it 
is  the  representative  of  the  i^yramidalis  of  t lie  Ox,  and  terminates  in  a  great  quantity  of 
tendinous  fibrilliB  at  the  internal  ala  of  the  nose. 

Carnivora. — In  the  Dog  and  Cat  the  following  peculiarities  are  found  : — 

The  lahialis  (or  orbicularis)  is  quite  rudimentary. 

The  buccinator  is  very  tliin  and  formed  of  only  one  muscular  plane. 

The  zygomatico-labialis  is  continued,  superiorly,  with  the  zygomato-auricuralis. 

The  supernaso-labialis  represents  a  wide,  undivided,  muscular  expansion,  united 
superiorly  to  the  cuticularis  of  the  forehead,  and  terminating  inferiorly  on  the  upper 
lip. 

The  supermaxillo-labialis  and  the  supermaxillo-nasalis  magnus  constitute  a  single 
fleshy  body  formed  of  several  parallel  fasciculi,  wliich  take  their  origin  above  the  supra- 
orbital foramen,  and  terminate  together  at  the  external  wing  of  the  nose  and  in  the 
upper  lip. 

There  is  no  supermaxillo-nasalis  parvus,  or  naso-transversalis. 

The  middle  anterior  (depressor  al-e  nasi)  is  ]ierfectly  developed. 

The  mento-labialis  and  its  suspensory  muscle,  the  middle  posterior,  are  scarcely 
apparent. 

B.  Masseteric  or  Temporo-maxillary  Region. 

In  Buminants,  the  massefer  and  temporal  are  not  so  large  as  in  Solipeds.    In  the 

Carnivora,  however,  they  offer  a  remarkable  development.     The  origin   of  the  pdery- 

goideus  internus  in  Ruminants  is  nearer  the  middle  line  than  in  the  Horse.    Its  obliquity 

si  also  greater,   and  the   movements  of  diduction  it  gives  the  low^er  jaw  are  more 

18 


230  THE  MUSCLES. 

extensive.  la  all  the  animals,  the  stylo-maxillaris  fasciculus  of  the  digastricus  is 
entirely  absent,  and  the  muscle  has  only  a  single  belly  extending  directly  from  the 
occipital  to  the  maxillary  bone.  In  the  Ox  is  foimd  a  small  square  muscle,  formed  of 
transverse  fibres,  which  unites  the  two  digastric  muscles  by  passing  beneatli  the  base  of 
the  tongue.  This  muscle,  in  contracting,  may  raise  the  hyoideal  apparatus,  and  in  this 
way  supplements  the  tendon  of  the  digastricus  and  the  inferior  ring  of  the  stylo- 
hyoideus. 

C.  Eyoid  Region. 

The  two  fleshy  planes  composing  the  mijlo-hyoideus  are  more  distinct  in  Iiuminants 
than  in  the  Horse.  Tue  stylo-hyoideus  of  these  animals  commences  by  a  long  thin 
tendon.  The  muscle  has  no  ring  for  the  passage  of  the  digastricus,  a  feature  observed 
in  all  the  domesticated  animals  except  Solipeds. 

In  the  Carnivora,  the  stylo-hyoideus,  formed  by  a  narrow,  very  thin,  and  pale 
fleshy  band,  commences  on  the  mastoid  portion  of  the  temporal  bone  by  a  small  tendon; 
the  kerato-liyoideus  is  remarkable  for  its  relatively  considerable  volume  ;  tlie  occipito- 
slyloideus  and  the  transversalis  hyoideus  are  absent. 

COMPARISOX   OF   THE  Mt'SCLES   OF   THE   HUMAN   HEAD   WITH   THOSE   OF  THE   DOMESTICATED 

ANIMALS. 

In  Man,  there  are  described  as  musdes  of  the  head,  the  epicranial  muscles,  muscles  of 
the  face,  and  ihose  of  the  toiver  jaw.  The  hyoid  and  digastric  muscles  are  reckoned  in 
the  region  of  the  neck.    Here  they  will  be  placed  in  the  region  of  the  head. 

A.  Epicranial  Muscles. 

The  middle  portion  of  the  human  cranium  is  covered  by  an  aponeurosis  that  adheres 
closely  to  the  hairy  scalp,  but  glides  easily  on  the  siu-face  of  the  bones.  To  the  circiun- 
fereuce  of  this  epicranial  aponeurosis  are  attached  four  muscles  which  move  it.  One 
of  them,  attached  behind  to  the  superior  occipital  curved  line,  is  named  the  occipital 
muscle  ;  another,  fixed  in  front  of  the  forehead,  is  called  the  frontal  muscle ;  the  other  two, 
double  and  lateral,  are  inserted  on  the  face  of  the  temporal  bone  or  the  external  ear, 
and  are  designated  auricular  muscles.  These  epicranial  muscles  move  the  scalp  for- 
wards, backwards,  and  sideways. 

B.  Muscles  of  the  Face. 

These  are  fourteen  in  number,  ten  of  which  are  found  in  the  domesticated  animals. 
We  commence  by  describing  these  common  muscles  (fig.  113). 

1.  The  orbicularis  of  the  lips,  which  has  a  fasciculus  that  passes  to  the  skin  from  the 
columna  of  the  nose ;  this  fasciculus  is  termed  the  depressor  of  the  columna,  or 
moustache  muscle  (^naso  lahialis). 

2.  The  buccinator,  corresponding  to  the  alveolo-labialis  of  animals.  Besides  its  office 
in  mastication,  it  takes  an  important  part  in  the  blowing  of  wind  instruments. 

3.  The  superficial  elevator  of  the  wing  of  the  nose  and  the  upper  lip.  It  resembles  the 
supernaso-labialis,  descends  from  the  orbital  margin  of  the  supermaxilla,  passes  along 
the  wing  of  the  nose,  and  is  lost  in  the  upper  lip. 

4.  The  deep  elevator  of  the  tviiig  of  the  nose  and  the  upper  lip,  whose  analogue  is 
found  in  the  supermaxillo-labialis  of  animals. 

5.  The  great  zygomaticus,  whose  presence  is  constant  in  all  species. 

6.  The  ^smcdl  zygomaticus.  represented  in  the  Horse  by  only  the  small  oblique 
fasciculus  sometimes  found  beneath  the  great  zygomaticus. 

The  small  zygomaticus  and  the  two  elevators  of  the  lips  are  lachrymal  muscles ;  by 
their  simultaneous  cnutraction  they  express  discontent  and  melancholy.  The  great 
zygomaticus,  on  the  contrary,  is  the  muscle  of  laughter;  it  draws  the  commissures  of 
tlie  lips  outwards. 

7.  The  canine,  or  great  supermaxillo-nasal  of  animals,  is  attached  beneath  the  infra- 
orbital foramen,  and  terminates  in  the  skin  of  the  upper  lip. 

8.  The  rtsorius  of  Santorini. 

9.  The  muscle  of  the  chin  (m/'ntodabiaUs). 

10.  The  myrtiformis,  or  middle  anterior  of  Bourgelat. 

The  otiier  "facial  muscles  of  Man,  whose  analogues  it  is  difficult  or  impossible  to  find 
in  animals,  are : — 


MUSCLES  OF  THE  TRUNK. 


231 


11.  The  triangularis  of  (he  lips,  \vhich  is  inserted  into  the  anterior  face  of  tl 


inferior  maxilla,  and  is  carried  upwards  to  the 
commissure  of  the  lips.  Bj-  its  contraction  it 
gives  the  face  an  expression  of  melancholy  or 
contempt. 

12.  The  quadratus  menti,  which,  after  being 
attached  to  tlie  maxilla  within  the  mental  fora- 
men, passes  upwards  on  the  skin  of  the  lower 
lip,  which  it  depresses,  and  thus  contributes  to 
the  expression  of  fear  or  dismay. 

13.  The  fransversalis  nasi  {compressor  nasi), 
a  muscle  which  is  fixed  into  the  supermaxilla 
and  on  the  bridge  of  the  nose,  where  it  is  con- 
founded with  the  opposite  muscle. 

14.  The  dilator  of  the  ala  of  the  nostril,  a 
very  small  triangular  fasciculus  applied  to  the 
external  part  of  the  nostril,  which,  by  contract- 
ing, it  elevates. 

C.  Muscles  of  the  Lower  Jaw. 

Tiiere  is  nothing  remarkable  to  be  noted  in 
the  masseter,  temporal,  or  pterygoid  muscles. 
The  upper  belly  of  the  digastricus  is  not  at- 
tached directly  to  the  inferior  maxilla. 

D.  Byoid  Muscles. 

These  are  only  three  in  number: — 

1.  The  mylo-hyoideus. 

2.  The  stylo-hyoideus,  which  commences  at 
the  styloid  process  of  the  temporal  bone,  and 
shows  a  ring  for  the  tendon  of  the  digastricus. 

3.  The  genio-hyoideus. 

We  do  not  find  in  Man  the  occipito-styloideTis, 
kerato-hyoideus,  or  the  transversalis-byoideus. 

Axillary  Region. 

This  comprises  two  muscles,  pairs, 
placed  beneath  the  sternum,  in  the  arm- 
pit, which  terminate  on  the  anterior  limb. 
These  are  the  superficial  and  deep  pec- 
torals.^ 


Fis:.  113. 


MTSCLES  OF   THE   HUMAN   HEAD  ; 
SUPERFICIAL   LAYER. 

1,  Frontal  portion  of  the  occipito-fronta- 
lis ;  2,  Its  occipital  portion ;  o.  Its 
aponeurosis  ;  4,  Orbicularis  palpebra- 
rum ;  5,  Pyramidalis  nasi,  6,  Com- 
pressor nasi ;  7,  Orbicularis  oris ;  8, 
Levator  labii   superioris  alseque  nasi ; 

9,  Levator    labii  superioris  proprius , 

10,  Zygomaticus  minor;  11,  Zygo- 
maticus  major;  12,  Depressor  labii 
inferioris ;  13,  Depressor  anguh  oris; 
14,  Levator  labii  inferioris;  15,  Super- 
ficial portion  of  masseter;  16,  Its  deep 
portion;  17,  Attrahens  aurem ;  IS, 
Buccinator;  19,  AttoUens  aurem;  20, 
Temporal  fascia  covering  temporal 
muscle ;  21,  Retrahens  aurem ;  22, 
Anterior  belly  of  the  digastricus,  with 
tendon  passing  through  pulley ;  23, 
Stylo-hyoid  muscle ;  24,  Mylo-hyoi- 
deus ;  25,  Upper  part  of  sterno-mas- 
toid ;  26,  Upper  part  of  trapezius — 
the  muscle  between  25  and  26  is  the 
splenius. 


Preparation. — 1.  Place  the  animal  in  the 
first  position.  2.  Unfasten  one  of  the  fore-limbs, 
and  allow  it  to  hang,  so  as  to  separate  it  from 
the  opposite  one.  3.  Remove  the  skin  with 
care,  and  dissect,  on  the  side  corresponding  to 
the  detached  limb,  the  two  muscles  which  form 
the  superficial  pectoral.  4.  Prepare  the  deep 
pectoral  on  the  opposite  side.  To  do  tliis, 
remove  the  panniculus  cautiously,  so  as  not  to  injure  the  muscle  about  to  be  examined ; 
divide  the  superficial  pectoral  transversely,  and  turn  back  the  cut  portions  to  the  right  and 
left ;  divide  also  the  mastoido-liumeralis  (levator  humeri)  and  cervical  trapezius  ne<ir 
their  insertion  into  the  limb,  and  reflect  them  upon  the  neck. 

1.  Superficial  Pectoral.     (Tig.  114,  9,  10.) 

iPj/noHj/fHs.— 3Iu.=cle  common  to  the  ann  and  fore-arm — Bourgelaf.  Pectoralis  magnus 
of  Man.  (Pectoralis  transversus — Percivall.  Leyh  divides  this  muscle  into  two  portions, 
which  he  desigua'es  the  sterno-radialis  and  small  sterno-humeralis). 


F  r  a  justification  of  the  employment  of  these  new  denominations,  see  the  note 
at  p.  177. 


232 


THE  MUSCLES. 


MUSCLES  OP   THE   AXILLARY   AND 
CERVICAL  REGIONS. 

1,  Portion  of  the  cuticularis  colli ;  2,  An- 
terior portion  of  the  mastoido-hume- 
ralis  ;  3,  Posterior  portion  of  ditto  ;  4, 
Sterno-maxillaris ;  5,  Subscapulo-hyoi- 
deus ;  6,  Sterno-hyoideus ;  7,  Sterno- 
thyroideus;  8,  Scalenus;  9,  Sterno- 
humeralis ;  10,  Sterno-aponeuroticus  -, 
11,  Sterno-trochineus  (pectoralis  naag- 
nus);  12,  Portion  of  the  fascia  en- 
veloping the  coraco-i-adialis,  receiving 
part  of  the  fibres  of  the  sterno-trochi- 
neus;  13,  Sterno-prescapularis ;  14, 
Its  terminal  aponeurosis. 


Situation — Comjjosition. — This  muscle 
is  situated  between  the  two  anterior 
limbs,  occupies  the  inferior  surface  of 
the  chest,  and  is  formed  by  two  por- 
tions which  adhere  closely  to  each  other, 
but  are  yet  perfectly  distinct.  Following 
the  example  of  Girard,  we  will  describe 
these  as  two  particular  muscles  by  the 
names  of  sterno-humeralis,  and  sterno- 
aponeuroticus. 

A.  Sterno-humeralis.  —  Form  — 
Structure. — This  is  a  short,  bulky  muscle, 
flattened  above  and  below,  contracted  at 
its  termination,  and  comi^osed  almost 
entirely  of  thick  parallel  fibres. 

Direction  and  Attachments. — It  com- 
mences on  the  anterior  appendage  and  the 
inferior  border  of  the  sternum,  and  is 
directed  obliquely  backwards,  downwards, 
and  inwards,  to  reach  the  anterior  ridge 
of  the  humerus,  where  it  teiminates  by 
an  ajioneurosis  common  to  it,  the  mas- 
toido  humeralis,  and  the  sterno-aponeuro- 
ticus. 

Belations. — It  responds,  by  its  ex- 
ternal face,  to  the  skin,  from  which  it  is 
separated  by  a  cellular  layer,  and  to  the 
inferior  extremity  of  the  cuticularis 
colli ;  by  its  internal  face,  to  the  sterno- 
aponeuroticus  and  sterno-prescapularis. 
Its  anterior  border  forms,  with  the  mas- 
toido-humeralis,  a  triangular  space  occu- 
pied by  the  subcutaneous,  or  "  plate,"  vein 
of  the  arm. 

Action. —  It  acts  principally  as  an 
adductor  of  the  anterior  limb. 

B.  Stekno-aponeurotictts. — Form — 
Structure  —  Direction  —  Attachments.  — A 
very  wide,  thin,  and  pale  quadrilateral 
muscle  formed  of  parallel  iieshy  fibres, 
which  arise  from  the  entire  inferior 
border  of  the  sternum,  to  pass  at  first 
outwards,  then  downwards,  and  terminate 
in  the  following  manner :  the  anterior 
fibres  go  to  the  aponeurosis  which  attaches 
the  mastoido-humeralis  and  sterno-hu- 
meralis to  the  anterior  ridge  of  the 
humerus ;  the  posterior  fibres  are  also 
continued  by  a  very  thin  fascia,  wliich  is 
spread  inside  the  limb  to  the  external 
face  of  the  antibrachial  aponeurosis. 

Belations. — By    its    superficial    face, 


MUSCLES  OF  THE  TRUNK.  233 

with  the  skin,  which  adheres  intimately  to  it  by  means  of  a  dense  cellular 
tissue,  and  with  the  steruo-humeralis,  which  covers  its  anterior  border. 
By  its  deep  face,  with  the  two  portions  of  the  deep  pectoral,  the  coraco- 
radialis  (flexor  brachii),  and  the  long  extensor  of  the  fore-arm;  it 
also  responds,  by  this  face,  to  the  antibrachial  aponeurosis  and  the  sub- 
cutaneous vein  of  the  fore-arm,  which  it  maintains  applied  against  that 
aponeurosis. 

Action. — It  is  an  adductor  of  the  anterior  limb,  and  a  tensor  of  the 
antibrachial  apoueui-osis. 

2.  Deep  Pectoral.     (Figs.  114,  11,  13;  115,  1.) 
Synonym. — The  pectoraUs  parvus  of  Man. 

Volume — Situation — Composition. — An  enormous  muscle,  situated  be- 
neath the  thorax,  and  composed,  like  the  preceding,  of  two  perfectly  distinct 
portions,  described  by  Grirard  as  two  muscles,  and  designated  by  him  as  the 
sterno-trocTiineus  and  sterno-preseapularis. 

A.  Stekko-trochixeus. — Pectoralis  magnus  of  (Percivall,  Eigot,  and) 
Bourgelat.     (The  great  sterno-humeralis  of  Leyh.) 

Volume — Extent. — This  muscle,  the  largest  of  the  two,  offers  a  con- 
siderable volume.  Extending  from  the  ninth  or  tenth  rib  to  the  upper 
extremity  of  the  arm,  it  at  fii-st  lies  beneath  and  against  the  abdomen,  then 
beneath  the  chest,  and  at  last  is  comprised  between  the  walls  of  the  latter 
cavity,  and  the  internal  face  of  the  anterior  limb. 

Form. — It  is  thin  and  flat  above  and  below  in  its  posterior  third,  thicker 
and  depressed  from  side  to  side  in  its  middle  third,  and  narrow  and  pris- 
matic in  its  anterior  third.  Its  general  form  may  be  compared  to  that  of  a 
somewhat  irregular  triangle,  elongated  from  before  to  behind,  which  would 
have  a  very  short  posterior  border,  a  longer  internal  or  inferior  border,  and 
an  external  or  superior  still  more  extensive. 

Structure. — It  is  entirely  composed  of  thick,  parallel,  fleshy  fasciculi,  all 
of  which  leave  the  posterior  or  internal  border  of  the  muscle  to  gain  its 
narrow  or  anterior  extremity.  These  fasciculi,  as  they  ajiproach  the  superior 
border,  become  longer,  and  those  which  proceed  from  the  posterior  border  com- 
mence hy  aponeui'otic  fibres.  Unfrequent  intersections  of  fibrous  tissue 
exist  towards  the  anterior  extremity  of  the  muscle. 

Attachments. — It  originates  :  1,  From  the  tunica  abdominalis  by  the  apo- 
neurotic fasciculi  of  its  posterior  border  ;  2,  By  its  internal  border,  from  the 
posterior  two-thirds  of  the  inferior  border  of  the  sternima.  It  terminates,  by 
its  anterior  extremity,  on  the  internal  tubercle  at  the  head  of  the  humerus, 
the  tendon  of  origin  of  the  coraco-humeralis,  and  the  fascia  envelopinff  the 
coraco-radialis.  Through  the  medium  of  this  fascia,  it  is  inserted  into  the 
external  lip  of  the  bicipital  groove  formed  by  the  great  trochanter,  and  is 
united  to  the  two  terminal  branches  of  the  supraspinatus  muscles.  (See 
Fig.  114,12.) 

Relations. — Its  deep  face,  which  is  successively  superior  and  internal, 
covers  the  external  oblique  and  the  straight  muscle  of  the  abdomen,  the 
serratus  magnus,  costo-sternalis,  and  sterno-preseapularis,  as  well  as  some 
thoraco-muscular  nerves ;  all  these  relations  are  maintained  by  means  of  a 
loose  and  abundant  cellular  tissue.  Its  superior  face,  which  alternately 
looks  downwards  and  outwards,  responds :  to  the  skin,  from  which  it  is 
separated  by  a  slight  cellulo-fibrous  fascia ;  to  the  sterno-aponem-oticus ; 
and  to  the  muscles,  vessels,  and  nerves  of  the  inner  aspect  of  the  arm,  through 


23i 


THE  MUSCLES. 


the  medium  of  the  subbrachial  aponeurosis  of  the  panniculus  and  a  con- 
siderable quantity  of  cellular  tissue.  Its  upper  border  adheres  in  an  intimate 
manner  to  the  last-named  muscle,  and  is  bordered  by  the  spur  (external 
thoracic)  vein.     The  large  vascular  trunks  which  leave  the  chest  to  reach 


the  anterior  limb,  pass  above  its  anterior  extremity,  by  crossing  its 
direction. 

Action. — It  pulls  the  whole  limb  backwards,  in  pressing  on  the  angle  of 
the  shoulder. 

B.  STERNO-PRESCAruLARis. — (The  pectoralu  parvus  of  Percivall  and 
Bourgelat.) — Form — Situation — Direction. — A  long  prismatic   muscle,  con- 


MUSCLES  OF  THE  TRUNK.  235 

tracted  at  its  two  extremities,  situated  in  front  of  the  preceding,  arising 
from  the  sternum,  directed  forwards  and  outwards  towards  the  scapulo- 
humeral angle,  and  afterwards  reflected  ujjwards  and  backwards  on  the 
anterior  border  of  the  shoulder,  which  it  follows  to  near  the  cervical  angle 
of  the  scapula. 

Structure  and  Attachments. — It  is  formed  of  very  large  fleshy  fasciculi, 
aaalogous  to  those  of  the  sterno-trochineus,  which  originate,-  by  their 
inferior  extremities,  from  the  sides  of  the  sternal  keel  and  the  cartilages  of 
the  first  three  or  four  ribs.  They  follow  the  direction  of  the  muscle,  and 
terminate,  one  above  the  other,  on  a  short  aponeurosis  which  covers  the 
supraspinatus,  and  is  confounded  with  the  external  aponeiu-osis  of  the 
scapula  (Fig.  114,  14). 

Belations. — In  its  axillary  portion,  this  muscle  responds,  inwardly,  to 
the  costo-sternalis,  the  fii-st  sternal  cartilages,  and  the  corresponding  inter- 
costal muscles :  outwards,  to  the  sterno-trochineus  and  sterno-aponeuroticus. 
In  its  prescapular  portion,  it  is  in  relation,  out\^ardly,  vnth.  the  mastoido- 
humeralis  and  trapezius ;  inwardly,  with  the  subscapulo-hyoideus,  the 
scalenus,  and  the  angulai-is  of  the  scapula ;  beliind,  with  the  suprasjjinatus 
which  is  separated  from  it  by  the  external  scapular  aponeurosis. 

Action. — This  muscle  is  a  congener  of  the  sterno-trochineus,  and  pulls 
the  scapula  backwai'ds  and  downwards.  It  is  also  a  tensor  of  the  scapular 
aponem-osis. 

DIFFEREXTIAL    CHAKACTEKS   OF   THE   MCSCLES   OF   THE   AXILLAKT   KEGION   IX   OTHEB 
THAN   SOLIPED   ANIJIALS. 

"With  regard  to  the  superficial  pectoral,  it  is  remarked  that  in  the  Ox,  Sheep,  and 
Pig,  the  sterno-humeralis  is  small  aud  less  distinct  from  the  sterno  apuneuroticus  than  in 
Solipeds ;  and  that  in  the  Dog  and  Cat,  the  stemc-aponeviroticus  is  very  thin  and 
narrow. 

In  the  deep  pectoral  there  is  found,  in  the  Ox,  a  sterno-prescapuJaris  scarcely  distinct 
from  tlie  sterno-trochineus,  and  which  does  not  extend  beyond  the  inferior  extremity  of 
tlie  supraspinatus.  In  the  bheep,  this  muscle  is  quite  confounded  with  the  sterno- 
trochineus.  In  the  Fig,  the  sterno-prescapularis  somewhat  resembles  that  of  the  Horse. 
Its  inferior  extremity  only  covers  the  first  chondro-sternal  articulation ;  the  superior 
extremity  is  more  voluminous.  With  regard  to  the  sterno-trochineus.  it  terminates  on 
the  summit  of  tlie  great  trochanter,  after  detaching  a  short  branch  t  >  the  tendon  of  the 
coraco-ljumeralis.  The  stemo-prescapulaiis  of  the  Dog  is  very  feeble,  and  terminates 
with  the  principal  muscle  on  the  humerus. 

COSTAL    EEGIOK. 

In  each  costal  region  we  find  fifty-four  muscles,  which  concur,  more  or 
less  directly,  in  the  resjiiratory  movements.  These  muscles  are :  1,  The 
great  serratus  ;  2,  The  costo-transversalis  ;  3,  Seventeen  external  intercostah ; 
4,  Seventeen  internal  intercostah;  5,  Seventeen  supercosfals ;  6,  The 
triangularis  sterni. 

Preparation. — 1.  Place  the  subject  in  the  second  position.  2.  Eeraove  the  fore- 
limb  and  all  the  muscles  attaching  it  to  the  trunk,  by  sawing  through  the  scapula  as 
shown  in  figure  10.?,  in  order  to  expose  the  great  serratus  and  costo-traii&versalis  muschs  ; 
finish  the  dissection  of  the  former  by  taking  away  aU  the  yellow  fibrous  tissue  which 
covers  its  posterior  dentations.  3.  Study  the  external  intercostals  and  the  supercostals, 
after  removing  the  great  oblique  muscle  of  the  abdomen,  the  serrati  mnscles,  the 
common  intercostal  (ilio-costalis),  and  the  ilio-spinalis.  4.  Excise  some  external  inter- 
costals in  order  to  show  the  corresponding  internal  ones.  5.  The  triangularis  is  dis- 
sected oil  another  portion,  which  is  obtained  in  separatiug  the  sternum  from  the  thorax 
by  sawing  through  tlie  sternal  ribs  a  little  above  their  inferior  extremity. 


23G  THE  MUSCLES. 

1.  Great  Serratus.     (Fig.  105,  15.) 

Synonyms. — Costo-subscapularis— G/rarrZ.  Posterior  portion  of  the  serratus  magnus  of 
Bourgelat.    (A  portion  of  Percivall's  serratus  magnus.) 

Form — Situation. — A  veiy  wide  muscle,  disposed  like  a  fon,  split  up 
into  digitations  at  its  inferior  border,  applied  against  the  thoracic  walls,  and 
partly  concealed  by  the  shoulder. 

Structure. — It  is  composed  of  divergent  fleshy  fibres,  all  of  which  con- 
verge towards  the  superior  extremity  of  the  scapula,  and  are  covered  by 
a  very  strong  aponeurosis  that  gradually  diminishes  from  above  to  below, 
and  only  adheres  to  the  muscle  in  its  inferior  part. 

Attachments. — 1,  To  the  external  face  of  the  eight  sternal  ribs ;  2,  To 
the  anterior  triangular  surface  of  the  internal  face  of  the  scapula,  behind  the 
angularis,  with  which  it  is  confounded;  3,  To  the  whole  extent  of  the 
posterior  triangular  surface  of  that  bone. 

On  reaching  the  scapula,  the  aponeurosis  separates  from  the  fleshy 
fibres,  and  is  inserted  alone  into  the  fibrous  plane  which  covers  the  muscular 
fasciculi  of  the  subscapularis. 

Relations. — The  great  serratus  responds :  outwardly,  and  through  the 
medium  of  an  abundant  supply  of  cellular  tissue,  which  facilitates  the  play 
of  the  limb  against  the  lateral  wall  of  the  thorax,  to  the  subscapularis, 
supraspinatus,  the  adductor  of  the  arm,  great  dorsal  (latissimus  dorsi),  and 
the  mass  of  olecranian  muscles ;  inwardly,  to  the  first  seven  external  inter- 
costals,  to  the  sides  of  the  sternum,  and  the  anterior  small  serratus.  Its  four 
posterior  digitations  cross  the  first  five  of  the  great  oblique  muscle  of  the 
abdomen,  and  are  covered  by  a  prolongation  of  the  abdominal  tunic. 

Action. — With  that  of  the  opposite  side,  this  muscle  constitutes  a  vast 
brace  or  girth  on  wliich  the  thorax  rests  when  the  animal  is  supported  on 
its  limbs;  it  therefore  acts,  in  relation  to  the  trunk,  like  a  suspensory 
ligament.  When  it  contracts,  its  fixed  point  being  the  thoracic  walls,  it 
pulls  the  superior  extremity  of  the  scapula  do\vnward  and  backward,  and 
causes  this  portion  of  the  limb  to  perform  a  swinging  movement  which 
carries  the  inferior  angle  upwards  and  forwards.  If  the  limb  is  the  fixed 
point,  then  it  raises  the  thorax  between  the  two  anterior  members,  and 
assists  in  the  respiratory  movements  by  elevating  the  ribs. 


2.  Transverse  Muscle  of  the  Bibs.     (Fig.  105,  16.) 
Synonyms. — Costo-stcrnalis — Girarcl.    {Lateralis  sterni — Percivall.') 

Form  —  Structure  —  Direction  —  Situation. —  This  is  a  flattened  band, 
aponeurotic  at  its  extremities,  oblique  from  upwards  and  forwards,  and 
situated  under  the  preceding  muscle,  at  the  inner  aspect  of  the  deep  pectoral. 

Attachments. — Its  posterior  extremity  is  fixed  to  the  sternum  and  the 
fouith  sternal  cartilage ;  the  anterior  to  the  external  face  of  the  first  rib. 

Relations. — Inwardly,  with  the  second  and  third  ribs,  into  which  are 
often  inserted  some  of  its  fasciculi,  and  with  the  three  first  intercostal 
muscles.     Outwardly,  with  the  two  portions  of  the  deep  pectoral  muscle. 

Action. — This  is  an  auxiliary  to  the  expiratory  muscles.  (Leyh  says  its 
action  is  to  raise  the  ribs  and  their  cartilages,  and  thus  to  enlarge  the 
anterior  portion  of  the  thorax  during  inspiration.) 


TEE  MUSCLES.  237 

3.  External  Intercosfals.     (Fig.  104,  68.) 

Situation — Form. — These  muscles  fill  tlie  spaces  between  the  ribs,  but 
do  not  descend  beyond  their  inferior  extremities ;  they,  therefore,  do  not 
occupy  the  intervals  between  the  cartilages.  They  are  flattened,  fleshy 
bands,  gradually  diminishing  in  thickness  from  above  to  below. 

Structure — Attachments. — Each  intercostal  muscle  is  composed  of  a 
series  of  muscular  fasciculi,  intermixed  with  numerous  aponeurotic  fibres, 
both  of  which  jiass  obliquely  backwards  aud  downwards,  from  the  posterior 
border  of  the  preceding  to  the  external  face  of  the  succeeding  rib. 

Belations. — They  respoud,  outwardly,  to  the  different  muscles  applied 
against  the  thoracic  walls ;  inwardly,  to  the  internal  intercostals. 

4.  Internal  Intercostals.  (Fig.  106, 16.) 

These  are  placed  at  the  internal  face  of  the  preceding,  which  they  exactly 
repeat  with  regai-d  to  their  general  form,  but  from  which  they  difier  in  the 
following  jDoints : 

1.  Very  thick  between  the  costal  cartilages,  these  muscles  are  reduced 
at  the  upper  part  of  the  intercostal  spaces  to  a  thin  aponeurotic  layer, 
supported  only  by  some  fleshy  fibres.  They  therefore  gradually  diminish 
in  thickness  from  below  upwards. 

2.  Their  fasciculi  are  less  tendinous  than  those  of  the  external  inter- 
costals, and  are  carried  obliquely  forward  and  downward,  from  the  anterior 
border  of  the  posterior  rib  to  the  posterior  border  and  internal  face  of  the 
rib  in  front ;  so  that  the  fibres  of  the  external  and  internal  intercostals'-  cross 
each  other  like  the  letter  X. 

3.  Outwardly,  they  respond  to  the  external  intercostals ;  inwardly,  to 
the  costal  pleura. 

Action  of  the  intercostal  muscles. — The  function  of  these  muscles  has  been 
for  a  long  time,  and  is  even  now,  much  discussed ;  and  it  may  be  said  that 
there  were  never,  perhaps,  more  diverse  or  contrary  oiunions  given  on  any 
subject  than  on  this.  M.  Berard,  who  has  summed  up  the  elements  of  the 
discussion  with  the  greatest  judgment,  considers  the  external  intercostals  as 
inspiratory  muscles,  and  the  internal  ones  also  as  inspiratory  by  those 
fasciculi  which  occupy  the  siDaees  between  the  costal  cartilages ;  the 
remainder,  the  majority,  are  expiratory. 

5.  Supercostals. 
Synonyms. — Transverso-costales — Girard.     (Levatores  costarum — Percivall.) 

Small,  flat,  triangular,  muscular  and  tendinous  fasciculi,  constituting, 
it  might  be  said,  the  heads  of  the  external  intercostals,  from  which  they  are 
scarcely  distinguishable  in  the  first  and  last  costal  intervals. 

They  arise  from  the  transverse  processes  of  the  dorsal  vertebrfe,  and  are 
directed  backwards  and  outwards,  gradually  expanding,  to  terminate  on  the 
external  face  of  the  one  or  two  ribs  which  succeed  their  fixed  insertion. 
Outwardly,  they  respond  to  the  ilio-spinalis ;  inwardly,  to  the  external 
intercostals. 

The  supercostals  draw  the  ribs  forward,  and  are  consequently  inspiratory 
muscles. 

6.   Triangularis  of  the  Sternum. 

Stjnonyms. — Stemalis — BourgeJat.  Stemo-costalis — Girard.  'The  sterno-costales  of 
Percivall,  and  sterno-cosfalis  of  Leyh.) 


238  THE  MUSCLES. 

Form — Situation. — This  muscle,  flattened  above  and  below,  elongated 
from  before  to  behind,  and  dentated  at  its  external  or  superior  border,  is 
situated  in  the  thoracic  cavity,  above  the  sternum  and  the  cartilages  of  the 
true  ribs. 

Attachments. — It  is  fixed,  by  its  internal  border,  on  the  superior  face 
of  the  sternum,  to  the  ligamentous  cord  which  circumscribes  it  outwardly. 
It  has  its  movable  insertion  on  the  cartilages  of  the  sternal  ribs,  the  first 
excepted,  by  means  of  digitations  from  its  external  border. 

Structure. — It  is  formed  of  strongly  aponeurotic  muscular  fasciculi,  which 
are  directed  from  the  internal  to  the  external  border. 

Belations. — Inwardly,  with  the  pleura ;  outwardly,  with  the  cartilages  to 
which  it  is  attached,  the  internal  intercostals,  and  the  internal  thoracic  vein 
and  artery. 

Action. — The  triangularis  of  the  sternum  concui'S  in  expiration  by 
depressing  the  costal  cartilages.  (Leyh  asserts  that  if  the  fixed  point 
be  the  sternum,  this  muscle  pulls  the  I'ibs  forwards,  and  so  widens  the 
thoracic  cage  ;  but  if  the  fixed  point  is  the  ribs,  the  sternum  will  be  raised 
and  the  thoracic  space  diminished.) 

DIFFEEENTIAL   CHARACTERS   IN   THE   MUSCLES   OF   THE   COSTAL   REGION   IN   OTHER 
THAN   SOLIPED  ANIMALS. 

The  muscles  of  the  costal  region  cannot  "be  the  same  in  number  in  all  the  domes- 
ticated animals;  the  intercostals  and  supercostals,  for  instance,  must  vary  in  number 
with  that  of  the  ribs.  Beyond  this,  the  differences  are  slight.  In  the  Ox,  the  great 
serratus  is  very  extensive,  and  the  portion  which  passes  to  the  posterior  triangular 
surface  of  the  scapula  is  readily  distinguished  from  the  anterior  by  its  diminished 
thickness,  the  larger  proportion  of  aponeurotic  fibres  it  contains,  and  the  flattened 
tendon  by  means  of  which  it  is  inserted.  In  the  Pi'd,  it  is  remarked  that  the  internal 
intercostals  are  prolonged,  maintaining  a  certain  thickness,  to  near  the  vertebral  column, 

COMPARISON   OF   THE   THORACIC   MUSCLES   OF   MAN   WITH   THOSE   OF   THE   DOMESTICATED 

ANIMALS. 

The  muscles  of  the  axillary  region,  the  costal  region,  and  the  diaphragm  are  desig- 
nated in  ]\Ian  as  the  thoracic  muscles. 

The  pectoral  muscles  are  distinguished  into  great  and  small.  The  great  pectoral 
corresponds  to  the  superficial  pectoral  of  the  Horse.  It  is  attached,  on  one  side,  to  the 
inner  two-thirds  of  the  clavicle,  the  anterior  face  of  the  sternum,  and  the  cartilages  of 
the  first  six  ribs;  on  tlie  other,  to  the  anterior  border  of  the  bicipital  groove  and,  by  a 
fibrous  expansion,  to  the  aponeurosis  of  the  arm.  The  costal  fasciculi  are  distinctly 
separated  from  the  clavicular  and  sternal  fasciculi. 

The  small  pectoral,  which  corresponds  to  the  deep  pectoral  of  animals,  is  inserted,  on 
the  one  part,  into  the  external  face  of  the  third,  fourth,  and  fifth  ribs  ;  on  the  other  part 
by  a  tendon  to  the  anterior  Ixirdcr  of  the  coracoid  process. 

In  Man,  tliere  is  found  a  muscle  which  does  not  exi.st  in  animals;  this  is  the  sub- 
clavhis,  a  very  .slender  fasciculus  situated  beneath  the  clavicle,  and  attached  to  the 
cartilage  of  the  first  rib  and  the  external  portion  of  the  lower  face  of  the  clavicle  (see 
Fig.  117,  5). 

The  great  serratus  does  not  show  any  distinct  aponeurosis  on  its  surface ;  it  arises 
from  the  eight  first  ribs,  and  its  digitations  are  grouped  into  three  principal  fasciculi. 

Lastly,  in  Man  Ihe  internal  intercostals  are  prolonged  to  the  vertebral  column  by 
small  muscles,  named  the  suhcostals  (or  intracostals). 

INFERIOR   ABDOMINAL    REGION. 

The  lateral  and  inferior  walls  of  the  abdominal  cavity  are  formed  by  a 
wide  musculo-aponeurotic  envelope,  which  rests,  by  its  periphery,  on  the 
sternum,  ribs,  lumbar  vertebra,  ilium,  lumbo-iliac  aponeurosis,  and  the 
pubis.  This  envelope  is  concave  on  its  superior  surface,  and  results  from 
the  assemblage  of  four  pairs  of  large  membranous  muscles  arranged   in 


MUSCLES  OF  TEE  TEVNK.  239 

superposed  layers.  Eeckoning  tlaera  from  without  inwards,  these  are 
designated  the  great,  or  external  oblique,  the  small,  or  infernal  oblique,  the 
great  straight,  and  the  transverse  muscle.  Covered  outwardly  by  an  expan- 
sion of  yellow  fibrous  tissue,  the  tunica  abdominalis,  and  separated  from 
those  of  the  opposite  side  by  the  ichite  line  (linea  alba),  a  medium  raphe  ex- 
tending from  the  sternum  to  the  pubis,  these  muscles  support  the  intestinal 
mass,  and  by  their  relaxation  or  contraction  adapt  themselves  to  the  varia- 
tions in  volume  these  viscera  may  experience. 

Preparation. — After  placing  the  animal  in  the  first  position,  a  wide  opening  is  to  be 
made  in  the  pectoral  cavity  by  the  ablation  of  a  certain  number  of  ribs,  which  should  be 
divided  inferiorly,  above  the  costal  attachments  of  the  great  oblique  muscle.  The  heart 
and  lungs  are  removed;  then  an  incision  is  made  in  tlie  diapliragm,  to  allow  the 
digestive  viscera  contained  in  the  abdominal  cavity  to  be  taken  away.  It  is  not  abso- 
lutely necessary,  however,  to  empty  that  cavity,  and  if  its  contents  be" allowed  to  remain, 
several  punctures  should  be  made  in  the  large  intestine  to  prevent  the  accumulation  of 
gas.  and  the  too  great  distention  of  the  abdominal  parictes. 

These  preliminary  precautions  having  been  adopted,  then  proceed  in  the  following 
manner : 

1.  Eemove  the  skin  from  this  region,  and  with  it  the  panniculus  camosus,  in  order  to 
study  the  external  surf;\ce  of  the  abdominal  tunic.  2.  The  dissection  of  the  great 
oblique  muscle  is  accomplished  by  removing  the  yellow  fibrous  envelope  from  the  fleshy 
portion  of  the  muscle,  together  with  the  stemo-trochineus.  Tlie  inguinal  ring  should 
be  exposed  by  the  ablation  of  the  dartos  muscle,  the  sheath  and  penis,  or  the  mammae. 
3.  On  the  opposite  side,  tlie  small  oblique  is  uncovered  by  excising  the  great  oblique, 
leaving,  however,  that  portion  of  the  aponeurosis  which  is  mixed  up  with  that  of  the  first 
muscle.  4.  The  latter  having  been  studied,  dissect  the  great  straight  muscle  of  the 
abdomen  on  the  same  side,  in  separating  from  the  white  line,  by  a  longitiidinal  incision, 
the  aponeurosis  common  to  the  two  oblique  muscles,  dividiua:  this  aponeurosis  and  the 
fleshy  portion  of  the  internal  oblique  by  another  incision  extending  transversely  from  the 
umbilicus  to  the  middle  of  the  lumbar  region,  and  laying  back  one  of  the  musculo- 
aponeiu'otic  sections  on  the  thigh,  the  other  on  the  ribs.  5.  The  transverse  muscle  is 
dissected  on  the  same  side  as  the  external  oblique  has  been.  To  expose  it,  nothing  more 
is  necessary  than  to  make  two  incisions  similar  to  the  foregoing,  but  iucluding  the  two 
oblique  and  the  straight  muscle,  throwing  back  the  two  portions  as  above.  6.  Lastly, 
open  the  entire  abdominal  cavity  hx  cutting  through  the  transverse  muscle  in  the  same 
way ;  then  study  the  muscular  digitations  of  that  muscle,  the  internal  orifice  of  the 
inguinal  canal,  and  the  leaf  reflected  from  the  aponeurosis  of  the  great  oblique  muscle. 

1.  Abdominal  Tunic. 

The  vast  expansion  of  yellow  elastic  fibrous  tissue  spread  over  the  two 
external  oblique  muscles  of  the  abdomen  is  so  named. 

Very  thick  towards  the  prepubic  tendon  of  the  abdominal  muscles  and 
in  the  vicinity  of  the  linea  alba,  this  expansion  gradually  thins  as  it  ap- 
proaches the  sternum,  and  disappears  near  the  abdominal  insertion  of  tlie 
sterno-trochineus  muscles.  It  also  diminishes  in  thickness  as  it  extends 
from  the  linea  alba ;  and  when  it  reaches  the  fleshy  portion  of  the  great 
oblique  muscle  it  becomes  reduced  to  an  extremely  thin  leaf,  whose  fasciculi 
separate  more  and  more  from  one  another,  until  they  completely  disappear. 
Anteriorly,  however,  it  is  seen  to  be  prolonged  on  each  side  to  the  posterior 
digitations  of  the  serratus  magnus.  Posteriorly,  it  furnishes  some  bundles 
of  fibres,  which  are  detached  from  the  surface  of  the  common  tendon,  and  • 
are  carried  between  the  thighs  to  be  lost  on  the  internal  crural  muscles. 

The  abdominal  tunic  is  covered  by  the  skin  and  the  panniculus 
carnosus,  from  which  it  is  separated  by  an  abundance  of  cellular  tissue.  In 
the  male,  its  external  surface  gives  attachment  to  the  suspensory  ligaments 
of  the  sheath,  and  to  the  dartos  :  and  in  the  female,  to  the  elastic  capsule 
which  envelops  each  mammary  gland.  By  its  internal  face,  it  closely 
adheres  to  the  aponeurosis  of  the  great  oblique  muscle  ;  though  it  is  easily 


240  THE  MUSCLES. 

separated  from  the  fleshy  portion.  It  is  traversed  by  several  openings  which 
afford  passage  to  the  subcutaneous  vessels  and  nerves  of  the  abdominal 
region. 

The  abdominal  tunic  acts  as  an  immense  elastic  girth  or  bandage,  which 
aids  the  muscles  in  sustaining  the  weight  of  the  intestines.  As  the  digestive 
organs  increase  in  vohmie  this  tunic  increases  in  thickness. 

In  the  Pig,  Dog,  and  Cat,  it  is  reduced  to  a  simple  cellulo-aponeurotic  lamina,  owing 
to  the  stomacli  and  intestines  in  these  animals  exercising  but  a  small  amount  of  pressure 
on  the  abdominal  parietes. 

2.   WJiite  Line. 

The  white  line  (linea  alba)  is  a  fibrous  cord  comprised  between  the 
internal  border  of  the  two  great  straight  muscles,  and  is  considered  as  being 
formed  by  the  intercrossing,  on  the  median-line,  of  the  aponeuroses  belonging 
to  the  oblique  and  transverse  muscles.  Attached,  in  fi'ont,  to  the  inferior 
surface  of  the  xiphoid  appendage,  this  cord  is  confounded,  behind,  with  a 
large  tendon,  the  prepubic  or  common  tendon  of  the  abdominal  muscles,  which 
is  fixed  to  the  anterior  border  of  the  pvibes  (Figs.  90,  A;  108,  c;  116,  i). 
This  tendon,  covered  by  the  abdominal  tunic,  contributes  to  form  the 
internal  commissure  of  the  inguinal  ring,  and  gives  origin  to  the  pubio-femoral 
ligament. 

Towards  the  union  of  its  posterior  third  with  its  two  anterior  thirds, 
the  white  line  wideus,  so  as  to  form  a  lozenge-shaped  space,  in  the  centre 
of  which  is  found  the  remains  of  the  umbilicus  and  the  umbilical  cord 
(Fig.  116,  14). 

3.  Great  Oblique,  or  External  Oblique  of  the  Abdomen.    (Figs.  105, 18  ;  116,  5.) 
Synonyms. — Costo-abdominalis — Girard.     {Ohliquus  externus  ahdomims — PercivaU.) 

Situation — Composition. — This  muscle,  the  largest  and  the  most  super- 
ficial of  the  four,  is  composed  of  a  flesliy  and  an  aponeurotic  portion. 

Form,  Structure  and  Attachments  of  tlie  fleshy  portion. — This  is  composed 
of  fibres  directed  obliquely  downwards  and  backwards,  and  presents  itself  as 
a  wide  muscular  band,  narrower  before  than  behind,  applied  to  the  inferior 
surface  of  the  last  thirteen  or  fourteen  ribs.  Its  superior  border  is  concave, 
and  attached :  1,  To  the  external  surface  of  the  ribs  just  mentioned  by  as 
many  slightly  aponeurotic  digitations,  the  first  four  of  which  cross  the  denta- 
tions of  the  great  serratus ;  2,  To  the  aponeurosis  of  the  great  dorsal  muscle, 
from  the  last  rib  to  the  external  angle  of  the  ilium  (Fig.  105,  18).  Its  inferior 
border,  convex  and  sinuous,  is  continuous  witli  the  aponeurosis  ;  it  descends, 
in  front,  to  the  cartilaginous  circle  of  the  false  ribs,  which  it  projects  beyond 
posteriorly,  increasing  in  this  as  it  nears  the  lumbar  region. 

Form,  Structure,  and  Attachments  of  the  aponeurosis. — This  is  narrow  and 
thin  in  front,  wide  and  thick  behind,  of  a  triangular  form,  and  composed 
of  white,  nacrous-looking  fibres  passing  in  the  same  dii'cction  as  the  fibres 
of  the  fleshy  portion,  with  whose  inferior  border  it  is  continuous  by  its 
external  border.  Its  internal  border  is  inserted  into  the  white  line  and  the 
preijubic  tendon ;  and  its  posterior  border,  extending  from  the  external 
angle  of  the  ilium  to  the  anterior  border  of  the  pubis,  responds  to  the 
jjlicature  of  the  flank,  embraces  the  corresptmding  crural  muscles,  and 
establishes  the  line  of  demarcation  between  the  trunk  and  the  abdominal 
limb  (Fig.  116,  10). 

The  ajjoneurosis  of  the  great  oblique  gives  rise,  at  its  posterior  bordcsr, 
to  two  very  remarkable  fibrous  leaves  which  appear  to  be  produced  by  tlie 


MUSCLES  OF  THE  TRUNK.  241 

doubling  of  this  aponeurosis  into  two  layers.  One  of  these  leaves  descends  on 
the  internal  muscles  of  the  thigh  to  constitute  the  crural  aponeurosis 
(Fig.  116,  11);  while  the  other  is  reflected  ui)wards  and  forwards,  to  enter 
the  abdominal  cavity  ;  this  reflected  leaf  of  the  great  oblique  aponeurosis  is 
named  the  crural  arch  (lijament  of  Poupart  or  Fallopius).    (Fig.  108,  b.) 

Near  the  prepubic  tendon  of  the  abdominal  musclesj  and  immediately 
before  its  division  into  two  leaves,  the  aponeurosis  of  tbe  external  oblique  is 
pierced  by  a  large  oval  apertm-e  (Fig.  116,  5),  the  inferior  orifice  of  the 
canal  through  which  passes  the  cord  of  the  testicle  in  the  male,  and  the 
mammary  vessels  in  the  female.  This  channel  has  been  named  the  inguinal 
canal. 

The  description  of  the  femoral  aponeurosis,  the  crural  arch,  and  tbe 
inguinal  ring — a  necessary  complement  of  the  great  oblique  muscle — will  be 
given  hereafter. 

Itelations  of  tJie  Great  Oblique  Muscle. — By  its  superficial  face,  the 
external  oblique  responds  to  tbe  sterno-trochineus  and  tbe  abdominal  tunic, 
which  latter  separates  it  from  the  skin  and  tbe  panniculus.  By  its  deep  face, 
it  is  related  to  the  ribs,  into  which  it  is  insertCLl,  as  well  as  with  their  carti- 
lages, tbe  corresponding  intercostal  muscles,  the  small  oblique,  and  the  great 
straight  muscle.  The  latter  even  appears  to  be  attached,  through  the 
anterior  moiety  of  its  external  border,  to  the  fleshy  portion  of  the  great 
oblique,  by  means  of  a  slight  lamina  of  yellow  elastic  tissue,  which  covers, 
to  a  small  extent,  the  deep  face  of  the  two  muscles. 

Action. — The  external  oblique,  in  contracting,  compresses  the  abdominal 
viscera,  flexes  the  vertebral  column,  and  acts  as  an  exj^iratory  muscle.  (By 
its  compression  on  the  abdominal  viscera  it  concm-s  in  the  acts  of  defecation, 
mictui'ation,  and  parturition.) 

IxTERNAii  Crural  Aponeurosis. — This  fibrous  lamina  descends  from  the 
plicature  of  tbe  flank  on  the  patella  and  the  inner  surface  of  the  leg. 
Outwardly,  it  is  confounded  with  the  aj)oneurosis  of  the  fascia  lata;  in- 
wardly, it  degenerates  into  cellular  tissue.  It  covers  tbe  long  adductor  of 
the  leg,  part  of  the  short  adductor,  the  vastus  internus,  and  the  crural  vessels 
at  theii-  exit  from  the  abdominal  cavity. 

Crural  Arch. — As  already  mentioned,  this  is  the  reflected  leaf  of  the 
great  oblique  aponeurosis,  and  is  also  named  the  ligament  of  Fallopius  anA 
Poupari's  ligament.  It  is  a  ■nide,  flat  band,  attached  by  its  extremities  to  the 
external  angle  of  the  ilium  and  the  anterior  border  of  the  pubis.  Its 
anterior  face  (Fig.  108,  b)  forms,  inwardly,  tbe  posterior  wall  of  the  inguinal 
canal ;  it  gives  attachment,  outwardly,  to  the  posterior  fibres  of  the  small 
oblique  miiscle.  Its  posterior  face,  applied  against  the  superior  extremity  of 
the  patellar  muscles,  the  long  adductor  of  tbe  leg,  the  pectineus,  and  the 
crural  vessels  on  their  leaving  the  abdomfen,  embraces  all  these  parts  as  in  a 
vast  arch,  and  from  this  peculiarity  it  derives  its  name.  Its  superior  border 
is  inserted,  for  its  external  half,  into  the  lumbo-iliac  aponeurosis.  In  its 
middle  part  it  is  much  thinner,  and  is  prolonged  to  the  external  surface  of 
the  long  adductor  muscle  of  the  leg  and  tbe  iliac  fascia,  to  be  at  last  mixed 
up  with  the  latter.  Within  the  pectineal  insertion  of  the  small  psoas 
muscle,  it  forms  the  anterior  margin  of  the  crural  ring  :  a  triangular  orifice 
circumscribed  on  the  other  side  by  the  anterior  border  of  the  pubis,  the 
iliacus,  and  the  long  adductor  of  the  leg,  and  tbrough  which  pass  the  crural 
vessels  as  they  leave  the  abdomen  by  the  crural  arch.^     The  inferior  border 

*  This  orifice  is  covered  by  a  very  thin  aponeurotic  layer,  wliich  is  prolonged,  above, 
on  the  crural  vessels,  behind,  into  the  pelvic  cavity,  and  which  appears  to  be  continuous, 


242  TEE  MUSCLES. 

is  continuous  with  the  femoral  aponeurosis  and  that  of  the  great  ohlique 
muscle. 

Inguinal  Canal. — This  is  an  infundibuliform  canal  compressed  on  each 
side,  through  which  the  spermatic  cord  and  scrotal  artery  pass  from  the 
abdomen  in  the  male,  and  the  external  mammary  vessels  in  the  female. 

Situated  on  the  side  of  the  prepubic  region,  in  an  oblique  direction 
downwards,  backwards,  and  inwards,  and  measuring  from  two  to  two-and- 
a-half  inches  in  length,  this  canal  lies  between  the  crm-al  arch,  which  con- 
stitutes its  posterior  wall,  and  the  fleshy  portion  of  the  small  oblique 
muscle,  which  forms  the  anterior  wall. 

Its  inferior  (external )  or  cutaneous  orifice,  also  named  the  inguinal  ring, 
is  much  larger  than  the  suj)erior  (internal).  Pierced  in  the  aponeurosis  of 
the  great  oblique,  in  the  angle  formed  by  the  union  of  the  internal  border 
with  the  posterior  border  of  the  aponeurosis,  this  openiDg  is  of  an  oval  form, 
directed  obliquely  backwards  and  inwards,  which  permits  it  to  be  described 
as  having  two  lips  or  pillars,  and  two  extremities  or  commissures. 

The  pillars,  distinguished  into  anterior  and  posterior,  are  composed  of  the 
arciform  fibres  from  the  aponeurosis  of  the  great  oblique  muscle. 

The  commissures,  internal  and  external,  result  from  the  union  of  the  two 
pillars  at  their  extremities.  The  internal  is  limited  by  the  prepubic  tendon 
of  the  abdominal  muscles. 

The  superior  (internal)  or  peritoneal  orifice  of  the  inguinal  canal  is  situated 
in  front  of,  and  directly  opj)osite  to,  the  crural  ring.  It  is  a  simide  dilatable 
slit,  comprised,  like  the  canal  itself,  between  the  crural  arch  and  the  small 
oblique  muscle.  Not  well  defined  at  its  extremities,  this  ojieuing  includes 
the  neck  of  the  vaginal  sheath. 

4.  Small  or  Internal  Oblique  Muscle  of  tJie  Abdomen. 

(Figs.  106,  17';  116,  2.) 

Synonyms. — Ilio-abdominalis — Girard.     (OUiquus  internus  abdominis — Percivall.) 

Situation — Composition. — Situated  beneath  the  preceding,  which  exactly 
covers  it,  this  muscle  is,  like  it,  composed  of  a  fleshy  and  aponeurotic 
portion. 

Form,  Structure,  Position,  and  Attachments  of  the  muscular  portion. — The 
muscular  portion  is  very  thick,  triangular,  and  flabelliform,  and  occui^ies  the 
region  of  the  flank.  Its  superior  border  is  united,  by  a  thick,  yellow,  elastic 
production,  to  the  aponeurosis  of  the  great  dorsal  (latissimus  dorsi),  and  a 
peculiar  small  muscle,  named  hy  the  Germans  the  retractor  costce  (retractor  of 
the  last  rib),  which  we  consider  as  a  dependency  of  the  small  oblique  muscle. 
Its  posterior  border  is  slightly  raised  and  lies  against  the  crural  arch,  from 
which  it  separates,  inwardly,  to  form  the  inguinal  canal.  Its  anterior  and 
inferior  border  is  convex,  irregular,  and  thinner  than  the  other  portions  of 
the  muscle,  and  is  continuous  with  the  aponeurosis.  All  the  fibres  entering 
into  the  composition  of  this  muscular  portion  ai-e  spread  like  a  fan,  and 
leave  the  external  angle  of  the  ilium  and  the  external  fourth  of  the  crural 
arch  to  be  directed,  the  posterior  fibres  backwards  and  inwards,  the  middle 
fibres  downwards,  and  the  anterior  fibres  forwards  to  reach  the  antero- 
inferior border  of  the  muscle. 


inferiorly,  with  the  upper  hordcr  of  Poupnrt's  ligament.  Tliis  lamina  is  perhnps  only  a 
dependency  of  the  sub})eritnneal  aponenrosis;  and  if  so,  it  represents  the  only  vestige 
of  the  fascia  tram^versalis  it  has  been  p  ssible  to  discover  in  Solipeds. 


MUSCLES  OF  TEE  TRUNK. 


24:^ 


Fig.  IIG, 


Form,  Structure,  and  Attachments  of  the  aponeurosis. — The  aponeurosis  is 
irregularly  triangular,  and  formed  of  nacrous-looking  fibres,  which  are 
directed  like  the  muscular  fibres,  and  cross 
in  X  fashion  the  aponeurotic  fibres  of 
the  external  oblique.  It  succeeds  the  an- 
tero-inferior  border  of  the  muscular  por- 
tion, and  is  separated,  superiorly,  into 
several  digitations  which  reach  the  in- 
ternal face  of  the  last  asternal  cartilages. 
Throughout  the  whole  extent  of  its  in- 
ternal border  it  is  fixed  to  the  white  line. 

Melations. — This  muscle  is  covered 
by  the  external  oblique.  The  aponeuroses 
of  the  two  muscles,  which  are  merely 
superposed  outwardly,  are  blended  in- 
wardly in  so  intimate  a  manner  that  it 
might  be  thought  their  respective  fasci- 
culi were  woven  into  each  other.  The 
small  oblique  covers  the  great  straight 
and  the  transverse  muscles. 

Action. — This  muscle,  a  congener  of 
the  preceding,  compresses  the  abdominal 
viscera,  depresses  the  last  ribs,  and  causes 
the  flexion,  either  dii-ect  or  lateral,  of  the 
vertebral  column. 

The  retractor  muscle  of  the  last  rib. — 
This  small  muscle,  flattened  on  each  side, 
and  triangular  in  form,  originates  by 
aponeurotic  fibres  from  the  summits  of 
the  first  two  or  three  transverse  processes 
of  the  lumbar  region.  It  terminates  on 
the  posterior  border  of  the  last  rib. 
Covered  by  the  last  digitation  of  the  pos- 
terior serratus  and  by  the  great  oblique, 
it  covers  in  turn  the  transverse  muscle  of 
the  abdomen.  In  contracting,  it  draws 
the  last  rib  backwards,  and  fixes  it  in 
that  position,  in  order  to  permit  the  ex- 
piratory action  of  the  internal  intercostal 
muscles.  It  therefore  plays  the  same 
part,  in  regard  to  these  muscles,  that  the 
scalenus  does  to  the  external  intercostal 
muscles  (Fig.  106,  17). 


MUSCLES  OF   THE   INFERIOR   ABDOMINAL 
REGION. 

1,  Aponeurosis  of  the  great  oblique ;  2, 
Muscular  portion  of  the  small  oblique  ; 
3,  Rectus  abdominis ;  3',  Transverse 
muscle ;  4,  Flat  tendon  by  which  the 
four  abdominal  muscles  are  inserted 
into  the  pubis ;  5,  Inguinal  ring ;  6, 
Its  anterior  pillar ;  7,  Its  posterior 
pillar;  8,  Its  external  commissure;  9, 
Internal  commissure;  10,  Posterior 
border  of  the  great  oblique  aponeu- 
rosis, 11,  Internal  crural  aponeurosis; 
12,  Strip  of  the  great  oblique  aponeu- 
rosis turned  downwards  to  show  the 
origin  of  Poupart's  ligament ,  14, 
Traces  of  the  umbilicus. 


5.  Great  Rectus  Muscle  of  the  Ahdomen. 
(Figs.  105,20;  116,3.) 

Synonyms. — Sterno-piibialis —  Girard.     {Rec- 
tus abdoniiius — Perciiall.) 

Situation — Extent  —  Form — Structure. 
— This  is  a  wide  and  powerful  muscular  band,  extending  from  the  sternum 
to  the  pubis,  included  between  the  aponeurosis  of  the  internal  oblique  and 
that  of  the  transverse  muscle,  narrower  at  its  extremities  than  in  its  middle 
portion,  and   divided  by  numerous  transverse  and    zig-zag   fibrous   inter- 


244  TEE  MUSCLES. 

sections.  These  strongly  adhere  to  the  aponeurosis  of  the  small  oblique 
muscle,  are  nearer  to  each  other,  and  more  distinct,  in  front  than  behind, 
and  are  produced  by  small  tendons  which  are  placed  at  certain  distances  on 
the  track  of  the  muscular  fasciculi,  making  it  somewhat  of  a  polygastric 
muscle. 

Attachments. — In  front :  1,  To  the  prolonging  cartilages  of  the  last 
four  sternal,  and  the  first  asternal  ribs ;  2,  To  the  inferior  face  of  the 
sternum.  Outwardly,  by  the  anterior  moiety  of  its  external  border,  to  the 
internal  face  of  the  great  oblique. 

Behind,  to  the  anterior  border  of  the  pubis  through  the  medium  of  the 
common  tendon,  which  is  a  direct  continuation  of  the  great  straight 
muscle. 

Belations. — By  its  inferior  face,  and  in  front,  with  the  sterno-trochineus 
and  great  oblique ;  for  the  remainder  of  its  extent,  with  the  aponeurosis  of 
the  small  oblique.  By  its  superior  face,  with  the  transverse  muscle  and 
the  cartilages  of  several  ribs.  By  its  internal  border,  with  the  white  line, 
which  separates  it  from  the  opposite  muscle. 

Action. — It  draws  the  thorax  backwards,  and  compresses  the  abdominal 
viscera.  It  is  also  the  principal  flexor  of  the  spine.  (Leyh,  remarking  that 
it  shares  in  the  functions  of  the  preceding  muscles,  adds  that  it  di-aws  the 
pelvis  forwards  during  copulation.) 

6.  Transverse  Muscle  of  the  Abdomen.     (Figs.  106,  18;  116,  3'.) 

Synonyms.  —  Lumbo-abdominalis  —  Girard.  ( Transversalis  abdominis  —  Percivall. 
The  costo-abdominalis  internus  of  Leyh.) 

Situation — Composition. —  This  muscle  is  situated  immediately  without 
the  peritoneum,  and  forms  the  deep  layer  of  the  abdominal  parietes.  It  is 
muscular  outwardly,  and  aponeurotic  for  the  remainder  of  its  extent. 

Form,  Structure,  and  Attachments  of  the  muscular  portion. — It  presents  a 
band  elongated  from  before  to  behind,  extending  from  the  sternum  to  the 
transverse  processes  of  the  last  lumbar  vertebrae,  following  in  its  course  the 
direction  of  the  cartilages  of  the  ribs,  and  formed  of  parallel  fibres  passing 
from  one  border  to  the  other. 

Its  superior  border,  concave,  is  attached  :  1,  To  the  internal  surface  of 
the  asternal  ribs  by  digitations  placed  opposite  those  of  the  diaphi'agm,  but 
the  majority  of  which  do  not  mix  with  theui ;  2,  To  the  extremity  of  the 
transverse  processes  of  the  lumbar  region  by  a  thin  fibrous  lamina.  Its 
inferior  border  is  convex  and  continuous  with  the  aponeurosis. 

Form,  Structure,  and  Attachments  of  the  aponeurosis. — This  is  triangular- 
shaped,  with  the  base  behind,  and  with  its  fibres  running  in  a  transverse 
direction  to  the  median  line.  Closely  laid  one  against  another  in  front, 
these  fibres  separate  behind,  and  form  only  a  very  thin  and  incomplete 
lamina. 

By  its  external  border,  the  aponeurosis  is  joined  to  the  inferior  margin 
of  the  muscular  portion.  Its  internal  border  is  fixed  to  the  xiphoid  cartilage 
and  the  white  line.  Its  posterior  border,  badly  defined,  appears  to  join  the 
crural  arch  only  on  its  outer  aspect. 

Belations. — Outwards,  with  the  inferior  extremity  of  the  asternal  ribs 
and  their  cartilages,  with  the  rectus  abdominalis,  the  small  oblique,  and  the 
depressor  muscle  of  the  last  rib  ;  inwardly,  with  the  peritoneum,  from  which 
it  is  separated  by  the  subperitoneal  aponeurosis  :  an  extremely  fibrous  layer 
which,  in  Man  and  some  animals,  becomes  much  thickened  towards  the  criu'al 


MUSCLES  OF  THE  TRUSK. 


245 


arch,  where  it  forms  adhesions.     It  has  been  described,  in  human  anatomy, 
as  the  fascia  transversal  Is. 

Action. — It   compresses  the  abdominal  viscera  when  it  contracts,  and 
presses  them  against  the  vertebral  column. 

Fig.  117. 

DIFFEREXTIAL      CHARACTEKS  =" 

OF  THE  ^a•SCLES  OF  THE 
ABDOMINAL  REGION  IN 
OTHER  THAN  SOLIPED 
ANIMALS. 

As  has  been  already 
said,  the  development  of  the 
abdomi)ial  tunic  is  in  pro- 
portion to  the  volume  of 
the  digestive  viscera.  This 
membrane  is,  therefore, 
very  wide  and  thick  in 
Buminants,  while  it  is  re- 
duced to  an  insignificant 
leaf  in  the  Pig  and  Car- 
nivora.  In  these  animals 
the  internal  crural  aponeu- 
rosis does  not  exist,  and 
is  replaced  by  a  cellular 
layer.  The  aponeurosis  of 
the  great  oblique,  instead  of 
being  doubled  into  two 
lamiuffi  at  its  posterior 
border,  is  entirely  reflected 
to  form  the  crural  arch. 
In  the  latter  animals,  the 
great  oblique  is  also  dis- 
tinguished by  the  extensive 
development  of  its  mus- 
cular part,  and  the  narrow- 
ness of  its  aponeurosis. 

The  muscular  portion 
of  the  small  oblique  of  Eu- 
minants  occupies  the  entire 
space  comprised  between 
the  posterior  border  of  the 
last  rib,  the  extremity  of  mtscles  of  the  anterior  aspect  of  the  body  of  man; 
the  transverse  processes  of  on  the  left  side  the  superficial  layer  is  seen,  on 
the  lumbar  vertebrae,  and       the  right  the  deeper  layer. 

the  external  angle  of  the  l,  Pectoralis  major;  2,  Deltoid;  3,  Anterior  boraer  of  the 
ilium.  The  small  retractor  latissimus  dorsi ;  4,  Serratus  magnus ;  5,  Subclavius,  right 
side ;  6,  Pectoralis  minor ;  7,  Coraco-brachialis ;  8,  Biceps, 
with  its  two  heads;  9,  Coracoid  process  of  the  scapula;  10, 
Serratus  magnus,  right  side  ;  11,  External  intercostal  muscle 
of  the  fifth  mtercostal  space ;  12,  External  oblique ;  13,  Its 
aponeurosis  with  the  linea  alba ;  14,  Poupart's  ligament ; 
15,  External  abdominal  ring;  16,  Rectus  muscle  of  right 
side;  17,  Pyramidalis  muscle;  18,  Internal  obhque ;  19, 
Conjoined  tendon  of  internal  oblique  muscle  and  Poupart's 
lisament. 


of  the  last  rib  is  not  distinct 
from  the  principal  muscle. 
This  arrangement  is  like- 
wise present  in  the  smaller 
domesticated  animals.  It 
is  also  to  be  remarked  that, 
iuRurninants,  the  tendinous 
intersections  of  the  great 
rectus  muscle  of  the  abdomen 
are  more  marked  at  its 
superior  than  its  inferior  face  :  and  that  the  aponeurosis  of  the  transverse  is  much  thicker 
and  more  resisting  than  in  Solipeds. 

comparison  op  the  abdominal  snrscLES  OF  MAN  with  those  of  animals. 
With  the  exception  of  some  slight  differences,  the  abdominal  muscles  of  Man  present 
the  same  disposition  as  those  of  the  smaller  animals. 

The  abdominal  tunic  is  not  present,  but  is  replaced   by  a  cellular  layer  which 

19 


■246  THE  MUSCLES. 

separates  the  skiu  from  the  aponeurosis  of  the  great  oblique.  The  muscular  portion  of 
this  muscle  has  no  attachment  to  tlie  aponeurosis  of  the  great  dorsal. 

The  aponeurosis  of  the  small  oblique  is  divided  into  two  lamellse  at  the  external 
border  of  the  great  straight  muscle,  the  anterior  is  consolidated  with  the  great  oblique, 
and  passes  in  front  of  the  great  straight ;  the  posterior  is  united  to  the  transverse,  and 
passes  behind  that  muscle. 

The  aponeurosis  of  the  transverse  is  divided  into  two  leave?,  only  one  of  which  remains 
behind  the  great  straight  muscle;  this  is  named  the  semilunar  Aihl  of  Douglas. 

The  great  rectus  muscle  of  the  abdomen  offers  three  transverse  librous  intersections  in 
its  length  (linex  transversa;).  At  its  upper  extremity,  it  divides  into  three  branches : 
the  internal  is  attached  to  the  xiphoid  appenda^'e  and  the  cartilage  of  the  seventh  rib ; 
the  middle,  to  that  of  tiie  sixth  rib  ;  the  external,  to  the  cartilage  of  the  fifth  rilj. 

"To  the  great  rectus  is  annexed  a  small  triangular  muscle,  the pyramplal,  which  is 
not  found  in  animals.  This  muscle  is  about  2J  inches  long  ;  is  sometimes  absent ;  most 
developed  in  children ;  is  attached  by  its  base  to  the  pubis,  between  the  spine  and  tho 
symphysis ;  and  by  its  summit  is  continuous  with  a  tendon  which  is  lost  in  the  white 
line,  and  constitutes,  with  that  of  the  opposite  side,  a  fibrous  cord  which  may  be  followed 
to  tiie  umbilicus." — Beaunis  and  Bouchard. 

Lastly,  at  the  inner  aspect  of  all  the  abdominal  muscles,  beneath  the  peritoneum,  is 
a  fibrous  lamella — the  fascia  transversalis.  'I'his  fascia  is  not  distinctly  limiteel  ujnvards 
or  outwards;  below,  it  is  fixed  to  the  crural  arch,  iu  the  viciuity  of  the  inguinal  canal, 
and  sends  a  layer  to  the  surface  of  the  oord  spermatic. 


DIAPHRAGMATIC    REGION. 

This  is  composed  of  a  single  muscle,  the  diaphragm. 

Diaphragm. 

Preparation. — Place  the  subject  in  the  first  position ;  open  the  abdomen  and  remove 
the  viscera  it  contains,  as  well  as  the  large  vascular  trunks  lying  upon  the  sublumbar 
region ;  detach  the  peritoneum  from  the  fleshy  portion  of  the  muscle,  in  order  to  show 
the  digit ations  of  the  latter  more  distinctly,  taking  care  not  to  allow  the  air  to  enter  the 
thoracic  cavity,  as  it  would  destroy  the  tense  and  concave  form  of  the  diaphragm. 

Situation — Direction. — Tlie  diaphragm  is  a  vast  musculo-aponeurotic 
partition  separating  the  thoracic  from  the  abdominal  cavity,  between  which 
it  is  placed  in  an  oblique  direction  downwards  and  forwards. 

Form. — It  is  flattened  before  and  behind,  elliptical,  wider  above  than 
below,  concave  posteriorly,  and  convex  anteriorly. 

Structure. — This  muscle  comprises:  1,  A  central  aponeurotic  portion 
designated  the  phrenic  centre,  which  is  incompletely  divided  into  two  folioles 
(leaflets)  by  the  pillars— Qeshy  columns  which  descend  from  the  sublumbar 
region;  2,  A  peripheral  (or  circumferential)  portion  forming  a  wide 
muscular  band  around  the  phrenic  centre. 

The  phrenic  centre  (also  named  the  speculum  Helmontii  or  mirroi*  of 
Helmont)  is  composed  of  white,  glistening,  radiating  fibres  which,  originating 
from  the  pillars,  extend  in  every  direction  to  join  the  muscular  fibres  of  the 
peripheral  portion.  It  is  pierced,  in  its  right  leaflet,  by  a  large  opening  for 
the  posterior  vena  cava. 

The  pillars  arc  two  in  number,  a  right  and  left.  The  right  pillar,  the 
most  considerable,  is  a  very  thick,  fleshy  fasciculus  which  commences  under 
the  loins  by  a  strong  tendon,  united  to  the  inferior  common  vertebral  liga- 
ment. It  descends  to  tho  phrenic  centre,  to  which  it  gives  a  heart-shaped 
appearance.  Near  its  inferior  extremity,  it  presents  an  opening  for  the  pas- 
sage of  the  oesophagus  into  the  abdominal  cavity. — The  left  pillar  is  a  small 
triangular  fasciculus,  partly  separated  from  the  preceding  by  an  orifice  for 
the  transmission  of  the  posterior  aorta  and  the  thoracic  duct.     It  also  arises 


MUSCLES  OF  THE  TRUNK. 


247 


from  the  subliimbar  region  by  a  tendon,  which  is  confounded  with  that  of  its 
congener. 

The  peripheral  muscular  portion  is  continuous,  by  its  concentric  border, 


Fiff.  118. 


DIAPHRAGM   OF   THE   HORSE;   POSTERIOR   FACE. 

1,  1',  The  two  portions  of  the  right  pillar ;  2,  Left  pillar  ;  3,  Tendons  of  the  pillars ; 

4,  4',  Peripheral  muscular  portion ;  5,  Left  leaflet  of  the  aponeurotic  portion ; 

5,  5',  Right  leaflet  of  the  same  ;  6,  Posterior  vena  cava ;  7,  (Esophagus  pasijng 
through  the  opening  in  the  right  pillar;  8,  Posterior  aorta  between  the  two 
pillars;  9.  Cartilaginous  circle  of  the  ribs;  10,  11,  Section  of  the  psoas  muscle; 
12,  Section  of  a  lumbar  vertebra  ;  13,  Section  of  the  common  mass  ;  14,  Retractor 
muscle  of  the  last  rib;  15,  Xiphoid  appendage  of  the  sternum. 

with  the  central  aponeurosis.  Its  excentric  border  is  divided  into  dentations. 
Above,  and  on  the  left  side,  it  nearly  always  joins  the  left  pillar  ;  but  ou 
the  right  side  it  stops  at  a  certain  distance  from  the  corresponding  pillar, 


248  THE  MUSCLES. 

so  that  towards  this  point  the  phrenic  centre  is  not  enveloped  by  the 
peripheral  portion,  and  is  in  contact  with  the  sublmnbar  region. 

Attachments. — 1,  To  the  bodies  of  the  lumbar  vertebrae  by  the  tendons 
of  its  two  pillars,  which  tendons  are  confounded  with  the  inferior  common 
vertebral  ligament ;  2,  By  the  external  contour  of  its  muscular  portion,  to 
the  superior  face  of  the  xiphoid  appendage  and  the  inner  face  of  the  last 
twelve  ribs,  near  their  inferior  extremities  or  cartilages.  The  digitations 
forming  the  last  insertions  do  not  intercross,  in  Solipeds,  with  those  of  the 
transverse  muscle  of  the  abdomen,  being  separated  by  an  interval  which  is 
wider  behind  than  before. 

Belations. — The  anterior  face  of  the  diaphragm  is  covered  by  the  pleura, 
and  responds,  mediately,  to  the  base  of  the  lung.  The  posterior  aspect, 
covered  by  the  peritoneum,  is  in  contact  with  the  greater  part  of  the  viscera 
contained  in  the  abdominal  cavity — the  stomach,  colon,  spleen,  and  liver  ;  the 
latter  is  even  attached  to  this  surface  for  a  portion  of  its  extent. 

On  each  side  of  the  pillars,  the  circumference  of  the  muscle  forms  an 
arch  which  passes  over  the  great  and  small  psoas  muscles. 

Action. — The  diaphragm,  in  contracting,  tends  to  become  an  inclined 
plane ;  its  central  portion  is  carried  backwards,  and  the  antero-posterior 
diameter  of  the  chest  is  increased.  It  is,  therefore,  essentially  an  inspiratory 
muscle.  It  may  also  raise  the  ribs  by  making  the  mass  of  abdominal  viscera 
its  fixed  point ;  it  then  acts  as  a  reflected  muscle,  to  which  these  viscera  serve 
as  a  pulley.  (The  diaphragm  also  aids  the  other  abdominal  muscles  in 
expulsive  efforts  and,  when  affected  with  irregular  spasmodic  contractions, 
produces  the  peculiar  phenomenon  in  Man  and  some  of  the  lower  animals, 
known  as  hiccough.) 

DIFFEREXTIAL  CHARACTERS  OP  THE  DIAPHRAGM  IN  OTHFR  THAN  SOLIPED   ANIMALS. 

In  the  Ox,  the  pillars  of  the  diaphragm  are  very  long  and  voluminous.  "The 
attachments  of  the  muscular  portion  are  much  farther  distant  from  the  cartilaginous 
circle  than  in  the  Horse,  particularly  at  the  superior  part;  this  disposition  explains  the 
innocuousness  of  puncture  of  the  paunch  in  the  middle  of  the  last  intercostal  space; 
for  with  the  Horse,  when  the  instrument  is  passed  through  this  part,  it  penetrates  the 
thorax. — Communicated  to  M.  Lecoq  by  M.  Tabourin. 

In  the  Sheep  we  have  not  remarked  that  the  costal  attachments  were  more  forward 
than  in  the  Horse. 

Kigot  erroneously  states  that,  in  the  Pig  and  Dori,  the  oesophagus  passes  between  the 
two  pillars  of  the  diaphragm  ;  on  several  occasions  we  have  convinced  ourselves  that  this 
conduit  traverses  the  right  pillar,  as  in  the  otber  animals. 

COMPARISON  OF   THE  DIAPHRAGM  OP  MAN  WITH  THAT  OF  ANIMALS. 

In  the  human  diaphragm,  the  aponeurotic  portion  is  divided  into  three  leaflets,  which 
has  caused  it  to  be  termed  the  aponeurotic  trefoil.  Between  the  middle  and  right 
leaflet  is  the  orifice  through  which  the  inferior  vena  cava  passes.  The  openings  for  the 
passage  of  the  cesopliagus  and  the  aorta  are  situated  between  the  two  pillars.  There  are 
frequently  met  with  in  Man  one  or  two  small  accessory  pillars,  separated  from  the  large 
pillars  by  an  aperture  that  affords  a  passage,  on  the  right  side,  to  the  vena  azygos  and  the 
sympathetic  nerve,  and  on  the  left  side,  to  one  of  the  lumbar  veins  and  the  other 
sympathetic  nerve. 

The  peripheric  muscular  portion  always  joins,  posteriorly,  the  central  muscular  portion. 

Article  II. — Muscles  op  the  Anterior  Limbs. 

These  are  divided  into  four  principal  groups :  the  muscles  of  the 
shoulder,  arm,  fore-arm,  and  foot. 


MUSCLES  OF  THE  ASTEBIOR  LIMBS.  249 

MUSCLES    OF    THE   SHOULDER. 

These  muscles  are  grouped  around  the  scapula,  and  all  act  upon  the  arm, 
which  they  extend,  flex,  abduct,  adduct,  etc.  They  form  two  regions :  an 
external  or  suprascapular,  and  an  internal  or  subscapular. 

A.  External  Scapular  Begion. 

This  comprises  four  muscles :  the  long  abductor  of  the  arm,  the  short 
abductor,  the  super-  for  supra-}  spinatus.  and  sub-  (or  infra-)  spinatus.  These 
muscles  are  applied  to  the  external  surface  of  the  scapula,  and  are  covered 
by  an  aponeurotic  lamella. 

Preparation  of  the  external  scapular  region.  — Separate  the  limb  from  the  tnmk; 
remove  the  trapezius  and  mastoido-humeralis,  to  expose  the  external  sm-face  of  the 
aponeurosis;  take  away,  also,  the  small  pectoral  muscle,  after  studying  its  mode  of 
insertion  into  this  fascia. 

This  bein?  accomplished,  next  remove  the  latter  muscle  to  show  the  supraspinatus, 
the  subspinatus,  and  long  abductor  muscle  of  the  arm ;  leaving  only  the  strip  which 
attaches  the  anterior  [.ortion  of  the  latter  to  the  tuberosity  of  the  scapular  spine. 

To  study  the  short  abductor  muscle,  it  is  only  necessary  to  cut  the  long  abductor  and 
superspinatus  across,  and  to  throw  back  the  sections :  an  operation  requiring  some  care, 
because  of  the  intimate  adherence  of  the  short  abductor  to  the  infraspinatus." 

1.  External  Scapular  Aponeurosis. 

This  aponeurosis,  to  which  the  sterno-prescapularis  and  long  adductor  of 
the  arm  act  as  tensors,  gives  origin,  by  its  internal  face,  to  several  septa 
which  peneti-ate  between  the  scapular  muscles,  and  form  around  them  more 
or  less  complete  contentive  sheaths.  Its  external  face  is  separated  from  the 
skin  by  the  panniculus  caruosus,  trapezius,  mastoido-hmneralis,  and  the 
aponeurotic  fascia  which  unites  the  last  two  muscles.  It  is  continuous,  in 
front,  with  the  thin  fibrous  expansion  extended  over  the  internal  scapular 
muscles  ;  behind  and  downwards,  it  is  prolonged  over  the  muscles  of  the  arm 
and  insensibly  degenerates  into  conjunctival  tissue ;  above,  it  is  attached 
to  the  fibro-cai-tilaginous  prolongation  of  the  scapula. 

2.  Long  Abductor  of  the  Arm,  or  Scapular  Portion  of  the  Deltoid. 
(Fig.  119,  1,  1.) 

Synonyms. — Seapulo-hmneralis  voagaas—Girard.  (Teres  major— Percivall.  Great 
scapulo-trochiterius — Leyh.) 

Situation — Composition — Form — Direction. — This  muscle  is  situated 
beneath  the  scapular  aponeurosis,  behind  the  subspinatus,  and  is  composed 
of  two  portions  placed  one  above  the  other,  separated  by  a  superficial  inter- 
space. The  posterior  portion,  the  most  considerable,  is  elongated  from 
above  to  below,  bulging  in  its  middle,  narrow  at  its  extremities,  plane  on  its 
external,  and  convex  on  its  internal  surface.  It  accompanies  the  posterior 
border  of  the  subspinatus,  and  is  lodged  in  a  depression  in  the  thick 
extensor  muscle  of  the  fore-arm. 

The  anterior  portion,  much  shorter  than  the  preceding,  extends  over  the 
subspinatus  and  short  abductor,  by  slightly  crossing  the  direction  of  these 
two  muscles.  Thick  inferiorly,  this  portion  diminishes  considerably  towards 
its  superior  extremity. 


250 


TEE  MUSCLES. 


Fis.  119. 


Structure  and  Attachments. — The  first 
portion  is  generally  paler  than  the  second, 
and  is  composed  of  longitudinal  fleshy  fibres 
deeply  fbtersected  by  tendinous  strips.  It 
takes  its  origin,  by  its  superior  extremity, 
from  the  dorsal  angle  of  the  scapula.  The 
anterior  portion  is  deeper-coloured  and  more 
tendinous  than  the  other.  Its  superior  ex- 
tremity, included  within  two  fibrous  folds 
resulting  from  the  duijlicature  of  the  scapular 
aponeurosis,  is  fixed,  through  the  medium  of 
these,  to  the  tuberosity  of  the  scapular  spine. 

These  two  muscular  bodies  unite  in- 
feriorly,  and  terminate  together  on  the  del- 
toid imprint  or  subtrochiterian  crest  by 
tendinous  and  muscular  fasciculi. 

Relations. — This  muscle  responds  :  out- 
wardly, to  the  scapular  a2)oneurosis,  with 
which  it  may  be  said  to  form  one  body; 
inwardly,  to  the  subspiuatus,  the  short  ab- 
ductor of  the  arm,  and  the  large  and  short 
extensors  of  the  fore-arm. 

Action. — It  gives  a  very  marked  abduc- 
tion movement  to  the  humerus,  and  also 
makes  it  pivot  outwards.  It  acts,  besides, 
as  a  flexor  of  that  bone,  when  its  action  is 
combined  with  that  of  the  adductor  of  the 
arm.  It  should  also  be  considered  as  a 
powerful  tensor  of  the  scapular  aponeurosis. 

3.  Short  Abductor  of  tlie  Arm,  or  Teres 
Minor.     (Fig.  85,  2,  3.) 

Synomjnis. — Scapiilo-humeralis  minor —  Girard. 
( Teres  minor  —  PercivaU.  Scapulo-trochiterius, 
medium  and  parvum — Leyh.) 

Volume — Situation — Direction. — A  small 
elongated  muscle,  situated  below  the  pre- 
ceding and  the  subspinatus,  along  the  pos- 
terior border  of  the  scapula,  whose  dii'ection 
it  follows. 

Form — Structure. — In  its  inferior  half  it 


1,  1,  Long  abductor  of  the  arm;  1',  Its  humeral 
insertion ;    2,  Superspinatus  ;  3,    Subspinatus  ; 
3',  Its  tendon  of  insertion ;  4,  Short  abductor 
EXTERNAL  MUSCLES  OF  THE  of  the  arm  ;  5,  Biceps  ;   6,  Anterior  brachialis ; 

RIGHT  ANTERIOR  LIMB.  7^  Large    extensor  of  the  fore-arm  ;  8,  Short 

extensor  of  the  fore-arm  ;  9,  Anconeus;  11,  Anterior  extensor  of  the  metacarpus  ;  11', 
Its  tendon;  12,  Aponeurosis  separating  that  muscle  from  the  anterior  brachialis ;  13, 
Oblique  extensor  of  the  metacarpus ;  14,  Anterior  extensor  of  the  phalanges ;  14',  Its 
principal  tendon;  15,  The  small  tendinous  branch  it  furnishes  to  the  lateral  extensor; 
16,  Lateral  extensor  of  the  phalanges;  16',  Its  tendon;  17,  The  fibrous  band  it 
receives  from  the  carpus;  18,  External  flexor  of  the  metacarpus ;  19,  Its  metacarpal 
tendon ;  20,  Its  supracaipal  tendon  ;  21,  Ulnar  portion  of  the  perforans ;  22,  Tendon 
of  the  perforans ;  23,  Its  carpa  lligament ;  24,  Its  reinforcing  phalangeal  sheath ; 
25,  Tendon  of  the  perforatus. 


MUSCLES  OF  THE  ANTEBIOR  LIMBS.  251 

is  prismatic,  muscular,  divided  by  fibrous  intersections,  and  easily  separated 
into  several  irregular  fasciculi.  In  its  superior  half  it  is  flattened,  entirely 
tendinous,  and  split  into  several  digitations,  the  longest  of  wkich  are  behind. 

Attachments. — It  originates  1,  Through  the  medium  of  its  tendinous 
digitations,  from  the  posterior  border  of  the  scapula  and  the  linear  imprints 
in  the  posterior  spinous  fossa ;  2,  From  the  smill  tubercle  situated  on  the 
external  side  of  the  margin  of  the  glenoid  cavity,  by  a  short  tendon.  It 
terminates  on  the  humerus,  between  the  crest  of  the  external  tubercle  and 
the  deltoid  imprint. 

Belations.- — Outwardly,  with  the  subspinatus  and  the  long  abductor ; 
inwardly,  with  the  large  extensor  of  tlic  fore-arm,  the  short  extensor,  and  the 
capsule  of  the  scapulo- humeral  articulation. 

Action. — Like  the  preceding,  this  muscle  is  an  abductor  and  outward 
rotator  of  the  humerus. 


4.  Superspinatus.     (Figs.  119,  2  ;  121,  5.) 

iSj/nonj/jMs.— Siipeiacrouiio-trochiterius— Girard.     (^Antea   spinatus — Percivall.      An- 
terior spmatus — Leyh.) 

Form — Situation. — This  muscle  is  thick  and  prismatic,  stronger  below 
than  above,  representing  a  very  elongated  pyramid,  and  completely  filling, 
and  even  projecting  beyond,  the  super- scapular  fossa. 

Structure — Attachments. — It  is  almost  entirely  formed  of  fleshy  fibres, 
which  are  attached,  by  their  superior  extremities,  to  the  cartilage  of  prolong- 
ment  of  the  scapula,  the  inner  face  of  the  scapular  aponeurosis,  the  super- 
scapular  fossa,  and  the  anterior  border  and  cervical  angle  of  the  scapula — 
fixed  insertion.  These  fibres,  on  reaching  the  inferior  extremity  of  the 
muscle,  form  two  very  thick,  short,  and  slightly  tendinous  branches,  united 
to  each  other  by  the  enveloping  coraco-radial  or  bicejis  aponeurosis.  The 
external  branch  reaches  the  summit  of  the  external  tubercle  :  the  internal  is 
inserted  into  the  corresponding  part  of  the  internal  tuberosity — movable 
insertion. 

Belations. — Outwards,  with  the  scapular  ajioneurosis,  to  which  its  fibres 
adhere  in  the  most  intimate  manner ,  inwards,  with  the  scapula  and  the  sub- 
scapularis  muscle  ;  forwards,  with  the  small  pectoral ;  and  behind,  with  the 
acromion  spine  and  the  subspinatus.  The  two  terminal  branches  cover  and 
embrace  the  coraco  radialis  tendon,  and  the  cai)sule  of  the  scapulo-humeral 
articulation. 

Action. — This  muscle  is  an  extensor  of  the  humerus,  and  a  tensor  of  the 
enveloping  coraco-radial  aponeurosis.  With  regard  to  the  articulation  of  the 
shoulder,  it  plays  the  part  of  a  powerful  ligament :  a  function  it  shares  with 
the  majority  of  the  other  scapular  muscles. 


5.  Subspinatus.     (Fig.  119,  3,  3'.) 

%non?/ni.s.— Sub-acromio-trochiterius — Girard.  {Postea  spinatus — Percivall.  Pos- 
terior spinatus — Leyh.) 

Situation — Form. — Situated,  as  its  name  indicates,  in  the  subspinatus 
fossa,  this  muscle  is  wide,  thin,  and  flattened  on  both  sides  at  its  superior 
extremity,  thick  and  prismatic  in  its  middle,  and  conoid  at  its  inferior 
extremity,  which  is  terminated  by  two  short  branches — an  external  and 
internal. 


252  TEE  MUSCLES. 

Structure. — The  muscular  fibres  entering  into  its  composition  are  directed, 
like  the  muscle  itself,  forward  and  downward  ;  they  are  deeply  mixed  with 
strong  aponeurotic  lamellae.  Of  the  two  branches  which  terminate  it 
inferiorly  the  external  is  the  strongest,  and  is  entirely  constituted  by  a 
powerful  tendon ;  the  internal  is  both  muscular  and  aponeurotic. 

Attachments.— All  the  fleshy  fasciculi  of  this  muscle  are  fixed,  either 
directly,  or  through  tlie  medium  of  the  internal  aponeurotic  lamellas :  1,  To 
the  whole  extent  of  the  subsjiinatus  fossa  ;  2,  To  the  acromion  spine  and  its 
tuberosity ;  8,  To  the  cartilage  of  prolongment  of  the  scapula ;  4,  To  the 
internal  face  of  the  scapular  aponeurosis— ^xec?  insertion.  The  movable 
insertion  of  the  muscle  takes  place,  on  the  external  tuberosity,  by  its  two 
terminal  branches,  the  internal  passing  within  the  convexity :  and  the  strong 
tendon  constituting  the  external  branch  (Fig.  119,  3'j  gliding,  by  moans  of 
a  synovial  bursa,  over  the  surface  of  this  convexity,  and  attaching  itself  to 
the  roughened  facet  which  forms  the  crest  of  the  external  tubercle. 

Relations. — This  muscle  is  covered  by  the  anterior  portion  of  the  long 
abductor  of  the  arm,  and  by  the  scapular  aponeurosis.  It  covers  the  scapula, 
its  cartilage,  the  fixed  insertion  of  the  large  extensor  of  the  fore-arm,  and  the 
short  abductor,  which  adheres  to  it  in  the  most  intimate  manner  at  its 
superior  or  aponeurotic  portion.  Its  anterior  border  responds  to  the 
acromion  spine  and  superspinatus ;  the  posterior  is  bordered  by  the  long 
abductor  of  the  arm.  Its  inferior  extremity  protects,  outwardly,  the  capsule 
of  the  scapulo-humeral  articulation,  and  is  concealed  beneath  the  mastoido- 
humei-alis. 

Action. — The  subspinatus  acts  on  the  humerus  as  an  abductor  and  out- 
ward rotator. 

B.  Internal  Scapular  Begion. 

This  is  composed  of  four  muscles :  three  principal,  the  suhsccqmlaris, 
adductor  of  the  arm  or  teres  major,  and  the  coraco-brachialis,  are  situated  at 
the  internal  face  of  the  scapula,  and  are  covered  by  a  very  small  fibrous 
fascia  which  is  formed  of  some  scattered  parallel  fibres  that  run  in  a  trans- 
verse direction.  The  last,  named  the  small  scapulo-humeralis,  is  a  very 
slender  fasciculus  deeply  lodged  behind  the  articulation  of  the  shoulder. 

Preparation.— Turn  over  the  limb  which  has  served  for  the  dissection  of  the  preceding 
region,  and  take  away  the  slight  internal  scapular  fascia.  Be  careful  to  preserve  the  ter- 
mination of  the  great  dorsal  muscle,  in  order  that  its  relations  nnd  ndhesions  with  the 
adductor  of  the  arm  may  be  studied ;  leave  also  th '  Immeral  insertion  of  the  sterno- 
trochineus,  so  that  its  union  with  the  tendon  of  the  coraco  humeralis  may  be  noted ;  in 
a  word,  prepare  the  region  as  it  is  represented  in  figure  121.  With  regard  to  the  small 
scapulo-humeral  muscle,  wliich  is  not  shown  in  this  preparation,  it  ought  to  be  dissected 
at  the  same  time  as  the  short  liexor  of  the  fore-arm. 


Suhsca-pularis.     (Fig.  121,  3). 
Synonym — Subscapulo-trochineus — Girard. 

Situation — Direction — Form. — This  muscle,  lodged  in  the  subscapular 
fossa  whose  name  it  bears,  affects  the  same  oblique  direction  as  the  scapula. 
It  is  wider  above  than  below,  and  divides  superiorly  into  three  portions ; 
so  that  its  form  exactly  repeats  that  of  the  excavated  surface  it  covers. 

Structure. — The  muscular  fibres  of  the  subscapularis  slightly  converge 
towards  its  inferior  extremity,  and  all  end  in  a  very  strong,  wide,  and  short 
tendon.     They  are  intermixed  with  deep  and  superficial  tendinous  fibres, 


MUSCLES  OF  THE  ANTERIOR  LIMBS.  253 

which  singularly  augment  the  tenacity  of  the  muscle  ;  the  superficial  fibres 
are  spread  over  the  internal  surface  in  glistening,  nacrous  layers. 

Attachments. — The  subscapularis  takes  its  origin  from  the  whole  extent 
of  the  fossa  whose  name  it  bears.  Its  movable  insertion  takes  place  on  the 
internal  tubercle,  by  means  of  a  voluminous  tendon  it  offers  at  its  inferior 
extremity.  A  particular  small  synovial  bursa  facilitates  the  gliding  of  this 
tendon  over  the  eminence  into  which  it  is  inserted. 

Eelations. — The  external  face  of  the  muscle  is  in  contact  with  the  scapula. 
Its  internal  face  is  applied  against  the  great  sen'atus,  from  which  it  is 
sepai-ated  by  a  thick  layer  of  cellular  tissue,  as  well  as  by  the  rudimentary 
fascia  covering  the  three  muscles  of  the  internal  scapular  region  in  common. 
Its  anterior  border,  margined  by  the  superspinatus,  adheres  closely  to  that 
muscle  in  its  upper  two-thirds,  and  forms  with  it,  by  its  inferior  third,  the 
intermuscular  space  that  lodges  the  subscapular  vessels  and  nerves.  Its 
posterior  border  responds  to  the  adductor  of  the  arm,  with  which  it  also 
unites  for  the  greater  part  of  its  extent ;  it  is  isolated  from  this  muscle,  in 
its  inferior  third,  by  the  interspace  lodging  the  subscapular  vessels  and 
nei-ves.  Its  terminal  tendon  covers  the  capsule  of  the  scapulo-humeral 
ai'ticulation,  which  it  powerfully  binds ;  it  is  in  part  covered  by  the  tendon 
of  origin  of  the  coraco-himieralis  muscle,  which  glides  over  its  surface  as  on 
a  pulley,  by  means  of  a  synovial  bursa. 

Action. — This  muscle  is  principally,  and  perhaps  exclusively,  an  adductor 
of  the  arm.  It  may  be  admitted,  however,  that  it  rotates  the  humerus 
inwards. 

Adductor  of  the  Ann,  or  Teres  Major.     (Fig.  121,  4.) 

Synonyms. — Subscapulo-bumeralis — Girard.  {Teres  major  —  FercivaU.  Great 
scapulo-humeralis — Leyh.) 

Form — Situation — Direction. — A  long  muscle,  flattened  on  both  sides, 
bulging  in  its  middle,  contracted  at  its  extremities,  thick  at  its  anterior,  and 
thin  at  its  posterior  border.  It  is  situated  behind  the  preceding,  in  the 
same  oblique  direction,  and  is  parallel  with  the  posterior  portion  of  the 
long  abductor,  which  it  appears  to  repeat  in  the  internal  scapular  region. 

Structure. — It  is  almost  entirely  muscular,  showing  only  some  tendinous 
fibres  at  its  external  surface  and  upper  extremity.  Its  inferior  extremity  is 
terminated  by  a  flat  tendon,  which  also  belongs  to  the  great  dorsal,  and 
which  has  been  already  described  (see  page  203). 

Attachments. — It  arises  from  the  dorsal  angle  of  the  scapula,  and  the 
posterior  border  of  the  subscapular  muscle — origin  ;  it  passes  to  the  circular 
imprint  on  the  body  of  the  humeras,  to  be  attached  by  its  inferior  tendon — 
termination. 

Eelations. — Outwards,  with  the  aponeurosis  of  the  great  dorsal  and  that 
of  the  long  extensor  of  the  fore-arm,  which  isolates  it  from  the  large 
extensor  muscle  ;  inwards,  with  the  great  serratus,  from  which  it  is  separated 
by  the  fibrous  and  cellular  layers  mentioned  in  the  description  of  the  sub- 
scapularis. Its  inferior  extremity  covers  the  short  flexor  and  middle  extensor 
of  the  fore-arm  ;  it  is  covered  by  the  long  branch  of  the  coraco-humeralis, 
and  by  the  vascular  and  nervous  trunks  which  send  their  ramifications  to 
the  arm,  fore-arm,  and  foot. 

Action. — This  muscle  adducts  the  arm,  and  causes  it  to  rotate  inwards. 
If  it  contracts  at  the  same  time  as  the  long  abductor,  it  directly  flexes  the 
humerus. 


25i  THE  MUSCLES. 

3.  Coraco-himeralis,  Coraco-hrachialis,  or  Omo-brachialis.     (Fig.  121,  10.) 
{Synonyms. — Coraco-humeralis — Percivall.     Middle  scajmlo-humeralis — Leyh., 

Volume — Situation — Direction. — A  small  elongated  muscle,  which  ap- 
pears to  belong  to  the  arm  rather  than  the  shoukler,  as  it  is  situated  at  the 
internal  face  of  the  humerus,  whose  direction  it  slightly  crosses.  If  it  is 
described  as  in  the  subscapular  region,  it  is  because  of  its  attachments  and 
action,  which  are,  in  every  respect,  analogous  to  those  of  the  other  muscles 
of  the  shoulder. 

Attachments — Form, — Structure. — ^It  commences  on  the  beak  of  the 
coracoid  process  by  a  small  flat  tendon,  which  is  at  first  included  between  the 
supraspinatus  and  subscapularis,  but  afterwards  leaves  the  interstice  formed 
by  these  two  muscles,  to  glide  and  be  inflected  over  the  terminal  tendon  of  the 
latter.  This  small  tendon  is  succeeded  by  two  muscular  branches,  one  deep, 
the  other  superficial.  The  first  is  a  wide,  thin,  and  short  band,  almost 
entirely  muscular,  attached  to  the  body  of  the  humerus  above  the  internal 
tuberosity.  The  second  forms  a  fleshy  body  of  a  certain  thickness,  flattened 
on  both  sides,  and  strongly  aponeurotic;  the  fasciculi  composing  it  are 
longer  as  they  are  more  posterior,  and  are  inserted,  by  their  inferior  extre- 
mities, into  the  imprints  on  the  anterior  face  of  the  humerus. 

Relations. — This  muscle  is  covered  by  the  coraco-radialis,  and  by  the 
sterno-trochineus,  which  is  partly  attached  to  its  tendon.  It  covers  the 
internal  insertion  of  the  subscapularis,  the  humerus,  the  common  tendon  of 
the  great  dorsal,  and  the  adductor  of  the  arm,  and  a  small  j)ortiou  of  the 
short  flexor  and  middle  extensor  of  the  fore-arm.  Its  posterior  border  is 
margined  by  the  vascular  and  nervous  trunks  on  the  inner  aspect  of  the  arm. 
The  anterior  humeral  nerve  passes  between  its  two  branches,  along  with  an 
arterial  and  venous  ramification. 

Action. — -It  is  an  adductor  of  the  arm,  and  makes  it  also  pivot  inwards. 
Its  direction  and  the  disposition  of  its  attachments  do  not  permit  it  to 
produce  rotation  outwards,  though  it  has  been  stated  to  do  so  by  several 
authors. 

4.  Small  Scapulo-Jiumeralis. 

(Synonyms. — Not  mentioned  by  Percivall.  Leyh,  in  addition  to  the  above  designation, 
names  it  the  tensor  of  the  capsular  ligament.) 

The  scapulo-humeralis  gracilis  is  a  very  small  cylindrical  fasciculus, 
comprised  between  the  large  extensor  of  the  fore-arm  and  the  capsule  of  the 
scapulo-humeral  articulation ;  deriving  its  origin  above  the  margin  of  the 
glenoid  cavity  of  the  scapula,  and  terminating  below  the  head  of  the  humerus 
by  a  thin  tendon,  which  insinuates  itself  between  the  fibres  of  the  short 
flexor  of  the  fore-arm.  This  muscle  apjiears  to  be  peculiar  to  Solipeds,  and 
has  been  regarded  by  Rigot  as  intended  to  raise  the  capsule  of  the  scapulo- 
humeral articulation  during  flexion,  so  as  to  prevent  its  being  pinched 
between  the  articular  sui'faces. 


DIFFERENTIAL   CHAKACTEES   OF  THE   MUSCLES   OF   TEE   SHOULDER   IN   OTHER   THAN   SOLIPED 

ANIMALS. 

The  Carnivora  are  the  only  animals  which  offer  somewhat  notable  differences  in 
the  muscles  of  the  shoulder. 

'J'hiis,  the  lont]  abductor  of  the  arm,  very  developed,  has  an  anterior  portion  arising 
directly  from  the  acromion,  and  a  posterior  portion  which  springs  from  the  whole  extent 


MUSCLES  OF  THE  ANTERIOR  LIMBS. 


255 


of  the  scapular  spine,  by  a  short  aponeurosis.  The  mperspinatus  is  considerable,  and 
terminates  in  a  single  branch  that  goes  to  the  grealt  trochanter. 

The  i-uhiipinatus  is  not  so  large  as  the  preceding,  and  is  also  undivided  at  its  inferior 
extremity :  it  is  the  inferior  branch  which  is  absent. 

The  coracoirrachialis  is  very  short,  and  comix)sed  of  a  single  fasciculus,  ■which 
terminates  above  the  hiuueral  insertion  of  the  adductor  of  the  arm. 

In  the  Pig,  the  disposition  of  this  muscle  is  the  same ;  it  is,  besides,  very  tendinous. 


COMPAniSON   OF  THE   MrSCLES  OF   THE   SHOULDER   OF   MAX   WITH   THOSE   OF   ANIMALS. 

As  muscles  of  the  shoulder,  there  are  only  described  the  deltoid,  suhspinatiis.  teres 
minor  and  major,  and  the  snhscapidaris ;  the  roraco-brachialis  being  included  in  the 
region  of  the  arm,  and  the  small  scapido-humeralis  is  absent  {see  Fig.  120). 

The  deltoid,  represented  in  part  by  the  long  abductor 
of  the  arm  of  Solipeds,  is  a  large,  triangular,  flat  muscle,  Fig.  120. 

that  covers  the  articulation  of  the  shoulder.     Its  fibres  are  . 

inserted  into  the  external  third  of  the  anterior  border 
of  the  clavicle,  the  external  border  of  the  acromion,  and 
the  inferior  border  of  the  scapular  spine  for  the  whole  of 
its  width ;  below,  it  is  attached,  through  the  medium  of  a 
tendon,  to  the  deltoid  imprint. 

By  their  disposition,  the  superspinatus,  suhspinatus, 
and  subscapularis  resemble  the  muscles  of  Carnivora 
The  teres  major,  after  establishing  relations  with  the  great 
dorsal,  as  in  Solipeds,  is  fixed  into  the  inner  lip  of  the 
bicipital  groove. 

MrSCLES    OF    THE   ABM. 

These  muscles,  grouped  around  the  humerus, 
are  attached  to  the  fore-arm  bv  their  inferior  ex- 
tremities. Those  situated  in  front  flex  this  por- 
tion of  the  limb,  while  those  behind  extend  it. 
The  fii'st  form  the  anterior  brachial  region,  the 
second  the  posterior  brachial  region. 

A.  Anterior  Brachial  Begion. 

This  region  is  composed  of  only  two  muscles, 
the  long  and  short  flexcns  of  the  fore-arm. 

1.  Lonq  Flexor  of  the  Fore-arm  or  BracMal 
Biceps.     (Figs.  85,  119,  121.) 

Synonyms. — Coraco-cubitalis,  or  coraco-radialis,  accord- 
ing to  Girard.  (Flexor  brachii — Percivall.  Scapulo-  or 
coraco-radialis — Leyh.) 

Preparation. — Place  the  limb  on  its  internal  face,  throw 
back  the  brachial  insertion  of  the  mastoido-hxuueralis, 
stemo-humeralis,  and  sterno-aponeuroticus,  over  the  ex- 
ternal muscles  of  the  fnre-arm;  excise,  lengthways,  the 
inferior  extremity  of  the  superspinatiis.  ito  show  the 
originating  lendon  of  the  muscle.  The  inferior  insertion 
may  be  studied  with  that  of  the  short  flexor  muscle. 

Form  —  Situation  —  Direction  —  Structure. — A 
long,  cylindrical  muscle,  thick  in  its  middle  portion,  bifid  inferiorly,  situated 
in  front  of  the  humerus,  in  an  oblique  direction  downwards  and  backwards, 
tendinous  at  its  two  extremities,  divided  by  a  great  number  of  strong  fibrous 
intersections,  one  of  which,  nearly  central  and  much  more  considerable  than 
the  others,  is  a  very  resisting  cord  that  traverses  the  muscle  throughout  its 
length,  and  becomes  continuous  with  the  tendons  at  its  extremities. 

Attachments. — This  muscle  has  its  origin  at  the  base  of  the  coracoid 


MUSCLES  OF  ANTERIOR  ASPECT 

OF  man's  upper  arm. 
1,  Coracoid  process  of  scapula  ; 
2,  Coraco-clavicular  liga- 
ment (trapezoid)  passing  up- 
ward to  clavicle ;  3,  Coraco 
acromial  ligament,  passing 
to  acromion ;  4,  Subscapu- 
laris ;  5,  Teres  major ;  6, 
Coraco-brachialis ;  7,  Bi- 
ceps ;  8,  Upper  end  of  ra- 
dius ;  9,  Brachialis  anticus  ; 
10,  Internal  head  of  triceps. 


256  TEE  MUSCLES. 

process  by  a  superior,  round,  and  thick  tendon  (Fig.  85,  6)  that  reaches  the 
bicipital  groove,  on  which  it  is  moulded  in  becoming  fibro-cartilaginous,  and 
over  which  it  glides  by  means  of  a  synovial  sac,  to  be  inflected  backwards 
and  confounded  with  the  body  of  the  muscle.  Its  inferior  tendon,  extremely 
short  and  strong,  terminates  on  the  superior  and  internal  tuberosity  of  the 
radius — the  bicipital  tuberosity — in  uniting  itself  to  the  capsular  ligament  of 
the  elbow  joint,  and  insinuating  itself  beneath  the  internal  ligament  of  this 
articulation.  At  its  origin,  this  tendon  gives  off  a  somewhat  resisting 
fibrous  band,  which  is  spread  over  the  surface  of  the  anterior  extensor  of 
the  metacarpus,  and  is  confounded  with  the  antibrachial  aponeurosis. 

Relations. — The  coraco-radialis  covers  an  adipose  cushion  which  sepa- 
rates it  from  the  capsule  of  the  scapulo-humeral  articulation,  the  anterior 
face  of  the  humerus,  the  coraco-humeralis,  and  the  articulation  of  the  elbow. 
It  is  covered  :  1,  By  the  superspinatus,  between  the  two  branches  of  which 
it  passes ;  2,  By  a  sj^ecial  aponeurotic  sheath,  whose  tensor  is  the  above- 
named  muscle,  with  the  sterno-trochineus  [see  Fig.  114,  12,  in  which  this 
aponeiu'osis  has  been  partly  preserved).  This  sheath  separates  the  coraco- 
radialis  from  the  mastoido-humeralis,  the  sterno-aponeuroticus,  and  from  its 
congener,  the  short  flexor. 

Action. — This  muscle  is  a  flexor  of  the  fore-arm,  and  a  tensor  of  the 
antibrachial  aponeurosis.  It  acts,  besides,  through  the  cord  which  traverses 
its  entire  length,  as  an  inextensible  band  that  mechanically  opposes  the 
flexion  of  the  scapulo-humeral  angle  while  the  animal  is  standing,  and  when 
the  fore-arm  is  maintained  fixed  by  the  contraction  of  the  humero-olecranian 
muscles. 

2.  Sliort  Flexor  of  the  Fore-arm.    (Fig.  85,  12.j 

Synonyms. — Humero-cubitalis  obliquus,  or  Iiumero-radialis — Girard.  {Uumeralls 
externus — Fercivall.     Iiumero-radialis — Leyh.) 

Preparation. — Lay  the  limb  on  its  internal  face,  and  remove  the  abductors  of  the 
arm,  the  subspiuatus,  and  the  large  and  short  extensors  of  the  fore-arm,  in  order  to 
expose  the  middle  and  upper  extremity  of  this  muscle.  Then  turn  the  limb  on  its 
external  fuce  to  dissect  the  inferior  extremity.  To  study  it  in  all  its  details,  it  is  a  good 
plan  to  cut  through  the  internal  ligament  of  the  ulnar  articulation,  and  those  muscles  of 
the  fore-arm  which  are  attached  to  the  epicondyle. 

Form — Structure — Situation — Direction. — This  is  a  very  thick  muscle, 
almost  entirely  fleshy,  voluminous  in  its  superior  part,  and  constricted 
infcriorly.  It  is  lodged  in  the  twisted  furrow  of  the  humerus,  the  direction 
of  which  it  exactly  follows  as  it  turns  round  the  bone  to  cover,  successively, 
its  posterior  face,  external  face,  anterior  face,  and  the  capsule  belonging  to 
the  elbow  articulation,  until  it  finally  reaches  the  inner  side  of  the  radius. 

Attachments. — The  muscular  fibres  entering  into  its  composition  have 
their  fixed  insertion  on  the  posterior  face  of  the  humerus,  below  the  articular 
head.  They  terminate,  inferiorly,  on  a  flat  tendon,  which  they  almost 
entirely  cover.  This  tendon  glides  in  a  transverse  groove  situated  on  the 
inner  face  of  the  radius,  below  the  bicipital  tuberosity,  and  afterwards 
passing  under  the  internal  ligament  of  the  elbow  joint,  it  divides  into  two 
very  short  fasciculi ;  one  of  these  goes  to  the  radius,  and  the  other  to  the 
ulna,  where  it  is  mixed  up  with  the  bundles  of  arciform  fibres,  which  unite, 
on  the  inner  side,  the  two  bones  of  the  fore-arm. 

Relations. — We  already  know  the  parts  this  muscle  covers.  It  is  covered, 
inwardly,  by  the  adductor  of  the  arm  and  the  middle  extensor  of  the  fore- 
arm ;  posteriorly  and  externally,  by  the  large  and  short  extensors  of  that 
ray.     Its  inferior  extremity,  comprised  between  the  anterior  extensor  of  the 


MUSCLES  OF  TEE  ANTERIOR  LIMBS. 


257 


metacarpus  and  the  coraco-radialis,  passes  below  the  antibrachial  band  of  the 
latter,  as  under  a  fibrous  bridge. 

Action. — It  is  simply  a  flexor  of  the  fore-arm. 


Fis.  121. 


INTERNAL  ASPECT  OF  LEFT  ANTERIOR  LIMB. 
1,  Prolonging  cartilage  of  scapula ;  2,  Inner  surface  of  scapula ;  3,  Subscapularis ; 
4,  Adductor  of  the  arm,  or  teres  major ;  5,  Supra-  or  antea-spinatus ;  6,  Long 
extensor  of  the  fore-arm,  or  portion  of  the  caput  magnum ;  7,  Large  extensor 
of  the  fore-arm,  the  other  portion  of  the  caput  magnum  ;  8,  Middle  extensor,  or 
caput  medium ;  9,  Humeralis  externus,  or  short  flexor  of  the  fore-arm ;  10, 
Coraco-humeralis ;  11,  Upper  extremity  of  humerus;  12,  Coraco-radialis,  or 
flexor  brachii ;  13,  Lower  extremity  of  humerus ;  14,  Brachial  fascia ;  15, 
Anterior  extensor  of  the  metacarpus,  or  extensor  metacarpi  magnus ;  16,  Belly 
and  aponeurotic  termination  of  the  flexor  brachii;  17,  Ulna;  18,  Ulnaris  acces- 
sorius,  or  oblique  flexor  of  the  metacarpeus ;  19,  Internal  flexor  of  the  meta- 
carpus, or  epicondylo-metacarpeus ;  20,  Radius;  21,  Tendon  of  the  oblique 
extensor ;  22,  Large  metacarpal  bone ;  23,  Flexor  tendons  of  the  foot ;  24,  Sus- 
pensory ligament ;  25,  Internal  rudimentary  metacarpal  bone ;  26,  Extensor 
tendon  of  the  foot ;  27,  Metacarpo-phalangeal  sheath  ;  28,  Lateral  cartilages  of 
the  foot ;  29,  Podophyllse. 


258  THE  MUSCLES. 

B.  Posterior  Brachial  Region. 

This  is  composed  of  five  muscles,  which  have  their  movable  insertion  in 
common  on  the  summit  of  the  olecranon,  and  are  consequently  designated 
olecranian  muscles.  With  reference  to  their  action,  they  are  also  designated 
extensors  of  the  fore-arm,  and  are  distinguished  into  long,  short,  middle,  and 
small. 

Preparation. — The  muscles  of  this  region  ought  to  be  studied  before  those  of  the 
preceding  region.  To  dissect  the  large  and  short  extensors,  it  is  necessary  to  lay  the 
limb  on  its  inner  face,  remove  the  slight  fibrous  layer  which  covers  these  two  muscles, 
and  raise  the  abductors  of  the  arm,  which  in  great  part  conceal  their  origin.  Tlie  limb 
is  kept  in  the  same  position  for  the  dissection  of  the  small  extensor,  which  is  not  easily 
accomplished,  as  it  is  almost  entirely  concealed  by  the  short  extensors  which,  besides, 
closely  adhere  to  it.  To  dissect  the  long  and  middle  extensors,  it  suffices  to  turn  the 
limb  on  its  external  surface  and  cut  away  the  vessels,  nerves,  and  lymphatics  which 
partly  cover  the  latter.  The  first,  lying  cl  >sely  to  the  internal  face  of  the  large  extensor, 
requires  some  care  in  order  to  free  it  from  its  aponeurosis. 

1.  Long  Extensor  of  the  Fore-arm.    (Fig.  121,  6.) 

Synonyms. — Scapulo-olecranius — Girard.  (A  portion  of  the  cajmt  magnum  of  the 
triceps  extensor  brachii—Percivall.     Long  scapulo-olecranius — Leyh.) 

Form — Situation. — This  is  a  wide  muscle,  flattened  within  and  without, 
and  applied  against  the  inner  face  of  the  large  extensor,  to  which  it  closely 
adheres. 

Structure  and  Attachments. — It  is  composed  of  an  aponeurosis,  attached 
to  the  posterior  border  of  the  scapula — -fxed  insertion :  and  a  muscular 
portion,  easily  divisible  into  two  fasciculi,  one  anterior,  the  other  posterior. 
These  two  fiisciculi  are  formed  of  vertical  fibres,  the  longest  of  which  are 
posterior,  and  terminate  at  the  posterior  border  of  the  ulna,  as  well  as  on 
the  antibrachial  aponeurosis — movable  insertion, 

Relations. — Outwards,  with  the  large  and  middle  extensors;  inwards, 
with  the  sterno-trochineus,  the  adductor  of  the  arm,  and  the  great  dorsal. 
Its  aponeurosis  adheres  closely  to  the  tendinous  portion  which  terminates 
the  last-named  muscle,  and  its  anterior  border  is  united  to  the  aponeurotic 
sheath  of  the  coraco-radialis  by  a  particular  fibrous  fascia,  which  covers  the 
vessels  and  nerves  on  the  inner  aspect  of  the  arm. 

Action. — It  extends  the  fore-arm,  and  renders  the  antibrachial  aponeurosis 
tense. 

2.  Large  Extensor  of  the  Fore-arm.    (Figs.  119,  7;  121,  7.) 

Synonyms. — Scapulo-olecranius  major — Girard.  The  long  portion  of  the  triceps 
brachialis  of  Man.  (Portion  of  the  caput  magnum  of  the  triceps  extensor  brachii — 
Feruivall.) 

Volume— Form — Situation. — An  enormous,  short,  and  triangular  muscle, 
occupying,  with  the  short  extensor,  the  space  comprised  between  the 
posterior  border  of  the  scapula  and  the  humerus. 

Structure  and  Attachments.— The  fleshy  mass  constituting  this  muscle  is 
formed  of  very  thick  fasciculi,  among  which  are  found  some  aj^oneurotic 
bands.  These  fasciculi  have  their  origin  on  the  dorsal  angle  and  the  axillary 
border  of  the  scapula,  either  directly,  or  through  the  medium  of  two  strong 
fibrous  layers,  between  which  they  are  at  first  included.  They  are  afterwards 
directed  backwards  and  downwards,  and  converge  towards  a  thick  tendon 
which  occupies  the  posterior  and  inferior  angle  of  the  triangle  represented 
by  this  muscle.     The  tendon  terminates  by  attaching  itself  to  the  summit  of 


MUSCLES  OF  THE  ANTERIOR  LIMBS.  259 

the  olecranon,  after  receiving  a  great  munber  of  fibres  from  the  short  extensor, 
and  after  gliding,  by  moaus  of  a  synovial  capsule,  over  the  eminence  which 
serves  for  its  insertion. 

Relations. — The  external  surface  is  covered  by  a  thin,  fibrous,  white-and- 
yellow  elastic  layer,  which  separates  it  from  the  panniculus ;  it  is  hollowed, 
near  the  upper  border  of  the  muscle,  by  an  excavation  into  which  is  received 
the  posterior  portion  of  the  long  abductor.  Its  internal  face  responds  to 
the  great  dorsal,  the  adductor  of  the  arm,  and  to  the  long  extensor.  Its  posterior 
border  is  margined  by  the  latter  muscle ;  the  superi(u- follows  the  axillary 
border  of  the  scapula,  and  is  attached  to  it  to  constitute  the  fixed  insertion 
of  the  muscle ;  the  inferior  responds  to  the  short  and  middle  extensors. 

Action. — It  is  an  extensor  of  the  fore- arm. 

3.  Short  Extensor  of  tU  Fore-arm.    (Fig.  119,  8.) 

Synonyms. — Humero-olecranius  exteinns  —  Girard.  The  vastus  externus  of  the 
triceps  brachialis  of  Man.     {Caj)ut  medium — Percirall.) 

Situation  —  Direction  —  Form  —  Structure.  —  This  muscle  is  situated 
between  the  humerus  and  the  inferior  border  of  tbe  preceding,  and  is 
directed  oV)liquely  downwards  and  backwards.  It  is  thick  and  short, 
flattened  and  aponetirotic  at  its  upper  extremity,  prismatic,  and  entirely 
formed  of  thick  parallel  muscular  fasciculi  for  the  remainder  of  its  extent. 

Attachments. — One  of  its  attachments  is  on  the  humerus,  to  the  curved 
line  extending  from  the  deltoid  imprint  to  the  base  of  the  articular  head 
(see  for  this  line  Fig.  41,  above  4),  by  the  short  aponeurosis  of  its  superior 
extremity — fxcd  insertion  ;  the  other  is  to  the  olecranon,  either  directly,  or 
through  the  tendon  of  the  large  extensor — movable  insertion. 

Belations. — The  prismatic  shape  of  this  muscle  oflers  three  faces,  which 
respond :  externally,  to  the  two  abductors  of  the  arm  and  to  a  slight  fibrous 
layer  continuous,  above,  with  that  which  covers  the  large  extensor,  and  below, 
with  the  antibrachial  aponeurosis ;  internally,  to  the  small  extensor,  from 
which  it  is  difficult  to  separate  it,  to  the  short  flexor  of  the  fore-arm,  and  to 
the  anterior  extensor  of  the  metacarpus ;  suj^eriorly,  to  the  large  extensor, 
which  closely  adheres  to  it. 

Action. — An  extensor  of  the  fore-arm. 

4.  Middle  Extensor  of  the  Fore-arm.    (Figs.  119,  17  ;  121,  8.) 

Synonyms. — Humero-olecranius  intemus—Girard.  The  vastus  internus  of  the 
triceps  brachialis  of  Man.     (Caput  parvum — Percivall.) 

Situation — Direction — Form — Structure. —  This  muscle  is  situated  at 
the  internal  face  of  the  humerus,  along  the  inferior  border  of  the  large 
extensor.  It  is  oblique  downwards  and  backwards,  pyriform,  bulging  at  its 
superior  extremity,  contracted  infericrly,  vrhere  it  terminates  by  two  small 
flat  tendons. 

Attachments.— It  originates,  by  its  superior  extremity,  from  the  inner 
aspect  of  the  humerus,  behind  and  above  the  tuberosity  on  its  body.  One 
of  its  terminal  tendons  is  attached  to  the  summit  of  the  olecranon  :  the 
other  glides  over  a  small  convexity  on  the  inner  side  of  that  eminence,  and 
goes  to  be  inserted  a  little  lower  than  the  first. 

Belations. — Above,  with  the  inferior  border  of  the  large  extensor ;  out- 
wards, with  the  humerus,  the  short  flexor,  and  short  extensor  of  the  fore- 
arm; inwards,  with  the  humeral  insertion  of  the  great  dorsal  and  the 
adductor  of  the  arm,  the  long  branch  of  the  coraco-brachialis,  the  vessels 


260 


THE  MUSCLES. 


Fis.  122. 


and  nerves  on  the  inner  side  of  the  arm,  and 
the  long  extensor  of  the  fore-arm. 

Action. — An  extensor  of  the  fore-arm. 

5.  Small  Extensor  of  the  Fore-arm  or  Anconeus. 
(Fig.  85,  10.) 

Synonym. — Humero-olecranius  minor —  Girard. 

Form  —  Structure  —  Sitnation — Relations. — 
This  is  a  small,  thick,  and  prismatic  muscle, 
almost  entirely  fleshy,  situated  behind  the  elbow 
articulation.  It  is  apjilied  against  the  synovial 
cul-de-sac  which  ascends  into  the  olecranian 
fossa,  and  to  which  it  is  strongly  attached ;  it 
is  hidden  by  the  short  extensor,  from  which  it  is 
not  easily  distinguished. 

Attachments. — It  originates  from  the  margin 
of  the  olecranian  fossa,  chiefly  above  and  out- 
wards. It  terminates  by  being  inserted  into  the 
anterior  and  external  part  of  the  olecranon. 

Action. — This  little  muscle,  a  congener  of  the 
preceding,  raises  the  articular  capsule  it  covers, 
and  prevents  its  being  pinched  between  the  bony 
surfaces. 

DIFFERENTIAL   CHARACTERS   OF   THE   MUSCLES   OF   THE 
AKM    IN   OTHEU   THAN   SOLIPED    ANIMALS. 

In  all  animals,  the  loixj  flexor  of  the  fore-arm,,  or 
coraco-radialis,  is  less  thick  and  tendinous  than  in  iSoli- 
peds. 

In  the  Pig,  Dog,  and  Cat,  it  comiDorts  itself  in  a 
special  manner  at  its  inferior  extremity ,  it  is  attached 
at  first  to  the  bicipital  tuberosity,  and  also  furnishes  a 
small  tendinous  branch  which  glides  over  the  inner  side 
of  the  radius  by  means  of  a  synovial  burta,  and  is  fixed 
within  the  ulna,  towards  the  base  of  the  olecranon. 

The  short  flexor  of  the  fore-arm,  or  anterior  brachial, 
is  terminated,  in  the  Pig,  Dog,  .^nd  Cat,  by  a  small 
tendon  which  is  fixed  in  the  ulna,  below  the  ulnar 
branch  of  the  coraco-radialis. 

The  long  extensor  of  the  fore-arm,  which  is  found  in 
all  the  domesticated  animals,  arises  from  the  external  face 
of  the  great  dorsal  in  the  Pig  and  Dog.  The  middle 
extensor  of  the  fore-arm  and  anconeus  of  these  animals 
are  remarkable  for  their  volume. 


COMPAUISON   OF   THE   MUSCLES   OF   THE   ARM   OF  MAN 
WITH  THOSK  OF   ANIMALS. 

In  Man,  three  muscles  are  situated  in  front  of  the 


DEEP  MUSCLES  ON  EXTERNAL 
ASPECT  OF  RIGHT  ANTERIOR 
LIMB. 

T,  Scapula  ;  2,  Coracoid  process 
of  scapula ;  3,  Flexor  brachii ; 
4,  Superior  extremity  of  humerus ;  5,  External  tuberosity  of  humerus ;  6,  Humeralis 
esternus  ;  7,  Body  of  humerus  ;  8,  Biceps  ;  9,  Aiiterior,  or  great  extensor  of  the  meta- 
carpus ;  10,  Ulna  ,  11,  Extensor  pedis,  or  anterior  extensor  of  the  phalanges  ;  12,  Uluaris 
accessorius,  or  ulnar  portion  of  the  perforans ;  13,  Lateral  extensor  of  the  metacar- 
pus, or  extensor  suffraginis ;  14,  Oblique  extensor  of  the  metacarpus ;  15,  Flexors  of 
the  foot;  16,  Trapezium ;  17,  Annular  ligament;  18,  Carpal  ligament  of  perforans 
tendon,  20;  19,  Perforatus;  21,  Tendon  of  anterior  extensor  of  metacarpus  ;  22,  Small 
metacarpal  bone  ;  23,  Suspensory  ligament ;  24,  Lateral  band  of  metacarpo-phalangeal 
sheath ,  25,  Perforans  teadou ;  26,  Branch  of  the  suspensory  ligament  joining  the 
extensor  pedis,  27, 


MUSCLES  OF  THE  ANTERIOR  LIMBS.  261 

hiunerus  :  the  biceps,  coraco-hrachialis,  and  the  anterior  brachialis ;  behind  are  found 
the  triceps  brachialis  and  tlie  anconeus. 

The  biceps,  which  corresponds  to  the  coraco-radialis  of  animals,  commences  on  the 
capula'  by  two  heads,  which  unite  towards  the  upper  part  of  the  humerus.  The  lono- 
or  tiou  is  detached  fiom  the  upper  part  of  the  rim  of  the  glenoid  cavity ;  the  shortest 
commences  from  the  summit  of  the  coracoid  process.  The  infer. or  tendon  of  the  biceps 
givt  s  otf,  before  fixing  itself  on  the  bicipital  tuberosity,  a  fibrous  lamella  which  is  con- 
founded with  the  antibiadiial  aponeurosis. 

Tlie  coraro-brachialis  has  only  one  fleshy  borly. 

As  in  the  Carnivora  and  Pig,  the  anterior  brachialis  terminates  on  the  ulna,  below 
the  coronoid  process. 

The  triceps  brachialis  exactly  represents,  by  its  three  heads,  the  large,  middle,  and 
short  exten.sors  of  the  fore-arm  of  animals      (See  Fig.  120  ) 

There  is  nothing  particular  with  regard  to  the  anconeus.  The  long  extensor  of  the 
fore-arm  of  the  Horse  has  no  representative  in  Man. 

MUSCLES    OF    THE    FORE-ARM. 

These  muscles,  nine  in  number,  distributed  in  two  regions — anterior  and 
posterior — envelop  the  bones  of  the  fore-arm  on  every  side  except  the 
internal,  where  the  radius  is  in  mediate  contact  with  the  skin.  They  all 
terminate  on  the  different  sections  of  the  foot,  which  they  flex  or  extend, 
and  are  contained  in  a  common  fibrous  sheath,  which  constitutes  the  anti- 
brachial  aponeurosis, 

Antibrachial  Aponeurosis. 

This  retaining  fascia  forms  a  very  strong  and  resisting  envelope,  which 
is  firmly  fixed  around  the  antibrachial  muscles  by  the  insertions  it  has  on 
the  bones  of  the  fore-arm,  being  attached  to  the  olecranon,  the  internal  aspect 
of  the  radius,  and  to  the  inferior  extremity  of  that  bone,  both  inwards  and 
outwards. 

Its  external  face  is  covered  by  superficial  vessels  and  nerves,  that  are 
separated  from  the  skin  by  a  very  thin  fibrous  layer,  which  is  more 
particularly  observable  on  the  inner  side,  where  it  covers  the  antibrachial 
aponeurosis  in  a  very  evident  manner ;  it  is  rendered  tense  by  the  sterno- 
aponeuroticus.  Up  to  the  present  time,  this  fibrous  layer  has  not  been 
distinguished  from  the  aponeurosis  it  covers.  The  inner  face  of  the  latter 
gives  rise  to  several  septa,  which  penetrate  the  interstices  of  the  muscles  to 
form  around  some  of  them  special  retentive  sheaths ;  it  adheres  to  several 
of  them  very  intimately.  At  its  upper  border,  this  aponeurosis  receives, 
inwardly,  the  insertion  of  the  long  extensor  of  the  fore-arm ;  in  front,  the 
accessory  band  of  the  coraco-radialis ;  outwardly,  it  is  continuous  with  the 
fibrous  fascia  covering  the  external  face  of  the  olecranian  muscles.  Inferiorly, 
it  is  prolonged  around  the  knee  to  form  the  tendinous  sheaths  in  that 
region. 

The  antibrachial  aponeurosis  is  made  tense  by  the  contraction  of  the 
long  extensor  of  the  fore-arm  and  the  coraco-radialis.  With  reference  to 
the  sterno-aponeuroticus,  which  has  hitherto  been  regarded  as  intended  to 
play  the  same  part,  it  can  only  act  on  the  fibrous  fascia  which  covers, 
externally,  the  antibrachial  aponeurosis. 

Preparation  of  the  muscles  of  the  fore-arm. — The  preparation  of  these  muscles  is 
extremely  simple,  as  it  suffices  to  remove  tlie  antibrachial  aponeurosis'  and  the  interstitial 
cellulo-adipose  tissue,  to  expose  and  to  isolate  them  from  each  other.  No  special 
recommendations  need,  therefore,  be  given,  as  a  glance  at  figures  89.  119,  121,  and  122 
will  guide  the  student  in  his  dissection,  and  supplement  the  njanual  details  which  would 
be  superfluous  here. 

Nevertheless,  as  the  terminal  insertions  of  some  of  these  muscles  are  inclosed  within 
the  hoof,  and  as  it  is  indispensable,  in  order  to  expose  them,  to  remove  this  horny  case, 
Bome  explanation  will  be  given  as  to  the  manner  in  which  this  should  be  eflected, 
20 


262  TEE  MUSCLES. 

particulnrly  as  the  apparent  difficulty  and  labour  too  frequently  cause  this  part  to  be 
omitttd  in  the  dissecting  rooms. 

1.  The  instruments  necessary  to  remove  the  hoof  are .  a  scalpel,  toe-knife,  hammer, 
and  a  pair  of  pincers. 

2.  Tlie  limb  should  be  in  a  vertical  position,  held  by  one  or  two  assistants,  and  the 
foot  placed  on  a  table,  stool,  or  very  solid  block  of  wood. 

3.  Pass  the  scalpel  as  deeply  as  possible  around  the  coronet,  to  separate  the  wall  of 
the  hoof  trom  the  organised  tissues. 

4.  With  tlie  knife  and  hammer,  split  the  wall  into  four  or  five  pieces  by  vertical 
incisions. 

5.  When  the  wall  is  thus  divided,  it  is  sufficient  to  insert  the  knife  under  the  frag- 
ments, and  making  it  serve  as  a  lever,  tear  them  olf ;  pincers  may  also  be  used  fur  tliia 
purpose,  each  of  the  pieces  being  twisted  from  the  sole. 

6.  To  remove  the  sole,  the  blade  of  the  scalpel  sliould  be  passed  between  its  upper 
face  and  the  plantar  surface  of  the  third  phalanx;  afterwards  the  toe-knife  may  be 
inserted  in  tlie  interval  at  the  bulbs  of  the  frog,  so  as  to  slightly  raise  the  external 
border  of  the  sole.  This  is  thin  seized  by  the  pmcers  and  pulled  oft',  along  with  the 
frog,  in  a  single  piece,  by  a  powerful  twisting  movement,  aided  by  the  as.-iistauts,  who 
press  on  the  limb  in  a  contrary  direetiou. 

A.  Anterior  Antihrachial  Begion. 

In  SoUpeds,  this  region  includes  four  extensor  muscles.  Two  act  on  the 
entire  foot ;  these  are  the  anterior  extensor  and  tlie  oblique  extensor  of  the 
metacarpus.  Two  others,  the  anterior  and  lateral  extensor  of  the  phalanges, 
terminate  in  the  digital  region. 

1.  Anterior  Extensor  of  the  Metacarpus.    ('Figs.  119, 11 ;  121, 15;  122,  9.) 

Synonyms. — Epicondylo-premetacarpeus — Girard.  It  represents  the  two  external 
radials  of  Man.  (Extensor  metacarpi  magnus  —  PerciviU.  Hamero-metacarpeus  — 
Leyh.) 

Situation — Direction — Form — Structure. — The  anterior  extensor  of  the 
metacarpus,  situated  in  front  of  the  radius,  in  an  almost  vertical  direction, 
is  composed  of  a  muscular  body  and  a  tendon.  The  first  has  the  form  of  an 
inverted  cone,  is  intersected  by  some  aponeurotic  lamellte,  and  is  composed 
of  muscular  fibres  slightly  arciform  at  their  superior  extremities.  The 
second,  at  first  rounded,  then  flattened,  commences  below  the  middle  third 
of  the  radius,  and  succeeds  the  inferior  extremity  of  the  muscular  portion. 

Attachments.-  This  muscle  has  its  fixed  insertion  :  1,  By  the  upper  ex- 
tremity of  its  fleshy  fibres,  on  the  crest  that  limits,  behind  and  below,  the 
furrow  of  torsion  of  the  humerus ;  2,  Above  and  in  front  of  the  inferior 
articular  surface  of  the  humerus,  by  means  of  a  strong  fibrous  band  common 
to  it  and  the  anterior  extensor  of  the  phalanges,  and  which  expands  on  the 
deep  face  of  these  two  muscles  in  becoming  intimately  united  with  the 
capsular  ligament  of  the  elbow  articulation.  Its  movable  insertion  takes 
place  on  the  anterior  and  superior  tuberosity  of  the  large  metacarpal  bone, 
by  the  inferior  extremity  of  its  tendon. 

Belations.— The  muscular  portion  is  covered  by  the  antihrachial 
aponeurosis  and  the  short  extensor  of  the  fore-arm.  It  covers  the  anterior 
face  of  the  radius,  as  well  as  the  elbow  articulation ;  outwards  and  behind, 
it  is  in  contact  with  the  inferior  extremity  of  the  short  flexor  of  the  fore- 
arm or  brachialis  anticus,  whose  aponeurosis  adheres  intimately  to  the 
arciform  portion  of  the  fibres  of  the  anterior  extensor  of  the  metacarpus, 
and  appears  to  attach  this  muscle  to  the  deltoid  imprint.  Its  tendon 
covers  a  small  portion  of  the  anterior  aspect  of  the  radius,  and  enters  the 
internal  vertical  groove  channeled  in  front  of  the  inferior  extremity  of  that 
bone ;  afterwards  it  passes  over  the  capsular  ligament  of  the  carpus,  and  is 


MUSCLES  OF  THE  ANTERIOR  LIMBS.  263 

maintained  against  that  membranous  expansion  by  a  wide  fibrous  sheath, 
through  which  it  glides  by  the  aid  of  two  synovial  membranes.  This 
tendon  is  crossed  above  the  knee  by  that  of  the  oblique  extensor,  which 
passes  to  its  surface. 

Action. — The  name  of  this  muscle  indicates  its  function ;  it  extends  the 
metacarpus  on  the  fore-arm. 

2.  Obliqtie  Extensor  of  the  Metacarpus.     (Figs.  119,  13;  121,  21 ;  122,  14.) 

Synonyms. — Cubitoprenietacarpeus,  or  radio-premetacarpeus — Girard.  It  is  the 
representative  of  the  long  abductor  and  short  extensor  of  the"  thumb  in  Man.  {Extensor 
metacarpi  oLliquus  vd  parvus — Fercivall.     Radio-metacarpeus — Leyh.) 

Situation — Form — Structure — Direction. — A  small  muscle  situated  at  the 
internal  side  of  the  radius,  beneath  the  anterior  extensor  of  the  phalanges, 
penniform  in  shape,  strongly  aponeurotic,  and  terminated  by  a  tendon  which 
turns  obliquely  round  the  anterior  aspect  of  the  radius  in  passing 
downwards  and  inwards,  to  reach  the  oblique  channel  on  the  inferior 
extremity  of  that  bone,  and  to  pass  from  thence  to  the  inside  of  the  knee. 

Attachments. — It  has  its  origin  on  the  external  side  of  the  radius  ;  its 
terminal  tendon  is  fixed  into  the  head  of  the  internal  metacarpal  bone,  by 
its  fibres  becoming  confounded  with  those  of  the  internal  ligament  of  the 
carpus. 

Relations. — This  muscle  is  covered  by  the  anterior  extensor  of  the 
phalanges  and  the  antibrachial  aponeurosis.  It  successively  covers  the 
anterior  face  of  the  radius,  the  tendon  of  the  anterior  extensor  of  the 
metacarpus,  the  radial  groove  lodging  its  tendon,  and  in  which  it  glides 
by  means  of  a  small  synovial  bm'sa,  as  well  as  the  internal  ligament  of  the 
carpus. 

Action. — It  extends  the  metacarpus,  and  may  make  it  pivot  from  within 
forwards. 

3.  Anterior  Extensor  of  the  Phalanges.     (Figs.  119,  14;  121,  15  :   122,  9.) 

Synonyms. — Epicondylo-prephalangeus — Girard.  The  extensor  communis  digitorum 
of  Man.     {Extensor  pedis — Perciiall.     Humero-prephalangeus — Leyh.) 

Situation — Direction — Extent — Farm — Structure. — This  is  a  long  vertical 
muscle,  situated  external  to,  and  behind  the  anterior  extensor  of  the  metacarpus, 
which  it  resembles  in  being  composed  of  a  fleshy  and  a  tendinous  portion. 
The  musculai-  portion  extends  from  the  inferior  extremity  of  the  humerus  to 
above  the  lower  third  of  the  radius ;  it  is  fusiform  in  shape,  intersected  by 
aponeurotic  lamellse,  and  bifid  at  its  superior  extremity.^  The  tendinous 
portion  forms  two  unequal  cords,  which  succeed  the  two  terminal  branches 
of  the  muscular  part,  and  lie  close  to  each  other.  These  two  cords  enter 
the  most  external  of  the  three  grooves  in  front  of  the  inferior  extremity  of 
the  radius,  and  reach  the  anterior  face  of  the  carpal  capsular  ligament, 
against  which  they  are  maintained  by  an  annular  ligamentous  apparatus. 
After  passing  from  beneath  this  ring,  the  smallest,  which  is  the  most  external, 
joins  the  tendon  of  the  lateral  extensor  (Fig.  119,  15).  The  principal  branch 
(Fig.  119,  14' )  continues  its  course  on  the  anterior  aspect  of  the  midd.e 
metacai-pal  bone  and  articulation  of  the  fetlock,  until  it  arrives  in  front  cf 
the  digit ;  here  it  terminates  on  the  os  pedis,  after  widening  in  a  remarkable 
manner,  and  after  receiving,  laterally,  at  the  middle  of  the  first  phalanx,  a 

'  This  division,  which  has  been  noticed  by  several  writers,  has  not  been  shown  in 
figure  119.     This  is  a  mistake,  as  it  is  constantly  prtseut. 


i2G4  THE  MUSCLES. 

reinforcing  band  wliicli  appears  to  be  given  off  from  the  inferior  extremity 
of  the  suspensory  ligament  of  the  fetlock. 

Attachments. — The  anterior  extensor  of  the  phalanges  has  its  fixed  attach- 
ment by  the  superior  extremity  of  its  muscular  body  :  1,  Below  the  crest 
tliat  limits,  posteriorly,  the  furrow  of  torsion  of  the  humerus ;  2,  In  front 
of  the  inferior  extremity  of  the  humerus ;  3,  To  the  anterior  border  of  the 
external  ligament  of  the  elbow  joint ;  4,  To  the  external  and  superior 
tuberosity  of  the  radius ;  5,  To  the  external  border  of  that  bone.  Its 
princijial  tendon  is  inserted  into  the  pyramidal  eminence  of  the  third  phalanx, 
after  being  successively  attached  to  the  capsular  ligament  of  the  fetlock 
joint  and  the  anterior  surfaces  of  the  first  two  phalanges. 

Belations. — The  muscular  portion,  covered  by  the  antibrachial  aponeu- 
rosis, covers  the  articulation  of  the  elbow,  the  anterior  face  of  the  radius, 
and  the  oblique  extensor  of  the  metacarpus ;  it  responds,  in  front,  to  the 
anterior  extensor  of  the  same  ray,  to  which  it  is  intimately  attached  by  its 
ujjper  half ;  behind,  to  the  lateral  extensor  of  the  i)halanges.  The  tendinous 
cords  cover  the  difl'erent  parts  already  enumerated  in  describing  the  course 
of  the  muscle — that  is,  the  anterior  face  of  the  radius,  the  carj^al  joints,  the 
principal  metacarpal  bone,  the  articulation  of  the  fetlock,  and  the  first  two 
phalanges.  A  vaginal  synovial  membrane  envelops  them  at  the  knee,  to 
facilitate  their  gliding  in  the  radial  groove  and  on  the  anterior  asjject  of 
the  capsular  ligament  of  the  carpus ;  while  the  inner  surface  of  the  prin- 
cipal tendon  is  covered,  in  front  of  the  fetlock,  by  a  small  vesicular 
capsule,  and  still  lower  by  the  synovial  membranes  of  the  two  inter- 
phalangeal  articulations. 

Action. — This  muscle  extends  the  third  phalanx  on  the  second,  that  on 
the  first,  and  this  again  on  the  metacarpal  bone.  It  may  also  concur  in  the 
extension  of  the  entire  foot  on  the  fore-arm. 

(Two  small  muscles,  which  should  be  only  considered  as  heads  of  this 
anterior  extensor,  have  been  particularly  described  by  Thiernesse  and 
Phillips,  and  named  after  these  authors. 

The  muscle  of  Phillips,  according  to  Leyh,  is  long  and  thin  ;  it  commences 
on  the  lateral  external  ligament  of  the  ulnar  articulation  and  the  external 
superior  tuberosity  of  the  radius ;  it  is  directed  obliquely  downwards  and 
forwards,  lying  beside  the  muscular  poi'tion  of  the  common  extensor. 
Towards  the  middle  and  outer  aspect  of  the  radius,  it  gives  off  a  small 
tendon,  which  passes  in  the  same  sheath  as  the  preceding,  in  front  of  the 
carpus,  and  continues  its  course  between  the  two  tendons  of  the  extensors 
of  the  phalanges  to  near  the  fetlock,  where  it  becomes  confounded  with  that 
of  the  lateral  extensor,  a  little  above  the  first  phalanx.  , 

The  muscle  of  Thiernesse  is  smaller  than  that  of  Phillips,  and  situated  at 
its  inner  side.  It  arises  in  front  of  the  transverse  ligament  of  the  ulna  by  a 
muscular  portion,  becomes  thinner  as  it  descends,  and  terminates  by  a  fine 
tendon  which  is  confounded  with  that  of  the  common  extensor,  towards  ths 
lower  third  of  the  fore-arm.) 

4.  Lateral  Extensor  of  the  Phalanges.     (Figs.  119,  16  ;  122,  13.) 

Synonyms. — Cubito  or  radialis-prephalangeus,  according  to  Girard.  The  extensor 
miuimi  digiti  of  Man.     (^Extensor  suffraginu — Fercivall.) 

Direction — Situation — Extent— Form— Structure. — A  small  vertical  muscle, 
situated  at  the  external  side  of  the  fore-arm,  between  the  jjreceding  and 
the  external  flexor  of  the  metacarpus,  and  formed  of  a  fleshy  body  and  a 


MUSCLES  OF  THE  ANTERIOR  LIMBS.  265 

tendon.  The  fleshy  body,  not  very  considerable,  and  flattened  from 
before  backwards,  extends  from  the  upper  extremit}-  of  the  radius  tu 
the  lower  fourth  of  the  same  bone.  The  tendon  (Fig.  119,  16'),  at  first 
rounded,  then  flattened,  reaches  the  gliding  groove  which  divides  the 
external  inferior  tuberosity  of  the  radius  into  two  portions,  passes  to  the 
external  side  of  the  carpus,  crossing  the  lateral  ligament  common  to  the  articu- 
lations of  this  region,  and  arrives  at  the  anterior  surface  of  the  princijial  meta- 
carpal bone,  where  it  receives  the  small  tendinous  branch  detached  from  the 
anterior  extensor,  as  well  as  a  strong  fibrous  band  coming  from  the  external 
side  of  the  carjms  fFig.  119,  17).  Afterwards,  descending  alongside  the 
external  border  of  tbe  prmcipal  tendon  of  its  congener,  and  imited  to  it  by  a 
fibrous  fascia,  it  gains  the  articulation  of  the  fetlock,  and  expanding,  ter- 
minates at  the  upper  extremity  of  the  first  phalanx. 

Attachments. — 1,  By  its  muscular  body,  to  the  external  tuberosity  of  the 
radius,  the  external  ligament  of  the  elbow  articulation,  and  to  the  bodies  of  the 
two  bones  of  the  fore-arm — origin  ;  2,  By  the  inferior  extremity  of  its  tendon, 
to  the  capsule  of  the  metacarpo-phalangeal  articulation,  and  in  front  of  the 
superior  extri-mity  of  the  first  phalanx — termination. 

Relations. — Its  muscular  portion,  enveloped  in  a  special  aponeurotic 
sheath,  responds :  in  front,  to  the  anterior  extensor  of  the  phalanges  ;  behind, 
to  the  external  flexor  of  the  metacarpus  and  the  perforatus  and  perforans 
muscles  ;  outwards,  to  the  antibrachial  aponeurosis.  The  tendon,  surrounded 
by  a  vaginal  synovial  sheath,  in  passing  over  the  cari)us,  covers,  beyond  the 
knee,  the  anterior  aspect  of  the  metacarpus,  and  the  anterior  ligament  of  the 
metacarpo-phalangeal  articulation,  over  which  it  glides  by  means  of  a  small 
vesicular  synovial  bursa.  It  is  covered  by  a  slight  fibrous  fascia,  which 
separates  it  from  the  skin,  and  which  is  also  spread  over  the  tendon  of  the 
anterior  extensor. 

Action. — This  muscle  is  an  extensor  of  the  digit,  and  also  concurs  in  the 
extension  of  the  entire  foot  on  the  fore-arm. 

B.  Posterior  Antibrachial  Region. 

This  is  composed  of  five  flexor  muscles  grouped  vertically  behind  the 
bones  of  the  fore-arm.  Three  are  situated  superficially,  and  act  on  the  whole 
foot ;  these  are  the  external  flexor,  oblique  flexor,  and  the  internal  flexor  of 
the  metacarpus.  The  other  two,  fixed  to  the  digit  by  their  inferior  extremity, 
and  covered  by  the  preceding,  are  designated  the  superficial  and  deep  flexors 
of  the  phalanges. 

1,  External  Flexor  of  the  Metacarpus,  or  Posterior  Ulnaris.^     (Fig.  119,  18.) 

Si/nouyms. — Epicoudylo-supeicarpeus — Girard.  {Flexor      metacarpi      externus — 

Percivall.     Humero-supercarpeus  exttrnus — Leyh.) 

Situation. — The  external  flexor  of  the  metacarpus  is  situated  at  the  ex- 
ternal side  of  the  fore-aim,  between  the  lateral  extensor  of  the  phalanges 
and  the  oblique  flexor. 

Form — Structure — Attachments. — This  muscle  is  elongated  from  above  to 
below,  flattened  from  one  side  to  the  other,  thick  in  its  middle  part,  and 
intersected  by  very  strong  aponeurotic  bands.     It  commences  on  the  summit 

•  It  is  known  that  the  bony  eminences,  hitherto  termed  in  veterinary  anatomy 
"  epitrochlea  "  and  '■  epicondyle,"  correspond .  the  first,  to  the  epicondyle  of  IMan,  the  second, 
to  the  epitrochlea.  It  ne^d  excite  no  surprise,  therefore,  to  see  the  denominations  given 
by  Girard  to  the  muscles  of  the  posterior  antibrachial  region  changed  as  above. 


266  THE  MUSCLES. 

of  the  epicondyle  by  a  very  powerful,  but  extremely  short  teudon.  In- 
feriorly,  it  terminates  by  a  second  tendon  longer  than  the  preceding,  and 
divides  into  two  branches,  an  anterior  and  a  posterior.  The  latter  (Fig.  119, 
20),  short  and  wide,  is  inserted  into  the  supercarpal  bone  in  becoming  mixed 
up  with  the  oblique  flexor.  The  former  (Fig.  1 19, 19),  rounded  and  funicular 
in  shape,  glides  by  means  of  a  synovial  bursa  in  the  channel  excavated  on 
the  external  aspect  of  the  supercarpal  bone,  and  which  is  converted  into 
a  canal  by  a  little  fibrous  apparatus ;  this  branch  is  afterwards  fixed  on  the 
head  of  the  external  metacarpal  bone  by  being  confounded  with  the  external 
ligament  of  the  carpus. 

Eelations. — Covered  by  the  antibrachial  aponeurosis,  this  muscle  covers 
the  two  flexors  of  the  digit.  Its  anterior  border  responds  to  the  lateral 
extensor  of  the  phalanges ;  the  posterior  to  the  oblique  flexor.  Its  superior 
tendon  lies  behind  the  external  ligament  of  the  elbow  joint,  and  is  covered 
deeply  by  the  external  cul-de-sac  of  the  synovial  capsule  belonging  to  that 
articulation. 

Action. — It  flexes  the  foot  on  the  fore-arm.  (Leyh  observes  that  it  is 
more  particularly  concerned  in  what  is  known  as  "high  action.") 

2.   Oblique  Flexor  of  the  Metacarpus,  or  Anterior  Ulnar  is.    (Fig.  121,  19.) 

Synonyms. — Epitrochlea  supercarpeus — Girard.  (^Flexor  metacarpi  medius—PercivaU. 
Humero-met.acarpeus  internus — Leyh.) 

Situation — Form — Structure. — This  muscle,  situated  behind  and  within 
the  fore-arm,  is  an  exact  counterpart  of  the  preceding  in  form  and  structure. 

Direction. — Bourgelat  has  improperly  named  it  an  oblique  flexor,  for  its 
direction  is  vertical  like  that  of  the  other  muscles  of  this  region. 

Attachments. — It  has  its  origin  :  1,  On  the  base  of  the  epitrochlea  by  the 
tendinous  fibres  of  its  superior  extremity ;  2,  On  the  olecranon,  by  a  small, 
very  thin,  and  very  pale  fleshy  band,  which  is  annexed  to  the  princijial 
muscular  body,  and  soon  unites  with  its  posterior  border.  Its  inferior  tendon 
is  undivided,  and  terminates  on  the  supercarpal  bone,  along  with  the  ex- 
ternal flexor,  to  which  it  is  intimately  attached. 

Belations. — By  its  superficial  face,  with  the  antibrachial  aponeurosis, 
which  strongly  adheres  to  its  tendon ;  by  its  deep  face,  with  the  flexors  of 
the  phalanges.  Its  anterior  border  is  covered  by  the  internal  flexor ;  the 
posterior  responds  to  the  external  flexor. 

Action. — It  is  a  congener  of  the  preceding. 

3.  Internal  Flexor  of  the  Metacarpus,  or  Palmaris  Magnus.     (Fig.  121,  19.) 

Synonyms.— 'Epitrochlea.  metacarpeus— G/mrd.  (Flexor  metacarpi  internus — Perci- 
vail.     Humero-metacarpeus  internus — Leyh.) 

Situation — Form—  Structure — Attachment.^ — This  muscle  is  situated 
within  the  fore-arm,  against  the  posterior  face  of  the  radius,  and  in  its 
general  features  resembles  its  congeners,  the  two  preceding  muscles.  It  is, 
however,  not  so  wide,  is  thinner,  and  less  aponeurotic.  Its  upper  extremity 
is  fixed,  by  tendinous  fibres,  to  the  base  of  the  epitrochlea  at  the  same  point 
as  the  oblique  flexor,  with  which  it  is  confounded — origin.  Its  inferior 
extremity  terminates  in  a  long,  thin,  funicular  tendon  which  passes  through 
a  fibrous  sheath  at  the  inner  side  of  the  knee,  and  is  inserted  into  the  head 
of  the  internal  metacarpal  bone — movable  insertion. 

Belations. — It  is  covered  by  the  antibrachial  aponeurosis,  and  covers  the 
oblique  flexor,  the  pei-foratus  and  perforans,  as  well  as  important  blood- 


MUSCLES  OF  THE  ASTERIOR  LIMBS.  267 

vessels  and  nerves.  Its  anterior  border  responds  to  the  radius.  A  synovial 
sheath  envelops  its  terminal  tendon,  and  facilitates  its  movenaents  in  the 
fibrous  canal  through  which  it  passes. 

Action. — It  is  a  congener  of  the  preceding. 

4.  Superficial  Flexor,  Suhlimis  of  the  Phalanges,  or  Perforatus.    (Figs. 
89,  119,  121,  122.) 

Synonyms. — Epitroclilo-plialanseus— G/rard.      i^Flexor   pedis  perforatus — PercivaU 
Humeru-coronaris  or  humero-phalangeus — Leyh.) 

Situation. — The  superficial  flexor  of  the  phalanges  is  situated,  with  its 
fellow,  the  perforans,  beneath  the  flexors  of  the  metacarpus,  which  form  around 
them  a  kind  of  muscular  envelope. 

Form — Structure — Extent. — It  is  composed  of  a  muscular  and  tendinous 
portion.  The  first,  long,  thin,  prismatic,  and  divided  by  a  great  number  of 
aponeurotic  intersections,  extends  from  the  inferior  extremity  of  the  arm 
nearly  to  the  carpus.  The  tendon,  continuous  with  the  inferior  extremity  of 
the  muscular  portion,  receives  at  its  origin  an  enormous  fibrous  production 
that  arises  from  the  eminence  of  insertion  situated  at  the  posterior  face  of 
the  end  of  the  radius,  and  which  contracts  somewhat  intimate  adhesions 
with  the  antibrachial  aponeurosis,  as  well  as  with  the  perforans. 

After  being  thus  reinforced,  this  tendon  passes  through  the  carpal  sheath 
and  arrives  behind  the  fetlock,  where  it  forms  a  ring  (Fig.  89,  14)  for  the 
jiassage  of  the  tendon  of  the  deep  flexor.  To  this  peculiarity  is  o\\'ing  the 
designations  of  perforatus  and  perforans,  given  to  the  two  flexors  of  the 
phalanges.  Afterwards  it  is  inflected  forwards  over  the  sesamoid  groove, 
and  terminates  by  two  branches  towards  the  middle  of  the  digital  region. 

Attachments. — It  takes  its  origin,  in  common  with  the  perfiirans,  at  the 
summit  of  the  epitrochlea,  and  is  inserted,  by  the  bifurcations  of  its  tendon, 
into  the  extremities  of  the  pulley  formed  behind  the  superior  extremity  of  the 
second  phalanx. 

Relations. — The  muscular  portion,  covered  by  the  external  and  the 
oblique  flexors  of  the  metacarpus,  may  be  said  to  be  incrusted  in  the  perforans, 
to  which  it  adheres  in  the  most  intimate  manner.  The  tendon  covers  that 
of  the  latter  muscle,  and  is  in  turn  covered  by  the  fibrous  expansions  of  the 
two  metacarpal  and  metacarpo-phalangeal  sheaths  which  are  now  to  be 
described. 

The  Carpal  sheath  is  the  name  given  to  a  very  remarkable  annular 
apparatus,  formed  by  the  superficial  face  of  the  common  posterior  ligament  of 
the  carpus,  and  by  a  thick  expansion  of  inelastic  white  fibrous  tissue,  together 
constituting  a  perfect  arch  thrown  across  like  a  bridge,  from  the  supercarpal 
bone  to  the  inner  side  of  the  carpus.  This  arch  is  continuous,  above,  with 
the  antibrachial  aponeurosis,  and  is  prolonged,  below,  over  the  metacarpal 
portion  of  the  flexor  tendons.  An  extensive  synovial  membrane  covers  the 
internal  aspect  of  the  carpal  sheath,  envelops  the  perforatus  and  perforans 
in  their  passage  through  this  canal,  ascends  above  the  carpus,  and  descends 
as  for  as  the  lower  third  of  the  metacarpal  region. 

The  Metacarpo-phalangeal  sheath  is  formed  by  the  sesamoid  groove,  the 
posterior  face  of  the  principal  navicular  ligaments,  that  of  the  glenoid  fibro- 
cartilage  of  the  finst  interphalangeal  articulation,  and  by  the  posterior  pulley 
of  the  second  phalanx.  It  is  completed  by  a  very  wide  membranous  expansion 
applied  against  the  flexor  tendons,  closely  adherent  to  the  perforatus  on  the 
median  line  of  the  digit,  and  fixed,  laterally,  to  the  phalangeal  bones  by  the 


268  THE  MUSCLES. 

aid  of  three  special  fibrous  bands.  A  very  extensive  vaginal  synovial  mem- 
brane covers  the  internal  walls  of  this  jiassage,  and  is  reflected  on  the  flexor 
tendons ;  it  ascends  along  these  tendons  to  the  inferior  extremities  of  the 
lateral  metacarpals,  and  forms,  inferiorly,  a  somewhat  large  cul-de  sac  which, 
behind  the  second  phalanx,  lies  against  the  j)osterior  cul-de-sac  of  the 
articular  synovial  membrane  of  the  foot,  and  also  against  the  superior  cul-de- 
sac  of  the  navicular  sheath.  The  metacarpo-phalangeal  sheath  is  also  named 
the  great  sesamoid  sheath ;  but  this  designation  is  more  frequently  applied 
to  the  synovial  membrane  lining  its  walls. 

Action. — This  muscle  flexes  the  second  phalanx  on  the  first,  that  on  the 
metacarpus,  and  the  entire  foot  on  the  fore-arm.  Its  tendon,  through  the 
influence  of  the  fibrous  band  which  attaches  it  to  the  posterior  face  of  the 
radius,  acts  mechanically  as  a  stay  while  the  animal  is  standing,  by  maintain- 
ing the  metacarpo-phalangeal  angle. 

5.  Beep  Flexor  of  the  Phalanges  or  Perforans.    (Figs.  119,  121,  122.) 

Synonyms. — Ciibito-phalangeus,  or  radio-phalangeus — Girard.  (Flexor  pedis  perforans 
— Percivall.   Humero-radio-phalangeus — Leyh.) 

Situation — Composition — Extent. — This  muscle  is  situated  immediately 
behind  the  radius,  and  is  composed  of  three  portions  which  unite  at  the 
carpus,  to  be  continued  to  the  inferior  extremity  of  the  digit  by  a  long 
powerful  tendon. 

Form,  Structure,  and  Attachments  of  the  muscular  portion  of  the  perforans. — 
The  three  muscular  portions  may  be  distinguished,  in  regard  to  their  origin, 
into  epitrochlean,  idnar,  and  radial. 

The  epitrochlean  portion  is  the  most  considerable,  and  lies  beside  the 
perforatus  ;  being  three  or  four  times  the  volume  of  that  muscle,  it  is  easily 
divided  into  several  very  tendinous  fasciculi,  which  leave  the  summit  of  the 
epitrochlea  along  with  the  superficial  flexor.  The  tdnar  portion,  situated 
between  the  external  flexor  and  the  oblique  flexor  of  the  metacarj^us,  is  very 
short  and  conoid,  thick  at  its  superior  extremity,  contracted  at  its  inferior, 
to  which  succeeds  a  long  flat  tendon,  united  below  to  the  principal  tendon; 
it  has  its  origin  on  the  summit  and  the  posterior  border  of  the  olecranon. 
The  radial  portion,  representing  the  flexor  longus  pollicis  of  Man,  is  the 
smallest,  and  is  deeply  concealed  beneath  the  epitrochlean  muscular  jiortion. 
The  fibres  composing  it  are  fixed  to  the  posterior  surface  of  the  radius, 
where  they  are  slightly  divergent,  and  collect  upon  a  small  particular  tendon, 
which  is  confounded  with  the  common  tendon  after  contracting  adhesions 
with  the  radial  band  of  the  perforatus. 

Course  and  Attachments  of  the  tendon. — The  tendon  which  succeeds  these 
three  portions  enters  the  carjjal  sheath  with  that  of  the  superficial  flexor. 
Towards  the  middle  of  the  metacarpal  region,  it  receives  a  strong  fibrous 
band  from  the  great  posterior  ligament  of  the  carpus  (Figs.  119,  23  ;  122, 18), 
traverses  the  sesamoid  annular  apparatus  of  the  perforatus  tendon,  j^asses 
between  the  two  terminal  branches  of  that  tendon,  over  the  pulley  on  the 
posterior  face  of  the  second  phalanx,  and  afterwards  widens  to  form  a  large 
expansion  designated  the  plantar  aponeurosis. 

This  aponeurosis  glides,  by  its  anterior  face,  over  the  inferior  sui-face  of 
the  navicular  bone,  by  means  of  a  j)articular  synovial  membrane,  the 
small  navicular  sheath,  and  is  covered,  posteriorly,  by  a  fibrous  layer,  noticed 
for  the  first  time  by  M  H.  Boulcy,  who  considers  it  as  a  reinforcing 
sheath  for  the  perforans  tendon.     It  is  finally  inserted  into  the  semilunar 


MUSCLES  OF  THE  ANTERIOR  LIMBS.  269 

crest  of  the  os  pedis,  and  the  median  imprints  situated  behind  this  crest, 
in  becoming  confounded  at  its  sides  with  the  tissue  of  the  lateral  fibro- 
cartilages. 

The  jiavicular  sheath  is  vesicular  in  form ;  it  covers  the  navicular  bone 
and  the  single  ligament  of  the  pedal  articulation,  becomes  reflected  on  the 
plantar  aponeurosis  in  front  of  this  ligament,  and  ascends  to  the  inferior 
cul-de-sac  of  the  sesamoid  sheath,  where  it  is  again  reflected  and  continued 
bv  itself.  It  therefore  forms  two  culs-de-sac,  one  superior,  the  other  inferior, 
which  are  readily  perceived  in  a  longitudinal  and  vertical  section  of  the 
digital  region.  The  first  is  in  contact  with  the  posterior  cid-de-sac  of  the 
synovial  membrane  of  the  pedal  articulation,  and  is  separated  from  the 
inferior  sac  of  the  sesamoid  sheath  by  a  transverse  layer  of  yellow  fibrous 
tissue  which  attaches  the  perforans  tendon  to  the  posterior  face  of  the  second 
phalanx.  The  second  is  situated  beneath  the  interosseous  ligament  which 
unites  the  navicular  bone  to  the  third  phalanx. 

The  reinforcing  sheath  of  the  perforans  tendon  is  formed  by  a  fibrous 
membrane  applied  against  the  posterior  face  of  the  plantar  aponeurosis. 
This  membrane  adheres  intimately  below,  to  the  expansion  it  covers,  and 
ends  in  becoming  entirely  confounded  with  it.  It  is  fixed,  at  its  borders,  to 
the  inferior  extremity  of  the  first  phalanx,  by  means  of  two  lateral  bands. 

Eelations. — The  epitrochleau  muscular  portion  is  covered,  at  its  origin, 
by  the  external  cul-de-sac  of  the  elbow  joint,  wliich  sac  also  covers  the  other 
muscles  attached  to  the  epitrochlea— the  external  and  oblique  flexors  of  the 
metacarpus.  It  responds,  anteriorly,  witb  the  radius  and  radial  portion  of 
the  muscle ;  posteriorly,  with  the  perforatus ;  externally,  with  the  external 
flexor  of  the  metacarpus;  inwardly,  with  the  internal  and  oblique  flexors 
of  the  same  ray. 

The  ulnar  portion,  covered  by  the  antibrachial  aponeurosis,  covers  the 
epitrochlean  portion. 

The  radial  division  is  comprised  between  the  latter  and  the  posterior  face 
of  the  radius. 

The  tendon  is  in  contact,  posteriorly,  with  that  of  the  perforatus ; 
anteriorly,  with  the  posterior  ligament  of  the  carpus,  the  suspensory  ligament 
of  the  fetlock,  and  the  sesamoid  groove  ;  by  its  sides,  with  the  vessels  and 
nerves  of  the  digit.  Its  tei-minal  expansion  is  covered  by  the  plantar  cushion, 
which  adheres  to  it,  in  front,  in  the  most  intimate  manner ;  it  covers  the 
navicular  bone. 

Action. — This  muscle  flexes  the  phalanges  on  one  another  and  on  the 
metacarpus.  It  also  concurs  in  the  flexion  of  the  entire  foot  on  the  fore-arm. 
The  band  which  attaches  its  tendon  behind  the  carpus,  as  well  as  its  phalan- 
geal reinforcing  sheath,  gives  it  the  mechanical  power  necessary  to  supjjort 
•  the  angle  of  the  metacarpo-phalangeal  articulation  and  the  digital  region, 
while  the  animal  is  in  a  standing  posture. 

(In  the  "Deep  Flexor,"  of  5l.  Chauveau's  description,  we  find  included 
two  portions  which  are  separately  named  and  described  by  Mr.  Percivall 
and  Professor  Gurlt.  These  are  the  ulnaris  accessorius  and  radialis  accessorius 
of  the  former,  and  the  cuhito-ulnar  and  radial  branches  of  the  latter.  These, 
in  reality,  are  portions  of  the  perforans.  and  have  been  so  designated  in  this 
treatise.  Though  arising  independently,  they  terminate  in  the  perforans 
tendon  before  it  leaves  the  carpal  sheath,  and  join  with  it  in  flexing  the 
metacarpus  and  phalanges.) 


270 


THE  MUSCLES. 


Fig.  12.",.  DIFFEKENTIAL    CHARACTERS  OF  THE   MISCLES   OF  THE   FORE- 

ARM  IN   OTHER   THAN   SOUPED   ANIMALS, 

KiMiNANTS. — Tn  the  Ox  and  Sheep,  the  anterior  ex- 
tensor of  the  metucarptis  comports  itself  as  in  Solipeiis. 

The  oblique  extensor  of  the  metacarpus  of  the  same 
region  terminates  inside  tlie  upper  extremity  of  the  prin- 
cipal metacarpus. 

The  anterior  extensor  of  the  phalanges  ofters  a  remark- 
able disposition.  This  muscle  is  divided  throughout  its 
length  into  two  parallel  portions :  an  external,  which  forms 
the  common  extensor  of  the  digits;  and  an  internal,  the 
propter  extensor  of  the  internal  digit. 

a.  The  fleshy  body  of  the  common  extensor  (fig.  123,  3) 
is  a  little  more  voluminous  than  that  of  the  second  muscle. 
Its  tendon  (3')  commences  near  the  inferior  third  of  the 
radius,  passes  over  the  knee,  the  metacarpal  bone,  and  the 
metacarpo-phalangcal  articulation.  On  arriving  at  the 
origin  of  the  digits  it  bifurcates,  and  each  of  its  branches 
goes  to  be  inserted  into  the  pyramidal  eminence  of  the 
tiiird  phalanx  (3").  This  muscle,  in  extending  the  digits, 
brings  them  together,  as  M.  Lecoq  has  judiciously  re- 
marked. 

b.  The  proper  extensor  of  the  internal  digit  (fig.  123,  4) 
much  resembles  the  common  extensor  in  volume,  form,- 
and  direction.  Its  tendon  (4')  passes,  with  that  termi- 
nating the  latter  muscle,  into  one  of  the  inferior  grooves 
of  the  radius  and  over  the  ca[)sular  ligament  of  the  carpus, 
where  the  two  cords  are  enveloped  by  a  common  synovial 
sheath.'  Arrived  at  the  metacarpo-phalangeal  articulation, 
this  tendon  is  placed  at  the  excentric  side  of  the  internal 
digit,  and  descends,  gradually  expanding,  until  it  reaches 
the  inferior  extremity  of  this  bone  ;  towards  the  middle  of 
the  first  phalanx,  it  receives  from  the  suspensory  ligament 
of  the  fetlock  two  constraining  bands  similar  to  those 
■which,  in  Solipeds.  bind  the  anterior  extensor  of  the  pha- 
langes on  the  same  bone.  '  This  tendon  bifurcates  infe- 
riorly  ;  one  of  its  branches  is  attached  to  the  anterior  face 
of  the  second  phalanx ;  the  other,  much  wider  than  the 

THE   FORE-ARM  first,  covers  the  common  external   lateral  ligament  of  the 

OF  THE  ox ;  EXTERNAL  FACE,  two  inter-phalangeal  articulations,  and  terminates  on  the 

1,   Anterior   extensor   of  the  whole  external  side  of  the  third  plialanx.     In  the  Sheep, 

metacarpus;  1',  In.sertion  of  this  second  branch  is  feeble,  and  is  directed  towards  the 

its  tendon  ;   2,  Oblique  ex-  heel,  which  it  envelopes  by  uniting  its  fibres  witli  the  per- 

tensor;  3,  Common  extensor  forans  tendon  and  the  plantar  cushion, 
of  the  digits;  3',  Its  tendon;  The  lateral  extensor  of  the  phalanges  of  Ruminants  is 

3",  Terminal  bifurcation  of  thicker  than  in  the  Horse,  and  constitutes  the  proper  ex- 

that  tendon;  4,  Proper  ex-  tensor  of  the    external  digit   (fig.    123,   5).     Its   terminal 

tensor  of  the  internal  digit ;  tendon  (4',  6,  7)  comports  itself  exactly  the  same  as  that 

4',  Its  tendon ;    5,   Proper  of  the   proper  extensor  of  the  internal  digit,  and  conse- 

extensor    of    the    external  quently  does  not   merit  a   special  descripticni.     We  may  , 

digit ;  5',  Its  tendon ;  6,  Its  remark,  with  M.  Lecoq,  that  thei^e  two  muscles  separate 

branch  of  insertion  into  the  tlie  digits  from  each  other  in  extending  them ;  they  are, 

second  phalanx ;  7,  Branch  therefore,  to  a  certain  point,  antagonists  of  the  common 

to   the    third    phalanx ;    8,  extensor. 

External  flexor  of  the  meta-  The  perforatus  of  the  Ox  and  Sheep  is  composed  of 

carpus ;  9,  Olecranian  por-  two  portions,  whose  tendons  unite  towards  the  middle  of 

tion  of  the  perforans ;   10,  the  metacarpal  region.     The  single  tendon  (fig.  124,  1,  2,  3) 

Tendon   of    the   perforans ;  which  results  from  this  union  afterwards  divides  into  two 

11,  Tendon   of  the   perfo-  branches,  each  of  which  comports  itself,  in  regard  to  tho 

ratus  ;  12,  Suspensory  liga- 

ment    of   the    fetlock ;    13, 

The  band  it  furnishes  to  the  perforatus  to  form  the  ring  through  which  the  perforans         « 
passes ;  14,  The  external  band  it  gives  off  to  the  proper  extensor  of  the  external  digit; 
15,  Coraco-radialis ;  16,  Anterior  brachial;  17,  Anconeus. 


MUSCLES  OF  THE  ANTERIOR  LIMBS. 


271 


digits,  as  the  sinixle  perforatus  tendon  does  in  the  Horse,  except  that  they  receive  from 
the  suspensory  liijament  a  tibrous  band  analogous  to  that  wliich,  in  Solipeds,  goes  to 
the  pcrtbrans  tendon.  Tliis  baud  (tig.  123,  13)  concurs  in  the  Ibrmation  of  the  annular 
ligament  tlirough  wliich  the  latter  tendon  passes. 

In  the  Ox,  the  terminal  tendon  of  the  perforans  does  not  receive  any  carpal  band  ; 
this  goes  to  the  perforatus.  Above  the  fetlock,  it  divides  into  two  branches,  one  for  each 
digit,  which,  after  traversing  tlio  perforatus,  terminates  behind  the  inferior  face  of 
the  third  phalanx.  There  it  is  blended  with  the  plantar  cushion, 
the  inferior  interdigital  ligament,  and  a  fibrous  fascia  already 
noticed  in  the  description  of  that  ligament.  This  la3'er  arises 
from  the  aponeurosis  covering  the  Hexor  tendons  in  the  meta- 
carpal region ;  it  descends  on  the  heels,  behind  and  outside  the 
digits,  remains  united  to  tiiat  of  the  other  digit  by  an  inter- 
mediate fibrous  fascia,  and  is  attaclied  to  the  enveloping  sheaths 
of  the  flexor  tendons,  as  well  as  to  the  superior  interdigital  liga- 
ment. Eacii  terminates  inferiorly,  in  becoming  united  to  the 
proper  extensor  of  the  digit,  the  plantar  cusliion,  the  inferior 
digital  ligament,  and  the  deep  flexor  of  the  phalanges. 

There  is  not,  properly  speaking,  a  phalangeal  reinforcing 
sheath ;  though  we  may  consider  as  such  the  superior  fasciculi 
of  tlie  inferior  interdigital  ligament  (fig.  124.  6). 

Pig. — In  this  animal,  the  anterior  extensor  tendon  of  the 
phalanges  passes  to  the  superior  extremity  of  the  inner  large 
metacarpal  bone,  and  that  of  the  oblique  extensor  to  the  small 
internal  metacarpal. 

Instead  of  the  anterior  extensor  of  the  phalanges,  two  muscles 
are  found  analogous  to  those  described  as  existing  in  Ruminants. 
The  external,  or  common  extensor  of  the  digits,  is  easily  divided 
into  several  fasciculi,  and  is  terminated  by  four  tendinous  branches 
which  reach  the  -pyramidal  eminence  of  the  third  phalanx  of  the 
four  digits.  The  tendon  of  the  small  external  digit  often  gives 
otf  a  thin  bifid  ramification,  destined  to  supplement  the  tendons  of 
the  two  large  digits.  The  internal  muscle,  or  proper  extensor  of 
the  two  internal  digits,  possesses  a  bifurcated  tendon  ;  each  branch  texdixous  and  liga- 
goes  to  the  excentric  side  of  the  third  phalanx  of  the  digit  it  is  mextous  apparA' 
charged  to  move. 

With  regard  to  the  muscles  of  the  posterior  antibrachial 
region,  it  is  remarked :  1,  That  the  anterior  branch  of  the  ter- 
minal tendon  of  the  external  fiexor  of  the  metacarpus  passes  to 
the  head  of  the  outer  metacarpal  bone  ;  2,  That  the  internal  flexor 
terminates  on  the  metacarpal  of  tije  great  external  digit ;  3, 
That  the  perforatus  is  formed  by  two  muscular  bodies,  each 
terminated  by  a  tendon  inserted,  inferiorly,  into  the  second  pha- 
lanx of  one  of  the  great  digits.  4,  That  the  perforans  is  divided 
into  four  terminal  branches  which  arrive  at  the  large  phalanx  of 
the  digits. 

Carxivora. — In  the  Dog  and  Cat,  the  anterior  extensor  of  the 
metacarpus  divides,  at  its' lower  extremity,  into  two  branches, 
which  resemble  those  of  the  two  external  mdial  muscles  of  Man : 
one  is  inserted  into  the  metacarpus  of  the  index,  the  other  into 
the  metacarpus  of  the  medius  (fig.  125,  A,  5,  6,  7). 

The  oblique  extensor  passes  to  the  metacarpus  of  the  thumb; 
it  furnishes,  besides,  a  small  particular  branch  that  glides,  by 
means  of  a  sesamoid,  over  the  third  bone  of  the  inferior  row  of 
the  carpus,  and  is  blended  with  the  posterior  ligament  of  the 
carpus  (fig.  125,  a,  8;  b,  4;  d.  8)  ;  it  separates  the  thumb  from  the  other  digits,  but  we 
think  it  scarcely  adapted  for  the  function  of  extensor. 

The  anterior  extensor  of  the  phalanges  of  solipeds  is  replaced  by  a  single  muscle,  the 
common  extensor  of  the  digits,  terminated  by  a  quadrifurcated  tendon,  whose  branches 
are  distributed  to  the  four  great  digits  ,fig.  125,  a,  9,  9'). 

The  tendon  of  the  lateral  extensor  is  divided  into  three  branches,  which  are  inserted 
on  tlie  anterior  face  of  the  three  outer  digits,  and  are  blended  with  the  tendons  of  the 
common  extensor,  or  with  the  fibrous  bands  furnished  to  these  tendons  by  the  inter- 
osseous metacarpal  muscles. 

The  external  flexor  of  the  metacarpus  comports  itself  as  in  the  Pig.    But  the  oblique 


TUS  OF  THE  POSTE- 
RIOR FACE  OF  THE 
DIGITAL  REGION  IX 
THE  OX  ;  POSTERIOR 
LIMB. 

1,  Perforatus  tendon ; 
2,  2,  Its  terminal 
branches;  3, 3,  Tiieir 
bifurcation ;  4,  4, 
Perforans  ;  6,  6,  Su- 
perior bands  of  the 
inferior  digital  liga- 
ment attached  to  the 
first  phalanx  ;  7,  In- 
ferior interdigital 
hgament ;  8,  8,  Sus- 
pensory ligament  of 
the  fetlock. 


272  THE  MUSCLES. 

flexor  is  covered  by  the  perforatus,  and  its  olecranian  portion,  thicker  than  in  the  other 
animals,  is  only  united  to  the  principal  fleshy  body  altogether  inferioily.  Tlie  internal 
flexor  is  feeble  and  conoid ;  its  tendon,  thin  and  long,  reaches  the  metacarpus  of  the 
index. 

The  perforatus  of  the  Dog  and  Cat  offers  a  long,  wide,  and  superficial  body, 
separated  from  the  perforans  by  the  oblique  flexor  of  the  metacarpus.  Its  tendon 
passes  outside  the  carpal  slieath.  and  is  divided  into  four  branches,  attached  by  their 
inferior  extremity  to  the  second  phalanx  of  the  four  principal  digits. 

For  the  perforans,  it  is  noted  : 

1.  That  the  radial  portion  of  the  muscle  (the  long  flexor  of  the  thumb  in  Man)  com- 
mences towards  the  superior  extremity  of  the  radius  (fig.  125,  c,  4). 

2.  That  the  ulnar  division  is  a  semi-penniform  muscle,  attached  by  the  superior 
extremities  of  its  fibres  to  nearly  the  whole  extent  of  the  posterior  face  of  tlie  ulnar  (fig. 
125,  c,  3). 

3.  That  the  epitrochlean  portion  sends  off,  above  the  knee,  a  small  particular 
fasciculus  terminating  in  a  very  thin  tendon,  which  becomes  lost  in  Ihe  fibrous  arch  of 
the  carpal  sheath  (fig.  125,  c,  6).  This  small  muscle  represents  the  pal  maris  brevis  of 
Man. 

The  terminal  tendon  divides  into  five  branches,  one  for  each  digit  (fig.  125,  d,  4,  &c.). 
There  have  been  already  described  in  these  animals : 

1.  Two  external  radial  muscles,  only  distinct  at  their  terminal  extremity,  and  con- 
founded for  the  remainder  of  their  extent.  This  is  the  anterior  extensor  of  the  meta- 
carpus in  Solipeds  ffig.  125,  a,  5,  G,  7). 

2.  A  long  abductor  of  the  thumb,  which  appears  to  be  the  representative  of  the 
analogous  muscle,  and  the  short  extensor  of  the  same  digit  in  Man.  It  is  the  oblique 
extensor  of  the  metacarpus  in  the  Horse  (fig.  125,  a,  8). 

3.  A  common  extensor  of  the  digits;  the  anterior  extensor  of  the  phalanges  in  the 
Horse  (fig.  125,  a,  10). 

4.  A  proper  extensor  of  the  three  external  digits,  the  proper  extensor  of  the  little 
finger  in  Man,  or  lateral  extensor  of  the  phalanges  in  tlie  Horse  (fig.  125,  a,  10). 

5.  A  posterior  ulnar,  or  external  flexor  of  the  metacarpus  in  the  Horse  (fig.  125, 
A,  14). 

6.  An  anterior  ulnar,  or  oblique  flexor  of  the  metacarpus  in  the  Horse  (fig.  125, 
D,  6). 

7.  A  great  palmar,  corresponding  to  the  internal  flexor  of  the  metacarpus  in  the 
Horse  (fig.  125,  b,  8). 

8.  A  small  palmar,  a  dependency  of  the  deep  flexor  of  the  phalanges  (fig.  125,  c,  6). 

9.  A  flexor  s'lblimis  of  the  phalanges  (fig.  125,  D,  1). 

10.  A  deep  flexor  of  the  phalanges  (fig.  125,  c,  5,  D,  3). 

11.  A  long  flexor  of  the  thumb,  united  to  tiie  preceding  muscle,  the  radial  portion  of 
the  perforans  (fii,'.  125.  c,  4). 

But  in  Carnirora  there  are  five  additional  muscles,  which  are  not  generally  found  in 
the  other  animals.  These  are :  the  proper  extensor  of  the  thumb  and  index,  long 
supinator,  short  supinator,  round  pronator,  and  the  square  pronator.  A  special  descrip- 
tion will  be  given  of  these. 

MUSCLES  PROPER  TO  THE  FORE-ARM  OF  CARNIVORA. 

1.  Proper  Extensor  of  the  Thumb  and  Index.    (Fig.  125,  a,  11 ;  b,  3.) 

Synonyms. — The  e.xtensor  secundi  internodii  pollicis  and  extensor  indicis  of  Man. 

Ttus  is  a  very  small  muscle,  composed  of  a  fleshy  borly  and  a  tendon.  The  first  is 
thin  and  fusiform,  and  is  situated  under  the  lateral  extensor;  it  has  its  origin  with  the 
oblique  extensor  of  the  metacarpus  at  tlie  external  side  of  the  radius.  The  tendon 
crosses  the  anterior  aspect  of  the  knee,  enveloped  by  the  synovial  slieath  of  the  common 
extensor  of  the  digits,  under  which  it  passes.  It  divides  into  two  branches,  one  of 
which  goes  to  the  thumb,  the  other  to  the  index.' 

2.  Long  Supinator.     (Fig.  125,  A,  12;  c,  8.) 

This  muscle  only  exi-sts  in  the  rudimentary  state  in  Carnivora.  Its  existence  in  the 
Dog  has  even  been  denied,  but  this  is  an  error ;  our  researches  have  demonstrated  that 
it  is  present,  in  a  more  or  less  evident  manner,  in  all  breeds. 


*  In  very  powerful  Horses,  and  more  frequently  in  the  Ox,  we  have  met  with  traces 
of  this  muscle  in  the  form  of  a  deep  fasciculus  situated  in  front  of  the  lateral  extensor. 


MUSCLES  OF  THE  ANTERIOR  LIMBS. 

Fig.  125. 
B.  C. 


D. 


273 


MUSCLES   OF   THE   FORE-ARM   AXD   PAW   OF   THE   DOG. 

A.  Aiiterior  superficial  region. — 1,  Short  flexor  of  tlie  fore-arm  (anterior  brachial); 
2,  Long  flexor  of  the  fore-arm  (brachial  biceps)  ;  3,  Anconeus  ;  4,  Round  pronator ; 
5,  Anterior  extensor  of  the  metacarpus  (external  radial);  6,  Its  tendon  of  inser- 
tion, destined  for  the  fourth  metacarpal  bone ;  7,  That  which  goes  to  the  third  ; 
8,  External  oblique  of  the  metacarpus  (long  abductor  and  short  extensor  of  the 
thumb) ;  9,  Common  extensor  of  the  digits ;  9',  Its  terminal  tendon  at  the  point" 
where  it  divides  into  four  branches ;  10,  Proper  extensor  of  the  three  external 
digits,  or  lateral  extensor  of  the  phalanges  in  the  Horse  ;  10',  Its  terminal  tendon 
at  the  commencement  of  its  trifurcation;  11,  Proper  extensor  of  the  thumb  and 
index;  11',  Its  terminal  tendon;  12,  12,  Long  supinator;  13,  External  flexor  of 
the  metacarpus  (posterior  ulnar). 

B.  Veep  anterior  region.— \,  Pvound  pronator ;  2,  Short  supinator ;  3,  Proper  extensor 
of  the  thumb  and  index ;  4,  Oblique  extensor  of  the  metacarpus ;  3,  Superior 
insertion  of  the  anterior  extensor  of  the  metacarpus ;  6,  Ditto  of  the  anterior 
extensor  of  the  phalanges;  7,  Proper  extensor  of  the  three  external  digits;  8, 
Internal  flexor  of  the  metacarpus  (great  palmar);  9,  Levator  humeri ;  10,  11, 
Long  and  short  flexors  of  the  fore-arm. 

C.  Deep  posterior  region. — 1,  Round  pronator;  2,  Square  pronator;  3,  Ulnar  portion 
of  the  perforans;  4,  Radial  portion  of  the  same  (long  flexor  of  the  thumb);  5, 
Terminal  tendon  of  the  same ;  6,  Tendon  of  the  small  palmar  (division  of  the 
perforans);  7,  Anterior  extensor  of  the  metacarpus;  8,  Long  su]iinator ;  9, 
Epicondyloid  insertion  of  the  perforatus,  perforans,  and  oblique  and  internal 
flexors  of  the  metacarpus;  10,  Oleeranian  in^^ertion  of  the  oblique  flexor;  11, 
Supercarpal  insertion  of  the  same;  12,  Terminal  tendon  of  the  internal  flexor; 
13,  Proper  extensor  of  the  external  digits;  14,  Coraco-radialis  ;  15,  Tendon  of 
the  extensors  of  the  fore-arm. 

D.  Superficial  posterior  region,  and  the  special  muscles  of  the  foot  or  hand. — 1,  Perfo- 


27 1  TEE  MUSCLES. 

It  is  a  very  delicate  band,  situated  in  front,  and  on  the  inner  side  of  the  anterior 
extensor  of  the  metacarpus,  taking  its  origin,  alung  with  tliat  muscle,  from  the  crest 
limiting  the  furrow  of  torsion  of  the  humerus,  behind  tbe  ridge;  and  terminating 
within  the  inferior  extremity  of  the  radius  by  flesliy  and  aponeurotic  fibres.  This  small 
muscle  can  have  but  a  very  limited  influence  on  the  movements  of  the  bones  of  the 
fore-arm,  because  of  its  trifling  volume.     As  its  name  indicates,  it  acts  in  supiiiatiou. 

3.  Short  Sxipinator  (Fig.  125,  B,  2.) 

A  triangular  and  slightly  divergent  muscle,  covered  by  the  anterior  extensor  of  the 
mctucarpus  and  the  comuiou  extensor  of  the  digits.  It  has  its  origin  in  the  small  fossa 
situated  outside  the  humeral  trocldea.  by  a  flat  tendon  which  is  c mfounded  with  the 
external  lateral  ligament  of  the  ell)ow  joint.  It  terminates  above  the  anterior  face  and 
the  inner  side  of  the  radius,  by  the  inferior  extremities  of  its  fleshy  fibres.  Covered  by 
the  two  preceding  muscles,  it  covers  the  elbow  articulation  and  the  bone  receiving  its 
insertion.  It  ought  to  be  cousideied,  in  Carnivora,  as  the  principal  supinator;  it  pivots 
the  radius  ou  the  ulna,  so  as  to  turn  the  anterior  face  of  the  fii'st  bone  outwards. 

4.  Round  Pronator.    (Fig.  125,  b,  1 ;  c,  1.) 

Situated  on  the  inner  and  upper  part  of  the  fore  arm,  between  the  great  palmar  or 
internal  flexor  of  the  metacarpus  and  the  interior  extensor  of  the  same  ray,  the  roimd 
pronator  is  a  thick  and  thort;  muscle,  which  originates  on  the  small  epicondyloid 
tuberosity  of  the  humerus,  and  terminates  at  the  internal  side  of  the  radius  by  aponeu- 
rotic fibres. 

5,  Square  Pronator.     (Fig.  125,  c,  2.) 

This  muscle  is  situated  immediately  behind  the  bones  of  the  fore-arm,  beneath  the 
muscular  masses  of  the  posterior  antibrachial  region.  It  extends  from  the  insertion  of  the 
flexors  of  tlie  fore-arm  to  near  the  carpus,  and  is  formed  of  transverse  fibres  which  pass 
directly  from  the  lUua  to  the  radius.  It  is,  then,  no  longer,  as  in  ]\Ian,  a  square  muscle 
attached  only  to  the  lower  fourth  of  these  two  bones.  The  two  pronators  are  antasfonists 
of  the  short  supinator,  turning  forwards  the  anterior  face  of  the  radius  anil  metacarpus. 

COMPARISON   OF   THE   MUSCLES   OF  THE   FORE-ARM   OP   MAN   WITH   THOSE   OF   ANIMALS. 

All  the  muscles  of  the  fore-arm  of  Man  are  more  or  less  perfectly  represented  in  the 
fore-arm  of  Carnivora. 

In  Man,  these  muscles  are  described  in  placing  the  fore-arm  in  a  state  of  supination, 
and  are  divided  into  three  regions  :  anterior,  external,  and  posterior. 

A.  Anterior  Region. 

This  comprises  eight  muscles  • — 

1.  The  round  pronator,  absent  in  animals  except  the  Carnivora.  This  muscle  forms 
the  internal  oblique  prominence  in  the  bend  of  the  elbow.  It  leaves  the  epitrochlea  and 
the  coronoid  process  of  the  ulna,  terminating  on  the  midJle  third  of  the  external  face  of 
the  radius. 

2.  The  great  palmaris,  which  corresponds  to  the  internal  flexor  of  the  metacai-pus  of 
the  Horse.  Situated  within  the  preceding,  it  is  attached,  above,  to  the  epitrochlea ; 
below,  to  the  base  of  the  second  metacarpal.      It  is  more  especially  a  flexor  of  the 

hand,  ,     ,  .  ,    .  ,  . 

3.  The  small  palmaris,  whose  presence  is  not  constant,  and  which  is  represented  m 
the  Dog  by  a  portion  of  the  deep  flexor  of  the  phalanges. 


ratus  ;  1',  Its  tendon  divided  at  its  passage  behind  the  carpal  sheath  ;  2,  Do.,  Its 
terminal  branches;  3,  Perforans;  .3'.  Its  tendon  divided  after  its  exit  from  the 
carpal  sheath  ;  4,  Do.,  Its  terminal  branches  ;  5.  Tendon  of  the  internal  flexor  of  the 
metacarpus;  6,  Oblique  flexor  (anterior  ulnar);  7,  Inferior  extremity  of  the  long 
supinator;  8,  Terminal  tendon  of  the  oblique  extensor  of  the  metacarpus;  9, 
Short  abductor  of  the  thumb;  10.  Opponent  of  the  thumb;  11,  Short  flexor  of 
the  thumb;  12,  Adductor  of  the  thumb,  transformed,  in  the  Dog,  into  the  adduc- 
tor of  the  index  ;  13,  Short  flexor  of  the  small  digit ;  14,  Adductor  of  the  small 
digit;  15,  Opponent  of  the  small  digit ;  16, 16,  Metacarpal  interosseous  muscles; 
fl,  a,  a.  Bands  which  maintain  the  flexor  tendons  on  the  metacarpo-])halangean 
articulations,  and  limit  the  sejiaration  of  the  digits;  collectively,  tliey  represent, 
in  a  rudimentary  state,  the  palmar  aponeurosis  of  Man. 


MUSCLES  OF  THE  ANTERIOR  LIMBS. 


275 


4.  The  superficial  flexor  or  per/oratus  has  two  planes  of  muscular  fibres.  The  super- 
ficial plane  is  dt-stiued  to  the  tindons  of  the  mrdius  and  annularis  ;  the  duep plane  to  tiie 
tendons  of  the  index  and  little  finger.  These  tendons  are  fixed  into  tiie  secondary- 
phalanges  of  the  above-named  digits. 

5.  i'iie  anterior  ulnar  resembles  the  oblique  flexor  of  the  metacarpus  of  the  Horse. 
It  is  inserted,  above,  into  the  epitrochlea  and  the  olecranon  ;  bel  i\v,  in  the  pisiform  bone. 
Its  action  is  transmittid,  by  a  fibrous  band,  from  this  bone  to  the  fifth  metacarpal. 
It  flexes  the  hand  by  inclining  it  inwards. 


Fi?.  126. 


Fig.  127. 


SUPERFICIAL  MUSCLES  OF  HUSIAN  FORE-ARM. 

1,  Biceps,  with  its  tendon  ;  2,  Brachialis  an- 
ticus;  3,  Triceps;  4,  Pronator  radii  teres; 
5,  Flexor  carpi  radialis  ;  6,  Palmaris  lon- 
gus ;  7,  A  fiisciculus  of  flexor  sublimis 
digitorum ;  8,  Flexor  carpi  ulnaris ;  9, 
Palmar  fascia;  10,  Palmaris  brevis ;  11, 
Abductor  pollicis;  12,  Flexor  brevis  pol- 
licis ;  lo,  Supinator  longus ;  14,  Extensor 
ossis  metacarpi,  and  extensor  primi  inter- 
nodii  pollicis. 


DEEP  LAYER  OF  SUPERFICIAL  MUSCLES  OF 
HUMAN   FORE-ARM. 

1,  Internal  lateral  ligament  of  elbow  joint ; 
2,  Anterior  ligament;  3,  Orbicular  ligament 
of  radius  ;  4,  Flexor  profundus  digitorum  ; 
5,  Flexor  longus  pollicis;  6,  Pronator  quad- 
ratus ;  7,  Adductor  pollicis ;  8,  Dorsal  in- 
terosseous of  middle,  and  palmar  inter- 
osseous of  ring  finger;  9,  Dorsal  inter- 
osseous muscle  of  rmg-finger,  and  palmar 
interosseous  of  little  tincrer. 


6.  The  deep  flexor  or  perforamt  is  resolved  into  two  fasciculi :  one,  the  internal,  for 
the  little  finger.'the  annularis,  and  the  niedius  the  other,  the  external,  for  the  index. 
The  three  first  tendons  are  ;it  first  united  to  each  other  by  fibrous  bands,  and  together 
pass  through  a  sheath  formf  d  by  the  perforatus. 

7.  The  proper  flexor  of  the  thumb,  represt-nted  in  the  Dog  by  the  radial  portion  of  the 
perforans.     It  is  attached,  for  one  part,  to  the  upper  three-fourths  of  the  anterior  face  of 


276  THE  MUSCLES. 

the  radius,  the  interosseous  aponeurosis,  and  the  coronoiJ  process  of  the  ulna;  on  the 
other  part,  to  the  second  phalanx  of  the  thumb. 

8.  The  square  pronator,  a  thick,  qua<lri lateral  muscle  with  transverse  fibres,  situated 
at  the  deep  and  inferior  portion  of  the  fore-arm.  This  muscle  in  the  Dog  is  much  more 
extensive  in  length. 

B.  External  Region. 

The  muscles  of  this  region  are  four  in  number,  two  of  which,  the  supinators,  are  only 
represented  in  Carnivorous  animals : — 

1.  The  long  supinator  forms  a  prominent  mass  at  the  bend  of  the  elbow.  It  is 
attached  to  the  infeiior  third  of  the  external  border  of  tiie  humerus,  and  to  the  base  of 
the  styloid  process  of  the  radius.  It  is  a  flexor  of  the  fore-arm,  not  a  supinator,  as  its 
name  indicates. 

2.  The  first  external  radial  is  represented  by  a  portion  of  the  anterior  extensor  of  the 
metacarpus  of  animals.  It  commences  at  the  inferior  part  of  the  external  border  of  the 
humerus,  and  terminates  at  the  posterior  part  of  the  base  of  the  second  metacarpal. 

3.  The  second  external  radial,  also  represented  by  a  portion  of  the  anterior  extensor 
of  the  metacarpus,  terminates  at  the  base  of  the  third  metacarpal. 

4.  The  short  supinator,  a  muscle  bending  round  the  upper  third  of  the  radius,  is  the 
essential  agent  in  supination. 

c.  Posterior  Region. 

The  muscles  of  this  region,  divisible  into  two  layers,  are : — 

1.  Tiie  common  extensor  of  the  digits — anterior  extensor  of  the  phalanges  of  the  Horse 
— divided  into  four  tendinous  branches  which  pass  to  all  the  fingers,  except  the  thumb. 

2.  The  proper  extensor  of  the  little  finger,  whose  tendon  is  joined  to  the  branch  .of  the 
common  extensor  that  passes  to  the  auricularis — the  lateral  extensor  of  animals. 

3.  The  posterior  ulnar,  corresponding  to  the  external  flexor  of  the  metacarpus  of  the 
Horse.     It  goes  to  the  epicondyle  at  tlie  upper  extremity  of  the  fifth  metacarpal. 

4.  The  long  abductor  of  the  thumb,  resembling  a  portion  of  the  oblique  extensor  of 
the  metacarpus  of  animals.  Tliis  muscle  is  attached  to  the  posterior  face  of  the  ulna 
and  radius,  and  the  upper  extremity  of  the  first  metacarpal. 

5.  The  short  extensor  of  the  thumb,  which  is  also  represented  in  animals  by  a  portion 
of  the  oblique  extensor  of  the  metacarpus. 

6.  The  long  extensor  of  the  thumb,  arising  from  the  ulna,  and  inserted  into  the  second 
phalanx  of  tlie  thumb.  This  mu=cle  limits,  inwardly,  the  excavation  termed  the 
anatomical  snuff-box. 

7.  The  proper  extensor  of  the  index,  whose  tendon  is  confounded  with  the  branch  of 
the  common  extensor  passing  to  this  digit. 

These  two  latter  muscles,  blended  in  the  Dog,  exist  only  in  a  rudimentary  state  in 
the  other  animals. 

We  say  nothing  of  the  anconeus,  placed  in  the  antibrachial  region  by  anthropoto- 
mists,  and  which  has  been  described  in  the  posterior  brachial  region. 

MrSCLES   OF   THE   ANTERIOR   FOOT   OK   HAND. 

These  will  be  studied  successively  in  Carnivora,  the  Pig,  Solipeds,  and  Ruminants. 

A.  Muscles  of  the  Anterior  Foot  or  Hand  of  Carnivora. 

All  the  muscles  of  the  human  hand  are  found  in  tlint  of  Carnivora,  some  perfectly 
developed,  otliers  quite  rudimentary.  These  muscles  are:  1,  The  short  abductor  of  the 
thumb;  2,  The  opponent  of  the  thumb;  3,  The  short  flexor  of  the  thumb ;  4,  An  adductor 
of  the  index — adductor  of  the  tlmmb  in  Man ;  5,  The.  cutaneous  palmar  ;  6,  The  adductor 
of  the  small  digit ;  7,  The  sliort  flexor  of  the  small  digit;  8,  The  opponent  of  the  small 
digit ;  9,  The  three  lumbrici  ;  1 0,  Four  interosseous  metacarpah. 

1.  ShoH  Abductor  of  the  Thumb.    (Fig.  125,  D,  9.) 

This  is  rudimentary,  like  the  digit  it  is  intended  to  move,  and  is  situated  behind 
the  metacarpal  bone  of  the  thumb ;  it  is  composed  of  very  pale  fleshy  fasciculi,  which 
are  continued  inferiorly  by  tome  tendinous  fibres.  It  has  its  origin  at  the  carpal  arch, 
and  terminates  on  the  metacarpal  bone  of  the  thumb,  as  well  as  at  the  external  side  of 
the  superior  extremity'  of  the  first  phalanx.     It  is  a  flexor  and  abductor  of  the  thumb. 


'  It  is  necessary  to  remember  that  the  position  of  the  digits  is  considered  in  relation  to 
the  axis  of  the  hand — that  is,  the  median  line  separating  the  medius  from  the  annularis 


MUSCLES  OF  THE  ANTERIOR  LIMBS.  277 


2.  Opponent  of  the  Tlmmb.     (Fig.  125,  d,  10.) 

This  vestige  of  the  thick  short  muacle  which  bears  the  same  name  in  Man  is  situated 
beneath  and  witliin  the  preceding,  iu  a  slightly  oblique  dirtction  downwards  and 
outwards.  Pale  and  almost  entirely  muscular,  it  is  attached  to  the  posterior  ligament 
of  the  carpus  and  the  metacarpal  bone  of  the  thumb.  Owing  to  the  conformation  of  this 
digit  in  Carnivora,  this  muscle  cannot  act  as  it  does  in  Man  in  producing  the  opposition 
of  the  thumb ;  it  only  draws  it  towards  the  a,xis  of  the  hand,  and  is  therefore  merely  an 
adductor  of  the  thumb. 

3.  Short  Flexor  of  the  Thumb.    (Fig.  125,  D,  11.) 
A  very  small  muscle,  deeper  in  colour  than  the  other  two,  and  situated  between 
them,  the  adductor  of  the  index,  and  the  fourth  interosseous  muscle.     It  is  fixed,  by  its 
superior  extremity,  in  the  mass  of  the  posterior  carpal  ligament,  and  attached,  below,  to 
the  internal  side  of  the  fiist  phalanx.    It  is  a  somewhat  extensive  Hexor  of  the  thumb. 

4.  Adductor  of  the  Index.    (Fig.  125,  d,  12.) 
Synonym. — The  adductor  of  the  thumb  in  Man. 

Elongated,  prismatic,  compressed  on  each  side,  included  between  the  third  and 
fourth  interosseous  muscles,  and  concealed  by  tbe  tendinous  portion  of  the  common 
flexor  of  tlie  digits,  this  muscle  is  attached,  superiorly,  to  the  posterior  carpal  ligament 
with  the  third  interosseous  muscle.  It  is  fixed,  inferiorly,  by  melius  of  a  small  flattened 
tendon,  along  the  superior  and  internal  side  of  the  first  phalanx  of  the  index.  It  is 
legurded  as  the  adductor  of  the  thumb  in  Man  transformed  into  an  adductor  of  the  index, 
in  consequence  of  the  atrophy  of  the  fifth  digit. 

5.  Cutaneous  Palmar  (Palmar is  Brevis). 
A  thick,  hemispherical,  musculo-adipose  body,  forming  the  base  of  the  exterior 
tubercle  placed  behind  the  carpus.     It  adheres  intimately  to  the  skin  by  its  superficial 
face,  and  deeply  to  the  aponeurosis  covering  the  muscles  of  the  hand. 

6.  Adductor  of  the  Small  Digit.    (Fig.  125,  d,  14.) 

Tills  muscle  is  superficiully  situated,  external  to,  and  behind  the  outer  metacarpal 
bone,  and  is  composed  of  a  thick,  conical  fleshy  body,  concave  on  its  anterior  surface, 
convex  posteriorly,  and  of  a  long,  thin,  and  flat  tendon,  which  succeeds  the  inferior 
extremity  of  the  muscular  portion. 

It  is  attached,  by  the  superior  extremity  of  the  latter,  to  the  pisiform  bone ;  the 
tendon  terminates  outside  the  superior  extremity  of  the  first  phalanx  of  the  small  digit. 

This  muscle  separates  that  digit  from  the  axis  of  the  hand,  and  is  therefore  an 
abductor  and  not  an  adductor,  as  its  name  would  indicate.  That  name  has  been  given 
to  it  in  Man,  because  the  hand  has  been  considered  iu  a  state  of  supination,  a  position  in 
which  it  is  effectively  an  adductor  in  regard  to  the  median  plane  of  the  body.  If  this 
name  has  been  preserved  here,  it  ia  owing  to  a  desire  not  to  import  any  new  element  of 
confusion  into  a  nomenclature  already  too  complicated. 

7.  Short  Flexor  of  the  Small  Digit.    (Fig.  125,  d,  13.) 

Situated  within  the  preceding,  in  a  slightly  oblique  direction  downwards  and  out- 
wards, flattened  before  and  behind,  triangular,  and  almost  entirely  muscular,  this  muscle 
derives  its  origin  from  a  ligament  which  unites  the  pisiform  bone  to  the  metacurpal 
region,  and  terminates  inferiorly  on  the  tendon  of  the  atlductor,  whose  congener  it  is. 
It  may  also  concur  in  the  flexion  of  the  small  digit,  though  to  a  very  limited  degree. 

8.  Opponent  of  the  Small  Digit.     (Fig.  125,  D,  15.) 

A  muscle  elongated  from  above  downwards,  flattened  before  and  behind,  situated 
under  the  perforans  tendons,  behind  the  second  interosseous  muscle,  in  a  direction 
slightly  downwards  and  outwanis.  It  originates  from  the  posterior  ligament  of  the 
carpus,  and  terminates  within  the  superior  extremity  of  the  first  phalanx  of  the  external 
digit  by  a  small  tendon.  It  acts  as  an  adductor  by  drawing  the  small  digit  towards  the 
axis  of  the  hand. 
21 


278  THE  MUSCLES. 

9.  Lunthiici. 

These  small  muscles,  which  owe  their  name  to  the  resemblance  they  bear  to  the 
lumbricales  or  earthworms,  are  only  three  in  number  in  Carnivora.  They  occupy  the 
interval  between  the  four  chief  branches  of  the  perforans  tendon,  from  which  they  have 
their  origin  ;  they  terminate,  by  a  small  fibrous  digitation,  on  the  extensor  tendons  of 
the  tiiree  external  digits.  It  is  often  impossible  to  trace  them  so  far ;  for  they  are 
frequently  observed  to  stop  within  and  above  the  first  phalanx  of  the  digits  for  which 
tht-y  are  destined.     Their  functions  cannot  be  rigorously  defined  in  Carnivora. 

10.  Metacarpal  Interosseous  Muscles.     (Fig.  125,  D,  16,  16.) 
These  are  four  thick   and   prismatic    muscular  fasciculi,  elongated  from  above  to 
below,  bifid  at  their  inferior  extremity,   placed  parallel  to  one  another,  in  front  of  the 
flexor  tendons,  from  which  they  are  separated  by  a  thin  aponeurotic  layer,  and  behind 
the  four  large  metacarpals. 

They  have  their  origin  on  the  posterior  and  lateral  faces  of  these  bones,  as  well  as  on 
the  posterior  carpal  and  intermetacarpal  ligaments.  Each  terminates,  by  the  two 
branches  of  its  inferior  extremity,  on  t!ie  great  sesamoids  of  the  digit  to  which  it  corn-s- 
poiids.  There  they  are  continued  by  a  small  tendon,  which  joins  the  chief  extensor  of 
the  digit.  These  muscles  oppose  undue  extension  of  the  digits  while  the  animal  is  stand- 
ing, flex  them  on  the  metacarpal  bones,  and  maintain  the  extensor  tendons  on  the  anterior 
aspect  of  the  phalanges. 

B.  Muscles  of  the  Anterior  Foot  in  the  Fig. 
In  our  notes  on  the  myology  of  this  animal,  we  find-. 

1.  A  muscle  which  originates  in  the  sub.st:mce  of  the  metacarpo-supercarpal 
ligament,  and  terminates  on  the  proper  extensor  of  the  small  external  digit  by  a  fibrous 
strip  joined  to  the  external  fasciculus  of  the  first  interosseous  muscle ;  it  is  also  attached 
to  the  external  sesamoid.  Tiiis  is,  no  doubt,  the  representative  of  the  short  flexor  of  the 
small  digit  in  Man  and  the  Carnivora. 

2.  A  single,  but  very  voluminous  lumbricus,  fixed,  at  the  one  part,  to  the  perforans 
tendon,  and  at  the  other,  to  the  proper  extensor  tendon  of  the  small  internal  digit 
(index),  as  in  the  preceding  muscle. 

3  Four  interosseous  metacarpal  muscles,  similar  to  those  in  the  Dog,  and  whose 
terminal  digitations  join  the  proper  extensor  tendons.  The  interosseous  muscles  of  the 
two  :-mall  digits  are  not  only  divided  at  their  inferior  extremity,  but  throughout  their 
whole  length  are  observed  to  be  two  very  distinct  fasciculi,  one  superficial  iind  external, 
the  other  deep  and  internal.  The  fibrous  membrane  covering  these  muscles,  and  which 
separates  them  from  the  perforans  tendons,  is  much  thicker  than  in  the  Carnivora. 

C.  Muscles  of  the  Anterior  Foot  in  SoUpeds. 

In  Solipeds  only  two  Inimibrici  and  two  interosseous  metacarpal  muscles  have 
t)  bo  described. 

1.  The  lumbrici  originate  at  the  right  and  the  left  of  the  perforans 
tendon,  above  the  sesamoid  annular  band  (.f  the  perforatus.  They  each 
terminate  by  a  thin  tendon,  which  is  lost  in  the  fibrous  lamina  enveloping 
the  elastic  cushion  of  the  ergot  of  the  fetlock. 

2.  The  interosseous  muscles  (anterior  lumbrici — Percivall)  have  been 
wrongly  considered  by  French  veterinary  anatomists  as  lumbrici  muscles, 
and  are  described  by  them  as  the  superior,  or  great  lumhrici.  Situated  within 
the  rudimentary  metacarpal  bones,  these  two  little  muscles  are  formed  of  a 
very  delicate  fleshy  mass  imbedded  in  the  fibrous  tissue  surrounding  the  head 
of  the  metacarpal  bones,  and  of  a  long  tendon  which  descends  to  the  metacarpo- 
phalangeal articulation,  to  be  confounded  with  the  band  furnished  to  the 
anterior  extensor  of  the  phalanges  by  the  suspensory  ligament.  Sometimes 
this  tendon  is  directly  united  to  one  C)f  the  extensors  of  the  phalanges. 

These  two  muscles  represent  the  interossei  of  the  lateral  digits.  With 
regard  to  those  of  the  median  digit,  they  are  transformed,  as  we  have 
already  seen,  into  a  fibrous  brace  which  constitutes  the  suspensory  ligament 
of  the  fetlock. 


MUSCLES  OF  THE  ANTEBIOB  LIMBS. 


279 


D.  Muscles  of  the  Anterior  Foot  in  Buminants. 

These  animals  have  no  muscles,  properly  speaking,  in  the  region  of  the  foot ;  in  fact, 
we  only  find  in  them  the  supensory  ligament  of  the  fetlock,  which  is  the  interosseous  of 
the  two  complete  digits. 


COMPAKISOX   OF   THE   HAND   OF   MAN"   WITH   THAT   OF   ANIMALS. 

The  muscles  of  Man's  hand  are  numerous  and  well-developed,  in  consequence  of  the 
extent  and  variety  of  the  movements  of  its  various  parts.  They  are  divided  into  three 
groups:  the  external,  or  group  of  the  thenar  eminence,  induce  the  movements  of  the 
thumb ,  the  internal,  or  group  of  the  hypothenar  eminence,  those  of  the  little  finger ;  and 
the  middle  group,  occupying  the  metacarpal  spaces,  comprising  the  interosseous  muscles, 
In  addition,  there  is  found  in  the  hand  a  cuticularis  muscle,  the  cutaneous  palmaris 
{pcilmaris  brevis). 

The  cutaneous  palmaris  occupies  two-thirds  of  the  hypothenar  eminence;  its  fibres 
are  directed  downwards  and  inwards.  It  corrugates  the  skin  on  the  ulnar  border  of  the 
hand. 


A.  Muscles  of  the  Thenar  Eminence. 

These  muscles,  nearly  all  present  in  the  Dog, 
are  • 

1.  The  short  adductor  of  the  thumb,  whose 
fibres,  leaving  the  lower  portion  of  the  auti- 
brachial  aponeurosis,  the  process  of  the  trape- 
zius and  the  scaphoides,  are  succeeded  by  a  ten- 
don which  is  inserted  into  the  upper  extremity 
of  the  first  phalanx  of  the  thumb. 

2.  The  opponent  {ojjpoyiensj  of  the  thumb, 
which  passes  from  the  anterior  pait  of  the  tra- 
pezium to  the  external  border,  and  near  the 
anterior  face  of  the  first  metacarpal. 

3.  The  short  flexor  of  the  thumb,  a  muscle 
adjoining  the  preceding,  and  which  is  resolved 
into  two  series  of  fibres — a  deep  and  a  super- 
ficial. 

4.  The  short  adductor  of  the  thumb,  a  trian- 
gulor  muscle,  occupying  the  outer  half  of  the 
hollow  of  the  palm.  It  is  attached  to  the  os 
magnum,  along  the  entire  length  of  the  third 
metacarpal  bone  and,  by  a  tendon,  to  the  sesa- 
moid and  supero-internal  tuberosity  of  the  first 
phalanx  of  the  thumb. 

B.  Muscles  of  the  Hypothenar  Eminence. 

These  muscles  are :  1.  The  abductor  of  the 
little  finger,  a  small  fusiform  muscular  body, 
which  is  attached,  above,  to  the  pisiform  bone, 
and  below  to  the  supero-intemaJ  part  of  the 
first  phalanx. 

2.  The  short  flexor  of  the  little  finger,  situ- 
ated without  the  preceding,  fixed  in  one  part 
to  the  process  of  the  unciform  bone,  and  in  the 
other  to  the  inner  part  of  the  first  phalanx. 

3.  The  opponent  {opponens)  of  the  little  finger, 
a  triangular  muscle,  situated  below  the  pre- 
ceding. It  is  inserted  into  the  process  of  the 
unciform  bone,  then  into  the  inner  border  of 
the  fifth  metacarpal  and  the  adjacent  portion  of  its 


Fig.  128, 


MUSCLES  OF   HTTMAy   HAND. 

,  Annular  ligament ;  2,  2,  Origin  and.  in- 
sertion of  the  abductor  pollicis  muscle  ; 
3,  Flexor  ossis  metacarpi,  or  opponens 
pollicis ;  5,  Deep  portion  of  flexor  brevis 
pollicis ;  6,  Adductor  pollicis ;  7,  7,  Lum- 
bricales  muscles  arising  from  the  deep 
flexor  tendons,  upon  wliich  the  figures 
are  placed  ,  8,  A  tendon  of  deep  flexor  ; 
9,  Tendon  of  flexor  longus  pollicis;  10, 
Abductor  minimi  digitii ;  11,  Flexor 
brevis  minimi  digitii ;  12,  Pisiform 
bone;  13,  First  dorsal  interosseous 
muscle,  the  abductor  indicis. 

anterior  face. 


C.  Interosseous  Muscles. 

"  The  interosseous  muscles  are  situated  in  each  interosseous  space,  two  for  each  space, 
and  are  divided  into  dorsal  and  palmar.  As  there  are  four  interosseous  spaces,  there  ought 
to  be  eight  muscles ;  but  it  is  usual  to  exclude  the  short  adductor  of  the  thumb,  because 


280  TEE  MUSCLES. 

of  its  special  insertions;  this  reduces  the  total  number  of  interosseous  muscles  to  seven — 
four  dorsal  and  three  i^ahnar. 

"  These  small  muscles  arise  from  the  lateral  faces  of  the  metacarpals  to  the  lateral 
and  upper  portions  of  the  first  phiilanges.  By  their  contraction,  they  incline  these 
phalaYiges  laterally,  and  consequently  carry  the  corresponding  digit  inwards  and 
outwards." 

It  may  be  added  that  the  lumbrici  muscles  are  small  muscular  and  tendinous 
fasciculi  annexed  to  the  tendons  of  the  deep  flexor  of  the  phalanges,  and  whose  tendons 
terminate  on  the  external  side  of  the  four  last  digits  in  becoming  blended  with  the 
interossei. 

Article  III. — Muscles  of  the  Postekiok  Limbs. 

These  form  four  principal  groups  :  the  muscles  of  the  croup,  thigh,  leg, 
and  foot. 

MUSCLES    OF    THE    GLUTEAL    REGION   OR    CROUP. 

This  region  is  composed  of  three  superposed  muscles,  which  are  applied 
to  the  ilium,  and  are  distinguished  according  to  their  relative  situation  as 
the  superficial,  median,  and  deep  gluteus} 

They  are  covered  by  a  thick  fibrous  fascia,  a  prolongation  of  the  aponeu- 
rosis of  the  great  dorsal,  and  which  is  continued  backwards  over  the  muscles 
of  the  posterior  crural  region,  where  it  is  confounded  with  the  superficial 
lamella  of  the  fascia  lata.  This  gluteal  aponeurosis  is  fixed  to  the  external 
an^le  of  the  ilium  and  the  supersacral  spine.  By  its  deep  face  it  gives 
attachtoent  to  several  fasciculi  of  the  superficial  and  middle  glutei. 

Preparation. — 1.  Place  the  animal  on  its  side,  or,  better,  in  the  second  position. 
2.  Remove  the  skin  from  this  region  in  order  to  show  the  gluteal  aponeurosis,  and  to 
study  its  extent,  attachments,  and  relations.  3.  Cut  away  this  aponeurosis  to  expose 
the  anterior  point  of  the  middle  gluteus  and  the  muscular  portion  of  the  superficial. 
To  prepare  the  aponeurotic  portion  of  the  latter  muscle,  the  sacro-sciatic  insertion  of  the 
long  vastus  must  be  detached  by  the  scalpel  and  thrown  downwards.  4.  Incise  the 
superficial  gluteus  near  its  femoral  insertion,  and  reverse  it  on  the  sacral  spine,  so  as  to 
lay  bare  the  external  face  of  the  middle  or  principal  gluteus.  6.  Divide  this  muscle  near 
its  femoral  insertions,  taking  care  not  to  injure  these,  and  remove  the  whole  of  its  mass, 
studying  meanwhile  the  nature  of  its  relations  to  the  parts  it  covers  ;  the  deep  or  small 
gluteus  then  becomes  apparent,  and  may  be  conveniently  examined. 

1.  Superficial  Gluteus.    (Fig.  129,  4.) 

Synonyms. — Ilio-trochanterius  medius — Girard.  Gluteus  minor — Bourgelat.  Gluteus 
medius — Bigot  and  Lafosse.  The  gluteus  magnus  of  Man.  (Gluteus  externus — Percivall. 
Ilio-trochanterius  externus — Leyh.) 

Composition — Situation. — This  muscle  is  composed  of  a  fleshy  portion, 
situated  beneath  the  gluteal  aponeurosis,  and  an  aponeurotic  portion  entirely 
concealed  by  the  anterior  portion  of  the  long  vastus  (abductor  magnus 
— Percivall). 

Form  and  Structure. — The  muscular  portion  is  triangular,  and  most 
frequently  divided  into  two  branches,  an  external  and  internal,  by  an  ex- 
cavation which  deeply  indents  its  superior  border.  Its  constituent  fasciculi 
are  very  thick,  loosely  attached"  to  each  other,  and  are  all  directed  back- 
wards and  downwards  to  converge  into  a  flat  tendon,  which  terminates  the 
inferior  angle  of  the  muscle.  The  aj)oneurosis  likewise  terminates  the  in- 
ferior angle   of  the  muscle.     This   aponeurosis,  also   triangular,  is   con- 

'  For  the  justification  of  the  employment  of  these  new  denominations  see  note, 
page  177 


MTSCLES  OF  THE  POSTERIOR  LIMBS.  281 

fonnded,  anteriorly,  with  the  posterior  border  of  the  muscular  portion  of  its 
terminal  tendon;  at  its  inner  and  superior  border  it  degenerates  into 
cellular  tissue. 

Attachments. — This  muscle  has  its  fixed  insertion:  1,  On  the  internal 
aspect  of  the  gluteal  aponeurosis,  by  the  superior  extremity  of  its  muscular 
fasciculi  ;^  2,  On  the  postero-external  angle  of  the  ischium,  and  the  ischiatic 
ligament,  by  the  internal  border  of  its  aponeurotic  portion.  It  has  its 
movable  insertion,  by  means  of  its  terminal  tendon,  on  the  small  external  or 
thii'd  ti'Ochanter  of  the  femui". 

Belations. — Outwardly,  with  the  gluteal  aponeurosis  and  the  anterior 
portion  of  the  long  vastus.  Inwardly,  -^-ith  the  middle  gluteus ;  by  its 
anterior  border,  with  the  fascia  lata,  to  which  it  is  closely  united. 

Action. — -This  muscle  has  been  justly  considered  by  Lafosse  as  an  abductor 
of  the  thigh.  Bourgelat  wrongly  regarded  it  as  an  extensor,  and  Girard 
and  Rigot  have  repeated  his  error.  Lecoq  has  proved  that  it  rather  produces 
flexion  than  extension.  (Leyh  states  that  it  is  an  extensor  and  a  rotator  of 
the  thigh  outwards.) 

2.  Middle  Gluteus.     (Fig.  129,  1.) 

Synonyms. — Ilio-trochanterius  magnus — Girard.  Gluteus  masimus — Bourgelat, 
Lafogse,  Eiqot,  etc.  Gluteus  medius  of  Man.  {Gluteus  maximus — Perch-all.  Superior 
portion  of  the  great  ilio-trochanterius — Leyh.) 

Volume — Situation. — This  muscle,  the  largest  of  the  glutei,  presents  a 
considerable  volume,  and  is  applied  against  the  iliac  fossa,  the  sacro-ischiatic 
ligament,  and  the  ilio-spinalis  muscle. 

Form  and  Structure. — It  is  elongated  from  before  to  behind,  wide  and 
very  thick  in  its  middle,  prolonged  forward  by  a  thin  point,  and  terminated 
behind  by  three  branches  of  insertion — two  tendinous  and  one  muscular. 
The  muscular  fasciculi  entering  into  its  composition  are  generally  very 
thick  and  more  or  less  long ;  all  converge  towards  the  posterior  insertions 
of  the  muscle. 

Attachments. — 1,  By  the  superior  or  anterior  extremities  of  the  muscular 
fasciculi,  on  the  internal  aspect  of  the  gluteal  aponeurosis,  the  aponeurosis 
of  the  common  mass,  the  superior  face  and  the  two  anterior  angles  of  the 
ilium,  the  two  sacro-iliac  ligaments,  and  a  small  portion  of  the  sacro-ischiatic 
ligament.  2,  On  the  trochanter  (major)  by  its  three  posterior  branches : 
the  first,  or  median,  is  a  thick,  round  tendon  fixed  on  the  summit ;  the 
anterior  is  formed  by  a  second  wide,  thin,  and  flat  tendon,  which  is  inserted 
into  the  crest,  after  gliding  over  the  convexity ;  the  posterior  is  a  small, 
triangular,  fleshy  slip,  aponeui'otic  at  its  anterior  border,  by  means  of  which 
it  is  attached  behind  the  trochanter.  This  slip  corresponds  to  the  pyramidal 
muscle  of  Man. 

Belations. — Covered  by  the  gluteal  aponeurosis  and  the  superficial  gluteal 
muscle,  it  covers  the  ilio-spinalis,  which  receives  its  anterior  point,  the 
iliac  fossa,  the  small  gluteal,  the  ilio-sacral,  and  sacro-ischiatic  ligaments,  the 
sciatic  nerves,  and  the  gluteal  nerves  and  vessels.  Near  the  external  angle 
of  the  ilium  it  is  bordered  by  the  fascia  lata  and  the  iliacus,  which  are 
closely  united  to  it. 

Action. — When  its  fixed  point  is  superior,  this  muscle  extends  and  abducts 
the  thigh ;  but  when  the  femiir  is  fixed,  it  causes  the  pelvis  to  rock  on  the 

'  "We  have  been  frequently  able  to  convince  ourselves  that  none  of  the  fasciculi  of 
the  superficial  gluteus  proceed  direct  from  the  ilium  or  the  sacral  spine. 


282 


THE  MUSCLES. 


superior  extremity  of  that  bone,  and  assists  in  rearing.    In  the  first  instance 
it  acts  as  a  lever  of  the  first  order ;  in  the  second,  as  one  of  the  third  order. 

Fig.  129. 


SUPERFICIAL  MUSCLES  OF  THE  CROUP  AND  THIGH. 

1,  Middle  glutens,  or  gluteus  maximus ;  2,  Anterior  spinous  process  of  ilium  ;  3, 
Muscle  of  the  fascia  lata,  or  tensor  vaginse ;  4,  Superficial  gluteus,  or  gluteus 
externus ;  *,  Great  trochanter  of  femur  ;  5,  Fascia  lata ;  6,  Patella,  with  insertion 
of  rectus ;  7,  Long  vastus,  or  adductor  magnus ;  8,  Superior  and,  9,  lateral  coccy- 
geal muscles;  10,  Semitendinosus  and  semimembranosus;  11,  12,  Inferior 
portions  of  long  vastus;  13,  Fascia  of  the  thigh;  14,  Vastus  externus. 

3.  Deep  Gluteus.    (Fig.  131,  5.) 

Synonyms. — Ilio-troclianterius  parvus — Girard.  Gluteus  medius — Bourgelat.  Glu- 
teus minimus— La/osse  and  Eigot.  The  gluteus  minimus  of  antliropotomists.  {Gluteus 
internus — Percivall.) 

Form — Situation. — A  small,  short,  thick,  and  quadilateral  muscle, 
flattened  above  and  below,  situated  beneath  the  preceding,  and  above  the 
coxo- femoral  articulation. 

Structure  and  Attachments. — It  is  composed  of  voluminous  muscular  and 


MUSCLES  OF  THE  POSTERIOB  LIMBS.  283 

tendinous  fasciculi,  which  arise  from  the  neck  of  the  ilium  and  the  supra- 
cotyloid  ridge,  to  be  directed  outwards  and  backwards,  and  terminate  within 
the  convexity  of  the  trochanter. 

Relations  — Its  upper  face  responds  to  the  middle  gluteus  ;  the  inferior 
covers  the  coxo-femoral  articulation,  and  strongly  adheres  to  the  fibrous 
capsule  of  that  joint ;  this  face  is  also  separated  from  the  anterior  giacilis 
(ilio-femoralis)  of  the  thigh  and  the  origin  of  the  anterior  rectus  (rectus 
femoris),  by  a  very  strong  fibrous  layer,  which  extends  from  the  external 
border  of  the  ilium  to  the  base  of  the  trochanter.  Its  posterior  border  is  in 
relation  with  the  anterior  gemellus  of  the  pelvis. 

Action.— \t  is  the  special  abductor  of  the  thigh,  and  is  also  an 
accessory  rotator  of  the  femur  inwards.  (Leyh  says  it  is  a  congener  of  the 
preceding  muscle,  and  therefore  an  extensor  of  the  thigh.  It  may  also 
maintain  the  capsular  ligament  tense.) 

DIFFEEENTIAL   CHARACTEKS   OF   THE   MUSCLES   OP   THE   GLUTEAL   REGION   IN   OTHER   THAN 

SOLIPED   ANIMALS. 

In  Eumhiants  and  the  Pig,  the  gluteal  muscles  much  resemble,  though  they  sensibly 
differ  from,  those  of  ^olipeds.  In  fact,  the  superficial  gluteus  and  the  long  vastus  form 
but  one  and  the  same  muscle  ;  the  ini'hJle  gluteus,  thinner  than  in  the  Horse,  is  not  so 
much  prolonged  in  front  on  the  ilio-spinalis ;  and,  on  the  contrary,  the  deep  gluteus, 
more  developed  than  in  the  Horse,  is  easily  divided  into  two  portions,  which  Kigot  has 
designated  as  two  distinct  gluteals. 

In  Gdrnivora,  the  superficial  gluteus  is  voluminous ;  it  proceeds  from  the  sacrum, 
and  terminates  by  an  aponeurosis  below  and  behind  the  trochanter.  This  aponetirosis 
receives,  in  front,  a  small  muscular  band  which  arises  by  tendinous  fibres  from  the 
surface  of  the  middle  gluteus,  near  the  external  angle  of  the  ilium,  and  which  resembles 
the  external  branch  of  the  superficial  gluteus  of  the  Horse.  In  these  animals,  also,  the 
middle  gluteus  does  not  extend  beyond  the  lumbar  border  of  the  ilium  in  front,  and 
terminates  behind  by  a  single  branch. 

COMPARISON    OF   THE   GLUTEAL   MUSCLES   OF   MAN   WITH   THOSE   OF   ANIMALS. 

The  gluteal  muscles  are  distinguished,  in  regard  to  their  volume,  into  gi-eat,  medium, 
and  small  (see  note,  p.  177). 

The  great  gluteus  (gluteus  maximus)  corresponds  to  the  superficial  gluteal  of  animals. 

The  medium  gluteus  (gluteus  medius)  to  the  middle  gluteus  of  Solipeds. 

The  small  gluteus  (gluteus  minimus)  to  the  deep  gluteus. 

The  medium  gluteus  does  not  extend  beyond  the  crest  of  the  ilium  in  -front  (see 
Figs   138,  1H4). 

With  regard  to  the  great  gluteus,  it  is  inserted  inwardly  into  the  sacrum  and  the 
coccyx ;  below,  into  the  external  bifurcation  of  the  linea  aspeia,  from  the  trochanter  to 
the  midtUe  third  of  the  femur. 

MUSCLES    OF    THE    THIGH. 

These  have  been  divided  into  three  secondary  regions,  which  are  :  the 
anterior  crural  (or  femoral)  or  patellar,  the  posterior  crural  (ov  femoral),  and  the 
internal  crural  (or  femoral)  region. 

A.  Anterior  Crural  or  Femoral  Begion. 

This  region  comprises  three  muscles  situated  in  front  of  the  femur :  the 
muscle  of  the  fascia  lata,  the  crural  triceps,  and  the  anterior  gracilis  of  the 
thigh. 

Preparation. — 1.  Place  the  subject  in  the  first  posit'on.  2.  Study  the  fascia  la.a 
muscle  immediately  after  removing  the  skin  from  this  region.  3.  Take  away  th  s 
muscle  and  the  superficial  gluteus,  the  long  vastus,  the  semitendinosis  and  semimcm- 
brauosis,  the  two  adductors  of  the  leg,  the  peetiueus,  and  the  two  adductors  of  the  clii.L'h, 
to  expose  the  tliree  portions  of  the  triceps.  Separate  these  thrte  muscular  divisions  frrm 
one  another,  commencing  above  where  they  are  scarcely  adherent.  Dis&ect  the  anterior 
gracilis  at  the  same  time. 


28i  THE  MUSCLES. 

1.  Muscle  of  the  Fascia  Lata.    (Fig.  129,  3.) 

Synonyms. — Hio-aponeuroticus — Girard.  {Tensor  vaginx — Percivall.  Ischio  rotu- 
leus  externus — Leyh.) 

Form — Situation. — A  flat  and  triangular  muscle,  situated  in  front  of  the 
superficial  gluteus,  and  outside  the  external  vastus. 

Structure — Attachments. — It  comprises  :  1,  A  flahelliform  muscular 
portion  covered  on  its  faces  by  tendinous  fibres,  and  attached,  superiorly,  to 
the  external  angle  of  the  ilium ;  2,  An  aponeurosis  named  the  fascia  lata, 
continuous  with  the  inferior  border  of  the  muscular  portion,  and  soon  divided 
into  two  superposed  layers,  one  superficial,  the  other  deep.  The  latter  is 
insinuated  between  the  long  vastus  and  the  external  vastus,  joins  the  terminal 
tendon  of  the  superficial  gluteus,  and  is  inserted  into  the  external  border  of 
the  femur.  The  first,  which  also  appears  to  divide  into  two  layers,  is  spread 
outwardly  over  the  long  vastus,  where  it  is  confounded  with  the  gluteal 
aponeurosis  ;  and  inwardly,  over  the  internal  crural  muscles,  to  become 
united  to  the  femoral  ajjoneurosis.  Below,  it  is  prolonged  to  the  patella, 
into  which  it  is  fixed  ;  it  is  even  continued  below  that  bone,  to  join  the  terminal 
aponeurosis  of  the  posterior  branch  of  the  long  vastus. 

Belations. — Outwards,  with  the  skin ;  inwards,  with  the  external  vastus, 
the  anterior  rectus,  and  the  iliacus ;  behind,  with  the  superficial  and  middle 
glutei.  In  front,  it  responds  to  a  cluster  of  lymphatic  glands,  and  receives 
on  its  aponeurosis  the  insertion  of  the  panniculus  carnosus. 

Action. — It  flexes  the  femur  by  raising  the  entire  limb,  and  renders  tens© 
its  own  terminal  aponeurosis. 

(In  speaking  of  the  uses  of  this  muscle,  Leyh  states  that,  in  addition  to 
its  being  a  flexor  of  the  thigh  and  an  extensor  of  the  leg  through  its  action 
on  its  aponeurosis,  it  maintains  the  position  of  the  limb  while  the  animal  is 
standing,  and  allows  the  other  muscles  to  become  relaxed.) 

2.  Crural  Triceps} 

An  enormous  muscle  lying  against  the  anterior  and  lateral  aspects  of  the 
femui",  composed  of  three  portions  which  are  not  very  distinct  from  each 
other  for  the  greater  part  of  their  extent,  and  which  are  separately  described 
as  the  anterior  rectus  or  straight  muscle,  and  the  vastus  externus  and  internus. 

A.  Anterioe  Straight  Muscle  of  the  Thigh,  or  Middle  Portion  of 
THE  Triceps. 

The  ilio-rotuleus  of  Girard.  {Rectus — Percivall.  Anterior  ilio-rotuleus — Leyh.) 
(Fig.  137,  16.) 

This  muscle  is  imbedded  between  the  two  lateral  portions  of  the  triceps, 
and  extends  from  the  cotyloid  angle  of  the  ilium  to  the  patella,  in  a  direction 
slightly  oblique  forwards  and  downwards. 

Form — Structure. — Elongated,  thick,  and  fusiform,  the  anterior  rectus 
offers,  at  its  superior  extremity,  two  short  and  flattened  tendinous  branches ; 
its  middle  portion  is  formed  of  pale-red  muscular  fibres  lying  close  to  each 
other,  and  marked  by  tendinous  intersections;  its  inferior  extremity  is 
enveloped  by  a  vast  aponeurotic  cone. 

Attachments. — It  originates,  by  its  two  superior  branches,  from  the 
imprints  which  surmount,  forwards  and  outwards,  the  lip  of  the  cotyloid 

'  Following  the  exnmple  of  M.  Cruveilliier,  we  will  rlescrihe  by  this  name  the  triceps 
cruris  of  the  older  anatomists,  and  the  anterior  rectus  of  the  thigh. 


MUSCLES  OF  THE  POSTERIOR  LIMBS.  285 

cavity.  It  terminates,  by  its  inferior  extremity,  on  the  anterior  face  of  the 
patella.  » 

Relations. — Externally,  internally,  and  posteriorly,  with  the  two  other 
portions  of  the  triceps  ;  anteriorly,  with  the  muscle  of  the  fascia  lata.  Its 
superior  extremity,  included  between  the  iliacus  and  the  deep  gluteus,  is 
separated  from  the  coxo-femoral  capsule  by  a  little  adipose  cushion  which  is 
insinuated  between  its  two  branches. 

Action. — An  extensor  of  the  leg  and  flexor  of  the  thigh. 

B.  External  Vastus  (Fig.  129,  4). — Form— Extent — Situation. — This 
is  a  thick  and  wide  muscular  mass,  flattened  on  each  side,  extending  from 
the  superior  extremity  of  the  femur  to  the  patella,  and  situated  to  the 
outer  side  of  the  anterior  rectus. 

Structure  and  Attachments. — The  fasciculi  composing  this  muscle  are 
intermixed  with  strong  aponem'otic  layers,  and  originate  from  the  whole 
outer  surface  of  the  femur  and  the  external  half  of  its  anterior  face ;  they 
are  directed  forwards  and  downwards,  to  terminate  either  on  the  anterior 
rectus,  or  on  the  superior  face  and  external  side  of  the  patella. 

Relations. — -Outwardly,  with  the  fascia  lata  and  super^cial  gluteus; 
inwardly,  with  the  anterior  rectus  and  the  vastus  internus,  which  is  inti- 
mately confounded  with  it  excej^t  towards  the  superior  extremity  of  the 
femur,  where  the  two  muscles  are  distinctly  separate;  behind,  with  the 
femur  and  the  long  vastus. 

Action. — It  is  an  extensor  of  the  leg. 

C.  Vastus  Internus  (Figs.  131,  7  ;  137,  17). — This  muscle  is  not  very 
distinct  from  the  preceding  fur  the  greater  j)art  of  its  extent,  and  forms  with 
it  a  deep  and  wide  channel,  in  which  the  anterior  rectus  is  lodged.  It  is  a 
repetition  of  the  vastus  externus  in  so  far  as  its  form,  structure,  extent, 
attachments,  and  action  are  concerned ;  but  it  possesses  the  following 
peculiarities : 

The  fibres  entering  into  its  composition  arise  from  the  whole  internal 
face  and  the  inner  half  of  the  anterior  face  of  the  femur,  and  go  to  be 
inserted,  some  on  the  aponeurosis  of  the  rectus,  others  on  the  internal 
patellar  ligament,  the  corresponding  side  of  the  patella,  and  on  the  superior 
face  of  the  same  bone,  in  common  with  the  vastus  externus. 

Relations. — By  its  external  face,  it  responds  to  the  latter  muscle  and 
the  rectus ;  by  its  internal  face,  to  the  internal  crural  aponeurosis,  the  long 
adductor  of  the  leg,  the  iliacus,  pectineus,  and  to  the  long  branch  of  the 
great  adductor  of  the  thigh. 

8.  Anterior  Gracilis.     (Figs.  90, 11 ;  131,  6.) 

Stinomjms. — Gracilis  anterius — Bigot.  Ilio-femoral  gracilis — Girard.  (^Crureus  vel 
cruralis — Percivall.) 

A  small  cylindi-ical  muscle,  situated  in  front  of  the  capsule  of  the  coxo- 
femoral  articulation,  alongside  the  fibrous  fasciculus  that  strengthens  the 
anterior  portion  of  this  membranous  ligament. 

Attachments. — It  originates  from  the  ilium,  very  near,  and  to  the  outside 
of,  the  external  branch  of  the  anterior  rectus  ;  it  afterwards  insinuates  itself 
between  the  two  vasti,  and  terminates  on  the  anterior  aspect  of  the  femur 
by  aponeurotic  fasciculi. 

Relations. — This  muscle  is  included  between  the  three  portions  of  the 
triceps  and  the  capsidar  ligament  of  the  coxo-femoral  articulation,  to  which 
it  strongly  adheres. 


286  THE  MUSCLES. 

Action. — It  appears  to  raise  (or  render  tense)  tlie  capsular  ligament 
during  flexion  of  the  femur. 

B.  Posterior  Crural  Begion. 

This  region  is  constituted  by  three  muscles  situated  behind  the  thigh. 
These  are  the  long  vastus,  the  semitendinosus,  and  the  semimemhranosus. 

Preparation. — Place  the  subject  in  the  first  position,  allow  one  hind  leg  to  lie 
unfastened,  and  incline  the  body  to  the  corresponding  side,  leaving  the  other  limb 
attached  to  the  supporting  bar,  with  the  thigli  slightly  flexed  to  make  these  muscles 
tense.  These  preliminary  arrangements  being  adopted,  proceed  in  the  following 
manner:  1.  Make  a  transverse  incision  tlirough  the  short  adductor  of  the  thigh,  an(i 
turn  back  the  two  portions  to  the  right  and  left,  so  as  to  expose  the  whole  of  the 
semimembranosus,  wliich  is  to  be  afterwards  dissected  from  the  semitendinosus  and  the 
great  adductor  of  the  thigh.  2.  After  removing  the  aponeurosis  covering  the  long  vastus 
and  semitendinosus,  the  latter  is  to  be  dissected  by  circumscribing  as  carefully  as 
possible  its  two  superior  insertions.  3.  The  long  vastus  is  then  to  be  prepared  by 
isolating  the  two  component  portions,  whose  sacro-sciatic  insertion  is  revealed  by 
dividing  the  analogous  msertion  of  the  semitendinosus ;  after  wliich,  reflect  the  entire 
muscle  iu  order  ^  study  itsxieep  face,  its  femoral  insertion,  and  its  relations  with  the 
subjacent  organs. 

1.  Long  Vastus.     (Fig.  129,  7.) 

Synomjms. — Ischio-tibialis  externus — Girard.  The  biceps  femoris  and  part  of  the 
gluteus  maximus  of  Man.  ^The  biceps  abductor  femoris  of  Percivall.  Anterior  pubio- 
ischio-tibialis — Leyh.) 

Volume — Situation — Extent— Direction. — This  muscle  offers  an  enor- 
mous volume,  as  its  name  indicates ;  it  is  situated  behind  the  thigh  and 
the  glutei  muscles,  and  forming  a  curve  with  its  concavity  forwards,  it 
extends  from  the  sacral  spine  to  the  superior  extremity  of  the  leg. 

Form  and  Structure,—  It  is  composed  of  two  prismatic  portions  perfectly 
distinct  from  each  other  for  nearly  the  whole  of  their  extent,  lying  side  by 
side,  and  designated  as  anterior  and  posterior. 

The  anterior  iwrtion,  the  most  considerable  of  the  two,  is  very  wide  at 
its  upper  extremity,  and  singularly  contracted  below.  It  is  covered,  on  the 
inferior  half  of  its  deep  face,  by  a  broad  and  strong  tendinous  band,  which 
becomes  aponeurotic  in  ascending  towards  the  superior  extremity  of  the 
muscle.  Its  component  fibres  are  longest  posteriorly,  and  all  arise  from  the 
superior  extremity  to  be  inserted  into  the  teudinous  layer. 

The  posterior  portion,  much  shorter  than  the  preceding,  presents  an 
inverse  disposition,  being  contracted  at  its  upper  extremity  and  very 
wide  below.  Its  muscular  fibres  are  partly  attached,  by  their  superior 
extremities,  to  a  longitudinal  aponeurotic  layer,  which  gives  the  muscle  a 
penniform  appearance  ;  they  terminate,  inferiorly,  in  a  strong  aponeurosis 
united  to  that  of  the  fascia  lata. 

Attaclments. — The  anterior  portion  arises,  by  its  superior  extremity,  from 
the  sacral  spine,  the  sacro-ischiatic  ligament,  the  aponeurosis  enveloping  the 
coccygeal  muscles,  and  the  ischial  tubei'osity.  It  terminates :  1,  On  the 
circular  imprint  situated  behind  the  subtrochanterian  crest,  by  a  fibrous 
branch  detached  from  the  deep  tendon;  2,  On  the  anterior  face  of  the 
patella,  by  the  inferior  extremity  of  that  tendon. 

The  posterior  portion  commences  on  the  spine  and  tuberosity  of  the 
ischium,  where  it  joins  the  anterior  division.  Its  terminal  aponeurosis  is 
spread  over  the  tibial  muscles  to  constitute  the  fascia  of  the  leg,  and  is 
inserted  into  the  tibial  crest. 


MUSCLES  OF  TEE  POSTERIOR  LIMBS.  287 

Belations. — The  gluteal  aponeurosis  is  prolonged  over  the  external 
surface  of  the  long  vastus,  becomes  increased  in  thickness,  and  is  more  or  less 
elastic ;  it  strongly  adheres  to  this  muscle,  and  superiorly  gives  attachment 
to  a  great  number  of  its  muscular  fasciculi,  Inwards,  the  long  vastus 
responds :  To  the  aponeurosis  of  the  superficial  gluteus,  which  separates  it, 
for  the  most  part,  from  the  principal  gluteus  and  the  trochanter  ;  to  the  deep 
layer  of  the  fascia  lata,  which  isolates  it  from  the  external  vastus  ;  to  the 
anterior  face  of  the  patella,  over  which  it  glides  by  means  of  a  small 
synovial  bursa,  before  becoming  inserted;  to  the  external  muscles  of  the 
leg ;  to  the  sciatic  nerves ;  to  the  great  adductor  of  the  thigh,  and  to  the 
semimembranosus.  Inferiorly,  the  semitendinosus  is  related  to  its  internal 
face,  and  more  superiorly,  it  is  in  contact  with  the  posterior  border  of  this 
muscle,  whose  sacro-ischiatic  insertions  it  covers  by  its  upper  extremity. 

Action. — The  two  portions  of  the  long  vastus  do  not  act  in  the  same 
manner,  and  in  this  respect  they  are  essentially  distinct.  The  principal 
division,  pulling  the  patella  outwards  and  the  femur  backwards,  is  an 
abductor  of  the  entire  limb,  and  an  extensor  of  the  thigh  ;  while  the  posterior 
portion  merely  determines  the  flexion  of  the  leg  and  the  tension  of  the  tibial 
ajjoneurosis.^ 

If  the  leg  be  the  fixed  point,  this  muscle,  in  contracting,  causes  the 
pelvis  to  swing  on  the  head  of  the  femur,  and  in  this  way  it  plays  an 
important  part  in  rearing. 

2.  Semitendinoms.     (Figs.  129,  10 ;  130,  14.) 

iSi/noH ?/?«s.—Ischio-tibialis  medius  or  posticus— G/rarc?.  (^Posterior  sacro-iscMo- 
tibialis — Leijh.  Percivall  dtscribes  this  and  the  next  muscle  by  the  name  of  adductor 
tibialis.) 

Situation — Extent — Direction. — This  muscle  is  situated  behind  the  pre- 
ceding, and,  like  it,  extends  from  the  sacral  spine  to  the  leg,  describing  a 
curve  whose  convexity  is  posterior. 

Volume — Form — Structure. — Less  considerable  than  the  long  vastus,  it 
is  elongated  from  above  to  below,  bifid  at  its  superior  extremity,  thick  and 
prismatic,  but  nevertheless  compressed  on  both  sides.  Its  muscular  fibres 
are  of  a  pale-red  colom*,  are  parallel  to  each  other,  and  follow  the  general 
direction  of  tlie  muscle  ;  they  terminate,  inferiorly,  on  an  aponeurosis  and  on 
a  flattened  tendon. 

Attachments. — This  muscle  arises,  above,  by  one  of  its  branches  from  the 
sacral  spine  and  the  sacro-ischiatic  ligament,  in  common  with  the  long  vastus  ; 
by  the  other  branch,  which  is  the  shortest,  from  the  ischiatic  tuberosity. 
Its  inferior  aponeurosis  is  confounded  with  that  of  the  tibia ;  the  tendon 
glides  over  the  internal  surface  of  the  tibia,  and  is  inserted  into  its  anterior 
crest. 

Belations. — Its  sacro-ischiatic  branch  is  covered  by  the  gluteal  aponeurosis, 
and  covers  the  long  vastus.  For  the  remainder  of  its  extent,  it  responds  : 
posteriorly,  to  that  aponeurosis ;  anteriorly,  to  the  sciatic  nerves  ;  externally, 
to  the  long  vastus  and  gastrocnemius ;  internally,  to  the  semimembranosus 
and  the  long  adductor  of  the  thigh.  ^ 

Action. — It  is  a  flexor  of  the  leg,  and  tensor  of  the  tibial  aponeui'osis, 

'  If  it  were  wished  to  establish  a  comparison  between  the  nature  of  the  action  of  the 
two  portions  of  the  long  vastus,  and  their  relations  and  attachments,  their  analogues  in 
Man  could  be  easily  determined.  The  anterior  is  undoubtedly  a  considerable  portion  of 
the  gluteus  maximus,  prolonged  to  the  patella;  t!ie  posterior  represents  the  biceps 
femoralis. 


288  THE  MUSCLES. 

when  its  fixed  point  is  above ;  when  the  leg  is  fixed,  it  becomes  one  of  the 
active  agents  in  rearing 

3.  Semimembranosus.     (Figs.  129,  10  ;  130,  13.) 

Synonyms. — Ischio-tibialis  internus — Girard.    (Great  ischio-fenioralis — Leyh.) 

Situation — Volume — Extent — Direction. — Situated  within  the  semiten- 
dinosus,  and  shorter  and  thinner  than  it,  the  semimembranosus  extends  from 
the  ischium  to  the  inferior  extremity  of  the  femur,  and  follows  an  oblique 
direction  downwards  and  forwards. 

Form — Structure. — Elongated  vertically,  depressed  on  each  side,  pris- 
matic, thick  at  its  anterior,  and  very  thin  at  its  iiosterior  borders.  It  is  also 
voluminous  at  its  upper  extremity,  which  has  a  small  prolongation  whose 
point  ascends  to  the  base  of  the  tail ;  contracted,  and  terminated  by  a  short 
tendon  at  its  inferior  extremity.  It  is  formed  of  thick  muscular  fasciculi, 
which  all  terminate,  below,  on  the  tendon. 

Attachments. — Above :  1,  To  the  aponeurosis  of  the  coccygeal  muscles, 
by  the  thin  prolongation  from  its  superior  extremity ;  2,  To  the  ischiatic 
tuberosity,  and  on  the  inferior  face  of  the  ischium.  Below,  to  the  small 
eminence  situated  within  the  internal  condyle  of  the  femur. 

delations. — Inwards,  with  a  very  thru  prolongation  from  the  gluteal 
aponeurosis,  and  with  the  ischio-cavernous  muscle  and  short  adductor  of  the 
leg;  outwards,  with  the  semitendinosus,  the  long  vastus,  and  the  sciatic 
nerves  ;  in  front,  with  the  great  adductor  of  the  thigh,  which  is  so  intimately 
united  to  it  that  some  difficulty  is  experienced  in  separating  their  fibres. 

Action. — It  is  an  adductor  of  the  limb  and  an  extensor  of  the  thigh,  when 
its  fixed  point  is  above ;  but  when  the  femur  is  fixed,  it  is  an  auxiliary  in 
rearing. 

C.  Internal  Crural  Begion. 

This  region  comprises  nine  muscles,  applied  in  three  superposed  layers 
against  the  inner  aspect  of  the  thigh.  These  are :  the  long  and  short  ad- 
ductor of  the  leg,  forming  the  superficial  layer  ;  the  pectineiis  and  the  smcdl 
and  great  adductors  of  the  thigh,  forming  the  middle  layer.  Those  of  the 
deep  layer — that  is,  the  square  crureus,  external  obturator,  internal  obturator, 
and  gemini  of  the  pelvis,  are  not  all  situated  on  the  inner  face  of  the  femur, 
one  of  them  being  contained  within  the  pelvic  cavity.  With  these  muscles, 
which  do  not  present  a  very  considerable  volume,  another  region  might  be 
formed  and  designated  the  deep  pelvi-crural,  or  coxo-femoral  region. 

Preparation. — 1,  Place  the  subject  in  the  first  position.  2.  Prepare  on  one  side  the 
two  muscles  of  the  superficial  layer,  by  removing  the  slight  fibrous  layer  covering  them, 
the  internal  crural  aponeurosis,  and  the  inferior  parietes  of  the  abdomen.  3.  To  expose, 
on  the  opposite  side,  the  three  muscles  of  the  middle  layer,  cut  through  the  two 
adductors  of  the  leg,  and  turn  them  back  to  the  right  and  left;  separate  the  semi- 
membranosus from  the  great  adductor  of  the  thigh ;  it  may  be  even  useful,  in  order  to 
study  the  latter  muscle,  to  remove  the  entire  mass  of  the  three  ischio-tibial  muscles. 
4.  Dissect  the  small  deep  muscles  on  a  separate  piece,  as  shown  in  figures  90  and  131. 

1.  Long  Adductor  of  the  Leg.     (Fig.  130,  8.) 

Synonyms. — Sublumbo-tibialis — Girard.  (Sartorius — Percivall.  Internal  ilio-rotu- 
leus — Leyh.) 

Form — Situation — Direction. — This  muscle  is  long,  thin,  and  flattened, 
narrow  at  its  inferior  extremity,  and  situated  at  first  within  the  abdominal 


MUSCLES  OF  THE  POSTERIOR  LIMBS.  289 

cavity,  at  the  entrance  to  the  pelvis ;  afterwards,  inside  the  thigh ;  it  is 
oblique  from  above  to  below,  behind  to  before,  and  within  to  without. 

Structure, — It  is  formed  of  parallel  muscular  fibres,  and  terminates, 
inferiorly,  by  an  aponeurosis  which  is  confounded  with  that  of  the  short 
adductor. 

Attachments. — It  originates,  superiorly,  from  the  inferior  face  of  the  iliac 
fascia  near  the  tendon  of  the  psoas  parvus,  and  is  inserted,  by  means  of  its 
terminal  aponeurosis,  not  on  the  supero-internal  tuberosity  of  the  tibia, 
but  on  the  internal  patellar  ligament,  in  common  with  the  short  adductor. 

Relations. — It  is  covered  by  the  crural  aponeurosis  and  Poupart's  liga- 
ment, and  covers  the  iliacus,  psoas  magnus,  the  anterior  femoral  nerve,  and 
the  internal  vastus.  Superiorly,  its  inner  border  forms  the  limit,  with  the 
pectineus  and  the  anterior  border  of  the  short  adductor,  to  a  triangular  space 
occui)ied  by  the  crural  vessels ;  below  this  space  the  two  adductors  of  the 
leg  are  closely  adherent  to  each  other. 

Action. — It  adducts  the  leg,  and  flexes  the  femur. 

2.  Sliort  Adductor  of  tJie  Leg.     (Fig.  130,  9.) 
Synonyms. — Subpubio-tibialis  —Girard.    ( Gracilis — Percivall.    Pvhio-tibialis — Leyh.) 

Form — Situation — Direction. — A  large  quadrilateral  muscle,  thin  at  its 
borders,  situated  inside  the  thigh  in  an  oblique  direction  downwards  and 
outwards.     It  forms  the  base  of  what  is  called  the  j^a^  of  the  thigh. 

Structure. — Formed  of  parallel  muscular  fibres,  which  extend  from  its 
superior  to  its  inferior  border,  this  muscle  is  tendinous  at  its  origin,  is 
covered  by  an  albugineous  layer,  and  terminates  inferiorly  in  a  wide 
aponeurosis. 

Attacliments. — It  originates,  by  the  whole  extent  of  its  superior  border, 
from  the  ischio-pubic  symphysis,  and  is  confounded  with  the  muscle  of  the 
opposite  side — origin.  Its  terminal  aponeurosis,  united  with  that  of  the 
long  adductor,  is  inserted  on  the  internal  patellar  ligament  and  the  internal 
face  of  the  tibia—  movable  insertion;  posteriorly,  it  is  confounded  with  the 
aponeurosis  of  the  semitendinosus,  and  with  it  forms  the  tibial  aponeurosis 
enveloping  the  tibial  muscles. 

Belations. — Its  superficial  face  is  covered  by  a  cellulo-fibrous  layer,  and 
by  the  saphena  vessels  and  nerves.  It  covers,  by  its  deep  face,  the  pectineus, 
the  adductors  of  the  thigh,  the  semimembranosus  and  semitendinosus,  and 
the  internal  femoro-tibial  ligament.  It  is  traversed  at  its  origin,  and 
altogether  in  front,  by  a  very  large  venous  branch. 

Action. — An  adductor  of  the  limb  and  a  tensor  of  the  tibial  aponeu- 
rosis. 

3.  Pectineus.     (Fig.  180,  11.) 

Synonyms. — Superpubio-femoralis — Girard.  Its  anterior  branch  corresponds  to  the 
pectineus,  and  the  posterior  to  the  middle  adductor  in  Man.  (^Anterior  puhio-femoralis 
—Leyh.)  , 

Situation — Direction — Form. — Situated  beneath  the  preceding,  in  an 
oblique  direction  downwards,  forwards,  and  outwards,  this  muscle  is  conoid, 
thick,  and  bifid  at  its  superior  extremity,  contracted  at  its  inferior  extremity. 

Structure  and  Attachments. — Its  fascicidi  arise  either  from  the  anterior 
border  and  inferior  surface  of  the  pubis,  or  from  the  surface  of  the  pubio- 
femoral  ligament,  which  passes  between  its  two  branches— /a;ec?  insertion. 
They  are  enveloped,  at  their  inferior  extremity,  by  a  tendinous  cone,  which 


290 


THE  MUSCLES. 


is  attached,  on  tlie  inner  aspect  of  the  femur,  to  the  imprints  surrounding 
the  nutrient  foramen — movable  insertion. 

Action. — The  pectineus  is  an  adductor  and  flexor  of  the  thigh,  and  also 
rotates  it  inwardly. 

Fig.  130. 


MUSCLES  OF  THE  SUBLUJIBAR,  PATELLAR,  AND  INTERNAL  CRURAL  REGIONS. 
1,  Psoas  magnus ;  1',  Its  terminal  tendon ;  2,  Psoas  parvus ;  3,  Iliacus ;  4,  Its  small 
internal  portion ;  5,  Muscle  of  the  fascia  lata ;  6,  Rectus  of  the  thigh ;  7,  Vastus 
internus;  8,  Long  adductor  of  the. leg;  9,  Short  adductor  of  the  leg;  11,  Pecti- 
neus; 12,  Great  adductor  of  the  thigh;  12',  Small  adductor  of  the  thigh;  13, 
Semimembranosus;  14,  Semitendiaosus.— A,  Portion  of  the  iliac  fascia;  B, 
Portion  of  the  layer  reflected  from  the  aponeurosis  of  the  abdominal  great 
oblique,  formmg  Poupart's  ligament ;  c,  Pubic  tendon  of  the  abdominal  muscles ; 
D,  Origin  of  the  pubio-femoral  ligament. 

Belations. — Inwards,  with  the  short  adductor  of  the  leg ;  outwards  and 
forwards,  with  the  femoral  insertion  of  the  psoas  magnus  and  iliacus,  the 
vastus  iuternus,  the  crural  vessels, and  the  long  adductor  of  tlie  leg;  behind, 
with  the  small  adductor  of  the  thigh,  and,  near  its  superior  extremity,  with 
the  external  obturator^ 


MUSCLES  OF  TEE  POSTERIOR  LIMBS.  291 

Action. — This  muscle  is  an  adductor  and  flexor  of  the  thigh,  and  more 
particularly  a  rotator  inwards  of  the  same  ray. 

4.  Small  Adductor  of  the  Thigh.     (Figs.  130,  12;  137,  14.) 

Si/nonyms. — The  anterior  portion  of  the  biceps  femoralis  of  Boiircjelaf,  and  of  the 
subpubio-femoralis  of  Gimrd.'^  (Middle  puhio-femoraVs  of  I.eyh.  A  portion  of  the 
adductores  femoris  of  Percivall,  and  which  he  has  named  the  adductor  h-evis.) 

Situation — Direction. — This  muscle  is  situated  beneath  tlie  short  ad- 
ductor of  the  leg,  between  the  pectineus  and  the  great  adductor  of  the  thigh, 
in  an  oblique  direction  downwards  and  outwards. 

Form — Structure. — It  is  flat  from  before  backwards,  thick  and  narrow  at 
its  upper  extremity,  thin  and  wide  inferiorly.  Its  muscular  fibres  are  of  a 
pale-red  colom",  nearly  parallel  to  each  other,  and  sometimes  very  indistinct 
— superficially,  at  least — from  those  belonging  to  the  great  adductor  ;  infe- 
riorly, they  become  aponeurotic. 

Attachments. — Above,  to  the  inferior  face  of  the  pubis — origin  ;  below, 
to  the  roughened  quadrilateral  surface  on  the  posterior  aspect  of  the  femur, 
in  common  with  the  short  branch  of  the  great  adductor — termination. 

Belaiions. — Inwards,  with  the  short  adductor  of  the  leg ;  outwards,  with 
the  obturator  externus :  in  front,  with  the  pectineus ;  behind,  with  the  great 
adductor  of  the  thigh. 

5.  Great  Adductor  of  the  Thigh.     (Figs.  130,  12.) 

Synonyms. — Posterior  portion  of  the  biceps  femoralis  of  Bourgelat,  and  of  the  sub- 
pubio-femoralis of  Girard.  ( The  adductor  longus,  of  Percivall.  Posterior  puhio-femoralis 
— Leyh.) 

Situation — Direction. — The  great  adductor  is  situated  beneath  the 
preceding  muscle,  between  the  small  adductor  and  the  semimembranosus, 
proceeding  obliquely  downwards  and  outwards. 

Form — Structure. — It  is  a  long,  thick,  prismatic  muscle,  depressed  from 
before  to  behind,  terminating,  inferiorly,  by  two  branches  of  unequal  length, 
and  almost  entirely  composed  of  parallel  muscular  fibres,  which  are  generally 
distinguished  from  the  fasciculi  of  the  small  adductor  by  their  deeper 
colour. 

Attachments. — Above,  to  the  lower  face  of  the  ischium  and  to  the  single 
tendinous  band  which  attaches  the  two  muscles  of  the  flat  of  the  thigh  to 
the  pelvic  symphysis — origin.  Below :  1,  By  its  external  branch,  the 
thickest  and  shortest,  to  the  quadrilateral  scabrous  surface  on  the  posterior 
face  of  the  femur,  outside  the  small  adductor ;  2,  By  its  internal  branch, 
the  longest  and  thinnest,  to  the  supero-internal  condyle  of  the  femur,  in 
common  with  the  semimembranosus  and  the  internal  femoro-tibial  ligament 
— termination. 

Belations. — Inwards,  with  the  short  adductor  of  the  leg ;  behind,  with 
the  semimembranosus;  in  front,  with  the  small  adductor,  the  external 
obturator,  and  the  inferior  extremity  of  the  square  crural  muscle.  Its 
external   border,    thinner   than    the   internal,   partly    covers    the   superior 

*  After  mature  deliberation,  we  have  decided  on  describing  as  two  muscles  the  biceps 
femoralis  of  Bourgelat,  and  to  give  to  them  the  names  of  small  and  great  adductors  of 
the  thigh,  by  which  Bichat  has  designated  the  corresponding  muscles  in  the  lower 
extremity  of  ftliin.  We  have  thought  it  our  duty,  in  this  instance,  to  follow  the  example 
given  us  by  several  German  authors. 


292  '         THE  MUSCLES. 

extremity  of  the  latter  muscle,  and  is  separated  from  tLe  sciatic  nerves  and 
the  long  vastus  by  an  aponeiu'otic  lamina.  The  crural  vessels  pass 
between  its  two  branches,  one  of  which,  the  internal,  responds  anteriorly  and 
near  its  insertion  to  the  internal  vastus  muscle. 

Action. — This  muscle  is  an  adductor  and  extensor,  as  well  as  a  rotator 
outwards  of  the  femoral  ray. 

6.  Square  Crural.     (Figs.  90,  14 ;  131,  10.) 

Synonyms. — The  gracilis  internus  of  Eourgelat,  and  the  isehio-femoral  gracilis  of 
Girard.  (Js^'ot  described  by  Percivall.  Small  ischio-femoralis  of  Leyh.  The  quadratus 
femoris  of  Man.) 

Situation — Direction — Form — Structure. — Situated  on  the  posterior  face 
of  the  femur,  between  the  great  adductor  and  external  obturator,  and  oblique 
downwards  and  outwards,  the  quadratus  cruralis  is  a  small  band  flattened 
from  before  to  behind,  and  formed  of  parallel  muscular  fibres,  slightly  tendi- 
nous at  their  inferior  extremity. 

Attachments. — Above,  to  the  inferior  surface  of  the  ischium,  in  front  of 
the  ischiatic  tuberosity — origin;  terminating,  below,  on  the  linear  imprint 
on  the  posterior  face  of  the  femur,  a  little  below  the  trochanter. 

Belations. — In  front  with  the  posterior  face  of  the  femur  and  external 
obtm-ator.  Behind,  and  inwardly,  with  the  great  adductor  of  the  thigh. 
Outwards,  with  the  sciatic  nerves  and  the  posterior  gemellus  of  the  pelvis. 

Action. — It  is  an  extensor  and  adductor  of  the  femur.  In  our  opinion, 
its  mode  of  attachment  will  not  permit  it  to  rotate  this  bone  either  inwards 
or  outwards — at  least  in  Solipeds. 

7.  External  Obturator.    (Fig.  90,  13.) 
Synonym. — Subpubio-trochanterius  externus — Girard. 

Form  —  Structure  —  Situation  —  Direction.  —  A  short,  thick  muscle, 
flattened  on  both  sides,  triangular,  fasciculated,  fleshy  and  aponeurotic, 
very  delicate  in  textm-e,  and  placed  almost  horizontally  beneath  the  pelvis, 
at  the  margin  of  the  oval  foramen,  which  it  api)ears  destined  to  close,  and 
from  which  it  derives  its  name  of  obturator. 

Attachments. — 1.  To  the  inferior  surface  of  the  pubis  and  ischium,  by 
the  internal  extremities  of  its  fasciculi  — fi.ved  insertion ;  2.  To  the 
trochanterian  fossa,  by  the  external  extremities  of  these  fasciculi — movable 
insertion. 

Relations. — Its  inferior  face  is  covered  by  the  pectineus,  the  two 
adductors  of  the  thigh,  and  the  square  crural ;  the  superior  covers  the 
capsule  of  the  hip-joint,  and  is  related  to  the  internal  obturator. 

Action. — An  adductor  and  rotator  outwards  of  the  thigh. 

8.  Internal  Obturator.    (Figs.  90  ;  131.) 
Synonym. — Subpubio-troclianterius  internus — Girard. 

Situation. — This  muscle  is  situated  in  the  pelvic  cavity,  above  the  oval 
foramen,  and  is,  consequently,  opposite  the  external  obturator. 

Form — Structure — Attacliments. —  It  is  formed  of  two  portions.  One  is 
very  thin,  and  composed  of  slightly  tendinous  divergent  muscular  fasciculi, 
which  arise  from  around  the  oval  foramen,  are  directed  outwards,  and 
terminate  in  a  tendon  belonging  to  the  other  portion.  The  latter,  elongated 
and  penniform,  is  situated  in  the  pelvis,  and  extends  from  the  anterior  angle 


MUSCLES  OF  THE  POSTEBIOR  LIMBS. 


i03 


of  the  sacrum  to  tlie  inferior  extremity  of  tlie  femur,  following  the  direction 
of  the  ischiatic  border  of  the  ilium,  into  wliich  it  is  inserted.  The  tendon 
to  which  it  owes  its  penuiform  shape  is  inflected  outwards,  behind  the  suj^ra- 
cotyloid  crest  or  sciatic  ridge,  joins  the  gemelli,  and  terminates  in  the 
bottom  of  the  trochauterian  fossa. 

Melations. — lu  its  iutrapelvic  portion,  this  muscle  responds:  outwards 

Fi?.  131. 


COCCYGEAL   AND   DEEP   MUSCLES   SURROCXDING   THE   COXO-FEMORAL   ARTICULATION. 

1,  Superior  Sacro-coccygeus  ;  2,  Lateral  sacro-coccygeus ;  3,  Inferior  sacro-coccygeus ; 
4,  Ischio-coccygeus ;  5,  Small  gluteus;  6,  Anterior  gracilis;  7,  Tendon  of  the 
internal  obturator ;  8,  8,  Gemelli  of  the  pelvis ;  9,  Accessory  fasciculus  of  the 
gemelli;  10,  Quadratus  cruralis;  11,  Sacro-sciatic  ligament;  12,  Great  sciatic 
notch ;  13,  Superior  ilio-sacral  ligament ;  14,  Inferior  ilio-sacral  ligament. 

and  downwards,  to  the  ilium,  pubis,  ischium,  and  external  obturator;  inwards 
and  upwards,  to  the  peritoneum,  important  vessels  and  nerves,  and  to  a 
fibrous  lamina  that  separates  it  from  the  bladder.  In  its  extra-pelvic 
portion,  it  is  in  relation  with :  behind,  the  middle  gluteal  muscle  and  the 
sciatic  nerves  :  in  front,  with  the  gemelli.  A  synovial  sheath  facilitates  the 
gliding  of  its  tendon  in  the  groove  in  which  it  turns. 

Action. — It  is  a  rotator  of  the  thigh  outwards,  and,  contrary  to  the 
opinion  of  the  majority  of  authors,  we  believe  it  to  produce  abduction  rather 
than  adduction,  if  at  any  time  its  position  allows  it  to  execute  either  of  these 
two  movements. 

9.  Gemelli  of  (lie  Pelvis  (Fig.  131,  8,  8,  9). 

Synonyms. — Ischio-trochanterius — Girard.    (Gemini — PercivaU.    Bifemoro-calcaneus 
—Leyh.) 

The  two  small  muscles  which  receive  this  name  are  far  from  presenting 
the  same  disposition  in  every  subject ;  but  we  will  describe  that  which 
appears  to  be  the  most  fi'equent.  Two  little  elongated  muscular  fasciculi 
are  usually  found,  one  above,  the  other  below  the  tendon  common  to  the  two 
portions  of  the  internal  obturator.  These  two  fasciculi  (Fig.  131,  8,  8), 
arise  from  the  external  border  of  the  ischium,  follow  the  direction  of  the 
above-mentioned  t^don,  and  are  inserted  into  it  by  the  external  extremities 
of  their  fibres,  exactly  representing  the  gemelli  of  Man.  But  there  is  also 
22 


294 


THE  MUSCLES. 


a  tlaird  (Fig.  131,  9),  wide,  flat,  and  often  very  voluminous,  situated  between 
the  preceding  and  the  external  obtui-ator ;  it  is  attached,  by  its  inner  border, 
to  the  external  border  of  the  ischium,  contracting  intimate  adhesions  with  the 
other  two  and  with  the  tendon  of  the  internal  obturator,  and  becoming 
inserted  by  the  whole  extent  of  its  external  border  into  the  digital  fossa. 

Belations. — The  gemelli  respond  posteriorly,  to  the  sciatic  nerves ; 
anteriorly,  to  the  capsule  of  the  hip-joint  and  the  external  obturator, 
through  the  medium  of  an  adipose  cushion. 

Action. — Like  the  jireceding  muscle,  these  rotate  the  thigh  outwards, 
and  perhaps  tend  to  produce  the  abduction  of  this  ray. 


DIPFEEENTIAL   CHAKACTEES   OF  THE   MUSCLES   OF   THE   THIGH   IN   OTHEB  THAN   SOLIPED 

ANIMALS. 

A.  Anterior  Crural  Region. 

In  the  Ox,  Sheep,  and  Goaf,  the  muscle  of  the  fascia  laia  is  much  wider  than  in 
Solipeds.  In  the  Dorj  and  Cat,  this  muscle  oifers  in  front  a  supernumerary  fasciculus — 
a  long  thick  band,  confounded  inwardly  with  tie  long  abductor  of  the  leg,  and  extending 
vertically  from  the  external  angle  of  the  ilium  to  the  patella,  into  which  it  is  inserted  by 
a  short  aponeurosis. 

Tlie  anterior  rectus  of  the  thifjh  in  the  Dog  and  Sheep  has  only  one  originating  brnnch. 

The  anterior  gracilis,  the  very  small  muscular  fasciculus,  is  only  present  in  Solipeds 
and  Carnivores. 

B.  Posterior  Crural  Region. 

EuMiNANTS. — In  the  Ox,  Sheep,  and  Goat,  the  two  portions  of  the  long  vastus  are 
"but  little  distinct  from  each  other,  and  the  anterior  is  reinforced  superiorly  by  (he 
superficial  gluteus,  which,  with  the  long  vastus,  forms  but  one  remarkably  developed 
^muscle. 


Fig.  132. 


The  internal  face  of  this  muscle  has 
no  point  of  attachment  on  the  femur ;  it 
glides  behind  the  trociianfer  by  means  of 
a  vast  mucous  bursa,  which  is  often  the 
Stat  of  pathological  alterations — ^synovial 
tumours  which  constitute  the  swellings  or 
gout  of  the  larger  Kuminunts.  Another 
synovial  bursa,  liable  to  the  same 
maladies,  covers  the  imtellar  tendon  of  the 
muscle  on  its  passage  over  the  external 
condyle  of  the  ft-mur,  and  facilitates  its 
gliding  oil  that  buny  eminence.  Before 
joining  the  external  patellar  ligament, 
this  tendon  shows  a  very  thick,  fibro- 
cartilaginous enlargement,  and  receives 
some  of  the  fibres  of  the  external  vastus. 
Another  arrangement  in  tliis  mu>cle, 
which  it  is  essential  to  recognise  in  a 
surgical  point  of  view,  is  the  union  of  the 
anterior  border  of  the  long  vastus  of  the 
Ox  with  the  fascia  lata,  whose  two 
lamelhe  comprise  th'it  muscle  between 
them,  and  closely  adhere  to  each  of  its 
iaces.  It  very  frequently  happens  that 
in  emaciated  beasts,  this  fascia  is  ruptured 
at  the  trochanter,  and  the  latter,  instead 
of  gliding  on  the  inner  face  of  the  long 
vastus,  slips  before  its  anterior  boriler  to 
pass  through  the  solution  of  continuity, 
where  it  is  fixed  so  firmly  that  it  is  some- 
1,  Middle  gluteal;  2,  2,  Long  vastus;  anterior  times  necessary  to  cut  across  the  fibres  of 
portion;  3,  Ditto,  posterior  portion;  4,  Semi-  tlie  long  vastus  in  older  to  give  the  limb 
tendinosus  i  5,  Muscle  of  the  fascia  lata.  liberty  of  movement. 


SUPERFICIAL   MUSCLES  OF   THE   CROUP   AND 
THIGH    IN   THE   COW. 


MUSCLES  OF  THE  POSTERIOR  LIMES.  295 

The  scmUendinosus  has  no  sacral  prolongation ;  it  arises  only  from  the  ischium. 

Tlie  semimembrandsns  is  divided,  inferiorly,  into  two  branches :  one,  very  thick, 
pnsses  to  the  femur;  the  other,  much  smaller,  terminates  by  a  tendon  which  is  in- 
sinuated beneath  the  internal  lateral  ligament  of  the  ftmoro-tibial  articulation,  to  gain 
the  superior  extrenuty  of  the  tibia. 

CL'iRNivoEA. — lu  th(  si-  animals  it  is  somewhat  difficult  to  isolate  the  two  portions  of 
the  long  vasltis  from  each  other.  The  anterior  only  proceeds  from  the  ischium.  Infe- 
riorly, they  terminate  in  common  by  an  aponeurosis  which  passes  to  the  tibial  crest  and 
the  1  sternal  patellar  ligament. 

The  seniiteiuiiuusus  and  semimembranosus  comport  themselves  as  in  the  smaller 
Rumiuants. 

C.  Internal  Crural  Region. 

RrMiNANTS. — The  long  adductor  of  the  leg  in  the  Ox  and  Sheep  is  traversed,  near  its 
origin,  by  the  femoral  artery.  The  pectineus  of  the  Ox,  single  at  its  upper  extremity,  is 
divided  into  two  branches  at  its  inferior  extremity.  One  of  these  brunches,  tliin  and 
pale,  is  prolonged  to  near  the  internal  condyle  of  the  femur,  while  the  principal  stops,  as 
in  the  Horse,  on  tlie  posterior  face  of  the  bone. 

The  siiiull  adductor  of  the  thigh  is  scarcely  distinct  from  the  great  adductor.  The 
latttr  is  undivided  at  its  inferior  extremity,  which  stops  at  the  posterior  face  of  the 
femur  without  going  to  the  inner  condyle  of  that  bone. 

Tlie  internal  obturator  has  no  upper  portion ;  it  is  united  to  the  external  obturator  in 
passing  through  the  oval  foiamen. 

Pig. — In  this  animal,  the  internal  crural  muscles  offer  somewhat  the  same  disposition 
as  in  the  Ox. 

Cahnivora. — In  the  Dog  and  Cat,  the  long  adductor  of  the  leg  arises  from  the 
external  an^le  of  the  ilium,  and  by  its  muscular  portion  is  prolonged  to  the  inner  face  of 
the  tibia.  The  short  adductor  is  much  thinner  and  narrower  than  in  the  other  animals. 
The  small  adductor  of  the  thigh  is  a  little,  dist  nctly-isolated,  muscle,  which  begins  on  the 
inferior  face  of  the  pubis,  and  terminates  at  the  posterior  face  of  the  femur,  below  the 
square  crural.  The  great  adductor  is,  on  the  contrary,  a  wide,  tliick,  undivided  muscle, 
attached  to  nearly  the  whole  extent  of  the  linea  aspera  of  the  femur. 

There  is  nothing  particular  to  note  wilh  regard  to  the  square  crural  and  the 
obturators  ;  the  gemelli  of  the  pelvis  are  always  composed  of  two  small,  distinctly-isolated, 
fasciculi,  which  comport  themselves  as  in  Man. 

COMrAKISON   OF   THE   MUSCLES   OF   MAN's   THIGH   WITH   THOSE   OF   THE   THIGH   OF   ANIMALS. 

A.  Anterior  Muscles. 

The  anterior  gracilis  is  not  found  in  Man ;  nevertheless,  there  are  reckoned  three 
anterior  muscles  of  the  thigh,  as  the  sartoiius,  which  corresponds  to  the  long  adductor 
of  the  It  g  of  animals,  is  includeil  in  this  region. 

The  sartorius  is  a  very  long  muscle,  whose  width  at  most  is  about  two  fingers'  breadth. 
It  is  attached  above,  not  to  the  lumbo-iliao  aponeurosis,  but  to  the  anteriur  and  superior 
iliac  spine  :  it  is  afterwards  directed  downwanls  and  inwards,  to  pa-s  round  the  internal 
condyle  of  the  femur,  and  terminate  by  an  expanding  tendon  at  the  crest  of  the  tibia. 

The  trusor  of  the  fascia  labi  {tensor  vagina!  femoris)  shows  the  same  general  dis- 
position observed  in  animals.  It  is  the  same  with  the  femoral  tricejis.  The  anterior 
rectus  arises  by  two  tendinous  l^ranches  :  one  is  detached  from  the  auterior  and  iuferior 
iliac  spine ;  the  other  from  the  brim  of  the  cotyloid  cavity. 

B.  Muscles  of  the  Posterior  Region. 

These  are  three  in  number :  the  femoral  or  crural  biceps,  semitendinosus,  and 
semimembranosus. 

The  femoral  biceps  is  represented  in  Solipeds  by  the  posterior  portion  of  the  long 
vastus.  It  is  an  elongated  muscle  arising  by  two  heads:  the  long  bead  comes  from  the 
iscbiatic  tuberosity  ;  the  shortest  from  the  middle  of  the  linea  aspera.  After  their 
union,  these  two  heads  give  rise  to  a  tendon  which  is  fixed  into  the  head  of  the  fibula, 
and  sends  an  expansion  over  the  tibi.d  aponeurosis. 

The  semitendinosus  arises  in  common  with  the  long  head  of  the  biceps ;  its  inferior 
tendon  is  reflected  beneath  the  internal  tuberosity  of  the  tibia,  to  be  fixed  into  the  crest 


296 


THE  MUSCLES. 


of  that  bone.    This  tendon,  with  that  of  the  sartorius,  forms  the  aponeurotic  expansion 
called  the  goose's  foot. 

The  semimembranosus  is  voluminous  in  its  lower  portion,  and  arises,  like  the  otlier 
two,  from  tlie  tuberosity  of  the  ischium;  its  fibres  pass  to  a  tendon  which,  on  reaching 
tlie  inner  side  of  the  knee,  teruiiuates  in  the  tluee  pieces  composing  that  articulation  (see 
fig.  134). 

Fis.  133.  Fig.  134, 


MUSCLES  OF   THE   ANTERIOR   FEMORAL 
REGION    IN   MAN. 

1,  Crest  of  the  ilium ;  2,  Its  antero-superior 
spinous  process ;  3,  Gluteus  medius ;  4, 
Tensor  vaginee  femoris ;  5,  Sartorius;  6, 
Rectus ;  7,  Vastus  externus ;  8,  Vastus 
internus;  9,  Patella;  10,  lliacus  internus; 
11,  Psoas  magnus ;  12,  Pectineus;  13, 
Adductor  longus;  14,  Portion  of  adductor 
magnus ;  1 5,  Gracilis. 


MUSCLES   OF   THE    POSTERIOR    FEMORAL   AND 
GLUTEAL   REGION    IN    MAN. 

1,  Gluteus  medius  ;  2,  Gluteus  maximus  ;  3, 
Vastus  externus,  covered  by  fascia  lata ; 
4,  Long  head  of  biceps ;  5,  Short  head  ;  6, 
Semitendinosus ;  7,  7,  Semimembrano- 
sus ;  8,  Gracilis ;  9,  Portion  of  inner 
border  of  adductor  magnus ;  10,  Edge  of 
sartorius  ;  11,  Popliteal  space  ;  12,  Gastroc- 
nemius, with  its  two  heads. 


C.  Muscles  of  the  Internal  Region. 

In  books  on  liuman  anatomy,  these  muscles  are  sometimes  designated,  from  their 
action,  by  the  generic  name  of  adductors.  They  comprise :  the  internal  rectus,  pectineus, 
first  or  middle  adductor,  second  or  small  adductor,  and  third  or  great  adductor.  Tiie 
square  crural,  the  obturators,  and  the  gemelli  are  described  among  the  posterior  muscles 
of  the  pelvis.     They  will,  however,  be  briefly  alluded  to  liere. 

The  internal  rectus  corresponds  to  the  short  adductor  of  the  leg  of  animals.  It  is 
a  thin  muscle,  bordering  the  inner  side  of  the  thigh.  It  is  attached,  above,  to  the 
symphysis  pubis ;  below,  to  the  crest  of  the  tibia,  in  common  with  tlie  sartorius  tendon. 


MUSCLES  OF  TEE  POSTERIOB  LIMBS.  297 

The  pectineus  repeats  the  anterior  branch  of  the  pectineus  of  the  Horse.  It  is  inserted, 
below,  into  the  iiitenuil  bifurcation  of  the  linea  aspera  of  the  femur. 

The  jirst  adductor  corresponds  to  the  posterior  branch  of  the  pectineus  of  Solipeds. 
It  is  lepresenteil  by  a  voluminous  muscular  mass,  which  arises  from  the  spine  of  the 
I)ubis  and  terminates  on  the  middle  third  of  thf  linea  aspera. 

The  second  or  small  adductor  corresponds  to  the  muscle  of  the  same  name  in  animals. 
It  is  insert  d  into  the  same  points  as  the  preceding. 

The  third  or  great  ndductur  is  attahid.  above,  to  the  ischiatic  tuberosity  and  to  the 
whole  of  the  lower  branch  of  the  iscliium  by  aponeurotic  fibres.  It  afterwards  divides 
into  two  branches:  the  external  bra'ich.  entirely  muscular,  is  fixed  into  the  entire 
interspace  of  the  linea  aspera  ;  the  internal  branch  gives  rise  to  a  tendon  which  goes  to 
the  inner  condyle  of  the  femur.  Between  these  two  branches  is  found,  as  in  the  Horse, 
the  ring  of  the  adductors,  in  which  pass  the  large  vessels  of  the  thigh. 

Tiie  square  crural  of  Man  is  nearly  horizontal,  as  it  is  attached,  inwardly,  to  the 
external  border  of  the  ischium,  and  outwardly,  between  the  great  and  small  trochanters. 

The  internal  obturator  and  gemelli  resemble  those  of  the  Dog. 

MUSCLES   OF    THE    LEG. 

These  muscles,  nine  in  number,  are  grouped  around  the  two  principal 
boues  of  the  leg.  so  as  almost  to  completely  envelop  them,  leaving  only  the 
internal  face  of  the  tibia  uncovered.  Like  those  of  the  fore-arm,  they  form 
two  jmrticular  regions:  an  anterior q.\i^  a  posterior ;  and  they  are  sheathed  in 
common  by  the  tibial  aponeurosis,  a  very  solid  fibrous  covering  which  in  every 
respect  corresponds  to  the  autibrachial  aponeurosis. 

TIBIAL    APONEUROSIS. 

This  aponeurosis  is  formed  of  several  superposed  layers  which  are 
intimately  united,  and  receives,  superiorly,  the  insertion  of  the  long  vastus, 
the  semitendiuosus,  and  the  short  adductor  of  the  leg,  which  may  be  con- 
sidered as  its  tensor  muscles. 

It  is  continued,  inferiorly,  over  the  tarsus  and  the  metatarsal  region,  in 
becoming  singularly  attenuated,  and  in  covering  the  fibrous  bauds  which 
bind  and  retain  the  anterior  tibial  muscles  in  the  bend  of  the  hock.  Its 
external  surface  is  separated  from  the  skin  by  a  very  thin  cellulo-fibrous 
expansion  ;  its  internal  face  furnishes  special  and  very  firm  sheaths  around 
the  majority  of  the  tibial  muscles. 

The  tibial  aponeurosis  is  attached  to  the  internal  surface  and  crest  of  the 
tibia,  as  well  as  to  the  summit  of  the  calcis.  The  latter  attachment  takes  place 
by  a  thick  fibrous  band,  whose  singular  and  complicated  disposition  has  not 
yet  been  exactly  described.  It  is  situated  in  front  of  the  tendon  of  the 
hock,  or  between  that  tendon  and  the  deep  layer  of  the  posterior  tibial 
muscles.  By  its  borders,  it  is  continuous  with  the  tibial  aponeurosis  or 
fascia.  Superiorly,  it  adheres  most  intimately  to  the  perforatus  tendon,  near 
the  point  where  the  latter  originates  ;  there  it  sends  off  a  thick  fasciculus  which 
descends  to  the  gastrocnemius  tendon.  Below  this,  it  appears  to  divide  into 
two  branches,  an  external  and  internal,  which  are  united  to  the  calcanean  cap 
of  the  perforatus  tendon,  and  are  attached  to  the  sides  of  the  calcis  in  such  a 
manner,  that  near  its  insertion  the  gastrocnemius  tendon  is  found  to  be 
enveloped  by  a  complete  fibrous  sheath,  formed  partly  by  the  perforatus 
tendon  and  partly  by  the  band  just  described.  This  latter,  therefore,  con- 
stitutes a  strengthening  apjiarattis  for  the  tendon  of  the  hock :  a  structure 
noticed  by  Girard,  who  made  it  a  branch  of  insertion  of  the  semitendiuosus  ; 
and  not  without  reason,  perhaps,  because  it  arises  fi'om  the  tibial  aponeurosis, 
which,  in  part  at  least,  is  itself  derived  from  the  semitendinosus  muscle. 

Preparation  of  the  Muscles  of  the  Leg. — Separate  the  limb  fi-om  the  trunk  by  sawing 


298  TEE  MUSCLES. 

through  the  femur  at  its  middle.  Dissect  the  insertions  of  the  long  vastus,  the  short 
adductor  of  ihe  leg,  and  the  seniitendinosus,  to  observe  the  continuity  of  tliese  muscles 
with  the  tibial  aponeurosis ;  study  the  int-ertions  of  this  aponeurosis,  particularly  that 
wliich  it  has  on  the  summit  of  the  calcis.  To  expose  the  muscles,  remove  their 
aponeurotic  envelope,  leaving,  however,  the  band  it  forms  in  front  of  the  tendon  of  the 
hock,  as  well  as  the  bands  which  retain  the  tendons.  Remove  the  hoof  in  the  manner 
already  indicated  for  the  anterior  extremity,  and,  finally,  separate  the  muscles  from  one 
another — an  operation  so  very  simple  as  not  to  reqiure  any  special  directions. 

A.  Anterior  Tibial  JRegion. 

This  is  composed  of  three  muscles :  the  flexor  of  the  metatarsus,  the 
anterior  extensor,  and  the  lateral  extensor  of  the  phalanges.  The  first  is 
deep-seated,  the  other  two  are  superficial. 

1.  Anterior  Extensor  of  the  Phalanges.     (Fig.  135,  20.) 

Synonyms. — Femoro-preph:ilan'j:eus — Girard.  The  extensor  longus  digitorum  pedis 
of  Man.     {Extensor  pedis — Fercivall. ) 

Situation — Direction^Extent. — This  muscle,  situated  in  front  of  the 
leg  and  foot,  follows  the  direction  of  these  two  rays  for  their  whole  extent. 

Form — Structure. — It  is  formed  of  a  muscular  body  and  a  tendon.  The 
first  is  fusiform,  depressed  from  before  to  behind,  aponeurotic  at  its  superficies 
in  its  superior  moiety,  and  tendinous  internally  in  its  inferior  moiety.  The 
tendon,  at  first  round,  then  flat,  commences  a  little  above  the  inferior  fourth 
of  the  tibia,  and  reaches  the  anterior  face  of  the  princiiial  metatarsus,  where 
it  receives  the  pedal  (extensor  brevis  digitorum)  muscle,  the  tendon  of  the 
lateral  extensor,  and  a  funicular  jirolongation  of  the  tibial  aponeurosis.  It 
afterwards  descends  on  the  fetlock,  where  it  comports  itself  exactly  as  the 
corresjjonding  tendon  in  the  anterior  extremity.  {See  the  anterior  extensor 
of  the  phalanges  in  the  fore-limb,  page  2G2.) 

Attachments. — Above,  in  the  digital  fossa  placed  between  the  trochlea  and 
external  condyle  of  the  femui",  through  the  medium  of  the  tendinous  portion 
of  the  flexor  of  the  metatarsus— ^j;erf  insertion.  Below,  on  the  cajjsular  liga- 
ment of  the  metatarso-j)halangeal  articulation,  the  anterior  face  of  the  two 
first  phalanges,  and  the  pyramidal  eminence  of  the  os  pedis. 

Relations. — The  muscular  portion  responds :  outwardly,  with  the  tibial 
aponeurosis ;  inwardly,  to  the  flexor  of  the  metatarsus ;  posteriorly,  to  the 
lateral  extensor  of  the  phalanges.  The  tendon  successively  covers :  the 
anterior  aspect  of  the  tibia,  the  anterior  capsular  ligament  of  the  tarsus,  the 
pedal  muscle,  the  anterior  face  of  the  principal  metatarsal,  the  articulation  of 
the  fetlock,  and  the  two  first  phalanges.  It  is  covered  by  the  tibial  aponeu- 
rosis, and  by  three  annular  fibrous  bands  destined  to  maintain  the  tendon  in 
the  bend  of  the  hock.  One  of  these  bands,  the  superior,  is  fixed  by  its  ex- 
tremities to  the  tibia,  a  little  above  the  tibio-tarsal  articulation  ;  it  is  common 
to  the  muscle  we  are  describing,  and  to  the  flexor  of  the  metatarsus.  The 
middle  band,  attached  to  the  cuboid  branch  of  the  latter  muscle  and  the 
inferior  extremity  of  the  calcis,  is  exclusively  intended  for  the  anterior  ex- 
tensor of  the  phalanges.  The  inferior  maintains  the  two  extensors  against 
the  superior  extremity  of  the  principal  metatarsal. 

Action. — This  muscle  extends  the  digit  and  flexes  the  entire  foot. 

2.  Lateral  Extensor  of  the  Phalanges.     (Fig.  135,  28.) 

Synonyms.—  Peroneo-prephalangeus — Girard.  The  peroneus  brevis  of  Man.  (Peroneus 
Fercivall.     Tihio-prephulan(jeus~Leyh.) 

Situation — Form — Structure — Extent — Direction. — This  muscle,  situated 


MUSCLES  OF  THE  POSTERIOR  LIMBS. 


299 


on  the  external  side  of  the  leg,  between  the  preceding  and  the  deep  flexor  of 
the  phalanges,  is  composed  of  a  muscular  portion  and  a  tendon.     The  first, 


Fi2.  135. 


EXTERNAL   DEEP  MUSCLES   OF   EIGHT    I'dSTKRIOR   LIMB. 

1,  Crest  of  the  ilium  ;  2,  Inferior  saoro-sciatic  ligament ;  3,  Sacro-ischiatic  ligament ; 
4,  Obturator  ligament ;  5,  Tuberosity  of  the  ischium  ;  6,  Anterior  tuberosity  of 
the  ilium  ;  7,  Small  gluteus,  or  gluteus  internus ;  8,  Its  insertion  into  the  great 
trochanter,  9;  10,  Iliacus.  or  iliac  psoas;  11,  Vastus  externus ;  12,  Rectus;  13, 
Great  sciatic  nerve;  14,  Gracilis ;  15,  Sartorius  ;  16,  Patella;  17,  Lateral  liga- 
ment; 18,  Oblique  flexor  of  the  phalanges,  or  flexor  pedis  accessorius ;  19,  Pero- 
neus;  20,  Extensor  pedis  ;  21,  Solearis,  or  plantaris  ;  22,  Gastrocnemius  externus ; 
23,  Flexor  pedis  ;  24,  Tendon  of  oblique  flexor  of  the  phalanges ;  25,  Perforatus 
tendon ;  2G,  Lateral  ligament  of  gastrocnemius ;  27,  28,  Annular  ligament ;  29, 
Tendon  of  lateral  extensor  of  the  phalanges,  or  peroneus ;  30,  External  rudi- 
mentary metatarsal  bone. 

elongated,  prismatic,  and  slightly  penniform,  extends  in  the  direction  of  the 
leg,  from  the  superior  extremity  of  that  region  to  beyond  its  inferior  extre- 
mity. The  tendon  succeeds  the  lower  end  of  the  muscular  portion,  and 
traverses  the  groove  on  the  middle  of  the  infero-external  tuberosity  of  the 


300 


THE  MUSCLES. 


tibia,  passing  to  the  external  side  of  the  tarsus,  where  it  is  enclosed  in  a  very 
firm  sheath,  and  is  inflected  forwards  to  become  united  to  the  tendon  of  the 
anterior  extensor,  near  the  middle  of  the  metatarsal  region. 

Attachments. — The  lateral  extensor  is  attached,  by  the  superior  extremity 
of  its  muscular  fibres,  to  the  external  femoro-tibial  ligament,  to  the  whole 
extent  of  the  fibula,  and  to  the  fibrous  partition  which  separates  this  muscle 
from  the  perforans — origin.  It  terminates  in  the  tendon  of  the  anterior 
extensor. 

Belations. — Its  muscular  body  is  enveloped  in  a  special  containing 
aponeurosis,  which  separates  it,  in  front,  from  the  anterior  extensor,  and 
behind  from  the  perforans.  The  tendon  covers  the  tibia,  and  margins  the 
external  and  suj)erficial  ligament  of  the  tibio-tarsal  articulation  ;  which  liga- 
ment supplies  a  fibrous  ring  destined  for  the  formation  of  its  reflected  sheath. 
A  vaginal  synovial  membrane  facilitates  its  motion  in  the  interior  of  this 
sheath. 

Action. — It  acts  like  the  preceding. 

3.  Flexor  of  the  Metatarsus.     (Fig.  136.) 

Synonyms. — Tibid-prcmetutarsus — Girard.      Its    muscular    portion    represents    the 
tibialis  anticus  of  anthropotoiiiiots.     {Flexor  Metatarsi — Fercivall.) 

This  muscle  is  situated  beneath  the  anterior  extensor  of  the  phalanges,  on 
the  external  surface  of  the  tibia,  and  is  composed  of  two  distinct  portions  :  one 
muscular,  the  other  aponeurotic,  not  united  from  end  to 
end,  but  placed  parallel  one  before  the  other. 

A.  Tendinous  Portion  (Fig.  136, 1). — Course — Attach- 
ments.— This  is  a  strong,  pearly-white  cord,  comprised 
between  the  muscular  port io7i  and  the  anterior  extensor  of 
the  phalanges.  It  commences  at  the  inferior  extremity  of 
the  femur,  in  the  fossa  excavated  between  the  trochlea 
and  the  external  condyle ;  it  afterwards  passes  through  the 
superior  groove  of  the  tibia,  where  it  is  enveloped  by 
a  prolongation  from  one  of  the  synovial  membranes  of 
the  femoro-tibial  articulation,  giving  origin,  below  this 
groove,  to  the  muscular  fibres  of  the  anterior  extensor 
of  the  phalanges.  Lower,  it  receives  some  of  the  fasciculi 
from  the  muscular  portion,  to  which  it  sends  in  exchange 
several  aponeurotic  layers;  it  passes  under  the  superior 
annular  band  in  front  of  the  hock,  in  company  with  the 
anterior  extensor,  and  reaches  the  level  of  the  trochlea  of 
the  astragalus,  where  it  is  perforated  to  form  a  ring  for 
the  passage  of  the  inferior  extremity  of  the  muscular 
portion.  It  finally  terminates  in  two  branches  :  a  large 
one,  inserted  in  front  of  the  superior  extremity  of  the 
principal  metatarsus  (Fig.  136,  4) ;  the  other,  narrower, 
deviates  outwards  to  reach  the  anterior  surface  of  the 
cuboid  bone  (Fig.  136,  3). 

1,  Tendinous  portion;  2,  Its    attachment   to  the    femur;    3,  Its 

cuboid  branch;  4,  Its  metatarsal  branch;  5,  Muscular  portion; 

6,  Its  succeeding  tendon  passing  through  the  ring  of  the  tendi- 

FLEXOR  MUSCLE  OF      jj^yg  portion;  7,  Cuneiform  portion  of  this  tendon;  8,  Its  meta- 

THE  METATARSUS.        tarsal    branch ;    9,    Anterior  extensor  of  the    phalanges  drawn 

outwards  by  a  hook. — A,  Lateral  extensor ;  B,  Tibial  insertion  of  the  middle  patellar 

ligament ;  C,  Femoral  trochlea. 


MUSCLES  OF  TEE  POSTERIOR  LIMBS.  301 

"Relations. — In  front,  with  tlie  anterior  extensor  of  tlie  pTialangcs; 
behind,  with  the  muscular  portion,  and  the  anterior  caj)sular  ligament  of 
the  tarsus. 

Action. — Tliis  tendon  enjoys  the  curious  property  of  bending  the  hock 
by  an  action  altogether  mechanical,  whenever  flexion  of  the  superior  bones 
of  the  limb  takes  place.  It  is,  therefore,  a  conducting  cord,  whose  office  it 
is  to  regulate  the  movements  of  flexion  in  the  hock,  and  conform  them  to 
those  taking  place  in  the  other  joints,  without  requiring  the  intervention  of 
an  active  agency  for  the  execution  of  these  movements. 

Another  function  has  also  been  attributed  to  it :  that  of  passively  opposing 
the  flexion  of  the  femur  on  the  tibia  while  the  animal  is  standing,  and.  in 
this  way  serving  as  an  adjunct  to  the  muscular  powers  which  support  the 
weight  of  the  body.  But,  in  our  opinion,  this  is  incorrect ;  as  in  order  that 
it  may  perform  this  task,  it  would  be  necessary  for  the  foot  to  be  maintained 
in  a  fixed  position  by  the  contraction  of  its  extensor  muscles.  But  these 
muscles  are  really  the  gastrocnemii,  which  have  their  origin  behind  the 
femur,  and  which  undoubtedly  tend  to  flex  that  bone  on  the  tibia — that  is,  to 
determine  the  movement  it  is  supposed  to  prevent.  And  exjieriment  clearly 
shows  that  we  are  justified  in  this  opinion  ;  for  division  of  this  tendinous  cord 
in  the  living  animal  does  not  interfere  in  the  slightest  degree  with  its 
natural  attitude,  either  when  standing  at  liberty  or  when  forced  to  stand. ^ 

B.  Muscular  Portion. — Situation — Form — Structure. — Situated  between 
the  tendinous  cord  and  the  tibia,  this  portion  is  elongated  from  above  to 
below,  very  wide  at  its  superior  part  and  narrow  inferiorly,  where  it  termi- 
nates in  a  bifid  tendon. 

Attachments. — It  originates,  by  the  upper  extremity  of  its  muscular  fibres, 
from  the  tibia,  below  and  on  the  sides  of  the  groove  through  wliich  the 
tendinous  cord  passes ;  its  most  superficial  fibres  are  even  attached  to  the 
aponeurotic  sheath  which  envelops  the  lateral  extensor.  Its  terminal  tendon 
(Fig.  136,  6)  traverses  the  annular  ligament  which  the  tendinous  portion 
forms  at  its  inferior  extremity,  and  becomes  inserted,  by  one  of  its  branches, 

'  J.  F  Meckel  rightly  considers  this  tendinous  cord,  not  as  a  portion  of  tlie  anterior 
tibial,  but  as  a  dependency  of  the  extensor  longus  digitoruiu.  It  would  be  wrong, 
however,  to  describe  it  apart  from  the  anterior  tibial,  properly  so-called — that  is,  the 
muscular  portion  of  our  flexor  of  the  metatarsus,  the  tsvo  being,  in  their  action, 
essentially  one. 

.  Is  there  anything  in  the  human  species  analogous  to  this  fibrous  cord  ?  After  mucli 
liesitation,  we  answer  in  the  affirmative,  and  give  it  as  our  opinion  that  this  tendon  repre- 
sents the  anterior  peroneus  {ixroneus  tertiits)  in  Man.  These  are  our  reasons  for  making 
this  assertion,  hazardous  as  it  certainly  is  at  first  sight :  In  Man.  Ihe  peroneus  tertius 
cannot  always  be  easily  distinguished  from  the  extensor  longus  digitorum ;  so  that  these 
two  muscles  may  be  regarded  as  a  single  one  until  reaching  the  instep,  where  it  ex- 
tends to  the  plialanges  of  tlie  toes  on  the  one  part,  and  the  metatarsus  on  the  other. 
Precisely  tlie  same  arrangement  is  found  in  Solipeds  ;  the  single  muscle  divides  into  two 
fasciculi,  one  for  the  digital  region  [anterior  extensor  of  tlie  phalanges),  the  other  to  the 
metatarsal  region  (tendinous  cord  of  our  flexor  metatarsi).  This  tendinous  cord,  then, 
exactly  represents  the  fasciculus  of  the  long  common  extensor  ot  the  toes  (in  Man),  which 
goes  to  the  metatarsus,  and  is  designated  the  peroneus  tertius. 

But  to  this  it  may  be  said :  your  peroneus  tertius  in  the  Horse  has  no  relation  whatever 
to  the  peroneus,  and  does  not  this  prove  that  you  are  in  error?  No  ;  for  if  thi.-j  muscle 
is  attached  to  the  fibula  in  Man,  it  is  because  the  principal  muscle  on  which  it  depends 
is  inserted  there  itself.  But  as  the  anterior  extensor  of  the  phalanges  of  the  Horse — 
that  is,  the  common  extensor  of  the  toes — is  not  inserted  into  the  fibula,  and  has  no 
connection  with  it  in  any  way,  its  metatarsal  fasciculus,  or  rather  its  tendinous  cord  or 
peroneu-*  tertius,  ought  to  be  absolutely  in  the  same  condition.  We  repeat,  however, 
that  this  opinion  may  be,  perhaps,  a  little  hazardous ;  aud  we  give  it  with  reserve, 
though  we  have  some  rcasone  for  considering  it  to  be  correct. 


302  THE  MUSCLES. 

in  front  of  the  superior  extremity  of  tlie  princip.al  metatarsal  bone,  along 
with  the  analogous  branch  of  the  tendinous  division  (Fig.  136,  8).  The 
other  ramification  is  directed  to  the  inside  of  the  tarsus,  to  be  attached  to 
the  second  cuneiform  bone  (Fig.  136,  7). 

Belatmis. — In  front,  with  the  tendinous  portion  of  the  muscle  and  the 
anterior  extensor  of  the  phalanges ;  behind,  with  the  external  face  of  the 
tibia.  The  tendon,  after  traversing  the  annular  ligament  of  the  cord,  covers 
the  metatarsal  branch  of  the  latter,  and  is  in  turn  covered  by  the  anterior 
extensor. 

Action. — It  is  an  active  agent  in  flexing  the  foot  on  the  leg. 

B.  Posterior  Tibial  Region. 
This  region  comprises  six  muscles,  which  are  arranged  in  two  super- 
posed layers  behind  the  tibia.  The  superficial  layer  is  formed  by  the 
gastrocnemii,  salens,  and  the  superficial  flexor  of  the  phalanges.  The  deep 
layer  is  composed  of  the  popliteus,  the  deep  flexor,  and  the  oblique  flexor  of 
tlte  phalanges. 

^     1.  Gastrocnemii,  or  Gemelli  of  the  Tibia.     (Figs.  135,  22  ;  137,  20.) 
Synonyms.— Bifemoro-calcaneus —  Girard.    (  Gastrocnemius  externus — Percivall.') 

Situation — Compofiition — Extent. — The  gemelli  of  the  leg,  situated  behind 
the  femoro-tibial  articulation,  below  the  ischio-tibial  muscles,  constitute 
two  thick  fleshy  fasciculi  distinct  from  one  another  only  at  their  superior 
extremity,  being  confounded  for  the  remainder  of  their  extent,  and  continued 
inferiorly  by  a  single  tendon  which  extends  to  the  point  of  the  calcis. 

Porm — Structure. — Both  of  these  muscular  masses  are  flattened  on  both 
sides,  thick,  in  the  middle,  narrow  at  the  extremities,  and  intersected  by 
strong  tendinous  bands.  By  their  union  they  form  a  wide  channel,  open 
in  front,  which  embraces  the  femoro-tibial  articulation  and  the  muscles  of 
the  deep  layer. 

The  tendon,  at  first  fasciculated,  then  single  and  funicular,  receives  that  of 
the  soleus,  and  is  reinforced  by  a  fasciculus  from  the  fibrous  band  annexed  in 
front  to  the  tendon  of  the  perforatus  {see  the  description  of  the  tibial  aponeu- 
rosis, p.  297).  An  aponeurotic  lamina  which  covers  the  external  gemellus, 
is  continued  downwards,  partly  with  this  fibrous  band,  and  partly  with  the 
tendon  of  the  muscle  itself. 

Attachments. — The  external  gemellus  arises  on  the  femur,  from  thef 
rugged  lip  which  margins  in  front  the  supracondyloid  fossa ;  the  internal, 
from  the  collection  of  tubercles  which  constitutes  the  crest  of  the  same 
name.  The  terminal  tendon  of  the  two  bellies  is  fixed  on  the  summit  of 
the  calcis,  not  at  its  anterior  part,  but  posteriorly,  this  being  lubricated  by  a 
vesicular  synovial  membrane  forming  a  gliding  surface  on  which  the  tendon 
rests  during  extreme  flexion  of  the  foot  (Fig.  67,  1). 

Belations. — The  gemelli  respond  :  by  their  superficial  face,  to  the  three 
ischio-tibial  muscles,  and  the  tibial  aponeurosis ;  by  their  deep  face,  to 
the  perforatus,  which  contracts  intimate  adhesions  with  the  vastus 
externus,  to  the  posterior  ligament  of  the  femoro-tibial  articulation,  the 
popliteal  muscle  and  vessels,  the  great  sciatic  nerve,  and  the  oblique  and  deep 
flexor  muscles  of  the  phalanges.  The  tendon  lies  beside  that  of  the  per- 
foratus, which  is  twisted  around  and  completely  envelopes  it  at  its  inferior 
extremity,  in  common  with  the  fibrous  band  from  the  tibial  aponeurosis. 
The  two  tendons  form  what  is  usually  termed  the  tendon  of  the  hock,  or 
tendon  of  Achilles. 


MUSCLES  OF  THE  POSTERIOR  LIMBS. 


303 


Action. — The  gastrocnemii  extend  the  foot  upon  the  tibia.     They  act  as 
a  lover  of  the  first  order  when  the  limb  is  raised  from  the  ground,  and  as 


Fig.  137. 


MUSCLES   ON   INNER    ASPECT   OF   LEFT   POSTERIOR   LIMB. 

1,  Crest  of  the  ilium  ;  2,  Section  through  it ;  3,  Sacro-ischiatic  ligament;  4,  Pyri- 
formis  ;  5,  Posterior  portion  of  sacro-ischiatic  ligament ;  6,  Tuberosity  of  ischium  ; 
7,  Anterior  portion  of  ischium,  sawn  through  ;  8,  Pubis  ;  9,  Obturator  foramen; 
10,  External  iliac  artery  and  vein,  11 ;  12,  Obturator  artery  and  vein;  the  figures 
are  placed  on  the  internal  obturator  muscle;  13,  Long  adductor  of  the  leg,  or 
sartorius;  14,  Small  adductor  of  the  thigh,  or  adductor  brevis;  15,  Short 
adductor  of  the  leg,  or  gracilis  ;  16,  Ptcctus  of  the  thigh  ;  17,  Vastus  internus ; 
18,  Patella,  with  ^insertion  of  rectus;  19,  Upper  extremity  of  tibia;  20,  Gas- 
trocnemius; 21,  Popliteus;  22,  Oblique  flexor  of  the  phalanges,  or  flexor  pedis 
accessorius,  with  its  tendon,  34 ;  23,  Perforans  muscle,  with  its  tendon,  35 ;  24, 
Flexor  metatarsi ;  25,  Anterior  extensor  of  the  phalanges,  or  extensor  pedis ; 
26,  Annular  ligament ;  27,  Tendon  of  flexor  metatarsi,  and  its  cunean  branch,^ 
28 ;  29,  Tendon  of  superficial  flexor  or  internal  gastrocuemius ;  30,  Tendon  of 
gemelli  or  external  gastrocnemius  ;  31,  Os  calcis  ;  32,  Astragalus  ;  33,  Perloratus 
tendon  ;  34,  Tendon  of  oblique  flexor  joining  the  perforans  tendon,  35  ;  36,  Large 
-metatarsal  bone;  37,  Extensor  pedis  tendon;  38,  Terminal  knob  of  small  meta- 
tarsal bone. 


304  TEE  MUSCLES. 

one  of  the  second  order  when  the  hoof  is  placed  on  the  ground.  They 
maintain  the  tibio-tarsal  angle  while  the  animal  is  standing,  and  in  pro- 
gression give  to  the  hock  that  spring  which  carries  the  body  forward. 

2.  Soleus  (or  Solearis).     (Fig.  135,  21.) 

Sjpionyim. — Bourgelat  and  his  successors  have  erroneously  assimilated  it  to  the 
plantaris  of  Man.  In  regarding  this  little  muscle  as  the  soleus,  we  conform  to  the 
well-founded  opinion  of  Cuvier.  It  is  the  peroneo-calcaneus  of  Girard.  {Plantaris — 
Percivall.) 

Form — Situation. — This  is  a  thin,  long,  and  riband-shaped  rudimentary 
muscle,  situated  at  the  external  side  of  the  leg,  between  the  tibial  aponeu- 
rosis and  the  muscular  portion  of  the  perforans. 

Attachments. — It  is  fixed,  by  its  superior  extremity,  behind  the  supero- 
external  tuberosity  of  the  tibia  ;  and  terminates,  inferiorly,  by  a  small  tendon, 
which  joins  that  of  the  gastrocnemii. 

Action. — It  is  a  feeble  auxiliary  of  the  last-named  muscles. 

3.  Superficial  Flexor  of  the  Phalanges,  or  Perforatiis.    (Figs.  135,  25  ;  137,  30.) 

Synonyms. — Femoro-phalangeus  —  GtVard.  It  is  represented  in  Man  by  the  jdantaris 
and  ilexor  brevis  digitorum,  or  perforatus.  These  two,  in  the  majority  of  ni;immalia, 
are  united  from  end  to  end  to  form  a  single  muscle.  (The  gastrocnemius  infernus  of 
Percivall.j 

Form — Structure. — The  perforatus  of  the  posterior  limb  is  only  repre- 
sented, in  reality,  by  a  long  tendinous  cord,  that  is  somewhat  muscular, 
slightly  thickened,  and  fusiform  in  its  upper  fifth,  which  forms  the  body 
of  the  muscle. 

Origin — Direction  and  Relations — Termination. — It  originates,  by  its 
upper  extremity,  in  the  supercondyloid  fossa,  descends  between  the  two 
portions  of  the  gastrocnemii,  to  the  external  of  which  it  is  intimately  i*elated, 
on  the  posterior  face  of  the  femoro-tibial  articulation  and  the  three  posterior 
deep  tibial  muscles.  On  reaching  the  inferior  extremities  of  the  muscular 
bellies  of  the  gastrocnemii,  it  becomes  exclusively  tendinous,  and  is  directly 
united  to  the  fibrous  band  which  reinforces  the  tendon  of  the  hock.  It 
afterwards  disengages  itself  below  the  gastrocnemius,  and  is  placed  at  the 
internal  side  of  its  tendon,  then  on  its  posterior  surface,  and  in  this  position 
gains  the  summit  of  the  os  calcis.  There  it  becomes  widened  to  form 
a  fibrous  cap,  which  is  covered  by  a  large  vesicular  synovial  membrane ; 
it  is  moulded  to  the  posterior  region  of  this  bony  eminence,  which  it  com- 
pletely envelops  in  order  to  be  fixed  on  its  lateral  portions,  and  is  united 
to  the  calcanean  band  from  the  tibial  aponeurosis.  From  this  point  the 
tendon  of  the  perforatus  is  prolonged  behind  that  of  the  perforans  to 
the  posterior  face  of  the  second  phalanx,  where  it  terminates  in  exactly  the 
same  manner  as  the  analogous  muscle  of  the  anterior  limb. 

Action. — It  flexes  the  second  phalanx  on  the  first,  and  this  on  the  meta- 
carpus. It  also  concurs  in  the  extension  of  the  foot.  Its  principal  office, 
however,  is  that  of  a  mechanical  stay,  destined  to  sustain  the  equilibrium  of 
the  body  while  the  animal  is  in  a  standing  posture,  by  preventing  the 
diminution  of  the  angle  of  the  hock  and  that  of  the  fetlcck,  the  femur  being 
fixed  by  the  contraction  of  the  crural  triceps  and  the  gluteal  muscles. 

4.  Poplifeus.     (Fig.  137,  21.) 

S7jnonyms. — The  abductor  tibialis  of  Bourgelat,  and  femoro-tibialis  obliquus  of 
Girard. 


MUSCLES  OF  THE  POSTERIOR  LIMBS.  305 

Situation  —  Direction  —  Form  —  Structure. — Situated  beliincT  the  tibia, 
below  the  femoro-tibial  articuhition,  this  muscle  is  oblique  downwards  aud 
inwards,  short  and  triangular,  tendinous  at  its  supero-external  angle,  and 
formed,  for  the  remainder  of  its  extent,  of  divergent  fleshy  fibres,  the  longest 
of  which  are  the  most  inferior. 

Attachments. — 1.  In  the  lowest  of  the  two  fossaB  excavated  on  the  outside 
of  the  external  condyle  of  the  femur,  by  its  tendon — origin.  2.  On  the 
supero-posterior  triangular  surface  of  the  body  of  the  tibia,  by  the  inferior 
extremity  of  its  muscular  fibres — termination. 

Eelations. — Posteriorly,  with  the  gastrocnemii  and  the  perforatus.  In 
front,  with  the  posterior  ligament  of  the  femoro-tibial  articulation,  and  the 
popliteal  vessels.  Outwards,  with  the  oblique  and  deep  flexors  of  the 
phalanges.  Inwards,  with  the  semitendinosus  and  tibial  aponeurosis.  The 
tendon,  concealed  at  its  origin  beneath  the  external  femoro-tibial  ligament, 
glides,  by  its  deej)  face,  over  the  contour  of  the  external  semilunar  cartilage 
and  the  posterior  portion  of  the  external  facet  on  the  tibia. 

Action. — It  flexes  the  tibia,  and  gives  it  a  slight  rotatory  movement  out- 
■wai-ds. 

5.  Deejp  Flexor  of  the  Phalanges  or  Perforans.     (Figs.  135,  23  ;  137,  23.) 

Synonyms. — Tibio-phalangeus — Girard.  The  flexor  perfornns  and  flexor  longus 
poUicis  pedis  of  Man.     (^Flexor  pedis — Percimll.     Great  tihlo-phulangeus — Ltyh.') 

Extent — Situation — Direction — Composition, — Extending  from  the  supe- 
rior extremity  of  the  leg  to  the  third  phalanx,  and  situated  behind  the  tibia 
and  foot,  whose  direction  it  follows,  this  muscle  is  composed  of  a  muscular 
body  and  a  tendon. 

Form,  Structure,  and  Attachments  of  the  mvscular  portion. — This  is  thick 
and  prismatic,  and  incompletely  divided  into  two  portions — an  internal,^ 
and  an  external,^  which  is  the  most  voluminous.  It  is  attached :  1,  To  the 
posterior  face  of  the  tibia,  on  the  linear  imprints  which  occupy  the  inferior 
triangular  surface  ;  2,  To  the  supero-external  tuberosity  of  the  same  bone  ; 
3,  To  the  peroneus ;  4,  To  the  interosseous  ligament  uniting  that  bone  to 
the  tibia. 

Direction  and  Attachments  of  the  tendon. — The  tendon  commences  above 
the  inferior  extremity  of  the  tibia,  where  it  is  most  usually  double,  each 
muscular  portion  being  succeeded  by  a  tendinous  cord  whose  volume  is  in 
harmony  with  the  size  of  the  muscle  from  which  it  proceeds.  The  single 
tendon  resulting  from  the  union  of  these  two  primary  ones  enters  the  groove 
formed  by  the  inner  face  of  the  os  calcis,  where  it  is  retained  by  a  fibrous 
arch  which  transforms  this  channel  into  a  perfect  sheath,  designated  the 
tarsal  sheath;  it  glides  in  the  interior  of  this  canal  by  nieuns  of  a  very 
extensive  vaginal  synovial  membrane,  which  extends  upwards  on  the 
posterior  ligament  of  the  tibio-tarsal  articulation,  and  is  prolonged  inferiorly 
to  the  middle  third  of  the  metatarsal  region.  The  tendon  of  the  perforans 
afterwards  descends  vertically  behind  the  suspensory  ligament,  receiving 
from  it  a  strong  fibrous  band  analogous  to  that  of  the  fore-limb,  but  less 
voluminous ;  it  then  passes  through  the  annular  portion  of  the  perforatus, 
is  inflected  mth  that  muscle  over  the  great  sesamoid  groove,  glides  on  the 
posterior  articulating  surface  of  the  second  phalanx  and  that  on  the  small 
sesamoid  bone,  thinning  out  into  a  plantar  aponeurosis  which  is  provided  with 

'  The  tibialis  posticus  of  Man.  *  The  flexor  longus  pollicis  of  IMan. 


306  THE  MUSCLES. 

a  phalangeal  reinforcing  sheath,  and  finally  terminates  on  the  semilunar 
crest  of  the  os  pedis.  This  tendon,  therefore,  on  leaving  the  tarsus,  com- 
ports itself  exactly  like  that  of  the  anterior  limb. 

Relations. — Outwards,  with  the  lateral  extensor  of  the  phalanges,  the 
soleus,  and  the  tibial  aponeurosis.  Inwards,  with  this  aponeurosis  and  the 
oblique  flexor  Behind,  with  the  gastrocnemii,  the  j)erforatus,  and  the 
fibrous  band  of  tlie  tendon  of  the  hock.     In  front,  with  the  tibia. 

Action. — This  muscle  flexes  the  phalanges  on  one  another  and  on  the 
metatarsus.  It  may  also  extend  the  foot  in  pressing,  during  its  contraction, 
behind  the  tibio-tarsal  articulation.  In  addition  to  this,  its  tendon  acts, 
while  the  animal  is  standing,  as  a  mechanical  support  to  the  phalanges  and 
the  articular  angle  of  the  fetlock. 

6.  Ohlique  Flexor  of  ilie  Phalanges.     (Fig.  137,  22.) 

Synonyms. — Peroneo-phalangeus — Girard.  The  tibialis  posticus  of  Man.  (^Flexor 
pedis  accessorius — Percivall.    Small  tibio-phalangeus — Leyh.) 

Situation — Direction. — A  muscle  situated  behind  the  tibia,  between 
the  popliteus  and  the  perfurans,  in  a  direction  slightly  oblique  downwards 
and  inwards. 

Form — Structure. — It  is  composed  of  a  fleshy  fusiform  body,  intersected 
by  numerous  fibrous  bands,  and  provided  with  a  funicular  tendon  inferiorly. 

Attachments. — The  superior  extremity  is  fixed  behind  the  external 
tuberosity  of  the  tibia — origin.  The  tendon  is  united,  by  its  inferior 
extremity,  to  that  of  the  perforans  towards  the  upper  third  of  the  meta- 
tarsal region — termination. 

Relations. — The  muscular  portion  responds :  in  front,  to  the  perforans, 
the  popliteus,  and  the  posterior  tibial  artery;  behind,  to  the  gastrocnemii 
and  the  perforatus.  The  tendon,  at  first  lodged  in  a  muscular  channel 
in  the  perforans  and  covered  by  the  tibial  aponeurosis,  afterwards  enters  a 
tortuous  sheath  at  the  inner  side  of  the  tarsus,  and  which  is  formed  by  the 
groove  that  bends  behind  the  infero-internal  tuberosity  of  the  tibia. 

Action. — It  is  a  congener  of  the  deep  flexor. 

DIFFERENTIAL   CHARACTERS   OF  THE   MUSCLES   OF   THE   LEG   IN   OTHER   THAN   SOLIPED 

ANIMALS. 

A.  Anterior  Tibial  Region. 

RrMiNANTS. — Among  these  animals,  the  Ox  presents : 

1.  A  complex  muscle,  wliifh  is  represented  in  the  Horse  by  the  anterior  extensor  of 
the  phalanges,  and  the  tendinous  cord  of  the  flexor  metatarsi.  Single  at  its  superior 
extremity,  which  begins  by  a  tendcm  arising  from  the  digital  fossa  situated  between  the 
trochlea  and  the  external  condyle  of  the  femur  (Fig.  138,  1),  this  muscle  comprises  in 
its  middle  part  three  fleshy  divisions  which  are  terminated  inferiorly  by  tendons. 

One  (if  these  divisions,  situated  in  front  of,  and  within  the  other  two,  has  its  tendon 
prolonged  to  the  superior  extremity  of  the  principal  metatarsal  bone,  and  is  also  inserted 
into  the  cuneiform  bones.  It  is  a  flexor  of  the  metatarsal  region,  and  replaces  the 
tendinous  cord  which  performs  this  function  in  Solij^eds  ( Fig.  138,  2). 

The  second,  placed  without  the  preceding,  constitutes  a  common  extensor  of  the 
digits,  whose  tendon  comports  itself  exactly  like  that  of  the  anterior  limb  (Fig.  138,  5, 
5',  (J)  (.see  p.  270). 

The  third,  concealed  by  the  other  two,  forms  the  proper  extensor  of  the  internal  digit, 
and  resembles  its  fellow  in  the  fore  extremity   see  p.  270). 

2.  An  anterior  tibial  muscle  (muscular  portion  of  the  flexor  of  the  metatarsal  of 
the  Horse).  It  is  a  triangular,  muscular  body,  lodged  in  the  antero-external  fossa  of 
the  tibia  into  th.e  upper  part  of  which  it  is  inserted,  aad  ia  succeeded  by  a  tendon  that 


MUSCLES  OF  THE  POSTERIOR  LIMBS. 


307 


138. 


commences  towards  the  middle  of  the  tibia.  This  tendon  passes  through  a  ring  pierced 
in  the  tendon  of  the  muscle  that  represents  the  tendinous  ])ortion  of  the  tiexor  of  the 
metatarsus ;  it  then  deviates  inwards,  and  is  fixed  into  the  cuneiforms  and  the  superior 
extremity  of  the  principal  metatarsal  bone  (Fig.  138,  4). 

3.  A  ■proper  extensor  of  the  external  di<jit 
(lateral  extensor  of  the  phalanges  in  8olipe(is, 
the  peroneus  brevis  lateralis  in  I\Ian),  whose 
fleshy  body  is  altogether  similar  to  that  of  the 
analogous  muscle  in  the  Horse,  and  is  termi- 
nated by  a  long  tendon  which  resembles  that  of 
the  proper  extensor  of  the  internal  digit  (Fig. 
138,  7,  8,  9,  10). 

4.  A  muscle  which  represents  the  peroneous 
longus  in  ISIan,  and  of  which  in  Solipeds  there 
is  not  a  trace.  This  muscle  commences  by  a 
short,  conical,  muscular  body  in  front  of  the 
supero-external  tubei'osity  of  the  tibia ;  and  it 
terminates  by  a  loniC  tendon  whose  direction  is 
as  follows :  included  at  first,  like  the  muscular 
portion,  between  the  proper  extensor  of  the  ex- 
ternal digit  and  the  triple  muscular  fasciculvis 
already  described,  it  arrives  on  the  outside  of 
the  tarsus,  passes  through  the  fibrous  groove  of 
the  proper  extensor,  where  it  is  enveloped  by  a 
special  synovial  membrane,  passes  over  the 
latter  in  slightly  crossing  its  direction,  and  is 
inflected  at  first  hackwaids,  tiien  outwards,  in 
insinuating  itself  underneath  the  external  tibio- 
tarsal  ligament,  and  the  calcaneo-metatarsal 
and  the  posterior  tarso-metatarsal  ligaments, 
which  retain  it  in  a  channel  on  the  inferior 
face  of  the  cuboido-scaphoid  bone.  It  is  finally 
inserted  into  tlie  deep  face  ot  the  second  cunei- 
form bone,  and  the  external  side  of  the  sujierior 
extremity  of  the  metatarsus,  by  a  small  branch 
detached  from  tlie  outer  side  of  the  principal 
tendon. 

All  these  muscles  are  similarly  disposed  in 
the  Sheep  and  Goat. 

Pig. — The  anterior  tibial  muscles  of  this 
animal  resemble  those  of  Huminants,  with  the 
exception  of  some  peculiarities  of  secondary  im- 
portance, among  which  the  following  may  be 
cited  : 

The  muscular  fasciculus  which  replaces  the 
cord  of  the  flexor  metatarsi  in  the  Horse  termi- 
nates on  the  scaphoid  and  the  second  cuneiform 
bone.  The  common  extensor  of  tlie  digits  has 
four  tendons,  one  for  each  digit.  The  proper 
extensors  have  two  each,  one  for  the  small  digit, 
the  other  for  the  great.  The  anterior  tibial 
passes  to  the  second  cuneiform  bone.  The 
peroneals  longus  lateralis  is  inserted  by  its  ten- 
don into  tlie  upper  extremity  of  the  internal 
metatarsus. 

Carmvoka. — Four  muscles  are  described  in 
these  animals:    1,    An   anterior   tibial;    2,    A 


EXTERNAL   MUSCLES   OF   THE   LEG   OF 
THE   ox. 

Originating  tendon  of  the  muscle  which 
represents  the  anterior  e.xtensor  of  the 
phalanges  and  the  tendinous  cord  of  the 
flexor  metatarsi  in  the  Horse ;  2,  Its 
flexor  fasciculus ;  5,  That  which  forms 
the  common  extensor  of  the  digits  ;  5', 
The  tendon  of  this  fasciculus ;  6,  Its 
termiaal  bifurcation ;  3,  The  long  la- 
teral peroneus  ;  3',  Its  tendon  ;  4,  Origin 
of  the  anterior  tibial  (the  muscular  por- 
tion   of    the    flexor     metatarsi    in    the 


Horse);  7,  Proper  extensor  of  the 
external  digit  (short  lateral  peroneus) ;  8,  Its  tendon ;  9,  Its  insertion  into  the  second 
phalanx;  10,  Its  insertion  into  the  third  phalanx;  11,  External  belly  of  the  gas- 
trocnemii ;  11',  Their  tendon  ;  12,  Solearis  ;  13,  Tendon  of  the  perforatus  ;  14,  Perforans; 
14',  Its  tendon;  15,  Suspensory  ligament  of  the  fetlocli ;  16,  The  band  it  gives  off  to 
the  perforatus  tendon;  17,  That  which  it  sends  to  the  proper  extensor  of  the  external 
digit ;  18,  The  pedal  muscle*  19,  The  insertion  of  the  long  vastus  on  the  patella  and  its 
external  ligament. 


308  THE  MVSCLES. 

long  common  extensor  of  the  digits ;   3,  A  long  lateral  peroneus ;   4,  A  short  lateral 
peroneus. 

1.  Anterior  tibial. — Situated  in  front  of  the  tibia,  and  more  voluminous  than  the 
common  extensor  of  the  digits,  whose  superior  extremity  it  covers,  this  muscle  has  its 
origin  on  the  crest  and  external  tuberosity  of  the  tibia.  It  receives,  near  the  interior 
third  of  this  bone,  an  extremely  thin  muscular  band  wliich  proceeds  from  the  libula, 
and  which  we  may  with  justice  compare  to  the  })roper  extensor  of  the  big  toe  in  Jlan. 
Tlien  it  terminates  liy  a  tendon  on  the  metatarsal  bone  of  the  internal  digit;  when  this 
bone  is  coiniected  witli  a  digital  regicm,  the  third  phalanx  receives  a  particular  bianeh 
from  this  tendon,  which  represents  the  tendinous  portion  of  the  small  proper  extensor 
fasciculus  annexeil  to  the  anterior  tibial.  This  muscle  responds  :  in  front  to  the  tibial 
aponeurosis;  inwards  and  backwards,  to  the  tiliia;  outwards,  to  the  common  ex- 
tensor of  the  digits.  Its  tendon  is  fixed  in  the  bend  of  the  hock  by  a  fibrous  band, 
whose  arrangement  is  singular  enough  to  lieserve  mention  here.  Attached  in  front 
of  the  inferior  extremity  of  tiie  tibia,  this  band  gives  origin,  by  its  internal  extremity, 
to  a  strong  ligamentous  cord  which  passes  undi-r  the  tendon  of  the  anterior  tibial 
muscle  to  reach  the  anterior  face  of  the  tarsus,  where  it  contracts  intimate  adhesions 
with  the  capsular  ligament  of  this  region,  and  terminates  on  the  superior  extremity 
of  the  metatarsal  bone  of  the  middle  digit.  This  cord  binds  the  inferior  extremity  of 
the  tibia  to  the  metatarsus,  and  prevents  undue  extension  of  the  tibio-tarsal  articula- 
tion. It  is,  perhaps,  the  representative  of  the  tendinous  cord  of  the  anterior  tibial  region 
in  tlie  Horse. 

2.  Long  common  extensor  of  the  rligits. — This  muscle  is  composed  of  a  fusiform  fleshy 
body,  and'  a  quad ri furcated  tendon.  The  fleshy  body,  situated  beneath  the  tibial 
aponeurosis,  between  the  anterior  tibial  and  the  lateral  peroneal  muscles,  covers  the 
external  face  of  the  tibia  and  the  small  fasciculus  of  the  proper  extensor  of  the  thumb; 
it  originates  by  a  short  and  strong  tendinous  cord,  from  the  inferior  extremity  (jf  the 
femur,  between  the  external  condyle  and  the  trochlea.  The  tendon  is  continuous  with 
the  inferior  extremity  of  the  fleshy  portion,  passes  beneath  the  band  of  the  anterior 
tibial,  through  another  fibrous  ring  at  the  cuboid  bone,  and  is  inserted,  by  its  four 
terminal  branches  into  the  four  large  digits,  in  the  same  manner  as  the  analogous  tendon 
in  the  fore-limb. 

3.  Long  lateral  peroneus. — This  muscle  is  composed  of  a  very  short  conical  fleshy 
portion,  succeeded  by  a  long  tendon.  The  former  originates  in  front  of  the  tuberosity  of 
the  supero-external  tuberosity  of  the  tibii,  and  does  not  appear  to  have  any  connection 
with  the  fibula.  Included  between  the  common  extensor  of  the  digits  and  the  short 
lateral  peroneus,  it  is  covered  by  the  tibial  aponeurosis,  and  covers  the  anteiior  tibial 
vessels.  The  tendon  descends  parallel  with  the  fibula  to  its  inferior  extremity,  over  which 
it  glides  in  becoming  inflected.  On  reaching  the  cuboides,  it  enters  a  groove  excavated 
on  its  external  surface,  gives  otf  a  short  isolated  branch  to  the  superior  extremity  of  the 
first  metatarsal  bone,  afterwards  crosses  transversely  the  direction  of  the  tarsus  in 
passing  behind  the  inferior  row  of  bones,  and  terminates  on  the  metatarsus  of  the 
thumb.  On  its  way  behind  the  cuboides,  this  tendon  gives  off"  another  branch  which 
we  have  every  reason  to  believe  is  constantly  present;  it  is  a  short,  interosseous  fasci- 
culus, which  at  first  penetrates  between  the  cuboides  and  the  external  metatarsal  bone, 
then  between  the  latter  and  the  second  metatarsal. 

This  musele  carries  the  inferior  extremity  of  the  limb  outwards,  and  when  the 
foot  is  mueh  extended  it  may  act  as  a  flexor. 

4.  Short  lateral  peroneus. — In  Cainivora,  this  muscle  is  formed  of  two  fasciculi,  a 
superior  and  inferior,  which  may  be  described  as  two  distinct  muscles. 

The  superior  fasciculus  comprises  a  very  weak  muscular  portion  attached  to  the 
upper  third  of  the  anterior  boider  of  the  fibula,  and  a  funicular  tendon  succeeding  its 
inferior  extremity  about  the  mid  lie  of  the  tibia.  This  tendon  glides  over  the  inferior 
extremity  of  the  fibula,  behind  the  long  lateral  peroneus,  which  it  passes  under  and 
crosses  in  descending  to  the  phalanges  of  the  extn-nal  digit,  where  it  is  united  to  the 
tendinous  branch  of  the  common  extensor  belonging  to  this  digit. 

The  inferior  fasciculus  has  its  origin  on  the  anterior  border  and  external  aspect  of 
the  peroneus,  by  penniforni  fibres  which  join  a  short,  but  more  voluminous  tendon  than 
that  of  the  preceding  fasciculus.  This  tendon,  with  the  last,  enters  the  posterior 
groove  in  the  fibula,  and  is  attached,  by  its  inferior  extremity,  to  the  upper  end  of  the 
external  metatarsus,  outside  the  branch  furnished  by  the  long  lateral  peroneus  to  that 
bone. 

The  superior  fasciculus  acts  as  a  proper  extensor  of  the  external  digit.  The  inferior 
is  an  abductor  of  the  foot. 


MUSCLES  OF  THE  POSTERIOR  LIMBS.  309 

B.  Posterior  Tibial  Region. 

ErsiiNANTS. — Tn  the  Ox,  Sheep,  and  Goat,  the  muscular  portion  of  the  perforatus  13 
thicker  than  in  Solipeds.  The  portion  of  the  perforans  is  better  defined  than  in  Solipeds, 
and  is  lodged  in  a  depression  on  the  principal  portion ;  it  can  easily  be  traced  from  the 
supero-external  surface  of  tlie  tibia,  wliere  it  originates.  The  tendon  does  not  difler  from 
that  in  the  fore-limb  ;  but  the  bands  which  descend  from  the  metatarsus  to  tlie  heels,  to 
be  imited  with  the  two  terminal  branches  of  this  tendon,  are  much  smaller  than  those  in 
the  metacarpal  region. 

Cakxivora. — The  soletis  is  absent  in  the  Bog  and  Cat.  The  muscular  body  of  the 
perforatus  is  prismatic,  voluminous,  and  entirely  blended,  in  its  upper  two-thirds  at  least, 
with  the  external  gastrocnemius ;  these  two  muscles  have  therefore  a  common  origin.  The 
tendon  is  quadrifurcated,  as  in  the  anterior  limb ;  it  oflers  on  its  surface,  shortly  before 
its  division,  several  thin  muscular  bands,  traces  of  the  fleshy  portion  of  the  common  short 
muscle  of  ]\Ian.  Several  of  these  bands  come  from  the  perforans  tendon,  and  all  pass  to 
the  four  terminal  branches  of  the  muscle.  The  terminal  tendon  of  the  perforans  is  divided 
into  fuur  or  five  branches,  one  for  each  digit. 

The  posterior  tibial  is  not  united  inferiorly  to  this  tendon,  but  constitutes  a  perfectly 
distinct  muscle  situated  between  the  deep  and  oblique  flexors  of  the  phalanges.  Formed 
by  a  very  small  fleshy  body  and  a  long  thin  tendon,  this  muscle  originates  above  the 
peroneus,  ficm  the  posterior  surface  of  the  tibia.  Its  tendon  lies  beside  that  of  the 
oblique  flexor,  and  with  it  enters  tlie  groove  behind  and  within  the  inferior  extremity  of 
the  tibia.  Enveloped  by  a  synovial  membrane  proper  to  its  passage  through  this  groove, 
this  tendon  soon  leaves  it  to  pass  to  the  free  surface  of  the  posterior  tarso-metatarsal 
ligament,  with  which  it  is  blended  towards  the  middle  of  the  tarsus. 

COMPARISON  OF  THE  MTSCLES  OF  THE  LEG  OF  M.4N  WITH  THOSE  OF  ANIMALS. 

In  Man,  the  muscles  of  the  leg  are  divided  into  three  regions :  an  anterior,  external, 
and  posterior 

A.  Anterior  Region. 

This  includes  three  muscles : 

1.  The  anterior  tibial,  which  corresponds  to  tlie  fleshy  portion  of  the  flexor  of  the 
metatarsus,  aud  whose  imperforate  tendon  is  fixed  into  the  first  cuneiform. 

2.  The  common  long  extensor  of  the  toes,  which  represents  the  anterior  extensor  o  the 
phalanges  of  the  Horse.  This  muscle  is  attached,  above,  to  the  external  tuberosity  of  the 
tibia  and  the  upper  three-fourths  of  the  inner  face  of  the  fibula ;  its  tendon  divides  into 
two  fasciculi,  the  internal  of  which  furnishes  a  branch  to  the  second,  third,  and  fourth 
toes,  and  the  external  goes  to  the  fifth. 

3.  The  proper  extensor  of  the  large  toe,  represented  in  the  Dog  by  a  small  fasciculus 
blended  with  the  anterior  tibial,  is  an  elongated  semi-penniform  muscle  which  arises 
from  the  inner  face  of  the  fibula  and  the  interosseous  ligament,  and  terminates  on  the 
second  phalanx  of  the  great  toe,  after  receiving  the  pedal  tendon  {extensor  brevis 
digitorum). 

B.  External  Region. 

This  region  is  only  composed  of  two  muscles :  the  long  and  short  peroneus. 

The  first,  which  does  not  exist  in  Solipeds,  is  a  penniform  muscle  attached  to  the 
upper  third  of  the  fibula,  the  external  tuberosity  of  the  tibia,  and  the  internal  face  of  the 
tibial  aponeurosis,  by  the  superior  extremities  of  its  muscular  fibres.  The  flat  tendon 
which  terminates  it  is  fixed  to  the  outer  portion  of  the  base  of  the  first  metatarsal. 

The  second  corresponds  to  the  lateral  extensor  of  the  phalanges  of  the  Horse,  and  is 
found  in  all  animals.  It  is  penniform,  and  is  attached  above,  by  its  fleshy  fibres,  to  the 
lower  two-thirds  of  the  external  face  of  the  fibula ;  below,  by  its  tendon,  to  the  upper 
extremity  of  the  fifth  metatarsal. 

These  two  muscles  determine  very  complicated  movements  in  the  region  of  the  foct. 

C.  Posterior  Region. 

The  posterior  tibial  muscles  form  two  layers :  a  superficial  and  a  deep 
The  first   comprises   the  crural  triceps  and  the  plantaris.     The  triceps  itself  is 
23 


310 


THE  MUSCLES. 


composed  of  the  gastrocnemii,  of  which  we  will  say  nothing,  and  the  snieus.  Tlie  latter 
is  flattened  from  before  to  behind,  attached  to  the  upper  third  of  the  fibula,  the  oblique 
line  of  the  tibia,  and  the  middle  third  of  the  inner  border  of  this  bone,  and  terminated 
by  an  aponeurotic  lamina  which  is  blended  with  the  tendo- Achilles.  The  plantaris  is 
formed  by  a  small  fusiform  muscular  body,  situated  beneath  the  external  gemellus,  then 


Fig.  139. 


Fig.  140. 


'-\Y 


MUSCLES  OF  THE  HUMAN  LEG;   ANTERIOR 
TIBIAL   REGION. 

1,  Quadriceps  extensor  inserted  into  the  pa- 
tella— the  figure  is  on  the  tendon  of  the 
rectus,  the  vastus  internus  and  externus 
being  on  each  side;  2,  Subcutaneous  sur- 
face of  the  tibia;  3,  Tibialis  anticus;  4, 
Extensor  longus  digitorum;  5,  Extensor 
proprius  pollicis ;  6,  Peroneus  tertius;  7, 
Peroneus  longus ;  8,  Peroneus  brevis ;  9,  9, 
Borders  of  the  soleus  muscle ;  10,  Part  of 
the  inner  belly  of  the  gastrocnemius;  11, 
Extensor  brevis  digitorum — the  tendon  in 
front  of  the  cipher  is  that  of  the  peroneus 
tertius,  that  behmd  it  the  peroneus  brevis. 

by  a  long  slender  tendon,  which  is  confounded  with  the  inner  border  of  the  tendo- 
Achilles,  or  is  inserted  into  the  os  calcis. 

Tiie  deep  layer  is  composed  of  four  muscles: 

1.  The  p<)}iliteus,  which  in  its  attachments  and  position  resembles  that  of  animals. 

2,  The  common  long  flexor  of  the  ^oeSj^corresponding  to  the  oblique  flexor  of  animals. 


SUPERFICIAL   POSTERIOR   MUSCLES  OP 
THE    HUMAN    LEG. 

1,  Biceps  forming  outer  ham-string;  2,  Ten- 
dons forming  inner  ham-string ;  3,  Popli- 
teal space ;  4,  Gastrocnemius  ;  5,  5,  Soleus  ; 
6,  Tendo-Achilles  ;  7,  Posterior  tuberosity 
of  OS  calcis ;  8,  Tendons  of  peroneus  longus 
and  brevis  passing  behind  the  outer  ankle ; 
9,  Tendons  of  tibialis  posticus  and  flexor 
longus  digitorum  passing  into  the  foot 
behind  the  inner  ankle. 


MUSCLES  OF  THE  POSTERIOR  LIMBS.  311 

It  is  an  elongated  penniform  muscle,  fixed  above  lo  the  oblique  line  and  middle  third  of 
the  posterior  face  of  the  tibia.  It^  tendon  is  inflected  beneath  the  external  malleolus, 
piisses  in  front  below  the  astragalus,  receives  the  accessory  of  the  long  flexor,  and  then 
diviiles  into  four  branches  for  the  four  lesser  toes. 

3.  The  posterior  tibial,  represented  by  a  portion  of  the  perforans  of  animals ;  its 
tendon  is  reflected  beneath  the  internal  malleolus  of  the  tibia,  and  is  attached  to  the 
scaphoid  process. 

4.  The  proper  long  tfexorof  the  great  toe,  also  represented  by  a  portion  of  the  perforans. 
This  muscle  is  voluminous  and  prismatic,  and  is  attached  above  to  the  lower  two-thirds 
of  the  posterior  face  of  the  fibula.  Its  tendon  is  reflected  inwards  on  the  astragalus  and 
the  groove  in  the  os  calcis,  crosses  the  tendon  of  the  common  long  flexor,  and  terminates 
on  the  posterior  extremity  of  the  third  phalanx  of  the  great  toe. 

MUSCLES    OF    THE    POSTERIOR    FOOT. 

SoLiPEDS. — Tn  these  animals  are  found :  1,  Two  lumhrici  and  two 
interosseous  muscles,  correspouding  to  those  of  the  anterior  limb ;  2,  A  pedal 
muscle. 

Pedal  muscle. — The  tarso-prephalangeus  of  Girard.  (The  flexor  meta- 
tarsi parvus.  Not  mentioned  by  Percivall.)  This  is  a  small  ribaud-shaped 
fasciculus,  situated  in  front  of  the  principal  metatarsal  bone,  beneath  the 
extensors  of  the  phalanges.  It  is  attached,  by  its  inferior  extremity,  to 
the  internal  surface  of  the  tendon  common  to  these  two  muscles,  and  by  its 
upjjer  extremity  to  the  lower  end  of  the  os  calcis  (and  astragalus).  It  aids 
in  extending  the  digit  (flexing  the  hock,  and  probably  keeping  the  tendons 
tense.) 

RniixAXTS. — The  pedal  is  the  only  muscle  in  the  region  of  the  foot  met  with  in 
Euminants.  It  is  attached,  inferiorly,  to  the  tendon  of  the  common  extensor  and  that  of 
the  proper  extensor  of  the  internal  digit. 

Pig. — This  animal  possesses  :  1,  A  pedal  muscle  attached,  below,  to  the  two  branches 
of  the  common  extensor  of  the  large  digits  :  2,  Four  interosseous  met:darsal  muscles,  which 
do  not  appear  to  difler  in  their  general  arrangement  from  the  metacarpal  interosseous 
muscles. 

Cakn'ivora. — In  the  Dog  and  Cat  there  exist  in  the  region  of  the  posterior  foot : 

1.  A  pedal  muscle,  composed  of  three  fasciculi  which  have  their  origin  either  from  the 
inferior  extremity  of  the  os  calcis.  or  from  the  tendinous  sheaths  in  the  bend  of  the  hock ; 
they  terminate  on  the  second,  third,  and  fourth  digits  by  small  tendons  joined  to  the 
branches  of  the  common  extensor. 

2.  The  muscular  digitiitions  annexed  to  the  tendon  of  the  perforatus,  traces  of  the 
fleshy  portion  of  the^earor  brecis  digitoruiu  of  Man. 

3.  A  flexor  pedis  accessorius,  or  perforans,  a  small  undeveloped  muscle  commencing 
outside  the  tarsus,  and  terminating  by  a  very  delicate  aponeurosis  on  the  posterior  face  of 
the  perforans  tendon. 

4.  Two  or  three  pale  and  rudimentary  bands,  situated  inside  the  tarsus  and  near  the 
internal  digit.     These  are  the  vestiges  of  the  muscles  proper  to  the  great  toe  in  Man. 

5.  An  adductor  of  the  little  toe  (abductor  minimi  digit)  is  a  thin,  elongated  muscle, 
carried  obliquely  from  the  posterior  tarso-metatarsal  ligament  to  the  internal  side  of  the 
first  phalanx  of  that  digit 

6.  Four  interosseous  metatarsal  muscles,  resembling  the  analogous  muscles  of  the 
metacarpal  region. 

7.  Lumhrici,  similar  to  those  of  the  anterior  limb. 

COMPARISOX  OF  THE  MUSCLES   OF   THE  FOOT  IN  MAN  WITH   THOSE   OP  ANIMALS. 

In  Man,  there  are  distinguished  the  muscles  of  the  dorsal  region,  the  plantar  region, 
and  the  interosseous  muscles. 

A.  Dorsal  Region. 

This  only  contains  one  muscle,  the  pedal  (extensor  hrevis  digitorum).  It  is  attached, 
behind,  to  the  antero-extemal  part  of  the  upper  face  of  the  os  calcis  by  several  aponeurotic 
laminae  ;  its  fleshy  fasciculi,  four  in  number,  are  prolonged  by  as  many  tendons  destined 
to  the  first  four  toes;  thiee  of  them  puss  along  with  the" tendons  of  the  common  extensor. 


312 


THE  MUSCLES. 


B.  Plantar  Region. 

This  is  subdivided  into  three  regions :  a  middle,  internal,  and  external. 

The  first  comprises:  1.  The  common  short  flexor  of  the  toes  which  is  represented  in 
Solipeds  by  a  portion  of  the  perforatus.  It  is  attached  to  the  infero-interual  tuberosity  of 
the  OS  calcis,  and  to  the  upper  face  of  the  middle  plantar  aponeurosis.  It  is  followed  liy 
four  tendons,  which  are  inserted  into  the  second  phalanges  of  the  first  four  toes,  after 
forming  rings  through  wiiich  pass  the  tendons  of  the  common  long  flexor. 

2.  The  accessory  of  the  long  flexor,  whose  fibres  pass  to  the  tendons  of  the  common 
flexor. 

3.  The  lumhrici,  four  in  number,  and  analogous  to  those  of  the  hand. 

The  internal  plantar  region  is  composed  of  three  muscles,  which  are  found  iu  a 
rudimentary  condition  in  the  Dog. 


Fig.  141. 


Fig.  142. 


'FIRST  LAYER  OF   PLANTAR  MUSCLES  OF 
HUMAN   FOOT. 

1,  Os  calcis;  2,  Posterior  part  of  plantar 
fascia  divided  transversely ;  3,  Abductor 
pollicis ;  4,  Abductor  minimi  digitii ;  5, 
Flexor  brevis  digitorum ;  6,  Tendon  of 
flexor  longus  pollicis ;  7,  7,  Lumbricales. 


THIRD   AND  PART  OF  SECOND  LATER  OF 
PLANTAR   MUSCLES   OF   HUMAN   FOOT. 

1,  Incised  plantar  fascia ;  2,  Musculus  acces- 
sorius ;  3,  Tendon  of  flexor  longns  digi- 
torum ;  4,  Tendon  of  flexor  longus  pollicis ; 
5,  Flexor  brevis  pollicis ;  6,  Adductor  pol- 
licis ;  7,  Flexor  brevis  minimi  digitii ;  8, 
Transversus  pedis ;  9,  Interossei  muscles, 
plantar  and  dorsal ;  10,  Convex  ridge 
formed  by  tendon  of  peroneus  longus  in  its 
oblique  course  across  the  foot. 

1.  The  short  adductor  of  the  great  toe,  which  extends  from  the  internal  tuberosity  of 
the  OS  calcis  to  the  internal  sesamoid  and  the  first  phalanx  of  the  gi-eat  toe. 

2.  The  short  flexor  of  the  great  toe,  which  arises  from  the  third  cuneiform  and  the 
tendon  of  the  posterior  tibial,  and  terminates  by  two  branches  on  the  external  sesamoid 
and  the  internal  sesamoid  of  the  great  toe. 

3.  The  short  adductor  of  the  great  toe,  a  muscle  formed  by  two  fasciculi,  and  having  a 
common  termination  on  the  external  sesamoid.  One  of  these  fasciculi  arises  from  the 
inferior  face  of  the  cuboidos,  tlie  third  cuneiform,  and  the  base  of  the  third  and  fourth 
metatarsal ;  it  has  been  formerly  described  as  the  oblique  adductor.  The  other  has  its 
origin  from  the  inferior  face  of  the  three  last  metatarsophalangeal  articulations  :  this 
has  also  been  called  the  transverse  adductor. 


MUSCLES  IN  BIRDS.  31S 

The  external  plantar  rosion  likewise  comprises  three  muscles,  whicli  are  : 

1.  The  itJiort  abductor  of  the  little  toe,  which  is  detached  from  the  internal  tuberosity 
of  the  OS  calcis,  and  is  inserted  into  the  external  portion  of  the  first  jihalanx  of  the  little 
toe. 

2.  The  short  flexor  of  the  little  toe  is  attached,  behind,  to  the  sheatli  of  the  long 
peroneus  and  to  the  process  of  the  fifth  metatarsal ;  in  front,  to  the  external  part  of  the 
first  phalanx  of  tlie  little  toe. 

3.  The  opponens  of  the  little  toe,  concealed  beneath  the  preceding,  is  inserted  at 
one  end  to  the  sheath  of  the  long  peroneus,  and  at  the  other  to  the  external  border  of 
the  fifth  metatarsal. 

C.  Interosseous  Muscles, 

Tliese  are  divided  into  dorsal  and  plantar  interossei.  Their  disposition  is  nearly 
the  same  as  in  the  hand. 


CHAPTEE  III. 

THE   MUSCLES   IN   BIRDS. 


In  birds  we  find  the  majority  of  the  muscles  already  described  ;  though  they  are  appro- 
priate by  their  form,  volume,  arrangement,  etc.,  to  the  particular  conformation  of  the 
skeleton  in  these  animals. 

To  undertake,  in  this  essentially  practical  work,  a  special  description  of  all  these 
organs,  would  be  to  depart  from  the  object  aimed  at  :  and  we  therefore  confine  ourselves 
to  tiiose  points  whicii  present  most  interest  in  an  animal  mechanic  point  of  view. 

1.  Tendons. — The  tendons  in  birds  present  in  the  inferior  limbs  and  at  the  extremity 
of  the  wings  an  amount  of  ossification  more  or  less  extensive  along  their  course.  This 
transformation  of  the  fibrous  tissue  of  the  muscles  is  not  the  eftect  of  senility,  for  it  is 
noticed  in  very  young  animals. 

The  tendons,  in  losing  the  greater  part  of  their  elasticity,  doubtless  gain  in  tenacity  ; 
and  this  allows  them  to  transmit  to  the  bony  levers  the  umscular  efforts  in  a  more 
integral  manner. 

It  is  also  observed  that  the  partial  ossification  of  the  tendons  does  not  exclusively 
belong  to  the  limbs ;  for  it  is  not  rare  to  meet  with  this  change  in  otlier  regions,  as  in 
the  neck  of  wading  birds.  In  the  museum  of  the  Veterinary  School  at  Lyons  is  the 
skeleton  of  a  heron  which  shows  this  peculiarity  in  the  higliest  decree ;  the  cervical 
vertebrjB  are  rougliened  by  a  multitude  of  filiform  bony  stylets,  all  directed  backwards, 
and  which  have  originated  from  the  ossification  of  the  tendinous  fibrillte  annexed  to  the 
muscles  of  the  cervical  region. 

2.  The  Pectoral  3Iuscles. — The  two  alternative  movements  which  produce  flight — the 
elevation  and  de()ress?ion  of  the  wings — being  due  to  the  action  of  the  pectoral  muscles, 
these  merit  special  notice. 

The  superficial  or  great  pectoral,  "  which  alone  weighs  heavier  than  all  the  other 
muscles  of  the  bird  put  together,  is  attached  to  the  furculimi,  to  the  great  ridge  of  the 
sternum,  and  to  the  last  ribs ;  it  is  inserted  into  the  very  salient  rugged  outline  of  the 
humerus.  It  is  by  this  muscle  that  birds  are  able  to  give  tliose  powerful  strokes  of  the 
wings  which  are  necessary  in  flight." 

The  deep  or  small  pectoral  is  "  placed  in  the  angle  formed  by  the  body  of  the  sternum 
and  its  crest,  and  in  the  interval  between  the  furculum  and  tiie  coracoid  bone. 
Its  tendon  passes  through  the  foramen  formed  by  the  union  of  the  furculum,  the  coracoid 
bone,  and  the  scapula,  as  over  a  pulley ;  it  is  inserted  above  the  head  of  the  humerus, 
which  it  raises.  It  is  by  means  of  this  arrangement  that  nature  has  been  able  to  place 
an  elevator  and  depressor  at  the  inferior  surface  of  the  trunk  so  far  from  the  centre  of 
gravity,  without  which  the  bird  would  have  been  liable  to  lose  its  equilibrium  and  tumble 
over  head  foremost  in  the  air.' 

Cuvier,  adopting  the  nomenclature  of  Vicq-d'Azyr.  called  this  muscle  the  middle 
perioral,  and  he  gave  the  name  of  small  pectoral  to  a  triangular  fasciculus  which  leaves 
the  lateral  angle  of  the  sternum  and  the  base  of  the  coracoid  bone,  to  be  inserted  under 


Cuvier,  '  Lcyons  d'Anatomie  Compare'e.' 


314  THE  MUSCLES. 

the  head  of  the  humeius.  In  our  opinion,  tliis  tendon  does  not  belong  to  the  pectoral 
region,  but  to  that  of  the  shoulder ;  and  with  J.  F.  Meckel  we  are  inclined  to  consider  it 
as  tlie  coiaco-humeralis,  which  has  followed  the  coracoid  process  in  its  development.' 

3.  The  Diaphragm. — "  In  birds,  the  diaphragm  is  so  differently  disposed  from  what 
it  is  in  the  higher  vertebrata,  that  its  existence  luis  been  suc-ce»sively  described  and  mis- 
understood, admitted  and  refuted,  and  is  still  looked  upon  as  problematical  by  a  large 
number  of  anatomists.  Nevertiieless,  this  muscle  exists,  and  its  development  is  in 
perfect  harmony  witli  the  importjince  of  its  functions.  It  is  composed  of  two  planes, 
which  at  their  origin  are  confounded  with  each  other,  but  soon  become  separated  and 
pursue,  one  a  transverse,  the  other  an  oblique  direction.  The  transverse  plane  ia 
triangular  in  form,  and  is  carried  horizontally  from  the  riglit  to  the  left  ribs  against  the 
inferior  surface  of  the  lungs.  The  oblique  plane  is  convex  in  front,  concave  behind,  and 
extends  from  the  dorsal  aspect  of  the  spine  to  the  sternum,  dividing  the  cavity  of  the 
trunk  into  two  secondary  cavities — the  thoiax  and  abdomen. 

"  In  birds,  as  in  mammals,  the  diaphragm  is  therefore  intended  to  perform  two  principal 
functions;  but  to  do  this  perfectly  in  the  former,  it  is  doubled.  So  far,  then,  from  this 
inspiratory  muscle  being  absent  in  birds,  or  from  its  existing  in  a  rudimentary  degree, 
they  are  really  provided  with  two  diaphragms:  1,  A  pulmonary  diaphragm,  which 
presides  in  the  dilatation  of  the  lungs ;  2,  A  thoracic  ahdmninal  diaphragm,  which  par- 
titions the  great  cavity  of  the  trunk,  and  concurs  in  the  inspiration  of  the  air  by  dilating 
the  large  serial  reservoirs  lying  at  its  posterior  surlace.  Of  these  two  muscular  planes, 
the  first  is  analogous  to  that  portion  of  the  diaphragm  which,  in  Man  and  the  mammalia, 
is  inserted  into  the  sternum  and  the  ribs ;  the  second  manifestly  represents  the  pillars 
of  the  diaphragm." 

This  description,  taken  from  tlie  work  of  M.  Sappey.  an  observer  who  is  as  conscien- 
tious as  he  is  talented,  gives  a  perfectly  exact  idea  of  this  muscle. 

*  E.  Geoffrey  Saint-Hilaire,  in  his  memoir  on  the  bones  of  the  sternum  ('  Philosophie 
Anatomique,'  vol.  i.  p.  89),  in  comparing  the  pectoral  muscles  of  fish  to  those  of  birds, 
also  employs  the  nomenclature  of  Vicq-d'Azyr,  and  recognises  three  pectorals  as  well. 
We  are,  iiowever,  obliged  to  confess  ourselves  as  in  opposition  to  the  great  master  who 
has  establisiied  rules  to  follow  in  the  classification  of  organs,  in  consequence  of  his 
having  limited  his  comparisons  to  the  two  classes  of  vertebrata  he  had  principally  in 
view.  If  he  had  extended  his  observations  to  the  mammalia,  and,  in  them  sought  for  the 
analogue  of  the  pectoralis  parvus,  he  would  have  discovered  it,  as  we  have  done,  in  the 
region  of  the  shoulder,  and  not  in  that  of  the  sternum. 


CHAPTER  IV. 
GENERAL  TABLE   OF   THE    INSERTIONS   OF   THE   MUSCLES   IN 

solipeds. 
1.  Yeetebeal  Column. 

A.   CERVICAL   TEBTEBBiE. 

I.  AUtlS. 

The  atlas  gives  insertion  to  nine  pairs  of  muscles  : — 

a.  By  the  surface  representing  the  spinous  process,  to  the  — 

Small  posterior  recti  muscles  of  the  head. 

b.  By  its  transverse  processes,  to  the — 

1.  Splenius  muscles. 

2.  Small  complexus  muscles. 

3.  Great  oblique  muscles  of  the  head. 

4.  Small  oblique  muscles  of  the  head. 

5.  Mastoido-humeralis  muscles. 

c.  By  its  body,  to  the — 

1.  Small  anterior  recti  muscles  of  the  head. 

2.  Small  lateral  recti  muscles. 

3.  Long  muscle  of  the  ueck. 

II.  Axis. 

The  axis  gives  insertion  to  six  pairs  of  muscles  : — 

a.  By  its  spin4)us  process,  to  the— 

1.  Transverse  spinous  muscles  of  the  neck. 

2.  Great  oblique  muscles  of  the  head. 

3.  Great  posterior  recti  muscles  of  the  head. 

b.  By  its  transverse  processes,  to  the — 

1.  Intertransverse  muscles  of  the  neck. 

2.  Mastoido-humeralis  muscles. 

And  by  the  inferior  face  of  its  body,  to  the — 

3.  Long  muscle  of  the  neck. 

III.  Third,  Fourth,  Fifth,  SiJcth,  and  Seventh  Cervical  Vertebrae. 
These  vertebrae  give  insertion  to  the  following  muscles : — 

a.  By  their  spinous  processes,  to  the — 

1.  Transverse  spinous  muscles  of  the  neck. 

2.  lUo-spinalis  muscles  (-ith  to  the  7th). 

b.  By  their  articular  tubercles,  to  the — 

1.  Great  complexus  muscles. 

2.  Small  complexus  muscles. 

3.  Transverse  spinous  muscles  of  the  neck. 

4.  Intertransverse  muscles  of  the  neck. 

c.  By  their  transverse  processes,  to  he — 

1.  Angular  muscles  of  the  scapula. 

2.  Splenius  muscles  (3rd  and  4tli). 

3.  Mastoido-humeralis  muscles  (3rd  and  4th). 

4.  Common  intercostal  muscles  (7th  . 

5.  Intertransverse  muscles  of  the  neck. 

6.  Iho-spinalis  muscles  (inferior  branch^ 


316  THE  MUSCLES. 

And  by  the  inferior  faces  of  their  bodies,  to  the — 

1.  Great  anterior  recti  muscles  of  the  head. 

2.  Long  muscle  of  the  neck. 


B.   DORSAL   VERTEBRA. 

The  dorsal  vertebrae  give  insertion : — 
a.  By  their  spinous  processes,  to  the — 

1.  Splenius  muscles  (1st  to  5th  or  6th). 

2.  Great  coniplexus  muscles  (1st  to  6th). 

3.  Small  complexus  muscles  (1st  and  2nd). 

4.  Trapezius  muscles. 

5.  Great  dorsal  muscles  (4th  to  18th). 

6.  Rhomboid  muscles  (2nd  to  7th). 

7.  Small  anterior  serrated  muscles  (2nd  to  13th). 

8.  Small  posterior  serrated  muscles  (10th  to  18th). 

9.  Ilio-siiinalis  muscles. 

10.  Transverse  spinous  muscles  of  the  back  and  loins. 

6,  By  their  transverse  processes,  to  the — 

1.  Great  complexus  muscles. 

2.  Small  complexus  muscles. 

3.  Ilio-spinalis  muscles. 

4.  Transverse  spinous  muscles  of  the  back  and  loins. 

5.  Supercostal  muscles. 

e.  By  their  bodies,  to  the — 

1.  Long  muscle  of  the  neck  (1st  to  6th). 

2.  Great  psoas  muscles  (17th  to  IStli). 

3.  Small  psoas  muscles  (16th  to  18th). 

C.   LUMBAR  VERTEBRA. 

The  lumbar  vertebrae  give  insertion : — 
a.  By  their  spinous  processes,  to  the — 

1.  Great  dorsal  muscles. 

2.  Small  posterior  serrated  muscles  (1st  to  3rd), 

3.  Ilio-spinalis  muscles. 

4.  Transverse  spinous  muscles  of  the  back  and  loins. 

6.  By  their  articular  tubei'cles,  to  the — 

1.  Ilio-spinal  muscles. 

2.  Transverse  spinous  muscles  of  the  back  and  loins. 

c.  By  their  transverse  processes,  to  the — 

1.  Great  psoas  muscles. 

2.  Square  muscles  of  the  loins. 

3.  Intertransverse  muscles  of  the  loins. 

4.  Transverse  muscles  of  the  abdomen. 

5.  llio  spinalis  muscles. 

d.  By  their  bodies,  to  the — 

1.  Great  psoas  muscles. 

2.  Small  psoas  muscles. 

3.  Pillars  of  the  diaphragm. 

D.   SACRTJM. 

The  sacrum  gives  insertion  to  the — 

1.  Ilio-spinalis  muscles. 

2.  Transverse  spinous  muscles  of  the  back  and  loins. 

3.  Superior  sacro-coccygeal  muscles. 

4.  Lateral  sacro-coccygeal  muscles. 

5.  Inferior  sacro-coccygeal  muscles. 


GENERAL  TABLE  OF  MUSCULAR  INSERTIONS.  317 

6.  Ischiococcygeal  muscles. 

7.  Long  vasti  muscles. 

8.  Semitendinosus  muscles. 

9.  Internal  obturator  muscles. 

E.   COCCTX. 

The  coccyx  gives  insertion  to  the — 

1.  Superior  sacro- coccygeal  muscles. 

2.  Inferior  sacro-coccygeal  muscles. 

3.  Lateral  sacro-coccygeal  muscles. 

4.  Ischio-coccygeal  muscles  (1st  and  2nd  coccygeal  vertebra"). 


2.  Head. 

A.   BONES  OP  THE   CRA>frC"SI. 

I.  Occipital. 

The  occipital  gives  insertion  to  nine  pairs  of  muscles  :— 

1.  Great  complexus  muscles. 

2.  Small  oblique  muscles  of  the  head. 

3.  Great  posterior  recti  muscles  of  the  head. 

4.  Small  posterior  recti  muscles  of  the  head. 

5.  Great  anterior  recti  muscles  of  the  head. 

6.  Small  anterior  recti  muscles  of  the  heud. 

7.  Small  lateral  recti  muscles. 

8.  Digastric  muscles. 

9.  Occipito-styloid  muscles. 

II.  Parietal. 

The  parietal  gives  attachment  to  one  muscle ; — 
The  temporal. 

III.  Frontal. 
The  frontal  gives  insertion  to  the — 

Supernaso-labial  is. 

rV  Sphenoid. 
The  sphenoid  gives  attachment  to  four  muscles  : — 

1.  Great  anterior  recti  muscles  of  the  head. 

2.  Small  anterior  recti  muscles  of  the  head. 

3.  Internal  pterygoid  muscles. 

4.  External  pterygoid  muscles. 

V.  Temporal. 
The  temporal  gives  insertion  to  five  muscles  : — 

1.  Splenius. 

2.  Small  complexus. 

3.  Small  oblique  muscle  of  the  head. 

4.  Mastoido-humeraUs. 

5.  Temporal. 

B.   BOXES   OF   THE   FACE. 

I.  Superior  Maxillary. 
The  supermaxillary  gives  insertion  to  the  following  muscles ; 

1.  Cuticularis  of  the  neck. 

2.  Alveoli-labialis. 


318  THE  MUSCLES. 

3.  Supermaxillo-nasalis. 

4.  Great  supermaxillo-nasalia. 

5.  Masseter. 

II.  Premaxillary  Bone. 
The  premaxillary  bone  gives  insertion  to  the — 

1.  Small  supermaxillo-nasalis. 

2.  Anterior  middle  or  intermediate  muscle. 


III.  Palatine  Bone. 
The  palatine  bone  gives  insertion  to  the — 
Internal  pterygoid  muscle. 

IV.  Zygomatic. 

The  zygomatic  bone  gives  insertion  to  one  muscle,  the — 
Supermaxillo-labialis. 

V.  Lachrymal. 

The  lachrymal  bone  gives  insertion  to  one  muscle,  the — 
Lachrymo-labialis. 

VI.  Nasal  Bone. 
The  nasal  bone  gives  insertion  to  one  muscle,  the — 
Supernaso-labialis. 

VII.  Inferior  Maxilla. 
The  inferior  maxilla  gives  insertion  to  the  following  muscles : 

1.  Sterno-maxillaria. 

2.  Alveolo-labialis. 

3.  Maxillo-labialia. 

4.  Posterior  middle  or  intermediate  muscles. 

5.  Masseter  muscles. 

6.  Temporal  muscles. 

7.  Internal  pterygoid  muscles. 

8.  External  pterygoid  muscles. 

9.  Digastric  muscles. 

10.  Mylo-liyoid  muscle. 

11.  Genio-hyoid  muscles. 

C.   HYOID  BONE. 

The  hyoid  bone  gives  insertion  to  the  following  muscles : — 

a.  By  its  hody  and  its  thyroid  cornua — 

1.  Sterno  hyoid  muscles. 

2.  Sea pulo- hyoid  muscles. 

3.  Mylo-hyoid  muscles. 

4.  Genio-hyoid  muscles. 

5.  Stylo-hyoid  muscles. 

6.  Kerato-hyoid  muscles. 

7.  Transverse  muscle  of  the  hyoid  bone. 

b.  By  its  branches  (styloid  cornua  and  styloid  bones) — 

1.  Stylo-hyoid  muscles. 

2.  Kerato-hyoid  muscles. 

3.  Occipito-styloid  muscles. 


GENERAL  TABLE  OF  MUSCULAR  INSERTIONS.  819 

3.  Bones  of  the  Thorax. 

A.   THE   BIBS   AXD  THEIK   CARTILAGES. 

The  ribs  and  costal  cartilages  give  insertion  to  the — 

1.  Scalenus  (1st). 

2.  Small  anterior  serrated  muscle  (5th  to  9th). 

3.  Small  posterior  serrated  musfle  (9th  to  18th). 

4.  Dio-spinalis  muscle  (3rd  to  18th). 

5.  Common  intercostal  muscle. 

6.  Great  psoas  (17th  to  18th). 

7.  Square  muscle  of  the  loins  (IGth  to  18th). 

8.  Great  serrated  muscle  1 1st  to  8th). 

9.  TransTcrse  muscle  of  the  ribs  (1st). 

10.  External  intercostal  muscles. 

11.  Internal  intercostal  muscles. 

12.  Supercostal  muscles. 

13.  Triangular  muscle  of  the  sternum  (2nd  to  8th) 

14.  Great  oblique  muscle  of  the  abdomen  (5th  to  ISth). 

15.  Small  oblique  muscle  of  the  ahdomen  (asternal  caitilages). 

16.  Great  rectus  muscle  of  the  abdomen  (asternal  cartilagesj. 

17.  Transverse  muscle  of  the  abdomen. 

18.  Diaphragm  (7th  to  18th). 


The  sternum  gives  insertion  to  the — 

1.  Cuticularis  of  the  neck. 

2.  Sterno-masillary  muscles. 

3.  Sterno-thyroid  muscles. 

4.  Sterno-hyoid  muscles. 

5.  Superficial  pectoral  muscles. 

6.  Deep  pectoral  muscles. 

7.  Transverse  muscles  of  the  ribs. 

S.  Triangular  muscle  of  the  sternum. 
9.  Great  recti  muscles  of  the  abdomen. 

10.  Transverse  muscles  of  the  abdomen. 

11.  Diaphragm. 

4.  Thoracic  Limb. 

A.  BONNES  OF  THE  SHOULDER. 

Scapula. 
The  scapula  gives  insertion  to  seventeen  muscles : — 
a.  By  its  externnl  face  to  the — 

1.  Supraspinatus. 

2.  Subspiuatus. 

3.  Short  abductor  of  the  arm,  or  teres  minor. 

4.  Long  abductor  of  the  arm. 

5.  Trapezius 

6.  Mastoido-humeralis. 

h.  By  Us  internal  face,  to  the — 

1.  Ehomboid  muscle. 

2.  Angular  muscle  of  the  scapula. 

3.  Great  serrated  muscle. 

4.  Subscapularis. 

5.  Small  scapulo-humeral  muscle. 

c.  By  its  anterior  border,  comprised  beiiceen  the  cervical  angle  and  the  coracoid 

process,  to  the — 

i.  Sterno-prescapularis,  or  small  pectoral  muscle. 


320  TEE  MUSCLES. 

2.  Long  flexor  of  the  fore-arm,  or  brachial  biceps. 

3.  Coraco-brachial  muscle. 

4.  Supraspinatus  muscle. 

d.  By  its  posterior  border,  comprised  betiveen  the  dorsal  angle  and  the  corrc 
sponding  portion  of  the  humeral  angle,  to  the — 

1.  Long  extensor  of  the  fore-arm. 

2.  Large  extensor  of  the  fore-arm. 

3.  Adductor  of  the  arm,  or  teres  major. 

4.  Long  alidii'tor  of  the  arm. 

5.  Short  abductor  of  the  arm. 


B.   BONES   OF   THE   ARM. 

Humerus. 
The  humerus  gives  insertion  to  twenty-four  muscles : — 

a.  By  its  superior  extremity,  to  the — 

1.  Supraspinatus. 

2.  Subspinatus. 

3.  Subscapularis. 

4.  Small  scapulo-humeralis. 

5.  Sterno-trochineus,  or  deep  pectoral. 

6.  Panniculus  carnosus. 

b.  By  its  body,  to  the — 

1.  Long  abductor  of  the  arm. 

2.  Short  abductor  of  the  arm. 

3.  Coraco-brachial  muscle  by  two  points. 

4.  Adductor  of  the  arm,  or  teres  mnjor. 

5.  Short  flexor  of  the  fore-arm,  or  anterior  brachial  muscle. 

6.  Short  extensor  of  tlie  fore-arm. 

7.  Middle  extensor  of  the  fore-arm. 

8.  Small  extensor  of  the  fore-arm,  or  anconeus  muscle. 

9.  Anterior  extensor  of  the  metacarpus. 

10.  Anterior  extensor  of  the  phalanges. 

11.  Great  dorsal  muscle. 

12.  Mastoido-humeralis  muscle. 

13.  Sterno-humeralis,  or  superficial  pectoral  muscle. 

c.  By  its  inferior  extremity,  to  the — 

1.  Anterior  extensor  of  the  phalanges. 

2.  External  flexor  of  the  metacarpus. 

3.  Oblique  flexor  of  the  metacarpus. 

4.  Internal  flexor  of  Ihe  metacarpus. 

5.  Superficial  flexor  of  the  phalanges,  or  perforatus. 

6.  Deep  flexor  of  the  phalanges,  or  perforans. 


C.   BOXES   OF   THE  FORE-ARM. 

I.  Radius. 
The  radius  gives  insertion  : — 

a.  By  its  upper  extremitij,  to  the — 

1.  Long  flexor  of  the  fore-arm,  or  brachial  biceps. 

2.  Anterior  extensor  of  the  phalanges. 

3.  Lateral  extensor  of  the  phalanges. 

b.  By  its  body,  to  the — 

1.  Short  flexor  of  the  fore-arm.  or  anterior  brachial  muscle. 

2.  Oblique  extensor  of  the  metacarpus 

3.  Anterior  extensor  of  the  phalanges. 

4.  Lateral  extensor  of  tlie  phalanges. 

5.  Deep  flexor  of  the  phalanges,  or  perforans. 


GEXERAL  TABLE  OF  MUSCULAR  INSEETJOXS.  321 

II.  Ulna. 
The  ulna  gives  insertion  : — 

o.   By  its  upper  extremity  (olecranon)  to  the — 

1.  Long  extensor  of  the  fore-arm. 

2.  Large  extensor  of  the  fore-arm. 

3.  Short  extensor  of  the  fore-arm. 

4.  Middle  extensor  of  the  fore-arm. 

5.  Small  extensor  of  the  fore-arm,  or  anconeus  muscle. 

6.  Oblique  flexor  of  the  metacarpus. 

7.  Deep  flexor  of  the  phalange;?,  or  perforans. 

b.  By  its  body,  to  the — 

1.  Short  flexor  of  the  fore-arm,  or  anterior  brachial  muscle. 

2.  Lateral  extensor  of  the  phalanges. 

D.   BOXES   OF   THE  CARPUS. 

Supercarpcd  Bone. 
The  supercarpal  bone,  the  only  bone  of  the  carpus  whicli  Las  muscular 
attachments,  gives  insertion  to  two  muscles : — 

1.  External  flexor  of  the  metacarpus,  or  posterior  ulnar, 

2.  Oblique  flexor  of  the  metacarpus. 

E,  BOXES   OF   THE   METACARPUS. 

I.  Princijml  Metacarpal. 
The  principal  metacarpal  gives  insertion  to  a  single  muscle  : — 
By  its  superior  extremity,  to  the — 

Anterior  extensor  of  the  metacarpus. 

II.  External  Eudimentary  Metacarpal. 

This  gives  insertion  to  a  single  muscle  : — 

External  flexor  of  the  metacarpus,  or  posterior  ulnar. 

III.  I)iternal  Eudimentary  Metacarpal. 
This  gives  insertion  to  two  muscles : — 

1.  Oblique  extensor  of  the  metacarpus. 

2.  Internal  flexor  of  the  metacarpus,  or  groat  palmar  muscle. 

F.  BOXES  OF  THE  DIGITAL  REGION. 

I.  First  Phalanx. 
This  gives  insertion  to  two  muscles : — 

1.  Anterior  extensor  of  tlie  phalanges. 

2.  Lateral  extensor  of  the  phalanges. 

II.  Second  Phalanx. 
This  gives  insertion  to  two  muscles : — 

1.  Anterior  extensor  of  the  phalanges. 

2.  Superficial  flexor  of  the  phalanges. 

III.  Tliird  Phalanx. 

The  third  phalanx,  or  os  pedis,  gives  insertion  to  two  muscles : — 

1.  Anterior  extensor  of  the  phalanges. 

2.  Deep  flexor  of  the  phalanges. 


322  THE  MUSCLES. 

5.  Abdominal  Limb. 

a.  bones  of  the  haunch. 
Coxa, 


The  coxa  gives  insertion : — 

a.  By  the  ilium,  to  the — 

1.  Ilio-spinalis  muscle. 

2.  Iliac  (psoas)  muscle. 

3.  Small  psoas  muscle. 

4.  Square  muscle  of  the  loins. 

5.  Ischio-coccygeal  muscle. 

6.  Great  oblique  muscle  of  the  abdomen. 

7.  Small  oblique  muscle  of  the  abdomen. 

8.  Transverse  muscle  of  the  abdomen  ( through  the  medium  of  the  crural 

arch). 

9.  Middle  gluteal  muscle. 

1 0.  Deep  gluteal  muscle. 

11.  Muscle  of  the  fascia  lata. 

12.  Anterior  rectus  muscle  of  the  thigh. 

13.  Anterior  gracilis  muscle. 

14.  Internal  obturator. 

b.  By  tlie  jnibis,  to  the — 

1.  Great  oblique  muscle  of  the  abdomen. 

2.  Small  oblique  muscle  of  the  abdomen. 

3.  Great  rectus  muscle  of  the  abdomen. 

4.  Transverse  muscle  of  the  abdomen  (through  the  medium  of  the  crural 

arch). 

5.  Short  adductor  of  the  leg. 

6.  Pectineus  muscle. 

7.  Small  adductor  of  the  thigh. 

8.  External  obturator  muscle. 

9.  Internal  obturator  nmscle. 

c.  By  the  ischium,  to  the — 

1.  Superficial  gluteus  muscle. 

2.  Long  vastus  muscle, 

3.  Semitendinous  muscle. 

4.  Semimembranous  muscle. 

5.  Short  adductor  of  the  leg. 

<;.  Great  adductor  of  the  thigh. 

7.  Square  crural  muscle. 

8.  External  obturator  muscle. 

9.  Internal  obturator  muscle. 
10.  Gemelli  muscles  of  the  pelvis. 


B.   BONES  OF  THE  THIGH, 

Femur. 
The  femur  gives  insertion : — 

a.  By  its  upper  extremity,  to  the — 

1.  Great  psoas  muscle. 

2.  Iliac  psoas  muscle. 

3.  Middle  gluteus  muscle. 

4.  Deep  gluteus  muscle. 

5.  External  obturator  muscle. 

6.  Internal  obturator  muscle. 

7.  Gemelli  muscles  of  the  pelvis. 

b.  By  its  body,  to  the — 

1.  Superficial  gluteus  muscle. 

2.  Fascia  lata. 


GENERAL  TABLE  OF  MTSCULAE  INSERTIONS.  323 

3.  External  vastus  muscle  (crural  triceps). 

4.  Internal  vastus  muscle  (crmal  triceps). 

5.  Anterior  gracilis  muscle. 

6.  Long  vastus  muscle. 

7.  Peetineus  muscle. 

8.  Small  adductor  of  the  thigh. 

9.  Great  adductor  of  the  thigh. 

10.  Square  crural  muscle. 

11.  Gastrocnemii  muscles. 

12.  Superficial  flexor  of  the  phalanges,  or  perforatus. 

c.  By  its  inferior  extremity,  to  the — 

1.  Semimembranous  muscle. 

2.  Great  adductor  of  the  thigh. 

3.  Anterior  extensor  of  the  phalanges. 

4.  Flexor  of  the  metatarsus. 

5.  Popliteus  muscle. 

C.  BONES  OF  THE  LEG. 
I.   Tibia. 
The  tibia  gives  insertion  : — 

a.  By  its  upper  extremity,  to  the — 

1.  Flexor  of  the  metatarsus. 

2.  Soleus  muscle. 

3.  Deep  flexor  of  the  phalanges,  or  perforans. 

4.  Oblique  flexor  of  the  phalanges. 

5.  Long  adductor  of  the  leg  '^through  the  medium  of  the  internal  patellar 

ligament). 

b.  By  its  hochj,  to  the — 

1.  Long  vastus  muscle. 

2.  Semitendinous  mutcle. 

3.  Sl)ort  adductor  of  the  leg  (in  common  with  the  long  adductor) 

4.  Flexor  of  the  metatarsus. 

5.  Popliteus  muscle. 

6.  Deep  flexor  of  the  phalanges  or  perforans. 

II.  Fibula. 
The  fibula  gives  insertion  to  two  muscles : — 

1.  Lateral  extensor  of  the  phalanges. 

2.  Deep  flexor  of  the  phalanges  or  perforans. 

III.  Patdla. 
The  patella  gives  insertion  to  five  muscles  : — 

1.  Fascia  lata  muscle  (or  tensor  vaginae). 

2.  Anterior  rectus  of  the  thigh. 

3.  External  vastus  (crural  triceps). 

4.  Internal  vastus  (crural  triceps). 

5.  Long  vastus  muscle. 

D.   BON'ES   OF   THE   TAHSUS. 

Calcis, 
The  calcis  gives  insertion  to  the  :— 
Gastrocnemii  muscles. 

Cuboides, 
The  cuboides  gives  insertion  to  the — 
Flexor  of  the  metatarsus. 


324  THE  MUSCLES. 

Second  Cuneiform. 
This  gives  attachment  to  the — 
Flexor  of  the  metatarsus. 

E.   BONES   OF  THE  METATARSUS. 

The  principal  metatarsal  gives  insertion  to  the — 
Flexor  of  the  metatarsus. 

F.  BONES  OF  THE   FOOT. 
I.  First  Fhalanx. 
The  first  phalanx  gives  insertion  to  one  muscle,  the — 

Anterior  extensor  of  the  phalanges. 

II.  Second  Phalanx. 

The  second  phalanx  gives  insertion  to  two  muscles : — 

1.  Anterior  extensor  of  the  phalanges. 

2.  Superficial  flexor  of  the  phalanges,  or  perforatus. 

III.  Tliird  Phalanx. 

The  third  phalanx  gives  insertion  to  two  muscles : — 

1.  Anterior  extensor  of  the  phalanges. 

2.  Deep  flexor  of  the  phalanges,  or  perforans. 


BOOK  IT. 
The  Digestive  Apparatus. 

CHAPTER  I. 

GENEUAL   CONSIDERATIONS   ON  THE   DIGESTIVE   APPARATUS. 

We  have  considered  the  animal  as  a  machine  composed  of  various 
levers  and  susceptible  of  various  movements ;  but  it  will  be  easily  under- 
stood that  the  working  of  this  machine  will  cause  the  wear  or  decomposition 
of  the  molecules  which  enter  into  the  construction  of  its  organs,  and 
that  these  springs  or  animated  wheels  demand  for  their  maintenance  an 
incessant  supply  of  new  materials,  destined  to  repair  their  continual  losses. 
Animals,  therefore,  are  under  the  necessity  of  taking  aliment,  from  which 
they  extract  those  reparative  principles  which,  distributed  to  all  the  organs, 
are  assimilated  into  their  proper  substance. 

The  organs  in  wliich  this  work  of  preparation  and  absorption  of  the 
organisable  material  is  carried  on  are  collectively  named  the  digestive 
apparatus :  one  of  the  most  important  of  those  which,  as  we  will  see,  suc- 
cessively complicate  and  perfect  the  animal  machine.  This  apparatus  does  not, 
properly  speaking,  constitute  an  essentially  distinctive  characteristic  of 
animality,  as  there  are  animals  without  a  digestive  cavity  ;  but  it  is  yet  one 
of  the  most  salient  attributes,  for  the  exceptions  just  mentioned  are  ex- 
tremely rare.  Considered  in  the  vertebra  ta,  this  apparatus  appears  as  a 
long  tube,  most  frequently  doubled  on  itself  many  times,  bulging  at  intervals, 
and  provided  along  its  course  with  several  supplementary  organs,  the 
majority  of  which  are  of  a  glandular  nature.  This  tube  extends  the  whole 
length  of  the  animal's  body,  and  opens  externally  by  two  orifices,  one  of 
these  serving  for  the  introduction  of  aliment,  the  other  for  the  expulsion  of 
the  residue  of  digestion.  These  openings  are  at  the  extremities  of  the 
alimentary  canal. 

The  conformation  of  this  apparatus  is  not  identically  the  same  in  all 
the  individuals  composing  the  sub-kingdom  of  vertebrata ;  on  the  contrary, 
it  presents  very  numerous  varieties,  according  to  the  habits  and  mode  of 
life  of  these  individuals,  and  this  makes  its  study  interesting  from^  two 
points  of  view :  in  relation  to  the  science  of  zoology,  and  to  that  of  veterinary 
hygiene,  which  derives  from  this  study  valuaTale  indications  concerning  the 
regime  of  the  domesticated  animals. 

But  this  diversity  of  characters  does  not  suffice  to  establish  sharply- 
defined  limits  between  the  conformations  that  are  distinguished  by  it.  There 
is,  in  reality,  but  one  typical  form  for  the  digestive  apparatus,  and  the  same 
principle  prevails  in  its  construction  throughout  the  entire  series.  Thus, 
whichever  of  the  vertebrata  we  may  be  studying,  its  alimentary  tube  will 
be  found  composed  of  a  collection  of  bulging  or  tubuliform  cavities,  which 
succeed  each  other  from  before  to  behind  in  the  following  order :  the  mouth, 
pharynx,  oesophagus,  stomach,  and  intestine, 
24 


326     GENERAL  CONSIDERATIONS  ON  THE  DIGESTIVE  APrARATlfS. 

This  system  of  cavities  is  divided,  physiologically,  into  two  principal  sec- 
tions :  the  first  comprises  the  mouth,  pharynx,  and  oesophagus,  or  the  compart- 
ments in  which  are  carried  on  those  digestive  operations  termed  "  preparatory," 
because  they  prepare  the  aliment  for  the  subsequent  modifications  which 
constitute  the  essential  phenomena  of  digestion ;  the  second  section  is 
formed  by  the  stomach  and  intestine,  where  these  phenomena  take  place. 

Each  of  these  two  sections  is  furnished  in  its  course  with  annexed  organs, 
which  are  present  in  the  majority  of  vertebrata ;  these  are  the  salivary  glands 
for  the  cavities  of  the  first  category,  and  the  liver,  pancreas,  and  spleen  for 
those  of  the  second. 

In  considering  the  general  position  of  these  various  parts,  principally 
in  mammals  and  birds,  it  is  found  that  the  first  section  of  the  digestive 
canal  and  its  appended  organs  is  lodged  beneath  the  upper  jaw  and  the 
base  of  the  cranium,  and  under  the  cervico-thoracic  portion  of  the  vertebral 
column.  The  second  section,  with  its  annexes,  occupies  the  great  abdominal 
cavity. 

In  Man,  these  two  sections  are  divided  into  supra-diapliragmatic  and 
infra-diaphragmatic,  because  of  their  relations  to  the  diaphragm. 

The  constituent  parts  of  the  first  category  might  be  termed,  by  reason 
of  their  functions,  the  preparatory  organs  of  the  digestive  apparatus  ;  and 
those  of  the  second,  or  abdominal  portion,  the  essential  organs  of  digestion. 

These  various  organs,  with  those  composing  the  respiratory  and  genito- 
urinary apparatus,  have  received  the  name  of  viscera,  and  the  term  splanch- 
nology is  often  given  to  that  branch  of  anatomy  devoted  to  their  study.^ 

These  new  organs  differ  so  notably  from  those  already  described,  that  it 
is  necessary  to  enter  into  some  generalities  as  to  their  nomenclature,  dis- 
position, form,  structure,  and  physical  or  chemical  characteristics. 

Nomenclaiure  in  splanchnology  does  not  rest  on  any  scientific  basis  ;  the 
name  of  organs  being  sometimes  derived  from  their  form — as  tlie  amygdalce  ; 
sometimes  from  their  direction — rectum  ;  sometimes  also  from  their  uses — the 
oesophagus,  salivary  glands  ;  their  length — duodenum  ;  the  names  of  the  anato- 
mists who  have  described  them — the  duct  of  Stenon,  Fallopian  tube;  and 
at  times  these  names  are  purely  conventional,  as  the  spleen. 

They  are  distinguished  as  hollotv  and  solid  organs. 

1.  The  hollow  organs  have  a  more  or  less  considerable  cavity,  capable  of 
being  increased  or  diminished,  but  they  are  not  of  a  definite  shape  or 
volume.  Their  consistency  varies  with  their  state  of  plenitude  or  vacuity, 
and  they  are  single  or  double,  symmetrical  or  asymmetrical. 

In  all  cases,  the  walls  of  the  hollow  organs  are  comj)osed  of  two  or  more 
membranes  which  we  will  now  describe  in  a  general  manner. 

a.  The  innermost  is  called  the  mucous  membkane,  because  of  the  mucus 
with  which  its  free  surface  is  always  covered.  It  is  made  continuous  with  the 
skin  at  the  natural  openings ;  and  from  its  similarity  of  organisation  it  has 
been  named  the  internal  or  re-entering  skin,  or  internal  tegumentary  membrane. 

•  The  name  fif  viscera  (from  vescor,  I  nourish )  lias  been  given  to  the  organs  wliich  aid  in 
nutrition,  and  the  term  Splanchnology  (from  (riryaLxvov,  a  visciis  or  intestine)  lias  been 
bestowed  on  that  division  of  anatomy  whicli  treats  of  these  organs  Splanclmology,  thus 
understood,  comprises  the  study  of  the  digestive,  respiratory,  urinary,  and  circulatory 
apparatus.  But  the  description  of  the  latter  forms  a  separate  category,  designated  in  the 
language  of  the  schools  by  the  name  of  Angioloriy.  On  tlie  other  hand,  however,  several 
authorities  include  in  Splanchnology  the  organs  of  generation,  and  others  even  add  the 
organs  of  sense.  There  is,  therefore,  no  accord  in  the  limits  given  to  the  detinition  of 
Splanchnology  ;  and  this  being  the  case,  we  have  thought  it  best  to  omit  this  expression 
and  the  distinction  it  seeks  to  establish. 


GENERAL  CONSIDERATIONS  ON  THE  DIGESTIVE  APPARATUS.    327 


Ficr.  143. 


A  mucous  membrane  comprises  a  superficial  or  epitJielial  layer  and  a 
deep  portion  which  constitutes  the  derm  or  chorion  [corium). 

The  epitheluim  is  a  very  thin,  inert  pellicle,  entirely  comiiosed  of 
epithelial  cells  united  by  an  almost  insignificant  quantity  of  amorphous 
matter  [blastema).  The  cells  are  flat  or  polygonal, 
round  or  cylindi'ical,  polyhedral,  or  very  irregular 
in  shape.  In  consequence  of  these  diverse  forms, 
there  is  pavement  (or  squamous),  spherical  (or 
spheroidal),  and  cylindrical  or  conical  (or  columnar) 
epithelium.  If  the  cells  are  furnished  with  small 
filiform  appendages,  named  vibratile  cilia,  the 
epithelium  is  then  designated  ciliated.  AVhen  the 
cells  are  arranged  in  a  single  layer  on  the  surface  squamous  epitheliuji  fkom 
of  the  corium,  the  epithelium  is  said  to  be  simple  ;  the  mouth. 

it  is  stratified  when  the  cells  are  arranged  in  strata  The  large  scale  is  mao;nified 
upon  each  other.  In  stratified  epithelium,  the  310  diameters,  and  exhibits 
shape  of  the  cells  is  not  the  same  on  the  sm-face  ^  nucleus  with  nucleolus  in 
and  beneath  it,  and  it  is  named  after  the  form  of  ^he  centre,  and  seconlary 
^.  ,>    •   1  1  nucleated  cells  forming  the 

the  superficial  layer.  _  body  of  the  scale. 

The  mucous  derm  or  corium  corresponds  to  that 
of  the  skin,  as  the  epithelium  corresponds  to  the 
epidermis.    It  is  composed  of  connective  ( or  areolar) 
tissue,  whose  thickness,  elasticity,  vascularity,  and 
sensibility  varies  with  the  situation  and  the  func- 
tion of  organs.     The  corium  is  thin  and   almost 
destitute  of  elastic  fibres  when  applied  to  the  bony 
walls  of  a  cavity ;    on  the  contrary,  it  is  thick, 
elastic,  and  slightly  adherent  when  it  lines  organs 
which,  like  the  stomach,  oesophagus,  and  intestines, 
are  capable  of  increasing  or  diminishing  in  capacity. 
The    fasciculi    of    the    connective   tissue    in   the 
deeper  layers  of  the  corium  are  loosely  united, 
but  nearer  the  surface  they  lie  closer ;  some- 
times they  form,  under  the  epithelium,  an 
amorphous   surface-layer,  the  basement  (or 
limitary)  membrane.    The  sub-epithelial  face 
of  the  corium  is  scarcely  ever  smooth,  but 
otfers  minute  prolongations  named  villositiesor 
Dapillce,  which  are  very  varied  in  their  form  columnar     ciliated     epithelium  : 
and  volume,  and  is  more  or  less  marked  by  magnified  310  diametep.s. 

depressions  designated   follicles.      The  villi       a,  Nucleated  cells  resting  on  their 

1        _  J    _  ii      1         '       i    T  smaller  extremities ;  6,  Cilia, 

are  observed  on  the  deep-seated  mucous  mem-  '    ' 

braues  ;  they  are  mure  particularly  the  vascular  and  absorbent  organs.  The 
papillae  are  found  towards  the  natural  apertures,  and  are  rich  in  nerves  ;  they 
are  more  especially  the  organs  of  sensibility.  The  follicles,  lined  by  one 
or  other  form  of  cell,  are  exclusively  organs  of  secretion. 

h.  Tlie  second  membrane  met  with  in  the  walls  of  the  hollow  organs  is  of 
a  muscular,  and  sometimes  of  a  cartilaginous  nature.  The  muscular  mem- 
brane is  formed  of  unstriped  fibres  whose  slow  contraction  is  involuntary. 
In  certain  organs — those  adjoining  the  natural  apertures — the  unstriped 
fibres  are  replaced  by  strijied,  which  are  under  the  influence  of  the  will, 
or  have  the  same  physiological  properties  as  the  smooth  fibres,  as  in  the 
oesophagus. 


COLUMNAR   epithelium. 

1,  Nucleus  of  the  cell ;  2, 
Jlembrane  of  the  cell  raised 
from  its  contents  by  the 
absorption  of  water. 

Fig.  145. 


328     GENERAL  CONSIDERATIONS  ON  THE  DIGESTIVE  APPARATUS. 


(JJnstriped  ov  smooth  bands  of  muscles  are  composed  of  long  fusiform  cells 
with  staff-shaped,  elongated  nuclei,  the  cells  varying  from  l-1125th  to  l-50th 
of  an  inch  in  length,  and  from  l-5025th  to  l-1125th  of  an  inch  in  breadth.) 

c.  When  the  organs  are  lodged  in  one  of 
the  great  splanchnic  cavities,  such  as  the 
chest  or  abdomen,  they  have  a  third  mem- 
brane— a  serous  layer,  which  lines  the  cavity, 
and  is  reflected  around  the  viscera  contained 
in  it,  so  as  to  envelop  them  more  or  less 
completely.  This  layer  has,  therefore,  an 
adherent  face,  ai)plied  either  against  the  walls 
of  the  cavity  or  the  external  surface  of  the 
splanchnic  organs  ;  and  a  free  face  always  in 
contact  with  itself. 

A  serous  membrane  is  composed  of  two 
layers :  a  deep,  connective  portion, analogous  to 
the  mucous  corium  :  and  a  superficial,  which  is 
only  pavement  epithelium.  The  free  surface 
of  this  epithelium  is  perfectly  smooth,  and 
lubricated  by  a  limpid  serosity  to  facilitate  the 
gliding  of  the  parts  the  membrane  covers. 
(The  epithelium  is  a  simple  tesselated  layer 
of  flattened  and  polygonal  nucleated  cells, 
about  1— 1200th  of  an  inch  in  diameter). 

2.  The  solid  organs  are  either  contained 
in  the  splanchnic  cavities  or  situated  outside 
them,  in  the  midst  of  connective  tissue,  which, 
in  condensing  around  them,  often  forms  a 
fibrous  covering. 

Like  the  hollow  organs,  they  are  single — 
spleen,  liver;  or  in  pairs — Mdneys ;  and 
symmetrical  or  asymmetrical.  They  are 
retained  in  their  situation  by  their  vessels 
and  nerves,  by  adherence  to  the  neighbouring 
organs,  or  by  particular  serous  attachments. 

With  the  exception  of  the  lungs  of  animals 
that  have  respired,  all  the  solid  organs  have  a 
density  greater  than  water.  Their  iceiglit  and 
volume  oifer  numerous  difierences,  which  are 
individual  or  relating  to  the  species  to  which 
they  belong.  Nevertheless,  each  organ  pos- 
sesses a  certain  volume  and  weight  which 
might  be  termed  physiologic  ;  when  the  organ 
is  above  or  below  this  average,  we  are 
authorized  in  saying  that  it  is  in  a  patho- 
logical condition. 

Organs  are  more  or  less  round  inform, 
and  their  surface  is  traversed  by  a  variable 
number  of  furrows  which  indicate  their 
division  into  lobes  or  lobules. 


COXICAL  VILLI  ON  MUCOUS  MEM- 
BRANE OF  SMALL  INTESTINE; 
MAGNIFIED   19    DIAMETERS. 

a,  Zone  of  follicles  surrouudiug  a  soli- 
tary gland ;  b,  Apertures  of  simple 
follicles. 

Fig.  147. 


FUSIFORM   CELLS   OF   SMOOTH 
MUSCULAR   FIBRE. 

a,  Two  cells  in  their  natural  state,  one  showing  the  staff-shaped  nucleus ; 
with  its  nucleus,  c,  brought  distinctly  into  view  by  acetic  acid. 


6,  A  cell 


GENERAL  COXSIDEEATIOXS  ON  TEE  DIGESTIVE  ATFABATVS.    329 

Their  colour  is  diverse ;  they  may  be  very  ^^\q— parotid  gland ;  or  very 
dark — liver,  spleen ;  or  uniform,  or  of  different  shades  :  varieties  which  are 
most  frequently  due  to  the  mode  of  distribution  of  the  vessels,  or  to  the 
jiresence  of  certain  anatomical  elements.  The  colour  of  organs  is  not  always 
the  same  in  the  deeper  parts  and  at  the  surface,  especially  Avhcn  they  are 
enveloped  by  a  thick,  opaque  membrane  ;  for  instance,  the  testicle.  Lastly, 
the  coloration  is  less  intense  after  death  than  during  life,  and  particu- 
larly if  the  animal  to  which  the  organs  belonged  has  been  killed  by  effusion 
of  blood. 

The  consistence  of  organs  depends  on  their  internal  fomiation  and  the 
nature  of  their  constituent  elements ;  there  are  soft  organs,  such  as  the 
lungs,  and  resisting  organs,  as  the  testicles.  As  a  general  rule,  the  consistence 
of  organs  diminishes  after  jnitrefaction  has  set  in. 

Cohesion  is  the  resistance  that  organs  offer  to  the  forces  which  tend  to 
tear  them  ;  it  depends  upon  the  texture  of  the  organs,  and  the  more  or  less 
abundance  in  their  interior  of  fibrous  and  elastic  tissue.  Cohesion  is  very 
different  from  consistency ;  thus,  such  an  organ  as  the  lung  may  be  easily 
compressed,  but  may  be  very  difficult  to  tear. 

If  organs  are  examined  with  regard  to  their  structure,  it  will  be  observed 
that  all  have  a  thin  or  thick  fibrous  casing  which  throws  septa  into  their 
interior,  and  which  support  their  proper  tissue  ;  this  "tissue  varies  with  the 
nature  of  the  organs.  It  wall  also  be  found  that  they  are  traversed  by  a 
more  or  less  considerable  number  of  blood-vessels — arteries  and  veins.  These 
vessels  expand  into  a  capillary  network,  whose  meshes  have  a  shape  closely 
allied  to  that  of  the  elements  of  the  proper  tissue.  The  number  and  volume 
of  the  vessels  of  an  organ  give  an  exact  idea  of  its  importance,  and  of  the 
activity  of  the  physiological  phenomena  taking  place  in  it.  Finally,  into 
the  composition  of  organs  enter  supei-ficial  and  deep  lymphatic  vessels  and 
nerves,  which  generally  follow  the  arteries.  The  nerves  show  in  their  course 
small  ganglionic  enlargements  ;  their  mode  of  termination  is  most  frequently 
unknown. 

Glands  are  organs  of  a  particular  construction,  whose  function  it  is  to 
eliminate  certain  fluid  or  solid  products  of  the  economy. 

The  very  simple  (or  tubular)  glands  consist  of  a  straight  or  convoluted 
tube,  or  of  a  small  vesicular  cavity  opening  on  a  tegumentary  membrane,  and 
are  lined  on  their  inner  face  by  one  or  more  layers  of  cells.  As  examples, 
there  may  be  cited  the  tubular  glands  of  the  intestines  and  stomach,  the 
racemose  (or  lobulated)  glands  of  Briinner,  and  the  solitary  follicles  of 
the  intestine. 

But  there  are  also  conglomerate  glands,  organs  more  complex,  though 
belonging  to  the  same  groups  as  the  simple  glands.  These  are  glands 
composed  of  tubes,  like  the  kidneys  and  testicles ;  racemose  glands,  such  as 
the  salivary  glands  and  pancreas;  a  network  of  glands,  like  the  liver;  or 
glands  witlti  closed  follicles,  such  as  the  thyroid.  In  these  the  essential 
anatomical  element^ — the  polygonal,  cylindrical,  or  spherical  gland-cell — 
is  situated  on  the  inner  face  of  a  tube,  as  in  the  Mdney,  or  a  demi-vesicle, 
as  is  seen  in  the  pancreas,  or  deposited  without  any  order  in  the  meshes  of 
a  plexus  of  canaliculi,  as  occurs  in  the  liver. 

The  conglomerate  glands  arc  provided  with  a  common  excretory  canal, 
that  commences  in  their  mass  by  a  great  number  of  arborescent  ramifications. 

The  walls  of  this  canal  are  composed  of  an  elastic,  and  sometimes  con- 
tractile, conjunctival  membrane,  covered  on  its  inner  face  by  an  epithelium, 
which  may  or  may  not  be  of  the  same  character  as  that  of  the  gland. 


330  THE  DIGESTIVE  APPARATUS  IN  3IA3IMALIA. 

For  a  long  time  there  have  been  classed  as  glands  certain  organs — such 
as  the  si^leen  and  thymus  body— without  excretory  ducts,  and  having  only 
remote  analogies  to  glands.  The  function  of  these  organs  is  but  little  known  ; 
though  as  they  are  always  abundantly  supplied  with  blood-vessels,  and  as 
they  are  therefore  believed  to  have  connections  with  the  vascular  system, 
they  have  been  named  vascular  blood-glands. 

This  is  the  limit  to  which  the  generalities  relating  to  the  viscera  that 
form  the  object  of  splanchnology  must  be  confined.  We  will  now  pass  to 
the  description  of  the  digestive  apparatus  in  mammals,  and  which  consists, 
as  mentioned  above,  of  a  series  of  enlarged  or  tubuliform  cavities,  to  which 
are  annexed  the  glandular  organs  designated  the  liver  pancreas,  and  spleen. 


CHAPTER  II. 

THE  DIGESTIVE  APPAEATUS  IN  MAMMALIA. 
We  will  study,  successively :  1,  The  preparatory  organs,  which  include 
the  mouth,  the  salivary  glands  annexed  to  that  cavity,  the  pharynx,  and 
the  oesophagus  ;  2,  Tlie  essential  organs,  comprising  the  stomach  and  intestine, 
and  their  annexes— ihe  liver, pancreas,  and  spleen;  witliihQ abdominal  cavity, 
which  contains  and  protects  these  organs. 

Article  I. — Preparatouy  Organs  op  the  Digestive  Apparatus. 

THE   BIOUTH. 

The  mouth,  the  first  vestibule  of  the  alimentary  canal,  is  a  cavity 
situated  between  the  two  jaws,  elongated  in  the  direction  of  the  larger  r.xis 
of  the  head,  and  pierced  by  two  openings :  an  anterior,  for  the  introduction 
of  food,  and  a  posterior,  by  which  the  aliment  passes  into  the  pharynx. 

The  mouth  should  be  studied  in  six  principal  regions:  1,  The  lips, 
which  circumscribe  its  anterior  opening;  2,  The  c7«eeA-s,  forming  its  lateral 
walls ;  3,  The  palate,  which  constitutes  its  roof  or  superior  wall ;  4,  The 
tongue,  a  muscular  appendage,  occupying  its  inferior  wall ;  5,  The  soft  palate 
(velum  pendulum  palati),  a  membranous  partition  situated  at  the  posterior 
extremity  of  the  buccal  cavity,  which  it  separates  from  the  pharynx,  and 
concurs  in  the  formation,  by  its  inferior  border,  of  the  isthmus  of  the  fauces, 
or  posterior  opening  of  the  mouth ;  6,  The  dental  arches  fixed  on  each  jaw. 

We  will  study  each  of  these  regions  in  particular,  before  passing  to  the 
examination  of  the  mouth  in  general. 

Preparation. — The  whole  of  the  mouth  oupjht  to  be  examined  iu  an  antero-posterior 
and  vertical  section  of  the  head,  as  in  figure  152. 

1.  The  Lips.     (Fig.  110.) 

These  are  two  membranous  movable  folds,  placed  one  above,  the  other 
below,  the  anterior  opening  of  the  mouth,  which  they  circumscribe.  There 
is,  consequently,  a  superior  and  an  inferior  lip,  united  at  each  side  by  a 
commissure. 

Each  lip  offers  for  study  an  external  and  internal  face,  and  a  free  and 
an  adherent  border. 

m\Q  external  face  is  convex,  and  presents,  on  the  median  line:  in  tlie 
upper  lip,  a  slight  projection  which  divides  it  into  two  lateral  lobes ;  iu  the 


THE  MOUTH.  331 

inferior  lip,  and  altogether  posteriorly,  the  single  prominence  named  the 
tuft  of  the  chin.  This  tace,  formed  by  tlie  skin,  is  garnished  with  fine,  short 
hairs,  amongst  which  may  be  remarked  long,  coarse  bristles,  whose  bulbs 
are  implanted  perpeudicularly  in  the  integument,  and  pass  beyond  its  deep 
surface,  to  be  lodged  in  the  subjacent  muscular  tissue.  These  pilous 
tentacles  ought  to  be  considered  as  veritable  tactile  organs,  as  several 
sensitive  nervous  twigs  penetrate  to  the  bottom  of  their  follicles. 

The  internal  face,  constituted  by  the  buccal  mucous  membrane,  and 
moulded  on  the  incisor  teetli,  is  concave,  smooth,  rose-coloured,  and  often 
stained  with  black  spots.  In  the  superior  lip,  particularly,  may  be  remarked 
numerous  orifices  opening  on  the  summits  of  three  small  papillae ;  these  are 
the  openings  of  the  excretory  canals  by  which  the  labial  glands  discharge 
their  fluid  into  the  interior  of  the  mouth. 

•     The  free  border,  thin  and  sharp,  bears  the  line  of  demarcation,  which 
separates  the  two  teguments. 

The  adherent  border  is  limited,  in  the  buccal  cavity,  by  a  groove  formed 
by  the  mucous  membrane  in  its  passage  from  the  dental  arches  to  the  inner 
side  of  the  lips.  Beyond  the  mouth  it  is  not  indicated  by  any  peculiarity 
of  structure  or  arrangement,  the  skin  being  continued  directly  from  the 
neighbouring  parts  on  the  lips. 

The  commissures  mark,  on  each  side,  the  point  of  reunion  between  the 
free  border  of  the  two  lips.  They  are  rounded  in  Solipeds,  and  otfer 
nothing  remarkable  otherwise. 

Structtjke. — Each  lip  is  composed  of  two  tegumentary  layers  :  one 
cutaneous,  the  other  mucous,  between  which  is  found  muscidar  tissue  and 
glands,  and  the  general  elements  of  every  organisation — vessels  and  nerves. 

1.  Teijumentary  layers. — Thesl-in  adheres  closely  to  the  subjacent  tissues, 
and  apart  from  the  chaiacters  ali-eady  indicated,  there  is  nothing  more  to  be 
said  at  present,  with  regard  to  its  disposition,  as  it  will  be  studied  more 
completely  with  the  organs  of  sense.  With  regard  to  the  mucous  membrane, 
it  may  be  remarked  that  its  derm  is  thick  and  dense,  and  lies  on  a  layer  of 
salivary  glands ;  that  it  is  provided  with  simple  conical  jiai^illse,  and  is 
covered  by  stratified  pavement  epithelium.  (It  is  sometimes  streaked  with 
pigment.) 

2.  Muscles. — These  are:  the  labial  or  orbicularis,  the  sphincter  of  the 
buccal  apertui-e,  and  common  to  the  two  lips ;  in  the  ujjper  lip,  the  aponeu- 
i-otic  expansion  of  the  supermaxillo-labialis,  the  musculo-fibrous  tissue 
which  separates  this  expansion  from  the  cutaneous  integument,  and  the 
terminal  insertion  of  the  sujiernasalis-labialis  and  the  great  supermaxillo- 
nasalis  ;  in  the  inferior  lip,  the  tuft  of  the  chin  and  its"  suspensory  muscles — 
the  posterior  intermediates  (levatores  menti).  All  these  muscles  having  been 
studied  in  detail  in  the  Myology  (page  217),  there  is  no  necessity  for  their 
being  again  described. 

3.  Lcibial  glandules. — These  form  an  almost  continuous  laver  between 
the  mucous  membrane  and  the  labial  muscle.  They  are  little  secretory 
organs,  similar  in  their  structure  and  uses  to  the  salivary  glands,  and  will 
be  described  when  these  come  under  notice. 

4.  Vessels  and  nerves. — The  blood  is  carried  to  the  lips  by  tlie  palato- 
Idbial,  and  the  superior  and  inferior  coronary  arteries.  It  is  returned  to  tlie 
heart  by  the  satellite  veins  of  the  two  last  vessels.  The  lymphatics  are  very 
numerous,  and  pass  to  the  glands  between  the  branches  of  the  lower  jaw. 
The  nerves  are  of  two  kinds :  the  motor,  which  are  given  oft"  from  the  facir,! 
nerve,  and  are  distributed  in  the  muscular  tissue  of  the  lips  to  cause  itj 


332  THE  DIGESTIVE  AFFABATVS  IN  MAMMALIA. 

contraction;  the  sensitive  nerves,  which  are  furnished  by  the  maxillary 
branches  of  the  fifth  cncejihalic  pair,  are  distinguished  by  their  number  and 
considerable  volume,  and  are  nearly  all  buried  in  the  cutaneous  integument, 
to  which  they  communicate  an  exquisite  sensibility. 

Functions. — The  lips  serve  for  the  prehension  of  solid  and  liquid  food ; 
they  retain  it  in  the  mouth  after  its  introduction  thereto,  and  likewise  pre- 
vent the  escape  of  the  saliva.  They  ought  also  to  be  regarded,  especially 
the  upper  lip,  as  very  delicate  organs  of  touch. 

2.  The  Cheeks.     (Fig.  110.) 

These  are  two  membranous  walls,  which  inclose  the  mouth  laterally. 
In  the  interior  of  the  buccal  cavity  they  are  limited :  behind,  by  the 
posterior  pillars  of  the  tongue ;  in  front,  by  the  lips,  with  which  they  are 
confounded  around  the  commissures;  above  and  below,  by  the  groove 
formed  by  the  gingival  mucous  membrane,  where  it  is  reflected  from  the 
molar  arches  on  to  the  cheeks. 

The  greatest  diameter  of  the  cheeks  is  antero-posterior,  like  that  of  the 
cavity  it  incloses.  Their  vertical  diameter  is  very  narrow,  esi^ecially 
behind ;  in  the  anterior  region,  however,  it  can  assume  a  certain  amplitude 
by  the  separation  of  the  jaws. 

Structure. — The  cheeks  are  formed  by  the  buccal  mucous  membrane, 
external  to  which  we  find  muscular  tissue  and  glands.  Vessels  and  nerves 
pass  through  these  parts  for  the  conveyance  of  nutritive  fluids,  sensibility,  or 
the  stimulus  to  contractility. 

1.  Mucous  membrane. — The  external  face  of  this  membrane  is  united  in  an 
intimate  manner  to  the  buccinator  muscle,  and  to  the  inferior  molar  glands. 
Its  free  face  presents,  at  the  level  of  the  third  superior  molar  tooth,  the 
buccal  opening  of  the  parotid  duct,  pierced  at  the  summit  of  a  variable- 
sized  tubercle.  On  the  face  of  each  dental  arcade  there  is  also  remarked  a 
linear  series  of  little  salient  points,  analogous  in  their  constitution  to  the 
large  parotideal  tubercle ;  these  are  the  excretory  orifices  of  the  molar  glands. 
Its  structure  is  the  same  as  the  mucous  meaibrane  of  the  lips.  (It  is  of  a 
pale  colour,  and  sometimes  stained  in  patches  with  pigment.) 

2.  Muscular  tissue. — This  is  the  buccinator  or  alveolo-labialis  muscle 
already  described.  It  may  be  remembered  that  the  external  face  of  this  muscle 
is  covered  by  the  masseter,  the  superior  molar  glands,  and  the  skin  ;  while  the 
internal  responds  to  the  mucous  membrane  and  the  inferior  molar  glands. 

3.  Glands. — These  are  two  masses  of  glandular  lobules,  known  as  the 
molar  glands.     They  will  be  described  with  the  salivary  glands. 

Vessels  and  nerves. — The  external  ma.xillary,  coronary,  and  buccal  arteries 
carry  blood  to  the  cheeks.  The  veins  empty  themselves  into  the  satellite 
branches  of  these  arteries. 

The  lymphatics  proceed  to  the  submaxillary  glands.  The  nerves  are  of 
the  same  kind,  and  proceed  from  the  same  source,  as  those  supplying  the  lips  : 
being  the  seventh  pair  of  encephalic  or  facial  nerves  for  the  muscular  layer, 
and  tlie  fifth  pair  for  the  integuments  (with  filaments  of  the  sympathetic  for 
the  circulation  and  the  labial  glandules). 

Functions. — The  cheeks  are  very  active  agents  in  mastication,  by  con- 
stantly pushing  the  aliment,  through  the  action  of  the  buccinator,  between  the 
dental  grinding  surfaces. 

3.  The  Palate.     (Fig.  148.) 
Freparatlon. — Separate  the  head  from  the  trunk ;  saw  through  the  branches  of  the 


TEE  MOUTH. 


333 


maxilla  above  the  angle  of  the  jaw,  and  from  the  crown  of  the  last  molar  tooth,  so  as  to 

pass  between  the  curtain  of  the'soft  palate  on  the  one  part,  ami  the  base  of  the  tongue  on 

the  other,  leaving  the  latter  organ  adlierent  to  the  lower  jaw.     TliLs  last  should  be 

removed  from  tl<e  upi)cr  jaw  hy  cutting  through  the  masseter  and  alveolo-labial  muscles, 

and  so  exposing  the  liard  and  solt  palates  in  such 

a  manner  as  to  render  easy  the  special  dissections  Fig.  148. 

necessary  for  their  study.     Tliese  dissections  are 

limited    to    the   removal  of  the  mucous   layer 

covering    the    deep     venous    network,   and    to 

the  partial  excision  of  this,  which   allows  the 

artt-ry  and   palatine   nerves   to  be  seen.     (See 

figure  148.) 

The  palate  (Jiard  jmlafe),  palatine  arch, 
or  iqjper  icall  of  the  mouth,  is  circum- 
scribed, iu  front  aud  cm  the  sides,  by  the 
superior  dental  arcade,  aud  limited,  behind, 
by  the  anterior  border  of  the  soft  palate. 
It  is  a  parabolic  surface,  exactly  repre- 
senting, in  its  configuration,  the  bony 
palate  (Fig.  21). 

On  its  face  is  remarked  a  median 
groove,  v^•hich  partitions  it  into  two  equal 
divisions,  aud  which  commences  quite  in 
front,  at  the  base  of  a  small  tubercle. 
Curved  transverse  furrows,  twenty  in 
number  (Leyh  gives  from  sixteen  to 
eighteen),  divide  each  of  these  halves 
into  an  equal  number  of  salient  arches, 
whose  concavities  are  turned  backwards, 
and  which  become  narrower  and  less 
marked  as  they  are  more  posterior. 
(These  arches  and  furrows  aid  in  retain- 
ing the  aliment  which  the  tongue  carries 
towards  the  palate  during  degh;tition). 

Structure. — The  palatine  lies  on  the 
bony  vault  formed  by  the  palatine  and 
supermaxillary  bones.  It  includes  in  its 
structure : 

1.  A  fibrous  membrane,  applied  to  the 
bone  just  mentioned,  which  sustains  a  re- 
markably-developed venous  network  con- 
stituting a  veritable  erectile  tissue,  and 
gives  to  the  palate  a  gi-eater  or  less 
degree  of  thickness,  according  to  its  state 
of  turgescence  (Fig.  148,  1). 

2.  A  mucous  layer,  extremely  adherent, 

by  its  deep  face,  to  the  preceding  tissue,  The  mucous  membrane  has  been  removed 
and  of  a  whitish  aspect  m  the  horse.  The  from  the  right  side,  and,  with  the 
COriura,    formed     entirely     of    connective       glandular  layer,  from  the  soft  palate. — 

1,  The  ridges  of  the  palatme  mucous 
membrane ;  2,  Venous  network  of  the  deep  layer,  which  is  cut  through  at  the 
external  side  to  show  the  palatine  artery,  3,  accompanied  by  the  tihiments  of  the 
palatine  nerve  ;  4,  Cartilaginous  digitation,  over  which  passes  and'  is  inflected  the  palatine 
artery ;  5,  Aponeurosis  of  the  soft  palate ;  5',  Terminal  extremity  of  the  tendon  of  the 
external  tensor  palati,  forming  by  its  expansion  the  staphvlin  aponeurosis ;  6,  The 
palato-pharyngeus  ;  7,  Circumflexus  palati ;  8,  Staphyiin  nerves. 


THE   HARD   AND   SOFT   PALATE. 


334  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

tissue,  shows  numerous  conical  papillae,  especially  at  the  posterior  part  of 
the  palate.  The  epithelium  fills  up  the  depressions  between  the  papillas;  it 
is  stratified  and  squamous,  and  remarkable  for  the  great  thickness  of  its 
horny  layer. 

3.  Two  voluminous  arfmes — Hhe palatine  ov  palato-lahials — lodged  in  the 
bony  fissures  of  the  palatine  roof.  These  arteries  proceed  parallel  to  one 
another,  and  unite  in  front  by  anastomosing  to  form  a  single  trunk,  whicli 
enters  the  incisive  foramen.  It  is  of  importance  to  know  their  disposition  in 
a  surgical  point  of  view,  as  care  ought  to  be  taken  not  to  wound  them  when 
abstracting  blood  from  the  palate.  The  blood  carried  by  these  arteries 
arrives  in  the  deep-seated  erectile  membrane,  and  is  finally  removed  by  two 
very  short  venous  trmiks,  which  do  not  jjass  with  the  palato-labial  arteries  into 
the  palatine  canal,  but  only  into  the  palatine  fissure. 

4.  Sensory  nerves  which  accompany  the  arteries,  and  are  de-rived  from  the 
superior  maxillary  branch  of  the  fifth  pair  of  cranial  nerves. 

Functions. — The  palate  has  a  passive,  but  important,  share  in  mastica- 
tion and  deglutition ;  furnishing  the  tongue,  as  it  does,  with  a  firm  basis  in 
the  movements  it  executes  when  passing  the  food  between  the  molar  teeth, 
and  in  carrying  the  alimentary  mass  backwards  to  the  pharynx. 

4.  Tie  Tongue.     (Figs.  149,  152.) 

Preparation. — 1.  By  means  of  a  strong  saw  without  a  back,  make  an  antero-posterior 
and  vertical  section  of  the  head,  in  order  to  study  the  general  disposition  of  the  tongue. 
2.  From  another  head  remove  the  lower  jaw,  leaving  the  tongue  in  the  intermaxillary 
space,  to  examine  the  external  conformation  of  the  organ  (see  the  dissection  of  the 
palate).  On  a  third  head,  kept  for  tlie  study  of  the  muscles,  these  parts  are  exposed  in  the 
following  manner :  The  masseter  is  entirely  removed,  and  the  cheek  is  detached  from  the 
lower  jaw  and  folded  back  on  the  upper  jaw ;  then  the  brunch  of  the  inferior  maxilla  is  sawn 
through  transversely,  at  first  behind,  next  in  front  of  the  molar  teeth  :  the  upper  piece  ot 
bnue  should  be  detached  by  luxating  it  behind  the  temporo-maxillary  articulation,  after  des- 
troying tlie  capsular  ligament  and  dividing  the  insertions  of  the  pterygoid  muscles.  With 
regard  to  the  inferior  piece,  it  is  reversed  in  such  a  way  as  to  put  the  line  of  the  molars 
flownwards,  and  the  inferior  border  of  the  bone  upwards  in  the  bottom  of  the  inter- 
maxillary space.  To  do  this  it  is  sufficient  to  separate  the  buccal  mucous  membrane  from 
the  mylo-hyoideus  muscle,  proceeding  from  above  to  below.  The  dissection  thus 
prepared,  serves  not  only  for  tlie  study  of  the  muscles  of  the  tongue,  but  also  for  those  of 
the  deep  salivary  glands,  the  pharynx,  larynx,  guttural  pouches,  the  nerves  and  arteries 
of  the  head,  etc.  It  is  always  better,  in  order  to  facilitatu'  this  dissection,  to  keep  the 
jaws  apart  by  fixing  a  piece  of  wood  or  bone  between  the  incisor  teeth  immediately  after 
the  death  of  the  animal. 

The  lingual  canaf. — The  inferior  wall  of  the  mouth  (or  floor),  circum- 
scribed by  the  lower  alveolar  arches,  forms  an  elongated  cavity  named  the 
lingual  canal  (or  space),  which  lodges  the  organ  designated  the  tongue.  This 
canal  occupies,  in  its  anterior  third,  the  superior  face  of  the  body  of  the  lower 
maxilla.  For  the  remainder  of  its  extent,  it  is  formed  by  a  double  groove, 
which  is  directed  to  the  bottom  of  the  mouth,  at  the  sides  of  the  tongue.  It 
exhibits  the  siihlingual  crest  and  the  harhs,  of  which  we  will  speak  when 
describing  the  sublingual  and  maxillary  glands. 

Situation  of  the  tongue.- — The  tongue  occupies  the  whole  length  of  this 
elongated  cavity,  and  thus  extends  from  the  back  part  of  the  mouth  to  the 
incisor  teeth,  lying  in  the  intermaxillary  space,  where  it  rests  on  a  species  of 
Avide  sling  formed  by  the  union  of  the  two  mylo-hyoidean  muscles. 

External  conformation.— It  is  a  fleshy  organ,  movable  in  the  interior  of 
the  buccal  cavity,  and  almost  entirely  enveloped  by  the  mucous  membi'aue 
which  lines  that  cavity.     In  Solipcds,  it  forms  a  kind  of  triangular  pyramid, 


THE  MOUTH  335 

depressed  from  side  to  side,  fixed  to  the  os  hyoides  and  tlie  inferior  maxilla 
by  the  muscles  which  form  the  basis  of  its  structure,  or  by  the  tegumentary 
membrane  which  covers  the  organ. 

Its  form  permits  it  to  be  divided,  for  the  study  of  its  external  disposition, 
into  three  faces,  three  borders,  and  two  extremities. 

The  superior  face  or  dorsum  of  the  tongue,  narrower  in  front  than  behind, 
is  roughened  by  numerous  papillae  which  give  it  a  downy  aspect.  Two  of 
these  papilla)  are  remarkable  for  their  enormous  volume,  their  lobulated 
appearance,  and  the  situation  they  occupy  at  the  bottom  of  two  excavations 
placed  side  by  side,  near  the  base  of  the  organ ;  they  are  named  the  lingual 
lacunse,  ov  foramen  csecum  of  Morgagni.  This  face  responds  to  the  palatine 
arch  or  roof,  when  the  jaws  are  together.  The  lateral  faces,  wider  in  the 
middle  of  the  tongue  than  at  its  extremities,  ai-e  limited  by  the  internal 
sui-faces  of  the  maxillary  branches.  Onthem  are  seen  several  large  papillae, 
and  the  orifices  of  some  lingual  glandulse. 

These  two  faces  are  separated  from  the  former  by  two  lateral  borders, 
which  correspond  to  the  superior  alveolar  arches  when  the  mouth  is  exactly 
closed.  With  regard  to  the  third  or  inferior  border,  its  existence  may  bo 
said  to  be  fictitious ;  by  it  enter  the  muscles  which  constitute  the  substance 
of  the  tongue,  and  it  is  by  it,  also,  that  the  organ  is  fixed  at  the  bottom  of  tbe 
intermaxillary  space. 

The  posterior  extremity,  or  base  of  the  tongue,  is  limited,  in  the  interior  of 
the  mouth,  by  a  furrow  which  borders  the  base  of  the  epiglottis.  It  presents 
a  thick,  median,  mucous  fold,  plaited  in  different  ways,  and  carried  over  the 
anterior  aspect  of  the  epiglottic  cartilage.  Two  other  folds,  more  anterior, 
also  formed  by  the  buccal  membrane,  unite  with  the  soft  palate  on  each 
side  the  base  of  the  tongue ;  these  are  the  posterior  pillars  of  the  organ 
(or  the  glosso-epiglottic  ligaments  of  Man),  and  comprise  in  their  thick- 
ness a  voluminous  collection  of  glands.  Behind  these  pillars  are  two 
triangular  spaces,  included  between  the  velum  pendulum  palati  and  the 
base  of  the  tongue,  each  of  which  has  an  excavation  perforated  with  oj^en- 
ings,  a  veritable  amygdaloid  cavity,  which  represents  the  amygdcdee  (tonsils) 
of  Man  and  the  Carnivora ;  it  is  a  kind  of  common  confluent  for  the 
numerous  glandxilai  accumulated  outside  the  mucous  membrane  which  lines 
this  excavation. 

The  anterior  extremity  of  the  tongue  is  quite  independent  from  the 
middle  of  the  interdental  space,  and  moves  freely  in  the  interior  of  the  buccal 
cavity :  it  is  also  teiTQed  the  free  portion  of  the  tougue,  in  opposition  to  the 
remainder  of  the  organ,  which  is  named  the  fixed  portion.  This  free  portion 
is  flattened  above  and  below,  and  slightly  widened  or  spatulated.  Its 
superior  face  is  plane,  or  nearly  so,  and  prolongs  that  of  the  fixed  portion. 
The  inferior,  slightly  convex,  and  perfectly  smooth,  is  continuous  with  the 
lateral  faces  of  the  organ,  and  rests  on  the  body  of  the  maxillary  bone  ;  it  is 
fixed  to  that  bone  by  a  median  fold  of  mucous  membrane,  the  anterior  pnllar, 
OT  frsenum  linguce.  The  bordei-s,  in  joining  each  other  in  front,  describe  a 
parabolic  curve  which  is  in  contact  with  the  incisive  arches. 

Structuke. — The  tongue  offers  for  study,  in  regard  to  its  structure  : 
1,  The  mucous  membrane  enveloping  the  organ;  2,  The  muscular  tissue  wh-ch, 
in  reality,  forms  its  mass ;  3,  The  vessels  and  nerves  distributed  to  it. 

1.  Mucous  membrane. — This  membrane,  a  continuation  of  that  lining  the 
mouth,  is  folded  at  the  bottom  of  the  canal  on  the  sides  of  the  tongue,  covers 
the  upper  surface  of  the  organ,  and  envelops  the  whole  of  its  free  portion. 
Its  derm  or  corium  has  not  the  same  thickness  throughout,  but  is  incom- 


336  THE  DIGESTIVE  APPABATUS  IN  MAMMALIA. 

parably  thinner  and  less  dense  on  the  sides  of  the  fixed  portion  and  the 
inferior  plane  of  the  free  part ;  on  the  dorsum  of  the  tongue  it  is  difficult  to 
cut  it.  Its  deep  face  receives  the  insertion  of  a  large  number  of  the  muscular 
fibres  of  the  organ,  and  for  the  greater  part  of  its  extent  it  adheres  in  the 
most  intimate  manner  to  these  fibres ;  though  its  adherence  is  not  so  close 
at  those  points  where  it  is  in  contact  with  the  labial  glandules. 

Its  superficial  face  is  not  smooth,  but  shows  a  prodigious  quantity  of 
minute  prolongations  or  papillce,  which,  according  to  their  shajje,  are  dis- 
tinguished as  filiform,  fungiform,  and  calyciform  papillce. 

The  filiform  papilhv.  are  formed  by  thin  prolongations  terminating  in  a 
point,  each  being  covered  by  an  epithelial  sheath  which  greatly  increases  its 
dimensions.  They  are  simple  or  composite,  having  at  their  summit 
secondary  jn-olongations,  much  smaller,  and  provided  also  with  an  epithelial 
covering.  These  filiform  papillte  are  largest  on  the  middle  part  of  the 
dorsum  of  the  tongue,  where  they  present  a  tufty  appearance ;  towards  the 
j)oint  of  the  organ  they  are  imbedded  in  epithelium,  and  are  scarcely 
apjjarent  in  the  minute  elevations  on  its  surface. 

The  fungiform  papillcB  (p.  capitatce)  are  club  or  sponge-shaped  elevations 
of  the  derm,  attached  to  the  membrane  by  a  short  pedicle.  Their  surface  is 
convex  and  smooth,  or  studded  with  filiform  papillae.  They  are  scattered 
irregularly  over  the  dorsum  of  the  tongue,  among  the  filiform  papillae,  and 
are  most  numerous  on  the  posterior  third  of  its  surface. 

The  calyciform  papillcB  (fosstilate,  circumvallate,  or  lenticular  papilloe)  are 
really  fungiform,  but  instead  of  projecting  above  the  free  surface  of  the  derm, 
they  are  placed  in  a  depression  of  this  membrane.  They  are  surrounded 
by  a  slightly-elevated  ring,  within  which  is  a  narrow  fossa  around  the 
pedicle  of  the  papilla ;  several  papillae  may  be  contained  within  one  cup- 
shaped  cavity.  They  only  exist  at  the  base  of  the  tongue,  where  two  of 
their  number,  very  developed  and  composite,  coriespond  to  the  hlincl  holes  of 
Morgagni  (foramen  caecum).  At  the  base  of  a  certain  number  of  the  fungi- 
form and  calyciform  papillae  is  a  band  of  adenoid  tissue. 

It  is  generally  believed  that  these  three  kinds  of  papillae  have  each  a 
distinct  function ;  the  filiform  are  to  retain  the  alimentary  and  sapid  sub- 
stances on  the  surface  of  the  tongue  ;  the  fungiform  are  tactile  organs,  and 
the  calyciform  are  gustatory. 

2.  Muscles. — Beneath  the  mucous  membrane,  on  the  dorsal  surface  of 
the  tongue,  is  a  cylindrical  fibrous  cord  which  sometimes  attains  the  thick- 
ness of  a  large  goose-quill.  This  cord  is  situated  in  the  median  jjlane, 
near  the  middle  part  of  the  organ,  and  is  from  2  to  3  inches  long.  It  may 
be  considered  as  a  fibrous  support  to  the  muscular  tissue,  and  it  sometimes 
directly  adheres  to  the  deep  surface  of  the  tegument.  At  other  times,  it  is 
only  connected  with  that  membrane  by  a  very  short  lamellar  prolonga- 
tion, and  is  then  buried  a  little  deeper  among  the  fibres  of  the  superior 
muscular  layer. 

(The  German  hippotomists  designate  this  the  cartilage  of  the  tongue.  It 
is  only  found  in  Solipeds,  and  was  first  described  by  Briihl,  who  gave  it  this 
designation.  Leyh  states  that  it  is  composed  of  dense  fibro-cartilage, 
surrounded  by  cellular  and  adipose  tissue ;  that  it  is  from  4  to  7  inches 
long,  and  |ths  to  1  inch  in  thickness ;  and  that  it  commences  about  an  inch 
from  the  anterior  appendix  of  the  hyoid  bone.) 

A  similar  cord,  but  not  so  strong  or  well  defined,  is  sometimes  found  at 
the  inferior  siirface  of  the  free  portion  of  the  tongue. 

Intrinsic  muscles. — In  studying   the  proper  substance  of  the  tongue  in 


TEE  MOUTH.  337 

two  sections,  one  vertical  and  longitudinal,  tlie  other  transverse,  there  is 
seen,  under  the  dorsal  mucous  membrane,  a  layer  of  red  fibres,  very  close  in 
their  textm-e,  and  very  adherent  to  that  membrane.  Amongst  these  fibres, 
there  are  some  which  affect  a  longitudinal  direction,  but  the  majority  are 
vertical  or  transverse,  and  all  are  interlaced  in  the  most  intimate  mamier. 
It  appears  as  if  this  layer  ( the  Ungnalis  sujierficiaUs  of  Man)  was  perfectly 
independent  of  the  other  muscidar  fibres,  whose  insertion  it  receives.  It 
also  forms  a  portion  of  those  which  writers  have  named  the  intrinsic  muscles 
of  the  tongue,  and  which  comprise  a  su];)enor  and  inferior,  a  transverse  and  a 
vertical  Ungualis  muscle.  An  attentive  examination,  however,  readily  shows  that 
the  fibres  proper  to  this  submucous  layer  are  continuous  with  those  which, 
coming  from  a  poixit  situated  beyond  the  tongue,  form  the  muscles  named,  in 
consequence,  extrinsic,  and  that  they  ai'e  only  the  prolongations  of  these. 
This  division  of  the  tongue  into  two  orders  of  muscular  fosciculi  does  not, 
for  tliis  reason,  possess  the  importance  generally  accorded  to  it. 

IJoctrinsic  muscles. — If  the  muscular  fibres  of  the  tongue  appear  to  be  one 
mass  in  the  superior  layer  just  referred  to,  it  is  not  so  when  they  are 
followed  beyond  this  layer ;  on  the  contrary,  V7e  see  them  separate  from  one 
another,  and  even  admit  between  them — at  least  in  the  fixed  portion — a 
certain  amount  of  adipose  tissue,  which  is  particularly  abundant  towards  the 
base,  where  it  forms  a  mass  called  the  fatty  nucleus  of  Baur ;  then  they 
collect  into  fasciculi,  or  perfectly  distinct  muscles. 

In  Solipeds,  these  muscles  number  five  pairs ;  1,  The  stylo-  or  Kerato- 
glossus ;  2,  The  great  liyo-  or  hasio-glossus ;  3,  The  genio-glossus ;  4,  Tlie 
small  hyo-glossus  (the  superior  lingual  of  some  authorities);  5,  The  jfharyngo- 
glossus 

STTLO-GLOSSUS. 

^Sytioiu/ms. — The  hyo-glossus  hngus  of  PercivaU.  Kerato-glossiis  externug—Leyh. 
The  stylo-glossus  of  Man.) 

This  is  a  very  long  riband-shaped  band,  formed  of  bright-red  parallel 
fibres,  and  extending  from  the  styloid  bone,  or  large  branch  of  the  os  hyoides, 
to  each  side  of  the  free  extremity  of  the  tongue. 

It  originates  on  the  external  surface  of  the  large  hyoideal  branch,  near 
its  inferior  extremity,  by  a  very  thin  aponeurosis  ;  and  terminates  near  the 
tip  of  the  tongue  in  expanding  over  the  inferior  surface  and  borders  of  the 
organ,  and  confounding  its  fibres  with  those  of  the  opposite  muscle. 

In  the  fixed  portion  of  the  tongue,  this  muscle  responds :  outwardly,  to 
the  mylo-hyoideus,  sublingual  gland,  lingual  nerve,  and  the  "Whartoniau 
duct ;  inwardly,  to  the  genio-glossus  and  great  hyo-glossus  muscles.  The 
whole  of  its  free  portion  is  covered  by  the  buccal  membrane. 

In  contracting,  this  muscle  pulls  the  tongtte  towards  the  back  of  the 
mouth,  and  inclines  it  to  one  side  when  acting  independently  of  its  fellow 
on  the  opposite  side  (Fig.  149,  1.) 

GEEAT    HTO-GLOSSUS    Of    BASIO-GLOSSTTS. 
{Synonyms. — Hyo-glossus  hrevis — PercivaU.     Hyo-glossus — Leyh.') 

A  wide  muscle,  flattened  on  both  sides,  thicker  than  the  preceding,  and 
composed  of  fibres  passing  obliquely  forward  and  upward,  the  longest  of  which 
are  anterior. 

Its  origin  occupies  the  whole  side  of  the  body  of  the  os  hyoides,  from  the 
extremity  of  the  comu  to  that  of  the  anterior  appendix.     Its  fibres,  after 


338 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


becoming  detached  frnm  this  point  of  insertion,  are  insinuated  beneath  the 
preceding  muscle,  spread  out  under  the  mucous  membrane  covering  the 
lateral  aspect  of  the  tongue,  and  for  the  most  part  are  reflected  inwards,  nearly 
\:o  the  superior  face,  to  constitute  the  transverse  fibres  of  the  organ. 

It  is  in  relation,  outwardly,  with  the  mylo-hyoideus,  stylo-glossus,  the 
great  hypo-glossal  nerve,  Wharton's  duct,  and  the  lingual  mucous  membrane  ; 
inwardly,  with  the  small  hyo-glossus,  the  small  branch  of  the  os  hyoides,  the 
pharyngo-glossus,  genio-glossus,  lingual  artery,  the  terminal  divisions  of  the 
glosso-pharyngeal  nerves,  and  great  and  small  hypo-glossals.     (Fig.  149,  2. ) 

It  retracts  the  tongue  in  depressing  its  base,  according  as  it  acts  singly 
or  simultaneously  with  its  fellow. 

(In  1850,  Briihl  described  as  the  middle  descending  stylo-glossus,  a  long, 
narrow  muscle  arising  from  the  lower  extremity  of  the  inner  face  of  the 
styloid  bone,  or  large  branch  of  the  os  hyoides,  and  terminating  near  the 
tip  of  the  tongue,  where  it  is  covered  by  the  hyo-glossus.  It  has  since  been 
described  as  the  internal  or  small  Kerato-glossus.  Its  action  is  the  same  as 
the  stylo-glossus.) 

CENIO-GLOSSUS. 
(Synonym. — Genio-hyo-glossuB — PercivaU.) 

This  is  a  beautiful  muscle,  whose  fibres  are  disposed  like  a  fan  in 
the  vertical  and  median  plane  of  the  tongue. 

It  originates  from  the  inner  surface  of  the  lower  jaw,  near  the  symphysis, 
by  a  tendon  parallel  to  that  of  the  genio-hyoidous.  From  this  tendon  are 
detached  a  multitude  of  divergent  fibres  which  pass  backwards,  upwards,  and 
forwards,  to  reach  the  upper  surface  of  the  tongue  and  become  continuous 
with  the  vertical  fibres  of  the  submucous  layer. 

Fio;.  149. 


MUSCLES  OF   THE   TONGUE,   SOFT   PALATE,   AND   PHARYNX. 

1,  Stylo-glossus ;  2,  Great  hyo-glossus ;  3,  The  same,  covered  by  the  submucous 
layer  formed  by  the  expansion  of  the  small  hyo-glossus;  4,  Genio-glossus;  5, 
Pharyngo-glossus;  6,  Pterygo-pharyngeus ;  7,  Hyo-pharyngeus ;  8,  Thvro-pha- 
rvngeus;  9,  Crico-pharyngeus ;  10,  (Esophagus;  11,  12,  Tensors  palati ;  13, 
Stylo-hyoideus ;  14,  Hj-oideus  magnus  ;  15,  Genio-hyoideus  ;  16,Hyo-thvroideus  ; 
17,  Sterno-thyroideus  ;  18,  Crico-thyroideus. 


THE  MOUTH. 


339 


Fisr.  150. 


OXE  LOBE  OF  A  RACE- 
MOSE GLAND. 

1,  Casing  of  connective 
tissue ;  2,  Excretory 
duct;  3,  Glandular 
vesicle,  or  acini. 

Fis.  151. 


The  two  genio-glossi  lie  together  on  the  median  plane  of  the  tongue, 
except  towards  their  origin,  where  they  are  constantly  kept  apart  by  adipose 
tissue.  Their  inferior  border  responds  to  the  genio-hyoid  muscles,  and  their 
anterior  fibres  are  partly  included  between  the  two 
mucous  layers  of  the  frtenum  lingufe.  They  are  re- 
lated, by  their  external  fiice,  to  the  basio-  or  great 
hyo-glossus,  the  stylo-glossus,  the  sublingual  gland,  the 
lingual  artery,  and  the  terminal  branches  of  the  thi-ee 
Lngual  nervcS. 

The  action  of  the  genio-glossus  is  complex ;  accord- 
ing to  the  portion  of  its  fibres  which  contract,  it  will 
carry  the  tongue  forwards,  pull  it  into  the  buccal 
cavity,  or  draw  it  downwards  into  the  floor  of  the  mouth. 
(Fig.^  149,  4.) 

SMALL    HYO-GLOSSUS. 

jnomjm. — Lingualis  superior  of  3Ian.  (Lingualis  of  Perci- 
vall.) 

Under  this  name  is  described  a  thin  band,  formed  of 
parallel  fibres,  which  is  exposed  immediately  on  remov- 
ing the  mucous  membrane,  with  the  subjacent  glands, 
from  the  base  of  the  tongue.  This  band  arises  from  the 
inner  side  of  the  articulation  uniting  the  body  of  the  os 
hyoides  to  its  small  branch.  It  passes  above  the  trans- 
verse muscle  of  that  bone,  which  it  crosses  perpendi- 
cularly, is  surrounded  at  this  point  by  a  great  mass  of 
adipose  tissue,  and  is  prolonged  directly  forward,  be- 
neath the  lingual  mucous  membrane.  Its  fibres  then 
vanish,  either  on  the  superior  aspect  of  the  tongue  or 
on  its  sides,  or  they  descend  obliquely  in  crossing  the 
direction  of  the  hyo-glossus,  to  join  the  superior  border 
of  the  stylo-glossus  (Fig.  149,  3). 

(This  muscle  contracts   and   retracts   the    tongi:e.) 

PHAEYXGO-GLOSSUS. 

{Stjnoivjm.— The  palato-glossus  of  Man.) 

A  rudimentary  muscle  fonned  of  parallel  fibres, 
which,  from  their  origin  on  the  lateral  wall  of  the 
pharynx,  pass  outside  the  articular  angle  of  the  branches 
of  the  OS  hyoides,  and  between  the  hyo-glossus  and  genio- 
glossus,  mixing  with,  and  intercrossing  their  fibres. 

3.  Labial  glands. — The  nimaerous  glands  of  the 
tongue  may  be  divided  into  racemose  (or  lobulated) 
glands,  and  closed  follicles  (or  follicular  glands.) 

The  racemose  glands  are  spread  on  the  sides  and  base 
of  the  tongue.  Kear  its  upper  border  they  form  two 
rows,  which  are  rendered  \isible  by  the  presence  of  a 
small  tubercle  placed  beside  each  of  them.  At  the  base 
of  the  tongue  they  are  found  beneath  the  fungiform  and 
calyciform  papillfe.  as  well  as  beneath  the  layer  of 
inclosed  follicles  which  lines  the  isthmus  of  the  fauces. 

At  the  entrance  to  this  passage,  the  l-ngual  mucous 
membrane  is  mammillated,  and  each  elevat'on  has  an 


FOLLICULAR   GLAND 

FROM   THE   ROOT  OF 

THE   TOXGUE. 

L,  Epithelium;  2,  Pa- 
pilla: of  mucous  mem- 
brane ;  3,  Cavity  of 
the  lollicle ;  4,  In- 
vesting coat  of  the 
gland  composed  of 
connective  tissue ;  5, 
Fibro  -  vascular  mr- 
tris,  formmg  its  par- 
enchyma, and  con- 
taining, 6,  6,  the 
closed  capsules  or 
follicles. 


340  THE  DIGESTIVE  APPARATUS  IN  MAM3IALIA. 

orifice.  This  arrangement  is  connected  with  the  presence,  at  this  part  of 
the  tongue,  of  the  closed  follicles,  which  are  more  or  less  voluminous  and 
aggregated,  and  separated  from  the  muscles  by  a  continuous  layer  of  race- 
mose glands.  They  are  composed  of  a  casing  of  condensed  connective,  and  a 
mass  of  adenoid  tissue,  which  has  in  its  centre  a  cavity  that  communicates 
with  the  orifice  above  the  follicle,  and  is  lined  by  the  lingual  epithelium 
minus  its  horny  layer. 

4.  Vessels  and  nerves. — The  tongue  is  supplied  with  blood  by  two 
arteries,  the  lingual  and  sublingual;  the  blood  is  removed  by  three  large 
veins,  two  of  which  enter  the  external  maxillary,  and  the  third  the  internal 
maxillary  vein.  The  lymphatics  constitute  a  very  fine  superficial  network, 
whose  emergent  branches  pass  to  the  submaxillary  glands.  The  nerves 
are  the  lingual,  the  glosso-pharyngeal,  and  the  great  hypo-glossal ;  the  latter 
is  a  motor  nerve,  and  consequently  supplies  the  muscles ;  the  others  are 
exclusively  sensitive,  and  are  distributed  more  particularly  to  the  mucous 
membrane. 

Functions. — The  tongue  serves  for  the  prehension  of  liquids  in  all 
animals,  and  for  solid  aliment  in  the  Ox.  It  concurs,  with  the  jaws,  in  pro- 
pelling the  substances  to  be  crushed  between  the  molar  teeth  during  masti- 
cation ;  and  it  is,  besides,  one  of  the  essential  organs  of  deglutition.  It  is 
able  to  play  this  important  and  complex  part  through  the  varied  movements 
it  can  execute  in  the  interior  of  the  mouth ;  and  the  extent  of  these  move- 
ments demands  a  moment's  notice.  They  are  of  two  kinds :  those  which 
influence  only  the  form  of  the  organ,  and  those  which  cause  it  to  submit  to 
various  displacements.  They  result  in  either  compressing  it  from  side  to 
side,  above  to  below,  or  curving  it  longitudinally,  and  even  transversely. 
These  movements  are  principally,  but  not  exclusively,  due  to  the  action  of 
the  intrinsic  fibres  ;  they  are  perfectly  independent  of  the  movements  which, 
as  a  whole,  produce  the  total  displacement  of  the  tongue.  With  regard  to 
these  latter,  they  may  result  in  carrying  the  tongue  beyond  the  mouth,  or 
withdrawing  it  into  that  cavity,  inclining  it  to  one  side,  raising  it  against 
the  palate,  depressing  it  on  the  floor  of  the  intermaxillary  space  or,  finally, 
lifting  it  towards  the  pharynx.  It  is  worthy  of  remark  that  these  move- 
ments do  not  alone  result  from  the  action  of  the  proper  lingual  muscles 
above  described ;  those  belonging  to  the  os  hyoides,  to  which  is  attached 
the  lingual  api)endix,  concur  also  in  producing  them.  But  this  appendix  is 
not  the  only  organ  thus  attached  to  the  hyoideal  apparatus  ;  the  larynx  and, 
through  its  intermediation,  the  pharynx,  are  placed  in  the  same  conditions, 
and  are  obliged  to  follow,  like  the  tongue,  the  movements  of  the  bony  frame- 
work supporting  them. 

There  consequently  results  between  these  three  organs  a  remarkable 
unity  of  action,  which  is  readily  explained  by  the  part  they  all  take  in  the 
one  common  act  of  deglutition. 

5.  Soft  Palate.     (Figs.  148,  152.) 

Preparation. — The  soft  palate  is  studied:  1,  On  the  antero-postcrior  and  vertical 
Bection  of  the  head  (fig.  152);  2,  On  the  portion  intended  to  show  the  interior  of  the 
pharvnx  (see  the  preparation  of  this  region);  'S,  On  the  portion  represented  in  fig.  1-18, 
ihe  mode  of  dissecting  which  has  been  indicated  at  page  333;  in  removing  the  mucous 
membrane  and  glamhdar  layer,  the  fibrous  membrane  and  the  two  intrinsic  muscles  are 
exposed.     The  extrinsic  muscles  should  be  studied  with  those  of  the  pharynx. 

Situation — Form. — The  soft  palate  (palatum  molle,  velum  pendulum  palatt) 
is  suspended  like  a  partition  between  the  mouth  and  the  pharynx,  and  by  its 


THE  MOUTH. 


sn 


posterior  border  circumscribes  the  orifice  wliicli  establishes  a  communica- 
tion between  these  two  cavities. 

Tiiis  partition,  which  continues  the  pahxte  posteriorly,  represents  in  its 
external  form  a  membranous  valve,  oblique  from  above  to  below  and  befdro 
to  beliind,  much  longer  than  it  is  wide,  and  exhibiting  for  study  tuo  faces 
and/oH>-  borders. 

The  inferior  or  anterior  face,  tnrned  towards  the  mouth,  shows  lon<n- 
tudinal  folds  and  transverse  ridges,  with  multitudes  of  oritices  belonfins  to 
the  submucous  glauduise.  On  its  sides  it  is  united  to  the  base  of  the  tongue 
by  means  of  two  thick  mucous  columns,  designated  the  posterior  pillars 
of  the  tongue.  The  superior  or  posterior  face  constitut  s  the  anterior  wall 
of  the  pharynx  ;  it  only  exhibits  some  very  slight  lougitudinal  ridges. 

Fig.  152. 


MEDIAX    LOXGirTDIXAL   SECTIOX    OF    THE    HEAD   AXD    irPPER    PART   OF   XECK. 

1,  Upper  lip  :  2,  Premasilla;  3.  Hard  palate;  4,  Tongue;  5.  Septum  nasi ;  6,  Nasal 
bone;  7,  Palatine  arch:  9.  Pterygoid  bone;  10.  Epiglottis;  11,  Entrance  to  the 
Eustachian  tube;  12,  Arrtenoid  cartilage.  13,  Cricoid  cartilage;  14,  (Esophagus; 
15,  Frontal  bone  and  sinus  :  16.  Cerebrum  :  17,  Corptis  callosum  :  18,  Cerebellum  ; 
19,  Sphenoid  bone :  20,  Medulla  oblongata ;  21.  Cervical  ligament  ;  22,  Spinal 
cord;  23,  Occipital  bone;  24,  24,  Atlas;  25,  25,  Dentata  ;  26,  Trachea. 


The  two  Jnteral  horders  are  inserted  into  the  walls  of  the  two  cavities 
which  the  soft  palate  separates.  The  anterior  border,  continuous  vriih  the 
palate,  is  attached  to  the  palatine  arch,  and  follows  the  curve  described  by 
it.  The  posterior  border,  the  only  free  one,  has  a  concave  form,  and 
closely  embraces  the  base  of  the  epiglottis,  which  is  most  usually  found 
reversed  on  the  pcsterior  surface  of  this  curtain.  This  border  is  continued 
at  its  extremites  by  two  thin  prolongations,  which  can  be  followed  on  the 
lateral  walls  of  the  pharynx  to  the  oesophageal  infundibulmn.  above  which 
they  unite  in  the  form  of  an  arch.  These  prolongments  are  named  the 
posterior  pillars  of  the  soft  pa'ate,  in  contradistinctmn  to  the  two  mucous 
folds  at  the  base  of  the  tongue,  which  constitute,  by  their  relation  to  this 
partition,  veritable  anterior  pillars.  This  posterior  border  concvu-s  to  cir- 
25 


342  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

cumscribe  what  is  named  the  isthmus  of  the  fauces,  an  aperture  constantly 
closed,  in  consequence  of  the  great  development  of  the  soft  palate  ;  it  is  only- 
dilated  for  the  passage  of  the  alimentary  substances  passing  into  the  pharynx. 
The  isthmus  of  the  fauces  is,  therefore,  not  merely  an  opening ;  it  is  a 
passage  which  has  for  its  inferior  wall  the  base  of  the  tongue  as  far  as  the 
epiglottis  ;  for  its  Tipj)er  wail  the  anterior  face  of  the  soft  palate ;  and  for 
its  sides  the  posterior  pillars  of  the  latter. 

Structure. — To  give  the  most  simj^le  idea  of  the  structure  of  the  soft 
palate,  it  might  be  said  that  the  mucous  membrane  of  the  palato  and  that  of 
the  floor  of  the  nasal  cavities  are  prolonged  behind  the  palatine  arch, 
parallel  to  one  another,  and  become  joined  towards  the  free  border  of  this 
curtain ;  and  it  might  be  further  shown  that,  in  the  space  between  these  two 
mucous  membranes,  there  is  a  librons  membrane,  muscles,  a  glandular  layer, 
vessels,  and  nerves  ;  besides  these,  there  are  no  other  elements  in  the  organi- 
sation of  the  soft  palate.  They  may  be  studied  in  the  following  order :  1, 
Fibrous  membrane;  2,  Muscles;  3,  Mucous  membranes;  4,  Vessels  and  nerves. 

1.  Fibrous  membrane  (I^'ig.  148,  5). — This  membrane,  remarkable  for  its 
power  of  resistance,  forms  a  real  framework  for  the  soft  palate,  of  which  it  only 
occupies  the  anterior  moiety.  It  is  attaclied  in  frcmt  of  the  palatine  arch, 
and  is  jtrolongcd  posterioily  by  a  particular  musclo,  the  palato-pharyngeus. 

2.  Muscls. — Of  these  muscles,  which  are  all  pairs,  there  are  those  which 
constitute  a  layer  situated  in  the  middle  of  the  soft  palate  itself,  and 
representing  the  intrinsic  muscles ;  these  are  the  pharynfjo-stnphyleus  (joalato- 
pliaryngeus)  and  the  palato-staphyleus  (circumjlexus  j^a^titi).  The  others,  the 
peristaphyleus, — extsrnal  and  internal  {tensors paJati,  external  and  internal), 
are  only  inserted  into  the  organ  by  their  terminal  extremities  and  therefore 
act  as  extrinsic  muscles. 

PHARYNGO-STAPHYLEUS.       (Fig.  148,  6). 
(^Synonym. — Palato-pharyngeus. — Ptrcivall.) 

In  removing  the  mucous  and  glandular  layers  which  cover  the  anterior 
face  of  the  soft  palate,  there  is  exposed  a  wide  and  thin  muscular  fasciculus 
succeeding  the  fibrous  layer  behind,  and  occupying  the  posterior  half  of  the 
entire  organ.  The  fibres  of  which  this  muscle  is  composed,  confounded  on 
the  median  line  with  those  of  the  muscle  on  the  opposite  side,  are  directed 
backwards  and  outwards,  the  most  posterior  following  the  curve  of  tlie  free 
border  of  the  curtain.  Arriving  near  the  lateral  border,  they  are  re- 
flected upwards,  jjassiug  between  the  pharyngeal  mucous  membrane  and 
the  middle  constrictor  of  the  pharynx,  with  which  it  appears  to  be  con- 
founded posteriorly ;  but  with  a  little  attention  it  can  be  followed  to  the 
superior  border  of  the  thyroid  cartilage,  into  which  it  is  inserted  after 
making  a  somewhat  long  track  under  the  mucous  membrane  of  the  pharynx. 

This  muscle  stretches  the  curtain,  and  draws  its  free  border  from  the 
oesophageal  infimdibulum  during  pharyngeal  deglutition. 

PALATO-STAPHYLEUS. 

ySj/nonyms. — Staphyleus — Girurd.  Circuivfiexus  pnlati — Percivall.  The  azygoauvulm 
of  Man.) 

A  small,  elongated,  cylindrical,  bright-red  muscle,  in  opposition,  on  the 
median  line,  to  that  of  the  other  side,  and  extending  over  the  inferior  surface 
of  the  preceding,  from  the  palatine  arch  to  the  free  border  of  the  soft  palate, 
which  it  pulls  forward  and  upward  to  dilate  the  isthmus  of  the  fauces.     It 


THE  MOUTH.  343 

originates  by  a  small  glistening  tendon,  not  from  the  palatine,  but  from  the 
uvular  aponeurosis  (Fig.  148,  7).  The  fascia  which  the  two  muscles  form 
is  fur  the  most  part  covered,  in  its  middle  portion,  by  the  fibres  of  tii3 
tcnsores  palati. 

rEEISTAPHYLEUS    EXTEKNUS. 
(Synonyms. — Tensor  paJati — Pereivall.     The  eircumfiexus  of  Man.) 

This  is  a  small,  elongated  muscle,  depressed  on  both  sides,  bulging  in  its 
middle,  thin  and  tendinous  at  its  extremities,  and  extending  obliquely  for- 
ward and  downward  from  the  styloid  process  of  the  temporal  bone,  where 
it  has  its  origin,  to  the  pterygoid  trochlea.  Its  terminal  tendon  glides 
and  is  inflected  inwards  on  this  pulley,  to  be  afterwards  spread  out  and 
confounded  with  the  fibrous  framework  of  the  soft  j)alate,  which  causes  this 
fi'amework  to  represent  an  expansion  of  the  tendon. 

The  muscle  is  covered  outwardly  by  the  pterygoidei  muscles ;  it 
responds,  internally,  to  the  next  muscle,  which  separates  it  from  the 
Eustachian  tube. 

It  is  a  tensor  and  depressor  of  the  aponeurosis  of  the  soft  palate 
(Fig.  149,  11). 

PERISTAPHYLEUS     IXTERNUS. 
{Synonyms. — Stylo-^haryngeus — Pereivall.     Tl;e  levator  palati  of  Man._, 

This  is  formed  by  a  pale  and  thin  band,  which  originates  with  the 
preceding  muscle,  descends  between  it  and  the  Eustachian  tube,  passes 
beneath  the  superior  constrictor  of  the  pharynx,  then  below  the  mucous 
membrane  of  the  pharynx  to  reach  the  soft  palate,  where  it  exj^auds  on  the 
anterior  or  posterior  surface  of  the  palato-pharyngeus,  beneath  the  glandular 
layer,  its  fibres  becoming  mixed,  on  the  median  line,  with  those  of  its  fellow. 

This  is  an  elevator  of  the  soft  palate  (Fig.  149,  12). 

3.  Glandular  layer.  ■ —  This  layer  is  comprised  between  the  fibrous 
membrane  and  the  anterior  mucous  layer,  becoming  thinner  as  it  is  pro- 
longed over  the  intrinsic  muscles ;  it  does  not  extend  to  the  free  border  of  the 
organ.  It  is  thickest  on  each  side  of  the  median  plane,  where  it  forms  two 
lobes  which  appear  on  the  anterior  aspect  of  the  soft  palate  as  an  elongated 
ridge,  much  more  marked  in  the  Ass  than  the  Horse.  It  is  worthy  of  notice, 
that  the  glandular  granulations  composing  this  layer  throw  all  their  secre- 
tion into  the  mouth — that  is,  on  the  anterior  face  of  the  septum. 

4.  Mucous  membranes. — -The  soft  palate  is  covered  on  both  its  surfaces 
by  two  mucous  layers,  one  anterior,  the  other  posterior,  united,  as  has  been 
remarked,  at  the  free  border  of  the  organ.  The  anterior  is  continuous, 
above,  with  the  mucous  membrane  of  the  hard  palate ;  on  its  sides,  with 
that  which  covers  the  base  of  the  tongue.  In  structure  it  is  the  same  as 
the  buccal  membrane;  its  epithelium  is  stratified  i)avement.  The  other 
layer  is  nothing  more  than  the  pituitary  membrane  extended  over  the 
posterior  surface  of  the  septum,  and  thence  to  the  lateral  surfaces  of  the 
pharynx.     It  will  be  more  fully  described  with  the  latter. 

5.  Vessels  and  nerves. — The  soft  palate  is  supplied  with  blood  by  the 
accending  pharyngeal  and  internal  ma.uUary  arteries.  The  nervous  filaments 
this  partition  receives  emanate  from  the  fifth  pair  of  cranial  nerves  (superior 
maxillary  branch),  and  from  Meckel's  ganglion;  they  form  the  posterior 
palatine  nerve  (Fig.  148,  8). 

Functions. — During  the  act  of  deglutition,  the  soft  palate  is  raised  to 


344  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

enlarge  the  isthmus  and  allow  solids  or  liquids  to  pass  through.  The  descrip- 
tion given  of  this  septum  permits  us  to  understand  how  it  plays  the  joartof  a 
valve  in  rising  freely  while  the  alimentary  bolus  or  mouthful  of  fluid  passes 
from  the  mouth  into  the  oesophagus,  across  the  pharyngeal  vestibule,  but 
never  allows  the  matters  which  have  once  entered  the  oesophageal  canal  to 
return  into  the  buccal  cavity.  Also  why,  when  any  obstacle  is  opposed  to  the 
descent  of  aliment  into  the  oesophagus,  after  it  has  cleared  the  isthmus  of 
the  fauces,  or  even  when  the  animal  vomits,  the  matters  arrested  in  their 
jiassage  or  ex^ielled  from  the  stomach  are  ejected  by  the  nasal  cavities, 
after  flowing  over  the  posterior  surface  of  the  soft  palate.  This  disposition 
of  the  pendulous  curtain,  in  forming  a  complete  jjartition  which  hermeti- 
cally seals  the  orifice  of  communication  between  the  mouth  and  pharynx, 
likewise  sufficiently  explains  why,  in  normal  circumstances,  Solipeds  respire 
exclusively  by  the  nostrils. 

6.   Tlie  Teeth. 

Passive  agents  in  mastication,  the  teeth  are  hard  organs,  bony  in 
appearance,  imjjlanted  in  the  jaws,  and  projecting  into  the  interior  of  the 
mouth  to  bruise  or  lacerate  the  solid  alimentary  substances. 

Identical  in  all  our  domesticated  animals,  by  their  general  disposition, 
their  mode  of  development,  and  their  structure,  in  their  external  con- 
formation these  organs  present  notable  differences,  the  study  of  which  ofiers 
the  greatest  interest  to  the  naturalist.  For  it  is  on  the  form  of  its  teeth 
that  an  animal  depends  for  its  mode  of  alimentation ;  it  is  the  regime,  in 
its  turn,  which  dominates  the  instincts,  and  commands  the  diverse  modifica- 
tions in  the  apparatus  of  the  economy ;  and  there  results  from  this  law  of 
harmony  so  striking  a  correlation  between  the  arrangement  of  the  teeth 
and  the  conformation  of  the  other  organs,  that  an  anatomist  may  truly  say, 
"  Give  me  the  tooth  of  an  animal,  and  1  will  tell  you  its  habits  and 
structure." 

Compelled  by  the  limits  of  our  task  to  confine  ourselves  to  the  purely 
descrijitive  part  of  the  dental  apparatus,  we  cannot  stop  to  notice  the 
interesting  physiological  considerations  on  which  this  principle  is  founded; 
but  will  begin  at  once  the  anatomical  study  of  the  teeth  by  indicating  their 
general  characters,  before  examining  them  successively  in  all  the  domestic- 
ated species. 

A.  General  Characters  of  the  Teeth  — General  Disposition. — The 
teeth  are  fixed  in  the  jaws,  and  ranged  one  against  the  other  in  such  a  way 
as  to  form  two  parabolic  arches  opening  behind,  and  interrupted  on  each 
side  by  what  is  called  the  interdental  space.  Distinguished  into  suiierior 
and  inferior,  like  the  jaws  to  which  they  belong,  these  arches  come  in  contact 
with  one  another  in  a  more  or  less  exact  manner  when  the  mouth  is  perfectly 
closed. 

Those  teeth  which  are  placed  altogether  in  front,  at  the  middle  of  the  dental 
arches,  are  named  incisors  or  incisive  teeth  ;  the  others,  situated  behind  these, 
and  always  numbering  two  for  each  jaw,  are  called  the  canine  teeth  or  tuslis  ; 
while  the  designation  of  molars  is  given  to  those  which  occupy,  in  the  more 
retired  portion  of  the  buccal  cavity,  the  lateral  parts  and  extremities  of  the 
dental  arches. 

External  Conformation.— Each  tooth  represents,  when  completely 
developed,  an  elongated  polyhedron,  which  has  sometimes  a  pyramidal 
form,  and  at  others  that  of  a  cone  or  a  parallelepiped. 


THE  MOUTH. 


345 


A  portion  of  the  tooth  is  buried  and  solidly  implanted  in  one  of  the 
alveolar  cavities  of  the  maxillary  bones  ;  this  is  the  root  or  imbedded  poii ion, 
(or  fang^.  The  other  portion,  circumscribed  at  its  base  by  the  gum,  leaves 
the  alveolus  to  project  into  the  interior  of  the  mouth,  forming  the  crown 
or  free  portion.  The  narrow  constriction  between  the  crown  and  root  is  named 
the  neck. 

The  fang  is  perforated  at  its  inferior  extremity  by  one  or  more  excavations 
(cacitas  pidpce)  which  penetrate  deeply  into  the  substance  of  the  tooth,  and 
admit  into  their  interior  the  vasculo-nervous  papilla,  simple  or  ramified, 
known  by  the  name  of  the  bulb  or  dented  pidp. 

The  crown,  the  portion  submitted  to  friction  during  mastication  and, 
consequently,  to  wear,  offers  the  most  varied  forms :  sometimes  it  is  shaped 
like  a  very  acute  cone ;  at  others,  it  is  divided  into  several  tubercles  more 
or  less  salient ;  and  sometimes,  again,  it  carries  at  the  extremity  of  the  tooth 
a  wearing  surface  more  or  less  plane  and  regular. 

Structure. — Three  essentially  different  substances  enter  into  the  structure 
of  all  the  teeth :  the  ivory,  enamel,  and  cement ;  to  which  ought  to  be  added 
the  soft  parts,  the  jndp,  gum.  and  aheolo-dental  periosteum. 

Ivory. — The  'ivory,  or  dentine,  has  the  hardness  of  bone,  is  of  a  whitish- 
yellow  colour,  and  is  rendered  brilliant  in  places  by  its  nacrous  reflection.  It 
forms  the  principal  mass  of  the  tooth,  enveloping  everywhere  the  pulp  cavity. 

Examined  by  aid  of  the  microscope,  this  substance  is  found  to  be 
channeled  by  a  multitude  of  minute,  undulating,  and.  branchinc  canals 
(dental  tuhuli)  imbedded  in  amorphous  matter — the  fundamental  auhstance. 

Fior.  153. 


SECTION   THROUGH    THE    FANG   OF    A    MOLAR    TOOTH. 

a,  a,  Dentine  traversed  by  its  tubuli ;  b,  b,  Interglobular,  or  nodular  layer; 
c,  c,  Cementuna. 


The  tuhuli,  or  canaliculi,  extend  from  the  dental  cavity  to  the  inner  face 
of  the  enamel :  single  at  their  origin,  they  soon  bifurcate,  and  again  anasto- 
mose several  times  during  their  slightly-undulating  course.  They  terminate 
in  a  cul-de-sac.  or  in  irregular  cavities  situated  beneath  the  enamel,  and 
named  the  interglobular  spaces  of  Czermak  (forming  the  interglobular  or 
nodular  layer).  These  canals  have  a  thin  proper  wall,  and  contain  a  dental 
fibre,  which  very  probably  is  a  continuation  of  the  pulp-cells.  The 
fundamental  substance  (or  matrix)  is  amorphous,  and  not  very  abundant ;  in 


S46  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

its  mass  are  deposited  the  saline  molecules  which  give  the  dentine  its  bony 
consistency.  (These  molecules  are  deposited  iii  lamellae,  concentric  with 
the  pulp  cavity.  Nasniyth  considers  the  fibres  to  be  rows  of  minute  opaque 
points  arranged  in  a  linear  series  (baccated  fibres),  and  to  be  merely  the 
nuclei  of  the  ivory  cells,  the  interfibrous  substance  being  the  remainder  of 
the  cell  filled  with  calcareous  matter.) 

Its  chemical  composition  much  resembles  that  of  bones.  After  remaining 
in  dilute  hydrochloric  acid  for  several  weeks,  it  comports  itself  like  them,  by 
giving  up  the  calcareous  salts  with  which  it  is  impregnated  to  the  acid 
solution,  and  becoming  soft  like  cartilage ;  submitted  to  the  action  of  boiling 
water  it  yields  gelatine. 

Enamel. — The  enamel  extends  in  a  layer  over  the  bony  substance  of  the 
free  portion  of  the  tooth,  whose  exterior  it  entirely  envelojjs;  it  is  prolonged 
over  the  fang  in  some  animals,  and  in  several  kinds  of  teeth  it  dips  by  the 
crown  into  the  interior  of  the  organ  to  a  very  great  depth.  It  is  brilliantly 
white,  and  so  hard  that  it  strikes  fire  like  steel. 

Its  microscopic  structure  is  very  interesting,  the  enamel  being  composed 
of  small  prismatic  hexagonal  rods,  1 -5000th  of  an  inch  in  diameter,  and 
notched  on  their  faces.  ()wing  to  this  notching,  the  prisms  are  intimately 
united  to  each  other.     They  form  several  layers  which  cross  each  other  at 

Fig.  154. 


A.   TRANSVERSE   SECTION   OF   ENAMEL,    SHOWING   ITS   HEXAGONAL   PRISMS; 
B.   SEPARATED   PRISJIS. 

an  acute  angle,  though  in  each  layer  tliey  are  exactly  parallel  to  one  another. 
By  immersing  the  enamel  in  dilute  hydrochloric  acid,  there  is  detached  from 
its  surface  a  fine  amorj^hous  membrane  or  cuticle  of  the  enamel. 

(The  chemical  composition  of  enamel  appears  to  be  96  5  per  cent,  of 
earthy  matter,  and  3'5  of  animal  substance.  The  first  consists  of 
phosphate  of  lime,  with  traces  of  fluoride  of  calcium,  carbonate  of  lime, 
phosphate  of  magnesia,  and  other  salts.  The  rods  are  directed  vertically 
on  the  summit  of  tlie  crown  of  the  tooth,  and  horizontally  at  the  sides.) 

Cement. — (Cementum,  substantia  ostoidea.  cortical  substance,  or  crusta 
petrosa). — The  cement  is  spread  in  a  non-continuous  layer  over  the  external 
surface  of  the  enamel  and  dentine.  It  is  accumulated  in  large  quantity 
in  the  substance  of  some  teeth,  as  will  be  noticed  when  speaking  of  the 
incisors  in  the  Horse  and  the  molars  of  the  Herbivora. 

The  structure  and  properties  of  this  substance  differ  in  nothing  from 
the  structure  and  properties  of  the  spongy  tissue  of  bone.  In  a  physio- 
logical state,  the    cement    does   not   contain   any   Haversian   canals..      (It 


TEE  MOUTH. 


347 


155. 


contains,  sparingly,  the  lacunae  and  canaliculi  which  characterise  true 
bone  :  those  placed  near  the  surface  have  the  canaliculi  radiating  from  the 
side  of  the  lacunae  towards  the  periodontal  membrane  :  and  those  more 
deeply  placed  join  with  the  adjacent  dental  tubuli.  In  the  thicker  portions 
of  the  cnista  petrosa,  the  lamellse  and  Haversian  canals  peculiar  to  bone 
are  also  found.  As  age  advances,  the  cementum  increases  in  thickness, 
and  gives  rise  to  those  bony  growths,  or  exostoses,  so  common  in  the  teeth 
of  the  aged ;  the  pulp  cavity  also  becomes  partially  filled  up  by  a  hard 
substance,  iutermediate  between  dentine  and  bone  (osteo-dentiiie — Owen; 
secondary  dentine — Tomes).  It  appears  to  be  formed  by  a  slow  conversion 
of  the  dental  pulp,  which  shrinks  or  even  disappears — Gray.) 

Dental  }juLp. — The  pntp,  or  papilla,  is  lurmed  by  a 
fibrillar  and  nuclear  mass  that  tills  the  internal  dental 
cavity.  It  receives  blood-vessels  and  nerves,  and  is 
enveloped  in  a  very  thin  membrane  which  is  entirely 
composed  of  several  layers  of  beautiful  cylindrical  or 
prismatic  cells,  the  most  superficial  of  which  send 
fibrillar  prolongations  into  the  dental  tubuli.  Towards 
the  base  of  the  papilla,  this  membrane  assumes  thi; 
texture  of  connective  tissue,  and  is  reflected  upwards  on 
the  fang  of  the  tooth  to  line  the  alveolus,  and  join  tie 
gum  at  the  origin  of  the  crown. 

Gum. — The  gum  is  a  portion  of  the  buccal  mucous 
membrane  surrounding  the  neck  of  the  tooth,  and  con- 
curs in  consolidating  it  in  the  alveolar  cavity.  Its 
structure  is  that  of  the  membrane  t6  which  it  belongs, 
being  a  thick  dermis  furnished  with  papillse  and  tesselatcd 
epithelium.     It  does  not  contain  any  glands. 

Alveolo-dental  periosteum. — This  scarcely  differs  from 
the  ordinary  periosteum  except  in  being  a  little  softer. 
It  lines  the  alveolus  and  covers  the  cementum  ( f  the  fang. 

Development. — Each  tooth  is  developed  in  the 
interior  of  a  closed  sac  named  the  dental  follicle,  and 
lodged  in  an  excavation  in  the  maxillary  lones.  The 
sac  presents,  according  to  the  species  of  animal  and  kind 
of  teeth,  numerous  variations,  which  we  cannot  stay  to 
consider  here ;  but  must  confine  ourselves  merely  to  a 
brief  sketch  of  the  general  and  constant  characteristics 
of  its  organisation. 

Tlie  dental  follicle  is  constituted  by  an  external  en- 
veloping membrane  of  a  cellulo-vascular  natiu-e  (Fig. 
156,  a).  It  shows  at  bottom  the  simple  or  compound 
papilla  which  at  a  later  period  is  termed  the  dental 
pulp  (b)  ;  this  organ,  destined  for  the  secretion  of  the 
dentine,  then  fills  nearly  the  whole  of  the  follicle. 
In  its  upper  part  is  observed  the  enamel  organ,  or  germ 
(enamel  membrane),  formed  by  a  prolongation  of  the 
gingival  epithelium,  and  connected  with  the  latter  by  a 
small  mass  of  cells  named  the  gubeniaculum  dentis. 
Most  frequently  there  is,  opposite  the  bottom  of  the 
follicle,  one  or  more  papillae  which,  in  some  cases,  adhere  by  their 
whole  length  to  one  of  the  lateral  walls  of  the  follicular  sac,  and  the  free 
extremities  of  which  cross  those  of  the  dentine  papillae,  or  are  bui'ied  in 


t5^ 


MAGNIFIED  SECTION  OF 
A  CAXISE  TOOTH, 
SHOWING  ITS  INTI- 
MATE  STRUCTURE. 

1,  Crown  ;  2,  2,  Neck  ; 
3,  Fang,  or  root ;  4, 
C'avitac  pulpae ;  5, 
Opening  by  which 
the  vessels  and 
nerves  comrrtunicate 
with  the  pulp  ;  6,  6, 
Ivor  J,  showing 
fibrous  structure ; 
7,  7,  Enamel ;  8,  8, 
Cement. 


34S 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


Fig.  156. 


a  kind  of  cup  hollowed  on  the  summit  of  the  latter  appendages  (c).     TJiese 
ai-e  covered  by  the  membrane  of  cylindrical  cells  mentioned  above  (n). 

With  regard  to  the  enamel  organ,  its  internal  face  also  presents  a  layer 
of  cylindrical  cells. 

It  is  in  the  interval  between  these  two  papillary  systems,  that  the  dental 
substance  is  deposited  as  in  a  mould,  consequent  on  a  process  of  secretion 
and  transformation,  the  mechanism  and  progress  of  which  are  somewhat 
complicated.  The  dentine  is  produced  by  the  metamorphosis  of  the  super- 
ficial cells  of  the  dental  germ.  These  cells  send  out  ramifying  prolongations 
which  constitute  the  tubuli  of  the  dentine,  and  those  of  the  middle  layer 
secrete  an  intertubular  amorphous  substance  in  which  the  earthy  salts  are 
deposited  from  without  inwards.  The  enamel  is  deposited  on  the  dentine, 
and  results  from  the  transformation  of  the  cylindrical 
cells  of  the  germ  into  enamel  prisms.  The  cement  is, 
in  its  turn,  deposited  either  on  the  enamel  or  the 
dentine  after  their  formation,  and  is  produced,  like 
the  bony  tissue,  by  the  internal  face  of  this  (perio- 
dontal) sac,  which  has  become  alveolar  lieriosteum. 
Tliis  development  will  be  alluded  to  in  the  cha2)ter  on 
the  foetus. 

When  formed  by  the  process  above  indicated,  the 
t;)oth  pierces  its  follicle  and  appears  in  the  interior  of 
the  mouth,  after  having  traversed  the  table  of  the 
maxillary  bones,  if  there  is  any,  and  the  gingival 
membrane.  (When  the  calcification  of  the  difterent 
tissues  of  the  to'oth  is  sufficiently  advanced  to  enable 
THEORETICAL  SECTION  OF  it  to  bcar  tlio  prossuro  to  which  it  will  be  afterwards 
THE  DENTAL  SAC  OF  A  subjoctc  d,  its  cruption  takes  place,  the  tooth  making 
its  way  through  the  gum.  The  gum  is  absorbed  by 
the  pressure  of  the  crown  of  the  tooth  against  it, 
which  is  itself  pressed  up  by  the  increasing  size  of 
Papilla  of  the  'e.\t"ernal  the  fang.  Concurrent  with  this,  the  septa  between 
cavity  (pi'O  of  the  tooth,  the  dental  sacs,  at  first  fibrous  in  structure,  soon  ossify, 
md  melTrinf-^i^E"li-  *^"'^  constitute  the  alveoli;  these  firmly  embrace  the 
thelial  layer  of  the'  den-  Ji^cks  of  the  teeth,  and  afford  them  a  solid  basis  of 
tine  membrane ;  E,  Cy-  support  —  Gray.)  Though  it  has  so  far  become  esta- 
limliical  cells  of  the  blished  in  its  functions,  the  process  of  growth  in  the 
ShIe-"'T''Tname?  ^^^^^^  ^^^^  "°*  ^^^  ceased.  The  pulp  lodged  in  the 
The  secretion  of  the  ce-  internal  dental  cavity,  and  charged  with  the  formation 
ment  is  not  supposed  to  of  the  ivory  or  dentine,  continues  its  functions  :  inces- 
have  commenced.  santly  depositing   new  layers  on  those   which   were 

originally  secreted.  The  dental  cavity  gradually 
diminishes  in  extent :  the  papilla  becomes  atrophied,  and  finishes  by  disap- 
pearing altogether  at  a  period  of  life  more  or  less  advanced,  according  to 
the  kind  of  teeth  and  species  of  the  animal. 

In  considering  the  entire  dental  apparatus,  with  regard  to  its  develop- 
ment, very  interesting  differences  are  remarked  in  the  progress  and  period 
of  evolution  ;  differences  which  have  been  made  available  for  ascertaining 
the  age  of  animals,  but  the  details  of  which  would  be  out  of  place  here. 
It  may  only  be  noted,  that  all  animals  have  two  successive  dentitions  :  the 
first,  composed  of  a  certain  number  of  teeth  designated  the  eadticous  [tem- 
porary, deciduous,  or  milk-teeth — cadiiqnes.  decaying  or  frail),  because  they 
are  soon  shed  and  give  place  to  others  which  are  stronger  and  more  solid 


PERMANENT  INCISOR  IN 
THE    HORSK. 

A,  Proper  membrane  of  the 
sac ;  IS,  Dental  pulp  ;  c, 


THE  MOUTH. 


349 


(and  also  because  they  appear  while  the  animal  is  yet  sucking) ;  the  second, 
comprising  the  latter,  are  named  replacing  teeth  ( remplarantes),  with  new, 
nun-deciduous  teeth  whicli  are  not  replaced,  and  are  therefore  named 
persistent  teeth.  (The  replacing  and  persistent  teeth  are  generally  included 
by  us  in  the  term  permanent.) 

B.  Teeth  of  Sompeds. — The  dentition  of  adult  Solipeds  is  composed 
of  from  36  to  40  teeth,  thus  distributed  in  each  jaw :  male,  6  incisors,  2 
canines,  12  molars;  female,  6  incisors,  12  molars.  With  regard  to  the 
first  dentition,  it  comprises  the  incisors  and  three  anterior  molars  only,  the 
canine  teeth  and  the  three  posterior  molars  being  persistent. 

The  latter  teeth — those  of  tlie  second  dentition — otler  in  their  develop- 
ment a  common,  but  very  remarkable  character,  rarely  met  with  in  the  other 
animals.  They  are  thrust  up  from  the  alveoli  during  the  entire  life  of 
the  animal,  to  replace  the  surfaces  worn  off  by  friction  ;  so  that  the  crown 
is  lormed  successively  by  the  various  portions  of  the  fang,  each  of  which 
issues  in  its  turn  from  the  alveolar  cavity. 

Ikcisoks. — These  are  so  named  because  they  serve,  particularly  in  the 


Fig.  157. 


THIN   SECTION   OF    THE    INNER    PORTION    OF    THE    DENTINE    AND    OF    THE    SURFACE 
OF    THE    PULP    OF    AN    INCISOR   TOOTH. 

Portion  iu  which  calcificrttion  is  complete,  showing  separate  globular  masses  at 
the  line  of  iunction  with  the  iincalcitied  substance,  h ;  at  c  are  seen  oval  masses 
of  germinal  matter  (cells),  with  formed  material  on  their  outer  surface ;  d, 
Terminal  portiolis  of  nerve  fibres. 

Herbivora,  for  the  incision  {incido.  to  cut)  of  the  food.  They  are  arranged 
in  the  segment  of  a  circle,  at  the  extremity  of  the  jaw,  and  are  distinguished 
by  the  names  of  pincer,  intermediate  or  lateral  (mitoyennes),  and  corner 
teeth.  The  pincers  are  the  two  middle  teeth,  the  intermediates  the  next, 
and  the  cor)iers  occupy  the  extremities  of  the  incisive  semicircle. 

The  general  form  of  these  teeth  is  that  of  a  trifacial  pyramid,  jiresenting 
an  incurvation  whose  concavity  is  towards  the  mouth.  The  base  of  this 
pyramid,  formed  by  the  crown,  is  flattened  before  and  behind ;  the 
summit,  or  extremity  of  the  fang,  is,  on  the  contrary,  depressed  on  both 
sides ;  the  shaft  of  the  pyramid  offers,  at  different  points  of  its  height,  a 
series  of  intermediate  conformations  which  are  utilised  as  characteristics 
of  age,  the  continual  pushing  outwards  of  the  teeth  bringing  each  of  them 
in  succession  to  the  frictional  surface  of  the  crown  (Fig.  159,  1). 

Examined  in  a  young  tooth  which  has  completed  its  evolution,  the  free 
portion  exhibits :  an  anterior  face,  indented  by  a  slight  longitudinal  groove, 
which  is  prolonged  to  the  root;  a  posterior  face,  rounded  from  side  to  sidej 


350 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


Fi?.  158. 


two  borders,  of  which  the  internal  is  always  thicker  than  the  external; 
lastly,  the  surface  of  friction  {table).  The  latter  does  not  exist  in  the  tooth 
which  has  not  been  used;  but  in  its  stead  is  found  two  sharp  margins 
circumscribing  a  cavity  named  the  external  dental  cavity  for  better,  in- 
fundihulum).       This    cavity    terminates    by   a    conical    cul-de-sac,   which 

descends  more  or  less  deeply  into  the  sub- 
stance of  the  tooth.  The  margins  are  dis- 
tinguished into  anterior  and  posterior ;  the 
last,  less  elevated  than  the  tirst,  is  cut  by  one 
or  more  notches  which  are  always  deepest  in 
the  corner  teeth.  It  is  by  the  wear  of  these 
margins  that  the  surface  of  friction  is  formed, 
and  in  the  centre  of  which  tlie  infundibulum 
persists  during  a  certain  period  of  time 
(Fig.  159,  •2)._ 

The  fang  is  perforated  by  a  single  aper- 
ture, through  which  the  pulp  of  the  tooth 
penetrates  into  the  internal  cavity  (Fig. 
159,  3,  c). 

In  the  composition  of  the  incisor  teeth  is 
found  the  three  fundamental  substances  of 
the  dental  organ.  The  dentine  (Fig.  159,  3,  6) 
envelops,  as  has  been  shown,  the  pulp  cavity. 
That  which  is  deposited  in  this  cavity  after 
the  complete  evolution  of  the  tooth,  to  replace 
the  atrophied  jjulp,  has  always  a  yellower 
tint  than  the  dentine  of  the  first  forma- 
tion ;  it  forms  on  the  table  of  the  tooth  the 
mark  designated  by  Girard  the  dental  star 
(Fig.  159,  4,  c).  The  enamel  covers  the 
dentine,  not  only  on  its  free  portion,  but 
also  on  the  roots  of  the  incisors ;  it  is  not 
prolomicd,  however,  to  their  extremities.  It 
is  doubled  into  the  external  dental  cavity, 
lining  it  throughout  (Fig.  159,  3.  a);  and 
when  the  surface  of  friction  is  established, 
there  can  be  perceived  a  ring  of  enamel 
surrounding  that  surface,  and  an  internal  ring 
circumscribing  the  infundibulum :  the  first 
circle  forms  what  is  called  the  encircling 
enamel ;  the  second,  the  central  enamel  (Fig. 
159,  4,  ffl.  h). 

In  the  virgin  tooth,  the  latter  is  con- 
tinuous with  the  external  enamel,  and  passes 
over   the    border   which   circumscribes   the 

JAW    OF    THE    nORSE,    THE     TEETH  ,  .        xl  •     ^         TT,     1  mi  t 

SEEN  ON  THEIR  TABLES.  entraucc  to  the  mfundibuhim.     The  cement 

Consult  figure  21  for  the  dentition  of  ^^  applied  over  the  enamel  like  a  protectmg 


THE    DENTITION    OF    THE     INFERIOR 


the  upper  jaw. 


varnish ;  but  it  does  not  exhibit  the  same 
thickness  everywhere  :  on  the  salient  portions 
it  is  extremely  thin,  and  does  not  even  exist  when  the  tooth  has  been 
submitted  for  some  time  to  the  friction  arising  from  the  contact  of 
the  aliment,  the  lips,  and  the  tongue.  It  is  more  abundant  in  depressed 
situations,  as  in  the  longitudinal  groove  on  the  anterior  face,  and  particularly 


THE  MOUTH. 


351 


at  the  bottom  of  the  infnndibnlum.  Nevertheless,  the  quantity  accumulated 
in  this  cul-de-sac  is  not  always  the  same ;  we  have  seen  it  sometimes  almost 
null,  and  on  the  other  hand  we  possess  incisors  unworn,  or  nearly  so,  in 
which  the  cavity  is  almost  entirely  obstructed  by  the  crusta  petrosa.  We 
are  not  aware  that,  up  to  the  present  time,  any  account  has  been  taken  of 
these  differences  when  calculatii)g  the  progress  of  icear ;  but  it  may  be 
imagined  that  they  ought  to  influence  in  a  sensible  manner  the  period  at 
which  effacemeut  of  the  external  dental  cavity  takes  place. 


Fig.  159. 


INCISOR   TEETH   OP   THE   HORSE.      DETAILS   OF   STRUCTURE. 

1,  A  tooth  in  which  is  indicated  the  general  shape  of  a  permanent  incisor,  and  the 
particular  forms  successively  assumed  by  the  dental  table  in  consequence  of 
friction,  and  the  continued  pushing  outwards  of  these  teeth ;  2,  A  virgin  tooth, 
anterior  and  posterior  faces ;  3,  Longitudinal^  section  of  a  virgin  tooth,  intended 
to  show  the  internal  conformation  and  structure.  Kot  to  complicate  the  figure, 
the  external  cement,  and  that  amassed  in  the  infundibulum,  has  not  been 
exhibited.  4,  Transverse  section  for  the  same  purpose ;  a,  Encircling  enamel ; 
6,  Centi-al  enamel;  c.  Dental  star;  d,  Dentine;  5,  Deciduous  tooth. 

All  the  characteristics  just  indicated  belong  to  the  deciduous  teeth 
(Fig.  159,  5\  except  that  they  are  smaller  than  the  permanent;  that  they 
are  of  a  shining  milky-white  colour,  due  to  the  thinness  or  absence  of  the 
crusta  petrosa ;  that  they  show  at  the  point  of  union  between  the  free 
portion  and  the  root,  a  constriction  named  the  neclc  ;  that  their  crown  is  finely 
striated,  and  not  cannular,  on  the  anterior  face ;  that  the  external  cul-de-sac 


352  THU  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

(infundibulum)  is  shallow ;  and  that  they  are  not  constantly  pushed  out- 
wards from  their  cavities,  their  growth  ceasing  when  they  begin  to  be  used^ 
When  the  replacing  teeth  appear,  they  do  so  a  little  beliind  the  temporary 
ones,  whose  shedding  they  cause  by  gradually  destroying  their  roots,  which 
at  last  become  only  a  long  and  very  thin  shell  of  dentine. 

The  follicle  in  which  the  incisor  teeth  are  developed  shows  only  two 
papillfe ;  one  for  the  secretion  of  the  dentine,  lodged  in  the  internal  cavity 
of  the  tooth,  and  hollowed  into  a  cuj^-shape  at  its  free  extremity ;  the  other 
is  contained  in  the  external  cul-de-sao  (Fig.  156,  a.  b.  c). 

Tusks,  Fangs,  or  Canine  Teeth.^ — •"  The  tusks  of  Solipeds  only  exist  in 
the  male  ;  it  being  qiiite  exceptional  to  meet  with  them  in  the  female,  and 
even  then  they  ai'e  rarely  so  strong  as  in  the  male. 

"  These  teeth  are  four  in  number,  and  are  placed  one  at  each  side  of  the 
jaws,  a  little  behind  tlie  incisors,  to  which  the  lower  canines  are  much 
nearer  tlian  the  upper.  Between  tliem  and  the  first  molar  there  is  left  a 
considerable  space,  which  constitutes  the  bar  of  the  inferior  jaw. 

"  The  free  portion  of  the  tusk,  sliglitly  curved  and  thrown  outwards, 
particularly  in  the  lower  jaw,  offers  two  faces  :  au  external  and  an  internal, 
separated  from  one  another  by  two  sharj)  borders  inclined  to  the  imier  side, 
and  meeting  in  a  point  at  the  extremity  of  the  tooth.  The  external  face, 
slightly  rounded,  jDresents  a  series  of  fine  stride,  longitudinal  and  parallel. 

"  Tlie  internal  face  has  a  conical  eminence  in  its  ndddle,  whose  point 
is  directed  towards  that  of  the  tooth,  and  is  separated  from  each  border 
by  a  deep  groove. 

"  The  fang  of  the  tusk,  more  curved  than  the  free  portion,  bears 
internally  a  cavity  analogous  to  that  of  the  root  of  the  incisors,  and 
like  it,  this  diminishes  and  finally  disappears  as  it  advances  in  age  ;  but  it 
is  always  relatively  larger,  because  of  the  absence  of  the  infundibulum  in 
the  canine  teeth. 

"  The  form  we  have  described  for  the  tusks  is  that  which  they  present 
while  still  young.  As  the  Horse  grows  older  they  lose  their  whiteness, 
and  become  worn  in  an  irregular  manner,  and  this  most  frequently  by  the 
action  of  the  bit  or  snaffle;  for  the  difierence  in  2)osition  of  these  teeth  in 
the  two  jaws  does  not  allow  of  friction  between  them. 

"  The  canine  teeth  are  not  shed,  and  grow  but  once.  Some  veterinarians, 
and  amoug  them  Forthomme  and  Rigot,  have  witnessed  instances  in  which 
they  were  replaced  ;  but  the  very  rare  exceptions  cannot  make  us  look  upon 
these  teeth  as  liable  to  be  renewed.  We  must  not,  however,  confound  with 
these  exceptional  cases  the  shedding  of  a  small  spicula  or  point,  which,  in 
the  majority  of  Horses,  precedes  the  eruption  of  the  real  tusks." 

"  The  structure  of  these  teeth  is  much  simpler  than  that  of  the  incisors ; 
consisting,  as  they  do,  of  a  central  mass  of  dentine  hollowed  by  the  pulp 
cavity,  and  covered  by  an  external  layer  of  enamel,  on  which  is  deposited  a 
little  cement. 

"  The  disposition  of  the  developing  follicle  is  in  harmony  with  the 
simplicity  of  structure  of  the  tusks  ;  at  the  bottom  there  is  a  simple  and 
conical  papilla  for  the  internal  cavity;  on  the  inner  wall,  a  double  longi- 
tudinal ridge,  on  which  are  moulded  the  ridge  and  grooves  on  the  internal 
face  of  the  to'-)th," 

Molar  Teeth.- — "  The  molars  are  twenty-four  in  number— six  in  each 
side  of  each  jaw.    There  are  also  sometimes  supplementary  molars  met  with 

'  The  quotations  inchiderl  within  invertfd  commas  are  from  M.  Lecoq's  '  Traite  de 
I'Exterieur  du  Cheval  et  des  Principaux  Animaux  Domestiques.' 


THE  MOUTH. 


353 


in  front  of  the  true  ones,  and  which  may  be  four  in  number ;  but  these  are 
Small  teeth,  having  but  little  resemblance  to  the  others,  are  most  frequently 
shed  with  the  first  deciduous  molar,  and  are  not  reijlaced. 

"  Generally  considered,  tlie  molar  arcades  have  not  the  same  disposition 
in  both  jaws.  Wider  apart  in  the  superior  one,  they  form  a  slight  curve, 
■whose  convexity  is  outwards.  In  the  inferior  jaw.  on  the  contrary,  the  two 
arcades  separate  in  the  form  of  a  V  towards  the  back  of  the  mouth.  Instead 
of  coming  in  contact  by  level  surfaces,  the  molars  meet  by  inclined  j)lanes, 
arid  in  such  a  way  that  the  iuternal  border  is  higher  than  the  external 
in  the  inferior  molars,  while  the  opjjosite  takes  jilace  in  the  superior. 

"  Like  the  incisors,  each  molar  presents  for  study  a  free  and  a  fixed 
portion. 

'•  The  free  portion,  nearly  square  in  the  upper  molars,  longer  than  wide 
in  the  lower,  shows  at  the  external  surface  of  the  former  two  longitudinal 
grooves,  the  anterior  of  which  is  the  deepest,  and  which  are  continued  on 
the  encased  portion.  This  is  not  the  case  with  the  inferior  molars,  which 
have  but  one  narrow,  and  frequently  an  indistinct,  groove. 

Ficr.  160. 


PROFILE   OF   THE   UPPER   TEETH  OF   THE   HORSE.   MORE   ESPECIALLY   INTENDED   TO 
SHOW   THE    molars;    THE    FANGS    HAVE    BEEN    EXPOSED. 

a,  Molar  teeth  ;  b,  Supplenientarj-  molar  ,  c,  Tusk  ;  d,  Incisors. 

"  The  internal  face  in  both  jaws  only  shows  one  groove,  and  that  but 
little  marked :  it  is  j^laced  backwards  in  the  ujiper  molars,  and  is  most 
apparent  towards  the  root. 

"  The  anterior  and  posterior  faces  are  in  contact  with  the  cori'esponding 
faces  of  the  adjoining  molars,  except  at  the  extremities  of  the  arcades,  where 
the  isolated  face  is  converted  into  a  narrow  border. 

"  With  regard  to  the  table  of  the  tooth,  it  inclines,  as  we  have  already 
mentioned,  outwards  in  the  lower  jaw.  and  inwards  in  the  upper ;  a  circum- 
stance which  prevents  the  lateral  movements  of  the  jaws  taking  place  with- 
out separation  of  the  incisors,  which  separation  removes  them  from  friction.'' 
In  the  virgin  molar  this  face  is  completely  covered  with  enamel,  and 
irregularly  undulated.  In  it  may  be  recognised  the  entrance  to  the  two 
infundibular  openings,  which  are  prolonged  in  the  interior  of  the  organ  to 
the  extremity  of  the  root,  and  which  are  almost  entirely  filled  with  cement 
at  the  period  when  the  tooth  has  completed  its  evolution  ;  they  are  only 
vacant  before  the  secretion  of  this  crusta  petrosa.     In  the  tooth  which  has 


354  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA 

been  worn,  this  frictional  surface  assumes  a  particular  aspect,  which  will  bo 
indicated  with  most  advantage  to  the  student  by  examining  the  structure  of 
the  molar. 

"  The  root,  if  examined  a  short  time  after  the  eruption  of  the  free 
portion,  looks  only  like  the  shaft  of  the  latter,  without  any  appear- 
ance of  fangs,  and  has  internally  a  wide  cavity.  It  is  not  until  the  tooth 
begins  to  be  pushed  from  the  alveolus  and  its  crown  to  become  worn,  that 
its  fangs  are  formed ;  these  are  at  first  hollow,  and  afterwards  filled,  as  well 
as  the  cavity  of  the  tooth,  by  the  formation  of  a  new  quantity  of  dentine. 
From  this  time  the  fangs  cease  to  grow ;  but  the  tooth,  constantly  projected 
beyond  the  alveolar  cavity,  allows  the  walls  which  inclose  it  to  contract ;  so 
that,  in  extreme  old  age,  it  happens  that  the  shaft,  completely  worn  away, 
instead  of  the  tooth,  leaves  several  stumps  formed  by  the  fangs. 

"  The  molars  of  the  two  jaws  exhibit  a  variety  of  roots.  In  the  molars 
terminating  the  arcades,  either  above  or  below,  or  at  the  extremities  of  these, 
there  are  three  ;  while  the  intermediate  molars  have  four  fangs  in  the  upper 
jaw,  and  only  two  in  the  lower. 

"The  molars  are  separated  from  each  other  by  their  imbedded  portion, 
particularly  at  the  two  extremities  of  the  arcade ;  an  arrangement  which 
strengthens  them  by  throwing  the  strain  put  upon  the  terminal  teeth  towards 
the  middle  of  the  line." 

The  structure  of  the  molars  resembles  that  of  the  incisors,  though  it  is 
much  more  complicated.  The  internal  cavity  is  extremely  diverticulated, 
and  enveloped  by  the  dentine.  The  enamel  is  applied  in  a  layer  over  it,  and  is 
doubled  in  its  external  culs-de-sac  exactly  as  in  the  incisors.  There  is  also 
on  the  table  of  the  tooth  which  has  been  worn,  an  external  covering  of 
enamel,  and  two  circles,  or  rather  two  irregular  polygons,  of  central  enamel 
circumscribing  the  two  cavities.  In  the  superior  molars,  these  bands  of 
enamel  represent  a  Gothic  B,  having  a  small  appendix  on  the  loop  nearest 
the  entrance  to  the  mouth.  This  figure  is  modified  in  the  teeth  of  the 
lower  jaw,  the  enamel  of  the  infundibuli  being  continuous,  on  the  inner  side, 
with  the  external  enamel.  The  cement  is  extremely  abundant,  and  in  the 
upper  molars  its  total  quantity  nearly  equals  that  of  the  dentine ;  it 
accumulates  in  the  culs-de-sac  and  on  the  external 
'^"       ■  covering  of  enamel,  where  it  partially  fills  up  the 

flutings  on  the  faces  of  the  crown.  Prolonged 
steeping  of  a  molar  tooth  in  hydrochloric  acid 
easily  permits  the  isolation  of  these  elements. 

Owing  to  the  arrangement  above  described,  the 
section  of  an  adult  molar  tooth,  naturally  repre- 
sented by  the  surface  of  friction  (Fig.  161), 
exhibits,  outwardly,  a  layer  of  cement ;  next,  the 
external  enamel  ;  between  this  and  the  central 
jg  I)  E  enamel,  the  dentine,  always  yellower,  and  sometimes 

TRANSVERSE  SECTION  OF  A  ^^"""^  ^^''^^  ^^.  ^^^  middle;  kstly,  the  enamel 
horse's  upper  molar  bands  of  the  infundibuli,  and  the  crusta  petrosa 
TOOTH.  filling  them.     As  these  enamel   bands  are  much 

A,  External  cement;  B,  Ex-  harder  than  the  other  substances,  they  are  worn 

te'rnal  crusta  petrosa.  '      "  "^^e  table  of  the  tooth  has  also,  for  this  reason,  the 
ajipearance  of  a  veritable  mill-stone,  and  is  admi- 
rably disposed  for  the  trituration  of  those  fibrous  substances  on  which  the 
animal  usually  feeds. 


THE  MOUTH.  355 

The  follicle  whicli  develops  these  three  elements  of  the  molat  tooth, 
offers  at  the  bottom  an  enormous  papilla  divided  into  several  lobes,  which 
lie  together  for  their  wliole  length ;  lodged  in  the  internal  dental  cavity,  it 
gradually  decreaS3s,  like  the  papilla  in  the  other  kinds  of  teeth,  as  the 
cavity  becomes  diminislied  by  the  formation  of  new  dentine.  Opposite  to 
it  are  two  long  papillaa,  which  occupy  the  enamelled  infundibuli. 

"  It  was  believed  for  a  long  time  that  the  molars  of  Solipeds  were  all 
persistent  teeth.  This  error,  founded  on  the  authority  of  Aristotle,  was  so 
deeply  rooted,  that  although  Kuini,  towards  the  end  of  the  sixteenth  century, 
had  discovered  the  existence  of  two  temporary  molars,  Bourgelat  did  not 
believe  it  when  he  founded  the  French  Veterinary  Schools,  and  was  only  con- 
vinced when  Tenon  had  proved  by  specimens,  in  1770,  that  the  first  three 
of  each  arcade  are  deciduous. 

"  The  replacement  of  these  twelve  molars  is  not  at  all  like  what  happei.s 
with  the  incisors.  The  molar  of  the  adult  grows  immediately  beneath  the  tem- 
porary one,  and  divides  its  two  fangs  into  four,  until  its  body  is  reduced  to  a 
simple  plate  and  falls  off,  allowing  the  contracted  summit  of  the  permanent  to 
appear  ;  and  this  grows  up  until  it  is  soon  on  a  level  with  the  others  in  the  row. 

"  The  first  replacing  molar  is  always  a  little  more  elongated  than  that 
which  it  succeeds,  and  it  most  frequently  expels  at  the  same  time  the  sup- 
plementary molar ;  so  that  if  forty-four  teeth  be  developed  in  the  male 
Horse,  it  is  very  rare  that  they  are  all  present  at  the  same  time." 

4 

7.  The  Mouth  in  General. 

We  will  now  consider,  as  a  whole,  the  cavity  whose  various  parts  have 
been  studied  in  detail,  and  examine,  successively,  its  general  disposition, 
capacity,  and  mucous  membrane. 

General  disposition  and  capacity  of  the  mouth. — The  mouth  being  elon- 
gated in  the  direction  of  the  head,  offers  a  great  antero-posterior  diameter, 
and  two  small  diameters — one  vertical,  the  other  transverse.  The  first 
extends  from  the  base  of  the  epiglottis  to  the  anterior  opening  of  the  mouth  ; 
the  second,  from  the  palate  to  the  floor  of  the  mouth ;  and  the  third,  from 
one  jaw  to  the  other.  "When  the  jaws  are  in  contact,  the  space  included 
between  these  limits  is  divided  into  two  regions:  one  central,  the  other 
peripheral.  The  first  is  circumscribed  by  the  dental  arches ;  the  second 
is  comprised  between  these  arches  on  the  one  side,  and  the  cheeks  and 
inner  aspect  of  the  lips  on  the  other.  It  may,  therefore,  be  remarked, 
that  the  capacity  of  the  mouth  is  almost  null  in  these  regions.  The  cheeks 
and  lips,  in  reality,  lie  almost  exactly  against  the  alveolar  arches,  and  the 
tongue,  in  contact  with  the  palate  by  its  superior  surface,  almost  entirely 
fills  the  central  region.  If  the  jaws  separate  from  one  another,  and  the 
cheeks  recede  from  the  dental  arcades,  the  cavity  of  the  mouth  becomes 
enlarged  in  proportion  as  these  movements  are  extensive.  It  must  be 
remembered  that  the  separation  of  the  jaws  is  effected  in  an  angular  manner, 
and  that  the  dilatation  produced  in  the  mouth  by  this  movement  is  greater 
before  than  behind,  the  opening  of  the  angle  comprised  between  the  two 
jaws  being  directed  tow-ards  the  entrance  of  the  cavity. 

Mucous  membrane. — The  walls  of  the  buccal  cavity  are  covered  by  a 
tegumentary  membrane,  which  we  have  hitherto  only  examined  in  parts  in 
the  different  regions  it  covers,  but  which,  it  is  to  be  noted,  forms  here  a 
single  and  continuous  layer,  the  mucous  membrane  of  the  mouth. 

This  membrane  is  continuous  with  the  external  skin  at  the  margin  of  the 


356  TEE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

buccal  opening  ;  followed  from  this  point  into  the  interior  of  the  cavity  it; 
lines,  it  is  seen  to  spread  itself  at  first  over  the  internal  surface  of  the  lips, 
then  to  be  prolonged  backwards  on  the  cheeks  as  far  as  the  posterior  pillars 
of  the  tongue.  If  it  is  examined  above  and  below,  to  the  bottom  of  the 
groove  which  corresi)onds  to  the  point  of  insertion  of  the  lips  and  cheeks, 
it  is  seen  to  cover  the  maxillary  bones  and  envelop  the  base  of  the  teeth, 
where  it  constitutes  the  gums.  From  the  superior  dental  arcade,  it  extends 
over  the  palatine  arch  and  the  soft  palate.  And  from  the  inferior  arcade, 
it  descends  to  the  floor  of  the  mouth,  and  is  reflected  over  the  tongue  to  form 
a  covering  for  that  organ.  At  the  isthmus  of  the  fauces  it  is  continuous 
Avith  the  pharyngeal  mucous  membrane. 

The  organisation  of  the  mucous  membrane  of  the  mouth  is  perfectly  in 
harmony  with  the  digestive  acts  performed  in  that  cavity.  It  is  there 
where  the  alimentary  substances,  which  are  sometimes  very  hard,  very 
resisting,  and  covered  with  asperities,  are  crushed ;  and  to  escape  inevitable 
injury,  this  membrane  is  protected  by  a  very  thick  eiiidermis  in  those  places 
which  are  most  particularly  exposed  to  the  contact  of  these  substances,  such 
as  the  upper  surface  of  the  tongue,  the  palate,  and  the  cheeks ;  even  the 
corium  or  sub-ejiidermic  layer,  is  also  greatly  thickened.  But  nature  has 
not  made  this  provision  for  the  parts  \\hicli  are  removed  from  the  direct 
contact  of  alimentary  matters ;  as,  for  example,  on  the  lateral  asi^ects  of 
the  tongue,  where  the  buccal  membrane  is  delicately  organised. 

This  membrane  also  shows,  in  its  lingual  portion,  small  organs  fyr  the 
gustation  of  savours,  the  perception  of  which  is  one  of  the  most  important 
jjrejiaratory  acts  of  the  digestive  functions ;  as  the  sensation  resulting  from 
this  appreciation  constitutes  an  excitant  to  the  desire  for  food,  and  also 
informs  the  animal  of  the  good  or  bad  properties  of  the  substance  introduced 
into  the  mouth. 

DIFFERENTIAL   CHAKACTERS   IN   THE   MOfTH   OF   OTHER   THAN   SOLIFED   ANIMALS. 

Tliat  the  different  regions  of  tlie  mouth  in  the  domesticated  animals  should  oft'cr  some 
diver»ities  will  be  readily  conceived,  as  all  are  not  submitted  to  the  same  regime,  nor  do 
they  all  live  in  the  same  manner. 

RuJiiNANTS.  1.  LijJS. — The  lips  of  the  Ox  are  remarkably  thick  and  rigid,  and 
possessed  of  but  little  mobility,  notwithstanding  the  great  development  of  tlie  muscles 
that  move  them ;  so  that  they  only  concur  indirectly  in  the  prehension  of  food,  the 
tongue  being  charged  with  the  largest  share  in  this  important  task.  Tlie  upper  lip 
oifers  in  the  middle  of  its  external  surface  a  large  patch  destitute  of  hair,  variously 
coloured  in  dilierent  animals,  always  humid  in  health,  covered  by  small  depressed 
eminences,  and  perforated  by  minute  apertures,  through  which  the  secretion  of  numerous 
thick,  yellow,  subcutaneous  glandules  passes  to  the  surface.  This  space,  situated 
between  the  two  nostrils,  constitutes  the  muffle.  (Around  the  muffle  are  a  few  hairs 
sometimes,  of  the  nature  of  tentaculte.) 

In  the  Sheep  and  Goat  the  lips  are  thin  and  very  mobile,  and  take  an  active  part  in 
the  prehension  of  food.  The  upper  lip  does  not  show  any  muffle,  and  is  divided  "into 
two  portions  by  a  median  groove.  In  the  Sheep  this  groove  is  in  reality  a  iissure ;  so 
that  each  half  of  the  lip  can  be  readily  moved  independently  of  the  other.  (The  upper 
lip  is  covered  with  hair  in  both  animals.  The  Goat  has  a  long  tuft  of  hair  appended  to 
its  lower  lip,  the  beard.) 

2.  Cheeks. — On  the  inner  surface  of  the  cheeks  in  the  Ox,  Sheep,  and  Goat,  from  the 
commissure  of  tlie  lips  to  the  first  molar  tooth,  is  a  multituiie  of  long,  thick,  conical 
papillaj  directed  backwards.  Beyond,  there  are  only  small  round  elevations  and  a  single 
row  of  large  papillae  similar  to  tlie  preceding,  in  a  line  with  the  upper  molars.  In  the 
Sheep  the  mucous  membrane  is  sometimes  spotted  black. 

3.  Palate. — In  the  Ox,  the  palate  is  most  extensive.  Its  posterior  third  is  quite 
smooth,  and  the  transverse  ridges  (bats)  only  occupy  the  anterior  two-thirds.  (They  are 
usually  sixteen  in  number.)  They  are  not  curved,  but  are  cut  into  notches  on  their 
summit,  which  is  inclined  backwards.     In  the  Sheep  and  Goat,  as  also  in  the  Ox,  is 


THE  MOUTH. 


357 


remarked,  in  front  and  in  the  middle,  near  the  pad  that  replaces  the  upper  incisor  ti  eth 
a  kind  of  T,  the  stt-m  of  which  is  directed  forwards,  and  at  the  extremity  of  whose 
branches  is  a  very  narrow  aperture,  the  buccal  opening  of  Jacobson's  canal.  This  wii] 
be  described  with  the  nasal  cavities. 

4.  Tongue. — The  tongue  of  the  Ox  is  distinguished  by  the  enormous  development  of 
the  muscles  composing  it.  It  is  garnished  with  conical  papillaj  which  have  a  horny 
slieath,  and  whose  summits,  inclining  backwards,  give  the  tongue  a  very  rough  feel. 
In  this  animal  it  serves  for  the  prehension  of  food ;  its  mobility  is  very  great,  and  it  can 
be  carried  into  the  nostrils  with  ease.  (The  body  of  the  organ  is  rounder,  and  the  point 
finer  than  in  tiic  Horse  The  calicyforni  piipiliaj  are  spread  over  the  whole  of  its  dorsal 
surface  ;  and  at  tlie  root,  on  the  middle  line,  is  a  somewhat  deep  groove.) 

The  tongue  of  the  Shecj)  and  Goat  is  smaller,  proportionally,  than  that  of  Solipeds. 

5.  Soft   Palate. — It    may   be 


said,  in  a  general  manner,  that 
the  palatine  prolongment  is 
shorter  than  in  Solipeds.  (The 
isthmus  of  the  fauces  is  wider, 
however,  and  the  amygdalae,  very 
developed,  are  situated  in  the 
two  large  depressions  formed  on 
the  sides  of  the  soft  palate  by 
the  folding  of  the  mucous  mem- 
brane.) 

6.  Teeth.— The  teeth  of  the 
Oz  are  thirty-two  in  number, 
twenty-four  of  which  are  molars, 
arranged  as  in  the  Horse,  and 
eight  incisors  belonging  to  the 
lower  jaw.  The  latter  are  re- 
placed in  the  upper  jaw  by  a 
thick  cartilaginous  pad,  covered 
by  the  mucous  membrane  of  the 
mouth  :  this  pad  forms  tlie  gum, 
and  furnishes  a  bearing  for  the 
incisors  of  the  lower  jaw.  Some- 
times, as  in  the  Horse,  there  are 
found  supplementary  molars, 
wliich,  if  four  in  number,  will 
make  up  the  whole  to  thiity-six ; 
though  they  are  never  all  present 
at  one  time,  as  the  supplementary 
ones  are  shed  before  the  molar 
dentition  is  completed. 

The  composilion  of  the  Ox's 
teeth  is  the  same  as  those  of  the 
Horse,  the  only  difference  being 
in  tlie  arrangement  of  the  several 
substances. 

Incisors.  —  "  The  incisors, 
eight  in  number,  are  placed  en 
clavier  (like  a  key-board)  at  the 
extremity  of  the  kind  of  rounded 
shoulder-bone  by  which  the  max- 
illary bone  terminates,  forming 
around  this  point  a  perfect  circle 
when  they  have  acquired  their 
full  development. 

"Instead  of  being  fixed  in 
the  alveoli,  as  in  Solipeds,  they 
possess  a  certain  degiee  of  mo- 


Fig.  162. 


THE    TEETH    OF    THE    OX. 

1,  Upper  jaw,  with  a,  the  friction  surface,  and  h,  the 
external  surface ;  2,  Lower  jaw,  with  a,  the  dental 
tables,  and,  b,  the  external  face. 


bility,  sometimes  mistaken  for  a  diseased  condition;  this  is  necessary  in  order  to 
prevent  their  wounding  the  cartilaginous  pad  of  the  upper  jaw  against  which  they 
press.  They  are  divided,  according  to  their  position,  into  two  pincers,  two  Jirst  inter- 
mediates, two  second  intermediates,  and  two  corner  in.-isors. 

"  Each  incisor  offers  for  consideration  two  parts :  one  free,  the  other  encased,  con- 
26 


358 


THE  DIGESTIVE  APFAMATU8  IN  MAMMALIA. 


stitutiDgr  tlie  root,  and  separated  from  one  another  by  a  very  marked  constriction — the 
neck.  This  arrangement  gives  to  the  tooth  the  form  of  a  shovel,  the  root  representing 
the  handle  (fig.  163). 

"The  free  portion,  flattened  above  and  below,  and  thinnest  and  widest  towards  its 
anterior  extremity,  presents  two  faces — an  inferior  or  external,  the  other  superior  or 
internal ;  with  three  borders,  an  anterior  and  two  lateral. 

''  The  external  face,  slightly  convex,  and  milk-white  in  colour,  is  covered  with  fine. 


Fig.  163. 


ox's    INCISOR   TOOTH. 

,  Free  portion,  external  face,  outer 
border;  a',  Ijid,  internal  face,  outer 
border  ;  b,  Root ;  c.  Neck  ;  /,  Anterior 
border  ;  g,  g'  Inner  border. 


undulating,  longitudinal  strife,  which  disappear 
with  age,  and  leave  the  surface  beautifully 
polished  (fig.  163,  a). 

"  The  internal  face,  flatter  than  the  pre- 
ceding, presents  in  its  middle  a  slight  conical 
eminence,  whose  base  widens  and  is  terminated 
near  the  free  extremity  of  the  tooth,  while  its 
sides  are  circumscribed  towards  each  border  by 
a  well-defined  groove  (fig.  163,  a'). 

"  The  two  lateral  borders  (the  internal 
slightly  convex  in  its  length,  the  external 
slightly  concave  in  the  same  direction)  make 
the  free  portion  appear  as  if  thrown  outwards. 
The  anterior  border  is  sharp,  and  slightly  con- 
vex from  one  side  to  the  other ;  it  is  the  first 
part  of  the  tootli  destroyed  by  wear. 

'.'  Tlie  root  is  rounded,  slightly  conical,  and 
implanted  in  an  alveolus  of  tlie  same  form ;  in 
youth,  it  shows  at  its  extremity  an  opening 
communicating  with  an  internal  cavity  analo- 
gous to  that  in  the  teeth  of  SoliiDeds,  and  f)ro- 
longed  into  the  interior  of  tlie  free  portion 
(fig.  163,  b). 

"  In  the  virgin  tooth,  the  enamel  forms  around 
th0  free  portion  a  continuous  layer,  thinnest  on 
the  internal  surface,  and  extending  very  scantily  over  a  part  of  tlie  root. 

"  The  dentine  composes  the  remainder  of  the  organ,  and  the  (pulp)  cavity,  which 

is  originally  a  large  space  of  the  same  form  as  the  tooth,  is  filled,  as  the  animal  grows 

old,  bv  new  dentine,  which,  as  in  the  Horse,  has  a  yellower  tint  than  the  primitive  ivory. 

"  When  tlie  cavity  is  completely  filled,  the  tooth  censes  to  grow,  and  is  not  pushed 

beyond  the  alveolus  during  wear,  like  the  teeth  of  the  Horse. 

"  The  incisor  tooth  has  scarcely  arrived  at  its  perfect  development  before  it  begins  to 
be  worn.  Its  horizontal  position,  and  its  coming  in  contact  with  the  pad  on  the  upper 
jaw,  exposes  the  anterior  border  and  superior  tace  to  friction,  and  consequent  wear 
from  before  to  behind.  The  wear,  therefore,  chiefly  affects  this  upper  face,  which  really 
forms  the  table  of  the  tooth,  and  which  Girard  designated  the  avale.  Wlien  use  has 
worn  away  the  conical  eminence  and  the  grooves  bordering  it.  the  tooth  is  levelled. 

"As  wear  goes  on,  there  appears  at  fiist,  and  at  the  extremity  of  the  tooth,  a  yellow 
band,  which  is  the  dentine  denuded  of  its  enamel ;  and  later,  in  this  ivory  a  yellower 
transverse  band  shows  itself.  With  increase  of  wear,  this  contracts,  then  widens,  and 
finishes  by  forming  a  mark  nearly  square,  and  then  round,  which  is  nothing  else  than 
the  recently-formed  dentine  that  fills  the  pulp  cavity  of  the  tooth.  It  is  a  veritable 
dental  star,  analogous  to  that  in  the  Horse's  tooth,  and  varying  in  form  according  to  the 
incisor  in  which  it  appears. 

"  In  proportion  as  the  teeth  are  used,  they  seem  to  separate  from  one  another, 
although  they  btill  remain  in  the  same  places.  This  is  because  these  teeth,  in  youth, 
only  touched  each  other  by  their  extremities,  and  as  they  became  worn  they  decreased  in 
width,  and  necessarily  became  separated  to  an  extent  varying  with  their  degree  of  wear. 
"  Finally,  when  the  tooth  has  reached  its  last  stage  of  wear,  there  only  remains  the 
root,  the  upper  portion  of  which,  becoming  apparent  by  the  retreat  of  the  gum,  stands  as 
a  yellow  stump,  very  distant  from  those  which  form  witli  it  the  remains  of  the  incisive 
arcade. 

"The  first  incisors  (or  milk-teeth)  of  the  Ox,  like  those  of  the  Horse,  are  all  deciduous, 
and  differ  from  those  which  replace  them  by  their  smaller  volume,  less  width,  the 
transparency  of  their  enamel,  and  their  being  more  curved  outwards.  Their  roots  are 
much  ehorter,  and  are  destroyed  by  the  succeeding  teeth.  The  two  temporary  pincers 
are  always  separated  by  a  marked  interval,  depending  on  the  thickness  of  the  fibro- 
cartilage  inrthe  maxillary  symphysis  during  youth." 


THE  MOUTH.  359 

MoLAES. — "  As  in  Solip6(ls,  the  molars  are  six  in  each  siae  of  tlie  jaws,  but  they  are 
much  smaller,  and  form  a  much  si lorter  arcade.  Their  reciprocal  volume  is  far  from 
l)ting  as  uniform  as  in  the  Horse,  but  goes  on  augmenting  from  the  first  to  the  sixth  ;  and 
to  such  a  degree,  that  the  space  occupied  by  the  three  anterior  molars  is  only  about  one- 
half  of  that  required  for  the  three  posterior  ones  ;  the  last  molar  alone  occupies  nearly 
four  times  as  much  space,  lengthwise,  as  the  first. 

"  Their  wearing  surface,  coastructed  on  the  same  system  as  that  of  the  Horse's  molars 
presents  eminences  a  little  more  acute," 

The  arrangement  of  their  three  constituents  is  in  principle  the  same  as  in  the  latter 
animal. 

"■  As  in  the  Horse,  the  three  front  molars  are  deciduous. 

"The  teeth  of  the  Sheep  and  Goat  are,  like  those  of  the  Ox,  thirty-two  in  number, 
divided  into  eight  incisors  and  twenty-four  molars,  to  which  are  sometimes  added 
supplementary  molars. 

"  The  incisors  of  the  smaller  Ruminants  are  not  disposed  like  a  key-board,  as  in  the 
Ox,  but  stand  up  to  form  a  grip,  resting  against  the  pad  on  the  upper  jaw  much  more 
by  their  extremity  than  by  their  inner  surface. 

"  They  are,  besides,  narrow,  have  scarcely  any  neck,  and  are  fixed  more  solidly  in  the 
alveoli  (fig.  164). 

"  Their  external  face  is  white  and  polished,  and  is  encased  towards  the  gum  in  a 
kind  of  black  cement. 

'•The  internal  face  has  two  wide,  longitudinal  grooves,  separated  towards  the  middle 
of  the  table  by  a  simple  ridge,  which  replaces  the  conical  eminence  of  the  Ox's  incisor. 
These  grooves  are  nearly  always  lined  with  the  black  cement-like  substance. 

"  The  incisors  of  the   Sheep  are,  like  the  Ox's,  distinguished  into  temporary  and 
replacing  teeth ;  the  first  are  known  from  the  others  by 
their  smallness,  and  particularly  by  their  narrowness.  F'g-  164. 

"  The  wear  of  the  incisors  in  the  Sheep,  from  their 
position,  ought  to  take  place  nearer  the  anterior  border 
tlian  in  tiie  Ox ;  the  dental  star  is  observed  more 
promptly,  and  always  forms  a  narrower  line  from  before  to 
behind. 

*■  Tlie  absence  of  a  neck  in  these  teeth  is  the  reason 
why  they  never  appear  to  separate  with  wear,  as  has  been 
remarked  in  the  Ox. 

''  The  molars  have  the  greatest  resemblance,  in  their  incisor  teeth  of  a  sheep 
general  form  and  relative  proportions,  to  those  of  the  Ox."  two  years  old. 

PiG.-"l.  Lips.— In   this  animal   the  lips  are  widely    The  second  intermediates  and 
cleft.    The  lower  is  pointed  and  little  developed  ;  the  upper        ,  he  corner  incisors  have  not 
is  confounded  with  the  snout,   which    will   be  described        yg^^  jjggu  replaced, 
with  the  nostrils."   (The  upper  lip  has  but  little  mobility.) 

"  2.  Cheeks. — These  are  small  and  thin,  and  the  mucous  membrane  smooth. 

"3.  Falafe. — Narrow  and  elongated,  it  is  disposed  as  in  the  Hoi-se.  In  front  is  seen 
the  orifices  of  Jacobson's  canals."  (The  transverse  ridges  are  twenty  to  twenty-two  in 
numbir,  the  anterior  being  larger  than  the  posterior,  and  their  free  borders  are  united). 

"4.  Toncjue. — 5.  Soft  Pahile. — These  two  organs  are  the  same  as  in  the  smaller 
Euminants,  except  that  the  filiform  papillae  are  perhajis  less  developed."  (The  isthmus 
of  the  fauces  is  circular,  and  the  posterior  pillars  are  confounded  with  the  mucous 
membrane  at  the  upper  part  of  the  oesophagus.  Its  anterior  surface  has  several  conical 
eminences  in  the  middle,  and  the  aiiiygdahe  are  little  rounded  elevations.) 

'•  6.  Teeth. — The  Pig  has  forty-four  teeth,  which  are  divided  into  twelve  incisors, 
four  canines  and  twenty-eight  molars"  (fiij.  165). 

"The  incisors,  six  in  taih  jaw,  exhibit  very  remarkable  difierences  between  each 
othrr.  'i"he  pincers  and  the  intermediates  of  the  upper  jaw  offer,  by  their  form  and  the 
cavity  they  show  on  their  table,  some  analogy  to  those  of  the  Horse.  In  the  lower 
jaw,  these  teeth  are  straight,  directed  forwards,  and  bear  some  resemblance  to  the 
incisors  of  rodent  animals.  The  corner  incisors  of  both  jaws  are  isolated  between  the 
intermediate  and  canine  teeth,  and  are  not  nearly  so  voluminous  as  the  other  incisors. 

"The  tujks  are  very  developed,  particularly  in  the  male,  and  cross  eacii  other  during 
the  life  of  the  animal ;  they  project  from  tiie  mouth,  and  form  a  very  dangerous  weapon 
in  the  wild  boar.     The  primary  canines  are  deciduous  like  the  incisors. 

"  The  molars,  seven  in  each  row,  increase  in  volume  from  the  first  to  the  last,  which 
is  very  strong.  Their  tables  hold  a  middle  place,  with  regard  to  disposition,  between 
that  of  the  Carnivora  and  Herbivora. 

"Caknivora. — 1.  Lips. — The  Carnivora,  like  the  Pig,  do  not  use  their  lips  to  grasp 


360 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


tlieir  food,  and  they  are  therefore  thin,  though  movable.  The  upper  lip  of  the  Bog  has 
a  groove  in  the  middle  line,  and  it  covers  the  lower  lip  more  or  less  at  tlie  sides 
acGorchng  to  the  breed.  The  lower  lip  is  always  scalloped  on  its  free  border  near  the 
commissures,  which  are  very  high.  In  the  Cat,  the  hairy  tentaculse  are  collected  on 
the  upper  lip  into  two  long  lateral  tufts,  the  moustaches ;  they  are  very  sensitive  and 
movable. 

"  2.  Cheels. — 3.  Palate. — The  cheeks  resemble  those  of  the  Pig ;  the  palate  that  of 
Ruminants.  The  mucous  membrane  is  often  stained  by  patches  of  pigment,  especially  on 
the  palate."  (The  latter  is  frequently  quite  black.  The  number  of  ridges  varies  from 
seven  to  nine.    Jacobson's  canal  opens  behind  the  incisors.) 

"  4.  Tongue. — This  is  thin  and  very  movable.  The  papillse  on  its  upper  face  vary 
somewhat  in  the  Cat  and  Dog.    In  the  former,  the  filiform  papillse  on  the  anterior  two- 

Fis.  165. 


THE   TEETH   OF   THE   PIG. 

1,  Upper  teeth,  table  surface  ;  2,  Lower  teeth,  table  aspect ;  3,  Lateral  view  of  the  jaws. 

thirds  of  tlie  tongue  are  covered  by  a  very  strong  horny  sheath,  whose  point  is  directed 
backwards.  In  the  Dog  these  papillje  are  less  developed,  and  there  are  observed,  more 
particularly,  a  number  of  composite  filiform  papillae  whose  divisions  are  very  flexible. 
There  also  are  found  regularly  disposed  among  these,  white  shining  epithelial  particlis 
which  correspond  to  the  fungiform  papillse. 

"At  the  base  of  the  tongue  of  Carnivora,  and  within  the  anterior  pillars  of  the  soft 
palate,  are  two  elongated  bodies  with  rounded  extremities  and  a  bosselated  slippery 
surface;  these  are  veritable  amygdalx.  formed  by  an  agglomeration  of  closed  follicles. 

"5.  Soft  Palate. — In  the  Dog  and  Cat,  the  soft  palate  is  very  short,  and  the 
isthmus  of  the  fauces  wide.  Consequently,  these  creatures  breathe  easily  by  the  mouth, 
and  expel  matters  by  it  from  the  stomach  during  vomiting.  At  its  free  border  the  soft 
palate  shows  a  small  prolongation,  something  like  the  uvula. 


THE  MOUTH. 


361 


"6.  Teeth. — The  teeth  of  the  Dog  are  forty-two  in  nmnber:  twelve  incisors,  four 
canines,  and  twenty-six  molars. 

"  The  incisors,  six  in  each  side  of  the  jaws,  are  more  developed  in  the  superior  than 
in  the  inferior  maxilla,  and  are  divided,  as  in  the  Horse,  into  pincers,  intermediates,  and 
corner  incisors;  the  last  being  much  stronger  than  the  preceding,  and  these  again 
stronger  than  the  pincers. 

"  Their  free  part  presents,  in  the  virgin  tooth,  three  tubercles :  a  middle,  which  is  the 
strongest,  and  two  lateral ;  these,  together,  are  not  unlike  a  trefoil  or  the  upper  part  of  a 
fleur-de-lis,  especially  those  in  the  upper  jaw.  On  the  internal  face  is  remarked  a  table 
or  slope,  somewhat  resembling  that  of  the  Ox  and  Sheep,  and  separated  from  the  root 
by  a  very  distinct  border  whose  extremities  mark  the  lateral  lobes.  This  table  is  of  no 
advantage  in  ascertaining  the  age. 

"The  root,  very  developed,  flattened  on  both  sides,  and  separated  from  the  free 

Fig.  166. 


Fi2.  167. 


GENERAL   AND   LATERAL   VIEW    OF    THE    DOG'S   TEETH. 

portion  by  a  well-defined  neck,  is  solidly  encased  in  a  deep  alveolus.     Its  internal  cavity 
is  very  promptly  obliterated. 

"  When  the  tooth  is  submitted  to  wear,  the  middle  lobe  is  the  fu-st  to  disappear;  so 
that  it  no  longer  resembles  a  trefoil  (fig.  167). 

"The  caducous  incisors  are  much  smaller  and  more  pointed  than  the  permanent 
ones;  yet,  like  them,  they  show  lateral  lobes.  At  the  period  of  their  eruption  these 
teeth  are  somewhat  widely  apart. 

"  The  fangs,  or  canine  teeth,  two  in  each 
jaw,  are  very  strong,  elongated  organs,  conical 
in  form,  curved  backwards  and  outwards,  and 
placed  immediately  after  the  incisors. 

"The  upper  fangs  are  the  thickest,  and 
have  a  small  space  between  them  and  the  corner 
incisors,  in  which  the  inferior  canines  are  lodged. 

"  These  teeth  are  deciduous,  like  the  incisors, 
and  are  distinguished  from  tlie  replacing  ones 
by  their  being  thinner  and  more  elongated. 

"They  are  worn  more  or  less  quickly,  ac- 
cording to  the  kind  of  food  the  animal  obtains, 
and  are  sometimes  broken  in  fighting. 

"  The  molars  are  distributed  in  the  two 
jaws,  twelve  being  fixed  in  the  upper  and  four- 
teen in  the  lower.  Nearly  all  of  them  are 
terminated  by  somewhat  acute  lobes,  proper  for  tearing  animal  food.  The  strongest 
in  each  jaw  is,  for  the  upper,  the  first  back-molar  or  fourth  in  the  row,  and  in  the  lower, 
the  fifth.     All  in  front  of  these  are  deciduous." 


ANTERIOR    VIEW    OF    THE    INCISORS    AND 
CANINE   TEETH   IN   A   YEAR- OLD   DOG. 


362 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


After  tlieir  complete  eruption  from  the  alveolar  cavities,  the  Dog's  teeth  are  no  longer 
pushed  outwards.  They  are  remarkable  for  their  brilliant  whiteness,  which  they  owe 
to  tlie  absence  of  cement  on  their  covering  of  enamel. 

The  Cat  has  thirty  teeth :  twelve  incisors,  four  tusks,  and  fourteen  molars,  eight  of 
which  are  in  the  upper,  and  six  in  the  lower  jaw. 

All  these  teeth  are  cunstructed  on  tlie  same  type  as  those  of  the  Dog.  The  tusks  are 
deeply  striated  on  their  external  sur'ace,  in:;tead  of  being  smooth. 

(Tlie  importance  of  a  correct  knowledge  of  the  period  of  eruption,  shedding,  replacing, 
and  o-eneral  wear  of  the  teeth  of  the  domesticated  animals,  as  a  guide  to  their  age, 
induces  me  to  give  the  table  on  page  363  (from  Leyh),  as  indicating  at  a  glance  the  age 
at  which  the  teeth  appear,  are  shed,  and  leplaced  in  the  different  ci'eatures: 

Baumeister  divides  the  successive  evolutions  in  the  wear  of  the  tables  of  the  Horse's 
incisor  teeth  into  four  periods — from  six  years  to  extreme  old  age.  The  first,  the  trans- 
versely-oval period,  extends  from  six  to  twelve  years  ;  the  round,  from  twelve  to 
eighteen  years ;  the  triangular,  from  eighteen  to  twenty-four  years,  and  the  antero- 
posterior oval  or  triangul-.ir,  from  twenty-four  years  and  upwards.  Girard  and  other 
French  authorities  shorten  these  periods  somewhat.  The  triangular  period,  for  instance, 
only  lasts  from  fourteen  to  seventeen  years.) 

COMPARISON   OF  THE   MOUTH   OF   MAN   WITH   THAT   OF   ANIMALS. 

The  brevity  of  Mail's  face  influences  the  shape  of  the  mouth ;  therefore  it  is  propor- 
tionally shorter  and  wider  than  in  the  domesticated  mammals. 

Fi?.  168. 


MEDIAN    ANTERO-POSTERIOR   SECTION  OF   THE    HUMAN    FACE. 

a,  Septum  of  nose,  with  section  of  hard  palate  below  it ;  6,  Tongue ;  c,  Section  of 
soft  palate ;  dj  d,  Lips ;  ?',  Uvula ;  r,  Anterior  arch,  or  pillar  of  fauces  ;  i.  Pos- 
terior arch  ;  i,  Tonsil ;  p,  Pharynx  ;  /;,  Hyoid  bone  ;  k,  Thyroid  cartilage  ,  n,  Cricoid 
cartilage  ;  s.  Epiglottis  ;  v.  Glottis  ;  1,  Posterior  opening  of  nares  ;  3,  Isthmus 
faucium  ;  4,  Superior  opening  of  larynx ;  5,  Passage  into  ossophagus ;  6,  Orifice 
of  right  Eustachian  tube. 


THE  MOUTH. 


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Sti. 

364  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

1.  Lips. — The  lips  have  a  thick,  free,  everted  border.  They  are  lined  by  a  rosy 
mucous  membrane,  which  is  insensibly  continued  inwards  by  the  buccal  membrane. 
The  upper  lip  is  limited  by  the  uo.se  and  the  naso-labial  furrow ;  the  lower  is  limited  by 
the  men  to-labial  groove.  The  first  has  in  its  middle  the  subnasal  fuirow.  Their 
structure  is  analogous  to  those  of  animals. 

2.  Cheelcs. — The  cheeks  are  limited  by  the  inferior  border  of  the  maxilla,  the  root  of 
the  ear,  the  prominence  of  the  chin,  and  the  naso-labial  furrow.  Between  the  skin  and 
the  mucous  membrane,  there  is  fouud,  as  in  brutes,  a  glandular  layer  and  muscles, 
chiefly  the  buccinator.  An  adipose  ball  is  always  fouud  near  the  anterior  border  of  the 
masseter. 

3.  Palate.— It  does  not  possess  a  vascular  membrane,  as  in  the  Horse,  and  its  mucous 
membrane  shows  a  longitudinal  and  transverse  furrows  in  its  anterior  two-thirds.  It 
is  pale  and  resisting. 

4.  Tongue. — This  is  thick,  short,  and  broad;  its  base  is  almost  vertical,  and  in  the 
middle  is  a  perpendicular,  fibrous,  and  semilunar  lamina,  the  Ungual  septum  which  gives 
insertion  to  muscular  fibres. 

Anthropotomists  distinguish  intrinsic  and  extrinsic  muscles.  The  first  are :  the 
lingualis  superior  and  inferior,  transversus,  and  longitudinalis.  The  second  are,  as  in 
Solipeds,  the  stylo-glossus,  genio-glossus,  hyo-glossus,  and  phuryngo-glossus.  There  is 
also  described  a  palato-glossus,  which  partly  belongs  to  the  solt  palate. 

The  mucous  membrane  shows  the  different  characters  recognised  in  that  of  animals. 
That  of  the  dorsal  face  is  divided  into  two  portions  by  two  A-shaped  rows  of  papillas, 
-whose  summit  abuts  on  the  deep  mucous  foUicle  named  the  foramen  cxcum.  The 
posterior  portion  presents  depressions  which  correspond  to  the  closed  follicles,  and  the 
fungiform  and  calyciform  papillae ;  the  anterior  portion  has  a  villous  aspect,  due  to  the 
great  inmaber  of  filiform  papillae  covering  it. 

5.  Soft  Palate. — In  Mao,  the  soft  palate  is  short  and  divided  into  two  portions :  an 
anterior,  horizontal,  attached  to  the  base  of  the  tongue  by  the  anterior  pillars  of  the 
curtain;  a  posterior,  movable  and  oblique,  having  a  free  porti.m.  the  uvula,  and  fixed  to 
the  lateral  walls  of  the  pharynx  by  the  posterior  pillars.  The  amygdala',  or  mass  of 
closed  follicles,  are  lodged  in  the  triangular  space  between  the  anterior  and  posterior 
pillars.  The  fibrous  structure  is  not  present,  unless  the  small  expansion  of  the 
external  tensor  of  the  palate  represents  it.  The  muscles  are  the  same  as  in  animals, 
and,  in  addition,  there  are  described  two  palato-glossal  muscles,  included  between  the 
mucous  folds  that  form  the  anterior  pillars.  The  palato-pharyngeus  extends  to  the 
posterior  nasal  spine.     The  isthmtis  of  the  fauces  is  wider  than  in  the  Carnivora. 

6.  Teeth. — -The  teeth  are  thirty-two  in  number,  sixteen  in  each  jaw.  They  are 
distributed  in  the  following  manner :  four  incisors,  two  canines,  two  small  molars 
(hicuspidati),  and  three  large  molars  (inuUi-cusp>iaati). 

Tlie  incisors,  when  viewed  in  profile  or  longitudinal  section,  have  a  ■wedge-shape,  and 
their  free  border  is  more  or  less  sharp.  The  canines  are  irregularly  conical ;  the  molars 
have  a  multiple  fang,  and  the  crown  is  studded  with  a  variable  number  of  tubercles:  two 
on  each  small  molar  and  four  on  the  large.  In  youth,  there  are  only  twenty  teeth,  ten 
in  each  jaw. 

THE    SALIVARY   GLANDS. 

The  salivary  glands  are  secretory  organs  annexed  to  the  buccal  cavity, 
into  which  they  pour  saliva :  a  recrementitious  fluid  that  softens  the  food, 
favours  its  mastication  and  deglutition,  and  has  a  chemical  action  upon  it 
after  its  arrival  in  the  abdominal  portion  of  the  digestive  canal. 

Though  very  diversified  in  form,  yet  they  j^resent  in  their  structure  such 
common  characters,  that,  to  obviate  a  recurrence  to  their  organisation  when 
speaking  of  each  gland,  we  will  describe  it  here. 

The  salivary  glands  are  constituted  by  a  red  or  yellow  spongy  tissue, 
which  is  divided  into  small,  rounded,  or  polyhedral  masses,  called  salivary 
lobides.  These  extend  in  a  layer  beneath  the  adlierent  fece  of  the  mucous 
membrane,  and  remain  isolated  from  each  other,  or  are  agglomerated  in  a 
body  to  form  a  single  gland.  In  the  latter  case  they  are  united  by  condensed 
connective  tissue,  which  is  disposed  over  the  surface  of  the  organ  as  a  very 
thin  enveloping  membrane,  and  into  the  lobular  interstices  in  lamellar 
prolongations. 


THE  SALIVARY  GLANDS. 


365 


In  studying  the  organisation  of  one  of  these  lobules,  it  will  be  observed 
that  it  is  made  up  of  many  very  small  secondary  lobules  or  acini,  wliich  are 
themselves  due  to  the  agglomeration  of  minute  elementary  vesicles  or 
follicles,  whose  average  diameter  is  from  1 -500th  to  1-1 200th  of  an  inch ; 
these  open  into  the  little  canal  belonging  to  each  of  the  secondary  lobules, 
and  which  again  joins  those  of  the  other  acini  of  the  primary  lobule,  to  form 
a  single  duct. 

The  minute  elementary  vesicles  or  follicles,  the  glandular  culs-de-sac  (or 
ultimate  follicles)  consist  of  a  thin  amorphous  membrane  (memhrana  propria), 
lined  by  a  layer  of  j)olygonal  epithelium  cells.  (They  are  closely  sur- 
rounded by  a  plexus  of  capillary  blood-vessels). 

When  the  salivary  lobules  remain  isolated,  this  canal,  which  is  designated 
as  excretory,  because  it  carries  from  the  lobnle  the  saliva  secreted  within  the 
elementary  follicles,  opens  directly  into  the  mouth.  But  when,  on  the 
contrary,  they  all  unite  and  form  a  single  gland,  their  excretory  canals 
finally  converge  into  one  or  more  principal  ducts,  whose  termination  in 
every  case  takes  place  in  the  same  manner — by  oi:)euing  into  the  mouth 
from  the  summit  of  a  more  or  less  salient  tubercle,  an  arrangement  which 
FiV.  169.  Fiff.  170. 


LOBtTLE  or  PAROTID  GLAND,  INJECTED  WITH  CAPILLARY    NETWORK     AROUND    THE    FOLLI- 

MERCURY,  AND  MAGNIFIED  50  DIAMETERS.  CLES  OF   THE   PAROTID   GLAND. 

renders  the  introduction  of  particles  of  food  into  these  excretory  orifices 
somewhat  difiicult.  The  fibrous  and  elastic  walls  of  these  ducts  are  lined 
internally  by  columnar  epithelium. 

If  to  the  fundamental  tissue  just  described,  be  added  arteries,  veins,  and 
lymphatics,  which  convey  the  materials  of  secretion  and  nutrition,  as  well  as 
the  nerves  which  regulate  the  secretory  and  nutritive  acts,  all  the  elements 
entering  into  the  organisation  of  the  salivary  glands  are  made  known. 

The  most  voluminous  of  these  glands — or  those  which  comprise  a  very 
great  number  of  agglomerated  lobules,  will  be  first  noticed.  They  are 
the  parotid,  maxillary,  sublingual,  and  molar  glands,  which  are  all  pairs,  and 
are  placed  in  proximity  to  the  mouth  when  they  do  not  lie  immediately 
beneath  the  adherent  face  of  its  mucous  membrane.  Secondly,  the  less  im- 
portant glands — those  which  are  spread  in  layers  under  that  membrane,  and 
including  the  labial,  lingual,  and  palatine  glands,  will  be  examined. 

1.  Parotid  Gland.     (Figs.  110  ;    172,  8). 
Preparation. — This  gland,  with  its  excretory  canal,  is  seen  after  the  removal  of  the 
cervico-facial  subcutaneous  a,n(l  parotido-auricularis  nauscles. 

The  parotid  gland  is  situated  in  the  space  included  between  the  posterior 


366 


THE  DIGESTIVE  APPARATCS  IN  MAMMALIA. 


border  of  the  inferior  maxilla  and  the  transverse  process  of  the  atlas.  It  is 
elongated  from  above  to  below,  flattened  on  both  sides,  and  divided  into 
two  faces,  two  borders,  and  two  extremities. 

The  exfernnl  face,  nearly  plane,  is  hollowed  in  its  inferior  part  into  a 
longitudinal  channel,  which  is  sometimes  transformed  into  a  complete  canal, 
and  lodges  the  jugular  vein  after  it  has  traversed  the  gland  from  below 
to  its  superficies  This  external  face  responds  to  the  jiarotido-auricularis 
muscle,  the  subcutaneous  muscle,  the  atloideau  loop,  a  cervical  ramification 
of  the  facial  nerve,  and  the  posterior  auricular  vein.  The  internal  face  is 
very  uneven  and  moulded  on  the  subjacent  parts.  It  covers  the  guttural 
pouch,  the  mastoid  insertion  of  the  small  oblique  muscle  of  the  head, 
levator  humeri,  stylo-hyoideus,  the  tuberosity  on  the  posterior  border  of 
the  OS  hyoides,  the  digastricus,  the  tendon  of  the  sterno-maxillaris,  and 
the  submaxillary  gland,  which  is  sej)arated  from  it  by  the  thin  cellulo- 
aponeurotic  layer  uniting  the  latter  muscle  to  the  levator  humeri ;  also  to 

Fig.  171 


MODES   OF    TERMINATION    OF    THE    NERVES    IN    THE   SALIVARY   GLANDS. 

1,  2,  Branching  of  tlie  nerves  between  the  salivary  cells;  3,  Termination  of  the 
nerve  in  the  nucleus;  4,  Union  of  a  ganglion  cell  with  a  salivary  cell;  5,  Varicose 
nerve-fibres  entering  the  cylindrical  cells  of  the  excretory  ducts. 

the  external  carotid  artery  and  its  two  terminal  branches,  the  posterior 
auricularis,  the  muscles  of  the  jaw,  and,  lastly,  the  facial  nerve,  which  often 
passes  through  the  substance  of  the  gland. 

The  anterior  border  of  the  gland  is  intimately  imited  to  the  posterior 
border  of  the  maxilla;  it  is  related  to  the  tempoi-o- maxillary  articulation, 
the  subzygomatic  vessels  and  nerves,  and  the  maxillo-muscular  vessels. 
The  posterior  border  is  thicker  than  the  preceding,  and  is  separated  from  the 
transverse  process  of  the  atlas  by  the  terminal  aponeurosis  of  the  levator 
humeri,  to  which  it  is  only  feebly  adherent :  it  can  also  be  easily  separated 
from  it,  in  order  to  raise  the  parotid  and  pass  through  the  stylo-hyoideus 
muscle,  in  the  operation  of  hyo-vertebrotomy. 

The  superior  extremity  is  bifurcated,  and  embraces  the  base  of  the  concha 
of  the  ear.  The  inferior  extremity  is  comprised  in  the  angle  formed  by  the 
imion  of  the  jugular  and  glosso-facial  veins. 


THE  SALIVARY  GLANDS. 


367 


Vessels  and  nerves  of  the  parotid  gland. — This  gland  receives  its  blood 
by  a  multitude  of  arterial  branches  from  the  large  vessels  it  covers.  Its 
nerves  are  very  numerous,  and  are  derived  from  the  facial  and  inferior 
maxillary  nerves,  and  the  carotid  plexus. 

Excretory  canal. — The  parotid  gland  is  provided  with  a  single  excretory 
canal,  the  duct  of  Stenon,  so  named  from  the  anatomist  who  gave  the  first 
good  description  of  it.  It  is 
detached  from  the  anterior 
border  of  the  gland,  near  its 
inferior  extremity,  where  the 
eye  may  readily  follow  it  be- 
tween the  lobules  to  the  three 
or  four  principal  branches 
from  which  it  originates  (Fig. 
172).  At  first  in  contact 
with  the  terminal  tendon  of 
the  sterno-maxillaris,  it  after- 
wards turns  round  the  pos- 
terior border  of  the  digastric 
muscle  (stylo-maxillaris  por- 
tion), advances  into  the  sub- 
maxillary space,  creeps  over 
the  internal  masseter  muscle 
(pterygoid),  beneath  the 
glosso-facial  vein,  and  arrives 
at  the  maxillary  fissure,  into 
which  it  enters  with  the 
aforesaid  vein  and  corre- 
sponding artery,  but  behind 
both.  It  then  ascends  ex- 
ternally along  the  anterior 
border  of  the  masseter 
muscle  to  the  level  of  the 
inferior  molars,  when  it 
passes  beneath  its  two  satel- 
lite vessels,  obliquely  crosses 
their  direction,  and  pierces 
the  cheek  towards  the  third 
ujjper  molar  tooth,  opening 
into  the  mouth  by  a  large 
tubercle. 

The  parotid  duct  is  com- 
posed of  two  membranes : 
the  internal,  mucous,  with 
columnar  epithelium ;  and 
the  external,  made  up  of  con- 
nective tissue,  and  circular  and  longitudinal  elastic  fibres 


INFERIOR   ASPECT    OF    HEAD    AND    NECK. 

1,  Inferior  border  of  lower  jaw ;  2,  Genio-hyoideus ;  3, 
Mylo-hyoideus ;  4,  Submaxillary  artery ;  5,  Ditto 
vein ;  6,  Parotid  duct ;  7,  Sterno-maxillaris  tendon ; 
8,  Parotid  gland ;  9,  Sterno-maxillaris  muscle ;  10, 
11,  12,  Submaxillary  glands;  13,  Sterno-thyro- 
hyoideus  and  subscapulo-hyoideus  muscles ;  14,  Thy- 
roid gland  ;  15,  Pterygoideus  interuus. 


2.  Maxillary  or  Submaxillary  Gland.     (Figs.  172,  173.) 
Preparatiim. — To  expose  this  <:land,  as  well  as  the  sublingual,  divide  the  maxilla,  as 
in  preparing  the  muscles  of  the  tongue  lor  dissection  (see  p.  334). 

This  gland,  smaller  than  the  preceding,  is  situated  in  the  intermaxillary 
space,  on  the  lateral  plane  of  the  larynx,  and  within  the  j^arotid  gland. 


368 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


It  is  long  and  narrow,  flattened  on  both  sides,  and  describes  a  sligbt 
curve  with  the  concavity  turned  upwards :  a  form  which  allows  it  to  be 
studied,  with  regard  to  relations,  on  two  faces,  two  borders,  and  two 
extremities. 

By  its  external  face,  it  responds  to  the  internal  pterygoid  muscle,  the 
digastricus,  the  sterno-maxillaris  tendon,  and  the  cellulo-aponeurotic  layer 
separating  it  from  the  parotid.  Its  internal  face,  applied  to  the  side  of  the 
larynx,  responds,  sujieriorly,  to  the  guttiu-al  pouch,  to  the  carotid  artery, 
and  to  the  nerves  which  accompany  that  vessel  in  the  upper  part  of  the 
neck. 

The  superior  border,  thin  and  concave,  is  margined  by  the  middle  part  of 
the  digastricus.  The  inferior,  thick  and  concave,  is  in  contact  with  the 
glosso-facial  vein. 

The  posterior  extremity  is  maintained  beneath  the  transverse  process  of 


Fis.  173. 


MAXILLARY    AND   SUBLINGUAL   GLANDS. 

R,  Maxillary  gland ;  s,  Wharton's  duct ;  T,  Sublingual  gland. 

the  atlas,  by  an  extremely  loose  and  abundant  cellular  tissue  ;  the  anterior  is 
insinuated  between  the  internal  pterygoid  and  the  thyro-hyoideus  muscle. 

Vessels  and  nerves. — The  blood  is  distributed  to  the  maxillary  gland  by 
various  small  innominate  arteries,  like  those  of  the  parotid  gland,  and  which 
are  most  frequently  derived  from  the  external  carotid  and  the  glosso-facial. 
The  nerves  are  principally  furnished  by  the  carotid  plexus. 


THE  SALIVARY  GLANDS.  369 

Excretory  Canal. —  Wliartons  duct,  as  it  is  termed,  is  long  and  narrow; 
has  very  attenuated  walls,  and  exists  for  nearly  tlie  whole  length  of  the 
sajjerior  border  of  the  gland  :  sometimes  on  its  internal  face,  where  it  receives 
the  raniilications  from  various  lobules.  At  the  anterior  extremity  of  the 
organ  it  becomes  free,  and  passes  forward  between  the  mylo-hyoidous  and 
basio-  (hyo-)  glossus  muscles.  After  crossing,  outwardly,  the  glosso-facial 
artery  and  great  hypoglossal  nerve,  and,  inwardly,  the  tendon  of  the  digas- 
tricus  and  the  lingual  nerve,  it  passes  between  the  hyo-glossus  lonffus  and 
the  sublingual  gland,  lying  closely  to  the  inner  side  of  the  latter ;  thus  it 
extends  parallel  to  the  lateral  groove  (or  channel)  of  the  lingual  canal  (on 
the  floor  of  the  mouth).  Jt  finally  arrives  near  the  fraenum  of  the  tongue, 
but  underneath  the  buccal  membrane,  and  opens  into  the  mouth  by  a  small, 
but  very  salient,  floating  tubercle,  situated  a  little  in  advance  of  the.frsnumj 
and  vulgarly  named  the  barb  (barbillon). 

The  structure  of  Wharton's  duct  is  identical  with  that  of  Stenon,  but  its 
external  tunic  is  extremely  thin,  and  has  not  any  circular  elastic  fibres. 

3.  Sublingual  Gland.     (Fig.  173.) 

This  is  less  in  volume  than  the  preceding,  and  is  situated  under  the 
tongue,  in  the  intermaxillaiy  space. 

Elongated  from  before  to  behind,  and  very  flat  laterally,  it  has,  like 
the  submaxillary  gland,  two  faces,  two  borders,  and  two  extremities,  whose 
relations  we  will  briefly  indicate. 

The  external  face  is  covered  by  the  mylo-hyoideus  muscle;  the  internal 
responds  to  Wharton's  duct  and  the  genio-glossus  and  hyo-glossus  langus 
muscles.  The  nj>2^er  border  projects  beneath  the  mucous  membrane  on  the 
floor  of  the  mouth,  where  it  forms  the  sublingual  ridge ;  the  inferior,  thin 
and  sharp,  is  comprised  between  the  mylo-hyoideus  and  the  genio-glossus 
muscles.  The  two  extremities  are  thin  and  tapering;  the  posterior  contains 
a  branch  of  the  lingual  nerve ;  the  anterior  extends  to  the  bottom  of  the 
angle  formed  by  the  union  of  the  two  branches  of  the  inferior  maxilla. 

Vessels  and  nerves. — This  gland  possesses  a  special,  but  small  artery— the 
sublingucd  Its  nerves  come  from  the  lingual  nerve,  and  even  from  the 
carotid  plexus. 

Excretory  canals. — These  number  fifteen  or  twenty,  and  are  named  the 
ductus  Riciniani.  Flexuous  and  very  slender,  they  are  detached  from  the 
superior  border  or  internal  face  of  the  gland,  ascend  perpendicularly,  and 
open  into  the  mouth  on  the  sublingual  crest  or  ridge  by  a  linear  series 
of  small  orifices  pierced,  as  usual,  in  the  centre  of  a  tubercle. 

4.  Molar  Glands. 

These  are  so  named  because  they  are  disposed  parallel  to  the  molar  arches. 
There  are  two  on  each  side. 

The  superior  molar  gland,  the  most  considerable,  represents  a  narrow 
line  of  salivary  lobules  placed  outside,  and  along  the  upper  border  of,  the 
alveolo-labialis  muscle.  In  its  posterior  part,  where  it  is  concealed  beneath 
the  masseter  muscle,  this  gland  is  thicker  and  more  compact  than  in  front, 
where  the  few  lobules  which  compose  it  scarcely  come  in  contact  with  each 
other. 

The  inferior  molar  gland,  less  lobulated  and  voluminous,  and  not  so 
wide  as  the  preceding,  is  placed  at  the  inferior  border  of  the  buccinator, 
immediately  beneath  the  mucous  membrane  of  the  mouth,  and  near  the 


370  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

point  where  it  is  reflected  from  the  side  of  the  cheek  on  to  the  inferior 
maxillary  bone.  It  is  bordered,  for  the  whole  of  its  extent,  by  the  buccal 
nerve. 

Both  glands  poiu*  their  secretion  into  the  mouth  by  numerous  salient 
orifices,  which  can  be  seen  arranged  in  line  on  the  buccal  membrane,  parallel 
to  each  molar  arcade. 

It  may  he  remarked  that  these  glands  establish  a  transition  between  the 
preceding  and  those  yet  to  be  mentioned.  Their  lobules  are  far  from 
representing  so  compact  an  agglomeration  as  that  formed  by  the  parotid  or 
sublingual  lobules ;  and  they  tend  to  separate  from  each  other  to  become 
more  independent.  Therefore  it  is  that  many  writers  regard  them  as  distinct, 
and  describe  them  as  superior  and  inferior  molar  glands. 

5.  Labial,  Lingual,  and  Palatine  Glands. 

The  lobules  composing  these  glands  are  spread  in  layers  more  or  less 
thick  on  the  inner  face  of  the  mucous  membrane,  instead  of  being 
agglomerated  in  masses,  as  in  the  previous  glands.  Sometimes  they  are 
scattered,  in  consequence  of  their  small  number.  In  general,  the  excretory 
duct  of  each  glandule  opens  independently  into  the  mouth,  without  com= 
municating  with  those  of  the  neighbouring  lobules. 

Labial  Glandidce. — These  are  more  abundant  in  the  upper  than  in  the 
lower  lip,  and  pass  beyond  the  commissures  to  be  spread  for  a  short  distance 
over  the  inner  aspect  of  the  cheeks.  It  is  easy,  in  the  living  Horse,  after 
turning  up  the  lip  and  carefully  wiping  it,  to  see  the  salivary  fluid  secreted 
by  these  small  organs  escape  by  their  excretory  ducts. 

Lingual  Glandules. — They  form  a  layer  under  the  mucous  membrane  at 
the  base  of  the  tongue,  and  adhere  very  closely  to  the  fibres  of  the  small 
hyo-glossus  muscle,  and,  laterally,  are  continuous  with  the  layer  which 
covers  the  external  face  of  the  amygdaloid  mucous  membrane.  They  are 
also  found  on  the  side  of  the  tongue,  above  the  superior  border  of  the  hyo- 
glossus  longus  muscle ;  though  these  are  few  and  scattered,  and  look  as  if 
incrusted  in  the  substance  of  the  hyo-glossus  muscle. 

Staphyline  (or  Palatine)  glandidce.  —  The  thick  layer  these  form  under  the 
anterior  mucous  covering  of  the  soft  palate  has  been  described  with  that 
organ.  We  have  only  to  observe  here,  that  it  is  continuous,  laterally,  with 
the  glands  at  the  base  of  the  tongue,  through  the  medium  of  the  glandulaB  of 
the  amygdaloid  cavity ;  and  in  such  a  manner,  that  the  part  of  the  mouth 
immediately  in  front  of  the  isthmus  of  the  fauces,  and  which  might  bo 
justly  considered  as  the  isthmus  itself,  is  enveloped  in  a  complete  glandular 
zone.  In  the  dead  body,  we  always  find  in  this  compartment  a  greater  or 
less  quantity  of  viscid  fluid,  which  is  certainly  secreted  by  this  zone.  It  is 
here,  then,  that  the  alimentary  bolus  is  enveloped  in  the  glutinous  matters 
intended  to  favour  its  passage  in  the  pharynx  and  oesophagus ;  and  it  is 
worthy  of  notice  that  the  constricted  passage  where  this  secretion  is  poured 
out  in  the  living  animal,  immediately  precedes  the  canal  traversed  by  the 
bolus  of  food  in  the  act  of  deglutition. 

DIPFEEENTIAL    CHARACTERS   IN   THE   SALIVARY    GLANDS   OF   OTHER   TUAX   SOLIPED 

ANIMALS. 

The  snlivary  system  of  the  Hcrbivcra  is  more  extensive  than  that  of  tlie  Omnivora, 
and  especially  the  Carnivora. 

Ruminants. — 1.  Parotid  gland. — The  paiotid  glands  of  the  Ox  are  distinguished  by 


THE  SALIVARY  GLANDS.  371 

their  meagre  development  and  red  colour,  which  contrasts  markedly  with  the  pale  yellow 
hue  of  the  maxillary  glands.  In  the  Sheep  and  Goat,  Steuou's  duct  passes  through  the 
masseter  muscle.  (In  the  Ox,  this  gland  otfers,  at  the  upper  part  of  its  anterior  border,  a 
round  lobe  lying  on  the  masseter.  Steuon's  duct  opens  into  the  mouth  at  the  fifih  molar. 
It  terminates  in  the  Sheej)  and  Goat  at  the  fourth  molar.) 

2.  Maxillary  gland. — In  the  Ox  this  gland  is  much  thicker  than  in  Solipeds,  its 
Tolume  being  m  inverse  relation  to  that  of  the  parotid.  In  its  posterior  moiety  it 
enlarges  into  an  oval  lobe  which,  below  the  larynx,  lies  against  that  of  the  opposite  tide. 
Whurlon  s  duct  follows  the  same  course  as  in  the  Horse ;  the  papilla  through  which  it 
opens  is  hard,  resisting,  and  notched,  and  is  lodged  in  an  elliptical  fossette  near  the 
incisors. 

3.  Sublingual  gland. — In  the  Ox,  Sheep,  and  Goat,  this  gland  comprises  two 
portions :  a  posterior,  somewhat  voluminous  and  lobulated,  provided  with  a  special 
excretory  duct  which  follows  and  opens  near  Wharton's  duct  (by  the  ductus  Bartho- 
linianus) ;  and  an  anterior,  pouring  out  its  secretion  by  many  canals,  and  representing 
the  gland  proper.  This  arrangement  allows  the  saliva  to  be"  collected  separately  from 
this  gland. 

4.  Molar  glands. — These  are  more  developed  in  Ruminants  than  in  Solipeds,  The 
upper  one  is  enlarged  at  its  posterior  extremity. 

Pig. — The  parvtid  gland  of  tiiis  animal  is  little  developed,  as  in  Ruminants,  and 
Stenon's  duct  follows  the  posterior  border  of  the  lower  jaw.  (Leyh  says  that  it  is,  pro- 
portionately, largely  developed  :  that  its  upper  end  does  not  reach  the  conch  of  the  ear, 
and  that  Steuou's  tiuct  opens  at  the  sixth  molar.) 

The  sublingual  gland  is  analogous  in  its  disposition  to  that  of  the  Ox.  Cuvier,  in  his 
'Let/ons  d'Anatomie  Compare'e,' indicates  this: — -"ThePtj/  has  two  sublingual  glands. 
One,  very  long  and  narrow,  accompanies,  outwardly,  the  excretory  canal  of  the  sub- 
maxillary gland,  from  the  angle  of  the  jaw  to  the  second  sublingual.  It  is  composed  of 
small  lobules  of  a  pale  red  colour.  Its  excretory  duct  arises  near  the  posterior  third,  and 
passes  along  with,  but  to  the  outside  of,  the  submaxillary  duct.  It  terminates  m  ar  tie 
orifice  of  the  latter  by  a  small  opening  ;  its  diameter  is  equally  small.  Tin-  second  Gub- 
lingual  gland  is  placed  before  the  first:  its  form  is  square  and  flattened,  and  the  lobes  of 
which  it  is  composed  are  larger  and  redder.  It  has  from  eight  to  ten  excretory  ducts."  (In 
this  animal  the  duct  of  Wharton  does  not  open  into  the  mouth  by  a  papilla  ;  consequently 
there  is  no  barb.) 

Carnivora. — The  parotid  of  the  Dog  and  Cat  is  small,  and  Stenon's  duct  always 
passes  through  the  masseter.  (It  opens  at  the  fourth  molar  in  the  Dog,  and  tiie  third  in 
the  Cat.) 

In  the  Dog  the  submaxillary  glands  are  larger  than  the  parotids.  "  They  even  havo 
in  front,  along  Wharton's  duct,  a  small  accessory  gland,  with  a  distinct  excretory  canal 
opening  into  the  same-papilla  as  Wiiarton's."  (Leyh  states  that  the  submaxillary  duct 
does  not  project  into  the  mouth).    The  supplementary  ghmd  is  absent  in  tlie  Cat. 

The  sahiingual  gland  is  not  present  in  the  Dog ;  it  is  very  small  in  the  Cat,  and 
carried  further  back  than  in  the  other  animals.  (Leyh  describes  a  tublmgiial  gland  as 
present  in  the  Carnivora,  and  which  is  divided  into  two  portions,  as  in  the  Pig:  the 
anterior  being  formed  of  detached  lobules  that  open  into  the  mouth  liy  several  ducts ; 
and  the  posterior,  larger  above  than  below,  with  two  ducts,  the  smaller  opening  into 
Wharton's  duct,  and  the  larger  a  little  in  front  of  it.) 

The  upper  molar  gland  of  the  Dog,  scarcely  noticeable  for  the  greater  part  of  its 
extent,  forms  posteriorly,  under  the  zygomatic  arch,  near  the  eye,  an  independent  lobe, 
remarkable  for  its  large  size  and  its  single  excretory  rluct.  Duvernoy  who  first 
described  it,  proposed  to  name  itthe  subzygomatic  ghmd.  It  is  not  present  in  the  Cat. 
(This  is  doubtless  the  organ  described  by  Leyh  as  the  orbital  gland,  which,  he  says,  is 
only  foun;l  in  the  Dog;  the  superior  molar  gland,  according  to  him,  not  existing  in  that- 
animal.  This  orbital  gland  is  external  to  the  ocular  muscles,  has  three  or  four  excretory 
canals  (the  ductus  Nuckiani)  which  converge  into  one  duct  that  opens  into  the  mouth 
above  tl;e  last  molar.) 

The  labial,  lingual,  and  palatine  glandulx  are  much  less  developed  in  the  Carnivora 
than  the  Herbivora.  This  predominance  of  the  salivary  system  in  the  latter  i-*  suffi- 
ciently accounted  ft)r,  when  we  consider  the  hard,  fibrous,  and  coriaceous  food  these 
animals  live  upon,  and  which  must  be  ingested  in  large  quantity,  bec.iu.-e  of  the  small 
amount  of  nutrition  it  contains.  For  its  mastication  and  deglutition  a  great  amount  of 
saliva  is  absolutely  necessary. 


372 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


COBIPAKISON   OF   THE   SALIVABY   GLANDS   OF   MAN   WITH   THOSE   OF   ANIMALS. 

As  in  animals,  the  parotid  is  the  most  voluminous  of  the  salivary  glands.  Its  tissue 
is  reddish-grey  and  lobulated,  the  lobules  adliering  closely  to  each  other.  Its  shiipe  is 
irregular,  and" it  is  moulded  to  the  excavation  behind  the  angle  of  the  Jaw.  Steuon's 
duct  passes  across  the  masseter,  and  shows  on  its  course  some  salivary  lobules,  forming 
what  is  named  the  accessory  parotid  (or  socia  ;parotidis) ;  it  opens  opposite  the  third 
uijper  molar. 

The  submaxillary  gland  weighs  about  half-an-ounce.  It  is  partly  situated  beneath 
the  deep  cervical  fascia,  and  partly  within  tlie  boily  of  the  lower  jaw,  between  the  mylo- 
hyoideus  and  hyo-glossus  muscles.  Its  lobules  are  more  loosely  united  than  those  of  the 
parotid.  Wharton's  duct  opens  on  the  sides  of  the  frsenum  linguae  by  a  small  opening  at 
the  apex  of  a  round  papilla  (carM?icu?a  sublingualis). 

The  sublingual  gland  is  analogous  to  that  of  the  Ox  and  Pig.  There  are,  in  fact,  two 
sublinguals  ;  an  anterior  about  the  size  of  an  almond,  and  furnished  witli  a  single 
excretory  canal — the  ductus  Bartholini,  that  terminates  near  Wharton's  duct;  the  other, 
posterior,  formed  by  several  isolated  lobules  with  multiple  excretory  ducts,  the  ductus 
Riviniani. 

There  are  also  labial,  palatine,  and  lingual  glands:  with,  besides,  near  the  frseuum, 
a  small  conglomerate  gland,  the  gland  of  Nuhn,  which  has  a  special  duct. 


Fig.  174. 


PHARYNGEAL  AND  LARYNGEAL  RE- 
GION; THE  POSTERIOR  PART  OF 
THE  HEAD  INCISED  AND  THROWN 
FORWARD. 

1,  Base  of  the  cranium  ;  2,  Roof  of 
the  pharynx ;  3,  Muscles  of  the 
cheek  ;  4,  4,  Walls  of  the  pharynx  ; 
6,  Septum  nasi  ;  7,  Posterior 
openings  of  nostrils  ;  8,  Entrance 
to  the  mouth ;  9,  Epiglottis ;  10, 
Posterior  pillars  of  soft  palate  ;  11, 
Arytenoid  cartilages  ;  12,  Opening 
of  the  oesophagus  ;  13,  (Esophagus  ; 
14,  Trachea. 


THE   PHARYNX.       (FigS.   174,  175.) 

Preparation. — 1.  Study  the  general  disposition 
and  situation  of  this  vestibule  in  the  antero- 
posterior vertical  section  of  the  head  (fig.  175). 
2.  In  order  to  examine  the  interior  conveniently, 
the  head  sliourd  be  separated  from  the  neck, 
leaving  attached  to  it  a  certain  portion  of  the 
trachea  and  cesophagus ;  then  by  sawing  across, 
either  through  or  behind  the  temporo-maxillary 
articulations,  all  that  portion  of  tlie  cranium  is  re- 
moved, and  the  posterior  parietes  of  the  pharynx  is 
exposed,  and  may  be  dissected  to  study  the  muscles 
(Fig.  178),  or  opened  in  the  middle  line  to  reach 
the  interior  of  the  cavity  (Fig.  174).  3.  The  muscles 
should  be  dissected  with  those  of  the  tongue,  and 
in  the  same  manner. 

Tlie  pharynx  is  a  membranous  vestibule 
common  to  the  digestive  and  air  passages, 
and  situated  behind  the  soft  palate,  which 
separates  it  from  the  moiith ;  above,  it  is  at- 
tached to  the  base  of  the  cranium,  and,  below, 
to  the  laryngeal  apparatus. 

Form  and  internal  disposition. — In  con- 
sequence of  the  conformation  of  the  soft 
palate,  which,  in  the  domesticated  animals, 
and  particularly  in  Solipeds,  is  prolonged  to 
the  base  of  the  epiglottis,  the  pharynx  forms 
a  cylindrical  cavity  elongated  from  before  to 
behind,  enclosed  laterally  and  posteriorly 
by  vnde  thin  muscles,  and  with  the  soft 
palate  for  an  anterior  wall.  At  the  two 
extremities  of  this  cavity  are  openings  which 
allow  the  pharynx  to  communicate  with  the 
other  passages  or  cavities,  and  whose  dis- 
position we  will  at  once  begin  to  study. 

At  the  upper  extremity  of  the  large 
axis  of  the  pharyngeal  cavity  is  to  be  re- 
marked:     1,   In    front,   the    two   posterior 


THE  PHARYNX.  373 

openings  of  the  nasal  cavities ;  2,  Behind,  and  directly  opposite  the  pre- 
ceding, the  two  pharyngeal  ojienings  of  the  Eustachian  tubes,  which  are 
closed  by  a  cartilaginous  kind  of  clap-valve.^ 

At  the  inferior  extremity  of  this  axis  is  found :  1,  In  the  centre,  a  vast 
gaping  orifice  projecting  into  the  anterior  of  the  pharyngeal  cavity,  like  a  tap 
into  a  cask :  this  is  the  entrance  to  tJie  larynx,  the  salient  portions  of  which 
form,  on  the  walls  of  the  pharynx,  two  lateral  gutters  limited  superiorly  by 
the  posterior  pillars  of  the  soft  palate ;  2,  In  front  of,  and  beneath  this,  is 
the  isthmus  of  the  fauces ;  Behind  and  above,  the  oesophageal  opening  at  the 
bottom  of  an  infundibulum,  which  may  be  considered  as  a  special  region  of 
the  pharynx. 

These  seven  openings  of  the  pharyngeal  cavity  give  it  the  appearance  of 
a  cross  road,  into  which  abut  different  thoroughfares.  It  is  necessary  to 
note  that  the  air  and  digestive  passages  intersect  each  other  here,  and  in 
such  a  way  that,  during  deglutition,  the  bolus  of  food  passes  over  the  entrance 
of  the  larynx  to  reach  the  oesophageal  opening.  This  peculiarity  is  easily 
seen  by  referring  to  figure  175. 

Fis;.  175. 


MEDIAN   LONGITUDINAL  SECTION   OF   HEAD   AND   UPPER   PART   OF   NECK. 

1,  Upper  lip;  2,  Premasilla ;  3,  Hard  palate;  4,  Tongue;  5,  Septum  nasi;  6,  Nasal 
bone;  7,  Palate  bone;  8,  Soft  palate;  9,  Pterygoid  bone;  iO,  Epiglottis;  11, 
Entrance  to  Eustachian  tube ;  12,  Arytenoid  cartilage ;  13,  Cricoid  cartilage ; 
14,  (Esophagus;  15,  Frontal  bone  and  sinus;  16,  Cerebrum;  17,  Corpus  cal- 
losum  ;  18,  Cerebellum  ;  19,  Sphenoid  bone  ;  20,  Medulla  oblongata  ;  21,  Cervical 
ligament ;  22,  Spinal  cord  ;  23,  Occipital  bone  ;  24,  24,  Atlas  ;  25,  25,  Dentata  ; 
26,  Trachea. 

Belations. — Viewed  externally,  for  the  study  of  its  connections,  it  will  be 
found  that  the  pharynx  responds,  posteriorly,  to  the  guttural  pouches  and 
guttural  lymphatics ;  laterally,  to  the  large  branch  of  the  os  hyoides,  the 

1  This  reo^ion  corresponds  to  the  posterior  nares  (arriere  fond)  of  Man,  a  diverticulum 
■which  cannot  be  distinguished  from  the  pharynx  in  the  domesticated  animals.  Under 
the  designation  of  the  posterior  nares  of  the  'nasal  fossae,  it  will  be  understood  that  we 
mean  the  posterior  extremities  of  these  cavities. 

(In  the  'Annates  de  Me'decine  Viterinaire.'  of  Brussels,  for  1871  (p.  244),  M.  Lorge 
describes  a  pharyngeal  caecum  as  existing  in  Solipeds,  which  he  states  corresponds  to  the 
naso-pharyngeal  region,  or  posterior  nares,  of  Man.) 
27 


374  THE  DIGESTIVE  ATTARATL'S  IN'  MAMMALIA. 

internal   pterygoid  and    stylo-hyoid  muscles,  the  glosso-pharyngeal,  great 
hypoglossal,  and  superior  laryngeal  nerves,  and  the  glosso-facial  artery. 

Steucture. — The  walls  of  the  pharynx  are  composed  of  a  mucous  mem- 
h'ane,  external  to  which  is  a  muscular  layer. 

1.  Mucous  membrane. — This  membrane  is  covered,  externally,  by  a  thin 
layer  of  yellow  elastic  fibres,  and  is  much  more  delicate  and  less  protected 
by  its  epidermis  than  the  buccal  mucous  membrane,  of  which  it  is  a  con- 
tinuation ;  it  also  communicates  with  that  of  the  oesophagus,  the  larynx,  the 
nasal  fossae,  and  the  Eustachian  tubes. 

Its  epithelium  is  stratified  throughout ;  but  it  is  thin  and  ciliated  in  the 
upper  part,  thicker  and  tesselated  on  the  inferior  moiety,  which  more 
particularly  belongs  to  the  digestive  apparatus. 

Everywhere  there  are  racemose  glands,  though  they  are  most  numerous 
towards  the  roof  of  the  pharynx.  There  are  also  some  follicidar  glands 
beneath  the  mucous  membrane,  in  the  neighbourhood  of  the  guttural  opening, 
the  nasal  cavities,  and  the  Eustachian  tubes. 

2.  Muscular  layer. — This  is  composed  of  seven  pairs  of  muscles,  indicated 
in  the  following  enumeration  :  the  palato-pharynr/eus,  pterygo-pharyngeus, 
hjo-pharyngeus,  thyro-pharyngeus,  crico-pharyngeus,  aryteno-pharyngeus,  stylo- 
pharyngeus. 

Palato-pharyngeus  (Pharyngo-staphylinus). — This  muscle,  which  has 
already  been  described  as  belonging  to  the  soft  palate,  is  prolonged  back- 
wards on  the  lateral  wall  of  the  pharynx,  where  its  fibres  are  mixed  with 
those  of  the  pterygo-pharyngeus,  and  go  to  be  attached  to  the  superior 
border  of  the  thyroid  cartilage  by  passing  beneath  the  hyo-pharyngeal 
and  thyro-pharyngeal  muscles.     It  therefore  also  belongs  to  the  pharynx. 

Pterygo-pharyngeus,  OR  Superior  Constrictor  (the  pcdato-pharyngeusoi 
Percivall). — This  muscle  is  thin,  wide,  flat,  and  triangular.  It  originates 
from  the  pterygoid  process,  whence  its  fibres  diverge,  some  posteriorly, 
others  inwardly.  The  former  mix  with  those  of  the  palato-pharyngeus, 
and  comport  themselves  like  that  muscle ;  and  the  latter  are  united,  on 
the  median  line,  with  the  analogous  fibres  of  the  opposite  muscle,  form- 
ing a  kind  of  zone  around  the  origin  of  the  Eustachian  tube.  This 
muscle  is  covered,  externally,  by  a  layer  of  yellow  elastic  tissue,  which  is 
attached  with  it  to  th.e  pterygoid  bone ;  afterwards  it  is  fixed  to  the  superior 
border  of  the  great  branch  of  the  os  hyoides,  and  is  even  prolonged  on  the 
external  surface  of  the  muscle  it  covers  to  the  thyroid  cartilage. 

The  elasticity  of  this  fibrous  covering  plays  a  certain  part  in  the  move- 
ments of  the  hyo-laryngeal  apparatus,  in  acting  as  a  passive  antagonist  of  its 
depressors. 

This  muscle  is,  and  can  only  be,  a  perfect  constrictor  of  the  pharynx, 
as  it  diminishes  the  diameter  of  that  cavity  in  every  direction  :  the  longi- 
tudinal diameter,  by  means  of  its  posterior  fibres,  which  draw  the  thyroid 
cartilage  forward ;  and  its  transverse  diameter,  by  the  circle  thrown  around 
the  orifice  of  the  Eustachian  tubes  (Figs.  149  :  176,  8). 

Hyo-pharyngeus,  or  First  Middle  Constrictor  ;  Thyro-pharyngeus, 
OK  Second  Middle  Constrictor  ;  and  Crico-pharyngeus,  or  Inferior 
Constrictor. — The  two  first  of  these  muscles  only  form  one  in  Man,  the 
middle  constrictor  of  the  pharynx.  They  are  three  muscular  bands  which 
terminate  above  the  pharynx,  on  a  median  fibrous  fold  sometimes  wide 
enough  to  look  like  an  aponeurosis.  The  first  band  arises  from  the  cornu  of 
the  OS  hyoides ;  the  second,  from  the  external  surface  of  the  thyroid  carti- 
lage ;  the  third,  from  the  superficial  face  of  the  cricoid  cartilage. 


THE  FHAR  I'.VA'. 


375 


These  are  universally  regardecl  as  constrictors. 

Sometimes  two  fasciculi  are  observed  in  the  crico-pharyngeus.  The 
supplementary  fasciculus  is  somewhat  thin,  and  arises  from  the  posterior 
border  of  the  bezil  of  the  cricoid  cartilage,  ascending  parallel  to  the  oeso- 
phagus to  terminate  with  the  principal  fasciculus. 

Aeyteno-pharyngeus. — By  this  name  has  been  described  a  small  fasci- 
culus, extremely  thin  in  Solipeds,  which  extends  from  the  posterior  border 
of  the  arytenoid  cartilage  to  the  origin  of  the  oesophagus.  To  expose  this 
muscle,  which  we  do  not  look  upon  as  constant,  it  is  necessary  to  turn  the 
oesophagus  forward  on  the  superior  surface  of  the  pharynx. 

Stylo-pharyngeus. — A  narrow  band  which  descends  from  the  great 
hyoideal  branch  to  the  side  of  the  pharynx,  where  it  is  confounded  with 
the  pterygo-pharyngeus.  It  elevates  the  pharynx  in  contracting,  and  it  is 
also  regarded  as  a  dilator ;  though  the  disposition  of  the  parietes  of  the 
pharynx,  and  the  feeble  volume  of  this  muscle,  scarcely  allows  it  to  play 
any  efficacious  part  in  the  dilatation  of  that  cavity.  It  may  only  produce 
a  very  slight  infundibulum  where  it  is  inserted.  The  real  dilating  agent 
of  the  pharyngeal  cavity  is  the  alimentary  bolus,  which  is  pushed  into  it  by 
the  action  of  the  tongue  (Fig.  149,  5). 

Fig.  176. 


MUSCLES  OP  THE  PHARYNGEAL  AND  HYOIDEAL  REGIONS. 
1,  Glenoid  cavity  of  temporal   bone ;   2,   Superior  extremity  of  styloid  bone ; 


3, 


Tensor  palati  with  its  pulley,  5  5  4,  Stylo-pharyngeus  ;  6,  Palato-pharyngeus  ;  7, 
Circumflexus  palati ;  8,  Pterygo-pharyngeus  ;  9,  Sublingual  gland ;  10,  Portion 
of  hyoid  bone  ;r  11,  Hyo-pharyngeus ;  12,  Thyro-pharyngeus ;  13,  Crico-pharyn- 
geus; 14,  Portion  of  stylo-pharyngeus  ;  15,  Hyo-thyroideus  ;"16,  Styloid  bone; 
17,  Crico-arytenoideus  lateralis ;  18,  (Esophagus ;  19,  Sterno-maxillaris  and 
hyoideus,  and  subscapulo  hyoideus  ;  20,  Trachea  ;  21,  Hard  palate  ;  22,  Tongue. 


It  is  not  rare  to  meet  a  second  stylo-pharyngeus  muscle  terminating  on 
the  same  point  as  the  first,  but  proceeding  from  the  inferior  extremity  of  the 
large  branch  of  the  os  hyoides,  instead  of  its  upper  part. 

Certain  anatomists  designate  it  the  inferior  kerato-pharyngeus,  and  con- 
sider it  as  a  constrictor  of  the  pharynx.    It  sometimes  exists  only  on  one  side. 

3.   Vessels  and  nerves. — The  blood  sent  to  the  pharynx  comes  from  the 


376  THE  DIGESTIVE  APPARATUS  IN  MAMSIALIA. 

pharyngeal  and  thyroideal  arteries.     Tlie  nerves  are  supplied  by  the  glosso- 
■jjJiaryngeus,  pneumogastric,  and  great  sympathetic. 

Functions. — The  pharynx  plays  a  passive  part  in  respiration,  by  serving 
as  an  intermediate  canal  between  the  nasal  passages  and  the  larynx. 

Its  principal  function,  however,  is  connected  with  the  digestive  pheno- 
mena, by  its  being  an  active  agent  in  the  first  stage  of  deglutition — a  complex 
and  rapid  movement,  which  is  executed  in  the  following  manner  :  The  bolus  of 
food,  propelled  by  the  tongue  into  the  pharyux,  is  seized  by  the  constrictor 
muscles,  which  come  into  action  successively  from  before  to  behind,  in  a 
peristaltic  and  involuntary  manner,  to  carry  the  mass  to  the  entrance  of 
the  oesophagus.  The  food  thus  passes  over  the  opening  of  the  larynx  during 
pliaryngeal  deglutition,  but  it  cannot  enter  it,  because  the  bolus  forces  back 
the  epiglottis  on  this  aperture,  which  it  almost  exactly  closes ;  because,  also, 
the  passage  of  the  food  prevents  pulmonary  inspiration,  which  might,  if 
allowed  to  take  place,  divert  it  from  its  natural  course,  and  throw  it  into 
the  nasal  air-passages  ;  the  application  of  the  walls  of  the  pharynx  to  the 
pellet  of  food  during  its  momentary  passage  over  the  larynx,  intercepts  all 
communication  between  the  external  air  and  the  lungs,  and  only  permits 
the  elevation  of  the  ribs  with  the  utmost  difficulty.  The  extreme  rapidity 
of  the  act  of  deglutition  is  another  reason  for  the  food  escaping  the  larynx. 

(Gray  concisely  remarks :  When  deglutition  is  about  to  be  performed, 
the  pharynx  is  drawn  upwards  and  dilated  in  different  directions  to  receive 
the  morsel  propelled  into  it  from  the  mouth.  The  stylo-pharyngei,  which 
are  much  further  removed  from  one  another  at  their  origin  than  at  their 
insertion,  draw  upwards  and  outwards  the  sides  of  this  cavity,  the  breadth 
of  the  pharynx,  in  the  antero-posterior  direction,  being  increased  by  the 
larynx  and  tongue  being  carried  forwards  in  their  ascent.  As  soon  as  the 
morsel  is  received  in  the  pharynx,  the  elevator  muscles  relax,  the  bag 
descends,  and  the  constrictors  contract  iipon  the  morsel  and  convey  H 
gradually  downwards  into  the  oesophagus.) 

The  deglutition  of  liquids  is  carried  on  in  a  similar  manner. 

It  is  curious  to  remark  that,  in  Solipeds,  the  food  does  not  come  into 
direct  contact  with  the  greater  portion  of  the  superior  wall  of  the  pharynx 
during  its  passage  through  that  cavity.  When  the  alimentary  mass  is 
carried  back  by  the  tongue,  it  raises  the  soft  palate  and  bears  its  posterior 
border  backwards  to  the  entrance  of  the  oesophagus.  The  extreme  develop- 
ment of  this  palatine  curtain,  therefore,  quite  prevents  this  surface  of  the 
pliarynx  from  being  directly  applied  to  the  food,  and  it  is  through  the  medium 
of  this  partition  that  the  constrictors  exercise  their  peristaltic  action  on  the 
morsel  of  aliment  until  it  reaches  the  oesophageal  infundibulum. 

DIFFERENTIAL   CHARACTERS   OF   THE   PHARYNX   IN   OTHER   THAN   SOLIPED   ANIMALS. 

The  pharynx  of  Ruminants  is  lono^  and  very  spacious.  The  hyo-,  thyro-,  and  crico- 
pharyngeal  muscles— the  first  and  second  of  the  two  middle  constrictors,  and  the  inferior 
constrictor — are  less  distinct  from  each  other  than  in  the  Horse ;  the  last-named  muscle 
is  very  small,  and  the  fibrous  raphe  on  which  the  constrictors  unite  is  little  developed. 
In  the  pharynx  of  the  Sheep  is  noticed  a  mucous  duplicaturo  that  descends  to  the  middle 
of  the  posterior  wall,  and  appears  to  be  a  continuation,  posteriorly  and  inferiorly,  of  the 
nasal  septum. 

In  the  Pi(f,  the  posterior  part  of  the  pharynx  is  narrow,  and  has  a  pouch  immediately 
above  tho  glottis,  between  the  thyro-  and  crico-pharyngeal  muscles. 

In  the  Dog,  the  infundibulum  is  very  spacious,  and  the  pharyngeal  mucous  membrane, 
nmch  finer  than  that  of  the  oesophagus,  is  distinguished  from  it  by  a  well-marked  line 
of  demarcation.  The  crico-pharyngeal  is  nut  very  distinct  from  the  thyro-pharyiigeal 
muscle  ;  so  that,  in  reality,  only  three  constrictors  can  be  dittinguished. 


THE  (ESOFHAGVS. 


377 


compauLjOK  of  the  pharynx  of  man  with  that  of  animals. 

In  consequence  of  the  smallness  of  the  soft  palate,  the  pharynx  of  Man  is  only  a 
kind  of  chiinnel  between  the  mouth  and  the  larynx  and  CBS.)phagu:>.  It  is  usually 
divided  into  three  portions  :  a  superior,  the  posterior  nares,  covered  by  ciliated  epithelium ; 
a  middle,  or  (juttund,  and  au  iuferior,  or  esophageal ;  tlie  two  latter  are  covered  with 
tesselated  epithelium. 

The  muscles  are  almost  the  same  as  in  the  Dog,  being  a  portion  of  the  palato-pharyn- 
geus,  the  superior,  middle,  and  inferior  constrictors,  and  a  stylo-pharyngcal  muscle. 

Below  the  sides  uf  the  pharynx,  and  between  the  pillars  of  the  soft  palate,  are  the 
amyrjdalx :  almond-shaped  organs,  whose  surface  s'.ows  the  openings  of  the  follicles  that, 
witli  the  vessels  and  a  little  connective  tissue,  compose  their  substance. 


THE   (ESOPHAGUS.      (Figs.  178,  179.) 

Preparation, — Place  the  subject  in  the  first  or  second  position ;  remove  the  subcu- 
taneous cervical  muscle  from   the  left  side;   take  away 
the   corresponding    anterior   limb,   and    proceed    to    tlie  Fig.  177. 

excision  of  the  ribs  of  this  side,  with  the  exception  of  the 
first.  Afterwards  dissect  the  vessels  and  nerves  in  the 
neighbourhood  of  the  oesophageal  canal,  taking  care  to 
preserve  their  relations  to  each  other. 

Form. — The  oesophagus  is  a  long,  cyHndrical, 
narrow,  membranous  canal,  easily  dilated  for  the 
gi-eater  part  of  its  extent,  and  destined  to  convey 
the  food  from  the  pharynx  to  the  stomach,  and  to 
complete  the  act  of  deglutition. 

Course. — This  canal  begins  at  the  pharynx, 
and  communicates  with  it  by  means  of  the  pos- 
terior opening  situated  above  the  glottis.  It 
afterwards  descends  behind  the  trachea  to  the 
middle  of  the  neck,  where  it  commences  to 
deviate  towards  the  left  side  of  that  tube,  and 
enters  the  thoracic  cavity  by  inclining  towards 
the  inner  aspect  of  the  first  left  rib.  It  soon 
after  regains  its  situation  above  the  trachea,  passes 
over  the  base  of  the  heart,  and  reaches  the  open- 
ing of  the  right  pillar  of  the  diaphi-agm,  in 
passing  between  the  two  layers  of  the  posterior 
mediastinum.  Traversing  tlais  opening,  it  pene- 
trates the  abdominal  cavity,  and  immediately 
afterwards  is  inserted  into  the  smaller  curvature 
of  the  stomach  by  an  orifice  designated  the  cardiac, 
which  will  be  studied  at  the  same  time  as  that 
viscus. 

Belations. — The  oesophagus  in  its  course  has 
the  following  nimierous  relations : 

At  its  origin,  it  is  comprised  between  the 
guttural  pouch  and  the  posterior  crico-arytenoid 
muscles. 


HniAN  PHARYNX  LAID  OPEN 
FROM    BEHIND. 

1,  Section  through  base  of 
skull ;  2,  2,  Walls  of  pha- 
rynx drawn  aside ;  3,  3, 
Posterior  nares,  separated 
by  the  vomer ;  4,  Extremity 
of  one  Eustachian  tube ;  5, 
Soft  palate;  6,  Posterior 
pillar  of  soft  palate  ;  7,  An- 
terior pillar ;  8,  Root  of  the 
tongue,  partly  concealed  by 
the  uvula ;  9,  Epiglottis 
overhanging  (10)  the  cordi- 
form  opening  of  the  larynx ; 

11,  Posterior  part  of  larynx ; 

12,  Opening  of  oesophagus, 
13 ;  14,  Trachea. 


In  the  cervical  region,  it  is  enveloped  in  a 
thick  layer  of  cellular  tissue,  which  unites  it  in  a  loose  manner  to  the 
sm-rounding  organs,  its  relations  with  these  varying  as  we  consider  them 
superiorly  or  inferiorly.  Superiorly,  and  in  the  median  plane,  it  occupies 
the  space  included  between  the  trachea  and  the  longus-colli,  being  bordered 
on  each  side  by  the  common  carotid  artery,  with  its  satellite  nerves — the 


378 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


trunk  common  to  the  great  sympatlietic  and  pneumogastric,  and  the  inferior 
laryngeal. 

Inferiorly,  it  is  related  to  the  trachea  internally;  and,  externally,  to 
the  inferior  scalenus  muscle,  and  the  vessels  and  nerves  of  the  left  cervical 
channel,  which  also  includes  the  jugular  vein.^ 

At  its  entrance  into  the  thoracic  cavity,  the  oesophagus,  still  deviating  to 
the  left,  and  lying  on  the  side  of  the  trachea,  responds,  externally,  to  the 
inferior  cervical  ganglion,  the  afferent  and  emergent  nervous  branches  of 
that  ganglion,  the  vertebral  arteries  and  veins,  and  the  superior  cervical  and 
dorso-muscular  vessels,  which  obliquely  cross  its  direction.      Beyond  this 

Fig.  178. 


TRANSVERSE   VERTICAL  SECTION   OF     HEAD   AND   NECK  IMMEDIATELY   IN   FRONT   OP   THE 
STYLOID   PROCESSES,    AND   BEHIND  THE  (ESOPHAGUS. 

1,  (Esophagus ;  2,  Inner  surfacer  of  trachea ;  3,  Common  carotid  artery ;  4,  Recur- 
rent nerve ;  5,  Thyroid  gland ;  6,  Exterior  of  pharynx ;  7,  Crico-pharyngeal 
muscle;  8,9,  10,  11,  Guttural  pouch  and  objects  in  its  interior;  12,  Stylo- 
pharyngeus  muscle;  13,  Sphenoid  bone;  14,  Jugular  ganglia;  15,  Internal 
carotid;  16,  17,  Pneumogastric  nerve;  18,  Parotid  gland;  19,  Great  hypoglossal 
nerve ;  20,  Jugular  vein ,  21,  Subscapulo-hyoideus ;  22,  Stylo-maxillaris. 

it  regains  its  position  between  the  trachea  and  the  longus  colli,  passes 
above  the  left  bronchus,  to  the  right  of  the  thoracic  aorta,  until  it  reaches 
between  the  layers  of  the  posterior  mediastinum,  which  bring  it  into  relation 
with  the  internal  face  of  the  lungs ;  these  are  channeled  for  its  reception, 
and  here  it  is  accompanied  by  the  oesophageal  artery,  and  the  oesophageal 
branches  of  the  pneumogastric  nerve. 

The  very  short  ]portion  lodged  in  the  abdominal  cavity  responds,  on  the 

'  It  is  not  rare  to  find  the  oesophagus  deviate  to  the  right  below  the  neck ;  in  this 
case  its  relations  will  be  inverted.  We  have  never  seen  this  canal  enter  the  thorax  in  the 
median  plane  of  the  body. 


THE  (ESOPHAGUS. 


379 


right,  to  a  fissure  in  the  superior  border  of  the  liver,  and  is  enveloped  by  the 
peritoneum. 

Interior. — Internally,  the  canal  whose  course  and  relations  we  have  just 
studied  jwesents  nothing  of  interest ;  and  it  only  requires  to  be  remarked, 
that  its  walls  are  always  shrunken  and  in  contact  when  food  is  not  passing 
between  them. 

Structure. — The  oesophagus  has  two  tunics :  a  mucous  and  a  muscular. 

The  mucous  membrane  is  continuous  with  that  of  the  pharynx  and  the 
stomach ;  it  is  white,  and  shows  numerous  longitudinal  folds  which  allow 
the  canal  to  dilate.  It  adheres  but  loosely  to  the  muscular  coat,  on  which 
it  can  glide  with  the  greatest  facility.  It  has  a  thick,  resisting,  stratified, 
tesselated  epithelium,  an  unstriped  muscular  layer,  and  some  racemose 
glands. 

Fig.  179. 


PECTORAL  CAVITY   AND   MEDIASTINUM,   SHOWING  THE   COURSE   OF   THE   TRACHEA 
AND   tESOPHAGUS. 


(A  third  or  mirldle  coat  is  sometimes  mentioned  by  anatomists ;  it  is 
composed  of  the  tissue  connecting  the  latter  tunic  with  the  one  to  be  next 
described.) 

The  muscular  coat  commences  at  the  posterior  part  of  the  pharynx  by 
the  aryteno-pharyngei  muscles,  and  by  two  small  superficial  bands  which 
are  detached  from  the  posterior  portion  of  the  crico-pharyngei  muscles. 
This  tunic  is  formed  of  superficial  longitudinal  fibres,  often  assembled  in 
fasciculi ;  and  of  a  deeper  series  of  spiral  or  circular  fibres,  which,  towards 
the  inferior  extremity  of  the  canal,  intercross  in  an  almost  inextricable 
manner.  This  muscular  layer  in  the  cervical,  and  for  a  great  part  of  the 
thoracic  portion  of  the  cesophagus,  has  the  red  colour  of  voluntary  muscles  ; 
but  it  becomes  white,  like  the  involuntary  fibres,  after  the  conduit  enters 
the  mediastinum,  and  acquires  considerable  thickness  and  marked  rigidity. 
It  is  to  be  noted  that  this  arrangement  of  the  muscular  tunic  is  especially 


380  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

evident  towards  the  insertion  of  the  cesophagus  into  the  stomach,  and  that 
the  muscular  tube  is  at  this  point  so  narrow,  that  it  is  almost  exactly  filled 
by  the  folds  of  mucous  membrane  it  contains.  For  this  reason  it  is  tbat 
we  may  inflate  a  stomach  by  the  pylorus,  without  applying  a  ligature  to 
the  oesophagus ;  the  aperture  of  the  canal  being  so  i^erfectly  closed  that  it 
does  not  allow  a  bubble  of  air  to  escape.  In  describing  the  interior  of  the 
stomach,  we  will  refer  to  the  consequences  resulting  from  this  interesting 
anatomical  fact. 

Vessels  and  nerves. — The  oesophagus  is  supplied  with  blood  by  the 
divisions  given  off"  by  the  common  carotid  artery,  as  well  as  the  bronchial 
and  oesophageal  arteries.  The  nerves  are  almost  exclusively  derived 
from  the  pneumogastric ;  the  motor  nerves  are  the  superior  oesophageal 
filaments,  branches  of  the  external  pharyngeal  and  laryngeal ;  the  sensitive 
filaments  are  derived  from  the  recurrent. 

Functions. — This  canal  conveys  nutriment  from  the  pharynx  to  the 
stomach  ;  it  has  no  other  uses. 

DIFFERENTIAL   CHARACTERS   OF   THE   (ESOPHAGTS   IN   OTHER   THAN   SOLIPED   ANIJIALS. 

In  all  the  other  domesticated  animals,  the  muscular  coat  is  red-coloured  throughout 
its  whole  extent,  and  everywhere  ofters  tlie  same  degree  of  thickness  and  the  same 
flaccidity,  The  canal  is  also  as  wide  towards  the  stomach  as  at  the  pharynx.  In 
Ruminants  and  the  Carnivora,  it  enters  the  stomach  as  a  funnel-shaped  (iufundi- 
buliform)  tube. 

The  dilatability  of  the  cesophagus  is  very  remaikable  in  these  animals :  Dogs  swallow- 
large  pieces  of  flesh;  and  Cows  and  Oxen  are  able  to  injtst  large  turnips,  or  sucii 
voluminous  foreign  bodies  as  shoes. 

(Ill  Ruminants  and  the  Carnivora  the  cesophagus  is,  proportionally,  wider  than  in  the 
Horse  and  Pig.) 

COMPARISON  OF   THE  CESOPHAGUS   OF   MAN   WITH   THAT   OF   ANIMALS. 

The  oesophagus  oi  Man  resembles  that  of  Carnivora ;  its  diameter  is  almost  uniform. 
It  also  inclines  to  the  left  below  the  neck,  but  in  tlie  thorax  is  in  the  median  line,  though 
it  again  deviates  to  the  left  as  it  joins  the  stomach.  As  the  thyroid  in  Man  is  very 
voluminous,  it  is  related  to  tlie  cesophagus  in  the  upper  part  of  the  neck.  Two  small 
accessory  fasciculi,  belonging  to  the  muscular  tunic  of  the  cesophagus,  have  been 
described  :  one  is  the  broncho-oesophageal  muscle,  which  is  detached  from  the  left  bronchus ; 
and  the  other  the  pleuro-oesophageal  muscle,  detached  from  the  left  layer  of  the  posterior 
mediastinum. 

Article  II, — The  Essential  Organs  of  Digestion. 

These  organs  being  all  contained  in  the  abdominal  cavity,  this  common 
receptacle  will  first  be  studied ;  afterwards  the  stomach,  intestines,  and  their 
annexed  organs — the  liver,  pancreas,  and  spleen — will  be  described, 

the  abdominal  cavity. 

In  mammalia,  the  interior  of  the  trunk  is  partitioned  by  the  diaphi"agm 
into  two  gTcat  cavities,  that  lodge  the  majority  of  the  organs  so  vaguely 
termed  the  viscera.  The  anterior,  the  smallest,  is  the  pectoral  or  thoracic 
cavity ;  the  posterior  is  named  the  abdomen,  or  abdominal  cavity.  The  latter, 
the  only  one  we  have  now  to  study,  is  a  vast  oval-shaped  reservoir,  elongated 
from  before  to  behind,  having  for  its  upper  wall  the  muscles  of  the  sub- 
lumbar  region,  inclosed  below  and  laterally  by  the  muscles  of  the  inferior 
abdominal  region;  bounded  in  front  by  the  diaphragm,  and  prolonged  behind 
between  the  bones  and  membranous  ligaments  of  the  pelvis. 

The  elements  composing  the  parietes  of  this  cavity  having  been  already 
described,  we  will  confine  oui'selves  to  au  examination  of  its  interior,  ia 


THE  ABDOMINAL  CAVITY.  381 

order  to  determine  the  various  regions  into  wliicli  it  is  possible  to  divide  it : 
a  matter  of  some  importance,  as  it  singularly  facilitates  the  tojiographioal 
study  of  the  contained  viscera ;  for  to  say  that  an  organ  is  situated  in 
the  abdomen,  is  a  very  vague  reference  to  its  precise  situation,  in  conse- 
quence of  the  great  extent  of  this  cavity.  It  is  necessary,  therefore,  to 
divide  the  abdomen  into  a  certain  number  of  peripheral  regions  which  corre- 
spond to  the  different  parts  of  its  wall,  with  a  view  to  define  the  situation 
of  the  organs  lodged  therein,  yet  without  complicating  anatomical  de- 
scription.    Six  princijial  regions  are  recognised  in  the  abdominal  cavity. 

A.  The  superior,  or  sublumbar  region,  corresponds  to  the  superior  wall  of 
the  abdomen :  that  is,  to  the  psoas  muscles  and  the  bodies  of  the  lumbar 
vertebraB.  It  extends  from  the  opening  between  the  two  pillars  of  the 
diaphragm  to  the  entrance  to  the  pelvis. 

B.  The  inferior  region,  limited,  laterally,  by  the  hypochondriacs  and 
the  flanks,  commences,  in  front,  at  the  xiphoid  cartilage,  and  is  prolonged 
to  the  pubis ;  it  comprises  all  that  jjurtion  of  the  abdomen  which  corre- 
sponds to  the  linea  alba  and  the  two  recti  muscles.  Its  great  extent 
necessitates  its  subdivision  into  five  secondary  regions :  The  suprasternal 
region,  named  the  epigastric  in  Man,  placed  above  the  xiphoid  cartilage  of  the 
sternum ;  the  umbilical  region,  situated  behind  the  preceding,  and  so  named 
in  consequence  of  its  including  that  jxart  of  the  wall  which  is  pierced  by  the 
umbilicus ;  the  prepubic  region — the  hypogastric  or  pubic  of  Man — occupies 
the  s^iace  in  front  of  the  anterior  border  of  the  pubis ;  the  two  inguinal 
regions,  diverticuli  of  the  abdominal  cavity,  located  in  the  inguinal  tracts, 
where  they  form  the  special  reservoirs  to  be  hereafter  described  as  the 
vaginal  sheaths  (or  canals). 

C.  The  lateral  regions  {right  and  left  lumbar  of  Man)  are  limited  :  in  front, 
by  the  costal  attachments  of  the  diaphragm  ;  behind,  by  the  entrance  to  the 
pelvic  cavity ;  above,  by  the  superior  border  of  the  small  oblique  muscle ; 
below,  by  the  interval  comprised  between  the  inferior  border  of  that  muscle 
and  the  external  border  of  the  great  rectus  muscle.  The  designation  of 
hypochondriac  is  given  to  the  subregion  which  corresponds  to  the  cartila- 
ginous circle  of  the  false  ribs.  The  flank  is  that  section  covered  by  the 
muscular  portion  of  the  small  oblique  muscle. 

D.  The  anterior,  or  diaphragmatic  region,  comprises  the  cavity  formed  by 
the  posterior  face  of  the  diaphragm.  Like  that  muscle,  it  is  divided  into 
two  regions,  a  central  and  peripheral. 

E.  The  posterior,  or  pelvic  region,  is  a  special  diverticulum  of  the  abdomen 
described  as  the  pelvic  cavity.  It  is  bounded,  above,  by  the  sacrum  ;  below, 
by  the  superior  face  of  the  pubes,  the  ischia,  and  the  internal  obturator 
muscle ;  on  the  sides,  by  the  constricted  portions  of  the  ossa  innomiuata 
and  the  saero-ischiatic  ligaments.  The  entrance  to  this  diverticulum  is 
situated  above  the  pubes,  and  is  of  an  oval  form.  Posteriorly,  it  is  narrower, 
and  is  traversed  by  the  rectum  and  the  genito-urinary  organs,  which  open 
externally. 

The  Peritoneum. — The  abdominal  cavity  is  covered,  internally,  by  a 
serous  membrane,  the  peritoneum,  which  will  now  be  briefly  described. 

Like  all  the  splanchnic  serous  membranes,  the  peritoneum  is  composed  oi 
a  parietal  and  a  visceral  layer,  which  together  form  a  closed  sac,  so  arranged 
that  the  organs  contained  in  the  abdomen  are  situated  external  to  this  sac. 
The  adjoining  theoretical  figure  (180),  representing  a  transverse  section  of  the 
abdominal  ca^'ity,  will  show  at  a  glance  this  arrangement.  Let  a  represent 
the  section  of  the  small  intestines  floating  at  liberty  in  the  interior  of  the 


382 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


Fiff.  180. 


THEORETICAL  ITIANSS'EH.SE  SECTION 
OF  THE  ABDOMINAL  CAVITY,  TO 
SHOW  THE  DISPOSITION  OF  THE 
PERITONEUM. 


cavity,  b  that  of  the  aorta,  at  the  level  of  the  great  mesenteric  artery  :  the 
peritoneal  membrane,  cc,  covers  the  walls  of  the  abdomen,  and  at  the  points 
DD  (not  inserted,  but  intended  to  be  placed  ivithin  the  cavity  below,  and  on 
each  side  of  b,  the  aorta)  is  folded  around  the  great  mesenteric  artery  in  such 

a  manner  as  to  form  two  layers,  ff,  which 
come  in  contact  by  their  adherent  face, 
reach  the  intestine,  and  then  separate  to 
enveloj)  it.  We  then  see  in  this  figure  the 
parietal  layer  of  the  peritoneum,  cc,  the 
visceral  layer,  GG,  and  the  two  layers,  ff, 
which  establish  the  continuity  of  the  parie- 
tal and  visceral  portions;  the  complete 
sac  formed  by  these  is  ai^i^arent,  and  it 
could  be  rendered  more  so  by  the  further 
separation  and  development  of  the  layers 
ff  ;  so  that  there  is  no  difficulty  in  under- 
standing how  the  small  intestine  may  be 
at  the  same  time  in  the  interior  of  the 
abdominal  cavity,  and  outside  the  sac 
formed  by  the  serous  membrane  which 
lines  that  cavity. 

This  arrangement  is  common  to  all  the 
organs  freely  suspended  in  the  abdomen. 
The  serous  folds  which  suspend  them,  in 
joining  their  peritoneal  layer  to  that  which 
covers  the  parietes  of  the  cavity,  will  be  studied  under  the  names  of 
ligaments,  mesenteries,  and  omenta.  Some  organs — the  kidneys,  for  example 
— have  no  proper  visceral  layer,  being  comjmsed  between  the  abdominal 
wall  and  the  external  face  of  the  parietal  peritoneum,  and  are  invested 
with  none  of  the  duplicatures  just  mentioned. 

We  will  briefly  study  the  duplicatures,  ligaments,  mesenteries,  and 
omenta  that  the  peritoneum  forms,  starting  from  the  mnbilicus  and  passing 
forwards  and  backwards  (Fig.  181). 

On  reaching  the  suprasternal  region,  the  peritoneum  forms  a  falciform 
duplicature,  extending  from  the  umbilicus  to  the  middle  lobe  of  the  liver, 
and  which  is  even  prolonged  between  that  lobe  and  the  posterior  face  of  the 
diaphragm  ;  at  the  free  border  of  this  fold  is  a  thickening  ^hich  is  regarded 
as  the  remains  of  the  obliterated  umbilical  vein.  In  becoming  doubled  over 
the  neighbouring  organs,  the  diaphragmatic  portion  constitutes :  1,  The 
ligaments  of  the  right  and  left  lobes  of  the  liver ;  2,  The  common  ligament 
of  that  gland,  which  surrounds  the  posterior  vena  cava :  3,  The  cardiac 
ligament  that  envelops  the  termination  of  the  oesophagus.  Behind  the 
liver  is  found  the  hepato  gastric  ligament,  which  fixes  the  stomach  in  the 
posterior  fissure  of  the  liver  and  is,  to  the  right  and  backwards,  attached  to 
the  duodenum  at  the  lower  face  of  the  right  kidney  ;  it  is  then  directed  from 
right  to  left,  and  becomes  continuous  with  the  parietal  peritoneum  of  the 
sublumbar  region  and  the  mesentery  proper. 

The  two  laminae  of  the  hepato-gastric  ligament  separate  at  the  lesser 
curvature  of  the  stomach  to  cover  that  viscus  ;  then  join  at  its  greater  cur- 
vature, and  pass  to  the  interior  of  the  abdominal  cavity.  This  fold  receives 
the  name  of  the  great  or  gastro-colic  omentum  ;  it  leaves  the  left  tuberosity 
of  the  ventriculus,  which  it  suspends  to  the  sublumbar  region  from  the 
whole  extent  of  the  great  curvature ;  to  the  right  it  goes  beyond  the  pylorus, 


THE  ABDOMINAL  CA  VITY. 


383 


to  be  continuecl  on  the  concave  curvature  of  the  dnodcnum  as  far  as  the 
caecum.  By  its  posterior  border,  the  great  omentum  is  spread  around  the 
termination  of  the  large  colon  and  the  origin  of  the  floating  colon,  where  it  is 
confounded  with  the  visceral  peritoneum  of  these  organs,  as  well  as  with  the 
parietal  peritoneum.  It  resiilts  from  this  arrangement  that  the  great  omentum 
forms  behind  the  stomach,  and  in  front  of  the  adherent  portion  of  the  large 
colon,  a  space  that  communicates  with  the  great  peritoneal  cavity  by  a  very 
narrow  opening,  the  foramen  of  Winsloio.  This  aperture  is  included  between 
the  vena  portfe,  posterior  vena  cava,  anterior  extremity  of  the  pancreas,  and 
the  lesser  ciu'vature  of  the  stomach.  To  the  left  of  the  latter  viscus,  on  the 
external  face  of  the  great  omentimi,  the  spleen  is  suspended  ;  consequently, 
that  portion  extending  from  the  spleen  to  the  veutriculus  is  named  the 
gastro-splenic  omentum. 

The  two  layers  composing  the  great  omentum  are  very  thin  for  the 
greater  part  of  their  extent,  and  include  the  blood-vessels  between  them. 
In  emaciated  animals  these  vessels  are  distinctly  seen,  owing  to  the  trans- 
parency of  the  membranes,  and  they  give  the  omentum  a  lace-work  appear- 
ance ;  but  in  fat  subjects  they  are  concealed  by  the  adipose  tissue  deposited 
aloug  their  course,  and  which  may  accumulate  in  considerable  quantity. 

In  the  sublumbar  region,  the  parietal  peritoneum  forms  several  folds  ; 
these  are  :  the  hepatico-renal  ligament,  extending  from  tire  right  lobe  of  the 
liver  to  the  anterior  border  of  the  right  kidney  ;  the  ligament  of  the  lohus 
Spigelii,  the  mesentery  proper,  the  colic  mesentery ;  lastly,  the  greatly  de- 
veloped laminae  surrounding  the  caecum  and  the  second  flexure  of  the  colon, 
which  constitute  the  meso-ca;ciim  and  mesa-colon. 


THEORETICAL   LONGITUDINAL   AND   MEDIAN   SECTION   OF   THE   ABDOMINAL   CAVITY, 
TO  SHOW   THE   REFLEXIONS  OF   THE   PERITONEUM. 

1,  Liver ;  2,  Stomach ;  3,  Small  intestine ;  4,  Origin  of  the  floating  colon ;  5, 
Rectum;  G,  Vagina  and  uterus;  7,  Bladder;  9,  Posterior  aorta;  10,  Diaphragm; 
11,  Posterior  vena  cava;  12,  Inferior  abdominal  wall. — Pp,  Pp,  Parietal  perito- 
neum ;  Pv,  Pv,  Visceral  peritoneum. — L,  Hepato-gastric  ligament ;  M,  Mesentery. 
— Ge,  Great  omentum. 


The  great  mesentery  is  detached  from  the  border  of  the  large  mesenteric 
artery,  and  projects  into  the  abdominal  cavity  to  reach  the  small  intestine 
at  its  lesser  curvatui'e,  and  enveloi)  that  viscus. 


384  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

Its  shape  is  that  of  an  irregular  triangle,  whose  summit  corresponds  to  the 
mesenteric  artery,  the  very  short  anterior  border  being  continuous  with  the 
duodenal  frtenum,  and  the  posterior  border,  the  longest,  with  the  meso-colon, 
its  convex  festooned  base  being  as  long  as  the  intestine  itself.  Between  the 
two  laminae  that  compose  it  are  the  blood-vessels  and  lymphatics,  as  well  as 
the  nerves,  of  the  small  intestine. 

The  colic  mesentery  is  constituted  like  the  great  mesentery.  Its  inferior 
border,  plane  or  plicated,  is  fixed  to  the  small  curvature  of  the  floating  colon 
and  the  commencement  of  the  rectum ;  its  ujoper  border  extends  from  the 
great  mesenteric  artery  as  far  as  the  entrance  to  the  jDclvic  cavity. 

Around  the  cross  of  the  cfecum,  from  the  origin  and  the  termina- 
tion of  the  great  colon,  the  peritoneum  is  reflected  to  cover  these  viscera ; 
a  layer  passes  from  the  anterior  border  of  the  caecum  on  to  the  ileum 
and  the  second  flexure  of  the  colon :  this  is  the  meso-ccmum  ;  another  layer, 
comprised  between  the  second  and  third  portion  of  the  colon,  and  whose 
shape  is  that  of  a  battledore,  is  named  the  meso-colon. 

If,  again,  the  peritoneum  is  taken  at  the  umbilical  region  and  followed 
backwards,  it  will  be  found  to  insinuate  itself  into  the  inguinal  canals,  cover 
the  organs  contained  in  the  pelvis,  and  become  reflected  at  the  bottom  of 
that  cavity,  to  be  continued  either  with  the  peritoneiim  of  the  sublumbar 
region,  or  with  that  on  the  abdominal  walls. 

This  serous  membrane  covers  the  anterior  cul  de  sac  of  the  bladder,  and 
at  this  point  has  three  ligaments.  The  middle  ligament,  falciform  in  shape, 
leaves  the  large  extremity  of  the  bladder,  is  attached  to  the  anterior  border 
of  the  pubis,  and  insensibly  disappears  on  the  inferior  abdominal  wall ;  on 
its  free  border  is  a  small  fibrous  cord,  which  is  supposed  to  be  the  remains 
of  the  urachus.  The  two  lateral  ligaments  are  more  developed,  and  extend 
from  the  entrance  to  the  pelvic  cavity  to  the  vesical  cul-de-sac ;  they  have  on 
their  free  border  the  obliterated  umbilical  arteries.  In  the  male,  the  peri- 
toneum is  prolonged  from  the  upper  face  of  the  bladder  to  the  enlargement  of 
the  deferent  ducts,  between  which  it  sends  a  transverse  fold  to  the  anterior 
extremity  of  the  vesiculae  seminales,  and  is  then  reflected  around  the 
rectum. 

In  the  female,  it  is  carried  from  the  bladder  to  the  terminal  portion 
of  the  vagina,  to  the  uterus,  and  to  the  cornua  of  that  organ,  where  it 
forms  three  folds  named  the  hroad  ligaments,  ligaments  of  the  ovary,  and  the 
round  ligament;  then  it  re  descends  on  the  upper  face  of  the  vagina,  and 
thence  envelops  the  rectum,  around  which  it  is  reflected  from  behind  forwards. 

According  to  this  arrangement,  we  see  that  the  termination  of  the 
digestive  canal,  and  the  parts  of  the  genito-urinary  organs  situated  altogether 
at  the  posterior  portion  of  the  pelvic  cavity,  are  placed  outside  the  peri- 
toneal serous  membrane. 

Structure. — Like  all  the  serous  membranes,  the  peritoneum  is  formed 
by  a  membrane  of  connective  tissue,  rich  in  elastic  fibres,  and  covered  on  its 
free  face  by  a  simple  tesselated  layer  of  epithelium  (the  cells  of  which  are  flat 
and  polygonal,  and  about  yoV^  of  an  inch  in  diameter).  Many  hlood-vessels 
are  found  on  the  adherent  surface,  while  lymphatics  are  abundant  in  the 
visceral  layer.  Its  nerves  come  from  the  diaphragmatic,  lumbar,  and  inter- 
costal branches,  and  the  great  sympathetic. 

DIFFERENTIAL   CHARACTERS   IN   THE   ABDOMINAL   CAVITY   OF   OTHER   THAN   SOLIPED 

ANIMALS. 

In  the  Car)iivr)7'a,  the  ahilominal  cavity  is  very  narrow ;  while  in  Rumiwnifs  it  is 
very  vast,  itd  capacity  being  in  direct  relation  to  the  volume  of  tlie  viscera  it  contains. 


THE  STOMACH.  385 

The  general  disposition  of  tlie  peritoneum  varies  but  little  in  the  different  species,  the 
only  notable  diversities  being  remarked  in  the  great  omentum.  In  the  Ox,  iiheep,  and 
Goat,  this  is  detached  from  the  middle  of  the  lower  face  of  the  rumen,  and  envelops  the 
right  sac  of  that  organ,  fixing  the  fourth  compartment  to  its  great  curvature,  and  then 
passing  upwards  to  become  continuous  with  the  mesentery.  In  the  Dog  and  Fig,  this 
fold  descends  in  front  of  the  intestinal  mass  until  near  the  pelvis  :  then  it  asctiuls  in 
gathering  ou  itself,  and  ultimately  spreads  over  the  colon  :  in  the  middle  portion  of  thtJ 
great  omentum  there  are,  consequently,  four  layers  placed  against  each  other. 

COMPARISON   OF   THE   ABDOMINAL   CAVITY   OP  MAN   WITH   THAT   OF   ANIMALS. 

The  abdominal  cavity  of  Man  is  elongated  vertically,  and  has  an  inferior  cavity 
occupying  the  entrance  to  the  pelvis.  There  is  nothing  particular  to  note  in  its  disposi- 
tion, tlie  difterences  observed  in  it  being  allied  to  the  external  shape  of  the  body.  The 
peritoneum  is  spread  over  its  parietes  nearly  in  the  same  manner  as  in  the  Carnivora ; 
the  great  omentum  is  constituted  by  four  layers,  and  covers  the  intestines  like  an  apron ; 
between  its  two  laminte  is  the  lesser  cavity  of  the  omentum,  virtually  in  the  adult. 

THE   STOMACH. 

The  stomach,  is  a  membranous  sac  comprised  between  the  oesophagus 
and  intestines,  and  in  which  are  commenced  the  essential  phenomena  of 
digestion. 

1.   The  Stomach  in  Solij^eds.     (Figs.  182,  183,  184,  185,  186.) 

Preparation. — In  order  to  study  the  relations  of  this  organ,  it  suiUces  to  open  the 
abdomen  and  remove  the  intestinal  mass  in  the  following  manner  : — Place  the  animal  iu 
the  first  po.sition,  and  very  slightly  inrllned  to  the  left  side  ;  make  an  incision  through 
the  inferior  abdominal  wall,  or,  still  better,  carry  it  away  entirely  by  a  circular  incision, 
taking  care  not  to  wound  any  part  of  the  intestine.  The  entire  viscera  should  then  be 
withdrawn  from  tlio  abdominal  cavity,  and  laid  on  the  table  which  suppoits  the  subject ; 
for  this  mass  cannot  be  allowed  to  fall  on  the  ground  without  risk  of  being  pulled  and 
torn,  either  in  the  intestine  itself,  or  those  parts  which  it  is  desired  to  preserve  intact  in 
the  abdomen.  Incise  the  floating  colon  where  it  joins  the  rectum,  and  the  duodenum 
where  it  passes  behind  the  great  mesenteric  artery  ;  the  base  of  the  caecum  should  now 
be  detached  from  the  sublumbar  surface  by  the  rupture  of  the  cellular  tissue  which 
connects  it  to  the  right  kidney  and  the  pancreas;  the  cellular  connection  between  the 
latter  gland  nud  the  terminal  extremity  of  the  fourth  portion  of  the  large  colon  should 
also  be  broken  ;  after  this,  it  is  only  necessary  to  divide  the  attachment  of  the  mesenteric 
bands  to  the  sublumbar  region,  with  the  vessels  contained  between  them.  The  intestinal 
mass  is  then  definitively  expelled  from  the  abdominal  cavity.  In  this  way  it  is  possible  to 
expose,  and  conveniently  prepare,  not  only  the  stomach,  but  also  the  spleen,  liver,  pancrea-, 
kidneys,  ureters,  etc.  Nothing  more  remains  than  to  make  known  the  procedure  to  be 
adopted  in  everting  the  stomach,  in  order  to  study  its  intemal  surface,  or  dissect  its  deep 
muscular  layer.  It  is  recommended,  first,  to  excise  the  stomach  with  at  least  three  inches 
of  the  oesopnagus,  and  eight  inches  of  the  duodenum,  end  cleanse  the  interior  of  the  organ. 
Tliis  may  be  done  in  several  ways,  but  the  following  is  the  simplest : — a  certain  quantity 
of  water  is  introduced  into  the  stomach  by  fixing  the  duodenum  to  a  water-tap,  tl.e 
right  hand  manipulating  the  organ  while  the  left  closes  the  duodenum  to  prevent  the 
escape  of  the  liquid.  The  alimentary  substances  contained  in  it  are  in  this  way  mixed 
with  the  water,  and  may  be  expelled  from  the  duodenum  by  pressing  the  stomach  ;  this 
operation  being  repeated  four  or  five  times,  thoroughly  cleanses  the  cavity  of  the  organ. 
To  evert  the  inner  surface,  it  is  only  necessary  to  introduce  by  the  duodenum  a  loop  <  f 
wire,  and  make  it  pass  through  the  oesophagus ;  a  strong  waxed  thread  is  fastened  in 
the  loop  and  firmly  fixed  around  the  esophagus,  when,  in  pulling  back  the  wire,  this 
extremity  is  drawn  towards  the  pylorus,  and  by  carofal  traction  the  latter  is  so  dilated 
as  to  allow  the  passage  of  the  cardiac  end,  and  complete  eversion  of  the  stomach.  Inflation 
will  then  give  it  its  normal  form  and  disposition  ;  with  thii  clifl'erence,  that  the  mucous 
membrane  is  external,  and  the  serous  tunic  internal. 

Lastly,  to  render  the  muscular  layers  of  the  stomach  more  evident,  it  is  advisable  to 
plunge  the  organ  into  boiling  water  for  some  minutes,  after  which  it  should  be  put  into 
cold  water.  If  it  is  desired  to  study  the  external  and  middle  layers,  the  stomach  should 
be  inflated,  and  its  serous  covering  removed  by  strips  with  forceps  and  the  fingers  ;  if  the 
deep  layer  is  to  be  examined,  the  mucous  membrane  must  be  removed  by  means  of  tlie 
forceps  and  scalpel  from  a  stomach  previously  everted. 


386 


THE  DIGESTIVE  APPAE ATI'S  IN  3IAMMALIA. 


Situation. — The  stomack,  also  designated  the  ventriculus,  is  situated  in  the 
diaphragmatic  region  of  the  abdomen,  where  it  affects  a  direction  transverse 
to  the  median  plane  of  the  body. 

Dimensions. — Its  average  capacity,  in  an  ordinary-sized  Horse,  is  from 
3  to  3i  gallons ;  but  it  varies  greatly  according  to  the  bulk  of  the  animal, 
its  breed,  and  the  nature  of  its  food.     Eelatively,  it  is  more  considerable 


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in  common-bred  Horses,  and  in  the  Ass  and  Mule.    When  empty,  its  average 
weight  is  between  3  and  4  pounds. 

Form. — Elongated  laterally,  curved  on  itself,  often  constricted  in 
its  middle,  and  slightly  depressed  from  before  to  behind,  this  reservoir 
presents,  externally :  1,  Two  faces — an  anterior  and  posterior,  smooth  and 
rounded ;  2,  A  great  or  convex  curvature,  forming  the  inferior  border  of  the 


THE  STOMACH. 


387 


organ,  and  giving  attachment,  throughout  its  extent,  to  the  great  omentum — 
a  membranous  fold  which  has  been  described  as  a  dependency  of  the  serous 
membrane ;  a  lesser  or  concave  curvature,  into  which  the  oesophagus  is 
inserted,  and  which  is  united,  to  the  right  of  that  canal,  to  the  liver,  by 
means  of  a  frasnum  known  as  the  hepato-gastric  ligament ;  4,  A  left  ex- 
tremitij,  dilated  in  the  form  of  a  large  conical  tuberosity,  and  constituting 
the  left  cul-de-sac  (or  fundus)  of  the  stomach  ;  5,  A  right  extremity,  narrower, 
curved  upwards,  and  continued  by  the  duodenum,  from  which  it  is  separated 
by  a  marked  constriction :  this  is  named  the  rigid  cul-de-sac  of  the 
stomach. 

Relations. — Studied  in  its  connections  with  the  neighbouring  organs,  the 
stomach  is  related  :  by  its  anterior  face,  with  the  diaphragm  and  liver ;  by 

Fiff.  183. 


STOMACH   OF   THE   HORSE. 

A,  Cardiac  extremitj'  of  the  oesophagus ;  B,  Pyloric  ring. 


its  posterior  face,  with  the  diaphragmatic  curvature  of  the  colon.  Its 
inferior  border,  margined  to  the  left  by  the  spleen,  which  is  suspended  from 
it  by  means  of  the  great  omentum,  is  separated  from  the  inferior  abdominal 
wall  by  the  large  anterior  curvatures  of  the  colon ;  its  distance  from  this 
wall  depends  upon  the  fulness  of  the  organ.  The  left  extremity,  suspended 
to  the  sublumbar  region  by  the  aid  of  a  very  short  serous  ligament,  a  portion 
of  the  great  omentum,  responds  to  the  base  of  the  spleen,  the  left  extremity 
of  the  pancreas  and,  less  directly,  to  the  anterior  border  of  the  left  kidney. 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


Fig.  184. 


Tho  right  extremity,  lower  than  the  left,  touches  the  right  lobe  of  the  liver 
aucl  the  above-meutioned  intestinal  curvatures. 

Interior. — When  a  stomach  is  opened  to  study  its  interior,  one  is  at  first 
struck  by  the  different  aspect  its  internal  membrane  presents,  according  as 
it  is  examined  to  the  right  or  left.  To  the  left,  it  has  all  the  characters  of 
the  oesophageal  mucous  membrane,  in  being  white,  harsh,  and  even  resisting ; 
it  is  covered  by  a  thick  layer  of  ejiithelium.  To  the  right,  it  is  thick, 
wrinkled,  spongy,  very  vascular  and  follicular,  has  a  reddish-brown  tint 
which  is  speckled  by  darker  patches,  loses  its  consistency,  and  is  deprived 
of  the  remarkable  epidermis  it  exhibits  on  the  left  side,  to  be  covered  by 
a  very  thin  epithelial  pellicle.  It  is  not  by  an  insensible,  but  a  sudden 
transition  that  the  mucous  membrane  of  the  stomach  is  thus  divided  into 

two  portions ;  and  their  separation  is  in- 
dicated by  a  salient,  more  or  less  sinuous, 
and  sharply-marked  ridge.  This  crest, 
then,  divides  the  stomach  into  two  com- 
partments :  a  division  already  indicated 
externally  by  the  circular  depression 
observed  in  the  majority  of  subjects. 
The  left  sac  or  compartment  is  considered 
as  a  dilatation  of  the  oesophagus.  The 
rigid  sac  constitutes  the  true  stomach  of 
Solii^eds ;  as  on  it  alone  devolves  the 
secretory  function  which  elaborates  the 
gastric  juice,  the  essential  agent  of  diges- 
tion in  this  organ. 

The  interior  of  the  stomach  (Fig. 
184)  offers  for  study  two  apertures :  the 
cardiac  and  pyloric.  The  cardiac,  or 
cesophageal  orifice,  is  in  the  lesser  curva- 
ture of  the  left  sac  of  the  stomach.  Its 
disposition  has  given  rise  to  numerous 
discussions,  as  in  it  has  generally  been  sought  the  reason  why  Solipeds 
vomit  with  such  extreme  difficulty.  At  one  time  there  has  been  des- 
cribed a  semilunar  or  spiroidal  valve,  which  is  opposed  to  the  retrograde 
movement  of  the  food ;  and  at  another  time  it  was  the  oblique  insertion  of 
the  oesophageal  canal,  resembling  that  of  the  ureters  into  the  bladder,  and 
which,  by  a  mechanism  analogous  to  these,  proved  an  obstacle  to  the  return 
of  aliment  into  the  oesophagus.  Both  suppositions  are  wrong.  When  we 
attentively  observe  the  manner  in  which  the  oesophagus  comports  itself  at 
its  termination,  it  will  be  noticed  that  it  is  inflected  downwards,  after  travers- 
ing the  right  pillar  of  the  diaphragm,  and  is  inserted  almost  perpendicularly 
into  the  lesser  curvature  of  the  stomach.  In  opening  into  this  viscus, 
the  oesophagus  does  not  widen  into  an  infundibiilum,  as  in  other  animals ; 
on  the  contrary,  its  calibre  is  here  narrower  than  elsewhere,  and  its  cardiac 
or  stomachal  orifice,  completely  obstructed  by  the  folds  of  mucous  membrane, 
only  occupies  an  infinitely  small  portion  of  the  internal  surface  of  the 
stomach. 

With  regard  to  the  jpylorus,  it  represents  a  large  aperture  formed  at  the 
bottom  of  the  right  sac,  and  furnished  with  a  thick  circular  ring;  this 
opening  can  be  completely  closed  through  the  action  of  the  powerful 
sphincter  sui'rounding  it. 

Structure. — The    parietes    of    the    stomach    are    composed   of  three 


INTERIOR   OF   THE   HORSES   STOMACH, 

A,  Left  sac ;  B,  Right  sac ;  C,  Duodenal 
dilatation. 


THE  STOMACH.  389 

membranes :  an  external,  or  serous ;  a  middle,  or  muscular  ;  and  an  internal, 
or  mucous. 

1.  Serous  memhraite.— This  membrane,  derived  from  the  peritoneum, 
adheres  closely  to  the  muscular  layer,  except  towards  the  lesser  curvature, 
where  it  is  constantly  covered  by  an  expansion  of  yellow  elastic  tissue, 
whose  use  appears  to  be  to  maintain  the  two  extremities  of  the  stomach 
near  each  other ;  for  when  this  is  destroyed  the  lesser  curvature  becomes 
considerably  elongated.  Along  the  whole  of  the  greater  curvature  is 
a  triangular  space  occupied  by  connective  tissue ;  this  space  disappears 
more  or  less  completely  as  the  organ  becomes  distended. 

It  has  three  folds,  which  are  detached  from  the  stomach  and  carried  on 
to  the  adjacent  parts,  and  which  are  formed  in  the  manner  indicated 
in  the  general  description  of  the  peritoneum.  Those  folds  constitute 
the  cardiac  ligament,  the  gastro-liepatic  ligament  or  omentum,  and  the  great 
omentum. 

The  cardiac  ligament  is  a  short,  serous  band  developed  around  the 
terminal  extremity  of  the  oesophagus,  and  strengthened  by  fibres  of  yellow 
fibrous  tissue.  It  attaches  the  stomach  to  the  posterior  face  of  the 
diaphragm,  and  is  continuous,  on  each  side,  with  the  two  folds  about  to  be 
described. 

The  g astro-hepatic  (or  lesser)  ligament  is  a  band  composed  of  two  layers, 
which  leave  the  lesser  curvature  of  the  stomach,  and  are  inserted  into  the 
posterior  fissure  of  the  liver.  It  is  prolonged  posteriorly,  and  to  the  right, 
along  the  duodenum,  where  it  constitutes  a  peculiar  serous  frasnum  which 
will  be  studied  with  the  small  intestine. 

The  great,  or  gastro-coUc  omentum,  is  detached  from  the  whole  extent 
of  the  great  curvature,  from  the  cardia  to  the  pylorus,  beyond  which  it 
extends  to  the  duodenum.  The  portion  surrounding  the  left  cul-de-sac  is 
excessively  short,  and  is  carried  to  the  sublumbar  wall  of  the  abdomen,  to 
which  the  stomach  is  fixed.  For  the  remainder  of  its  extent,  this  omentum 
is  greatly  developed,  and  hangs  freely  in  the  abdominal  cavity,  among  the 
intestinal  convolutions.  The  border  opjiosed  to  the  stomach  is  attached 
to  the  terminal  portion  of  the  large  colon,  and  to  the  origin  of  the  lesser 
colon.  For  further  details,  see  the  description  of  the  peritoneum.  These 
three  ligaments  fix  the  stomach  in  the  abdominal  cavity,  in  addition  to  the 
oesophagus  and  duodenum,  which  are  continuous  with  it. 

2.  Muscular  membrane. — This  tunic,  comprised  between  the  serous  and 
mucous  layers,  is  lined  internally  by  a  covering  of  condensed  connective 
tissue  which  adheres  intimately  to  it,  and  which  may  be  regarded  as  the 
fibrous  membrane  of  the  stomach.  Dissection  shows  this  muscular  tunic  to 
be  composed  of  three  superposed  planes. 

The  superficial  plane  envelops  all  the  right  sac,  and  the  majority  of  the 
fibres  composing  it  are  spread  in  loops  around  the  left  cul-de-sac,  their 
extremities  being  lost  on  the  surfaces  of  the  organ.  Some  of  them  even 
extend  over  the  great  curvature,  to  the  surface  of  the  right  sac ;  while 
others  are  evidently  continuous  with  the  superficial  fibres  of  the  oesophagus 
(Fig.  185,  A). 

The  middle  plane  (Fig.  185,  b)  is  formed  of  circular  fibres  spread 
over  the  whole  of  the  organ.  In  the  right  sac,  they  are  placed  immediately 
below  the  serous  membrane ;  in  the  left  sac,  they  j^ass  beneath  the  fibres 
of  the  superficial  plane,  and  finish  by  becoming  confounded  so  intimately 
with  these,  that  towards  the  tuberosity  formed  by  the  left  extremity  it  is 
impossible  to  distinguish  them.  By  their  aggregation  around  the  pylorus, 
28 


390 


THE  DIGESTIVE  AFFARATUS  IN  MAMMALIA. 


they   constitute   the   sphincter    (or    pyloric  valve)   which    envelops   that 
orifice. 

The  deep  plane  (Fig.  186,  a),  like  the  first,  is  specially  destined  for 
the  left  sac,  and  cannot  be  properly  studied  except  in  an  everted  stomach 
deprived  of  its  mucous  membrane.  Much  thicker  than  the  superficial  plane, 
it  yet,  in  its  general  arrangement,  much  resembles  it.  Thus,  its  fasciculi 
present  loops  which  embrace  the  left  cul-de-sac,  and  whose  extremities  are 
lost  on  the  faces  of  the  organ,  where  some  of  them  become  continuous  with 


Fig.  185. 


Fig.  186. 


MUSCULAR   FIBRES   OF   THE   STOMACH  ; 
EXTERNAL   AND   MIDDLE   LAYERS. 

A,  Fibres  of  the  external  layer  enveloping 
the  left  sac ;  B,  Fibres  of  the  middle  plane 
in  the  right  sac ;  c,  Fibres  of  the  ceso- 
phagus. 


DEEP  AND  MIDDLE  MUSCULAR  LAYERS  EX- 
POSED BY  REMOVING  THE  MUCOUS  MEM- 
BRANE   FROM    AN    EVERTED   STOMACH. 

A,  Deep  layer  of  fibres  enveloping  the  left  sac ; 
E,  Fibres  of  the  middle  plane  which  alone 
form  the  muscular  layer  of  the  right  sac ; 
C,  Fibres  of  the  oesophagus. 


fhe  circular  fibres.  The  loops  nearest  the  oesophagus  embrace  the  stomachal 
opening  of  that  canal  like  a  cravat.  It  is  to  be  remarked  that  the  fibres 
of  this  deep  layer  intersect  those  of  the  superficial  plane ;  the  former 
passing  from  the  left  to  the  right  sac,  in  inclining  downwards  towards 
the  great  curvature,  while  the  latter  are  directed  to  the  right  and  slightly 
upwards. 

From  this  arrangement  it  results,  as  a  glance  at  Figs.  185, 186  will  show : 

1,  That  the  right  sac  has  only  a  single  muscular  plane ;  2,  That,  on  the 

•  contrary,  the  left  sac  has  three,  all  of  which    concur   in   propelling   the 

aliment  that  has  accumulated  in  the  left  or  oesophageal  compartment  into 

the  right,  or  true  stomach. 

8.  Mucous  membrane. —  Independently  of  the  general  characters  notified 
in  the  interior  of  the  stomach,  it  has  to  be  remarked  that  the  gastric  mucous 
membrane  is  united  to  the  preceding  tunic  by  an  expansion  of  connective 
tissue ;  though  it  adheres  but  feebly  throughout  the  right  sac,  especially 
towards  the  greater  curvature,  where  it  is  thickest ;  and  that  it  has  no  ridges 
in  the  left  sac,  though  in  the  right  they  are  always  present,  even  when  the 
organ  is  inflated. 

On  the  surface  of  this  membrane  are  seen  microscopical  apertures  {alveoli), 
the  orifices  of  the  excretory  ducts  of  glands ;  these  are  rare  in  the  left  sacj 


THE  STOMACH. 


391 


but  extremely  numerous  in  the  right.  In  this  region  they  are  sojiaratcd 
from  each  other  by  minute  processes  resembling  papillae ;  but  the  latter  are 
only  met  in  the  vicinity  of  the  pylorus. 

The  gastric  mucous  membrane  is  composed  of  an  epithelial  layer  and  a 
corium,  in  which  is  distinguished  a  glandular  and  a  muscular  layer.  Tho 
epithelium  is  stratified  and  tesselated  in  the  left  compartment,  simple  and 
cylindrical  in  the  right  sac,  where  it  covers  the  little  mucous  processes 
that  separate  the  glandulae,  and  penetrates  more  or  less  deeply  into  the 
interior  of  these. 

In  the  left  side  there  are  found  some  glandular  organs  analogous  to 
those  of  the  oesophagus,  but  the  real  glandular  layer  belongs  only  to  the 


Fis.  187. 


Fig.  188. 


PEPTIC  GASTRIC  GLAND. 

a,  Common  trunk  ;  6,  6,  Its  chief  branches  ; 
c,  c,  Terminal  caeca,  with  spheroidal  gland- 
cells. 


PORTIONS  OF  ONK  OF  THE  0.T:CA  JIORE 
HIGHLY  MAGNIFIED,  AS  SEEN  LONGITUDI- 
NALLY (a),  and  in  TRANSVERSE  SEC- 
TION (b). 
a,  Basement  membrane;  6,  Large  glandular 
cell ;  c,  Small  epithelial  cells  surrounding 
the  cavity 


right  side.  There  are  found  multitudes  of  parallel  tubular  glands,  united 
by  a  small  quantity  of  delicate  connective  tissue  which  is  very  rich  in  nuclei. 
They  secrete  the  gastric  fluid,  or  furnish  the  mucus  that  covers  the  surface 
of  the  epithelium  ;  they  are  consequently  distinguished  as  pepsine  (or  peptic), 
and  mucous  glands,  the  former  being  much  more  numerous  than  the  latter. 

They  are  composed  of  a  simple  straight  tube  at  their  origin  (excretory 
ductj,    which   frequently  divides   into   two    or   more    flexunus   tubes   that 


892 


THE  DIGESTIVE  APPARATUS  IN  MAMJSIALIA. 


Fig.  189. 


terminate  in  culs-de-sac  (or  glandular  cceca).  The  epithelium  is  not  tho 
same  in  the  two  kinds  of  glands  :  the  mucous  glands  (Fig.  189,  a,  h)  are  lined 
with  cylinder-epithelium  throughout  their  extent ; 
the  peptic  glands  (Figs.  187,188)  are  lined  with 
cylinder-epithelium  at  their  origin  (Fig.  187,  a), 
but  the  secretory  tubes  contain  round  peptic  cells. 
(Each  caeca,  when  highly  magnified,  is  found  to 
consist  of  a  delicate  basement  membrane  (Fig. 
188,  a)  inflected  over  a  series  of  nearly  globular 
cells  (h),  which  occupy  almost  the  whole  cavity 
of  the  tube,  and  contain  a  finely-gi-anular  matter ; 
the  narrow  passage  left  vacant  in  the  centre  is, 
however,  still  surrounded  by  a  layer  of  epithelial 
cells  (c),  whose  small  size  is  in  striking  contrast 
to  the  large  dimensions  of  the  gland  cells.) 

The  muscular  layer  (of  the  mucous  membrane) 
is  immediately  beneath  the  glandular  structure, 
and  contains  two  planes  of  intersecting  fibres. 
Lastly,  the  connective  layer  of  the  corium  is  thick 
and  loose,  sustains  the  vessels  (and  nerves),  and 
unites  the  mucous  to  the  muscular  tunic  of  the 
stomach. 

4.  Vessels  and  nerves. — The  stomach  receives  its 
blood  by  the  two  branches  of  the  gastric  artery,  the 
splenic  and  its  terminal  branch — the  left  epiploic 
artery,  and  by  the  pyloric  and  right  epiploic  arteries. 
The  principal  arterial  ramifications  extend  be- 
„     ,  tween  the    mucous   and   muscular   layers,  where 

MUCOUS  GASTRIC  GLAND  WITH    ^^  .  -i,  -n  ^-ix-  \.xi 

CYLINDER  EPITHELIUM.       ^'^^J   lumish   two  Capillary   reticulations   to   the 
a,  Wide  trunk ,  b,  b,  Its  cscal  glandular  layer :  a  deep  network  that  surrounds 
appendage.  the  secretory  tubes,  and  a  superficial  placed  be- 

tween the  alveoli.     The  blood  is  carried  from  the 
organ  to  the  vena  portae  by  the  satellite  venous  branches.     The  lymphatics 

Fig.  190. 


APPEARANCE   OP   THE   PROPER  GASTRIC   MEMBRANE   OF   THE  STOMACH   IN   AN 
INJECTED    PREPARATION  (HUMAN). 

A,  From  the  conrex  surface  of  the  folds  or  ruga; ;  B,  From  the  neighbourhood  of 
the  pylorus,  where  the  orifices  of  the  gastric  follicles  occupy  the  interspaces  of 
the  deepest  portions  of  the  vascular  network. 

form  a  subserous  and  two  deep  networks  at  the  base  of  the  glandular 
layer  and  in  the  fibrous  membrane.  They  enter  small  ganglia  (or  glands) 
situated  along  the  curvatures,  and  from  these  to  Pecquet's  reservoir.     The 


TEE  STOMACH.  393 

nerves  are  derived  from  the  pneumogastrics  and  solar  plexus,  and  in  accom- 
panying the  vessels  show  microscopic  ganglia  in  their  course ;  their  mode 
of  termination  is  not  known. 

Functions. — In  the  stomach  is  begun  those  transformations  by  which 
alimentary  matters  are  rendered  capable  of  being  assimilated.  There  the 
food  comes  into  contact  with  the  gastric  fluid,  by  whose  action  its  principal 
elements,  and  particularly  the  albuminoid  substances,  become  soluble  and 
absorbable,  after  undergoing  some  isomeric  changes. 

DIFFERENTIAL   CHARACTERS   IN   THE   STOMACH   OF   OTHER   THAN   SOLIPED   ANIMALS. 

The  stomacli  is  an  organ  that  exhibits  great  differences  in  the  various  domesticated 
animals.  In  the  study  of  these  differences,  we  will  proceed  from  the  simple  to  the 
complex. 

1.  TJie  Stomach  of  the  Pig. 

The  Pig's  stomach  is  simple,  like  that  of  the  Horse,  but  it  is  less  curved  on  itself,  and  the 
cardia  is  nearer  the  left  extremity  ;  the  latter  has  also  a  small  conical  dilatation,  which 
has  been  compared  to  a  cowl  curved  backwards.  The  ojsophagus  opens  into  the  stomach 
by  a  wide  infundibulum,  and  the  mucous  membrane  of  that  conduit  is  prolonged  over 
the  gastric  surface  in  a  radius  of  from  two  to  three  inches  around  the  cardia.  Here 
again  we  find  a  "trace  of  the  division  into  two  sacs,"  common  to  Solipeds. 

The  capacity  of  the  Pig's  stomach  averages  from  one  and  a  half  to  two  gallons. 
(The  muscular  tunic  is  thicker  in  the  right  than  the  left  extremity ;  near  the  ceso- 
phagus  the  serous  tunic  shows  some  transverse  folds.) 

2.  The  Stomach  of  Carnivora,     (Fig.  191.) 

In  the  Dog  and  Cat  the  ventriculus  is  but  little  curved,  and  is  pear-shaped,  the 
small   extremity   corresponding    to    the 

pylorus.      The  cardia  is  dilated   like   a  Fig-  191' 

funnel,  and  is  nearer  the  left  extremity 
of  the  organ  than  in  otlier  animals.  The 
oesophageal  mucous  membrane  is  not  con- 
tinued beyond  the  margin  of  that  orifice. 
The  simple  stomach  of  Carnivora  forms 
only  a  single  sac,  whose  internal  mucous 
membrane  presents,  throughout  its  whole 
extent,  the  same  organisation  as  the 
membrane  lining  the  right  sac  of  Soli- 
peds. This  membrane  is  remarkable  for 
the  regular  and  undulated  folds  it  forms 
when  tlie  stomach  is  empty.  Nothing 
is  more  variable  than  the  capacity  of  the 
Dog's  stomach,  because  of  the  great  dif- 
ferences in  the  size  of  this  animal,  accord- 
ing to  breed.  M.  Colin  has  found  the 
minimum  to  be  IJ  pints,  and  the  maxi- 
mum If  gallons ;  he  calculates  the  aver- 
age to  be  about  2 J  quarts.  In  the  Cat, 
the  average  is  from  2  to  2|  gills. 

3.  The  Stomach  of  Ruminants. 

These  animals  are  distinguised  from 
the  others  by  the  faculty  they  possess 
of  swallowing  their  food  after  imperfect 
comminution,  and  causing  it  to  return 
again  into  the  mouth  to  submit  it  to  a 
second  mastication,  previous  to  final  de- 
glutition. The  gastric  apparatus  is  ad-  stomach  of  the  dog. 
mirably  arranged  to  effect  this  pliysio-  A,  (Esophagus ;  B,  Pylorus, 
logical  finality,  and  is  remarkable  for  its 

enormous  development,  as  well  as  its  division  into  four  separate  pouches,  which  are 
regarded  as  so  many  stomachs. 


394 


TEE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


These  cavities  represent  a  considerable  mass  that  fills  the  greater  part  of  the 
abdomiiifil  cavity,  and  the  medium  capacity  of  which  is  not  less  than  fifty-five  gallons! 
One  of  them,  the  rumen,  into  which  the  oesophagus  is  inserted,  constitutes  nine-tenths 
of  the  total  mnss.  The  other  three,  the  reticulum,  omasum,  uud  abomasum,  form  a  short 
chain,  continuous  with  the  left  and  anterior  portion  of  the  rumen.  The  abomasum  alone 
should  be  considered  as  a  true  stomach,  analogous  to  that  of  the  Dog,  or  the  right  sac  of 
the  ventriculum  of  Solipeds.  The  other  three  compartments  only  represent,  like  the 
left  sac  in  the  latter  animals,  oesophageal  dilatations. 

The  description  about  to  be  given  of  each  of  these  divisions  more  particularly  applies 
to  the  Ox  ;  care  will  be  taken,  in  the  proper  place,  to  note  the  special  peculiarities  in  the 
stomach  of  the  Sheep  and  Goat. 

KcMEN  (Fig.  192). — This  reservoir,  vulgarly  designated  the  paunch,  alone  occupies 
three-fourths  of  the  abdominal  cavity,  in  which  it  alfects  a  direction  inclined  from  above 
to  below,  and  from  left  to  right. 

Fig.  19. • 


STOMACH  OF  THE  OX,  SEEN  OX  ITS  RIGHT  UPPER  FACE,  THE  ABOMASUM  BEING  DEPRESSED. 

A,  Rumen,  left  hemisphere ;  B,  Rumen,  right  hemisphere ;  c,  Termination  of  the 
oesophagus  ;  D,  Reticulum  ;  E,  Omasum  ;  F,  Abomasum. 

External  conformation. — Elongated  from  before  to  behind,  and  depressed  from  above 
to  below,  it  offers  for  study :  1.  An  inferior  and  a  superior  face,  nearly  plane,  smooth, 
and  divided  into  two  lateral  regions  by  traces  of  fissures,  which  are  only  sensible  at  the 
extremities  of  the  organ ;  2,  A  left  and  right  border,  smooth,  thick,  and  rounded  ; 
3,  A  posterior  extrennty,  divideol  by  a  deep  notch  into  two  lobes,  described  by  Chabert 
by  the  name  of  conical  cysts  ;  4,  An  anterior  extremity,  offering  an  analogous 
arrangement,  and  concealed,  at  first  sight,  by  the  stomachs  (or  compartments)  superadded 
to  the  rumen ;  the  notch  on  the  right  of  this  extremity  divides  it  into  two  unequal 
pouches,  which  will  be  referred  to  presently. 

It  is  to  be  remarked  that  theic  two  notches,  which  are  prolonged  on  the  surface  by 
furrows  that  separate  these  into  two  lateral  regions,  divide  the  rumen  into  two  sacs,  a 
right  anol  left ;  this  olivision  we  will  find  more  manifest  in  the  interior  of  theviscus.  The 
right  sac,  the  shortest,  is  in  great  part  enveloped  by  the  serous  covering  which 
constitutes  the  i^reat  omentum.  The  left  sac  surpasses  the  other  by  its  two  extremities, 
except  in  the  Sheep  and  Goat,  in  which  the  riiiht  conical  cyst  is  longer  than  the 
1  ft.     The  anterior  extremity  of  this  left  sac  is  thrown  backwards  on  the  corresponding 


THE  STOMACH. 


395 


lobe  of  the  right  sac ;  above,  it  receives  the  insertion  of  the  oesophagus,  and  is  continuous^ 
in  front,  with  the  reticulum. 

Relations. — The  external  form  of  the  rumen  being  rletermined,  fhe  study  of  its 
relations  becomes  easy.  By  its  superior  surface,  it  is  in  contact  with  the  intestinal 
mass  ;  its  opposite  face  rests  on  the  inferior  abdominal  wall.  Its  left  border,  supporting 
the  spleen,  touches  the  most  elevated  part  of  the  flank  and  the  sublumbar  region,  to 
which  it  adheres  by  cellular  tissue,  as  well  as  the  vicinity  of  the  cceliac  trunk  and  tlie  great 
mesenteric  artery;  the  right  bonier,  margined  by  the  abomasum,  responds  to  the  most 
declivitous  portion  of  the  right  hypochondriac  and  flunk,  as  well  as  to  the  intestinal 
circumvolutions.  The  anterior  extremity,  bounded  by  the  reticulum  and  omasum, 
advances  close  to  the  diaphragm ;  the  posterior  occupies  the  entrance  to  the  pelvic 
cavity,  where  it  is  more  or  less  in  contact  with  the  genito-urinary  oigans  lodged  there. 
In  the  pregnant  female,  the  uterus  is  prolonged  forwards  on  the  upper  face  of  the  viscus 
just  described. 

Interior  (Fig.  193). — In  the  interior  of  the  rumen  are  found  incomplete  septa,  which 
repeat  the  division  into  two  sacs  already  so  marked  externally.     These  septa  are  two  in 


Fis.  193. 


INTERIOR   OF   THK   STOMACH   IN   EITMINANTS ;   THE   UPPER   PLANE   OF   THE   RtTMEN 
AND   RETICULUM,    WITH   THE    OESOPHAGEAL    FURROW. 

A,  Left  sac  of  the  rumen ;  B,  Anterior  extremity  of  that  sac  turned  back  on  the 
right  sac ;  C,  Its  posterior  extremity,  or  left  conical  cyst ;  G,  Section  of  the 
anterior  pillar  of  the  rumen  ;  g,  g,  Its  two  superior  branches ;  H,  Posterior  pillar 
of  the  same ;  h,  h,  h,  Its  three  inferior  branches ;  i,  Cells  of  the  reticulum ;  j, 
(Esophageal  furrow ;  K,  ffisophagus ;  L,  Abomasum. 


number,  and  represent  large  muscular  pillars,  which  correspond  inferiorly  to  the 
notches  described  at  the  extremities  of  the  organ.  The  anterior  pillar  (Fig.  193,  g) 
sends  to  the  inferior  wall  of  the  rumen  a  strong  prolongation,  directed  backwards,  and 
to  the  left ;  it  is  continued  on  the  superior  wall  by  two  branches,  which  separate  at  an 
acute  angle.  The  poderior  pillar  (Fig.  193,  H),  more  voluminous  than  the  preceding, 
has  three  branches  at  each  of  its  extremities — a  middle  and  two  lateral.  The  middle 
branches  are  carried  forwards  on  the  limit  of  the  two  sacs,  which  they  separate  from  one 
another ;  that  from  above  meets  the  corresponding  branch  from  the  anterior  pillar     The 


396  THE  DIGESTIVE  APPARATUS  IN  3IAMMALIA. 

lateral  branches  diverge  to  the  right  and  left  in  describing  a  curve,  and  in  circumscrib- 
ing the  entrance  to  the  conical  cysts,  which  they  transform  into  two  compartments 
distinct  from  the  middle  portion  of  the  sacs  of  the  rumen;  the  inferior  go  to  meet  the 
superior  branches,  but  do  not  altogether  join  them. 

The  internal  surface  of  the  rumen  is  covered  by  a  multitude  of  papillary  prolongations, 
dependencies  of  the  mucous  membrane.  To  the  right,  and  in  the  cids-de-sac,  thcae 
papillae  are  remarkable  for  their  number,  their  enormous  development,  and  their  general 
foliated  shape.  On  the  left  side  they  are  more  rare,  particularly  on  the  superior  wall, 
and  only  form  very  small  mammiform  tubercles;  they  are  absent  on  the  muscular 
columns.  This  papillary  arrangement  is  still  more  developed  in  certain  wild  Ruminants, 
and  it  is  scarcely  possible  to  give  an  idea  of  their  richness  in  the  stomach  of  the 
Gazelle. 

The  interior  of  the  rumen  offers  for  study  two  openings,  situated  at  the  anterior 
extremity  of  the  left  sac :  one  is  the  oesophageal  orifice,  pierced  in  the  superior  wall, 
dilated  into  an  infundibulum,  and  prolonged  into  the  small  curvature  of  the  reticulum 
by  a  particular  furrow  (or  channel),  which  will  be  described  after  the  latter  compart- 
ment ;  the  other,  placed  below,  and  opposite  the  preceding,  traverses  the  bottom  of 
the  cul-de-sac  from  before  to  behind,  and  forms  the  C(jmmunication  between  the  paunch 
and  reticulum :  it  is  a  very  large  opening,  circuinscribid  below  and  on  the  sides  by  a 
septum  or  semilunar  valve,  resulting  from  the  jimction  of  the  parietes  of  the  rumen  with 
those  of  the  reticulum. 

Structure. — Like  all  the  hollow  organs  in  the  abdomen,  the  rumen  has  three  tunics : 
a  serous,  a  Ttiuscular,  and  a  mucous. 

The  serous  envelops  the  organ  throughout,  except  above,  in  front,  and  to  the  left, 
the  point  which  touches  the  sublumbar  region,  and  the  pillars  of  the  diaphragm,  as  well 
as  the  bottom  of  the  notches  which  separate  the  culs-de-sac  from  the  extremities.  This 
membrane  gives  origin,  like  that  of  the  stomach  of  the  Horse,  to  a  vast  duplicature — 
the  great  omentum.  The  arrangement  of  this,  which  is  somewhat  difficult  to  observe 
in  the  Ox,  in  consequence  of  the  enormous  weight  of  the  gastric  mass,  is  readily  seen 
in  the  smaller  Ruminants.  It  begins  at  the  middle  of  the  faces  of  the  paunch  and  the 
tissure  intermediate  to  the  two  conical  cysts,  forming  a  wide  envelope  that  contains 
the  right  sac  and  the  abomasum;  it  becomes  attached  in  passing  over  the  great 
curvature  of  the  last-named  cavity,  and  is  confounded,  sujjeriorly  aud  posteriorly,  with 
the  great  mesentery. 

The  muscular  coat  is  very  thick,  and  forms  the  internal  columns  of  the  viscus.  Its 
fibres  are  disposed  in  several  layers,  whose  arrangement  is  simple,  and  offers  nothing 
really  interesting  to  study,  except  in  the  points  where  the  serous  tunic  passes  from  one 
cul-desac  to  another,  or  from  the  rumen  to  the  reticulum ;  there  it  is  often  accompanied 
by  thin  and  wide  muscular  fasciculi  which,  like  the  latter  membrane,  stretch  over  the 
intermediate  fissures,  and  thus  become  real  unitive  or  common  fibres. 

The  muscular  fibres  of  the  rumen  present  an  unmistakable  transverse  striation — a 
very  rare  physical  characteristic  in  the  muscular  tissue  of  organic  life. 

The  mucous  membrane  offers  some  peculiarities,  which  deserve  a  few  words.  The 
corium  is  very  thick,  and  probably  contains  some  glands,  but  they  must  be  extremely 
few.  The  free  face  of  the  membrane  is  excessively  uneven,  in  consequence  of  the 
pajjillary  apparatus  mentioned  above. 

The  papillai  of  the  rumen  are  foliaceous,  conical,  or  fungiform.  Those  of  the  first 
description  are  much  more  numerous  than  the  others ;  they  have  the  shape  of  an  oval, 
elongated  leaf,  their  summit  is  wide  and  rounded,  and  the  base  narrow  and  apparently 
implanted  in  the  corium.  On  one  face  is  a  little  rib  that  springs  from  the  base  and 
disappears  on  the  widened  portion,  resembling  the  principal  vein  or  nervule  of  a  leaf. 
On  the  other  face,  opposite  the  vein,  is  a  faint  longitudinal  groove. 

These  papillae  are  constituted  by  a  layer  of  nucleated  connective  tissue,  covered  by 
epithelium ;  the  former,  in  the  principal  papillae,  has  on  its  faces  and  extremities  minute 
prolongations,  resembling  on  a  small  scale  the  secondary  papillae  described  as  existing 
on  the  lingual  mucous  membrane.  In  the  centre  of  the  papillae  are  one  or  two  main 
arteries,  derived  from  the  network  of  the  corium.  These  pass,  in  a  slightly  flexuous 
manner,  to  the  summit,  and  break  up  into  several  branohlets,  succeeded  by  veins,  that 
descend  along  the  surface  of  the  papilla  into  each  of  its  secondary  prolongations. 

The  conical  and  fun^riform  papillaj  are  few  in  the  left  sac,  and  resemble  the  papillsQ 
of  the  same  name  described  on  the  tongue. 

The  epithelium  of  the  mucous  membrane  of  the  rumen  is  remarkable  for  its  strength 
and  cohesiveness.  It  belongs  to  the  category  of  stratified  tesselated  epithelium,  and 
forms  a  sheath  to  each  papilla,  covering  the  corium  in  the  interpapillary  spaces. 

There  are  frequently  found,  in  opening  the  rumen  of  animals  just  killed,  large 


TEE  STOMACH.  397 

exfoliated  patches  on  the  surface  of  this  layer.  This  is  a  sufficient  indication  of  the 
activity  of  the  secretion  of  the  epithelium,  and  the  rapidity  of  its  renovation. 

Reticclvm  (JIONEYCOMis)  (Figs.  Uf2,  193). — JSitiKition—Form — Iielations. — This,  the 
smallest  compartment,  is  elougateJ  from  one  side  to  the  other,  slightly  curved  on  itself, 
and  placed  transversely  betwei  u  the  posterior  face  of  the  diaphragm,  in  one  direction, 
and  the  anterior  extremity  of  the  left  sac  of  the  rumen  in  the  other ;  the  latter  onlv 
appearing,  externally,  to  be  a  prolongation,  or  a  diverticulum  of  the  rumen. 

It  has  two  faces,  ttco  curvatures,  and  two  extremities.  The  anterior  face  adheres  to 
the  phrenic  centre  of  the  diaphragm  by  cellular  tissue.  The  posterior  face  lies  against 
the  anterior  extremity  of  the  rumen.  The  great  inferior  or  convex  curvature  occupies 
the  suprasternal  region.  The  lesser,  superior,  or  concave  curvature  partly  responds  to 
the  lesser  curvature  of  the  omasum.  The  left  extremity  is  only  separated  from  the  rumen 
by  a  fissure,  which  lodges  the  inferior  artery  of  the  reticulum.  The  right  extremity  forms 
a  globular  cul-de-sac,  in  relation  with  the  base  of  the  abomasum. 

Interior  (Fig.  193). — The  internal  surface  of  the  reticulum  is  divided  by  ridges  of 
the  mucous  membrane  into  polyhedral  cells,  which,  in  their  regular  arrangement,  look 
like  a  honeycomb;  they  are  widest  and  deepest  in  the  cul-de-sac.  and  become  gradually 
smaller  in  approaching  the  superior  curvature.  The  interior  of  these  cells  is  divided 
into  smaller  spaces,  included  one  within  the  other,  by  secondary  and  successively-dtcreas- 
hig  septa.  The  principal  septa  ofler  on  their  free  border  a  series  of  conical  prolonga- 
tions, with  a  rough  hard  summit;  while  their  faces  are  studded  with  minute,  blunt,  or 
pointed  papillffi.  The  secondary  septa  also  show  similar  prolongations;  and  those  on 
their  free  margin  are  even  more  developed  than  on  the  chief  septa.  Lastly,  from  the 
bottom  of  the  cells  spring  up  a  crowd  of  long,  conical,  and  very  pointed  papillte,  resem- 
bling stalagmites  in  the:r  arrangement. 

It  may  be  noted  that  the  foreign  bodies  so  frequently  swallowed  by  Eimiinants,  are 
usually  lodged  in  the  reticulum;  therefore  it  is  that  at  tlie  bottom  of  the  cells  are  found 
either  small  stones,  and  needles  or  pins,  often  fixed  in  the  intermediate  septa,  or  nails, 
scrajDS  of  iron,  etc.  The  interior  of  the  reticulum  communicates  with  the  left  sac  of  the 
rumen  by  the  orifice  already  described,  and  with  the  omasum  by  a  particular  open- 
ing, placed  near  the  middle  of  the  small  curvature,  though  a  little  more  to  the  right 
than  the  left.  This  opening,  eight  or  ten  times  smaller  than  the  preceding,  is 
connected  with  the  infundibulum  of  the  cardia  by  a  remarkable  groove  (or  channel), 
the  oesophageal,  which  will  be  described  separately,  as  it  does  not  properly  belong  to  the 
reticulum. 

Structure. — The  serous  membrane  does  not  cover  all  the  anterior  surface  of  the  organ, 
as  the  latter  adheres  to  the  posterior  face  of  the  diaphragm.  The  muscidar  tunic  is  much 
thinner  than  that  of  the  pauneh,  and  more  fasciculated.  The  fibres  pass  in  the  same 
direction.  The  corium  of  the  mucous  membrane  sends  a  prolongation  into  each  of  the 
septa  of  the  alveoli,  and  into  each  of  the  conical  papillae  on  these  septa,  or  to  the  bottom 
of  these  alveoli.  The  stratified  pavement  epithelium  is  very  thick,  and  its  horny  layer 
is  very  developed  at  the  summit  of  the  papillae. 

Esophageal  Gkoove  (Fig.  193). — This  gutter  is  so  named  because  it  appears  to 
continue  the  oesophagus  to  the  interior  of  the  stomach.  It  extends  on  the  lesser 
curvature  of  the  reticulum  from  the  cardia  to  the  entranee  of  the  omasum  ;  commencing 
in  the  rumen,  it  belongs  to  the  reticulum  for  the  remainder  of  its  extent.  Measuring 
from  six  to  eight  inches  in  length,  this  demi-canal  is  directed  from  above  downwards, 
and  from  left  to  right,  between  two  movable  lips,  which  are  fixed  by  their  adherent 
border  to  the  superior  wall  of  the  reticulum.  These  two  lips  are  thickened  at  their  free 
margins,  which  look  downwards  and  to  the  left.  At  their  origin  at  the  oesophageal 
infundibulum,  they  are  thin  and  but  slightly  elevated ;  but  they  become  thick  and 
salient  on  arriving  near  the  orifice  of  the  omasum,  which  orifice  they  surround,  though 
they  neither  meet  nor  become  confounded  with  each  other. 

The  mucous  memhrane  covering  these  two  lips  is  much  corrugated  outwardly  and 
on  the  free  border ;  but  in  the  interior  of  the  groove  it  possesses  all  the  characters  of  the 
oesophageal  mucous  membrane  in  being  smooth,  white,  and  ridged  longitudinally  ;  near 
the  orifice  of  the  omasum  it  has  some  large  conical  papillaa 

If  this  membrane  be  removed  to  study  the  subjacent  tissue,  the  following  arrangement 
is  observed :  At  the  bottom  of  the  channel,  and  in  the  space  comprised  between  its  two 
lips,  are  transverse  muscular  fibres,  which  belong  to  the  rumen  or  reticulum.  The  lips 
themselves  are  entirely  composed  of  longitudinal  muscular  fasciculi,  particularly  abun- 
dant towards  the  free  border ;  these  fasciculi  are  confounded  with  the  proper  fibres  of  the 
stomach  towards  the  extremities  of  the  canal,  and  are  carried  from  one  lip  to  the  other 
in  forming  loops  around  the  orifices  which  communicate  by  this  canal. 

Omasum  {Fsalterium,  jMany-plies,  Many-leaves,  or  jNIanyplcs.    Fig.  192). — In  the 


39S 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA 


Ox,  this  compartment  id  larger  tlian  tbe  reticulum,  but  in  the  Sheep  and  Goat  it  ia 
smaller. 

Situation — Form — Relations. — Situated  above  the  cul-de-sac  of  the  reticulum  and  the 
anterior  extremity  of  the  right  sac  of  the  rumen,  this  compartment,  wlien  distended,  has  an 
oval  form,  is  slightly  curved  in  an  opposite  direction  to  the  honeycomb  division,  and 
depressed  from  before  to  behind.  It  lias,  therefore,  an  anterior  face,  applied  against  the 
diaphragm,  to  which  it  is  sometimes  attached  by  connective  tissue  ;  a  posterior  face  lying 
towards  the  paunch :  a  great  curvature,  turned  upwards,  and  fixed  in  the  posterior  fissure 
of  the  liver  by  an  omental  fra?num  which  is  continued  on  the  lesser  curvature  of  the 
abomasum  and  duodenum ;  a  lesser  curvature,  wiiich  looks  downwards  and  responds  to 
the  reticulum ;  a  left  extremity,  exhibiting  the  neck,  which  corresponds  to  the  orifice  of 
communication  between  tiie  reticulum  and  many-plies ;  a  riglil  extremity,  continuous 
with  the  base  of  the  abomasum,  from  which  it  is  separated  by  a  constriction  analogous  to 
that  of  the  anterior  extremity,  but  much  less  marked. 

Interior. — This  compartment  shows  in  its  interior  the  two  apertures  placed  at  its  extre- 
mities.   The  right  orifice,  opening  into  the  abomasum,  is  much  wider  than  the  left,  which 

Fig.  193 


>  Rf 


SECTION  OF  THE  WALL  OF  THE  OMASUM  OF  THE  SHEEP:  FROM  THE  GREAT  CURVATURE, 
SHOWING  THE  ORIGIN  OF  THE  LEAVES. 

P,  Peritoneum ;  M,  The  two  muscular  layers ;  E.  Epithelium ;  1,  1,  Principal  leaves 
at  their  origin;  2,  Secondary  leaf;  3,  3,  Leaves  of  the  third  order;  4,  Denticu- 
lated lamina ;  5,  5,  Two  planes  of  muscular  fibres  ascending  into  the  principal 
leaves,  some  issuing  from  the  muscular  layer  of  the  organ. 


communicates  with  the  reticulum.  The  cavity  which  tliese  orifices  bring  into  communica- 
tion with  tlie  adjoining  compartments,  offers  one  of  tlie  most  curious  arrangements  met  with 
in  the  viscera ;  it  being  filled  by  unequally-developed  leaves  of  mucous  membrane,  which 
follow  the  length  of  the  cavity.  These  laminae  have  an  adherent  border  attached  either 
to  the  great  curvature  or  to  the  fac«s  of  the  organ,  and  a  free  concave  border  turned 
towards  the  lesser  curvature.  They  commence  at  the  side  of  the  orifice  of  the  reticulum 
by  denticulated  ridges,  between  which  are  furrows,  and  which  are  prolonged  from  the 
base  of  the  leaves  to  the  entrance  of  the  abomasum.  At  the  latter  aperture  tney 
disappear  altogether,  after  rapidly  diminishing  in  height.  Tlieir  faces  are  studded  by  a 
multitude  of  very  liard  mamillai-y  papillfe,  resembling  grains  of  millet,  which  are  more 
developed  and  conical  on  some  of  the  leaves  than  others.  All  these  lamellar  prolongations 
are  far  from  bein^  of  the  same  extent:  t^velve  to  fifteen  are  so  wide  that  th.  ir  free  border 
nearly  reaches  the  lesser  curvature  of  the  viscus,  and  between  these  principal  leaves  are 
others  which,  thougli  regularly  enough  arraneed,  are  more  or  less  narrower.  At  first 
there  is  remarked  a  sec mdary  leaf,  half  the  width  of  the  chief  ones,  between  which  it  is 
placed;  then,  on  each  of  its  sides,  another,  one-half  narrower ;  and,  lastly,  at  the  base  of 
these,  two  denticulated  laminae  more  or  less  salient.  In  a  general  way,  the  laminte  which 
are  inserted  into  the  great  curvature  are  the  longest  and  widest ;  and  those  attached  to 
the  faces  of  the  viscus  become  shorter  and  narrower  as  they  draw  nearer  the  lesser 
curvature.  The  space  comprised  between  these  prolongations  is  always  filled  by  very 
attenuated  alimentary  matters,  which  are  usually  impregnated  by  a  very  small  quantity 
of  fluid,  but  are  also  often  dry,  and  sometimes  even  hardened  into  compact  flakes. 


THE  STOMACH. 


399 


Slructiire. — The  gerom  layer  is  a  dependency  of  tlie  peritoneum,  and  offers  nothing 
particular ;  it  does  not  completely  cover  the  anterior  face. 

The  muscular  tunic  is  much  fasciculated,  and  thin. 

The  mucous  membrane  is  remarkable  for  the  thickness  of  its  stratified  pavement 
epithelium ;  all  the  leaves  are  formed  by  two  layers  of  this  membrane,  laid  one  against  the 
other ;  and  as  their  structure  is  interesting,  we  will  notice  it. 

The  principal  leaves  are  composed  of  this  duplicature  of  mucous  membrane,  and  two 
layers  of  muscidar  fibres  between  ;  these  layers  are  opposite  each  other  at  the  commence- 
ment of  the  leaf,  and  separated  by  a  transverse  vessel ;  in  tlie  remainder  of  their  extent 
tliey  are  kept  apart  by  the  vessels  thut  pass  towards  tiie  border  of  the  leaf.  Their  fibre  s 
are  detached  from  tht-  surface  of  the  muscular  tunic  and,  at  certain  points,  from  its  deep 
layer.  In  the  smaller  leaves  there  appears  to  be  only  one  layer  of  muscular  fibres ;  on 
all  the  leaves  are  various-sized  papillae,  the  smallest  of  which  are  l»ue  a  grain  of  millet, 


Fis.  195, 


Fig.  196. 


T— 


SECTION   OP   A   LEAF   OF   THE   OMASUM. 

1,  1,  iluscular  planes ;  v,  vessel ;  2,  Epithe- 
lium ;  3,  3,  Small-sized  papillse,  round 
and  hard. 


LOXGITUDINAL  SECTION  OF  A  LARGE  PA- 
PILLA FROM  THE  OMASCJI,  SHOWING 
NERVE-CELLS   IN    ITS   INTERIOR. 


and  have  for  base  a  mass  of  condensed  connective  tissue,  whose  superficial  fibres  form  a 
kind  of  shell  (Fig.  195) ;  the  largest  are  club-shaped.  They  receive  blood-vessels,  and 
we  have  found  in  the  connective  tissue,  elements  with  a  S"mewhat  irregular  outline,  pro- 
vided with  nuclei,  which  we  considered  to  be  nerve-cells  (Fig.  196.) 

Abomasum  (Eeed  or  Eennet.  Figs.  192,  193). — Situation — Form — Tielations. — The 
abomasum  stand;?  next  to  tiie  rumen  for  capacity.  It  is  a  pyriform  reservoir,  curved  on 
itself,  elongated  from  before  to  behind,  and  situated  behind  the  oruasum,  above  the  right 
sac  of  the  rumen.  On  the  right  it  touches  the  diaphiaiim  and  tlie  hypochondriac;  on 
the  left  it  is  related  to  the  rumen.  The  greater  curcature,  turned  downwards,  receives 
the  insertion  of  the  great  omentum.  Tiie  lesser  curvature,  inclined  upwards,  gives 
attachment  to  the  serous  band  already  noticed  when  speaking  of  the  great  curvature  of 
the  omasum.  Its  5a.se  is  in  contact  with  the  cul-de-sac  of  the  reticulum,  and  is  separated 
from  the  omasum  by  the  constriction  in  the  foiTU  of  a  thick  neck,  which  corresponds  te 
the  communicating  orifice  of  the  two  stomachs.  Its  point,  directed  upwards  and  back- 
wards, is  continued  by  the  duodenum. 

Interior. — This  being  the  true  stomach  of  Ruminants,  the  mucous  membrane  lining 
its  interior  acquires  all  the  characters  which  distinguish  that  of  the  stomach  of  the 
Carnivora,  or  that  of  the  right  sac  of  the  Horse's  stomach.  It  is  soft,  spongy,  smooth  to 
the  touch,  vascular,  red-coloured,  covered  by  a  thin  epithelium,  and  provided  with 
numerous  glands  for  the  secretion  of  the  gastric  juice.  Thinner  than  in  monogastric 
animals,  this  tenuity  is  compensated  for  by  a  mtich  greater  extent  of  surface,  which  is 
still  further  increased  by  numerous  lamellar  folds.  These  latter  are  analogous  in  con- 
stitution to  those  of  the  omasum,  cross  i:i  a  veiy  oblique  manner  the  great  axis  of  the 
abomasum,  and  altogether  affect  a  kind  of  spiral  arrangement. 

The  abomasum  has  two  apertures  :  one,  situated  at  its  base,  opens  into  the  omasum ; 
the  other,  placed  opposite  to  the  first,  and  much  narrower,  is  the  pylorus,  which  is 
circumscribed,  as  in  the  other  animals,  by  a  muscular  ring. 

Structure. — The  serous  membrane  is  continuous  with  the  omenta  which  abut  on  the 
great  and  lesser  curvatures  of  the  viscus.  The  muscular  layer  is  of  tlie  same  thickness 
as  in  the  omasum.     The  internal  tunic  has  already  been  noticed. 

FrxcTioss  OF  THE  Stom.^ch  in  Rumin.\xts. — We  cannot  pretend  to  give  here  a 
complete  history  of  the  phenomena  of  rumination,  but  must  confine  ourselves  to  describe 
in  a  few  words  what  are  the  principal  attributes  of  each  gastric  dilatation. 


400  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

The  rumen  is  a  sac  where  the  aliment  taken  during  feeding-time  is  kept  in  reserve, 
and  whence  it  is  again  carried  into  the  mouth  during  rumination,  after  having  been 
more  or  less  softened. 

The  reticulum  participates  in  the  functions  of  the  rumen,  to  which  it  is  only  a  kind 
of  diverticulum.  But  it  is  particularly  with  regard  to  liquids  that  it  plays  the  part  of  a 
reservoir ;  the  solid  substances  contained  in  it  being  always  diluted  by  a  larger  quantity 
of  water. 

The  oesophageal  groove  carries  into  the  omasum  the  substances  swallowed  a  second 
time  after  rumination,  or  even  those  which  the  animal  ingests  in  very  small  quantity  for 
the  first  time. 

The  omasum  completes  the  trituration  and  attenuation  of  the  food,  by  pressing  it 
between  its  leaves. 

The  abomasum  acts  as  a  true  stomach  charged  with  the  secretion  of  the  gastric  juice  ; 
in  this  reservoir  occur  the  essential  phenomena  of  gastric  digestion. 

COMPARISON    OF    THE    STOMACH    OF    MAN    WITH    THAT    OF    ANIMALS, 

In  its  form,  the  stomach  of  Man  much  resembles  that  of  the  Carnivora. 

The  insertion  of  the  oesophagus,  however,  does  not  offer  so  large  an  infundibulum. 
The  organ  is  situated  in  the  left  hypochondriac,  and  is  nearly  horizontal. 

Everywhere  the  mucous  membrane  is  red  and  glandular ;  the  muscular  fibres  are 
disposed  in  three  planes,  as  in  Solipeds ;  but  the  superficial  and  deep  are  particularly 
directed  towards  the  left  sac. 

THE  INTESTINES.      (Figs.  204,  205,  206.) 

The  alimentary  canal  is  continued  from  the  stomach,  in  the  abdominal 
cavity,  by  a  long  tube  doubled  on  itself  a  great  number  of  times,  and 
which  terminates  at  the  posterior  opening  of  the  digestive  apparatus. 
This  tube  is  the  intestine.  Narrow  and  uniform  in  diameter  in  its  ante- 
rior portion,  which  is  named  the  small  intestine,  it  is  irregularly  dilated 
and  sacculated  in  its  posterior  part,  the  large  intesti?ie.  These  two  por- 
tions, so  markedly  defined  in  all  the  domesticated  mammals,  are  but  im- 
perfectly distinguished  from  one  another  with  regard  to  the  digestive 
phenomena  occurring  in  tlieir  anterior.  We  will  study  them  in  all  the 
animals  which  interest  us,  and  conclude  by  a  general  and  comparative 
examination  of  the  entire  abdominal  portion  of  the  digestive  canal. 

Preparation. — The  study  of  the  intestines  does  not  demand,  properly  speaking,  any 
special  preparation ;  it  being  sufficient  to  incise  the  inferior  wall  of  the  abdomen  to 
expose  these  viscera.  As  their  mass,  however,  is  heavy  and  unmanageable,  it  is 
advisable  to  expel  their  contents  in  a  manner  similar  to  that  recommended  for  the 
preparation  of  the  stomach ;  a  puncture  at  the  point  of  the  Cfecum  allows  the  escape  of 
the  substances  accumulated  in  that  I'eservoir — those  which  fill  the  large  colon  may  be 
removed  by  an  incision  made  toward  the  pelvic  curvature,  and  those  in  the  floating  colon 
by  the  rectum.  The  small  intestine  may  be  evacuated  by  three  or  four  openings  at 
about  equal  distances  in  the  length  of  the  viscus.  Having  done  this,  inflate  the 
intestines  to  somewhat  of  their  natural  volume  ;  this  preparation  then  permits  the  gen- 
eral arrangement  of  the  intestinal  mass  in  the  interior  of  the  abdomen  to  be  easily  studied. 

It  would  be  well  to  remove  the  entire  mass  altogether  from  the  body,  and  lay  it  out  on 
a  table,  so  as  to  isolate  the  various  parts,  study  them  in  succession,  and  note  their  form, 

1,   The  Small  Intestine.     (Figs,  204,  205,  206,) 

Length — Diameter. — The  small  intestine  is  a  long  tube,  which,  in  a 
horse  of  ordinary  height,  may  average  about  24  j'ards  in  length,  and  from 
1  to  If  inches  in  diameter.  This  diameter  is  susceptible  of  variation, 
according  to  the  state  of  contraction  of  the  muscular  tunic  of  the  viscus. 

Form. — This  tube  is  cylindrical,  doubled  on  itself,  presenting  two  cur- 
vatures :  one  convex,  perfectly  free ;  the  other  concave,  called  the  small  cur- 
vature^ which  serves  as  a  point  of  insertion  to  the  mesentery  that  sustains 


THE  INTESTINES.  401 

the  organ.  Removed  from  tlie  abdominal  cavity,  freed  from  the  serous  folds 
which  sixspend  it,  and  distended  by  air  or  water,  this  disposition  of  tho 
small  intestine  naturally  causes  it  to  twist  in  a  sjural  manner. 

Course  and  Belations. — The  small  intestine  commences  at  the  right  cul- 
de-sac  of  the  stomach,  from  which  it  is  separated  by  the  pyloric  constriction. 
At  its  origin  it  presents  a  dilatation  which,  in  form,  closely  simulates  a  small 
stomach,  whose  cui'vatures  are  the  inverse  of  those  of  tljc  proper  stomach. 
Placed  at  the  posterior  face  of  the  liver,  this  expansion,  or  head,  of  the  small 
intestine  begins  the  narrower  portion,  which  at  first  is  directed  forward, 
then  bends  suddenly  backward  :  thus  forming  a  loop  investing  the  base  of 
the  caecum  on  the  right  side ;  then  it  is  carried  to  the  left  in  crossing,  trans- 
versely, the  sublumbar  region,  beliind  the  great  mesenteric  artery ;  here  it  is 
joined  to  the  origin  of  the  floating  colon  by  a  very  short  serous  fr^uum.  It 
then  reaches  the  left  flank,  where  it  is  lodged,  and  where  it  forms  numerous 
folds  that  are  freely  suspended  in  the  abdominal  cavity  among  the  convolu- 
tions of  the  small  colon.  The  terminal  portion  of  this  conduit,  which  is 
easily  recognised  by  the  greater  thickness  of  its  walls  and  its  smaller 
diameter,  disengages  itself  from  these  convolutions  to  return  to  the  right, 
and  opens  into  the  concavity  of  the  cfecum,  below,  and  a  little  to  the  inside 
of,  the  point  where  the  large  colon  has  its  commencement. 

In  the  language  of  the  schools,  this  terminal  portion  is  named  the  ileum 
(eiActv,  to  heist) ;  the  part  which  is  susjDended  in  the  left  flank,  and  which 
forms  the  principal  mass  of  the  intestine,  is  designated  the  jejunum  (jejunus, 
empty) ;  and  the  curvature  formed  by  this  viscera  at  its  origin,  from  the 
pylorus  to  the  great  mesenteric  artery,  is  termed  the  duodenum  (twelve 
fingers'  breadth). 

This  classical  division  is,  however,  altogether  arbitrary,  and  scarcely 
deserves  to  be  retained.  It  would  be  better  to  divide  the  intestine  into  a 
fixed  or  duodenal,  and  a  free  oy  floating  portion. 

Mode  of  attachment. — The  small  intestine  is  maintained  in  its  position, 
at  its  extremities,  by  the  stomach  and  the  caecum.  But  its  principal  means 
of  fixation  consists  in  a  vast  peritoneal  fold,  which,  from  its  use,  is  named 
the  mesentery  {fxicrov,  h'Tepov). 

This  serous  layer  presents  a  very  narrow  anterior  part  which  sustains 
the  duodenum,  and  fixes  it  in  such  a  manner  as  to  prevent  its  experiencing 
any  considerable  displacement.  Continuous,  in  front,  with  the  gastro-hepatic 
omentum,  this  portion  of  the  mesentery  is  successively  detached  from  the 
base  of  tho  liver,  the  inferior  aspect  of  the  right  kidney,  or  even  from  the 
external  contour  of  the  base  of  the  cfecum,  and,  lastly,  from  the  sublumbar 
region,  to  be  soon  confounded  with  the  principal  mesentery.  This  becomes 
wider  as  it  approaches  the  cfecal  extremity,  and  arises,  as  from  a  centre,  from 
the  outline  of  the  great  mesenteric  artery,  to  spread  in  every  direction,  and 
is  inserted  into  the  small  curvature  of  the  floating  portion  of  the  viscus. 
The  great  length  of  this  insertion  causes  it  to  become  extended  in  a  spiral 
or  screw-like  manner,  around  its  point  of  origin.  It  may  be  remarked  that 
the  terminal  extremity  of  the  intestine  is  retained  between  the  two  serous 
layers  of  the  mesentery,  to  a  certain  distance  from  its  free  border.  This 
peritoneal  fold  consequently  forms  at  this  point,  at  the  side  opposite  to 
its  insertion  into  the  intestinal  tube,  a  particular  fraBnum,  which  is  observed 
to  be  carried  to  the  anterior  face  of  the  caecum. 

Interior. — The  interior  of  the  cylindrical  tube  formed  by  the  small 
intestine  offers  longitudinal  folds,  which  are  effaced  by  distention,  except 
towards  the  origin  of  the  duodenal  portion.     Those  met  with  in  this  situation 


402  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

possess  all  the  characters  of  the  valvidse  conniventes  (valves  of  Kerlcring)  of 
Man  ;  they  resist  the  effects  of  traction  exercised  on  the  intestinal  membranes, 
and  are  formed  by  two  mucous  layers  laid  together,  with  a  plentiful  supply 
of  connective  tissue  between  them. 

The  internal  surface  of  the  small  intestine  also  offers  for  study  a  mul- 
titude of  villosities  and  glandular  orifices,  or  follicles,  which  will  be  noticed 
hereafter.  It  communicates  with  the  inner  surface  of  the  stomach  by  the 
pyloric  orifice,  and  with  that  of  the  caecum  by  means  of  an  opening  which 
projects  into  the  interior  of  that  reservoir,  like  a  tap  into  a  barrel.  This 
projection,  which  is  not  very  marked,  is  formed  by  a  circular  mucous  fold, 
strengthened  externally  by  muscular  fibres,  and  is  named  the  ilio-coecal 
valve  or  valvula  Bauhini.  Two  additional  orifices  open  on  the  surface  of  the 
small  intestine  in  its  duodenal  portion,  from  5  to  8  inches  from  the  pylorus : 
one  is  the  orifice  common  to  the  biliary  and  principal  pancreatic  duct,  the 
other  that  of  the  accessory  pancreatic  duct. 

Structure. — The  wall  of  the  small  intestine,  like  that  of  the  other 
hollow  viscera  in  the  abdominal  cavity,  is  composed  of  three  tunics : 

1.  Serous  membrane. — This  envelops  the  organ  everywhere,  except  at  its 
small  curvature,  which  receives  the  insertion  of  the  mesentery. 

2.  Muscular  coat. — Covered  internally  by  a  layer  of  condensed  connective 
tissue  (which  is  sometimes  designated  as  a  fourth  tunic)  this  middle  mem- 
brane has  two  planes  of  fibres :  one,  superficial,  is  formed  of  longitudinal 
fibres  uniformly  spread  over  the  whole  surface  of  the  viscus ;  the  other, 
deep-seated,  is  composed  of  circular  fibres,  which  are  a  continuation  of  those 
of  the  pyloric  ring. 

3.  Mucous  membrane. — This  tunic,  extremely  interesting  to  study,  is  soft, 
spongy,  highly  vascular,  very  delicate,  and  of  a  reddish-yellow  colour.  Its 
external  face  is  loosely  adherent  to  the  muscular  layer,  and  its  free 
aspect  exhibits  the  villi,  and  the  glandular  or  follicular  orifices  already 
noticed. 

It  comprises,  in  its  structure,  an  epithelial  covering,  and  a  mucous 
derm  or  corium. 

The  epithelial  layer  is  formed  by  a  single  row  of  cylindrical  (or  columnar) 
cells,  implanted,  by  their  summit,  on  the  surface  of  the  derm,  and  lining  the 
interior  of  the«orifices  which  open  on  the  inner  face  of  the  membrane.  The 
base  of  these  cells  has  an  amorphous  cushion,  which,  when  they  are  all 
united,  appears  like  a  thin  layer  spread  on  the  inner  surface  of  the 
intestine. 

The  mucous  derm  is  thick  and  loose  in  its  deeper  portion,  and  is  con- 
Btituted  by  fasciculi  of  connective  tissue  mixed  with  elastic  fibres,  and 
lymphoid  elements.  On  its  free  surface  it  exhibits  villosities  and  depressions, 
which  correspond  to  the  glands.  It  has  a  muscular  layer,  whose  unstriped 
fibres  are  arranged  in  a  similar  manner  to  those  of  the  muscular  coat  of  the 
intestine.  Lastly,  it  contains  follicles,  and  vascular  and  nervous  reticulations. 
We  will  study  each  of  these. 

The  villi  are  the  foliated  or  conical  appendages  which  are  found  to  be 
most  developed  in  the  shortest  portions  of  the  intestine.  In  Birds  and  the 
Carnivora  they  attain  their  maximum  length ;  while  in  Euminants  they 
are  in  a  rudimentary  state,  though,  whatever  may  be  their  dimensions, 
they  are  always  visible  to  the  naked  eye.  Their  number  is  considerable, 
and  they  have  been  justly  compared  to  the  pile  of  velvet.  In  structure,  they 
are  formed  of  a  small  spongy  mass  of  embryonic  connective  tissue,  in  the 
.centre  of  which  are  one   or   more  lymphatic  (or  lacteal)  vessels,  with  a 


THE  INTESTINES. 


403 


magnificent  network  of  peripherj|,l  capillary  blood-vessels ;  tlie  whole  being 
inclosed  in  a  complete  epithelial  sheath. 


FiV.  197. 


A.    VILLI 


OF    MAX,   SHOWING   THE   BLOOD-VESSELS   AND   LACTEALS.- 
OF   A   SHEEP, 


-B.    VILLUS 


Fi?.  198. 


The  orifices  opening  on  the  intestinal  mucous  membrane  belong  either  to 
Brunner's  {duodenal)  glands,  or  to  those  of  Lieberkiihn  {simple  follicles). 

Brunner's  glands  form  a  continuous 
layer  beneath  the  duodenal  mucous  mem- 
brane. In  their  organisation,  these  small 
granular  bodies  are  exactly  like  the  acini 
of  the  salivary  glands  ;  each  acinus  pos- 
sesses an  extremely  short  excretory  duct, 
that  passes  through  the  mucous  mem- 
brane. (These  racemose  glands  secrete 
a  clear  alkaline  mucus,  w^hich  contains 
no  formed  elements,  such  as  cells  or 
nuclei.) 

The  glands  (or  cryptse  mucosse)  of 
LieherhiiJin  or  Galeati  are  placed  in  the 
substance  of  the  mucous  membrane,  and 
are  distinguished  by  their  microscopical 
dimensions,  their  considerable  number, 
and  their  tubular  form,  which  has  caused 
each  of  them  to  be  compared  to  the  finger 
of  a  glove;  they  are  implanted  perpen- 


PORTION  OF  ONE  OF  BRtmNER  S  GLANDS. 


404 


THE  DIGESTIVE  APPARATUS  IN  3IAMMALIA. 


dicularly  in  the  mucous  membrane,  and  open  on  its  free  surface.  Tliey 
are  found  throughout  the  whole  extent  of  the  intestine,  and  are  lined  with 
columnar  epithelium. 

The  solitary  glands  {glanduloe,  solitarise,  or  lenticular  glands)  are  round, 
salient  bodies,  visible  to  the  naked  eye.  They  are  somewhat  rare  in  the 
small  intestine,  but  are  more  abundant  at  the  posterior  portion  of  the  large 
intestine.  They  are  foi-med  by  a  mass  of  lymphoid  elements  enveloped  by 
some  condensed  fasciculi  of  connective  tissue.  Above  them  the  mucous 
membrane  is  sliglitly  umbilicated,  and  is  destitute  of  villi  and  tubular  glands, 
though  these  are  arranged  in  a  circle  around  the  follicles,  to  form  the 
coronce  tuhulorum.  (The  solitary  glands  usually  contain  a  cream-like 
secretion,  which  covers  the  villi  on  their  free  surface.) 

Fis:.  199 


PERPENDICULAR   SECTION   THROUGH   ONE   OP   PETER's   PATCHES   IN    THE   L0"\^ER   PART 
OF   THE   ILEUM   OF   THE   SHEEP 

a,  a,  Lacteal  vessels  in  the  villi  r  b.  6.  Superficial  layer  of  the  lacteal  vessels  {rete 
angustum);  c,  c,  Deep  layer  of  the  lacteals  (rete  arnplum);  d,  d,  EfTerent  vessels 
provided  with  valves ;  e,  Lieberkiihn's  glands ;  /,  Fever's  glands ;  g,  Circular 
muscular  layer  of  the  wall  of  intestine  ;  h,  Longitudinal  layer  ;  i,  Peritoneal  layer. 


The  aggregated  follicles  (glandulae  agminafoe)  are  nothing  more  than 
solitary  glands  collected  together  in  a  limited  space,  where  they  constitute 
what  are  known  as  the  glands  of  Peyer  or  of  Pecldin,  or  the  honeycomb 
glands.  Absent  in  the  duodenum,  and  even  at  the  commencement  of  the 
jejunum,  these  glands,  about  a  hundred  in  number,  are  very  irregularly 
placed  on  the  internal  surface  of  the  intestine  at  its  gi'eat  curvature,  on  the 
side  opposite  to  the  mesentery.     Their  form  is  oval  or  circular,  and  the 


THE  INTESTINES. 


405 


smallest  scarcely  measure  more  than  some  few  hundredths  of  an  inch  square  ; 
while  the  diameter  of  the  largest  increases  to  1^  inch. 

(Each  of  these  patches  is  composed  of  a  group  of  small,  roimd,  whitish 
vesicles,   covered   with    mucous    membrane;    these   vesicles   consist   of  a 


Fig.  200. 


Fis.  201. 


PERPENDICULAU  SECTION  THROUGH  THE  INTESTINAL  WALL  TO  SHOW  A  SOLITARY  FOLLICLE. 

a,  Liebertuhnian  glands ;    b,  Solitary  follicle ;    c,  Lacteal  vessels  sui-rounding,  but 

not  penetrating,  the  follicles ;  d,  Lai-ge  eiierent  vessels,  provided  with  valves. 

moderately-thick  external  capsule,  having  no  excretory  canal,  and  containing 
a  similar  secretion  to  that  in  the  solitary  follicles.  They  are  surrounded 
by  a  zone  or  band  of  simple  follicles,  and  the 
spaces  between  them  are  covered  with  villi.  The 
vesicles  are  usually  closed  ;  though  it  is  supposed 
they  open  at  intervals  to  discharge  their  secretion. 
The  mucous  and  submucous  coats  of  the  intestine 
are  intimately  adherent  and  highly  vascular,  oppo- 
site the  Peyerian  glands.) 

4.  Vessels  and  nerves. — The  small  intestine 
receives  its  arteries  almost  exclusively  from  the 
great  mesenteric  artery.  One,  which  goes  to  the 
duodenum,  comes  from  the  coeliac  trunk.  These 
arteries  form  a  submucous  network,  from  which 
branches  pass  inwards  and  outwards,  the  first  to 
the  muscular  and  serous  tunics,  the  second  to  the 
glands  and  the  villi.  A  tubular  network  sur- 
rounds each  Lieberkiihnian  gland,  and  is  observed 
in  each  villus  ;  while  a  spherical  reticulation  sur- 
rounds each  solitary  follicle,  loops  being  given  off 
which  penetrate  nearly  to  the  centre  of  the 
follicle. 

The  veins  have  the  same  arrangement,  and  finally  enter  the  vena  portae 
29 


VILLI  OF  INTESTINE,  WITH 
THEIR  CAPILLARY  PLEXUS 
INJECTED. 


4oa 


THE  DIGESTIVE  AFFAnATUS  IX  MA^niALIA. 


The   lymphatics   constitute    three   superposed  networks   in  the   mucous 
membrane.     The  first  is  situated  around  the  glandular  orifices ;  it  receives 

Fig.  202, 


HORIZONTAL   SECTION   THROUGH   THE   MIDDLE   PLANE   OF   THREE   PEYERIAN   GLANDS, 
SHOWING    THE    DISTRIBUTION    OF    THE    BLOOD-VESSELS   IN    THEIR    INTERIOR. 


the   central   lacteal  from 
FiV.  203 


DIAGRAMMATIC  REPRESENTA- 
TION OF  THE  ORIGIN  OF 
THE  LACTEALS  IN  A  VILLUS. 

e.  Central  lacteal ;  d,  Connec- 
tive-tissue corpuscles  with 
communicating  branches ; 
c,  Ciliated  columnar  epithe- 
lial cells,  the  attached  ex- 
tremities of  which  are  di- 
rectly contiguous  with  the 
<oanective  tissue  corpuscles. 


each  villus;  the  second  is  placed  between  tlie 
glandular  and  the  muscular  layer  of  the  mucous 
membrane  ;  finally,  the  third  exists  in  the  deep 
portion  of  the  membrane,  and  communicates  with 
the  meshes  encircling  the  closed  follicles.  The 
most  voluminous  emergent  vessels  pass  through 
the  wall  of  the  intestine  and  accompany  the  blood- 
vessels between  the  layers  of  the  mesentery,  enter- 
ing the  mesenteric  glands,  and  terminating  in  the 
reservoir  of  Pecquet  (receptaculum  chyli) 

The  nerves  are  from  the  solar  plexus;  they 
form  a  submucous  reticulation  and  a  myenteric 
plexus,  comprised  between  the  two  planes  of  the 
muscular  tunic- 
Microscopic  ganglia  are  found  on  their  coiu-se. 
Development. — The  small  intestine  shows  it- 
self at  an  early  period  in  the  foetus,  and  during 
the  foetal  existence  of  Euminants  preserves  a  very 
remarkable  predominance  over  the  large  intestine  : 
a  predominance  equally  marked  in  tlie  vessels  it 
receives,  for,  in  a  foetus  of  five  months,  we  have 
found  the  collective  arteries  of  the  small  intes- 
tine equivalent  to  about  ten  times  the  volume  of 
those  of  the  caecum  and  colon. 

Functions. — It  is  in  this  tube,  and  under  the 


THE  INTESTINES.  407 

influence  of  tlie  hepatic,  pancreatic,  and  intestinal  secretions,  that  are 
carried  on  those  molecular  transformations  which  properly  constitute  the 
digestive  function.  It  is  also  in  this  intestine  that  the  absorption  of  the 
nutritive  principles  and  fluids  commences,  and  in  which  the  villi  are  the 
essential  organs. 

2.  The  Large  Intestine. 

The  large  intestine  commences  by  a  vast  reservoir  in  the  form  of  a  cul- 
desac,  named  the  ccecum.  It  is  continued  by  the  colon,  whose  posterior 
extremity  is  succeeded  by  the  rectum.  It  is  separated  from  the  small 
intestine  by  the  ileo-ccecal  valve. 

A.  Ccecum.     (Figs.  204,  205,  206.) 

Situation — Direction. — This  is  a  very  wide  and  elongated  sac,  occupying 
the  right  hypochondriac,  where  it  affects  an  oblique  direction  downwards 
and  backwards. 

Dimensions — Capacity. — Its  length  is  ordinarily  a  little  over  thi-ee  feet, 
and  it  will  contain,  on  an  average,  about  7^  gallons  of  fluid. 

Form— External  surface. — The  elongated  sac  formed  by  the  caBcum  is 
conical  in  shape,  terminating  in  a  point  inferiorly,  and  bulging  and  curved 
like  a  crook  superiorly.  Externally,  it  exhibits  a  great  number  of  circular 
furrows,  interrupted  by  longitudinal  muscular  bands,  four  of  which  are 
observed  in  the  middle  portion  of  the  organ  ;  they  disappear  towards  its 
extremities.  The  bottom  of  these  furrows  necessarily  corresponds  to  the 
internal  ridges,  and  these  can  be  made  to  disappear  by  destroying  the 
longitudinal  bands,  which  considerably  lengthens  the  caecum ;  thus  showing 
that  these  transverse  puekerings  are  due  to  the  presence  of  the  riband-like 
cords,  and  have  for  their  object  the  shortening  of  the  intestine  without 
diminishing  the  extent  of  its  surface. 

Relations. — To  study  its  relations,  the  csecum  is  divided  into  three 
regions : 

1.  The  superior  extremity,  base,  arch,  or  still  better,  the  crooJc,  presents 
in  the  concavity  of  its  curvature,  which  is  turned  forwards,  the  insertion  of 
the  small  intestine  and  origin  of  the  colon.  Placed  in  the  sublumbar 
region,  it  responds,  superiorly,  to  the  right  kidney  and  to  the  pancreas, 
through  the  medium  of  an  abundant  supply  of  connective  tissue.  Outwardly, 
it  touches  the  parietes  of  the  right  flank,  and  is  encircled  by  the  duodenum. 
On  the  inner  side,  it  adheres  by  cellular  tissue  to  the  termination  of 
the  large  colon,  and  is  in  contact  with  the  convolutions  of  the  small 
intestine. 

'2.  The  middle  portion  (meso-ccecum)  is  in  contact,  inwardly,  with  the  same 
convolutions  and  the  large  colon  ;  outwardly,  with  the  cartilages  of  the  false 
ribs,  whose  curvature  it  follows. 

3.  The  inferior  extremity,  or  point,  VLsnallj  rests  on  the  abdominal  pro- 
longaticn  of  the  sternum;  but  as  it  is  free  and  can  move  about  in  every 
direction,  it  often  happens  that  it  is  displaced  from  this  situation. 

3Iode  of  attachment. — The  caecum  is  fixed  to  the  sublumbar  region  and 
the  terminal  extremity  of  the  large  colon  by  a  wide  adherent  surface. 
All  around  this  surface  the  peritoneum,  which  constitutes  the  serous 
covering  of  the  caecum,  is  gathered  into  folds,  and  in  passing  from  the 
cascum  to  the  origin  of  the  colon,  this  tunic  forms  a  particular  short  and 
narrow  fraenum  designated  the  meso-ccecum. 


408 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


Interior. — Viewed  internally,  the  caecum  offers  for  study  the  valvulce  or 
transverse  ridges  corresi)onding  to  the  external  furrows.  We  have  already 
seen  that  these  are  due  to  simple  circular  folds,  comprising  in  their  thick- 
ness the  three  tunics  of  the  organ,  and  that  they  are  susceptible  of  being 
effaced  by  distention,  to  re-appear  afterwards  in  varying  number  and  position  ; 
differing  widely,  in  this  respect,  from  the  valvulae  conniventes  of  the  small 
intestine. 

Two  orifices,  placed  one  above  the  other,  open  on  the  internal  surface  of 
the  caecum,  at  the  point  corr'^ioouding  to  the  concavity  of  the  crook.     The 

Fis.  204 


GENERAL  VIEW  OP  THE  INTESTINES  OF  THE  HORSE  ;  SEEN  FROM  THE  RIGHT  SIDE, 
WITH  THE  PELVIC  CURVATURE  AND  A  PORTION  OF  THE  SMALL  INTESTINE 
CARRIED    BEYOND    THE    ABDOMINAL   CAVITY. 

a,  (Esophagus  ;  b,  Right  sac  of  the  stomach ;  c,  Small  intestine,  showing  its  origin, 
or  duodenal  portion  encii-cling  the  base  of  the  caicum ;  d,  Ca3cum  ;  e,  Origin  of 
the  large  colon ;  /,  First  portion  of  the  large  colon ;  g.  Suprasternal  flexure ;  h. 
Second  portion  of  the  large  colon  ;  t,  Pelvic  flexure  ;  j,  Third  portion  of  the  large 
colon ;  k,  Diaphragmatic  flexure  ;  I,  Fourth  portion  of  the  large  colon ;  m,  Ter- 
mination of  the  free  colon  ;  n,  Rectum  ;  o,  Mesentery  proper ;  ]?,  Colic  mesentery 
(meso-colon) ;  r,  Neck  of  the  vaginal  canal ;  s,  Spermatic  vessels ;  t.  Deferent 
canal ;  u,  Bladder;  v,  Vesicular  seminales;  x,  Pelvic  enlargement  of  the  deferen 
canal ;  y,  Prostate  ;  z,  Suspensory  ligament  of  the  penis. 

most  inferior  represents  the  terminal  opening  of  the  small  intestine  at  the 
centre  of  the  ilio-ccecal  valve,  whose  presence  in  the  domesticated  animals 
has,  in  consequence  of  a  wrong  ajipreciation  of  analogies,  been  denied ;  it  is 
nothing  more  than  the  projection  described  as  being  made  by  the  end  of  the 
small  intestine.  The  second  opening,  placed  about  1^  or  2  inches  above 
the  preceding,  and  puckered  around  its  margin,  establishes  a  communication 
between  this  viscus  and  the  colon.  If  this  opening  be  compared  with  the 
capacity  of  the  canal  which  begins  from  it,  it  will  be  remarked  that  it  could 
scarcely  be  narrower. 


TEE  INTESTINES 


409 


Fig.  205. 


A,  The  duodenum  as  it  passes 
behind  the  great  mesen- 
tric  artery  ;  B,  Free  por- 
tion of  the  small  intes- 
tine ;  C,  Ileoc£Ecal  portion  ; 
D,  Cffioura ;  E,  F,  G,  Loop 
formed  by  the  large  colon ; 
G,  Pelvic  flexure ;  r,  F, 
Point  where  the  colic  loop 
is  doubled  to  constitute 
the  suprasternal  and  dia- 
phragmatic flexures. 


GENERAL   VIEW   OF   THE    HORSE's   INTESTINES;    THE   ANEVIAL   IS   PLACED   ON   ITS 
BACK,   AND   THE   INTESTINAL  MASS   SPREAD  OUT. 


410 


THE  DIGESTIVE  APPARATUS  IN  3IA3IMALIA. 


Structure. — The  serous  tunic  does  not  call  for  any  notice  beyond  that 
already  given  when  speaking  of  the  attachments  proper  to  the  cfecum.  The 
muscular  tunic  is  formed  of  circular  fibres,  crossed  externally  by  longitudinal 
bands,  which  maintain  the  organ  in  transverse  folds.  The  mucous  mernhrane 
is  thicker  than  that  of  the  small  intestine,  and  is  also  distinguished  from  it 
by  the  absence  of  the  Brunnerian  and  aggregated  glands.  It  has,  however, 
the  solitary  follicles  and  crypts  of  Lieberkiihn,  as  well  as  some  few 
intestinal  villi.  The  blood-vessels  are  the  coical  arteries  and  veins.  The 
lymphatics  pass  to  the  sublumbar  receptacle;  and  the  nerves  are  derived 
from  the  great  mesenteric  plexus. 

Functions. — The  caecum  serves  as  a  reservoir  for  the  enormous  quantities 
of  fluid  ingested  by  herbivorous  animals.  The  greater  part  of  this  fluid,  in 
its  raj)id  passage  through  the  stomach  and  small  intestine,  escapes  the 
absorbent  action  of  the  villi  and  accumulates  in  the  caecum,  where  it  may  be 
said  to  wash  the  alimentary  mass  with  which  it  comes  in  contact ;  thus 
dissolving  the  soluble  and  assimilable  matters  this  mass  may  yet  contain, 
and  favouring  their  entrance  into  the  circulation  through  the  immense 
absorbing  surface  formed  by  the  mucous  membrane  of  the  large  intestine. 

It  docs  not  appear  that  the  aliment  is  submitted  in  the  caecum  to  any 
transformation,  all  the  molecular  changes  of  the  digestive  process,  properly 
speaking,  having  been  accomplished  when  the  mass  reached  the  interior  of 
this  viscus. 

B.  Colon. 
The  colon  is  divided  into  two  portions,  which  differ  from  each  other  iu 

Fig  206. 


THE   COLON   OF   THE   HORSE. 

1,  First  portion  ascending  to  form  the  suprasternal  flexure;  2,  Second  portion 
descending  to  form  the  pelvic  flexure,  7  ;  3,  6,  Longitudinal  muscular  bands ; 
4,  Point  of  the  csecum,  5  ;  8,  Duodenum  ;  9,  Small  intestine. 

volume,  and  in  the  disposition  they  aflfect  in  the  abdominal  cavity.     The 
first  is  the  large  or  double  colon;  the  second,  the  small  or  floating  colon. 

The  Large  or  Double  Colon  (Figs.  204,  205,  206). — This  intestine 


THE  n\TESTL\ES.  411 

begius  at  the  cfecum,  and  terminates  by  suddenly  contracting  at  the  origin 
of  the  small  colon. 

Length — Capacity. — It  is  from  about  10  to  13  feet  in  length,  and  has  a 
medium  capacity  equal  to  18  gallons. 

Foi-m — General  disposition. — Kemoved  from  the  abdominal  cavity,  and 
extended  on  a  table  or  on  the  ground,  this  portion  of  the  intestine  appears  as 
a  voluminous  canal,  offering  a  succession  of  dilatations  and  contractions ; 
its  surface  being  traversed  by  longitudinal  bands,  and  sacculated  and 
furrowed  transversely  for  a  gi'cat  i)art  of  its  extent,  exactly  like  the  cfecum. 
It  is  also  doubled  in  such  a  manner  as  to  form  a  loop,  whose  two  branches 
are  of  equal  length  and  are  held  together  by  the  peritoneum,  which  is 
carried  from  one  to  the  other ;  so  that  the  terminal  extremity  of  the  large 
colon  returns  towards  the  point  of  its  origin. 

But  this  colic  flexure,  owing  to  its  length,  could  not  be  contained  in  the 
abdomen  ;  and  it  is  therefore  doubled  in  its  turn  from  above  to  below  and 
from  right  to  left  (at  the  points  f,  f,  in  Fig.  20  )  ^ 

and  forms  curvatures  wlfich  will  be  noticed   prt-  s-  -    • 

sently.  From  this  circumstance,  it  hapjiens  that 
the  large  colon,  studied  in  the  abdominal  cavity, 
is  divided  into  four  portions  lying  beside  each 
other  in  pairs  ;  so  that  a  transverse  section  of  that 
cavity,  made  in  front  of  the  base  of  the  cfecum, 
would  give  for  this  intestine  the  results  indicated 
in  the  annexed  figure. 

Course  and  Relations. — In  following  the  course 
of  the  large  colon  from  its  origin  to  its  termina- 
tion, in  order  to  studv  its  four  portions  in  their 

'      ,         1     ,.  ,1       i-   n         •  •         1-  1  PLAN   OF   THE   COLON. 

normal  relations,  the  tollowmg  is  observed : 

Commencing  from  the  arch  of  the  caecum,  the  colon  is  directed  forwards, 
above  the  middle  portion  of  that  reservoir,  which  it  follows  to  its  point. 
Arrived  at  the  posterior  face  of  the  diaphragm  at  its  most  declivitous  part, 
it  bends  downwards  and  to  the  left,  forming  its  first  or  suprasternal  fiexxire, 
because  it  rests  on  the  xiphoid  cartilage  of  the  sternum  (Fig.  204,  g).  Here 
begins  the  second  portion  of  the  viscus,  which  is  in  immediate  contact 
w'ith  the  inferior  abdominal  wall,  and  extends  backwards  into  the  pelvic 
cavity,  where  it  is  inflected  to  the  left  to  constitute  the  pelvic  Jlexure.  This 
curvature,  the  centre  of  the  colic  loop,  responds  to  the  rectum  and  bladder, 
as  well  as  to  the  deferent  canals,  or  the  uterus  and  ovaries,  according  to 
the  sex.  It  is  succeeded  hy  the  third  portion  of  the  colon,  which  is  carried 
forward,  above,  and  to  the  left  of  the  preceding.  Bound  to  the  second 
division  by  peritoneum  and  connective  tissue,  this  new  section  reaches  the 
phrenic  centre,  and  is  then  doubled  upwards  and  to  the  right.  The  flexure 
arising  from  this  third  duplicature  is  called  the  diapJiragniatic,  because  of  its 
relations  with  the  musculo-aponeurotic  membrane  which  partitions  the  great 
cavity  of  the  trunk,  or  the  g astro-hepatic  curvature,  in  consequence  of  its  lying 
equally  against  the  liver  and  stomach  (it  is  also  designated  the  sigmoid  Jlexure) 
(Fig.  204.  h).  To  this  flexure  succeeds  the  fourth  and  last  portion  of  the 
large  colon,  bound  to  the  first  portion,  as  the  second  is  to  the  third.  This 
extends,  posteriorly,  to  the  base  of  the  Cfecum,  where  it  terminates  in  a 
sudden  contraction,  and  is  continued  by  the  small  colon  ;  it  occupies  the 
sublumbar  region,  and  through  the  medium  of  a  cellular  layer  is  applied 
against  the  inferior  face  of  the  pancreas  and  the  inner  side  of  the  caecal  arch. 

3Iode  of  attachment. — The  large  colon  can  be  easily  displaced  in  the 


412  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

abdominal  cavity.  It  is  nevertheless  fixed :  1,  By  its  origin,  to  the  caecum 
and  to  the  serous  frfenum  which  attaches  it  to  that  receptacle ;  2,  By  the 
adherence  of  its  terminal  portion  to  the  pancreas  and  the  cross  of  the  caecum ; 
3,  By  the  mesocolon.  The  latter  ligament  forms,  in  the  concavity  of  the 
pelvic  flexure  a  kind  of  racket,  the  handle  of  which  is  prolonged  to  a  short 
distance  between  the  two  branches  of  the  colic  flexure.  Beyond  this,  these  two 
branches  are  directly  placed  side  by  side. 

External  surface. — We  ha.ve  seen  that  the  large  colon  does  not  oifer  the 
same  diameter  everywhere,  and  that  it  is  bosselated,  plicated,  and  traversed 
by  longitudinal  bands  ;  it  is,  however,  important  to  study  in  detail  this  dis- 
position of  its  external  surface  in  each  of  the  regions  already  named. 

At  its  origin,  the  large  colon  is  extremely  narrow,  and  scarcely  equal  to 
the  small  intestine.  But  it  soon  dilates  and  assumes  a  considerable  volume, 
which  it  preserves  beyond  the  pelvic  flexure.  It  then  becomes  progressively 
constricted  to  the  middle  of  its  third  portion,  where  the  diameter,  reduced  to 
its  minimum,  is  yet  much  greater  than  at  the  origin  of  the  first  portion. 
Near  the  diaphragmatic  flexure,  the  large  colon  i^  again  gi-adually  dilated, 
and  finishes  by  acquiring,  near  its  termination,  the  greatest  volume  it  has 
yet  exhibited.  The  muscular  bands  which  maintain  its  transverse  folds 
throughout  the  whole  extent  of  its  first  dilated  portion,  are  four  in  number. 
Three  disappear  in  arriving  towards  the  pelvic  curvature,  and  the  only  one 
remaining  is  that  which  is  placed  in  the  concavity  of  that  curvature.  At 
the  second  dilatation  there  are  three  bands,  two  of  which  are  prolonged  to  the 
floating  colon.  The  transverse  folds  formed  by  these  flat  bands  are  but 
faintly  marked  towards  the  pelvic  curvature,  and  are  altogether  absent  in 
the  narrow  portion  succeeding  it ;  it  is  only  in  the  whole  extent  of  the  first 
dilatation  that  they  are  deepest  and  most  numerous. 

Internal  surface.  — This  is  exactly  like  that  of  the  cfecum. 

Structure. — The  serous  memhrane  envelops  the  whole  organ,  except  in 
those  places  where  it  comes  in  contact  with  itself  or  with  other  viscera.  So 
it  happens  that  the  peritoneum,  in  passing  from  the  sublumbar  region  to 
the  last  portion  of  the  colon,  does  not  cover  the  surface  which  adheres  by 
cellular  tissue  to  the  inferior  aspect  of  the  pancreas  and  caecum ;  neither,  in 
being  carried  from  one  branch  of  the  colic  flexure  to  the  other,  does  it  envelop 
their  opposed  sides,  except  at  the  pelvic  flexure,  where  it  forms  the  meso- 
colon. 

Tlie  muscular  tunic  does  not  differ  in  its  arrangement  from  that  of  the 
caecum  ;  neither  does  the  mucous  memhrane.  The  arteries  emanate  from  the 
great  mesenteric ;  they  are  the  tirio  colic  arteries.  The  two  satellite  veins 
soon  form  a  single  trunk,  which  enters  the  vena  portae.  The  lymphatics  empty 
themselves  into  Pecquet's  reservoir.  The  nerves  emerge  from  the  great 
mesenteric  plexus. 

The  Small,  or  Floating  Colon  (Fig.  204). — This  is  a  bosselated  tube, 
which  succeeds  the  large  colon,  and  is  terminated  in  the  pelvic  cavity  by  the 
rectum. 

Length—  Form — Course — Belations. — This  tube  is  about  10  feet  in  length, 
and  offers  a  disposition  analogous  to  that  of  the  small  intestine,  except  that 
it  is  double  the  size  of  that  viscus,  is  regularly  bosselated  on  its  surface,  and 
is  provided  with  two  wide  and  thick  longitudinal  bands,  one  on  the  side  of 
its  great,  the  other  on  its  small,  flexure.  Arising  from  the  terminal 
extremity  of  the  large  colon,  to  the  left  of  the  caecum,  where  it  responds  to 
the  termination  of  the  duodenum,  and  where  it  receives  the  insertion  of  the 
great  omentum,  this  intestine  is  lodged  in  the  left  flank,  forming  folds  which 


THE  INTESTINES.  413 

are  mixed  Tvitli  the  convolutions  of  tbe  small  intestine.  It  afterwards 
passes  into  the  pelvic  cavity,  to  be  directly  continued  by  the  rectum. 

Mode  of  attachment. — Floating  like  the  small  intestine,  the  small  colon  is 
suspended  by  a  serous  layer,  exactly  similar  to  the  mesentery  proper,  though 
wider,  and  named  the  colic  mesentery.  This  mesentery  is  detached  from  the 
sublumbar  region,  not  from  around  a  central  point,  but  from  a  line  extending 
from  the  great  mesenteric  artery  to  the  bottom  of  the  pelvic  cavity.  It  is 
narrower  at  its  extremities  than  in  its  central  portion. 

Interior. — The  internal  surface  of  the  floating  colon  shows  valvular  folds, 
analogous  to  those  of  the  Cfecum  and  large  colon.  It  is  in  the  intervals 
between  these  that  the  faecal  matters  are  moulded  into  balls. 

Structure. — The  serous  membrane  is  without  special  interest,  and  the 
muscular  tunic  is  similar  to  that  of  the  large  colon.  The  mucous  memlrane 
is  also  the  same.  These  membranes  receive  their  blood  by  the  small,  and 
a  branch  of  the  great,  mesenteric  artery.  A  venous  trunk,  passing  between 
the  layers  of  perituneum  composing  the  mesentery,  carries  back  the  blood 
to  the  vena  portae.  The  lymphatics  are  nearly  as  fine  and  as  numerous  as 
those  of  the  small  intestine ;  they  enter  the  same  confluent,  the  reservoir  of 
Pecquet. 

FuxcTioxs  OP  THE  CoLCN.— In  this  intestine  is  accomplished  the  ab- 
sorption of  fluids,  and  of  soluble  alible  matters.  When  the  alimentary  mass 
arrives  in  the  small  colon,  deprived  of  its  assimilable  principles  and 
charged  with  excretory  substances  thrown  out  on  the  surface  of  the  intes- 
tinal tube,  it  loses  its  name  and  receives  that  of  excrement  or  fceces.  These 
excrements,  compressed  by  the  peristaltic  contractions  of  the  muscular  tunic, 
are  divided  into  little  rounded  or  oval  masses,  which  find  theii"  way  to  the 
rectum,  where  they  accumulate,  and  Avhence,  in  due  course,  they  are  expelled. 

C.  B.ectum.     (Fig.  204.) 

The  rectum  extends,  in  a  straight  line,  from  the  entrance  to  the  pelvic 
cavity  to  the  posterior  opening  of  the  digestive  canal,  or  anus.  It  is  no- 
thing more,  properly  speaking,  than  the  extremity  of  the  small  colon,  the 
limit  which  separates  them  being  somewhat  arbitrary ;  it  dilFers  from  that 
viscus,  however,  in  having  no  ridges,  and  in  its  w-alls  being  thicker  and  more 
dilatable,  so  that  it  can  be  distended  into  an  elongated  pouch,  and  form  a 
reservoir  or  receptacle  for  the  excrementitious  matters  until  they  are  expelled. 

Belafions.— it  responds,  superiorly,  to  the  roof  formed  by  the  os  sacrum  ; 
inferiorly,  to  the  bladder,  the  deferent  canals,  vesiculae  seminales.  prostate 
gland.  Cottier's  glands,  or  to  the  vagina  and  uterus ;  laterally,  to  the  sides 
of  the  pelvis. 

Mode  of  attachment. — There  ought  to  be  considered  as  such:  1,  The 
posterior  extremity  of  the  colic  mesentery,  representing  the  mesorectum ; 
2,  An  orbicular  fold,  constituted  by  the  peritoneum  in  its  circular  reflection 
around  this  viscera  at  the  extremity  of  the  pelvic  cavity  ;  3,  The  suspensory 
ligaments  of  the  penis,  which,  joining  under  the  rectum,  form  a  ring  en- 
circling the  posterior  extremity  of  the  intestine  {see  Fig.  204  and  the 
description  of  the  penis)  ;  4,  A  thick,  triangular  fasciculus,  comprising  two 
lateral  parts,  and  composed  of  white  muscular  fibres  ;  this  fasciculus,  which 
is  really  a  prolongation  of  the  muscular  tunic  of  the  viscera,  is  detached  from 
the  rectum  above  the  anus,  and  is  attached  to  the  inferior  aspect  of  the 
coccygeal  bones,  between  the  inferior  sacro-coccygeal  muscles,  where  its 
outline  can  be  seen  beneath  the  skin  when  the  tail  is  elevated. 


414  THE  DIGESTIVE  APPARATUS  IN  MABIMALIA. 

Structure, — The  serous  membrane  does  not  envelop  the  whole  of  the 
organ  ;  that  portion  which  traverses  the  bottom  of  the  pelvic  cavity  being 
left  uncovered  by  it.  The  muscular  layer  is  very  thick,  and  composed 
of  largo,  longitudinal,  and  slightly  spiral  fasciculi,  beneath  which  are 
annular  fibres.  The  mucous  memhrane,  loosely  attached  to  the  muscular 
tunic,  shows  longitudinal  and  transverse  rugae.  The  small  mesenteric  and  the 
internal  pudic  artery  (artery  of  the  hiilh)  supply  these  membranes  with  blood. 
The  nerves  are  derived  from  the  pelvic  or  hypogastric  plexus. 

Anus. — The  anus,  or  posterior  opening  of  the  digestive  tube,  is  situated 
at  the  posterior  extremity  of  the  rectum,  under  the  base  of  the  tail,  where, 
in  Solipeds,  it  can  be  seen  forming  a  rounded  prominence  which  diminislies 
with  age.  It  is  the  border  or  margin  of  this  orifice,  which  is  corrugated 
like  the  mouth  of  a  draw-purse,  where  the  intestinal  mucous  membrane 
meets  with,  and  is  continued  by,  the  external  skin. 

In  proceeding  from  within  outwards,  there  are  found  the  following 
elements  entering  into  tho  structure  of  the  anus  :  1,  Tlie  mucous  membrane 
of  the  rectum ;  2,  The  prolongation  of  the  circular  and  longitudinal  fibres 
of  the  muscular  layer,  forming  what  is  named  the  internal  sphincter; 
3,  A  sphincter  muscle,  composed  of  red  fibres,  which  receives  the  insertion  of 
a  retractor ;  4,  The  fine,  hairless,  and  closely-attached  skin,  which  covers 
the  sphincter  ;  though  destitute  of  hair,  it  is  rich  in  sebaceous  follicles.  We 
will  only  notice  the  muscles. 

The  SPHINCTER  OF  THE  ANUS,  (spMucter  ani)  is  foi-med  of  circular  fibres, 
some  of  which  are  fixed  above,  under  the  base  of  the  tail,  and  are  confounded, 
below,  with  the  muscles  of  the  perineal  I'egion.  Comprised  between  the 
skin  and  the  prolongation  of  the  muscular  layer  of  the  rectum,  this  muscle 
is  (during  life)  in  a  state  of  almost  permanent  contraction  to  keep  the  anal 
aperture  closed,  it  being  only  relaxed  during  the  expulsion  of  ffecal  matters. 

The  RETRACTOR  OF  THE  ANUS,  OF  iscHio-ANAL  musclc  (retractor  ani),  is  a 
wide  band  attached  to  the  internal  surface  of  the  ischiatic  ligament  (sacro- 
ischiatic),  and  even  to  the  supercotyloid  crest,  by  aponeurotic  fibres.  The 
fasciculi  composing  this  band  are  all  parallel  to  each  other,  while  their 
posterior  extremities  are  insinuated  beneath  the  sphincter,  and  are  confounded 
with  its  fibres.  This  arrangement  of  the  retractor  ani  clearly  indicates  that 
it  pulls  the  anus  forwards,  re-establishing  it  in  its  normal  position  after 
expulsion  of  the  fseces  :  an  act  which  always  results  in  carrying  the  posterior 
extremity  of  the  rectum  backwards. 

These  two  muscles  are  of  a  red  colour,  and  belong  to  those  of  animal 
life.  Their  vessels  are  derived  from  the  same  sources  as  those  of  the  rectum, 
'i'he  hagmorrhoidal  nerve  supplies  them  both  with  filament 

DIFFEREMTIAIi   CHARACTERS   OF   THE    INTESTINES    IN    OTHER    THAN    SOLIPED    ANIMALS. 

In  the  domesticated  animals,  the  intestines  vary  as  much  in  tbeu"  dimensions,  length, 
and  diameter,  as  in  their  general  disposition. 

1.  The  Intestines  of  Buminanis.     (Fig.  208.) 

The  small  intestine  of  the  Ox  floats  at  the  extremity  of  a  broad  mesenteric  lamina, 
which  is  narrower  in  front  than  behind,  plane  throughout,  except  at  its  intestinal  border, 
which  is  of  considerable  length,  and  is  folded  into  a  multitude  of  festoons.  Twice  the 
length  of  the  small  intestine  of  the  Horse — averaging  about  49  yards — it  is  about 
f)ne-balf  its  diameter.  The  duodenum,  at  first  sustained  by  the  omentum,  which 
attachi'S  the  small  curvature  of  the  fourth  compartment  of  the  stomach  to  the  posterior 
fissui'e  of  the  liver,  forms  a  particular  loop,  which  is  in  contact  with  the  sublumbar 
region  before  it  goes  to  be  suspended  by  the  large  mesentery,  and  to  be  continued  by  the 
cjiivol-utions  of  the  floating  portion.    The   ileum  termiu;ites   as  in  the  Horse.     Tha 


THE  INTESTINES. 


415 


Peyorian  glands  are  less  numerous  on  the  internal  surfoce  of  the  small  intestine  than 
in  Solipeds,  thuugh  they  are  larger  iu  size.  In  tlie  Sheep  and  Goat,  they  are  often 
more  than  eight  inches  in  length,  and  extend  to  Bauhin's  (ileo-  cajcal )  valve. 

The  cxcinn  is  nearly  cylindrical  in  form,  without  bulges  or  longitudinal  bands.  The 
extremity  of  the  cul-de-sac,  rounded  and  globular,  floats  freely  in  the  abdominal  cavity, 
anil  is  directed  backwards.  At  its  opposite  extremity,  the  crecum  is  continued  directly 
with  the  colon,  without  forming  a  crook,  after  having  received  the  insertion  of  the  small 
intestine. 

In  the  0.r,  in  the  vicinity  of  this  insertion,  there  are  traces  of  one  of  Peyer's  patches. 
In  the  Shee})  and  Goat,  these  patches  are  very  numerous. 

The  colon,  sustained  between  the  layers  of  the  great  mesentery,  on  the  margin  of 
which  is  suspended  the  small  intestine,  is  rolled  upon  itself  in  such  a  way  as  to  form 
a  certain  number  of  elliptical  convolutions,  by  at  first  making  several  concentric  spiral 
turns,  which  leave  a  certain  interval  between  them  for  the  reception  of  the  excentric  convo- 
lutions.    The  last  spiral  turn  is  a  little  distant  from  the  others ;  in  the  smaller  Ruminants, 

Fisr.  208. 


GENERAL   VIEW   OF    THE    INTESTINES    OF    THE   OX  ;    RIGHT    FACE. 

A,  Orit^in  of  the  duodenum;  B,  Floating  portion  of  the  small  intestine;  C,  Termina- 
tion of  the  small  intestine ;  D,  Cxcum ;  e,  Its  point  directed  backwards ;  F, 
Flexure  of  the  large  colon  at  its  termination ;  G,  H,  Terminal  portion  of  the 
intestine. — 1,  Insertion  of  the  ductus  choledochus ;  2,  Insertion  of  the  pancreatic 
duct. 

it  is  close  to  the  insertion  of  the  mesentery  m  the  small  intestine,  which  it  follows  to 
near  the  duodenum  in  describing  regular  festoons.  On  reaching  the  trunk  of  the  great 
mesenteric  artery,  this  convolution  passes  to  the  right,  and  in  directed  backwards,  then 
forwards,  thus  forming  a  flexure,  and  turns  back  in  company  with  the  duodenal 
flexure.  The  colon  then  continues  in  a  direct  line  to  the  rectum,  attachi  d  to  a  short 
mesenteric  layer,  which,  by  its  position,  resembles  the  large  suspensory  band  of  the 
floating  colon  in  Solipeds. 

The  calibre  of  this  intestine  is  at  first  equal  to  that  of  the  ca3cum ;  but  it  soon  becomes 
constricted,  and  maintains  a  uniform  diameter,  which  scarcely  exceeds  that  of  the  small 
intestine  of  the  Horse.  The  muscular  layer  has  the  same  arrangement  as  in  the  latter, 
although  it  is  not  covered  in  all  its  points  by  the  serous  tunic,  in  consequence  of  the 
situation  of  the  colon  between  the  two  layers  of  the  mesentery.  In  emaciated  animals, 
however,  it  may  be  remarked  that  the  serous  covering  furnished  by  these  layers  to  the 
muscular  coat  of  the  colon  is  more  extensive  than  at  first  we  might  be  led  to  think ;  on 
tlie  left  side,  the  prominences  of  the  spiral  convolutiuus  are  found  tf)  stand  in  relief  on 
the  surface  of  the  mesentery,  and  it  is  therefore  more  completely  enveloped  in  the 
corresponding  peritoneal  layer. 

From  this  description,  it  will  be  seen  that  in  the  large  intestine  of  T?uminants  the 
aecal  division  is  well  defined,  but  that  the  division  of  the  colon  into  a  large  or  double, 
and  &,  small  or  floating  jwrtion  can  scarcely  be  made;  unless  we  regard  as  the  large  or 
flexureil  colon  the  spiral  folds  contained  betweeTi  the  layers  of  mesentery,  and  see  the  float- 
ing portion  iu  the  pojierior  extremity  of  the  tube  lying  at  first  against  the  sublumbar  wall 


416 


THE  DIGESTIVE  APPARATUS  IN  31AMMALIA. 


of  the  abdomen,  and   afterwards   suspended   by  the   short   mesenteric  frrenum  which 


resembles  the  great  colic  mesentery  of  Solipeds. 
Fi^.  209. 


INTESTINES   OF   THE   DOG. 

a,  Stomach  ;  h,  Duodenum  ;  c,  Jejunum  ;  d,  Ileum  ;  e,  Caecum ; 
/,  Ascendmg  colon ;  g,  Transverse  colon ;  h,  Origin  of  des- 
cending colon  ;  i,  Great  omentum  ;  k,  Spleen  ;  I,  Mesentery  ; 
m,  Pancreas. — 1,  Aorta;  2,  Great  mesenteric  artery,  3, 
Artery  of  the  duodenum  ;  4,  Artery  of  the  large  mtestine  , 
5,  Small  mesenteric  artery. 


It  is  worthy  of  remurk  that  the  ^reat 
mesenteric  artery  goes  to  the 
first,  and  the  small  mesen- 
teric to  the  second  portion, 
as  in  the  Horse. 

Measured  throughout  its 
whole  extent,  from  the  cjecal 
cul-de-sac  to  the  anus,  the 
large  intestine  of  the  Ox  is 
from  33  to  39i  feet.  It  is, 
therefore,  longer  than  that 
(if  the  Horse;  but  its  capa- 
city is  much  less,  for  it  does 
not  exceed  from  6J  to  7^ 
gallons. 

2.  llie  Intestines  of  the  Pig. 

The  average  length  of 
the  I'if/s  intestines  is  about 
72  feet,  of  wliieli  56  go  to 
the  small,  and  16  to  the 
large  intestine. 

In  their  general  dispo- 
sition they  bear  some  resem- 
blance to  those  of  the  Ox  ; 
though  only  the  last  portion 
of  the  colon  is  included  be- 
tween the  layers  of  the  me- 
sentery, it  being,  for  the 
remainder  of  its  extent,  out- 
side that  membrane,  where 
it  forms  a  distinct  mass. 

Among  the  peculiarities 
of  the  small  intestine,  may 
be  cited  the  presence  of  an 
immense  Peyerian  gland, 
which  occupies  the  latter 
portion  of  the  canal,  where 
it  figures  as  a  band  measur- 
ing from  5  to  6i  feet  in 
length. 

Tlie  Ccccum  shows,  on  its 
internal  surface,  some  Peye- 
rian patches ,  it  is  bosselated, 
as  in  the  Horse,  and  is  fur- 
nislied  with  three  longitu- 
dinal bands.  The  colon  has 
two  of  these  muscular  bands 
in  a  portion  of  its  track,  and 
even  three  towards  the  cae- 
cum ;  as  well  as  sume  trans- 
verse folds.  It  is  doubled 
exactly  as  in  the  Ox 


3. 


The  Intestines  in  Car- 
nivora.    (Fig.  209.) 

The    intestines    of    the 
Carnivora    are     remarkable 
for  their  shortness  and  small 
volume.     In  a  Dog  of  ordi- 
nary size,  they  scarcely  measure  more  than  14  feet  in  length,  of  which  only  24  to  28 
inches  are  for  the  large  intestine.     In  the  Cot,  the  latter  is  about  one-half  this  length, 
and  the  entire  extent  of  the  viscus  is  equal  to  about  6  or  7  f«.et.     "With  regard  to 


THE  INTESTINES, 


417 


Ficr.  210. 


capacity.  M.  Colin  J^ivcs  the  following  averages :  for  the  Dog's  small  intestine,  1  quart ; 
that  of  the  Cut,  l-4tli  of  a  pint ;  the  large  intestine  in  the  Dog,  nearly  1  quart,  aud  iu  the 
Cat.  a  tritie  more  than  l-4th  of  a  pint. 

The  small  intestine,  suspended  at  the  extremity  of  a  mesentery  similar  to  <hat  of 
Solipeds,  rests  on  the  inferior  abdominal  wall.  It  is  distinguished  by  the  thickness  of 
its  parietes,  the  length  and  number  of  its  villosities,  which  cover  its  inner  surface,  and 
which  are  even  found  accumulated  on  Peyer's  patches.  These  latter  number  about  20 
in  the  Dog,  and  5  or  (j  in  the  Cat.  The  csecum  forms  only  a  small,  spirally-twisted 
appendix,  lined  by  a  plicated  and  very  follicular  mucous  membrane,  particularly  in  the 
Cat,  which  shows  at  the  bottom  of  the  cul-de-sac  a  true  Peyer's  gland. 

The  colon  is  scarcely  larger  than  the  small  intestine,  and  is  neither  sacculated  nor 
furnished  with  longitudinal  bands.  In  its  short  course,  it  is  disposed  somewhat  like  the 
same  intestine  in  JNIan ;  and,  as  in  him,  it  may  be  divided  into  the  ascendincj  {Yh^.  209,/), 
transverse  (g),  and  descending  colon  (7i),  which  is  continued  directly  with  the  rectum. 

Near  the  anus,  this  latter  viscus  presents  on  its  sides  two  narrow  apertures  leading 
to  two  glandular  pouches,  which  are  filled  witli  a  brownish  matter,  that  has  a  strong  and 
fetid  odour,  and  which  is  secreted  by  the  glands  covering  the  internal  wall  of  these 
diverticuli. 

(Measurements  of  the  intes- 
tines, always  a  subject  of  interest 
to  comparative  anatomists,  have 
been  frequently  made  by  difterent 
authorities.  Leyh  gives  the  length 
of  the  Horses  intestines  as  from 
10  to  12  times  that  of  its  body  : 
those  of  the  Ox  as  from  20  to  22 
times ;  the  Sliee})  and  Goat  from 
26  to  28  times ;  the  Pig  from  15 
to  17  times ;  the  Dog  from  4§  to 
5 J  times;  and  the  Cat  from  4  to 
5  times. 

According  to  Hering,  the  entire 
length  of  the  intestines  of  tln' 
Horse  averages  100  "Wurtemburg 
feet,  70  of  which  are  for  the  small 
intestine,  and  30  for  the  large.  In 
the  Ox  they  are  150  feet,  120  being 
for  the  small  intestine,  and  3U 
for  the  large ;  in  the  Sheep  they 
average  90  feet,  65  to  70  being 
allowed  for  the  small  intestine; 
those  of  the  Goat  measure  95, 
the  small  intestine  being  70 ;  in 
the  Pig  they  are  90  feet,  72  of 
which  are  for  the  small  intestine, 
and  18  for  the  large ;  large-sized 
Dogs  averaged  from  23  to  27  feet, 
20  to  22  of  which  were  for  the 
small  intestine ;  small  dogs  had 
only  6  feet  in  many  instances. 
TJie  Cat  has  from  4  to  5  feet.) 


COMPARISON   OF   THE  INTESTINES  OP 
MAN   WITH   THOSE   OF   ANIMALS. 

Not  unfrequently  the  small 
intestine  of  Man  is  divided  into 
duodenum  and  small  intestine 
proper.  The  duodenum  is  from 
9  to  11  inches;  is  dilated  at  its 
origin,  and  firmly  attached  to  the 
posterior  face  of  the  liver  by  a 
peritoneal  fold,  and  to  the  right 


THE    HUMAN    INTESTINES    AND    SUPERIOR    MESENTERIC 
ARTERY. 

1 ,  Descending  portion  of  the  duodenum  ;  2,  Ti-ansverse 
portion ;  3,  Pancreas ;  4,  Jejuniun  ;  5,  Ileum ;  6, 
Ciccnm  and  appendix  vermiformis ;  7,  Ascendinc; 
colon  ;  8,  Transverse  colon  ;  9,  Descending  colon  ; 
10,  Superior  mesenteric  artery;  11,  Colica  media; 
12,  The  branch  that  inosculates  with  the  colica 
sinistra ;  13,  Pancreatico-duodenalis  inferior ;  14, 
Colica  dextva;  15,  Ileo-colica ;  16,  16,  Vasa  intes- 
tinis  tenuis. 


of  the  subluml>ar  region  by  con- 
nective tissue.     It  describes  the  arc  of  a  circle,  in  the  concavity  of  which  is  lodged  tie 
right  extremity  of  the  pancreas,  and  not  the  caicum  as  in  Solipeds. 


418  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

The  small  intestine  proper  is  suspended  by  a  mesentery  somewhat  similar  to  that  of 
the  Horse.  Its  length  varies  mufh — from  IS  to  26  feet.  Its  internal  face  has  a  large 
number  of  transverse  riigse,  the  valvulx  conniventes.  It  also  shows  from  20  to  25 
Fcyer's  patches,  particularly  in  the  ileo-ca3cal  portion.  Its  structure  is  like  that  already 
(ieocribed. 

In  the  large  intestine  is  recognised  the  csecum,  colon,  and  rectum. 

The  ca3cum  is  a  small  reservoir  placed  in  the  right  iliac  fossa,  a  little  obliquely 
downwards  and  to  the  left.  It  commences  at  the  ileo-cajcal  valve,  has  an  average  length 
of  about  2J  inches,  and  terminates  by  a  rounded  extremity  with  a  small  hollow  prolong- 
ation, averaging  3  inches  in  length,  the  cxcal  or  vermiform  appendix.  The  mucous 
membrane  is  like  that  of  animals,  and  the  muscular  tunic  is  the  same. 

The  human  colon  is  regularly  sacculated,  like  the  small  colon  of  the  Horse ;  it  begins 
in  the  right  iliac  fossa,  above  the  valvula  Bauhiui;  it  ascends  to  the  lower  face  of  the 
liver,  passes  abruptly  across  from  right  to  left,  and,  arriving  at  the  spleen,  again  changes 
its  direction  downwards  to  the  iliac  fossa  :  it  then  again  describes  the  iliac  S,  to  reach 
the  mesial  line,  where  it  is  continued  by  the  rectum.  From  this  course,  the  colon  has 
been  divided  into  three  portions :  the  ascending  colon,  transverse  colon,  and  descending 
colon.  In  the  ascending  and  transverse  colon  are  observed  three  series  of  sacculi, 
separated  by  three  muscular  longitudinal  bands ;  the  descending  colon  has  only  two. 

There  is  scarcely  anything  special  to  note  in  the  rectum  and  anus,  except  that  they, 
and  esi^ecially  the  latter,  are  very  rich  in  arteries  and  varicose  veins,  and  that  the  anus 
is  sepaiated  from  the  rectum  by  small  cavities  open  in  front,  and  which  are  found  ia 
the  Dog ;  these  are  the  sinuses  of  Moryagni. 


GESEEAL   AND   COMPAEATIVE   SURVEY   OF  THE   ABDOMINAL   OR   ESSENTIAL   rORTTON   OF  THE 

DIGESTIVE   TUBE. 

We  have  terminated  the  description  of  the  anatomical  characters  which  distinguish 
the  tssential  portion  of  the  alimentary  canal  in  all  the  domesticated  animals,  and  what 
gradations  has  this  study  revealed  !  Let  us  recapitulate  and  compare  them,  before 
showing  the  admirable  harmony  which  pervades  these  diverse  arrangements,  and 
adapts  them  to  the  variations  in  general  organisation,  habits,  and  instincts. 

In  the  Carnivora  which  subsist  on  flesh  {Dog  and  Cat),  we  have  seen  a  very  ample 
stomach,  secreting  a  gastric  fluid  throughout  the  whole  extent  of  its  mucous  membrane, 
and  intestines,  (relatively)  extremely  short. 

In  the  Oinnivora,  or  mammalia  which  live  on  a  mixed  diet  (Pig],  we  have  found  a 
small  portion  of  the  internal  surface  of  the  stomach  occupied  by  a  mucous  membrane 
unfitted  to  secrete  gastric  juice,  and  the  intestines  relatively  of  much  more  considerable 
capacity  than  in  Carnivora. 

With  the  Herbivora,  which  derive  their  nourishment  exclusively  from  the  vegetable 
kingdom  '  Buminants  and  Solipeds),  the  surface  destined  for  the  production  of  the  gastric 
juice  also  singularly  diminishes  in  extent,  although  the  stomach  in  some  of  these  animals 
is  remarkable  for  its  extraordinary  development.  But  to  compensate  for  this,  the 
capacity  of  the  intestinal  canal  assumes  considerable  proportions,  and  in  the  various 
species  is  in  directly  inverse  relation  to  the  area  of  the  gastric  surface.  This  surface 
being  relatively  more  extensive  in  Ruminants  than  in  Solipeds,  all  these  animals  ought 
to  be  classed  in  an  inverse  order  with  regard  to  the  development  of  the  intestinal 
surface. 

Finally,  in  considering  as  the  internal  surface  of  the  stomach  (a  point  of  view  quite 
rational)  only  those  portions  of  the  mucous  membrane  organised  for  the  secretion  of  the 
gastric  juice,  we  are  led  to  recognise  that  this  surface  is  in  inverse  proportion  to  that  of 
the  intestine;  that  it  reaches  its  highest  degree  of  development  in  Carnivorous  animals; 
and  that  it  is  reduced  to  the  smallest  dimensions  in  Solipeds,  animals  which,  on  the 
contrary,  present  a  very  great  development  of  the  intestinal  surface. 

The  nature  of  the  aliment  readily  accounts  for  these  remarkable  differences.  The 
Cainivora,  living  on  substantial  food,  take  it  in  very  large  quantity,  because  they  are 
exposed  to  frequent  fastings;  it  is,  therefore,  necessary  that  they  should  have  a 
stomach  Iirge  enongh  to  contain  the  ingested  substances,  and  to  secrete  the  amount  of 
g  istric  juice  neeiled  to  transform  them  into  assimilable  materials.  If  these  animals  have 
a  .short  and  nariow  intestine,  it  is  because  a  small  surface  only  is  required  to  absorb  the 
products  of  digestion,  these  being  mixed  with  but  a  minimum  quantity  of  non-nutritive 
sub.stances,  and  readily  come  in  contact  with  the  absorbing  membrane. 

With  regard  to  the  Herbivora,  their  food  contains  a  trifling  proportion  of  nutritive 
dementi  inclosed  in  an  extremely  abundant  matrix,  and  being  compelled  to  ingest  great 


ORGANS  ANNEXED  TO  THE  ABDOMINAL  DIGESTIVE  CANAL.     419 

quantities  at  short  iiit(  rvals,  the  stomach,  properly  called,  can  only  be  a  temporary 
receptacle  for  the  aliment,  wiiicli  passes  rapiiily  throuuh  it  after  being  inijiregnated  by  the 
g-istiic  juice.  The  surface  which  secretes  that  tiiiid  is  nho  singularly  reduced,  because 
if  it  has  to  perform  its  functions  more  frequently  than  in  Carnivora,  it  is  nc^t  required  to 
display  so  much  activity  in  a  given  time.  If,  on  leaving  tlie  stouiach,  the  alimenfarv 
matters  encounter  a  vast  intestinal  surface,  it  is  iu  order  that  the  reparative  materials 
dispersed  in  the  alimentary  mass  may  not  escape  the  absorbent  action  of  tiiat  surface, 
and  may  be  the  more  eftectually  brdught  into  contact  with  it.  We  have  tiiis  exemplified 
in  Kuminants  ;  owing  to  tlieir  double  mastication  and  the  triturating  action  of  the  mani/- 
plies,  their  food  arrives  in  the  stomach  proper  more  comminuted  and  bet'er  attenuated 
than  in  the  Horse ;  the  mas.^,  more  finely  broken  up,  retains  less  of  the  assimilable  and 
reijarative  matters,  and  these  are  more  easily  seized  by  the  absorbing  surface  :  and,  :is  a 
necessary  consequence,  the  intestinal  tube,  although  longer  tiian  in  fcjoiipeds,  is  far  from 
offering  the  same  capacity. 

Analogous  considerations  explain  the  reason  for  the  intermediate  conformation  of  the 
digestive  canal  in  Omnivorous  animals. 

There  is,  then,  an  admirable  correlation  between  the  conformation  of  the  digestive 
tube  and  tlje  nature  of  the  substances  which  form  the  base  of  the  alimentation  of  animals ; 
and  this  harmony  is  eqTially  apparent  when  the  stomacii  and  intestines  are  compared  with 
the  other  apparatus  of  the  economy,  and  with  the  natural  habits  and  instincts  of  creatures. 
So  it  is  tliat  a  creatitre  furnished  with  an  ample  stomach  and  narrow  intestine,  will  have 
sharp  teeth  and  claws  to  tear  its  prey,  strength  and  agility  to  capture  it,  and  will  also 
pos.-ess  sanguinary  instincts,  while  another,  with  its  gastric  surface  greatly  diminished, 
willliave  inte.-'tines  as  developed  in  their  length  as  in  the'r  capacity,  and  be  distinguished 
by  its  jieaceful  habits,  the  absence  of  aggressive  claws,  and  the  crushing  and  grinding  furm 
of  the  principal  pieces  of  its  dental  apparatus,  etc. 


ORGANS  ANNEXED  TO  THE  ABDOMINAL  PORTION  OF  THE  DIGESTIVE 

CANAL. 

These  organs  are  three  in  number  :  two  glands — the  Ever  and  'pancreas, 
which  pour  into  the  small  intestine  two  particular  fluids,  the  hile  and  pan- 
creatic juice ;  and  a  glandiform  organ,  the  spleen,  remarkable  for  its  nume- 
rous vasctilar  connections  with  different  organs  of  the  digestive  apparatus, 
and  which  for  this  reason  deserves  to  be  studied  with  it,  although  it  is 
doubtful,  if  not  improbable,  that  it  has  anything  to  do  with  digestion. 

Preparation. — These  three  organs  can  readily  be  studied  after  removing  the  intestinal 
mass,  as  indicated  at  page  385.  In  order  to  examine  the  details  of  their  organisation 
with  more  facility,  it  would  be  well  to  detach  them  altogetiier  with  the  diaphragm  and 
kidneys,  and  to  lay  out  the  whole  on  a  tuble.  (To  study  the  relations  of  tliese  three 
organs  with  tliose  of  the  abdominal  cavity,  it  is  advisable  to  place  the  sul)Ject  on  its 
sternum  after  removing  the  intestines,  and  to  detach  the  poiterior  part  of  the  body  at  the 
loins.) 

The  Liver.    (Figs.  182,  211,  216.) 

Sitiiaiion — Direction.- — This  organ  is  situated  in  the  abdominal  cavity,  to 
the  right  of  the  diaphragmatic  region,  and  in  an  oblique  direction  down- 
wards and  to  the  left. 

Weight. — The  weight  of  the  healthy  liver,  in  a  middle-sized  Horse,  is 
eleven  pounds. 

Form  and  External  Surface, — Eeleased  from  all  its  connections  with  the 
neighboiu'ing  organs,  and  viewed  externally,  it  is  seen  to  be  flattened  before 
and  behind,  irregularly  elongated  in  an  elliptical  form,  thick  in  its  centre, 
and  thin  towards  its  borders,  which  are  notched  in  such  a  manner  as  to 
divide  the  organ  into  three  principal  lobes.  This  configtn-ation  permits  it 
to  be  studied  in  two  faces  and  a  circumference. 

The  anterior  face  is  convex,  perfectly  smooth,  and  channeled  by  a  wide 


420  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

and  deep  notch  formed  for  the  passage  of  the  posterior  vena  cava.  This 
fissure  extends  directly  from  behind  to  before,  and  consequently  slightly 
crosses  the  general  direction  of  the  liver ;  near  the  point  where  the 
vena  cava  leaves  the  gland  to  traverse  the  diaphragm  are  seen  the 
openings  of  the  principal  suprahepatic  veins.  The  posterior  face  is  equally 
smooth  and  convex,  and  has  also  a  fissure  by  which  the  vena  portse  and 
the  hepatic  artery  and  nerves  enter,  and  by  which  the  biliary  ducts  emerge 
from  the  liver.  This  groove  is  slightly  concave  towards  the  left,  and  follows 
the  direction  of  the  liver  in  proceeding  obliquely  downwards,  backwards, 
and  to  the  left. 

The  circumference  may  be  divided  into  a  superior  or  left,  and  an  inferior 
or  right  border,  united  at  both  extremities  by  the  ellipsis  formed  by  the 
liver.  The  superior  border  presents,  in  jiroceeding  from  right  to  left :  1,  The 
insertion  of  the  ligament  of  the  right  lobe ;  2,  The  origin  of  the  fissure  for 
the  vena  cava ;  3,  A  notch  for  the  oesophagus ;  4,  The  insertion  of  the  left 
ligament.  The  inferior  border  is  sharp,  and  otfers  two  deep  notches,  which 
divide  the  liver  into  three  lobes :  a  superior  or  right,  an  inferior  or  left, 
and  an  intermediate  one.  The  rir/ht  lobe  is  usually  of  medium  volume, 
and  has  above,  on  its  posterior  face,  an  appendix  in  the  shape  of  a  small 
secondary  lobule  of  a  triangular  form,  whose  base  responds  to  the  com- 
mencement of  the  portal  fissures :  this  is  the  lobus  Spigelii.  The  left 
lobe  is  nearly  always  the  largest.  The  middle  lobe,  the  smallest  of  the 
three,  is  itself  divided  by  secondary  notches  into  several  digitations  or 
lobules. 

Belations. — Viewing  the  organ  in  position,  in  order  to  study  its  general 
relations,  it  is  found  that  the  anterior  face  is  apj^lied  against  the  diaphragm — 
a  disposition  which  augments  its  convexity  in  diminishing  that  of  its  pos- 
terior face ;  and  that  the  latter  is  in  contiguity  with  the  stomach,  the 
duodenum,  and  the  diaphragmatic  curvature  of  the  colon. 

The  connections  proper  to  each  lobe  are  observed  to  be  as  follows : 
I,  The  middle  lobe  responds  to  the  centre  of  the  aponeurotic  portion  of 
the  diaphragm ;  2,  The  left  lobe  touches  the  left  and  inferior  part  of  this 
aponeurosis,  and  is  prolonged  to  the  cori'csponding  point  of  the  fleshy 
peripheral  band  of  that  muscle ;  3,  The  right  lobe  is  in  contact  with  the 
right  and  superior  part  of  the  muscle ;  its  upper  border  touches  the  right 
kidney ;  the  pancreas  rests  against  its  base,  on  the  posterior  face. 

Mode  of  attachment. — The  liver  is  suspended  to  the  sublumbar  wall  of 
the  abdomen  by  the  large  blood-vessels  which  enter  its  fissures,  and  it  is 
also  fixed  to  the  posterior  face  of  the  diaphragm  by  four  particular  bands. 
One  of  these  is  carried  from  the  anterior  face  of  the  liver  to  the  phrenic 
centre,  and  appears  intended  to  oppose  total  displacement  of  the  organ  ;  the 
other  three  belong  to  each  particular  lobe. 

A.  The  ligament  of  the  anterior  face  of  the  liver  (or  coronary  ligament) 
comprises  two  series  of  very  short  aponeurotic  fibres,  which,  arising  from 
the  two  borders  of  the  vena  cava  fissure,  go  to  be  fixed  to  the  posterior  face 
of  the  phrenic  centre.  The  peritoneum  is  folded  over  it  on  each  side  in 
passing  from  the  diaphragm  to  the  liver  The  adherence  of  these  fibres  to 
the  walls  of  the  vena  cava  is  extremely  close ;  and  the  vena  cava  itself, 
being  thus  in  a  manner  united  to  the  tissue  of  the  liver,  it  happens  that 
the  union  of  the  anterior  face  of  the  viscus  wdth  the  phrenic  centre  could 
not  be  more  solidly  established. 

B.  The  ligament  of  the  left  lobe  is  a  wide  peritoneal  fold,  between  the 
two  layers  of  which  are  some  fasciculi  of  w^hite  fibrous  tissue.    It  is  detached 


ORGANS  ANNEXED  TO  THE  ABDOMINAL  DIGESTIVE  CANAL.     421 

from  the  aponeurotic  centre,  to  the  left  of  the  oesophageal  orifice,  and  is 
inserted  into  the  left  part  of  the  superior  border  of  the  liver. 

C.  The  ligament  of  the  right  lobe  is  a  fold  analogous  to  the  preceding, 
but  much  shorter,  and  whose  origin,  placed  very  high  and  near  the  sub- 
lumbar  parietes,  is  partly  covered  by  the  right  kidney.    It  is  inserted  into  the 


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f.  S  -^ 

t>  ^   bfl 

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o  .:; 

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superior  border  of  the  viscus,  and  sends  a  small  layer  to  the  lobus  Spigelii ; 
most  frequently,  hoAvever.  this  lobule  is  sustained  by  a  special  peritoneal 
frsenum,  given  off  from  the  anterior  border  of  tlie  kidney. 

D.  The  ligament  of  the  middle  lobe  (the  longitudinal,  broad,  falciform,  or 
suspensory  ligament)  is  a  falciform  and  vertical  serous  layer,  whose  adherent 
30 


422  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

border  is  attached,  almost  in  the  median  plane,  to  the  posterior  face  of  the 
diaphragm,  and  even  to  the  inferior  abdominal  parietes.  At  its  free  border 
is  a  fibrous  cord  (the  round  ligament),  formed,  by  the  obliteration  of  the 
fcetal  umbilical  vein.  By  its  upper  part,  it  penetrates  a  secondary  notch 
in  the  middle  lobe,  and  is  prolonged  on  the  anterior  face  of  this  to  tlie  point 
where  the  vena  cava  traverses  the  diaphragm. 

Structure. — As  elements  in  its  structure,  the  liver  offers  for  study : 
1 ,  A  serous  membrane  ;  2,  A  fibrous  capsule  ;  3,  The  proper  and  fundamental 
tissue  of  the  organ. 

1.  Serous  Membrane. — This  membrane  is  only  an  expansion  of  the  peri- 
toneal bands  or  ligaments  already  described,  and  of  which  the  two,  on 
arriving  at  the  organ,  separate  to  become  developed  on  its  surfaces,  and  to 
completely  cover  it,  except  in  the  anterior  and  posterior  fissures. 

2.  Fibrous,  or  Glisson's  Capsule. — This,  the  proper  envelope  of  the 
liver,  is  formed  by  a  very  fine  fibrous  membrane,  closely  adherent  to 
the  preceding  layer  on  the  one  side,  and  to  the  tissue  of  the  liver  on  the 
other.  It  penetrates  the  substance  of  that  tissue  in  passing  around  the 
vessels  lodged  in  the  posterior  fissure,  and  from  its  inner  face  it  sends  a 
multitude  of  lamellar  partitions,  which  separate  the  hepatic  granulations, 
and  form  a  veritable  framework  in  the  interior  of  the  organ.  The 
presence  of  this  capsule  has  been  denied,  but  its  existence  is  not  to  be 
doubted  in  all  the  domesticated  animals ;  it  is  particularly  well  developed 
in  Ruminants. 

3.  Proper  Tissue  of  the  Liver. — The  proper  substance  of  the  liver  is 
distinguished  by  its  bluish-brown  or  violet  hue,  the  shades  of  which  vary 
much  according  to  the  subjects.  It  is  heavy,  compact,  and  so  friable  that  it 
is  crushed  by  the  most  moderate  pressure.  It  is  composed  of  polyhedric 
granulations  from  l-20th  to  1-lOth  of  an  inch  in  diameter,  which  are 
readily  enough  distinguished  from  one  another  through  the  peritoneum  on 
the  surface  of  the  organ,  particularly  when  the  septa  thrown  in  between 
them  from  Glisson's  capsule  are  hypertrophied  from  some  slight  chronic 
irritation. 

Sometimes  the  hepatic  lobule  is  uniform  in  colour  throughout ;  often  it 
shows  a  red  central  point,  with  a  yellow  circle  around  it,  and  an  interrupted 
red  rin"  circumscribing  this  again,  and  which  communicates  with  a  similar 
circle  belonging  to  the  adjoining  lobules,  so  as  to  compose  a  network  at  the 
surface  of  the  gland  ;  at  other  times  the  lobules  are  yellow  at  the  centre  and 
red  at  the  circumference.  All  these  appearances,  the  study  of  which  at  one 
time  was  considered  of  much  importance,  are  uncertain,  and  may  vary  in  a 
thousand  ways,  in  combining  with  one  another  ;  so  that  they  really  demand 
but  little  attention,  due  as  they  are  to  the  greater  or  less  degree  of  plenitude 
of  the  different  vessels  entering  the  lobule. 

As  the  liver  is  composed  of  lobules  placed  beside  each  other,  we  will 
describe  one ;  as  when  its  structure  is  well  known,  we  will  be  familiar  with 
the  organisation  of  the  entire  organ. 

In  a  hepatic  lobule  we  find  :  1.  Hepatic  (or  hiliary)  cells ;  2,  Biliary  canal- 
iculi  (or  ducts);  3,  Afferent  vessels;  4,  An  efferent  vessel;  5,  Ltjmphatics  ; 
6,  Connective  tissue. 

Hepatic  cells. — These  are  polygonal  or  round,  and  much  resemble 
squamous  epithelium ;  their  diameter  varies  from  l-500th  to  l-200th  of  an 
inch.  They  are  composed  of  a  thin  enveloping  membrane  and  yellow- 
coloured  contents.  The  latter  comprise  one  or  two  nuclei  with  nucleoli, 
coloured  granules,  biliary  matter,  a  small  mass  of  a  substance  which  has  been 


ORGANS  ANNEXED  TO  THE  ABDOMINAL  DIGESTIVE  CANAL.     423 


Fio;.  212. 


studied  by  Bernard  and  Schiflf,  and  named  "  animal  amidon ;"  and,  lastly, 
adipose  granules,  whose  volume  and  quantity  vary  with  the  condition  of  the 
animals,  or  the  period  of  digestion  at  which  the  liver  has  been  removed. 
The  hepatic  cells  are  situated  in  the  network  formed  by  the  vessels  of  the 
lobule,  and  constitute  its  principal  portion. 

Hepatic  Ducts. — Destined  to  carry  away  the  bile  secreted  in  the  interior 
of  the  hepatic  lobule,  the  bili- 
ary ducts  iorm  around  it  a  kind 
of  girdle  that  accompanies  the 
interlobular  branches  of  the 
vena  portfe.  Within  and  with- 
out, this  girdle  sends  off  small 
pz'olongments  :  the  first  bring 
it  into  communication  with 
the  ducts  of  the  neighbouring 
lobules;  the  second  enter  the 
substance  of  the  lobule  and 
are  soon  lost. 

The  wall  of  the  biliary 
ducts  is  a  thin  amorphous 
membrane,  lined  by  polygonal 
cells,  smaller  than  the  hepatic 
cells. 

The  origin  of  the  biliary  or 
hepatic  ducts  in  the  interior  of 
the  lobules  is  still  a  vexed 
question  in  histology.  It  was 
believed,  and  some  authorities 
still  believe,  that  the  ducts  terminate  in  pouches,  at  a  short  distance  from 
the  periphery  of  the  lobule.  But  it  has  been  remarked  that  an  injection 
introduced  by  the  ductus  choledochus  does  not  remain  near  the  periphery 
of  the  lobule,  but,  on  the  contrary,  penetrates  to 
its  centre  by  passing  between  the  hepatic  cells ;  and 
from  this  it  is  admitted  that  the  hepatic  ducts  fur- 
nish a  very  fine  network  around  each  of  the  cellular 
elements  of  the  liver  (Fig.  213).  Nevertheless,  there 
are  histologists  who  do  not  share  in  this  opinion, 
who  assert  that  these  terminal  ducts  have  no 
proper  walls,  and  that  the  supposed  networks  they 
form  is  only  a  simple  system  of  intercellular  spaces 
distended  by  the  injection. 

Afferent  vessels. — These  are  the  branches  of  the 
portal  vein   and    hepatic    artery.     The    portal   vein, 
after  reaching  the  interior  of  the  liver,  divides  into 
gradually  decreasing  vessels,  until  it  terminates  by 
forming  the  interlobular  or  subhepatic  veins.     These 
vessels  surround  the  lobule,  communicate  with    the 
neighbouring  interlobular  veins,  and  give  off  a  large 
number  of  twigs  to  the  interior  of  the  lobule,  where   a,  Capillaries  of  the  biliary 
they  anastomose,  and  constitute  the  hepatic  capillary       ^^^f;  ^'  |?^P.^,^'''J^'^p*' 
plexus.     The    hepatic    artery  furnishes  ramuscules,       piUary  Wood-vessel's. 
which  mix  with  the  ramifications  of  the  portal  vein 
in   the   (vaginal)  plexus.     The   principal   branches  of  the   latter   are    all 


A.  Portion  of  a  hepatic  column,  showing  its  compo- 
nent secreting  cells ;  B,  Secreting  cells  detached  ; 
a,  In  their  normal  state  ;  b,  A  cell  more  highly 
magnified,  showing  the  nucleus  and  distinct  oil- 
particles  ;  c.  In  various  stages  of  fatty  degenera- 
tion. 


213. 


BILIARY  CAPILLARIES  OF 
THE  rabbit's  liver. 
PART  OF  A  LOBULE, 
SHOWING  THE  ARRANGE- 
MENT OP  THE  BILIARY 
DUCTS  IN  RELATION  TO 
THE    HEPATIC   CELLS. 


424 


THE  DIGESTIVE  APPAEATUS  IN  MAMMALIA. 


directed  from  the  periphery  towards  the  centre  of  the  lobule,  where  they 
unite  to  form  the  aiferent  vessel.     It  results  from  this  arrangement  that  the 

hepatic  cells  which  fill  the  spaces 
^'S-  214.  between  the  vessels  are  placed  in 

radiating  series. 

Efferent  series. — Situated  in  the 
centre  of  the  lobules,  this  vessel 
receives  all  the  ramifications  of 
the  capillary  plexus,  and  is  named 
the  intralobular  or  central  supra- 
hepatic  vein.  It  is  voluminous, 
and  communicates  with  the  other 
intralobular  veins.  (These  intra- 
lobular veins  terminate  in  the 
larger  trunks  that  run  along  the 
bases  of  the  lobules,  and  are  named 
the  siiblohular  veins.) 

Lymphatics. — In  a  hepatic  lo- 
bule are  found  very  fine  lymphatic 
vessels  that  sui-round  the  branches 
of  the  hepatic  plexus,  where  they 
form  the  lymphatic  vaginae,  or 
canals  which  contain  the  blood- 
vessels. 

Connective   tissue. — The   intra- 
lobular connective  tissue  is  scanty, 
the  lobule   being  almost  entirely 
composed  of  cells  or  capillaries ;  so  that  only  some  trabeculse  exist  around 
the  lymphatic  sheaths.     There  is,  however,  a  larger  quantity  in  the  inter- 
lobular spaces ;  and  in  some 
'^'  "    '■  animals — especially  the   Pig 

— Glisson's  capsule  sends 
somewhat  thick  lamellae  of 
connective  tissue  between 
these  lobules. 

ExcRETOEY  Apparatus. — 
This  is  very  simple  in  Soli- 
pods,  and  is  composed  of  a 
vessel  named  the  ductus  chole- 
dochus,  resulting  from  the 
luaion  of  several  trunks  lodged 
in  the  posterior  fissure  of  the 
liver,  and  which  come  from  the 
tliree  lobes.  Traced  in  the 
substance  of  the  hepatic  tissue, 
these  branches  divide  into 
more  and  more  attenuated 
ramuscules  that  arise  from 
the  periphery  of  the  lobules, 
and  are  continuous  with  the  biliary  ducts  that  envelop  and  penetrate  these. 

Course. — At  its  exit  from  the  liver,  the  ductus  choledochus  is  placed 
between  the  layers  of  the  gastro-hepatic  omentum,  and  ascends  to  the  wall  of 
the  duodenum,  which  it  passes  through  at  about  six  inches  from  the  pylorus, 


HORIZONTAL  SECTION  OF  THREE  SUPERFICIAL 
LOBULES,  SHOWING  THE  TWO  PRINCIPAL 
SYSTEMS   OF    BLOOD-VESSELS. 

a,  a,  Intralobular  veins,  terminating  in  the 
hepatic  veins;  b,  b,  Interlobular  plexus, 
formed  by  branches  of  the  portal  vein. 


SECTION  OF  A  SMALL  PORTION  OF  THE  LIVER  OF  A 
RABBIT,  WITH  THE  HEPATIC  OB  INTRALOBULAR 
VEINS   INJECTED. 


OBGANS  ANNEXED  TO  THE  ABDOMINAL  DIGESTIVE  CANAL.      425 

along  with  the  principal  pancreatic  duct.  The  orifices  of  these  two  canals 
are  surrounded  by  a  circular  mucous  fold  {ampulla  of  Vafer),  which  is 
usually  very  prominent,  and  acts  as  a  valve  in  preventing  the  entrance  of 
alimentary  substances  into  the  apertures  it  encircles ;  this  office  it  fills  so 
well,  tliat  it  will  not  even  allow  the  aii-  with  which  the  duodenum  is  inflated 
to  pass  mto  the  ducts. 


Fig.  216. 


EXCRETORY   APPARATUS   OF   THE   HORSE'S   LIVER. 

1,  Left  lobe  of  the  liver;  2,  Middle  lobe;  3,  Right  lobe;  4,  Lobule  of  Spi^rel ;  6, 
Posterior  vena  cava  at  its  entrance  into  the  liver ;  7,  Vena  porta; ;  8,  Ductus 
oholedochus  ;  9,  Pancreatic  duct ;  10,  Common  entrance  of  these  two  ducts  into 
the  small  mtestine. 

There  enter  into  the  structure  of  the  ductus  choledochus:  1,  A  fibrous 
membrane,  which  some  anatomists  believe  contains  unstriped  muscular 
fibres ;  2,  Cylindrical  epitJieUum;  3,  Numerous  racemose  glands,  opening  on  its 
inner  surface  by  very  small  orifices. 

Vessels  and  Nerves  of  the  Liver.— The  blood-vessels  are  the  hepatic 
artery,  portal  vein,  and  suprahepatic  veins. 

The  liepatic  artenj  is  a  branch  of  the  coeliac,  and  enters  the  gland  by  the 
posterior  fissure,  in  company  with  the  portal  vein  and  ductus  choledochus. 
In  the  liver  it  divides  into  very  fine  ramifications  which  join  the  intra- 
lobular plexus,  anastomose  on  the  surface  of  the  biliary  ducts,  or  expand 
either  on  the  serous  membrane,  or  in  the  walls  of  the  portal  vein. 

The  portal  vein  is  the  functional  vessel  of  the  liver.  It  reaches  that 
organ  by  the  posterior  fissure,  and  Glisson's  capsule  accompanies  its  rami- 
fications as  far  as  the  hepatic  lobules,  where  they  form  the  plexus  of  sub- 
hepatic veins. 

The  suprahepatic  (or  sublobular)  veins  are  so  named  because  they  gain 
the  antero-superior  face  of  the  viscus  to  open  into  the  posterior  vena  cava. 
They  carry  away  the  blood  that  has  been  brought  by  the  portal  vein  and 
hepatic  artery.  Their  origin  is  due  to  the  union  of  the  intralobular  veins, 
which  make  a  passage  through  the  hepatic  tissue  with  which  their  walls  are 
immediately  m  contact,  gradually  join  each  other,  and  enter  the  posterior 
vena  cava  on  its  way  through  the  anterior  fissure  of  the  liver.  The  number 
of  trunks  (hepatic)  entering  this  vessel  is  considerable,  but  the  majority  are 
very  small ;  the  principal  confluent  is  placed  at  the  anterior  extremity  of 
the  fissure. 

The  lymphatics  form  a  fine  superficial  plexus,  easy  to  inject ;  with  deeper 


426  TEE  DIGESTIVE  APPARATUS  IlS  MAMMALIA. 

networks  placed  around  tlie  vessels  that  penetrate  by  the  posterior  fissure. 
In  the  lobules  they  are  disposed  as  described  above.  Joined  to  the 
lymphatics  of  the  stomach,  they  constitute  a  single  trunk  that  goes  to  the 
sublumbar  receptacle. 

The  nerves  are  more  particularly  derived  from  the  solar  plexus,  although 
the  pneumogastric  and  diaphragmatic  also  supply  filaments  to  the  liver. 
They  interlace  around  the  hepatic  artery  and  portal  vein ;  their  mode  of 
termination  is  unknown. 

Functions. — The  most  important  considerations  are  attached  to  the  study 
of  the  functions  of  the  liver ;  but  we  cannot  enter  into  them  in  detail  with- 
out going  beyond  our  subject.  Besides,  there  is  yet  much  to  be  learned 
respecting  them. 

The  liver  is  a  biliary  and  glycogenetic  gland.  It  secretes  the  bile  at  the 
expense  of  the  blood  of  the  portal  vein,  which  comes  from  the  intestinal 
tunics  charged  with  the  assimilable  substances  absorbed  by  the  veins  from 
the  villi.  This  fluid  is  submitted  to  modifications  in  the  interior  of  the 
liver,  by  which  it  is  relieved  of  certain  matters,  while  at  the  same  time  it 
furnishes  the  biliary  secretion. 

The  bile  is,  therefore,  in  this  respect  an  excrementitious  secretion ;  though 
all  its  elements  are  not  thrown  off,  some  of  them  acting  on  the  alimentary 
substances,  and  others  being  absorbed.  From  the  most  recent  researches, 
it  would  appear  that  it  has  a  share  in  the  purification  of  the  blood,  in 
digestion,  and  in  calorification ;  in  the  latter  especially,  as  its  absorbed 
elements  are  very  rich  in  carbon  and  hydrogen,  bodies  eminently  adapted 
for  the  production  of  animal  heat. 

The  liver  is  also  a  glycogenetic  gland,  this  function  having  been  demon- 
strated to  pertain  to  it  by  Bernard.  The  sugar  formed  in  the  liver  finds 
its  way  into  the  blood,  and  leaves  the  organ  by  the  suprahepatic  veins.  It 
is  elaborated  in  the  hepatic  cells  by  the  transformation  of  the  substance 
known  as  "animal  amidon,"  which  is  brought  into  contact  with  a  kind  of 
diastase  that  exists  with  it  in  their  interior. 

Lastly,  it  is  also  believed  that  the  liver  is  a  hcematogenetic  organ,  the  red 
globules  being  formed  in  its  mass  at  the  expense  of  the  fibrine  of  the  blood 
that  passes  through  it. 

It  will  thus  be  seen  that  the  liver  furnishes  two  very  different  products- 
bile  and  sugar.  The  knowledge  of  this  fact,  combined  with  the  internal 
arrangement  of  the  organ,  has  led  some  anatomists  to  consider  the  organ  as 
two  glands  reciprocally  contained  within  each  other.  But  this  hypothesis 
loses  its  value  if  it  be  admitted  that  the  hepatic  ducts  pass  between  the  cells 
to  the  centre  of  the  lobule,  and  that  in  this  portion  they  are  destitute  of 
epithelium.  It  is  therefore  probable  that  the  sugar  and  bile  are  produced 
in  the  large  hepatic  cells,  and  that  the  first  passes  into  the  veins,  while  the 
second  is  poured  into  the  biliary  ducts. 

In  Solipeds,  the  secretion  of  bile,  though  most  active  during  the  digestive 
period,  yet  goes  on  in  a  continuous  manner. 

(Certain  deductions  of  a  pathological  kind  are  based  upon  the  foregoing 
anatomical  facts,  and  have  an  important  bearing  with  regard  to  comparative 
pathology.  They  have  been  pointed  out  by  Wilson,  and  are  as  follows  : — 
Each  lobule  is  a  perfect  gland  ;  its  structure  and  colom-  are  uniform,  and 
it  has  the  same  degree  of  vasciilarity  throughout.  It  is  the  seat  of  a  double 
venous  circulation  ;  the  vessels  of  the  one  (Jiepatic)  being  situated  in  the 
centre  of  the  lobule,  and  those  of  the  other  {portal)  in  the  circumference. 
Now  the  colour  of  the  lobule,  as  of  the  entire  liver,  depends  chiefly  on  the 


OBGANS  AXXEXED  TO  THE  ABDOMINAL  DIGESTIVE  CAXAL.     427 

proportion  of  blood  contained  within  these  two  sets  of  vessels ;  and  so  long 
as  the  circulation  is  natural,  the  colour  will  be  uniform.  But  the  instant 
that  any  cause  is  developed  which  shall  interfere  with  the  free  circuhi- 
tion  of  either,  there  will  be  an  immediate  diversity  in  the  colour  of  the 
lobule. 

Thus,  if  there  be  any  impediment  to  the  free  circulation  of  the  venous 
blood  through  the  heart  or  lungs,  the  circulation  in  the  hepatic  veins  will. 
be  retai-ded,  and  the  sublobular  (or  supralubularj  and  intralobular  veius 
will  become  congested,  giving  rise  to  a  more  or  less  extensive  redness  in  the 
centre  of  each  of  the  lobules;  while  the  marginal  or  non-congested  portion 
presents  a  distinct  border  of  a  yellowish  white,  yellow,  or  green  colour, 
according  to  the  quantity  or  quality  of  the  bile  it  may  contain.  ■'  This  is 
^passive  conrjestion'  of  the  liver,  the  usual  and  natural  state  of  the  organ 
after  death ;"  and,  as  it  commences  «-ith  the  hepatic  vein,  it  may  be  called 
the  first  stage  of  hepatic  venous  congestion. 

But  if  the  causes  which  produced  this  state  of  congestion  continue,  or  be 
from  the  beginning  of  a  more  active  kind,  the  congestion  will  extend  through 
the  lubular  venous  plexuses  "  into  those  branches  of  the  portal  vein  situated 
in  the  interlobular  jissures,  but  not  to  those  in  the  spaces,  which  being  larger, 
and  giving  origin  to  those  in  the  fissures,  are  the  last  to  be  congested.''  In 
this  second  stage  the  liver  has  a  mottled  appearance,  the  non-congested 
substance  is  arranged  in  isolated,  circular,  and  ramose  patclies,  in  the 
centres  of  which  the  spaces  and  parts  of  the  fissure  are  seen.  This  is  an 
extended  degree  of  hepatic  venous  congestion  ;  it  is  "  active  congestion  "  of  the 
liver,  and  very  commonly  attends  disease  of  the  heai't  and  lungs. 

These  are  instances  of  partial  congestion  ;  but  there  is  sometimes  general 
congestion  of  the  organ.  "In  general  congestion  the  whole  liver  is  of  a  red 
colour,  but  the  central  portions  of  the  lobules  are  usually  of  a  deeper  hue 
than  the  marginal  portions.") 

Development — The  liver  of  the  foetus  is  remarkable  for  its  enormous 
development.  Its  function  commences  early,  for  at  birth  the  intestines  are 
filled  with  meconium,  a  product  of  the  biliary  secretion.  A  more  detailed 
description  will  be  given  when  the  general  development  of  the  foetus  comes 
to  be  studied. 

2.  The  Pancreas. 

This  organ  has  the  greatest  resemblance  to  the  salivary  glands  in  its 
structure  and  physical  properties  ;  and  for  this  reason  it  has  been  named  the 
abdominal  salivary  gland. 

Situation. — It  is  situated,  in  the  sublumbar  region,  across  the  aorta  and 
posterior  vena  cava,  in  front  of  the  kidneys,  and  behind  the  liver  and 
stomach.     Its  weight  is  seventeen  ounces. 

Form  and  Belations. — The  pancreas  is  rather  irregular  and  variable  in 
form,  according  to  the  kind  of  animal.  Flattened  from  above  to  below, 
traversed  obliquely  from  its  inferior  to  its  superior  face  by  an  opening  for 
the  passage  of  the  portal  vein,  and  which  is  named  the  pancreatic  ring,  this 
gland  is  sometimes  triangidar,  sometimes  oblong,  and  curved  on  itself :  it  is 
under  the  latter  form  that  we  will  notice  it. 

It5  faces  present  the  lobulated  aspect  of  salivary  glands.  The  superior 
adheres  by  cellular  tissue  to  the  aorta,  posterior  vena  cava,  coeliac  trunk, 
solar  plexus,  splenic  vessels,  and  the  right  kidney  and  supra  renal  capsule ; 
it  is  covered  by  the  peritoneum  for  a  certain  portion  of  its  extent.  The 
inferior  responds  to  the  base  of  the  cfecum  and  the  foiu'th  portion  of  the 


428  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

colon,  througli  the  medium  of  a  thick  layer  of  cellular  tissue.  The  anterior 
border,  concave  and  undulating,  is  in  contact  with  the  duodenum  and  the  left 
extremity  of  the  stomach.  The  posterior  is  very  convex,  especially  to  the 
right,  and  near  its  middle  jiresents  a  notch  for  the  reception  of  the  portal 
vein  before  its  entrance  into  the  ring.  The  right  extremity  (or  head),  the 
thinnest,  adheres  to  the  duodenum,  and  shows  the  excretory  ducts  of  the 
gland.  The  left  is  carried  towards  the  base  of  the  spleen,  in  passing 
between  the  left  extremity  of  the  stomach  and  the  kidney  of  the  same 
side. 

Structure. — It  resembles  the  salivary  glands,  except  in  its  epithelium. 
This,  instead  of  being  simple  polygonal  cells  lining  the  thin,  structureless 
membrane  of  the  ultimate  follicles,  is  very  granular,  and  fills  these  cavities. 
The  gland  receives  its  blood  by  the  hepatic  and  great  mesenteric  arteries ; 
the  nerves  come  from  the  solar  plexus. 

Excretory  apparatus. — The  liaucreas  has  two  excretory  ducts  :  a  principal, 
described  by  Wirsung,  whose  name  it  bears,  and  an  accessory.  The  duct  of 
Wirsung,  lodged  in  the  substance  of  the  gland,  but  nearer  the  superior  than 
the  inferior  face,  at  first  comprises  two  or  three  thick  branches,  which  soon 
unite  to  form  a  single  trunk  that  emerges  from  the  pancreas  by  the  left 
extremity  of  the  organ.  Larger  than  the  ductus  choledochus,  it  opens,  as 
already  stated,  at  the  same  part  of  the  duodenal  surface.  The  accessory 
duct  (ductus  pancreaticus  minor)  is  much  smaller ;  it  leaves  the  principal 
trunk,  receives  some  branches  in  its  passage,  and  opens  alone  into  the  small 
intestine,  directly  opposite  the  duct  of  Wirsung. 

The  ductus  choledochus  and  the  duct  of  Wirsung  do  not  pass  directly 
through  the  wall  of  the  intestine,  but  obliquely,  like  the  entrance  of  the 
ureters  into  the  bladder.  They  open  in  the  middle  of  a  circular  valve — the 
ampulla  of  Vater.  This  ampulla  is  limited  by  a  thick  primary  mucous 
fold,  and  within  this  is  a  second,  thinner,  beneath  which  the  ductus  chole- 
dochus opens ;  at  the  bottom  of  the  space  circumscribed  by  this  second  fold, 
beneath  a  free  mucous  lip,  is  seen  the  duct  of  Wirsung. 

Functions. — From  the  researches  of  Bernard,  it  appears  established  that 
the  fluid  secreted  by  the  pancreas  emulsifies  fatty  matters  and  renders  them 
absorbable. 

3.  The  Spleen. 

The  spleen  differs  from  glands  not  only  in  the  absence  of  an  excretory 
duct,  but  also  in  the  other  details  of  its  organisation.  It  has  been  consi- 
dered as  a  vascular  gland,  whose  uses  are  not  yet  determined  in  a  precise 
manner. 

Situation. — It  is  situated  in  the  diaphragmatic  region,  close  to  the  left 
hypochondriac,  and  appears  as  if  suspended  in  the  sublumbar  region,  as  well 
as  at  the  great  curvature  of  the  stomach. 

Form — Direction — Relations.— The  spleen  is  falciform,  and  directed 
obliquely  downwards  and  backwards.  It  has  two  faces,  two  borders,  and  a 
point. 

The  external  face  is  in  relation  with  the  muscular  portion  of  the 
diaphragm,  and  is  moulded  to  it.  The  internal,  slightly  concave,  touches 
the  large  colon ;  it  has  sometimes  a  small  lobule,  or  offers  traces  of  lobula- 
tion. The  posterior  border  is  convex,  thin  and  sharp.  The  anterior,  thicker, 
concave,  and  bevelled  at  the  expense  of  tlie  internal  face,  is  channeled  by  a 
slight  longitudinal  fissure  which  lodges  the  splenic  vessels  and  nerves  ;  it 


OBGANS  ANNEXED  TO  TEE  ABDOMINAL  DIGESTIVE  CANAL.     429 

receives  the  insertion  of  the  great  mesentery,  by  which  it  is  held  to  the 
greater  curvature  of  the  stomach.  The  base,  or  superior  ex-fremity,  is  thick 
and  wide,  and  responds  to  the  left  kidney  and  the  corresponding  extremity 
of  the  pancreas ;  it  shows  the  insertion  of  the  susjjensory  ligament.  The 
point,  or  inferior  extremity,  is  smooth  and  thin. 

Weight. — The  average  weight  is  32  ounces  ;  but  it  is  sometimes  of 
enormous  dimensions — as  much  as  three  or  fom*  times  its  normal  volume. 

Mode  of  attachment. — The  sjdeen  is  a  floating  organ,  whose  displacements 
are  limited  by  a  suspensory  ligament,  and  the  great  (or  gastro-splenic) 
omentum.  The  first  is  a  peritoneal  fold  which  proceeds  from  the  anterior 
border  of  the  left  kidney  and  the  sublumbar  wall,  and  is  strengthened  by 
the  elastic  fibrous  tissue  comprised  between  its  two  layers.  It  is  fixed  to 
the  base  of  the  spleen,  and  is  confounded,  inwardly,  with  the  great  omentum. 
The  latter  is  already  known  as  proceeding  to  the  colon,  and  in  its  passage 
becoming  attached  to  the  splenic  fissure,  whence  it  extends  over  the  sur- 
face of  the  organ  to  form  its  serous  covering. 

Structure. — The  tissue  of  the  spleen  has  a  violet-blue  coloiu-,  sometimes 
approaching  to  a  red  hue ;  it  is  elastic,  tenacious,  and  soft,  yields  to  the 
pressure  of  the  finger,  and  retains  the  imprint.  Enveloped  externally  by  the 
peritoneum,  its  substance  includes  a  fibrous  frameicork,  splenic  pulp,  Mal- 
pighian  corpuscles,  vessels,  and  nerves. 

Serous  membrane. — This  is  developed  over  the  whole  surface  of  theor^an, 
except  in  the  fissui'e  of  the  anterior  border  Its  internal  face  adheres  most 
intimately  to  the  proper  tunic  of  the  spleen.  It  is  only  an  expansion  of  the 
serous  bands  which  limit  the  movements  of  the  viscus. 

Fibrous  frameicorli. — Under  the  peritoneal  membrane  is  a  thick,  resisting, 
fibrous  timic,  roughened  and  granular  on  its  exterior,  and  sending  from  its 
deep  face  into  the  interior  of  the  mass  a  multitude  of  prolongations  called 
trabeculce,  which  cross  in  all  directions,  forming  a  cellular  network  whose 
numerous  narrow  meshes  contain  the  other  elements  of  the  organ.  In 
washing  a  morsel  of  spleen  in  a  jet  of  water,  the  latter  are  removed,  and  the 
outlines  of  this  fibrous  structure  are  fully  exposed.  If  a  stream  of  water  is 
passed  through  the  splenic  artery,  the  same  result  will  be  arrived  at. 
Kolliker  has  found  in  the  proper  tunic  of  the  spleen,  and  in  its  trabeculfe, 
a  particular  contractile  tissue,  the  muscular  cell-fibres,  mixed  with  fasciculi 
of  elastic  or  inelastic  fibrous  tissue.  (The  proper  coat,  the  sheaths  of  the 
vessels,  and  the  trabeculfe  consist  of  a  dense  mesh  of  white  and  yellow 
elastic  fibrous  tissues,  the  latter  considerably  predominating.  It  is  owing  to 
the  presence  of  this  tissue  that  the  spleen  possesses  a  considerable  amount  of 
elasticity,  admirably  adapted  for  the  very  great  variations  in  size  that  it 
presents  imder  certain  circumstances.  In  some  of  the  mammalia,  in 
addition  to  the  usual  constituents  of  this  tunic,  are  found  numerous  pale, 
flattened,  spindle-shaped  nucleated  fibres,  like  imstriped  muscular  fibre. 
It  is  probably  owing  to  this  structure,  that  the  sjdeen  possesses,  when  acted 
upon  by  the  galvanic  current,  faint  traces  of  contractility.) 

Spjlenic  pulp. — This  name  is  given  to  a  reddish  pultaceous  material, 
which  partly  occupies  the  aveolar  framework  formed  by  the  intersections 
of  the  trabeculfe.  It  is  sustained  by  a  very  delicate  reticulum  of  connective 
tissue,  and  is  composed  of  numerous  elements,  such  as  pigment  granules, 
free  nuclei,  large  cells  with  several  nuclei,  lymphoid  elements,  and  blood- 
globules  in  a  state  of  decomposition  or  transfoi-mation.  These  globules 
are  free  or  enveloped  in  an  albuminoid  membrane.  (The  proper  substance 
of  the  spleen  consists  of  coloured  and  colourless  elements.     The  coloured 


430 


THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 


Fis.  217. 


are  composed  of  red  blood-globules  and  coloured  corjjuscles,  either  free  or 
included  in  cells.     Sometimes  unchanged  blood-discs  are  seen  included  in 

a  cell ;  but  more  frequently  the 
included  blood-discs  are  altered 
both  in  form  and  colour.  Besides 
these,  numerous  deep-red,  or  red- 
dish-yellow, or  black  corpuscles 
and  crystals,  either  single  or  aggre- 
gated in  masses,  are  seen  diffused 
throughout  the  pulp  substance ; 
these,  in  chemical  composition, 
are  closely  allied  to  the  hsematine 
of  the  blood.  The  colourless  ele- 
ments consist  of  granular  matter; 
nuclei,  about  the  size  of  the  red 
blood-discs,  homogeneous  or  gra- 
nular in  structure ;  and  nucleated 
vesicles  in  small  numbers.  These 
elements  form  a  large  proportion  of 
the  entire  bulk  of  the  si^leen  in  well- 
nourished  animals ;  whilst  they 
diminish  in  number,  and  occasion- 
ally are  not  found  at  all,  in  starved 
animals.  The  a2ii:)lication  of  chemi- 
cal tests  shows  that  they  are  essen- 
tially a  proteine  compound.) 

Maljnghian  corpuscles, — These 
are  ccmtained,  like  the  pulp,  in  the  meshes  of  the  fibrous  framework,  and  are 
enveloped  by  this  pulp.  Scattered  along  the  track  of  the  small  arteries, 
these  corpuscles  are  visible  to  the  naked  eye,  and  appear  as  whitish  closed 
sacs,  cells,  and  nuclei  floating  in  a  plasma.  The 
Malpighian  corpuscles  are  constituted  by  the  adven- 
titious tunic  of  the  arteries,  in  which  lymphoid  ele- 
ments are  accumulated  at  certain  points.  They 
are  therefore  allied  to  the  closed  follicles  of  the 
intestines,  (These  splenic  or  Malpighian  corpuscles, 
are  round,,  whitish,  semi-opaque  bodies,  glutinous 
in  consistence,  and  disseminated  throughout  the  sub- 
stance of  the  organ.  They  are  more  distinct  in 
early  than  in  adult  life  or  old  age,  and  vary  con- 
siderably in  size  and  number,  From  the  manner 
CLE,  FROM  THE  SPLEEN  vo.  whicli  they  are  appended  to  the  sheaths  of  the 
OF  THE  ox.  smaller  arteries  and   their  branches,  they  resemble 

1,  External  tunic,  or  mem-  the  buds  of  the  moss-rose.  Each  consists  of  a  mem- 
brana  propria ,  2  Gran-  branous  capsule,  composed  of  fine  pale  fibres  inter- 
uiar  contents:   o,  Part    ■,      .         •         n     t        ,•  mi      i  i       i  i  -t 

of  a  small  artery  •  4  lacmg  in  all  directions,  i  he  blood-vessels  ramiiy 
Its  sheath,  derived  from  ing  on  the  surface  of  the  corpuscles,  are  the  larger 
the  external  tunic  of  the  ramifications  of  the  arteries  to  which  the  sacculus 
spleen,  with  which  the  jg  connected,  and  also  of  a  delicate  capillary  plexus, 
necSr^' ''  "'''     ^"^"l^i"  *"  t^^*^*    surrounding    the    vesicles    of  other 

glands.  These  vesicles  have  also  a  close  relation 
with  the  veins,  and  the  vessels  begin  on  the  surface  of  each  vesicle  through- 
out the  whole  of  its  circumference,  forming  a  dense  venous  mesh  in  which 


BRANCH  OF  SPLENIC  ARTERY  WITH  ITS  RAMI- 
FICATIONS STUDDED  WITH  MALPIGHIAN  COR- 
PUSCLES, 


Fis,  218, 


A  SINGLE  SPLENIC  CORPUS- 


ORGANS  ANNEXED  TO  THE  ABDOMINAL  DIGESTIVE  GANAL.     431 

each  of  these  bodies  is  inclosed.  It  is  probable  that,  from  the  blood  con- 
tained in  the  capillary  network,  the  material  is  sepai'ated  which  is  occa- 
sionally stored  up  in  their  cavity ;  the  veins  being  so  placed  as  to  carry 
off,  under  certain  conditions,  those  contents  that  are  again  to  be  dis- 
cbarced  into  the  circulation.  Each  capsule  contains  a  soft,  white,  semi-fluid 
substance,  consisting  of  granular  matter,  nuclei  similar  to  those  found  in  tlie 
pulp,  and  a  few  nucleated  cells,  the  composition  of  which  is  apparently 
albuminous.  These  bodies  are  very  large,  after  the  early  periods  of  diges- 
tion, in  well-fed  animals,  and  especially  those  fed  upon  albuminous  diet. 
In  starved  animals,  they  disapj^ear  altogether.) 

Arteries. — These  emanate  from  the  splenic  artery  at  different  elevations, 
and  plunge  into  the  tissue  of  the  spleen,  preserving  their  reciprocal 
independence.  Their  terminal  ramifications  do  not  open,  as  has  been 
said,  into  venous  sinuses,  but  into  minute  tufts  of  capillaries,  wLich  traverse 
the  splenic  pulp,  to  be  continued  by  the  venous  network. 

Veins. — All  the  venous  branches  of  the  spleen  open  into  the  splenic 
vein,  and  are  lodged  with  the  corresponding  artery  in  the  fissure  of  the 
organ.  Traced  from  their  commmencement,  they  are  seen  to  gradually  lose 
their  constituent  membranes,  and  to  open  into  sinuses  which  are  only  lined 
by  the  epithelium  of  the  vessels.  It  is  in  these  sinuses  that  the  network 
of  venous  capillaries  which  succeed  the  arterial  capillaries,  originates. 

Lymphatic  vessels. — These  are  found  on  the  external  surface  of  the 
organ,  and  along  the  track  of  the  blood-vessels.  (They  invest  these  with 
a  distinct  sheath,  between  which  and  the  parietes  of  the  vessels  numerous 
lymph  corpuscles  may  be  fomid.) 

Nerves. — They  are  derived  from  the  solar  plexus,  and  enveloping  the 
splenic  artery,  with  it  enter  the  spleen.  (They  appear  to  be  very  large, 
but  this  appearance  is  due  to  the  great  proportion  of  ordinary  fibrous  tissue 
investing  them.) 

From  what  has  been  said  above  respecting  the  arrangement  of  the 
splenic  arteries  and  veins,  it  will  be  perceived  that  the  areolfe  formed  by 
the  trabecidae  of  the  fibrous  framework  contain  the  pulp,  and  are  not  in 
direct  communication  with  the  arterial  capillaries.  Such  an  organisation 
belongs  to  erectile  tissues.  The  arteries  communicate  with  the  veins  proper 
by  venous  canals  channeled  in  the  splenic  pulp,  and  are  lined  only  by  ellip- 
tical cells.  These  venous  canals  are  extremely  dilatable,  especially  in 
the  Horse.  When  the  splenic  vein  is  inflated,  their  walls  separate  and 
press  back  the  pulp,  they  become  considerably  enlarged,  and  distend 
the  cells  of  the  fibrous  structm-e,  but  the  air  does  not  reach  the  interior 
of  these  cells. 

FcN'CTioys. — Nothing  precise  is  known  regarding  the  functions  of  the 
spleen  :  though  they  must  be  of  very  secondary  importance,  because  animals 
in  which  the  organ  has  been  extirpated,  and  which  have  recovered  from  the 
consequences  of  the  operation,  have  continued  to  live  in  apparent  good 
health.  Numerous  hypotheses  have  been  formed  on  this  subject ,  two  of 
which,  foimded  on  the  study  of  the  anatomical  peculiai'ities  of  the  spleen 
tissue,  and  on  exact  physiological  observations,  are  as  follows :  1,  The  spleen 
is  a  diverticidura  for  the  portal  vein  ;  2,  The  red  globules  are  destroyed  in  the 
spleen. 

With  regard  to  the  first  hypothesis,  it  is  evident  that,  owing  to  the 
presence  of  the  venous  sinuses  already  mentioned,  and  their  great  dilata- 
bility,  as  well  as  to  the  elasticity  and  contractility  of  the  spleen  tissue,  the 
organ  is  favourably  constructed  to  act  as  a  blood  reservoir-.     M.  Goubaux, 


432  THE  DIGESTIVE  APPARATUS  IN  MAMMALIA. 

on  the  other  hand,  has  demonstrated  that  there  is  always  an  augmentation 
in  the  spleen's  volume  when  an  animal  has  ingested  large  quantities  of 
water,  the  consecutive  absorption  of  which  determines  a  certain  tension  in 
the  portal  venous  system. 

The  second  opinion,  emitted  by  Kolliker,  is  founded  on  the  existence 
in  the  splenic  pulp  of  blood-globules  in  a  state  of  decomposition,  and 
in  the  analyses  made  by  J.  Beclard  of  the  blood  in  the  splenic  vein, 
which  have  proved  that  there  is  a  notable  diminution  in  the  proportion  of 
globules. 

It  is  to  be  remarked  that,  in  the  researches  undertaken  to  discover 
the  functions  of  the  spleen,  account  has  not  been  taken  of  the  connections 
existing  between  this  organ  and  the  great  omentum  in  the  majority  of 
mammals,  and  which  testify  that  the  spleen  is  only,  properly  speaking, 
a  vascular  appendage  placed  on  the  track  of  this  omentum.  But  the  uses 
of  this  vast  peritoneal  fold  are  themselves  little  understood.  Might  they 
not  be  included  with  those  which  are  presumed  to  belong  to  its  appended 
organ  '^ 

DIFFERENTIAL   CHARACTERS   IN   THE   ANNEXED   ORGANS   IN   THE   ABDOMINAL   PORTION   OF 
THE   DIGESTIVE   CANAL   IN   OTHER   THAN   SOLIPED  ANIMALS. 

The  important  differences  these  organs  offer  in  the  domesticated  mammals  belong 
more  particularly  to  the  liver. 

1.  Liver. — In  the  domesticated  mammals  other  than  Solipeds,  the  liver  exhibits  vari- 
ations in  form,  volume,  and  position,  which  have  no  influence  on  its  organisation  :  so  tliat 
the  study  of  these  possesses  but  a  mediocre  attraction.  This  is  not  so,  however,  with  re- 
gard to  the  excretory  apparatus,  the  arrangement  of  which  is  complicated,  and  becomes 
very  interesting.  The  biliary  duct,  in  fact,  on  leaving  the  fissure  of  the  portal  vein,  and 
before  reaching  the  intestine,  gives  rise  to  a  particular  conduit  which  is  detached  at  an 
acute  angle,  and  which,  after  a  course  of  variable  length,  according  to  the  size  of  the 
animal,  becomes  dilated  into  a  vast  sac,  the  so-called  gall-hladder. 

In  all  treatises  on  anatomy,  the  special  conduit  is  designated  the  cystic  duct,  that 
portion  which  precedes  its  origin  being  named  the  hepatic  duct ;  while  the  appellation  of 
ductus  communis  choledochus  is  reserved  for  the  section  which  goes  to  the  intestine.  But 
these  distinctions  are  vicious,  and  we  limit  ourselves  to  the  recognition  of :  ( a)  A  ductus 
choledochus  exactly  like  that  of  Solijjeds,  and  like  it  extending  from  the  posterior 
fissure,  where  it  originates  by  the  union  of  several  branches,  to  the  duodenum ;  and  {b)  a 
cystic  duct,  which  branches  suddenly  into  the  choledic  duct,  and  terminates  in  the  gall- 
bladder. 

a.  The  gall-hladder  is  a  reservoir  with  membranous  walls,  in  which  the  bile  accumu- 
lates during  the  intervals  of  digestion.  This  sac,  lodged  wholly,  or  in  part,  in  a  fossa  on 
the  posterior  face  of  the  liver,  is  oval  or  pyriform,  and  presents  a  fundus  and  nech.  Its 
parietes  comprise  three  tunics  :  an  external,  of  peritoneum  :  a  middle,  formed  of  dartoid 
tissue  ;  and  an  internal,  or  mucous,  continuous  with  that  of  the  various  biliary  ducts. 

b.  The  cystic  duct  extends  in  a  straight  line  from  the  neck  of  the  gall-bladder  to  the 
choleilic  duct.  It  adheres  intimately  to  the  tissue  of  the  liver,  and  does  not  exhibit,  in- 
ternally, the  spiral  valves  which  have  been  described  in  Man.  In  opening  it  longitudi- 
nally, there  ai-e  discovered,  at  least  in  Ruminants  and  the  Camivora,  very  small  orifices 
which  pierce  the  wall  adherent  to  the  tissue  of  the  liver :  these  are  the  openings  of 
several  minute  but  particular  biliary  canals,  named  the  hepatico-cystic  ducts. 

c.  The  ductus  communis  choledochus  comports  itself  exactly  as  in  Solipeds.  It  is 
much  wider  than  the  cystic  duct,  and  opens  sometimes  alone,  sometimes  with  the  pan- 
creatic canal,  into  the  duodenum  in  a  manner  which,  up  to  a  certain  point,  reminds  one 
of  the  mode  of  termination  of  the  ureters.  Instead  of  passing  perpendicularly  across  the 
intestinal  parietes,  it  first  pierces  the  muscular  layer,  follows  for  a  short  distance  between 
it  and  the  mucous  membrane,  and  then  opens  on  the  internal  face  of  the  latter  by  an 
orifice  which  is  encircled  by  a  valvular  fold,  as  in  the  Horse. 

Such  is  the  excretory  apparatus  belonging  to  the  liver  in  animals  provided  with 
a  gall-bladder.  In  these  animals  the  biliary  secretion  is  certainly  continuous,  as 
in  the  Horse ;  but  in  the  intervals  of  digestion  the  bile,  instead  of  flowing  directly  on 
to  the  intestinal  surface,  passes  into  the  gall-bladder  by  the  cystic  duct,  and  there 


OBGANS  ANNEXED  TO  TEE  ABDOMINAL  DIGESTIVE  CANAL.      433 

accumulates.  When  digestion  commences  again,  this  reserve  of  bile  is  thrown  into  the 
ductus  choledochus  by  the  contraction  of  the  muscular  fibres  of  the  cyst,  and  by  the 
pressure  of  the  abdominal  viscera ;  it  meets  that  which  comes  directly  from  the  liver, 
and  with  it  is  carried  to  the  duodenum. 

We  will  now  glance  at  the  particular  arrangement  of  this  viscus  in  each  species. 

In  the  Ox,  the  liver  is  entirely  confined  to  the  right  diaphragmatic  region.  It  is 
thick,  vohuninous,  and  scarcely  notched  at  its  peripheiy  ;  so  that  it  is  difficult,  if  not 
impossible,  to  distinguish  three  lobes  in  it,  the  lobus  Spigelii  alone  being  detached  from 
the  mass  of  the  organ.  The  gall-bladder,  fixed  towards  the  superior  extremity,  is  nearly 
always  floating ;  near  its  neck  it  receives  the  insertion  of  several  large  conduits,  which 
come  directly  from  the  up^jer  part  of  the  liver.     The  ductus  choledochus  opens  alone  at 

Fis,  219. 


LIVER   OP   THE   DOG,    WITH    ITS   EXCRETORY   APPARATUS. 

D,  Duodenum  and  the  intestinal  mass;  p.  Pancreas;  r,  Spleen;  e,  Stomach;  /, 
Rectum;  R,  Right  kidney;  B,  Gall-bladder;  ch,  Cystic  duct;  ff.  Liver;  f'.  Lobe 
of  the  liver,  prepared  to  show  the  distribution  of  the  vena  porta;  and  hepatic 
vein ;  VP,  Vena  portse ;  Vh,  Hepatic  vein ;  d,  Diaphragm ;  VC,  Vena  cava  • 
C,  Heart. 

a  great  distance  from  the  pylorus ;  M.  Colin  has  found  it  to  be  24i  inches  in  one  cow, 
and  29^  inches  in  another.  In  the  Sheejj  and  Goat,  the  form  and  position  of  the  liver 
diflera  but  little  from  that  of  the  Ox.  The  ductus  choledochus,  however,  imites  with 
that  of  the  pancreas,  and  terminates  at  12  to  16  inches  from  the  pylorus. 

In  the  Pig,  the  liver  has  three  well-marked  lobes ;  the  middle  carries  the  gall- 
bladder.    The  ductus  choledochus  opens  alone  at  1  or  1 J  inches  only  from  the  pylorus. 

In  the  Dog  and  Cat,  the  liver  is  very  voluminous,  is  deeply  notched,  nnd  is  divided 
into  five  principal  lobes.  The  middle  lube  has  the  gull-bladder  attached  to  it,  and  gives 
it  complete  lodgment  in  a  fossa. 


434 


TEE  DIGESTIVE  APPABATUS  IN  MAMMALIA. 


In  the  Dog,  the  ductus  choledochus,  joined  to  a  small  branch  from  the  pancreatic  duct, 
enters  the  intestine  at  a  variable  distance  from  the  pylorus,  depending  upon  the  size  of 
the  animal,  but  usually  between  1^  and  4f  inches.  In  the  portion  comprised  between 
tlie  intestine  and  the  origin  of  the  cystic  duct,  it  receives  several  biliary  canals  of  some- 
what considerable  diameter.  In  the  Cat,  the  ductus  choledochus  is  most  frequently 
inserted  from  about  1  to  l^  inches  from  the  pyloric  orifice  ;  it  opens  immediately  along- 
side the  pancreatic  duct  when  it  does  not  join  it. 

2.  Pancreas. — In  the  Ox.  the  pancreas  is  not  placed  across  the  sublumbar  parietes, 
but  is  comprised  between  the  layers  of  the  mesentery,  to  the  right  of  tlie  great  mesenteric 
artery.  The  excretory  duct  is  single,  and  opens  into  the  small  intestine  at  from  14  to  16 
inches  beyond  the  ductus  choledochus. 

In  the  Sheep  and  Goat,  there  is  the  same  general  arrangement,  but  the  excretory 
duct  opens  with  that  of  the  liver. 

In  the  Pig,  this  duct  is  inserted  at  from  4  to  6  inches  behind  the  ductus  choledochus. 

The  pancreas  of  the  Dog  is  extremely  elongated,  and  included  between  the  layers  of 
the  mesentery  which  sust;iin  the  duodenum.  It  is  curved  at  its  anterior  extremity, 
behind  the  stomach,  to  one  side  of  the  median  line.  Its  excretory  du't,  usually  single, 
pierces  the  intestinal  membranes  2  inches  beyond  the  hepatic  duct  (Fig.  219,  m).  Except 
in  the  mode  of  insertion  of  the  excretory  duct,  which  has  been  described  in  noticing  the 
ductus  choledochus,  the  pancreas  of  the  .Cat  comports  itself  exactly  like  that  of  the  Dog. 

3.  Spleen. — In  Ruminants,  the  spleen  is  nut  supported  by  the  great  omentum,  but 
adlieres  to  the  left  side  of  the  rumen  and  diaphragm.  It  is  not  falciform,  and  its  breadth 
is  the  same  througliout  its  extent.  In  the  Carnivora,  it  is  suspended  to  the  great 
omentum  at  a  certain  distance  from  the  left  sac  of  the  stomach.  It  is  irregularly  falci- 
form, its  point  is  less  acute  than  in  Solipeds,  and  is  directed  upwards. 


COMPARISON   BETWEEN  THE   ANNEXED   ORGANS  OP   THE   ABDOMINAL   PORTION   OF   THE 
DIGESTIVE   CANAL   IN   MAN   AND   TBOSE   OF   ANIMALS. 

1.  Liver. — Like  that  of  Euminants,  the  human  liver  is  situated  in  the  right  excava- 
tion of  the  lower  face  of  the  diaphragm.  Its  direction  is  nearly  horizontal ;  its  shape  is 
oval,  and  its  average  weight  from  forty-nine  to  fifty-three  ounces.  The  posterior  border 
is  thick  and  round ;  the  anterior  border  and  extremities  thin  and  sharp.  The  upper 
lace,  which  in  expiration  asceuds  to  the  fourth  rib,  is  divided  nito  two  portions  or  lobes — 

right  antl    left,  by  the   falciform 
Fio-.  220.  ligament;  it  is  smooth  and  con- 

vex. The  inferior  fiice  has  three 
furrows,  or  fossae :  two  longitu- 
dinal, united  by  a  transverse,  re- 
sembling altogether  the  letter  H. 
The  transverse  furrow  represents 
that  on  the  posterior  aspect  of 
the  liver  of  animals,  and  its  des- 
tination is  the  same.  The  right 
long  tudinal  furrow  lodges  the 
obliterated  umbilical  vein ;  the 
left,  well  marked  before  and  be- 
hind, lodges  the  gall-bladder 
in  front,  and  the  inferior  vena 
cava  behind.  This  face  has  four 
lobes,  the  right  and  left,  and  two 
middle  lobes.  In  front  of  the 
''  transverse    furrow   is    the    lobus 

UNDER  SURFACE  OF  THE  HUMAN  LIVER.  quadratus,  and  behind  the  same 

1,   Right   lobe;   2,   Left   lobe;  3,   Lobus  quadratiis;  4,    fissure  is  the  lobus  Spigelii. 

Lobus   Spigelii :  5,  Lobus  caudatus  ;  6,  Longitudinal  On  the  lower  face  of  the  right 

fossa ;  7,  Pons  hepatis  ;  8,  Fossa  of  ductus  venosus  ;  lobe  are  three  depressions :  an 
9,  Inferior  vena  cava;  10,  Gall-bladder;  11,  Trans-  anterior  or  impressio  colica ;  a 
verse  fossa;  12,  Vena  cava;  13,  Depression  corres-  deep  middle  one,  impressio  vesicm  ; 
ponding  to  the  curve  of  the  colon;  14,  Double  and  a  small  posterior  one,  which 
depression  produced  by  right  kidney  and  supra-renal  receives  the  supra-renal  capsules, 
capsule.  impressio  renalis. 

2.  Pancreas. — This  organ  is 
very  elongated  transversely,  like  that  of  the  Dog  and  Cat.  It  is  closely  applied  against 
the  lumbar  vertebrae,  as  in  the  Horse,  but  its  anterior  face  is  much  more  enveloped  by 
tlie  peritoneum      Its  right  extremity  rests  on  t!ie  duodenum,  while  the  left  corresponds  to 


THE  DIGESTIVE  APPARATUS  IN  BIRDS.  435 

the  spleen  and  left  kidney.     Its  texture  is  consistent,  and  of  a  greyish-white  colour.     The 
duct  of  Wirsung  terminates  along  with  the  ductus  choledochus  in  the  ampulla  of  Vater. 

3.  Spleen. — This  is  not  falciform,  but  quadrangular;  its  inferior  extremity  is  larger 
than  the  superior.  It  is  attached  to  the  stomach  by  the  great  omentum,  and  its  inner 
face  is  divitled  into  two  portions  by  a  salient  ridge  ;  a  little  in  front  of  this  is  a  fissure 
the  hilam  lienis,  by  which  vessels  enter  it. 


CHAPTER  III. 

THE   DIGESTIVE   APPARATUS   OF   BIRDS. 

Constructed  on  the  same  plan  as  tliat  of  Mammals,  the  digestive  apparatus  of  Birds 
nevertheless  oilers  in  its  arrangement  several  important  peculiarities,  which  will  be 
hurriedly  noticed  in  reviewing,  from  the  mouth  to  the  anus,  its  different  sections. 

Month  — The  essentially  distinctive  character  of  the  mouth  of  birds  consi.>ts  in  the 
absence  of  lips  and  teeth,  these  organs  being  replaced  by  a  horny  production  fixed 
to  each  jaw,  and  forming  the  salient  part  termed  the  beak.  In  the  GaUinacx,  the  beak 
is  short,  pointed,  thick,  and  strong,  the  upper  mandible  being  curved  over  the  lower.  In 
Palmipeds,  it  is  longer,  weaker,  flattened  above  and  below,  widened  at  its  free  extremity, 
and  furnished  within  the  mouth,  on  the  borders  of  each  mandible,  with  a  series  of  thin 
and  sharp  txansverse  laminae  to  cut  the  herbage. 

Tiie  muscular  appendage,  or  tongue,  lodged  in  the  buccal  cavity,  is  suspended  to  a 
remarkably  mobile  hyoidean  apparatus.  Covered  by  a  horny  epithelium,  and  provided  at 
its  base  with  several  papillre  directed  backwards,  this  organ  always  affects  the  form  of 
the  lower  jaw :  in  Poultry  it  is  like  the  barbed  head  of  an  arrow,  the  point  being  directed 
forwards ;  in  Pigeons  this  saggital  form  is  still  more  marked  ;  in  Geese  and  Duchs,  on 
the  contrai7,  and  in  consequeuce  of  the  wide  shape  of  the  beak,  it  has  not  this  disposition, 
and  is  softer  and  more  flexible  than  in  the  Gallinaose. 

With  regard  to  the  salivary  glands  annexed  to  the  mouth,  they  are  imperfectly 
developed,  the  presence  of  the  fluids  they  secrete  being  less  necessary  in  birds  than  iii 
Mammals,  as  the  food  is  nearly  always  swallowed  without  undergoing  mastication; 
consequently  insalivation  is  all  but  useh  ss. 

Gurlt^  speaks  of  a  parotid  gland  situated  beneath  the  zygomatic  arch,  whose  duct 
opens  into  the  mouth  behind  the  commissure  of  the  jaws.  Meckel  names  this  organ  the 
angular  gland  of  the  mouth,  and  says  that  it  is  difficult  to  regard  it  as  representing  the 
parotids,  any  morethan  the  glands  of  the  cheeks  and  lips.  Duvernoy-  categorically 
assimilates  it  to  the  latter. 

The  sublingual  glands  lie  in  the  median  line  throughout  nearly  their  whole  extent, 
and  form  an  apparently  single  and  conical  mass,  whose  apex  occupies  the  re-entering 
angle  formed  by  the  union  of  the  two  braiiches  of  the  lower  maxilla. 

According  to  Duvernoy,  the  submaxillary  glands  are  represented  by  two  very  small 
organs  situated  behind  the  preceding.  Their  existence,  however,  is  far  from  being 
general ;  for  among  common  poultry,  the  Turkey  was  thii  only  bird  in  which  Duvernoy 
observed  these  submaxillary  glands. 

Pharynx  (Fig.  221,  2). — This  cavity  is  not  distinct  from  the  mouth,  the  soft  palate 
being  entirely  absent  in  birds.  On  its  sraperior  wall  mav  be  remarked  the  guttural  orifice 
of  the  nasal  cavities :  a  longitudinal  slit  divided  into  two  by  the  infi  rior  border  of  the 
vomer.  Below  is  another  less  extensive  slit,  the  entrance  to  the  larynx,  and  which  is 
remarkable  for  the  complete  absence  of  the  epiglottidean  operculum. 

OESOPHAGUS. — Tills  canal  is  distinguished  by  its  enormous  calibre  and  great  expansi- 
bility. Its  walls  are  very  thin,  and  contain  in  their  substance  lenticular  glands,  easily  seen 
in  an  inflated  cesophagus,  in  consequence  of  the  tenuity  and  transparency  of  its  textures. 

At  its  origin,  the  oesophageal  canal  is  not  separated  from  the  pharynx  by  any 
constriction ;  in  its  course  it  lies  alongside  the  long  muscle  of  the  neck,  and  the  trachea  ; 
its  terminal  extremity  is  inserted  into  the  first  compartment  of  the  stomach,  or  .succentric 
ventricle,  alter  entering  the  thorax  and  passing  above  the  origin  of  the  bronchi, 
between  tlieir  two  branches. 

In  Palmipeds,  the  resophagus  is  dilated  in  its  cervical  portion  in  such  a  manner  as 
to  form,  wheu  its  walls  are  distended,  a  long  fusiform  cavity. 


'  Anatomic  der  Hausvogel.*    Berlin,  1849. 

Cuvier.     '  Anatomic  Compare'e.'     2nd  Edition.     Pari?,  1836. 


436 


THE  DIGESTIVE  AFPABATUS  IN  BIEDS. 


Fiff.  221. 


GEKEKAL   VIEW   OF   THE   DIGESTIVE   APPARATUS  OF   A   FOWL. 


The  abdominal  muscles 
have  been  removed,  as 
well  as  the  sternum, 
heart,  trachea,  the 
greater  portion  of  the 
neck,  and  all  the  head 
except  the  lower  jaw, 
which  has  been  turned 
back  to  show  the  tongue, 
the  pharynx,  and  the 
entrance  to  the  larynx. 
The  left  lobe  of  the 
liver,  succentric  ven- 
tricle, gizzard,  and  in- 
testinal mass,  have  been 
pushed  to  the  right  to 
exhibit  the  different 
portions  of  the  alimen- 
tary canal,  and  to  ex- 
pose the  ovary  and  ovi- 
duct. 

1,  Tongue;  2,  Pharynx "j 
3,  First  portion  of  the 
oesophagus ;  4,  Crop ; 
5,  Second  portion  of  the 
oesophagus ;  6,  Succen- 
tric ventricle ;  7,  Giz- 
zard ;  8,  Origin  of  the 
duodenum ;  9,  First 
branch  of  the  duodenal 
flexure ;  10,  Second 
branch  of  the  same , 
11,  Origin  of  the  float- 
ing portion  of  the  small 
intestine ;  12,  Small 
intestine;  12',  Terminal 
portion  of  this  intestine, 
flanked  on  each  side 
by  the  two  caeca  (re- 
garded as  the  analogue 
of  the  colon  of  mam- 
mals); 13,  13,  Free 
extremities  of  the  ce- 
cums ;  14,  Insertion  of 
these  two  culs-de-sac 
into  the  intestinal 
tube;  15,  Rectum  ;  I'i, 
Cloaca;  17,  Anus;  18, 
Mtseutery ;  19,  Left 
lobe  of  the  liver  •  20, 
Right  lobe;  21,  Gall- 
bladder; 22,  Insertion 
of  the  pancreatic  and 
biliary  ducts ;  the  two 
pancreatic  ducts  are  the 
anteriormost,  the  cho- 
ledic  or  hepatic  is  in  the 
middle,  and  the  cystic 
duct  is  posterior;  23, 
Pancreas ;  24,  Dia- 
phragmatic aspect  of 
the  lung;  25,  Ovary 
(in  a  state  of  atrophy  ; 
26,  Oviduct. 


THE  DIGESTIVE  AFPABATUS  IN  BIRDS.  437 

In  Gallmacv  (Fi^j.  221.  3.  4,  rt >.  this  dilataiion  does  not  exist;  but  the  oesophao:us 
presents  in  its  course,  and  ininit  diately  before  eiit(  ring  tlie  chest,  au  ovoid  membranous 
pouch  named  the  crop  (or  unjliivieg.)  In  the  oesophagus  of  the.se  birds,  then,  wp  find 
two  distinct  sections,  joined  end  to  end — one  superior  or  cervical,  the  other  inferior  or 
thoracic,  on  tlie  limit  of  wliich  is  the  crop.  The  latter  does  not  dilier  in  its  structure 
from  the  oesophagus,  and  is  a  temporary  reservoir  for  the  food  swallowed  by  the  animal 
duriuLj  its  meal,  and  where  it  is  softened  by  being  impregnated  with  a  certain  quantity 
of  fluid;  afttr  wliich  it  is  passed  into  the  succentric  ventricle  by  the  contractions  of  the 
'jxtcrnal  membrane  of  the  crop,  aided  by  a  wide  subcutaneous  cervical  muscle  which 
covers  tliat  reservoir. 

In  Pi(]eons,  the  crop  is  also  present ;  but  it  is  divided  into  two  lateral  pouches,  and 
exhibits  glandular  eminences  towards  the  common  inferior  opening  of  these  sacs  into  the 
oesophagus.  "  Otherwise,  singular  changes  are  observed  in  the  apparent  structure  of  its 
walls  in  the  male  as  well  as  in  the  female,  during  incubation,  or  during  the  first  weeks 
after  hatching."  (Hunter  was  the  first  to  observe  this ; — '  Observations  on  Certain  Parts 
of  the  Animal  Economy,'  London,  1792).  "At  this  period,  the  membranes  of  the  crop 
become  thickened ;  the  vessels,  more  numerous  and  more  apparent,  are  redder,  and  the 
glands  mtire  developed.  The  intern.il  surface  is  divided  by  folds  or  ridges,  which  cross 
each  other,  and  form  triangular  meshes  ;  while  an  apparently  milky  fluid  is  poured  out 
from  the  secret.)ry  poris  into  the  cavity  of  the  crop.  Pigeons  exclusively  nourish  their 
young  with  this  fluid  dui'ing  the  first  three  days  of  their  existence."  ' 

Stojiach  —The  stomach  presents  numerous  variations  in  birds.  Its  simplest  form  is 
seen  in  the  heron,  pelican,  petrels,  etc.,  where  it  is  a  single  tac  provided  with  a  thick 
zone  of  glands  around  the  entrance  of  the  oesophagus,  which  secrete  the  gastric  juice. 
But  in  the  majority  of  tlie  other  species,  and  particularly  in  our  domesticated  birds,  the 
disposition  of  the  stomacii  is  modified  and  complicated  ;  the  glandular  zone  destined  for 
the  gastric  secretion  forms  a  special  compartment — the  succentric  ventricle,  and  this  is 
followed  by  a  second  reservoir — tlie  gizzard,  which  is  remarkable  for  the  strong  muscular 
constitution  of  its  walls.  The  first  is  also  named  the  glandular  stomach,  and  the  second 
the  muscular  stomach. 

Glandular  str»nach,  or  succentric  ventricle  (lyrovenfrictdus)  (Fig.  221,  6). — This  is  an 
ovoid  sac  placed  in  the  median  plane  of  the  body,  between  the  two  lobes  of  the  liver,  and 
beneath  the  aorta.  Its  anteiior  extremity  receives  the  insertion  of  the  cesophagus;  the 
posterior  is  continued  by  the  gizzard  The  volume  of  this  stomach  is  inconsiderable,  and 
its  cavity  is  very  narrow;  the  aliment  does  not  accumulate  in  it,  but  merely  passes 
tlirougli,  carrying  with  it  the  acid  juice  which  afterwards  dissolves  its  protein  elements.  Its 
■walls  have  three  tunics  :  an  external  or  peritoneal ;  a  middle,  formed  of  white  muscular 
fibres,  continuous  with  those  of  the  cesuphagns;  and  an  internal,  of  a  mucous  nature,  per- 
forated by  orifices  for  the  passage  of  the  gastric  juice.  Tiiese  are  small  cylinders  placed 
perpendicularly  to  the  surface  of  the  stomach,  closely  laid  against  one- another,  like  the 
microscopic  glands  of  Lieberkiihn,  and  contained  in  the  cellular  layer  uniting  the  inner 
to  the  middle  tunic.  The  glandular  structiu-e  of  this  receptacle  sufficiently  demonstrates 
that  it  should  be  assimilated  to  the  right  sac  of  the  stomach  in  Solipeds,  and  therefore 
must  be  regarded  as  the  true  stomach. 

Gizzard,  OT  muscular  stomdch  (ventricidus  Indbostis)  (Fig.  221,  7). — Much  more  volu- 
minous than  the  preceding,  this  stomach  is  oval  in  form,  depressed  on  each  sitie.  and 
situated  behind  the  liver,  being  partly  covered  by  the  lateral  lobes  of  that  gland.  Above, 
and  to  the  right,  and  at  a  short  distance  from  each  otiier,  are  seen  the  insertion  of  the 
succentric  ventricle  and  the  origin  of  the  duodenum.  The  cavity  of  the  gizzard  always 
contains  food  mixed  with  a  large  quantity  of  silicious  pebbles,  whose  use  will  be  indicated 
hereafter. 

This  viscera  is  composed  of  the  three  tunics  which  form  the  walls  of  all  the 
abdominal  reservoirs.  Tlie  internal,  or  mucous,  is  distinguished  by  the  thickness  and 
extraordinary  induration  of  its  epidermic  layer,  which  presents  nearly  all  the  characters 
of  horny  tissue,  and  is  so  easilj'  detached  from  the  mucous  chorium  that  it  is  often 
regarded  as  a  special  membrane.  On  the  adherent  face  of  this  corium  are  applied  two 
powerful  red  muscles — a  superior  and  inferior,  occupying  the  borders  of  the  organ,  and 
whose  fibres,  disposed  in  flexures,  pass  from  side  to  side,  and  are  inserted  into  a  strong, 
nacrous  aponeurosis  on  the  lateral  surfaces  of  the  organ.  Outside  this  contractile 
apparatus  is  a  thin  peritoneal  envelope. 

The  gizzard  is  the  triturating  apparatus  of  birds.  When  the  aliment  reaches  its  cavity 
it  has  not  yet  submitted  to  any  disaggregation,  but  here  it  meets  with  all  the  conditions 


Buvernoy.    •  Legons  d'Anatomie  Compare'e  de  G.  Cuvier.'    2nd  Edition. 
31 


438  THE  DIGESTIVE  APPARATUS  IN  BIRDS. 

indispensable  to  the  accomplishment  of  thi.s  act:  two  energetic  compressor  muscles,  a 
C(inieous  layer  spread  over  the  internal  surface  of  the  viscera,  giving  to  it  the  rigidity 
necessary  to  r  sist  the  enormous  pressure  exercised  on  its  contents;  and  silicious 
pebbles— veritable  artificial  teeth — wliich  an  admirable  instinct  causes  i)irds  to  swallow, 
and  between  which,  by  the  efforts  of  the  tiiturating  muscles,  the  food  is  bruised.  This 
triturating  action  of  the  gizzard  is  only  effected  in  birds  fed  on  hard  coriaceous  aliment, 
such  as  the  various  kind  of  grain.  It  would  be  useless  in  birds  uf  prey,  in  which  the 
two  gizzard  muscles  are  replaced  by  a  tliin  fleshy  membrane  of  uniform  thickness; 
showing  that  the  presence  of  these  muscles  is  subordinate  to  the  kind  of  alimentation. 

Intestine.— The  length  of  the  intestine  varies,  as  in  Mammals,  according  to  the 
nature  of  the  food  :  very  short  in  birds  of  prey,  it  is  notably  elongated  in  omnivorous 
and  granivorous  birds.  Its  diameter  is  nearly  UTiitbrm  throughout  its  whole  extent, 
and  it  is  difficult  to  establish  in  birds  the  various  distinctions  recognised  in  the  intestine 
of  Mammalia.  It  begins  by  a  portion  curved  in  a  loop,  which  represents  the  duodenum, 
and  whose  two  branches,  lying  aide  by  side,  are  pirallel  to  each  other  like  the  colic 
flexure  of  Solipeds.  Fixed  by  a  short  mesenteric  fryenum  to  the  colon,  this  part  of  the 
intestine  includes  the  pancreas  between  its  two  branches.  Its  curvature  floats  freely  in 
the  pelvic  portion  of  the  abdominal  cavity  (fig.  221,  S,  9,  10). 

To  the  duodenal  loop  succeed  convolutions  suspended  to  the  sublumbar  pnrietes  by  a 
long  mesentery,  and  which  are  rolled  up  into  a  single  mass,  elongated  from  before  to 
behind,  occupying  a  middle  position  between  the  air  sacs  of  tiie  abdominal  cavity. 
Tlie  analogy  existing  between  this  mass  of  convolution.s,  and  the  floating  iiortion  of  the 
small  intestine  of  Mammals,  does  not  require  demonstration  (fig.  221,  11,  J  2). 

The  terminal  part  of  this  floating  intestine  lies  besicle  the  duodenal  loop,  and  is 
flanked  by  the  two  appendages  disposed  like  cxca.  'Ihese,  scarcely  marked  in  the 
Piijeon  by  two  sm  dl  tubercles  placed  on  the  track  of  the  intestinal  tube,  do  not  measure 
less  than  from  six  to  ten  inches  in  the  other  domesticated  birds;  thiy  are  two  narrow 
culs-de-sac,  slightly  club-shaped  at  their  closed  extremities,  which  are  free  and  directed 
towards  the  origin  of  the  intestine,  while  the  other  extremity  opens  into  the  intestinal 
canal  near  the  anus.  There  are  always  alimentary  matters  in  these  sacs,  tliese  becoming 
introduced,  in  following  a  retrograde  course,  by  the  same  almost  unkirown  mechanisn-i 
which  presides  over  the  accumulation  of  spermatic  fluid  in  the  vesiculas  seminales.  Ac- 
cording to  the  majority  of  naturalists,  these  two  appendages,  although  described  as  cxca,  do 
not  represent  the  reservoir  bearing  that  designation  in  Mammals.  This  reservoir  is 
nothing  more  than  a  small  particular  appendix  placed  on  the  track  of  the  intestine,  in  front 
of  the  free  extremity  of  the  ab;)ve-mentioned  culs-de-sac,  and  which  is  only  to  be  found 
in  a  small  number  of  birds,  and  among  these  sometimes,  as  Gurlt  affirms,  is  the  Goose. 
According  to  tliis  view,  which  appears  to  be  a  very  rational  one,  the  portion  of  intestine 
comprised  between  the  two  blind  luhes  annexed  to  the  viscera  (Hg  221,  12')  corresponds 
to  the  colon,  and  these  tubes  themselves  are  only  dependencies  of  this  inte.^tine. 

The  rectum  (fig.  221,  15)  terminates  the  digestive  canal;  it  is  the  brief  portion  of 
intestine  which  follows  the  opening  of  the  cajea.  Placed  in  the  sublumbar  region, 
this  viscus  is  terminated  by  a  dilatation,  the  cloaca  ffig.  221,  lU),  a  vestibule  common 
to  the  digestive  and  genito-urinary  passages,  which  opens  externally  at  the  anus,  lodges 
the  penis  when  it  exists,  and  serves  as  a  confluent  for  the  ureters,  oviduct,  bursa  of 
Fabricius,  and  the  deferent  canals. 

Abdominal  Appendages  of  the  Digestive  Canal. — Liver  (Fig.  221,  19,  20). — This 
is  a  voluminous  gland,  divided  into  two  principal  lobes — a  right  and  left,  the  former 
always  larger  than  the  latter ;  these  incompletely  include,  on  each  side,  the  gizzard  and 
succentric  ventricle.  In  the  Pigeon,  this  gland  is  provided  with  a  gall-bladder 
(fig.  221,  21)  attached  to  the  internal  face  of  the  right  lobe.  But  the  arrangement  of 
the  excretory  apparatus  is  not  altogether  identical  with  that  observed  in  Mammals 
■which  possess  this  receptacle  ;  as  two  biliary  ducts  open  separately  into  the  intestine 
towards  the  extremity  of  the  second  branch  of  the  duodenal  loop.  One  proceeding 
directly  from  the  two  lobes  of  the  liver,  is  the  hepatic  or  choledic  duct ;  the  other,  the  cydic 
duct,  remains  independent  of  the  Litter,  and  opens  behind  it.  It  carries  into  the  digestive 
canal  the  bile  accumulated  in  the  gnll-bladder,  and  which  arrives  there  by  a  particular 
duct  belonging  exclusively  to  the  right  lobe;  the  cvstic  canal  is  a  braneli  of  this  duct 
(fig.  221,  22). 

Pancreas  (Fig.  221,  23).— In  the  Galhnacse.,  this  gland  is  very  devdoped,  long,  and 
narrow,  and  is  comprised  in  the  duodenal  loop  or  flexure;  at  the  extremity  next  the 
gizzard  it  has  two  principal  excretory  ducts,  which  separately  pierce  the  intestinal 
membranes,  a  little  in  front  of  the  hepatic  canal. 
4  Splfen. — This  is  a  small,  red-coloured,  disc-shaped  bodv,  placed  to  the  right  of  the 
stomachs,  on.  the  limit  of  the  gizzard  and  buccentric  ventricle. 


BOOK  III. 
Kespieatory  Apparatus. 

The  maintenance  of  life  in  animals  not  only  requires  the  absorption  of  the 
organisable  and  nutritive  matters  conveyed  to  the  internal  surface  of  the 
digestive  canal,  but  demands  that  another  principle,  the  oxygen  of  the  atmo- 
sphere, should  enter  with  these  materials  into  the  circulation.  In  animals 
with  red  blood,  this  element,  in  mixing  with  the  nutritive  fluid,  commences 
by  expelling  an  excrementitial  gas,  carbonic  acid,  and  communicating  a  bright 
red  colour  to  that  fluid,  with  which  it  circulates  ;  it  is  brought  into  contact, 
in  the  general  capillary  system,  with  the  minute  structures  of  the  various 
apparatus,  exercising  on  the  organic  matter  comjjosing  them  a  special 
excitory  influence,  without  which  the  tissues  could  not  manifest  their 
properties,  as  well  as  inducing  a  combustible  action  which  evolves  the  heat 
proper  to  the  animal  body. 

This  new  absorption  constitutes  the  phenomenon  of  respiration.  In  the 
Mammalia,  this  is  etfccted  in  the  lungs :  parenchymatous  organs  hollowed  out 
into  a  multitude  of  vesicular  spaces  whicli  receive  the  atmospheric  air  and 
expel  it,  after  depriving  it  of  a  certain  quantity  of  oxygen,  and  giving,  in  return, 
a  proportionate  quantity  of  carbonic  acid.  These  organs  are  lodged  in  the 
thoracic  cavity,  whose  alternate  movements  of  dilatation  and  contraction  they 
follow.  They  communicate  with  the  external  air  by  two  series  of  canals 
placed  end  to  end  :  1,  A  cartilaginous  tube  originating  in  the  pharyngeal 
vestibule,  and  i-amifving  in  the  lungs ;  2,  The  nasal  cavities,  two  fossae 
opening  into  that  vestibule,  and  commencing  by  two  openings  formed  at  the 
anterior  extremity  of  the  head. 


CHAPTER  I. 
RESPIRATORY   APPARATUS   OF    MAMMIFERS. 

In  this  apparatus  we  will  first  study  the  organs  external  to  the  thoracic 
cavity :  the  nasal  cavities,  and  larynx  and  trachea  ;  then  the  chest  and  the 
organs  it  contains — the  lungs. 

To  this  study  will  be  added  that  of  the  two  glandiform  organs  whose 
uses  are  unknown,  but  which,  by  their  anatomical  connections,  belong  to  the 
respiratory  apparatus.     These  are  the  thyroid  bodies  and  the  thymas  gland. 

THE   NASAL    CAVITIES. 

These  cavities  are  two  in  number,  a  right  and  left,  and  oiTer  for  study  : 
their  entrance,  or  nostrils — the  fossse,  properly  called,  which  constitute 
these  cavities :  and  the  diverticuli  named  sinuses. 


440 


THE  RESPIRATORY  APPARATUS  IN  MAMMALIA. 


Preparation. — Remove  the  lower  jaw  from  three  heads.  On  the  first  of  these  make 
two  transverse  sections,  one  passing  between  the  second  and  third  molar  tootli,  the  other 
behind  the  dental  arcade.  Saw  through  the  second  head  longitudinally  and  vertically,  a 
little  to  one  side  of  the  median  line.  On  the  third  make  a  horizontal  section  in  such  a 
manner  as  to  obtain  an  inferior  portion  analogous  to  that  shown  in  figure  23. 

1.  The  Nostrils. 

The  nostrils  are  two  ohlong,  lateral  openings,  situated  at  the  extremity 
of  the  nose,  circumscribed  by  lij)s  or  movable  ivings  (alse)  disjiosed  in  an 
oblique  direction  downwards  and  inwards,  and  slightly  curved  on  them- 
selves, so  as  to  present  their  concavity  to  the  external  side. 

The  lips  or  alse  of  the  nostril  are  enveloped,  inwardly  and  outwardly,  by  a 
thin,  delicate  skin,  covered  by  fine,  short  hairs.  The  external  is  concave  on 
its  free  margin  ;  the  internal  is  convex.  The  commissure  which  unites  these 
two  wings  superiorly,  forms  a  slight  ci'oss  curved  inwards.  When  the  finger 
is  introduced  into  this  commissure  it  does  not  enter  the  nasal  cavity,  but  the 
false  nostril :  a  conical  pouch  formed  by  the  skin,  extending  to  the  angle 
comprised  between  the  nasal  spine  and  tlic  elevated  process  of  the  pre- 
maxillary  bone. 

In  the  Ass,  according  to  Goubaux,  the  false  nostril  is  areolated  at  the 
posterior  extremity,  which  ascends  beyond  the  summit  of  the  re-entering 
angle  formed  by  the  nasal  and  premaxillary  prolongation. 

The  inferior  commissure  is  round  and  wide,  and,  towards  the  bottom, 
presents  an  opening,  sometimes  double,  which  looks  as  if  punched  out ;  this 
is  the  inferior  orifice  of  tlie  lachrymal  duct,  which,  in  the  Ass  and  Mule,  is 
carried  to  the  inner  face  of  the  external  wing,  near  the  superior  commissure. 
Structure. — The  nostril  is  composed  of  a  cartilaginous  framework, 
muscles  to  move  it,  and  integuments,  vessels,  and  nerves. 

Cartilaginous  framework  (Fig.  222). — This  framework  is  formed  by  a 
cartilage,  bent  like  a  comma,  and  which,  in  its  middle 
part,  lies  against  that  of  the  opposite  side,  the  two 
making  a  kind  of  figure  X.  Fixed  in  a  movable 
manner  to  the  inferior  extremity  of  the  middle  septum 
of  the  nose,  by  means  of  short  interposed  fibres,  this 
cartilage  offers  :  a  wide  upper  part,  situated  in  the 
substance  of  the  inner  wing  of  the  nostril,  and  covered 
by  the  transverse  muscle  of  the  nose  (Fig.  222,  1)  ; 
and  an  inferior  portion,  which,  after  passing  into  the 
lower  commissure,  is  jirolonged,  in  a  blunt  point,  to 
the  external  wing,  where  it  receives  the  insertion  of 
several  fasciculi  belonging  to  the  orbicularis  muscle 
of  the  lips,  the  pyramidal  muscle  of  the  nose,  and 
the  supernaso-labialis  (Fig.  222,  2).  Each  wing, 
therefore,  possesses  a  cartilaginous  skeleton  ;  but  that 
of  the  external  wing  is  very  incomjilete,  in  conse- 
quence of  its  being  only  formed  by  the  inferior  ex- 
tremity of  the  common  cartilage. 

This  cartilage,  it  will  be  imderstood,  sustains  the 
2,  2,  Narrow  e.xtremity  alaa  of  the  nose,  prevents  their  falling  inwards,  and 
prolonged  into  the  ex-   always  keeps   open  the  external  orifices  of  the  re- 

ternal  wins :  3,  bupenor         .     ■;  , 

or  anterior  border  of  the    spiratory  apparatus. 

septum.  Muscles. — The  motor  muscles  of  the  alfe  are  all 

dilators  in  the  domesticated  animals.     They  are  :  the 

transversalis  nasi  (dilatator  naris  anterior — Percivall),  or  transversalis  of  the 


Ficr.  22: 


CARTILAGES  OF  THE  NOSE. 

1,  1,  Wide  portion,  form- 
ing the  base  of  the  inter- 
nal wing  of  the  nostril , 


THE  NASAL  CAVITIES.  4n 

nose,  a  single  muscle  placed  on  the  widened  portion  of  the  cartilaginous 
pieces  ;  the  supermaxillo-nasalis  magnus  (dilatator  naris  lateralis — Percivall), 
or  pyramidal  muscle  of  the  nose,  whose  insertion  occupies  the  wliole  extent 
of  the  external  wing ;  the  supermaxillo-nasalis  parvus  (nasalis  hrevis  lahii 
superioris — Percivall),  fixed,  by  its  two  portions,  to  the  skin  of  the  false 
nostril;  the  middle  anterior  (depressor  alse  nasi — Percivall)  which  is  con^ 
founded,  superiorly,  with  the  external  fasciculus  of  the  preceding  muscle, 
it  being  attached  to  the  inferior  branch  of  the  cartilaginous  appendix  of  the 
maxillary  turbinated  bone ;  and,  lastly,  the  super naso-lahialis  (levator  lahii 
superioris  aloique  nasi — Percivall),  whose  anterior  branch  is  inserted,  in 
j)art,  into  the  external  wing.  All  these  muscles  having  been  described  in 
the  Myology  (page  220),  need  not  be  further  alluded  to  here. 

Integuments  of  the  nose. — The  skin  covering  the  alfe  of  the  nose,  ex- 
ternally, is  doubled  over  their  free  margin  to  line  their  internal  face,  being 
prolonged  over  the  entire  extent  of  the  false  nostril,  and  is  continued,  in 
the  nasal  fossae,  properly  called,  by  the  pituitary  membrane.  This  skin  is 
fine,  thin,  charged  with  colouring  pigment,  often  marked  by  leprous  spots, 
and  adheres  closely  to  the  muscles  included  between  its  duplicatures,  through 
the  medium  of  a  very  dense  and  resisting  fibro-cellular  tissue. 

Vessels  and  nerves. — The  nostrils  are  supplied  with  blood  by  the  superior 
coronary,  the  external  nasal,  and  the  palato-labial  arteries  ;  it  is  returned  by  the 
glosso-facial  veins,  and  partly  by  the  venous  network  of  the  nasal  mucous 
membrane.  The  lymphatics,  large  and  abundant,  receive  those  of  the 
pituitary  membrane,  and  join  the  submaxillary  glands  by  passing  over  the 
cheeks.  The  nerves  are  very  numerous,  the  sensory  being  derived  from 
the  maxillary  branch  of  the  fifth  pair,  and  the  motors  from  the  facial 
nerve. 

FtTNCTiONS. — The  nostrils  permit  the  entrance  to  the  nasal  cavities, 
of  the  air  which  is  to  pass  to  the  lungs.  Their  dilatability  allows  the 
admission  of  a  greater  or  less  volume,  according  to  the  demands  of 
respiration.  It  is  to  be  remarked  that,  in  Solipeds,  the  nostrils  constitute 
the  only  channel  by  which  the  aerial  column  can  be  introduced  to  the 
trachea,  in  consequence  of  the  great  development  of  the  soft  palate,  which  is 
opposed  to  the  entrance  of  air  by  the  mouth  ;  these  orifices  are  also,  for  the 
same  reason,  relatively  larger  than  in  the  other  domesticated  animals,  in 
which  the  passage  of  air,  by  the  buccal  cavity,  is  easily  accomplished. 

2.  The  Nasal  Fossx.     (Figs  223,224.) 

Clianneled  in  the  substance  of  the  head,  above  and  in  front  of  the  palate, 
and  separated  from  one  another,  in  the  median  plane,  by  a  cartilaginous 
septum  which  does  not  exist  in  the  skeleton,  the  nasal  fossae  extend  from  the 
nostrils  to  the  cribriform  plate  of  the  ethmoid  bone,  in  a  direction  parallel 
to  the  larger  axis  of  the  head.  Their  length  is,  therefore,  exactly  measured 
by  that  of  the  face.     See  Fig.  223  for  the  whole  of  these  cavities. 

The  nasal  fossae  are  formed  by  two  lateral  imlls,  a  roof  or  arch,  a  floor,  and 
two  extremities. 

Walls. — The  two  walls  are  very  close  to  each  other,  and  the  more  so  as 
they  are  examined  towards  the  ethmoid  bone  and  the  roof  of  the  cavity.  The 
space  separating  them  varies,  in  proportion  as  it  is  measured  at  the  level  of 
the  turbinated  bones  or  at  the  meatuses. 

Inner  wall. — This  is  formed  by  the  nasal  septum,  and  is  perfectly 
smooth. 


•142 


THE  RESPIRATORY  APPARATUS  IN  MAMMALIA. 


Outer  wall. — This  is  chiefly  constituted  by  the  supermaxillary  bone, 
is  very  rugged,  and  is  divided  into  three  meatuses,  or  passages,  by  the 
turbinated  bones — the  irregular  columns  applied  against  the  inner  face  of  the 
before-mentioned  bone. 

The  turbinated  hones  have  already  been  described,  and  we  will  only  now 
refer  to  the  principal  features  of  their  organisation.  Each  is  formed  of  a 
bony  plate  rolled  upon  itself  (Fig.  223,  2,  3),  and  is  divided,  internally,  into 
two  sections,  the  superior  of  which  forms  part  of  the  sinus,  and  the  in- 
ferior belongs  to  the  nasal  fossae ;  they  are  continued,  inferiorly,  by  a  fibro- 
cartilaginous framework,  which  prolongs  tlieir  nasal  section  to  the  external 
orifice  of  the  nose.  The  flexible  appendix  of  tlie  ethmoidal  turbinated  bone 
is  usually  single,  sometimes  double,  and  disappears  before  reaching  the  alee 
of  the  nose.     That  of  the  maxillary  turbinated  bone  is  always  bifui-cated, 

Fio;.  223. 


TRANSVERSE  SECTION   OF   THE   HEAD   OF   AN   OLD   HORSE,   SHOWING   THE   ARRANGEMENT 
OF   THE   NASAL   CAVITIES   AND   MOUTH. 

1,  Nasal  fossa ;  2,  Superior  turbinated  bone ;  3,  Inferior  ditto ;  4,  Median  septum  of 
the  nose ;  5,  Centi-al  part  of  the  buccal  cavity  (drawn  more  spacious  than  it 
really  is  when  the  two  jaws  are  brought  together) ;  6,  6,  Lateral  portions  of  the 
same ;  7,  Section  of  the  tongue. 

and  its  antero-superior  branch  is  directly  continued  by  the  superior  extremity 
of  the  internal  wing  of  the  nostril. 

The  meatuses  are  distinguished  into  superior,  middle,  and  inferior,  or  into 
anterior,  middle,  and  posterior,  as  the  head  is  inspected  in  a  vertical  or  hori- 
zontal position.  The  superior  passes  along  the  corresponding  border  of  the 
ethmoidal  turbinated  bone,  and  is  confounded  with  the  roof  of  the  nasal 
cavity  ;  it  is  prolonged,  behind,  to  near  the  cribriform  plate  of  the  ethmoid 


THE  NASAL  CAVITIES 


443 


bone :  it  is  tlie  narro-^est.  The  middle,  comprised  between  the  two  tur- 
binated bones,  presents,  on  arriving  near  the  ethmoidal  cells,  the  orifice 
■which  brings  all  the  sinuses  into  communication  with  the  nasal  fossa.  This 
orifice  is  ordinarily  narrow  and  curved;  but  we  have  seen  it  sometimes 
converted  into  a  foramen  sufficiently  wide  to  permit  the  introduction  of  a 
finger  end.  It  is  also  by  this  meatus  that  the  inferior  compartment  of  the 
turbinated  bones  opens  into  the  nasal  fossa,  these  two  bones  being  each 
rolled  in  a  contrary  direction.  The  inferior  meatus,  situated  under  the 
maxillary  turbinated  bone,  is  not  distinct  from  the  floor  of  the  nasal  cavity. 
See  figure  224  for  the  arrangement  of  the  tui'binated  bones  and  the  meatuses 
on  the  external  wall  of  the  nosp. 

Roof  or  arch. — This  is  formed  by  the  nasal  bone,  and  is  only  a  narrow 
channel,  confoimded,  as  has  been  said,  with  the  superior  meatus. 

Floor. — Wider,  but  not  so  long  as  the  roof,  which  is  opposite  to  it,  but 
from  which  it  is  distant  by  the  height  of  the  cartilaginous  septum,  the  floor 
is  concave  from  side  to  side,  and  rests  on  the  palatine  arch,  which  separates 
the  mouth  from  the  nasal  cavities. 

In  front  of  this  nasal  region  is  remarked  the  canal  or  organ  of  Jacobson  : 
a  short  duct  terminating  in  a  cul-de-sac  in  the  middle  of  the   cartilaginous 


Fis.  224. 


LOXGrrUDINAL   MEDIAN   SECTION   OF   THE   HEAD   AND   UPPER   PART   OF   NECK. 

1,  1,  Atlas ;  2,  2,  Dentata  ;  3,  Trachea  ;  4,  Right  stylo-thvroideus  ;  5,  Guttural 
pouch;  6,  Stvlo-pharyngeus ;  8,  Palato-pharyngeus ;  9,  Sphenoidal  sinus;  10, 
Cranial  cavity,  11,  Occiput;  12,  Parietal  protuberance;  13,  Frontal  sinus; 
14,  Ethmoidal  turbinated  bone;  15,  Maxillary  turbinated  bone;  16,  Entrance  to 
nostril,  18,  Pharyngeal  cavity;  19,  Inferior  maxilla;  20,  Premasilla;  21, 
Hard  palate. 


substance  which  closes  the  incisive  foramen.  At  the  bottom  of  this  cul-de- 
sac  opens  a  second  canal,  longer,  wider,  and  more  remarkable,  but  which 
has  not  yet  been  described.  (It  has  been  described  by  Stenson,  and  is  named 
"  Stenson's  duct.")  It  has  sometimes  the  diameter  of  a  writing  quill, 
commences  by  a  cul-de-sac  on  a  level  with  the  second  molar  tooth,  accom- 
panies the  inferior  border  of  the  vomer  from  behind  to  before,  where  it  is 
envelojjed  in  a  kind  of  cartilaginous  sheath — a  dependency  of  the  nasal 
septum ;  it  terminates,  as  we  have  said,  after  a  course  of  about  5  inches. 


444  THE  RESPIRATORY  APPARATUS  IN  3IAMMALIA. 

The  structure  of  this  duct  resembles  that  of  the  excretory  ducts  of  glands ; 
its  walls  are  evidently  composed  of  two  timics— an  internal  or  mucous, 
very  rich  in  follicles,  and  having  longitudinal  folds,  and  an  external,  of  a 
fibrous  nature  These  membranes  receive  numerous  vessels,  as  well  as 
nervous  divisions  emanating  from  a  long  filament  of  the  spheno-palatine 
ganglion,  and  which  may  be  traced  from  the  external  side  of  the  canal  to 
near  the  incisive  foramen,  where  it  is  lost.  Such  is  the  organ  of  Jacobson  ; 
its  uses  are  quite  unknown. 

Extremities. — The  anterior  or  inferior  extremity/  of  the  nasal  fossa  is 
formed  by  the  nostril  already  described.  The  posterior  or  superior  extremity 
presents,  above,  a  space  occupied  by  the  ethmoidal  cells.  Below  and  behind, 
this  extremity  communicates  with  the  pharyngeal  cavity  by  a  wide  oval 
opening,  which  is  circumscribed  by  the  vomer  and  palate  bones :  this  is  the 
guttural  opening  of  the  nasal  fossa. 

Structure. — The  nasal  fossfe  ofier  for  study  in  their  organisation : 
1,  The  hony  framework  by  which  these  cavities  are  formed ;  2,  The 
cartilaginous  septum  separating  them ;  8,  The  pituitary  membrane — the 
mucous  layer  covering  their  walls. 

1.  Bony  Framework  of  the  Nasal  Fossae. — This  comprises:  1,  The 
nasal,  maxillary,  frontal,  and  palate  bones,  which  together  form  a  vast  irre- 
gular tube  circumscribing  the  nasal  fossae  ;  2,  The  ethmoid  bone,  occupying 
the  bottom  of  this  tubular  cavity  and  the  turbinated  bones  aj^plied  against 
the  latei'al  walls ;  3,  The  vomer,  j)laced  in  the  median  plane,  and  serving  as 
a  support  for  the  cartilaginous  partition  dividing  this  single  cavity  into  two 
compartments.  All  these  bones  having  been  already  studied  in  detail,  we 
confine  oiu'selves  to  their  simple  enumeration. 

2.  Middle  Septum  of  the  Nose  ('Fig.  223,  4). — Formed  of  cartilage 
susceptible  of  ossification,  this  partition  is  nothing  more  than  the  perpendi- 
cular lamina  of  the  ethmoid  bone  prolonged  to  the  extremity  of  the  nose. 
Its  elongated  form  permits  us  to  recognise  in  it  two  faces,  two  borders,  and 
two  extremities.  The  faces  are  channeled  by  a  multitude  of  furrows,  which 
lodge  the  anastomosing  divisions  of  the  magnificent  venous  plexus  of  the 
pituitary  membrane. 

The  superior  border,  united  to  the  frontal  bone  and  median  suture  of  the 
nasal  bones,  expands  to  the  right  and  left  on  the  inner  faces  of  these,  in 
forming  two  laminfe,  thin  at  their  free  margin,  the  section  of  which  is 
represented  in  Fig.  223.  These  laminae  are  wide  enough  in  front  to  project 
b«yond  the  nasal  spine.  The  inferior  border  is  received  into  the  mortice  of 
the  vomer. 

The  posterior  extremity  is  continued  without  any  precise  limitation,  by 
the  perpendicular  lamina  of  the  ethmoid  bone. 

The  anterior  extremity,  a  little  wider,  supports  the  cartilages  of  the 
nostrils.  It  is  joined,  below,  to  the  premaxillary  bones,  and  is  spread  out 
on  the  incisive  openings  in  a  thick  layer  which  exactly  closes  them. 

This  septum  is  covered  by  a  thick  perichondrium,  which  adlieres 
intimately  to  the  pituitary  membrane. 

3.  Pituitary  Membrane. — This  membrane,  also  designated  the  olfactory 
mucous  membrane,  and  Schneiderian  membrane,  is  continuous  with  the  cutaneous 
integument  covering  the  inner  face  of  the  alse  of  the  nose.  Considered  at 
first  on  the  internal  wall  of  the  nasal  fossae,  the  pituitary  membrane  is  seen 
to  cover  the  cartilaginous  septum  forming  this  wall,  then  to  be  spread  over 
the  floor  as  well  as  the  roof  of  the  cavity,  reaching  the  outer  wall,  which 
it  also  covers  in  enveloping  the  external  surface  of  the  turbinated  bones, 


THE  NASAL  CAVITIES. 


445 


and  is  insinuated,  by  the  middle  meatus,  into  the  cells  of  the  inferior  or 
anterior  compartment  of  these  osteo-cartilagiuous  columns.  It  also  penetrates, 
by  the  semicircular  opening  of  this  meatus,  into  the  sinus,  to  give  it  its 
mucous  covering,  and  is  likewise  prolonged  into  the  apparatus  of  Jacobson. 
Behind,  it  is  confounded  with  the  lining  membrane  of  the  pharyngeal  cavity. 

Its  deep  face  is  separated  by  the  periosteum  or  perichondrium,  from  the 
bony  or  cartilaginous  walls  on  which  it  is  spread ;  and  it  is  united  to  the 
two  precited  layers,  this  union  being  closest  where  it  is  thinnest,  although 
it  can  always  be  easily  distinguished  from  these  two  fibrous  layers*  through- 
out the  whole  extent  of  the  nasal  fossa.  The  free,  or  superficial  face,  presents 
numerous  glandular  orifices,  and  is  constantly  covered  by  an  abundance  of 
mucus,  that  prevents  the  desiccation  to  which  this  surface  is  exposed  by 
the  incessant  movement  of  air  over  it. 

Structuke. — The  organisation  of  the  pituitary  membrane  resembles 
that  of  other  mucous  membranes,  but  it  also  presents  some  diflerences 
according  as  to  whether  it  is  examined  near  the  nostrils  or  deeper  in 
the  cavities.  It  is  also  usual  to  divide  it  into  two  portions  :  the  olfactory 
mucous  membrane,  which  covers  the  upper  part  of  the  ethmoidal  turbinated 
bone  and  cells ;  and  the  Schneiderian  memhiane  covering  the  inferior  two- 
thirds  of  the  nasal  cavities. 

The  corium  oi'  the  Schneiderian  membrane  is  thick,  soft,  spongy,  and 
rose-coloured,  and  contains  a  large  number  of  vessels  and  glands.  The 
latter  are  mucous,  or  racemose  glands,  and  are  extremely  abundant  in  the 
layer  covering  the  septum  of  the  nose,  as  well  as  at  the  inner  face  of  the 
cartilaginous  appendices  of  the  turbinated  bones ; 
though  they  are  rare   or    altogether  absent  on   the  Fig.  225. 

external  face  of  the  latter.  The  ejnthelium  is  ciliated 
and  stratified,  the  deeper  cells  being  round,  those  on 
the  surface  columnar. 

The  olfactory  mucous  membrane  differs  from  the 
preceding  by  its  greater  thinness,  its  delicateness,  its 
slightly  yellow  tint,  and  the  cliaracter  of  its  epithe- 
lium. The  corium  contains  straight  or  slightly-con- 
torted tubular  glands — the  glands  of  Bowman.  The 
epithelium  is  columnar  and  stratified,  and  readily 
changes ;  in  animals  it  is  destitute  of  cilia.  The 
deeper  cells  contain  some  yellowish  pigment  granules. 
Schultze  describes  as  olfactory  cells,  certain  fusiform 
elements  which  he  considers  as  concerned  in  filfaction. 
These  cells  have  two  prolongations :  a  deep  one, 
which  is  connected  with  the  fibres  of  the  olfactory 
nerve ;  and  a  superficial,  tliat  enters  between  the 
epithelial  cells  and  tends  to  approach  the  free  surface 
of  the  membrane. 

(The  "  olfactory  cells  "  are  than,  rod-like  bodies 
(Fig.  225,  b),  presenting  varicose  enlargements  which 
are  connected  with  processes  of  deeper-seated  nerve- 
cells.  The  epithelial  cylinders  proper  (d,  e)  are 
related  at  their  bases  with  the  septa  of  connective 
tissue  belonging  to  the  sub-epithelial  glandular  layer, 
and  are  probably  in  communication  with  the  olfactory 
cell.  Schultze  describes  another  set  of  epithelial 
cells  (a)  as  terminating  externally  by  truncated  flat  surfaces,  and  to  all 


CELLS  OF  THE  OLFACTORY 
MUCOUS  MEMBRANE. 

a,  b,  c,  After  Schultze , 
d,  e,  f,  After  Lockhart 
Clarke. 


446 


THE  BESPIBATOBY  APPAEATVS  IN  MAMMALIA. 


appearance  not  covered  by  any  membrane,  apart  from  the  contents  of  the  cell, 
which  are  a  yellow,  granular  proto-iilasma  surrounding  an  oval  nucleus  lying 
in  colourless  protoplasma.  The  extremity  of  these  cells  is  thin,  and  they 
can  be  traced  inwards  until  they  expand  into  a  flat  portion  that  sends  off  pro- 
cesses which  apj)ear  to  be  continuous  with  the  fibres  of  the  submucous 
connective  tissue.  Similar  cells  (c)  are  found  towaxxls  the  margin  of  the 
true  olfactory  region,  but  these  have  a  band  at  their  free  extremity,  which  is 
also  provided  with  a  circle  of  cilia.) 

The  pituitary  membrane  receives  its  blood  by  the  ophthalmic  and  nasal 
arteries ;  it  is  returned  by  the  large  anastomosing  veins  which  form,  in  the 
deep  layer,  a  long,  close,  and  magnificent  j)lexus  that  terminates  in  the 
satellite  vein  of  the  nasal  artery.  This  i^lexuous  arrangement  is  so  marked  at 
certain  points — as  at  the  appendices  of  the  turbinated  bones,  that  it  gives  the 
mucous  membrane  somewhat  the  ajipearance  of  erectile  tissue.  It  will  be 
understood  that  in  fiivouring  the  stagnation  of  the  blood,  this  arrangement 
predisposes  to  haemorrhage. 

The  lymphatics  of  the  pituitary  membrane  could  not  be  injected  for  a 
long  time,  neither  in  man  nor  animals ;  and  this  led  several  anatomists  to 
deny  their  existence.  Nevertheless,  they  do  exist,  and  form  a  fine  sui)erficial 
network  on  the  septum  of  the  nose,  the  turbinated  bones,  and  the  meatuses. 
The  trunks  passing  from  it  go  to  the  submaxillary  glands. 

The  nerves  of  this  membrane  are  numerous,  and  are  derived  from  the 
first  and  fifth  pairs,  and  from  Meckel's  ganglion.  The  ramifications  of  the 
olfactory  nerve,  on  emerging  from  the  apertures  of  the  cribriform  plate  of 
the  ethmoid  bone,  j^ass  to  the  inner  and  outer  walls  of  the  nasal  cavities ; 
being  destined  for  the  olfactory  mucous  membrane,  they  do  not  descend 
below  the  upper  third  of  these  cavities.  They  form  at  first  a  close  plexus, 
and  afterwards  terminate  in  a  manner  not  quite  understood.  Schultze  admits 
that  they  terminate  on  the  olfactory  cells  mentioned  above. 

The  branches  derived  from  Meckel's  ganglion  and  the  fifth  pair  are 
specially  destined  for  the  Schneiderian  membrane,  and 
are  named  the  ethmoidal  brandies  of  the  palpebro-nasal 
and  spheno-palatine  nerves.  They  endow  the  nose  with 
an  acute  degree  of  sensibility,  and  it  is  believed  that 
they  render  olfaction  more  perfect. 

(It  is  to  be  remarked  that  the  filaments  composing 
the  olfactory  plexus  differ  from  ordinary  cephalic  nerves 
in  containing  no  white  substance  of  Schwann,  and  are 
nucleated  and  finely  granular  in  texture,  resembling  the 
gelatinous  form  of  nerve-fibres.  The  surface  to  which 
they  are  limited  is  that  covered  with  the  yellowish- 
brown  ej)ithelium.) 

3.  Sinuses. 

The  sinuses  are  very  anfractuous  cavities,  excavated 
in  the  substance  of  the  bones  of  the  head,  on  the  limits  of 
FIBRES  OP  ULTIMATE   tlic  cranium  and  face,  and  around  the  ethmoidal  masses, 

^^^r'^!!^!?!    w^i^^i  ^^^^J  envelop. 

These  cavities,  diverticuli  of  the  nasal  fossae,  are 
pairs,  and  are  five  on  each  side  :  the  frontal,  super- 
maxillary,  sphenoidal,  ethmoidal,  and  inferior  maxillary  sinuses.  The  first 
four  communicate ;  the  last  is  usually  perfectly  isolated. 

Feontal  Sinus. — This  cavity,   situated  at  the  inner  side  of  the  orbit, 


Fig.  226. 


OLFACTORY 
OF  DOG. 


THE  NASAL  CAVITIES.  447 

presents  very  irregular  walls,  wliich  are  formed  by  the  frontal,  nasal,  lachry- 
mal, and  ethmoidal  bones,  and  the  superior  portion  of  the  ethmoidal 
turbinated  bone.  It  communicates  with  the  superior  maxillary  sinus  by  a 
vast  opening  made  in  a  very  thin  bony  partition.  A  thick  vertical  plate, 
often  bent  to  the  right  or  left,  but  always  imperforate,  separates  this  sinus 
from  that  of  the  opposite  side. 

SuPERiOK  Maxillary  Sinus. — Channeled  beneath  the  orbit,  between  the 
maxillary,  zygomatic,  ethmoid,  and  lachi'ymal  bones,  this  diverticulum  is  the 
largest  of  all,  and  is  divided  into  two  compartments  by  the  maxillo-dental 
canal,  which  traverses  it.  The  internal  compartment  constitutes  a  kind  of 
shallow  cavity,  continuous  with  the  sphenoidal  sinus,  and  presents  a  narrow 
slit,  which  penetrates  to  the  ethmoidal  sinus.  The  external  compartment 
is  separated,  in  front,  from  the  maxillary  sinus  by  a  partition  which  M. 
Goubaux  has,  contrary  to  the  generally-received  opinion,  demonstrated  to  be 
imperforate  at  all  periods  of  life ;  though  he  has  sometimes  found  it  so  thin 
as  only  to  consist  of  two  mucous  layers  laid  against  each  other.  This 
compartment  is  prolonged  backwards  into  the  maxillary  protuberance,  and 
the  roots  of  the  two  last  molars  project  into  its  anterior. 

Sphenoidal  Sinus. — This  is  the  smallest,  after  that  ot  the  great 
ethmoidal  cell.  Formed  by  the  sphenoid  and  palate  bones,  this  cavity  is  very 
irregular,  and  is  subdivided  by  incomplete  septa  into  several  compartments, 
which  may  be  always  reduced  to  two :  an  anterior,  comprised  between  the 
palatine  laminae ;  the  other  posterior,  hollowed  in  the  body  of  the  sphenoid 
bone.  In  contact,  on  the  median  line,  with  the  sinus  of  the  opposite  side, 
it  is  separated  from  it  by  a  twisted  plate,  which  is  constantly  perforated,  even 
in  young  animals. 

Ethmoidal  Sinus. — By  this  name  is  designated  the  internal  cavity  of  the 
large  ethmoidal  cell,  which  constitutes  a  real  sinus,  and  which  a  narrow 
slit  brings  into  communication  with  the  superior  maxillary  sinus. 

Inferior  Maxillary  Sinus. — This  last  diverticulum  is  remarkable  because 
of  its  not  communicating  with  the  others.  Excavated  in  the  supermaxillary 
bone,  and  separated  from  the  superior  sinus  by  the  imperforate  septum 
previously  mentioned,  it  is  divided,  like  the  latter  cavity,  into  two  compart- 
ments :  an  internal,  prolonged  into  the  superior  cavity  of  the  maxillary 
turbinated  bones ;  and  an  external,  the  smallest,  showing  the  roots  of  the 
fourth  molar,  rarely  those  of  the  third.  It  does  not  d-iscend,  as  Rigot  has 
asserted,  above  the  three  front  molars ;  but  supposing  the  head  to  be  vertical, 
it  does  not  extend,  in  the  adult  Horse,  beyond  the  extremity  of  the  maxillary 
ridge,  in  front  of  which  it  would  be  necessary  to  trepan,  in  order  to  arrive 
at  its  interior. 

Communicating  Orifice  of  the  Sinuses  with  the  Nasal  Fossa. — All 
the  sinuses  of  one  side  communicate  with  the  corresponding  nasal  fossa  by 
the  curved  slit  which  has  been  observed  at  the  bottom  of  the  middle  meatus. 
This  slit  penetrates  the  superior  maxillary  sinus,  under  the  septum  that 
separates  it  from  the  frontal  sinus ;  it  also  enters  the  inferior  maxillary 
sinus,  which  thus  communicates  solely  with  the  nasal  cavity,  wliile  the 
other  diverticuli  open  in  common  into  this  cavity  through  the  medium  of 
the  superior  maxillary  sinus. 

Mucous  Membrane  of  the  Sinuses. — In  entering  the  sinuses  to  cover 
their  walls,  the  pituitary  membrane  becomes  extremely  thin,  and  loses  its 
great  vascularity ;  it  is  applied  immediately  to  the  bones,  and  serves  as  a 
periosteum. 

Development  of  the  Sinuses. — These  cavities  begin  to  be  developed  in 


448  TEE  EESPIEATOEY  APPARATUS  IN  MAMMALLi. 

the  fcetus,  and  are  gradually  hollowed  in  the  thickness  of  the  bones  which 
concur  to  form  them.  They  increase  during  the  animal's  lifetime,  by  the 
thinning  of  the  bony  plates  inclosing  or  partitioning  them,  and  particularly 
by  the  growth  of  the  superior  molar  teeth,  whose  roots  project  into  these 
cavities.  The  formation  of  the  inferior  maxillary  sinus  is  more  tardy  than 
the  others ;  though  it  is  not  so  late  as  seven  or  eight  years,  as  the  majority  of 
Veterinary  Anatomists  have  asserted.  M.  Goubaux  has  proved  that  the  sinus  is 
already  present  at  six  months  old  ;  and  in  a  head  which  has  been  for  several 
years  in  the  museum  of  the  Lyons  School,  and  which  belonged  to  a  foal  of 
very  small  stature,  about  a  year  old,  this  sinus  is  seen,  in  its  external  part, 
to  be  already  1^  inches  in  depth,  and  8-lOths  of  an  inch  in  width. 

Functions  of  the  Sinuses. —  Have  the  sinuses  or  diverticuli  of  the  nasal 
cavities  the  same  uses  as  these  cavities?  It  is  probable,  although  not 
absolutely  certain.  There  is  nothing  to  prove  that  they  have  anything  to  do 
with  respiration  or  olfaction  ;  and  it  would  seem  that  their  exclusive  function 
is  to  give  increased  volume  to  the  head  without  increasing  its  weight,  and 
in  this  way  to  furnish  wide  surfaces  of  insertion  for  the  muscles  attached 
to  this  bony  region— these  cavities  being  all  the  more  ample  as  the  muscles 
are  large  and  numerous. 

DIFFERENTIAL   CHARACTERS   OF   THE  NASAL   CAVITIES   IN   OTHER   THAN   SOLIPED  ANIMALS. 

1.  Nostrils  — In  the  Ox,  the  nostrils,  placed  on  each  side  of  the  muffle,  are  narrower 
anfl  less  movahle  than  in  the  Horse.  (The  superior  extremity  of  the  ala  is  not  horizontal ; 
the  inferior  is  diviiled  into  two  branches.) 

In  the  Puj,  the  end  of  tlie  nose  constitutes  the  snout  (rostrum  suis),  whose  anterior 
surface,  plane  and  orbicular,  shows  the  external  orifices  of  the  nostrils.  This  snout,  a 
veritable  tactile  organ  employed  by  tlie  animal  to  dig  up  the  ground,  is  covered  by  a 
dark-coloured  skin,  kept  damp  by  a  humid  secretion,  like  the  muffle  of  the  Ox.  It  has 
for  a  base  the  scoopmg-hone,  a  particular  piece  situated  at  the  extremity  of  the  nasal 
septum,  and  enveloped  by  a  layer  of  cartilage  which  extends  aroimd  the  no.strils.  It  is 
easy  to  distinguish  two  symmetrical  halves  in  this  bone,  which  evidently  represent  the 
two  cartilaginous  pieces  in  the  nose  of  Solipeds. 

In  the  Bog,  the  end  of  the  no.se  forms  a  salient  region,  which  is  roughened,  naked, 
usually  dark-coloured,  damp,  and  sometimes  divided  by  a  median  groove ;  in  this  region 
the  nostrils  are  pierced,  their  form  resembling  two  commas  opposed  to  each  other  by  their 
convexities.  The  cartilaginous  framework  sustaining  these  orifices  is  not  composed  of 
separate  pieces,  but  is  only  a  dependance  of  the  median  septum  and  the  appendages  of 
the  tm-binated  bones. 

The  same  considerations  apply  to  the  nostrils  of  the  Cat  with  the  exception  of  the 
colour  of  the  integument,  which  is  nearly  always  of  a  ro.sy  hue,  like  the  mucous  surfaces. 

2.  Nasal  Cavities. — The  nasal  fossaj  of  the  Ox,  Sheep,  and  Goat  are  distinguished  by 
the  presence  of  a  third  turbinated  bone— the  olfactory  antrum,  andliy  the  commrmication 
existing  between  them,  posteriorly,  above  the  inferior  border  of  the  vomer.  We  have 
already  seen  that  in  these  animals,  as  in  those  yet  to  be  mentioned,  the  canal  of  Jacobson 
completely  traverses  the  palatine  arch. 

In  tlie  Pig,  the  nasal  fossaj  are  long  and  narrow.  They  are,  on  the  contrary,  very 
short  in  the  Dog  and  Cat,  and  the  internal  cells  of  the  tinbinated  bones,  remarkable 
for  their  number  and  complexity,  all  communicate  with  the  proper  nasal  I'ossaj,  without 
concurring  in  the  formation  of  the  sinuses. 

3.  Sinuses. — In  the  Ox,  the  frontal  sinuses  are  prolonged  into  the  bony  cores  which 
support  the  horns,  and  into  the  parietal  and  occijjital  bones  ;  they  therefore  envelop,  in 
a  most  complete  manner,  the  anterior  and  superior  part  of  the  cranium,  and  form  a 
double  wall  to  this  bony  receptacle.  They  are  extremely  diverticulated,  and  do  not 
communicate  with  those  of  the  great  maxillary  bones.  They  u.sually  open,  on  each  side, 
into  the  nasal  cavities  by  four  apertures  pierced  at  the  base  of  tiie  great  ethmoidal  cell. 
According  to  Girard,  three  of  these  orifices  lead  to  special  comjiartments,  isolated  from 
one  another,  and  grouped  around  the  orliit ;  in  consequence  of  which  these  diverticuli  of 
the  frontal  sinuses  are  designated  the  orbital  sinuses. 

This  author  has  denied  the  presence  of  sphenoidal  sinuses ;  but  they  exist,  although 
email,  and  are  in  communication  with  the  preceding. 


TEE  LARYNX.  449 

The  sinus  of  the  great  ethmoidal  cell  comports  itself  as  in  the  Horse. 

There  is  only  one  pair  of  maxillary  sinmes,  which  are  very  large,  anil  partitioned  into 
two  compartments  by  a  plate  of  bone,  that  bears  at  its  superior  border  the  siipermaxillo- 
deutal  canal,  like  the  superior  maxillaiy  sinus  of  .Solipeds.  The  external  or  maxillary 
compartment  is  prolonged  into  the  lachrymal  {jrotuberance ;  the  internal  occupies  the 
thickness  of  the  palatine  arch.  A  wide  orifice  at  the  base  of  the  maxillary  turbinated 
bone  aflbrds  a  connnunication  between  this  sinus  and  the  nasal  fossa. 

In  the  Sheep  and  Goat,  there  exists  a  similar  arrangement  of  the  sinuses  of  the 
head;  but  these  cavities  are  much  less  spacious  tlian  in  tlie  Ox;  the  frontal  sinus  ia 
particular,  does  not  extend  beyond  tlie  superior  border  of  the  frontal  bone. 

In  the  Pi(j.  these  latter  sinuses  are  prolonged  into  the  parietal  bones ;  though  they 
are  far  from  olfering  the  same  extent  as  in  the  smaller  Ruminants.  It  is  tlie  same  with 
the  others ;  they  present  an  arrangement  analogous  to  those  of  the  Sheep  and  Goat. 

In  the  Dog  and  Cat,  there  are  only,  on  each  side,  a  maxillary  and  a  frontal  sinus. 
The  first  scarcely  merits  notice ;  and  the  second,  a  little  more  tleveloped,  opens  into  the 
nasal  cavity  by  means  of  a  small  aperture  situated  near  the  middle  septum  of  the  two 
frontal  sinuses. 

(Leyh  states  that  the  Carnivora  have  no  maxillary  sinus  ;  consequently,  the  sphenoidal 
sinus  communicates  below  with  the  nasal  foss£e.) 

COMPAPwlSON  OF   THE   NASAL   CAVITIES   IX   MAX   VflTH  THOSE   OF   AXIMALS. 

The  external  orifices  of  the  nasal  cavities  of  Man  are  called  nostrils  ;  these  are  fla.,..encd 
transversely,  and  prolonged  in  front  of  the  lobule  of  the  nose;  their  external  face  or  ala 
is  concave  and  movable.  They  are  lined  internally  by  a  membrane  that  holds  a  middle 
place  between  the  skin  and  mucous  membranes  ,  it  has  a  number  of  little  hairs,  called 
vihrissx. 

The  cavities  or  nasal  fossseoSer  nothing  paiticular;  as  in  animals,  they  show  a  superior, 
middle,  and  inferior  meatus.  On  their  floor,  in  front,  is  seen  tlie  superior  orifice  of  the 
incisive  foramen,  which  corresponds  to  the  commencement  of  Jacobson's  canal.  The 
pituitary  membrane  has  a  squamous  epithelium  in  its  olfiictory,  as  on  its  Schneiderian 
portion.  At  the  bottom  of  the  nasal  cavities  and  the  upper  part  of  the  pharynx,  is  a 
kind  of  diverticulum  named  the  postenor  naves;  it  has  been  already  alluded  to  when 
speaking  of  the  pharynx. 

The  sinuses  are :  1,  The  sjjhenoidal  sinus  and  the  posterior  ethmoidal  cells,  that  open 
beneath  the  roof  of  the  nasal  fossse ;  2,  The  middle  ethmoidal  cells,  opening  into  the 
superior  meatus;  3,  The  -anterior  ethmoidal  cells,  and  frontal  and  maxillary  sinuses, 
communicating  with  the  middle  meatus.  All  these  sinuses  have  a  proper  communicating 
orifice  with  the  nasal  cavities. 

THE   AIR   TUBE    SUCCEEDING   THE    NASAL   CAVITIES. 

This  single  tube  comi^rises :  the  lari/nx,  which  commences  the  trachea ; 
the  latter  forms  the  body  or  middle  portion,  the  bronchice  terminating  it. 

.  Larynx.     (Figs.  227,  228,  229.) 

Preparation.— I.  Make  a  longitudinal  section  of  the  head,  in  order  to  study  tho 
general  disposition  of  the  larynx  (Fig.  224'.  2.  Isolate  the  cartilages,  to  examine 
their  external  conformation.  3.  Remove  the  muscles  from  a  third  larynx,  to  show  the 
mode  of  articulation  of  the  various  cartilages  Figs.  227,  228\  4.  Prepare  the  muscles  in 
conformity  with  the  indications  furnished  by  a  glance  at  figure  22S).  5.  Remove  a  larynx 
as  carefnily  as  possible,  so  as  not  to  injure  the  walls  of  the  pharynx,  in  order  to  study 
the  interior  of  the  organ,  and  especially  its  pharyngeal  opening. 

Form — Situation. — The  larynx  forms  a  very  short  canal,  which  gives 
passage  to  the  air  during  respiration,  and  is  at  the  same  time  the  organ 
of  the  voice. 

It  is  a  cartilaginous  box,  depressed  on  each  side,  and  open  from  one  end  to 
the  other  ;  the  anterior  orifice  being  situated  at  the  bottom  of  the  pharyngeal 
cavity,  and  the  posterior  continuous  with  the  trachea. 

This  apparatus,  situated  in  the  intermaxillary  space,  is  suspended 
between  the  two  cornua  of  the  os  hyoides,  and  fixed  to  the  extremities  of 
these  appendages  by  one  of  its  constituent  pieces.     It  serves  to  support  the 


4  50  THE  HESPIRA  TOE  Y  APPARA  TUS  IN  MAMMA  LI  A . 

pharynx,  and  by  means  of  the  walls  of  the  latter  is  attached  to  the  cir< 
cumference  of  the  posterior  openings  of  the  nasal  cavities. 

In  order  to  facilitate  description,  this  brief  notice  of  its  form,  situation, 
general  relations,  and  mode  of  attachment  will  be  followed  by  a  notice  oi 
its  structure  ;  afterwards,  the  study  of  its  external  and  internal  surfaces  will 
receive  attention. 

Structure  of  the  Larynx. — It  comprises  in  its  structure :  1,  A  carti- 
laginous frameworJc,  composed  of  five  pieces;  2,  Muscles  which  move  these 
pieces ;  3,  A  mucous  membrane  spread  over  the  inner  surface  of  the  organ ; 
4,  Vessels  and  nerves. 

1.  Cartilaginous  fi-ameivorh  of  the  larynx. — In  this  we  find  :  three  single 
median  cartilages,  the  cricoid,  thyroid,  and  epiglottis;  and  two  lateral 
cartilages,  the  arytenoid.     All  are  movable  one  upon  the  other. 

Cricoid  Cartilage. — This  cartilage,  as  its  name  indicates  (KptKos,  elSo?, 
like  a  ring),  is  exactly  like  a  ring  with  a  bezel  looking  upwards.  Depressed 
on  each  side,  but  all  the  less  as  the  animal  has  its  respiratory  apparatus 
well  developed,  this  ring  offers  two  faces,  and  tioo  borders  or  circumferences. 
The  internal  face  is  smooth  and  covered  by  mucous  membrane.  The  external 
face  is  provided,  in  the  middle  of  the  widened  portion  forming  the  bezel  with 
a  little  eminence  more  or  less  prominent,  elongated  in  the  form  of  a  crest, 
and  separating  the  two  posterior  crico-arytenoid  muscles,  to  which  it  gives 
attachment,  from  each  other.  On  the  sides  of  this  bezel  are  two  small,  articular, 
concave  facets,  which  correspond  to  the  branches  of  the  thyroid  cartilage. 
Notliino'  remarkable  is  to  bo  noted  for  the  remainder  of  the  extent  of  this  face. 
The  superior  ■  circumference,  comjirised  laterally  between  the  two  branches  of 
the  thyroid  cartilage,  is  hollowed  out  in  the  narrow  part  opposite  the  bezel, 
where  its  shows  two  lateral  convex  articular  facets  for  articulation  with  the 
arytenoid  cartilages.  The  inferior  circumference  responds  to  the  first  ring 
of  the  trachea ;  it  offers  a  small  notch,  often  double,  on  the  middle  of  the 
bezel. 

Thyroid  Cartilage  (^upcds,  cISos,  like  a  shield). — This  is  composed 
of  two  lateral  plates,  which  have  the  form  of  an  obliquangular  parallelo- 
gram, and  are  united  at  their  anterior  extremity  to  form  a  thick  constricted 
part  which,  in  Veterinary  Anatomy,  is  named  the  body  of  the  thyroid.  This 
body  is  smooth  on  its  inferior  face,  where  it  is  covered  by  the  terminal 
extremity  of  the  subscapulo-hyoideii  muscles.  On  its  siiperior  face  is 
an  obtuse,  rounded,  and  irregular  protuberance,  on  which  the  epiglottis 
articulates. 

The  plates,  lateral  branches,  or  alee  of  the  thyroid  present  tico  faces,  two 
borders,  and  two  extremities.  The  external  face,  slightly  convex,  is  covered . 
by  the  hyo-thyroideus  and  thyro-pharyngeus  muscles.  The  internal  face, 
slightly  concave,  is  covered,  near  the  superior  border,  by  the  pharyngeal 
mucous  membrane ;  for  the  remainder  of  its  extent  it  responds  to  the  thyro- 
arytenoid and  lateral  crico-arytenoid  muscles. 

The  superior  border  is  divided  by  a  small  prolongation  into  two  parts : 
an  anterior,  giving  attachment  to  the  thyro-hyoid  membrane ;  the  other 
posterior,  into  which  is  inserted  the  pharyngo-staphyleus  (palato-pharyngeus) 
muscle.  This  appendix,  the  great  thyroid  cornu  of  Man,  forms  one  of  the 
obtuse  angles  of  the  parallelogram  represented  by  each  lateral  plate  of  the 
thyroid  cartilage  ;  it  is  united  to  the  extremity  of  the  hyoid  cornu  ;  and  at 
its  base  is  an  opening,  or  deep  notch,  through  whicli  passes  tlie  superior 
laryngeal  nerve.  The  inferior  border  is  also  divided  into  two  parts  by  the 
second  obtuse  angle  of  the  cartilage  :  the  anterior  part  forms,  with  that  of 


THE  LARYNX.  451 

the  opposite  plate,  a  receding  angle  occupied  by  the  crico-thyroid  membrane ; 
the  posterior  gives  attachment  to  the  crico-thyroid  muscle.  The  extremities 
constitute  the  acute  angles  of  the  thyroid  plate.  The  anterior  is  confounded 
with  that  of  the  opposite  branch,  to  form  the  body  of  the  cartilage.  The 
posterior,  slightly  curved  downwards,  is  terminated  by  a  small,  convex 
diarthrodial  facet,  which  articulates  with  the  concave  facets  of  the  external 
lace  of  the  cricoid  cartilage. 

The  thyroid  cartilage  is  frequently  partially,  or  even  entirely,  ossified. 

Epiglottis. — This  piece  forms  a  soft  and  flexible  appendix,  shaped  like 
a  sage-leaf;  inferiorly,  it  circumscribes  the  entrance  to  the  larynx,  and 
is  bent  over  it,  so  as  to  close  it  hermetically  when  the  alimentary  bolus  is 
traversing  the  pharyngeal  vestibule. 

This  cartilage  has  two  faces,  two  lateral  borders,  a  ha^e,  and  a  summit. 
The  anterior  face  is  convex  from  side  to  side,  concave  from  above  to  below, 
and  covered  by  the  mucous  membrane  of  the  j)harynx ;  it  gives  attachment 
to  the  hyo  epiglottidean  muscle. 

H^he  posterior  face  shows  an  inverse  configuration,  and  is  covered  by  the 
lining  membrane  of  the  larynx,  which  is  perforated  by  glandular  orifices. 
The  borders  ofier  a  free  portion,  which  aids  in  circumscribing  the  entrance 
to  the  larynx;  as  well  as  an  adherent  part  fixed  to  the  arytentiid  cartilage  by 
means  of  a  mucous  fold,  and  made  irregular  by  the  little  cartilaginous  bodies 
which  are  superadded  to  it.  (These  are  the  cuneiform  cartilages,  or 
cartilages  of  Wrisberg,  placed  in  the  aryteno-epiglottidean  fold  of  mucous 
membrane  which  extends  from  the  apex  of  the  arytenoid  cartilage  to  the  side  of 
the  epiglottis.)  The  base  is  thick,  and  articulated  with  the  middle  part  of 
the  thyroid ;  it  gives  origin,  posteriorly,  to  two  lateral  prolongations,  which 
pass  to  the  inferior  border  of  the  arytenoids,  but  usually  without  joining 
these. 

The  summit  unites  the  iree  portion  of  both  borders,  and  is  thrown  forwards 
on  the  upper  face  of  the  soft  i:»alate  (Fig.  174,  9). 

Arytenoid  Cartilages. — These  two  pieces  have  been  so  designated  from 
their  resemblance,  when  approximated,  to  the  mouih  of  a  pitcher  (upvTaLva, 
cT8os,  nice  a  intcher).  They  are  situated  in  front  of  the  cricoid, 
above  the  entrance  to  the  larynx;  each  afiects  an  irregular  quadrilateral 
form,  and  presents  for  study  two  faces  and  four  borders.  The  internal  face 
is  smooth,  almost  flat,  and  lined  by  the  laryngeal  mucous  membrane. 
The  external  face  is  divided  by  a  ridge  into  two  portions  :  a  superior,  covered 
by  the  arytenoid  muscle  ;  and  an  inferior,  giving  attachment  to  the  thyro- 
arytenoid and  lateral  crico-arytenoid  muscles.  The  superior  border  is  concave, 
and  joined  to  that  of  the  opposite  cartilage.  Tlie  inferior  border  gives 
attachment,  posteriorly,  to  the  vocal  cord.  The  anterior  border,  thick  and 
convex,  and  covered  by  the  mucous  membrane,  circumscribes,  superiorly 
and  laterally,  the  entrance  to  the  larynx ;  it  is  in  joining  above,  with  the 
homologous  border  of  the  other  arytenoid  cartilage,  that  the  pitcher- beak 
already  mentioned  is  formed.  The  posterior  border  projects  into  the  larynx 
by  its  inferior  portion  ;  superiorly,  this  border  is  very  thick,  and  is  hollowed 
by  a  small  articular  facet,  which  responds  to  the  anterior  facet  of  the  bezel 
of  the  cricoid.  Above,  and  to  the  outside  of  this  facet,  is  a  very  prominent 
tubercle  which  terminates  behind  the  crest  of  the  external  face,  and  gives 
attachment  to  the  posterior  crico- arytenoid  muscle. 

Articulations  of  the  Laryngeal  Cartilages  (Figs.  227,  228), — -These 
articulations  are  of  the  simplest  kind.     They  are  as  follows : 

A.    The   thyroid   cartilage   is  joined   to    the  os  hyoides  :    ] ,    At    the 


452 


TEE  BESPIBATORY  APPARATUS  IN  MA3IMALIA. 


extremities  of  the  cornua,  by  means  of  a  short  ligament  interposed  between 
that  extremity  and  the  appendix  of  the  superior  border  of  the  thyroid ;  2, 
To  the  whole  extent  of  the  hyoid  concavity,  by  an  elastic  membrane — the 
thyro-hyoid  membrane,  attached  to  the  body  of  the  thyroid  cartilage  and  the 
superior  border  of  the  lateral  plates  of  that  cartilage  (Fig.  228,  4). 


Fi2.  227. 


Fis  228. 


SUPERIOR   FACE.  INFERIOR   FACE. 

CARTILAGINOUS   PIECES   OF   THE   LARYNX,   MAINTAINED   IN   THEIR   NATURAL   POSITION 
BY    THE    ARTICULAR    LIGAMENTS. 

a,  Cricoid  cartilage ;  h,  b.  Arytenoid  cartilages  ;  c,  Body  of  the  thyroid  ;  c',  c',  Lateral 
plates  of  the  thyroid ;  d,  Epiglottis ;  e,  Body  of  the  hyoid  ;  /,  Trachea. — 1, 
Crico-arytenoid  articulation ;  2,  Capsule  of  the  crico-thyroid  articulation ;  3, 
Crico-thyroid  membrane  ;  4,  Thyro-hyoid  membrane  ;  5,  Crico-trachealis  ligament. 

B.  The  thyroid  cartilage  articulates  with  the  cricoid  by  two  small 
arthrodi83,  which  unite  the  posterior  extremities  of  the  branches  of  the  first 
cartilage  with  the  facets  on  the  external  face  of  the  second.  A  thin  external 
capsule  incloses  this  articulation  (Fig.  227,  2).  These  two  cartilages  are 
also  held  together  by  meaus  of  a  membranous  elastic  ligament — the  crico- 
thyroid membrane,  which  passes  from  the  angle  comprised  between  the  two 
branches  of  the  thyroid  to  the  anterior  notch  of  the  cricoid  (Fig.  228,  3). 

C.  The  two  arytenoid  cartilages  are  united,  at  their  superior  border,  by 
the  arytenoid  muscle  and  laryngeal  mucous  membrane. 

D.  The  latter  cartilages  are  brought  into  contact  with  the  anterior  facets 
of  the  cricoid  bezel,  by  means  of  the  concave  articular  surface  of  their  posterior 
border ;  the  result  is  a  small,  but  very  movable,  arthrodial  joint,  inclosed 
by  a  thin  external  capsule  and  by  the  surrounding  muscles  (Fig.  227,  1). 

E.  These  cartilages  are  also  united  to  the  thyroid  through  tlie  medium  of 
the  vocal  cords.  These  are  two  elastic  bands  which  project  within  the 
larynx,  and  between  them  include  the  triangular  space  termed  the  glottis ; 
their  internal  face  is  covered  by  the  mucous  membrane  of  the  larynx ;  the 
thyro-hyoid  muscles  envelop  their  external  face  ;  their  inferior  extremity  is 
fixed  into  the  crico-thyroid  membrane,  and  the  angle  of  the  thyroid  cartilage ; 


THE  LARYNX.  453 

the  superior  is  attaclied  to  the  inferior  border  of  the  arytenoid  cartilage, 
towards  the  angle  which  separates  this  from  the  posterior  border.  The 
articuhitiou  of  sounds  is  jirincipally  due  to  the  vibration  of  these  cords, 

F.  The  epiglottis  is  fixed  by  amphiarthrosis  to  the  body  of  the  thyroid 
cartilage,  by  means  of  elastic  fasciculi  mixed  with  fat,  which  pass  from  the 
base  of  the  first  to  the  upper  face  of  the  second.  It  is  not  rare  to  find  among 
these  fasciculi  small  synovial  bursas. 

G.  The  epiglottis  is  united,  laterally,  to  the  inferior  border  of  the 
arytenoids,  through  the  medium  of  the  two  mucous  folds  already  noticed,  in 
the  substance  of  which  are  the  cartilaginous  prolongations  annexed  to  the 
base  of  this  fibro-cartilage.  These  prolongations  circumscribe,  anteriorly, 
the  ventricles  of  the  larynx,  and  are  sometimes  designated  the  superior  vocal 
cords :  a  name  we  rarely  give  them,  as  they  do  not  merit  it. 

H.  Finally,  the  first  ring  of  the  trachea  is  attached  to  the  cricoid 
cartilage  by  a  circular  elastic  membrane. 

All  of  these  articulations  have  neither  the  same  importance  nor  mobility. 
The  kind  of  movements  they  permit  is  easily  understood,  aud  they  are  suf- 
ficiently indicated  in  the  description  of  the  muscles  which  execute  them. 

It  is  sufiicient  here  to  state,  that  these  movements  may  either  produce 
the  shortening  or  elongation  of  the  larynx,  its  tlilatation  or  contraction  in  a 
transverse  direction,  or  the  occlusion  of  its  anterior  opening. 

2.  Muscles  of  the  larynx.  —  The  laryngeal  ajiparatus  is  elevated  or 
depressed  with  the  hyoid  bone,  which  it  follows  in  all  its  movements.  It 
is  also  moved  by  proper  muscles,  which  either  produceits  total  displacement, 
or  cause  the  several  pieces  of  its  cartilaginous  framework  to  play  upon  each 
other.  Among  these  muscles  there  are  three  extrinsic  :  the  i>terno-tlujroideus, 
lujo-thjroideus,  and  the  hyo-epiglottideus.  The  others  are  intrinsic,  or 
attached  in  their  origin  and  termination  to  the  different  pieces  of  the  larynx  ; 
they  are  :  the  crico-thyroid,  posterior  crico-aryfenoid,  lateral  crico-arytenoid, 
thyro-ariitenoid,  and  the  arytenoideus  muscles.  All  are  pairs,  except  the  last 
and  the  hyo  epiglottic! eus. 

Sterxo-thyroideus. — (See  page  198.) 

Hyo-thyroideus. — This  is  a  ^-ide,  triangular  muscle  formed  entirely  of 
muscular  fasciculi,  which  originate  from  the  whole  extent  of  the  hyoid 
cornu,  and  terminate  on  the  external  face  of  the  thyroid  ala ;  the  most 
inferior  are  longest.  This  muscle  covers  the  thyroid  cartilage  and  the 
thyro-hyoid  membrane.     It  is  covered  by  the  maxillary  gland. 

In  contracting,  this  muscle  brings  the  thyroid  cartilage  within  the  branches 
of  the  hyoid  bone,  and  in  this  way  carries  the  larynx  forward  and  upward. 

Hyo-epiglottidecs. — By  this  name  is  designated  a  small  cylindrical 
fasciculus,  whose  fibres  are  buried  in  the  middle  of  a  mass  of  adipose  tissue, 
and  which  extend  from  the  superior  face  of  the  body  of  the  hyoid  bone  to  the 
antero-inferior  face  of  the  epiglottis.  Partly  covered  by  the  mucous 
membrane  of  the  pharynx,  this  muscle  concurs  in  restoring  the  epiglottis 
to  its  normal  position  after  the  passage  of  the  alimentary  bolus.  But  it  is 
also  necessary  to  state  that  the  epiglottis  is  carried  forward  more  particularly 
by  its  own  proper  elasticity,  as  well  as  that  of  the  ligamentous  fasciculi 
which  attach  it  to  the  thyroid  cartilage. 

Crico-thyroideus  (Fig.  229,  8). — This  small  muscle,  applied  to  the 
external  side  of  the  cricoid  cartilage,  is  elongated  from  above  to  below, 
and  composed  of  strongly  tendinous  fibres  which  cross,  more  or  less,  the 
general  direction  of  the  muscle.  They  arise  from  the  above-named  cartilage, 
and  pass  to  the  posterior  border  of  the  thyroid  plate. 
32 


454 


THE  BE8PIRAT0RY  APPARATUS  IN  MAMMALIA. 


Fia.  229 


The  crico-thyroideus  shortens  the  larynx,  in  bringing  together  the  two 
cartilages  into  which  it  is  inserted. 

Posterior  Crico-arytenoideus  (Fig. 
229,  7)  — This  is  the  most  powerful  muscle 
in  this  region.  Its  fibres  are  directed  for- 
wards and  outwards,  and  originate  from 
the  bezel  of  the  cricoid,  which  they  cover, 
and  from  the  median  crest  of  that  part. 
They  all  converge,  in  becoming  more  or  less 
tendinous,  towards  the  posterior  tubercle  of 
the  arytenoid  cartilage,  on  which  they  ter- 
minate. Covered  by  the  oesophagus  and 
the  crico-pharyngeal  muscular  baud,  this 
muscle  is  separated  from  that  of  the  oppo- 
site side  by  the  median  crest  of  the  cricoid 
bezel. 

The  posterior  crico-arytenoid  muscles 
dilate  the  entrance  to  the  larynx,  as  well  as 
the  glottis,  in  causing  the  arytenoid  car- 
tilages to  rotate  or  swing  on  the  cricoid 
cartilage,  and  in  separating  them  from  one 
another  by  their  anterior  and  inferior  bor- 
ders. They  act  as  a  lever  of  the  first  order. 
Lateral  Crico-arytenoideus  (Fig.  22'J, 
5).  —  A  triangular  muscle,  smaller  than 
the  preceding,  situated  between  the  thyroid 
and  arytenoid  cartilages,  and  formed  of 
tween  the  cricoid  '  cartilage  and  fasciculi  longer  in  front  than  behind  ;  these 
first  ring  of  trachea,  10;  11,  In-  originate  on  the  side  of  the  anterior  border 
fero-posterior  extremities  of  crico-  ^£  ^-^^  cricoid  cartilage,  and  are  directed 
thyroid  cartilages.  t      ^      i  •      ^  i  •  i      ^t  ^     • 

•'  *  upwards  to  terminate  outside  the  posterior 

crico-arytenoideus,  on  the  tubercle  of  the  arytenoid  cartilage. 

It  is  a  direct  antagonist  of  the  last  muscle,  and,  consequently,  a  con- 
strictor of  the  larynx. 

Thyro  ARYTENoiDETTS  (Fig.  229,  6). — Lodged  at  the  inner  face  of  the 
thyroid  ala,  this  muscle  comprises  two  fasciculi,  separated  by  the  ventricle 
of  the  glottis. 

The  anterior  fasciculus  is  a  long  and  pale  band,  originating  on  the 
internal  surface  of  the  ala  of  the  thyroid  cartilage,  near  its  receding  angle, 
and  ascending  to  the  arytenoid  cartilage,  bending  round  its  external  face  to 
join,  on  the  median  line,  the  analogous  fasciculus  from  the  opposite  side, 
mixing  its  fibres  with  those  of  the  arytenoideus.  By  its  inner  face  it  covers 
the  superior  vocal  cord  and  the  laryngeal  mucous  membrane. 

The  posterior  fasciculus,  wider  than  the  anterior,  comports  itself  in  a 
somewhat  similar  manner.  It  commences  from  behind  the  same  point,  and 
terminates  on  the  external  crest  of  the  arytenoid  cartilage ;  but  its  most 
anterior  fibres  pass  over  this  crest  and  join  the  arytenoid  muscle.  Its 
internal  face  corresponds  to  the  vocal  cord,  and  its  posterior  border  is  con- 
founded with  the  fibres  of  the  lateral  crico-arytenoideus. 

Sometimes  it  happens  that  these  fasciculi  are  not  distinct  from  each 
other,  and  exist  only  as  a  wide  muscular  band  applied  against  the  ventricle 
of  the  glottis. 

It   is  surmised   that  this  muscle  is  a  constrictor  of  the  larynx.     Its 


POSTERO-LATERAL   VIEW   OF    THE 
LARYNX 

I,  Epiglottis  ;  2,  Arytenoid  cartilages  ; 
3,  Thyroid  cartilage ;  4,  Arytenoi- 
deus muscle ;  5,  Crico-arj'ienoideus 
lateralis ;  6,  Thyro-arytenoideus ; 
7,  Crico-arytenoideus  posticus ;  8, 
Crico-thyroideus ;  9,  Ligament  be- 


THE  LARYNX.  455 

function  is  particularly  marked  in  phonation,  wten  it  modifies  the  length, 
separation,  and  tension  of  the  vocal  cords. 

Akytenoideus. —  Situated  beneath  the  pharyngeal  mucous  membrane, 
above  the  arytenoid  cartilages,  this,  the  smallest  of  the  laryngeal  muscles,  is 
composed  of  two  lateral  portions  whose  fibres  arise  from  a  median  raphe 
and,  diverging,  pass  to  the  superior  part  of  the  external  face  of  the  before- 
mentioned  cartilages,  where  they  terminate  by  becoming  inserted  into  the 
crest  dividing  that  face,  and  imiting  with  the  thyro-arytenoid  muscle. 

The  French  works  on  Veterinary  Anatomy  cite  this  muscle — we  do  not 
know  why — as  a  dilator  of  the  larynx.  Its  position  in  front  of  the  crico- 
arytenoid cartilages  sufiiciently  indicates  that  it  cannot  act  otherwise  than 
in  bringing  the  two  arytenoid  cartilages  together.  And  the  continuity  of 
a  large  number  of  its  fibres  with  those  of  the  thyro-arytenoideus,  does  not 
allow  it  to  have  any  other  action  than  that  of  this  muscle. 

3.  Mucous  membrane  of  the  larynx. — This  membrane  is  only  a  con- 
tinuation of  the  jjharyngeal  mucous  membrane,  which,  after  covering  the 
prominence  formed  by  the  opening  of  the  larynx,  is  folded  over  the  cir- 
cumference of  that  opening,  to  be  spread  on  the  posterior  face  of  the  epi- 
glottis and  the  internal  face  of  the  arytenoid  cartilages,  to  dip  into  the 
ventricles,  pass  above  the  vocal  cords,  line  the  inner  face  of  the  cricoid 
cartOage,  and,  finally,  to  be  prolonged  into  the  tracheal  tube.  Its  deep  face 
adheres  closely  to  the  parts  it  covers,  excejit  in  the  lateral  ventricles.  The 
free  face  is  perfectly  tense,  and  is  covered  with  stratified  tesselated  epi- 
theliimi  at  the  epiglottis  and  vocal  cords,  but  only  with  ciliated  epithelium 
elsewhere. 

The  glandulce  of  the  larynx  are  racemose,  and  are  numerous  on  the 
posterior  face  of  the  epiglottis,  where  they  are  lodged  in  the  minute  depres- 
sions of  the  cartilage ;  they  are  also  found  on  the  arytenoid  cartilages  and 
the  aryteno-epiglottidean  folds.  The  mucous  membrane  of  the  larynx 
possesses  an  exquisite  sensibility,  owing  to  which  admission  to  the  air- 
passage  is  denied  to  the  solid  or  liquid  alimentary  particles,  which,  dui'ing 
deglutition,  might  deviate  from  their  normal  course  and  pass  into  this 
opening.  The  slightest  touch  brings  into  play  this  sensibility,  and  deter- 
mines an  energetic  reflex  excitation  of  the  constrictor  muscles  of  the  larynx 
and  chest ;  from  this  results  the  almost  complete  occlusion  of  the  laryngeal 
tube,  and  a  violent  cough  which  expels  the  substances  whose  contact  has 
occasioned  the  irritation  of  the  membrane.  Everyone  has  experienced  the 
effects  of  this  reflex  action,  and  knows  by  experience  the  great  sensibility  of 
the  larynx. 

4.  Vessels  and  nerves. — Blood  is  carried  to  the  larynx  by  the  laryngeal 
arteries,  which  pass  between  the  cricoid  and  the  posterior  border  of  the 
thyroid  cartilages.  Their  branches  spread  over  the  ventrical  of  the  glottis 
and  the  thyi-o-arytenoid  muscle,  to  be  expended  in  the  substance  of  the 
miiscles  and  mucous  membrane.  The  terminal  ramifications  form  red 
plexuses  on  certain  parts  of  the  larynx.  The  veins  are  satellites  of  the 
arteries.     The  lymphatics  form  a  superficial  and  a  submucous  network. 

The  pneumogastric  furnishes  the  larynx  with  its  principal  nerves — the 
superior  and  inferior  laryngeal.  The  first  is  distributed  to  the  upper  part 
of  the  organ  and  to  the  entrance  to  the  glottis,  endowing  the  mucous 
membrane  with  that  high  degi-ee  of  sensibility  that  distinguishes  it.  The 
second  is  more  especially  a  motor  nerve,  and  supplies  all  the  muscles, 
except  the  crico-thyroid  muscle.  A  filament  of  the  recurrent  nerve  is 
distributed  in  the  mucous  membrane  of  the  subglottal  portion,  and  to  the 


456  THE  BESPIBATORY  APPARATUS  IN  MAMMALIA. 

inferior  border  and  inner  face  of  the  vocal  cords.  The  presence  of  nervous 
filaments,  analogous  to  those  of  the  trachea,  in  the  sub-glottal  part  of  the 
larynx  may  explain  the  difference,  well  known  to  physiologists,  that  exists 
betwefen  the  sensibility  of  the  entrance  to  the  glottis  and  that  of  the  inferior 
border  of  the  vocal  cords. 

External  Surface  of  the  Larynx. — It  is  divided  into  four  planes :  a 
superior,  inferior,  and  two  lateral.  The  superior  plane,  formed  by  the  ary- 
tenoid and  posterior  crico-arytenoid  muscles,  is  covered  by  the  pharynx 
and  oesophagus  ;  in  its  anterior  moiety,  it  is  directly  covered  by  the  pharyn- 
geal mucous  membrane. 

The  inferior  plane  presents,  from  before  to  behind,  the  thyro-hyoid 
membrane,  the  body  of  the  thyroid  cartilage,  the  crico-thyroid  membrane,  the 
inferior  part  of  the  cricoidxjartilage,  and  the  crico-trachealis  ligament.  There 
is  remarked,  laterally,  the  inferior  border  of  the  thyro-hyoid  muscle.  This 
plane  corresponds  to  the  scapulo-hyoideal  muscles,  which  entirely  cover  it. 

The  lateral  planes  exb'bit  the  external  faces  of  the  thyro-hyoid  and 
crico-thyroid  muscles,  that  of  the  cricoid  tiartilage,  and  the  alse  of  the 
thyroid.  They  also  show  the  opening  through  which  passes  the  superior 
laryngeal  nerve  ;  they  are  related  to  the  crico-  and  thyro-pharyngeal  muscles, 
as  well  as  the  maxillary  gland. 

Internal  Surface  of  the  Larynx. — -This  surface  is  divided  into  three 
perfectly  distinct  regions  :  a  middle  one,  named  the  glottis ;  a  superior,  called 
the  supraglottic  portion ;  and  an  inferior,  designated  the  subglottic  portion. 

The  glottis  [rima  glottidis)  is  a  narrow  si)ace  which  affects  the  figure  of  a 
very  elongated  isoscelated  triangle,  its  base  being  uppermost.  This  irregular 
fissure  is  comprised  between  the  elastic  structures  known  as  the  vocal  cords. 
It  is  the  narrowest  part  of  the  larynx. 

The  supraglottic  portion,  wider  than  the  glottis,  but  always  greatly 
depressed  on  each  side,  particularly  in  the  region  comprised  between  the 
arytenoids,  presents:  1,  The  two  ventricles  of  the  larynx,  lateral  excavations, 
dilated  at  the  bottom,  and  which  penetrate  between  the  anterior  border  of 
the  vocal  cords  and  the  prolongations  of  the  base  of  the  epiglottis,  insinuat- 
ing themselves  even  between  the  fasciculi  of^he  thyro-arytenoid  muscle 
(in  the  Ass  and  Mule  the  ventricles  are  proportionately  larger  than  in  the 
Horse,  and  open  close  to  the  base  of  the  epiglottis) ;  2,  The  suhepiglottic 
sinus,  a  deep  depression  at  the  base  of  the  epiglott's,  which  is  provided,  in 
the  Ass  and  Mule,  with  a  thin  membrane,  capable  of  vibrating ;  3,  The 
entrance  of  the  larynx,  or  pharyngeal  opening  of  the  cavity,  a  vast,  gaping 
aperture  of  an  oval  fi)rm,  circumscribed  by  the  anterior  border  of  the 
arytenoids  and  the  lateral  border  of  the  epiglottis,  and  making  a  remark- 
able projection  at  the  bottom  of  the  pharyngeal  space. 

The  subglottic  portion  of  the  larynx  is  the  widest  of  the  three ;  it  is 
directly  continuous  with  the  internal  canal  of  the  trachea.  In  front  is  seen 
the  prominence  formed  by  the  posterior  border  of  the  vocal  cords :  above, 
a  diffused  and  shallow  excavation,  placed  at  the  point  of  junction  of  the 
arytenoid  and  cricoid  cartilages,  and  which  is  named  the  subarytenoid  sinus. 

Functions. — As  a  tube  intended  for  the  passage  of  a  column  of  air 
during  the  act  of  respiration,  the  larynx  does  not  give  rise  to  any  very 
interesting  physiological  considerations.  It  is,  nevertheless,  worthy  of  remark 
.  that  this  organ,  in  imitation  of  the  nostrils,  dilates  or  contracts,  according 
to  the  volume  of  the  column  of  air  introduced  into,  or  expelled  from,  the 
lungs,  and  that  its  paralysis,  during  rapid  movements,  causes  an  embarrass- 
meni  in  the  respiration  which  betrays  itself  in  "roaring."     But  a  physio- 


THE  TRACHEA.  457 

logical  study  of  the  larynx  acquires  a  real  interest  v.lien  it  is  examined  with 
regard  to  the  articulation  of  sounds,  or  as  an  organ  of  phonation.  This 
study,  however,  does  not  come  within  our  province ;  though  what  has  been 
said  concerning  the  vocal  cords  will  give  a  summary,  but  satisfactory,  idea 
of  the  mechanism  which  presides  over  this  function,  and  the  part  the  larynx 
plays. 

It  may  also  be  added,  that  nearly  all  the  muscles  of  the  larynx  are  con- 
cerned in  phonation ;  by  modifying  the  tension  and  the  separation  of  the 
vocal  cords  they  determine  differences  in  the  sounds.  One  only  is  concerned 
in  respiration ;  this  is  the  posterior  crico-arytenoideus,  which  is  a  dilator  of 
the  glottis. 

2.  The  Trachea.     (Figs.  230,  234.) 
Preparation. — Follow  the  same  procedure  as  for  the  dissection  of  the  oesophagus. 

The  trachea  is  a  flexible  and  elastic  tube,  formed  of  a  series  of  incom- 
plete cartilaginous  rings,  which  succeed  the  larynx,  and  terminate  above  the 
base  of  the  heart  by  two  divisions,  which  constitute  the  bronchi. 

Form. — This  tube  is  cylindrical,  and  (slightly)  flattened  on  both  sides. 
Its  inferior  face  and  two  borders  are  regularly  rounded,  and  offer  transverse 
grooves,  which  correspond  to  the  intervals  between  the  constituent  pieces  of 
the  trachea.  The  superior  face,  nearly  plane,  shows  the  thin  and  widened 
extremities  of  these  cartilaginous  arcs. 

Course. — Leaving  the  posterior  extremity  of  the  larynx,  the  trachea 
descends  backwards  to  the  entrance  of  the  chest,  by  following  the  inferior 
border  of  the  neck  below  the  longus  colli  muscle.  It  afterwards  becomes 
inflected,  superiorly,  to  pass  between  the  two  first  ribs,  enters  the  chest  in 
traversing  the  anterior  mediastinum,  proceeds  directly  backwards,  and  finally 
arrives  above  the  left  auricle  of  the  heart,  to  the  right  of  the  posterior  aorta, 
where  the  tube  presents  its  terminal  bifurcation. 

Relations. — In  its  cervical  portion,  the  trachea,  surrounded  by  a  loose 
and  abundant  cellular  tissue,  lies  in  a  kind  of  muscular  envelope  which  the 
majority  of  the  muscles  of  this  region  form  around  it,  and  which  are :  the 
sterno-hyoid  and  steruo-thyroid,  placed  in  front ;  the  sterno-maxillaries, 
situated  at  first  ha.  front,  and  afterwards  on  the  sides  towards  their  termina- 
tion ;  the  subscapulo-hyoideii,  above  and  in  the  middle  of  the  lateral  parts ; 
the  scalenii,  altogether  below  and  at  the  sides ;  the  longus  colli,  behind ; 
and  outside  all  these  muscles,  the  superficial  expansion  of  the  subcutaneous 
muscle  of  the  neck.  This  envelope  is  thinnest  in  front  of  the  middle  portion 
of  the  neck ;  and  this  is  the  place  where  the  operation  of  tracheotomy 
should  be  performed. 

The  trachea  is  also  in  relation,  in  its  cervical  portion:  1,  With  the 
oesophagus,  which  descends,  as  we  know,  at  first  in  the  middle  of  the 
posterior  face,  then  to  the  left  side  of  the  air-tube ;  2,  With-  the  carotid 
arteries,  which  pass  along  both  sides  of  the  tube,  accompanied  by  their 
satellite  nerves — the  pneumogastric,  great  sympathetic,  and  recurrent 
nerves. 

After  clearing  the  two  first  ribs,  where  it  reaches  its  thoracic  portion, 
the  trachea  responds,  superiorly,  to  the  longus  colli  and  the  oesophagus ; 
below  to  the  brachial  trunks,  to  the  anterior  aorta  which  fm-nishes  them,  to 
the  anterior  vena  cava,  the  cardiac  and  recurrent  nerves,  and  to  the  base 
of  the  heart ;  laterally,  to  the  inferior  cervical  ganglia  of  the  great  sympa- 
thetic, the  vertebral  vessels — cervical  and  dorso-muscular — and  to  the  two 
^•^vers  of  the  anterior  mediastinum ;  to  the  right,  the  vena  azygos ;  to  the 


458 


THE  BESPIBATORY  APPARATUS  IN  MAMMALIA. 


left,  the  arch  of  the  aorta  and  the  thoracic  duct.     The  latter  is  sometimes 
carried  to  the  opposite  side. 

Stktjctuee, — The  trachea  comprises  in  its  structure :  the  cartilaginous 
rings  which  form  its  base  ;  the  ligaments  which  unite  these  rings ;  the 
mucous  membrane  spread  over  its  inner  face ;  a  muscular  layer,  which  only 
lines  that  membrane  superiorly ;  and  vessels  and  nerves. 

Fiff.  230. 


.     THE   RESPIRATORY   ORGANS;   INFERIOR,   OR   FRONT   VIEW. 

1,  Trachea ;  2,  Jugular  vein  ;  3,  Great  rectus  anticus  muscle  ;  4,  Carotid  artery ; 
5,  Longus  colli  muscle ;  6,  Origin  of  the  common  carotids ;  7,  Vertebral  artery ; 
8,  Section  of  first  rib;  9,  Cephalic  trunk  of  right  axillary  artery;  10,  Anterior 
lobe  of  right  lung;  11,  Middle,  or  supplementary  lobe  of  ditto;  12,  Posterior 
portion  or  lobe  of  ditto  ;  13,  Heart ;  14,  Cardiac  artery  ;  15,  Ventricular  branch 
of  cardiac  vein  ;  16,  Qi^sophagus. 

Cartilaginous  rings  of  the  trachea. — These  are  about  fifty  in  number, 
and  do  not  form  perfect  rings,  being  incomplete  on  the  upper  side  of  the 
trachea.  Each  is  a  kind  of  arc,  composed  of  a  cartilaginous  plate  flattened 
and  curved  on  itself,  whose  extremities  are  turned  towards  each  other,  and 


THE  TEA  CHE  A. 


459 


joined  in  the  majority  of  tlie  rings ;  tliey  even  overlap  in  some.  These 
extremities  are  thin  and  wide,  and  sometimes  bifurcate  and  unite  with  the 
adjoining  rings. 

In  the  middle  part  of  the  trachea,  these  rings  are  generally  larger  than 
at  the  origin  or  termination  of  the  tube.  The  last  ring,  in  serving  as  a 
transition  between  the  trachea  and  bronchi,  presents  a  more  complicated 
arrangement ;  being  frequently  completed  by  isolated  cartilaginous  plates, 
and  is  always  divided  by  a  median  spur  or  bifurcation — directed  towards  the 
interior  of  the  trachea,  into  two  lateral  segments,  each  of  which  corresponds 
to  a  bronchus. 

Ligaments. — The  rings  of  the  trachea  are  united  at  their  borders  by 
intermediate  ligaments,  which  are  composed  of  elastic  tissue,  and -permit  the 
lengthening  or  shortening  of  the  tube  they  concur  to  form. 

Towards  the  extremities  of  the  arcs,  they  are  confounded  with  a  tliin 
cellular  layer  that  unites  these  extremities.  The  first  cartilage  is  received  by 
its  anterior  border  into  the  cricoid  ring,  and  joined  to  it  by  the  wide  annular 
ligament  mentioned  at  page  452.  Owing  to  the  elasticity  of  this  ligament, 
the  two  cartilages  it  binds  together  can  move  one  within  the  other, 
like  two  segments  of  a  telescope,  and  in  this  way  vary  the  length  of  the 
tube. 

Muscular  layer. — This  layer  only  covers  the  superior  face  of  the 
trachea ;  it  is  formed  of  pale,  rose-coloured,  transverse  fasciculi,  attached 
by  their  extremities  to  the  internal  face  of  the  cartilages.  Its  action 
undoubtedly  diminishes  the  diameter  of  the  trachea,  by  contracting  the  arcs 
composing  this  cartilaginous  tube.  (Kolliker  has  found  some  longitudinal 
fibres  passing  across  the  transverse  ones  at  the  posterior  part  of  the  trachea. 
Leyh  describes  longitudinal  fibres  in  the  anterior  wall  of  the  trachea, 
between  the  mucous  membrane  and  the  cartilaginous  rings,  and  which,  he 
states,  diminish  the  length  of  the  tube.) 

Mucous  membrane. — Continuous  with  that  of  the  larynx,  this  membrane 
is  prolonged,  through  the  medium  of  the  bronchi,  and  in  becoming  modified 
in  character,  into  the  air-cells.  Its  free  or  superficial 
surface  is  perforated  by  glandular  orifices,  and  ex- 
hibits longitudinal  ridges  which  are  ineftacable  by 
distension ;  it  is  lined  with  ciliated  epithelium.  Its 
deep  face  is  covered  with  yellow  elastic  tissue  dis- 
posed in  longitudinal  fasciculi,  and  adheres  inti- 
mately either  to  the  face  of  the  cartilages  and  their 
intermediate  ligaments,  or  to  the  posterior  muscular 
layer. 

An  essential  characteristic  which  distinguishes 
this  membrane  from  that  lining  the  larynx,  is  its 
slight  sensibility. 

(The  tracheal  glands,  whose  orifices  are  so  nume-  ^'  External  layer  oflong 
rous  in  the  mucous  membrane,  abound  towards  the 
posterior  part  of  the  tube ;  they  are  small,  ovoid 
bodies,  lying  between  the  muscular  and  fibrous  coats. 
Other  glands,  less  in  size,  are  placed  between  the 
layers  of  fibrous  tissue  uniting  the  cartilages  at  the 
sides  of  the  trachea.  Their  secretion  is  poured  out 
upon  the  free  surface  of  the  mucous  membrane,  to  lubricate  and  protect  it.) 

Vessels  and  nerves.- — The  small  arteries  emanating  from  the  vessels 
in  the  vicinity  of  the  trachea — as  the  carotid  and  the  collateral  branches 


CILIATED    EPITHELIUM 
FROM    THE   TRACHEA. 


tudinal  elastic  fibres ; 
2,  Homogeneous  surface 
layer  of  the  mucous 
membrane ;  3,  Round 
cells ;  4,  Oval  and  ob- 
long cells ;  5,  Ciliated 
cells. 


4u0 


THE  RESPIRATORY  APPARATUS  IN  MAMMALIA. 


of  the  brachial  arteries — supply  it  with  blood.     Its  nerves  come  from  the 
recurrent ;  they  show  small  ganglia  on  their  track. 

Functions. — Except  as  a  tube  for  the  passage  of  the  inspired  and  expired 
air,  the  trachea  performs  no  other  function. 

3.  The  Bronchi.     (Fig.  232.) 

Preparafion. — After  removing  the  lung  from  the  thoracic  cavity,  it  is  filled  with  water 
by  fixing  the  tiaclica  to  a  water-tap.  The  bronchi  may  then  be  dissected  by  tearing 
aiid  triturating  the  i^ulmonaiy  tissue. 

Each  of  the  two  bronchi — the  terminal  branches  of  the  trachea — resembles 
a  tree  imbedded  in  the  substance  of  the  lung,  and  sending  out  a  multitude 
of  branches. 

Fig.  232. 


'^;^v^^''' 


^\  '-^-z 


:^^^^ 


Bronchial  Tube,  with  its  Bronchules  and  Ultimate  Ramifications  (natural  size). 

Disposition.  —  At  a  short  distance  from  their  origin,  the  bronchi  enter 
the  lobes  of  the  lung,  and  pass  backwards  and  outwards  towards  the 
superior  part  of  the  base  of  the  organ,  giving  off  in  their  course  large 
collateral  branches  until  they  tliemselves  are  expended.  These  branches 
originate  alternately  above,  within,  below,  and  outwards  ;  and  thiis  extend 
in  every  direction.  The  first  forms  an  obtuse  angle  with  the  principal 
trunk,  and  is  directed  forwards,  to  ramify  in  the  anterior  lobule  of  the 
lung  ;  the  others  are  detached  at  an  angle  more  or  less  acute.  All  are 
subdivided  into  gradually-decreasing  branches,  which  soon  become  of  a 
capillary  diameter,  and  finally  open  into  the  pulmonary  air-cells.  (See 
Stkuctuke  of  the  Lungs.) 


THE  TRACREA.  461 

Form. — The  bronchial  tubes  are  not  flattened  like  the  trachea;  a 
transverse  section  shows  them  to  be  regularly  cylindrical. 

Volume. — -The  left  bronchus  is  always  smaller  than  the  right,  and  both 
are  much  inferior  in  volume  to  the  aggregate  of  their  respective  branches. 

Relations. — Each  bronchus  enters  the  pulmonary  lobe  along  with  the 
blood-vessels,  which  with  it  forms  what  is  called  the  root  of  the  lung.  The 
divisions  of  this  arborescent  trunk  are  accompanied  by  the  bronchial  artery, 
vein,  and  nerves,  which  ramify  in  the  same  manner. 

Near  their  origin,  the  bronchi  are  related  to  the  bronchial  glands,  above 
which,  and  to  the  left  side,  passes  the  oesophagus. 

Stetjctttre. — The  structure  of  the  bronchial  tubes  resembles  that  of  the 
trachea  ;  their  walls  being  formed  by  a  cartilaginous  framework,  a  muscular 
layer,  mucous  membrane,  and  vessels  and  nerves. 

Cartilages  of  the  bronchi. — These  only  exist  in  tubes  of  a  certain  calibre, 
the  minute  passages  being  deprived  of  them,  aud  having  only  membranous 
walls.  As  in  the  trachea,  this  framework  includes,  for  each  tube,  a  series 
of  transverse  rings  joined  border  to  border  ;  though  these  are  no  longer 
formed  of  a  single  arciform  piece,  but  each  results  from  the  union  of  several 
lozenge-shaped  pieces  whose  extremities  overlap,  and  which  are  united  to 
each  other,  like  the  cartilaginous  segments  of  the  neighbouring  rings,  by 
means  of  cellular  layers,  and  also  by  the  membranes  spread  over  their 
internal  sui'face. 

Muscular  layer. — Extended  in  a  very  thin  continuous  layer  over  the 
entire  inner  surface  of  the  cartilaginous  rings,  this  layer  disappears  in  the 
smallest  bronchial  tubes. 

Mucous  memhrane. — This  membrane  is  dis- 
tinguished from  that  of  the  trachea  by  its  great 
sensibility ;  it  alone  constitutes  the  walls  of 
the  terminal  bronchial  divisions.  (When  the 
cartilages  terminate,  the  tubes  are  wholly  mem- 
branous, and  the  fibrous  coat  and  longitudinal 
elastic  fibres  are  continiied  into  the  ultimate 
ramifications  of  the  bronchiee.  The  muscular 
coat  is  disposed  in  the  form  of  a  continuous 
layer  of  annular  fibres,  and  may  be  traced  upon 
the  smallest  tubes  ;  it  is  composed  of  the  un- 
striped  variety  of  muscular  fibre.) 

Vessels  and  nerves. — The  vascular  and  ner- 
vous branches  distributed  in  the  tissue  of  the    ''^^<'°^'  membrane  of  a  bron- 

,      ■,■-,.-,  r,  ,      ,iT,        1  CHIAL  TUBE,  WITH  THE  CAPIL- 

broucnial  tubes  come  from  the  satellite  vessels       laries  injected. 

and  nerves  of  these  tubes — the  hroncliial  arteries, 

veins,  and  nerves.     The  lymphatics  pass  to  the  bronchial  glands. 

DIFFERENTIAL   CHARACTERS   IN   THE   AIR-Tl'BE   SUCCEEDING   THE   NASAL    CAVITIES   IN   OTHER 

THAN    SOLIPEU   ANIMALS. 

EuMiNANTS.— In  the  Ox,  Slieep,  and  God,  the  interior  of  the  larijnx  is  simpler  than  in 
the  Horse,  and  tlie  lateral  ventricles  and  vocal  cnrds  are  almost  eti'aced.  The  most 
important  diiferences  in  its  various  pieces  are  as  follows :  1,  Tlie  thyroid  cartilage  has 
no  anterior  appendices,  but  is  provided,  posteriorly,  with  two  considerable  prolongations 
that  articulate  with  the  cricoid  cartilage  it  has  no  excavation  between  the  two  wings, 
and  is  formed  by  a  single  piece ;  its  inner  face,  in  the  middle,  near  the  lower  border,  has  a 
small  fossette  to  which  a  round  and  very  salient  tuberosity  on  the  extern^il  face  corres- 
ponds) ;  2,  The  upper  border  of  the  cricoid  is  not  notched  in  front  (neither  is  the  bezel  on 
its  lower  border) ;  3,  The  epiglottis  is  wider,  but  less  acute,  than  iu  Sulipeds  '^Leyh  says  it 


462  THE  BE8PIBAT0BY  APPARATUS  IN  MAM3IALIA. 

is  less  extensive,  but  thicker)  ;  4,  A  hyo-epiglottidean  muscle  bifid  at  its  origin.  (There 
is  no  aryteuo-epiglottidean  ligament.) 

The  trachea  of  these  animals  does  not  olfer  aoy  important  differences.  The  last  ring  is 
not  so  developed  as  in  the  Horse,  and  the  tube  detaches  a  supplementary  bronchus  to  a 
lobe  of  the  lung  which  does  not  exist  in  Solipeds.  (Tlie  rings  of  the  middle  portion  are 
proportionally  nariow,  and  their  exti-emities  meet  behind  and  form  a  salient  ridge.) 

Pig. — The  larynx  of  the  Pig  is  remarkable  for  its  great  mobility,  suspended  as  it  is  to 
the  hyoid  cornua  by  the  base  of  a  very  developed  epiglottis,  rather  than  by  the  wings  of 
the  thyroid  cartilage.  "  There  are  wide,  shallow,  lateral  ventricles,  which  have  a  small 
oblong  sinus  that  ascends  between  the  thyroid  cartilage  and  the  mucous  membrane. 
These  ventricles  are  not  surrounded  by  the  thyro-arytenoideus  muscle,  which  is  small 
and  undivided ;  above  and  outwardly,  they  are  margined  by  a  thick  cord — a  kind  of 
superior  vocal  cord,  considered  by  Duges  as  acting  with  the  ventricles  to  modify  the 
deep  grunting  sounds."  *  (Instead  of  a  tuberosity  on  the  external  face  of  the  thyroid 
cartilage,  there  is  a  median  crest,  and  its  inferior  border  has  a  small  point.  The  cricoid 
appears  to  be  drawn  downwards  and  backwards,  and  its  lower  border  is  very  prominent  in 
the  middle,  and  articulates  with  one  or  two  small  cartilaginous  plates  which  have  been 
sometimes  wrongly  described  as  belonging  to  the  proper  cartilages  of  the  larynx.  The 
antero-superior  angles  of  the  arytenoid  cartilages  are  united  to  a  small  cartilaginous 
piece  which  prolongs  them ;  their  external  face  has  a  spine,  and  the  internal  angles  are 
separated  by  a  small  pisiform  body  called  the  '  interarticuiar  cartilage.") 

The  trachea  of  this  animal  resembles  that  of  Ruminants.  (It  has  about  thirty  rings, 
and  has  three  bronchi.") 

Carnivora.— The  larynx  of  the  Dog  and  Cat  is  very  like  that  of  the  Horse.  In 
proportion,  the  epiglottis  is  shorter,  wider  at  the  base,  and  more  triangular  than  in  the 
other  species ;  the  lateral  ventricles  are  shallow.  (There  is  an  interarticuiar  cartilage  as 
in  the  Pig ;  there  is  no  sub-epiglottidean  ventricle,  and  the  vocal  cords  appear  to  be 
nearer  each  other.  The  trachea  has  about  forty-two  rings,  whose  extremities  do  not  meet ; 
the  space  between  them  is  less  in  the  Cat  than  the  Dog.) 

The  larynx  and  trachea  of  Man  will  be  compared  with  that  of  animals  when  we  come 
to  describe  the  lungs. 

THE  THOEAX.     (Figs.  230,  234.) 

The  thorax,  also  called  the  thoracic  or  pectoral  cavity,  lodges  not  only 
the  lungs,  but  also  the  heart  and  the  large  ve.ssels  that  spring  from  or 
pass  to  that  organ,  with  a  portion  of  the  oesophagus  and  trachea,  as  well 
as  nerves,  which  are  as  remarkable  for  their  number  as  their  physiological 
importance. 

Situation. — We  have  seen  that  the  thorax  has  for  its  base  the  bony  cage 
formed  by  the  ribs,  sternum,  and  bodies  of  the  dorsal  vertebraB.  Suspended 
beneath  the  middle  portion  of  the  spine,  this  cage  is  transformed  into  a 
closed  cavity  by  the  intercostal  muscles,  which  fill  the  spaces  between  the 
ribs  ;  and  by  the  diaphragm,  that  vast  oblique  partition  which  separates  the 
thorax  from  the  abdomen. 

Internal  conformation. — Considered  as  a  whole,  the  thoracic  cavity 
represents  a  hollow  cone  placed  horizontally,  depressed  on  each  side,  and 
particularly  in  front  towards  the  summit;  with  its  base,  formed  by  the 
diaphragm,  cut  very  obliquely,  in  consequence  of  the  direction  taken  by  that 
muscle.  This  obliquity  of  the  diaphragm  renders  the  antero-posterior 
diameter  of  the  cavity  much  greater  above  than  below ;  the  difference  is 
more  than  double. 

The  internal  surface  of  this  conical  cavity  may  be  divided  into  six 
regions  :  a  superior,  inferior,  and  two  lateral  planes,  a  base,  a  posterior  plane, 
and  a  summit. 

The  superior  plane  presents,  on   the   middle   line,  a  large  projection 

resulting  from  the  union  of  the  vertebral  bodies  ;  and,  laterally,  two  deep 

channels — furrows — the  vertehro-costal  channels.     These  latter,  wider  behind 

than  before,  are  formed  by  the  superior  extremities  of  the  costal  arches ; 

^  Lavocat,  '  Auatomie  des  Animaux  Domestiques.' 


THE  THORAX. 


463 


tliey  lodge  the  superior  border  of  the  pulmonary  lobes.  The  middle 
projectiou,  or  ridge,  is  comprised  between  these  two  lobes.  Covered  in  front 
by  the  posterior  extremity  of  the  longus  colli,  this  ridge  responds,  for  the 
remainder  of  its  extent,  to  the  posterior  aorta,  the  thoracic  canal,  and  the 
vena  azygos;  on  its  sides  are  seen  the  subdorsal  branches  of  the  great' 
sympathetic  nerve. 

The  inferior  plane,  much  shorter  than  the  preceding,  is,  like  it,  narrower 
in  front  than  behind ;  it  has  for  a  base  the  superior  face  of  the  sternum, 
the  sternal  cartilages,  and  the  triangularis  sterni  muscle.  Posteriorly, 
it  gives  attachment  to  the  fibrous  sac  containing  the  heart. 


Fio;.  234. 


THE  PECTORAL  CAVITY  AND   MEDIASTINUM,  WITH  THE  COURSE  OF  THE  TRACHEA 
AND   (ESOPHAGUS. 

A,  Anterior  mediastinum;  B,  Posterior  mediastinum;  C,  The  heart  and  pericar- 
dium in  the  middle  part  of  the  mediastinum ;  D,  Diaphi-agm ;  E,  Trachea ;  f, 
(Esophagus. 

The  lateral  planes,  more  extensive  than  the  other  two,  are  concave  in 
both  their  diameters.  Formed  by  the  internal  face  of  the  ribs  and  the 
deep  intercostal  muscles,  they  are  in  contact  with  the  external  face  of  the 
lung. 

The  base,  or  posterior  plane,  formed  by  the  convex  face  of  the  diaphragm, 
is  circumscribed  on  its  exterior  contour  by  the  circle  of  asternal  cartilages, 
and  by  the  last  rib.  In  it  we  see  the  three  openings  which  traverse  the 
diaphragmatic  septum. 

The  summit,  or  entrance  of  tlie  tJiorax,  is  an  oval  opening,  elongated 
vertically,  comprised  between  the  two  first  ribs  and  the  longus  colli  muscle, 
and  which  is  partly  obstructed  by  an  enormous  collection  of  lymphatic 
glands ;  through  this  opening  passes  the  trachea,  oesophagus,  the  axillary 
and  carotid  arteries,  the  anterior  vena  cava,  and  the  pneumogastric,  great 
sympathetic,  inferior  laryngeal,  and  diaphragmatic  nerves. 


464  THE  RESPIRATORY  APFARATUS  IN  MAMMALIA. 

Sucli  is  the  thoracic  cavity.  Like  the  abdomen,  it  is  provided  witli.  a 
serous  lining,  which  remains  to  be  examined. 

The  Pleura. — The  serous  lining  of  the  thprax  comprises  two  distinct 
membranes,  designated  as  the  pleime,  constituting  two  sacs  placed  one 
against  the  other  in  the  median  plane,  and  forming  a  septum  named  the 
mediastinum,  which  divides  the  thoracic  cavity  into  two  lateral  compart- 
ments. Each  pleura,  therefore,  covers  one  of  the  external  or  costal  walls 
of  the  thorax,  and  the  corresponding  moiety  of  the  diaphragm ;  it  is 
afterwards  reflected  in  the  vertical  and  antero-posterior  plane  of  the  cavity, 
to  concur  in  the  formation  of  the  mediastinum,  whence  it  is  carried 
over  the  lung.  This  arrangement  exhibits  the  pleura  in  four  portions  : 
a  costal,  diaphragmatic,  mediastinal,  together  representing  the  parietal  layer 
of  the  membrane,  and  a  pulmonary  or  visceral  portion. 

The  costal  pleura  is  ajiplied  to  the  inner  face  of  the  ribs  and  the  internal 
intercostal  muscles.  Strengthened  on  its  adherent  face,  at  each  intercostal 
space,  by  a  lamina  of  yellow  elastic  tissue,  this  membrane  responds,  by 
its  free  face,  to  the  external  plane  of  the  lung,  with  which  it  does  .not,  in 
a  normal  condition,  contract  any  adhesions.  It  is  continued,  jDosteriorly, 
with  the  diaphragmatic  layer ;  in  front,  above,  and  below,  with  the  medias- 
tinal pleura. 

The  diaphragmatic  pleura  adheres  somewhat  loosely  to  the  fleshy  portion 
of  the  muscle,  but  the  union  is  more  intimate  on  the  aponeurotic  portion. 
This  layer  is  contiguous,  by  its  free  face,  with  the  base  of  the  lung ;  it  is 
confounded  with  the  mediastinum  by  the  internal  part  of  its  periphery. 

The  mediastinal  pleura  is  placed,  by  its  adherent  face,  against  that  of  the 
opposite  side,  and  in  this  way  produces  the  middle  septum  which  divides 
the  thoracic  cavity  into  two  portions.  Several  organs  are  comprised  between 
the  two  layers  of  this  partition,  but  most  important  of  all  is  the  heart.  In 
Veterinary  Anatomy,  that  part  of  the  septum  in  front  of  this  organ  is  named 
the  anterior  mediastinum  ;  the  appellation  of  posterior  mediastinum  being 
reserved  for  the  portion  situated  behind  it.  These  terms  have  not  the  same 
signification  as  in  hmnan  anatomy,  though  they  are  retained  here  to  prevent 
misunderstanding. 

The  anterior  mediastinum,  thicker  than  the  posterior,  but  much  less 
extensive,  contains,  superiorly,  the  trachea,  oesophagus,  the  anterior  aorta  and 
its  divisions,  the  anterior  vena  cava,  thoracic  duct,  the  cardiac,  pneumo- 
gastric,  recurrent,  and  diaphragmatic  nerves ;  it  also  includes  the  thymus 
gland  in  the  foetus  and  young  animal.  The  posterior  mediastinum  is 
incomparably  narrower  below  than  above,  in  consequence  of  the  oblique 
position  of  the  diaphragm.  Its  inferior  part,  always  deviated  to  the  left,  is 
extremely  thin,  and  perforated  by  small  openings,  which  give  it  the 
appearance  of  fine  lace-work.  Traversed  altogether  superiorly  by  the  pos- 
terior aorta,  the  vena  azygos,  and  the  tlioracic  duct,  this  mediastinum  gives 
passage,  a  little  lower  between  its  layers,  to  the  oesophagus,  the  oesophageal 
branches  of  the  pneumogastric  nerves,  and  to  the  left  dia])hragmatic  nerve. 
It  is  these  layers  of  this  mediastinum  which  pass  to  the  lung  to  constitute 
the  pulmonary  pleura,  in  becoming  reflected  above  and  below,  in  a  hori- 
zontal line  extending  from  the  root  of  the  pulmonary  lobe  to  the  anterior 
face  of  the  diaphragm. 

The  pulmonary  or  visceral  pleura,  a  continuation,  as  has  been  said,  of  the 
mediastinal  pleura,  is  in  contact,  by  its  free  face,  with  the  parietal  layer  of 
the  membrane.  Its  deep  face  adheres  intimately,  in  Solipeds,  to  the  proper 
tissue  of  the  lungs. 


THE  THORAX. 


465 


Independently  of  these  four  serous  layers,  tlie  right  pleura  furnishes  a 
special  membranous  fold,  which  arises  from  the  inferior  wall  of  the  thoracic 
cavity,  and  ascends  to  envelop  the  posterior  vena  cava.  This  fold  also 
sustains  the  right  diaphragmatic  nerve. 

In  order  to  study  the  various  portions  of  the  pleurae  collectively,  with 
their  reciprocal  relations,  and  their  connections  with  the  organs  contained 
in  the  thoracic  cavity,  we  will  suppose  three  transverse  sections  of  this 
cavity  :  one  passing  behind  the  heart ;  the  other  at  the  roots  of  the  lungs, 
and  dividing  the  left  ventricle  of  the  heart ,  the  third  traversing  the  anterior 
mediastinum,  a  little  in  front  of  the  right  ventricle. 

If.  in  the  first  section  (Fig.  235),  we  take  the  costal  pleura  at  the  point 
a,  and  follow  it  up  to  6,  we  will  see  it  folded  downwards    to   form   the 


Ficr.  235, 


Fig.  236. 


Ficr.  237 


THEOKETICAL   S1::CTI0:<S    OF    THE    THORACIC    CAVITY  J    II^TENDED    TO    SHOW    THE 
DISPOSITION   OF   THE    PLEURAE. 


mediastinal  layer,  to  be  applied  to  the  aorta,  c,  and  the  oesophagus,  d  ;  then 
reflected  at  e  on  the  lung,/,  enveloping  every  part  of  the  organ  ;  returning  to 
the  point  e,  it  leaves  the  lung,  is  again  reflected  to  achieve  the  formation 
of  the  mediastinal  septum,  h  g,  and  finally  regains  the  jwint  it  started  from. 
On  the  right  side,  with  only  a  slight  variation,  it  has  the  same  arrangement. 
After  being  carried  from  the  point  a'  to  b',  then  to  e',  and  after  enveloping 
the  lung,  returning  to  e,  and  being  reflected  in  the  median  jilane  to  the 
point  g',  the  right  pleura  leaves  the  inferior  thoracic  wall  to  pass  aroimd 
the  posterior  vena  cava,  and  come  back  to  a',  its  point  of  departure. 

The  second  section,  (represented  by  Fig.  236)  shows  the  pleura  arrived 
at  the  point  h,  descending  on  the  root  of  the  lung,  c,  covering  that  organ 
and  returning  to  c,  and  reflected  on  the  pericardium,  d,  to  gain  the  point  a. 

In  the  third  section  (Fig.  237),  we  see  the  parietal  pleura,  a  h,  without 
any  points  of  continuity  with  the  visceral  pleura,  c.  It  is  at  the  level  of 
this  section  that  the  lung  forms  two  perfectly  free  lobes,  which  are  not 
attached  to  the  anterior  mediastinum. 

Stktjcture. — Like  all  the  serous  membranes,  the  pleurae  have  a  free  face 
covered  by  a  simple  tesselated  epithelium ;  it  is  perfectly  smooth,  always  in 
contact  with  itself,  and  constantly  lubricated  by  a  serous  fluid  which 
facilitates  the  gliding  of  the  lung  on  the  parietes  of  tlie  thoracic  cavity. 


40(5  TBE  BESPIBATOBY  APPARATUS  IN  MAMMALIA. 

The  deep  face  is  united  to  the  subjacent  parts  by  connective  tissue 
destitute  of  fat ;  the  adherence  of  the  visceral  pleurje  is  most  intimate. 

The  pleura  has  plexuses  of  vessels  :  one,  the  subserous,  has  large  meshes  ; 
but  a  second,  the  subepithelial,  has  a  closer  network. 

The  nerves  are  from  the  sympathetic  and  pneumogastric  for  the  pul- 
monary pleiu-a :  from  the  diaphragmatic  and  intercostal  nerves  for  the 
parietal  pleura. 

Functions. — The  thorax  is  not  a  mere  receptacle,  but,  on  the  contrary, 
performs  a  very  important  part  in  the  act  of  respiration.  We  know,  in  fiict 
that  it  is  dilated  and  contracted  by  the  movements  of  the  diaphragm  and  the 
ribs  (see  pp.  142,  248).  The  lung  being  applied  immediately  against  the 
thoracic  walls,  and  never  at  any  time  separate  from  them,  follows  this  cavity 
in  its  movements,  dilating  in  inspiration  and  contracting  in  expiration,  after 
a  certain  quantity  of  the  oxygen  of  the  inspired  air  has  been  removed  and 
replaced  by  an  equivalent  amount  of  carbonic  acid. 

The  movements  of  the  thorax  are,  therefore,  of  capital  importance,  con- 
stituting, as  they  do,  the  initial  phenomenon  of  respii*ation,  and  having 
dependent  on  them  all  the  other  acts  of  this  function. 

DIFFERENTIAL   CHARACTERS   IN   THE   THORAX  OF  OTHER   THAN   SOUPED   ANIMALS. 

In  the  Ox,  the  tliorax  is  not  so  long,  particularly  in  its  superior  part,  as  in  Solipeds, 
by  reason  of  the  slight  obliquity  of  the  diaphragm,  and  of  its  mode  of  attachment  to  the 
ribs. 

The  total  capacity  of  this  cavity  is  also  certainly  inferior  to  that  of  the  Horse's  chest. 
It  is  the  same,  though  relntively  more  extensive,  in  the  Sheep,  Goat,  and  Fig ;  while 
the  Doj  possesses  in  this  respect  an  incontestable  superiority  over  Solipeds.  It  is  to  be 
noted  that  all  tiiese  animals,  without  exception,  are  distinguished  from  the  Horse.  Ass, 
and  Mule  by  the  conformation  of  the  posterior  mediastinum.  In  them  it  is  not  open  in 
its  lower  part,  but  as  solid,  thick,  and  complete  there  as  elsewhere.  Therefore  it  is  that 
the  consecutive  effusion  of  pleuritis  is  readily  localised  in  one  of  the  pleural  sacs  in  the 
first-named  animals,  while  this  localisatiim  is  impos-sible  in  the  second.  (This  is  an 
important  observation,  in  a  pathological  point  of  view.) 

THE  LTJNa  (or  lttngs).     (Figs.  230,  234.) 

Preparation. — The  flisposition  of  the  lung  in  the  thoracic  cavity  is  best  studied  by 
plrtcing  the  subject  in  the  second  position,  opening  the  chest  by  excision  of  the  ribs,  as 
in  Fig.  234,  and  inflating  the  organ  by  the  trachea.  To  study  i'ts  external  conformation, 
it  should  be  removed  from  the  cavity,  with  the  heart  and  large  vessels,  and  inflatetl  as 
before. 

Situation — General  disposition. — This  essential  organ  of  respiration  is  a 
spongy  viscus,  lodged  in  the  thoracic  cavity,  and  divided  into  two  lateral, 
but  independent,  moieties,  each  of  which  occupies  one  of  the  two  serous  sacs 
formed  by  the  plurfe.  It  is  also  .described  as  two  pulmonary  lohes,  or  tivo 
lungs— a  right  and  left,  the  latter  a  little  less  voluminous  than  the  former. 

Form  and  Belatlons.—Together,  the  lungs  affect  the  outline  of  the 
thoracic  cavity;  each  represents  the  moiety  of  a  cone,  and  offers  for  study : 
an  external  and  internal  face,  a  base  and  summit,  and  a  superior,  inferior,  and 
posterior  border. 

The  external  or  costal  face  is  convex  (and  smooth),  and  moulded  to  the 
external  v\all  of  the  thorax. 

The  internal,  or  mediastinal  face,  forms  a  vertical  plane,  separated  from 
the  opposite  lung  by  the  mediastinum.  It  shows  :  1,  An  inextensive  anterior 
part,  in  contact  with  the  anterior  mediastinum ;  2,  At  the  level  of  the  heart, 
an  excavation  in  which  that  organ  is  lodged  ;  3,  Immediately  behind  this 
excavation,  and  a  little  above  it,  the  root  of  the  lung  (Jiilum-pulmonis) ,  afasci- 


THE  LUNGS.  467 

cuius  formed  by  the  air-tubes  and  pulmnary  vessels  in  entering  the  viscus  ; 
4,  A  posterior  portion,  more  extensive  than  the  other  two  jnit  together, 
corresponding  to  the  posterior  mediastinum,  and  attached  to  that  septum  by 
means  of  a  fold  developed  around  the  organ,  to  form  the  pulmonary  pleura  ; 
this  fold  constitutes,  posteriorly,  a  small  serous  ligament  [lig amentum  latum 
'pulmonis),  attached  at  once  to  the  mediastinum  and  the  posterior  face  of  the 
diaphracjm.  On  this  portion  of  the  lung  are  remarked  two  antero-posterior 
fissures :  one,  hollowed  near  the  upper  border  of  the  organ,  to  receive  the 
thoracic  aorta ;  the  other  situated  lower,  but  not  so  deep,  more  marked  in 
the  left  than  the  right,  and  lodging  the  oesophagus.  In  the  right  lung  this 
mediastinal  face  offers  a  small  particular  lobule,  which  is  absent  in  the  left. 

The  hase,  or  diaphragmatic  face  of  the  lung,  cut  obliquely  from  above  to 
below,  and  before  to  behind,  is  concave,  and  moulded  to  the  anterior  face  of 
the  diaphragm.  On  the  right  lung  is  seen  the  posterior  face  of  the  small 
lobule  noticed  on  the  inner  side,  and  a  deep  fissure  excavated  between  it  and 
the  principal  lobe,  for  the  jjassage  of  the  posterior  vena  cava. 

The  summit  of  the  viscus,  situated  behind  the  first  rib,  presents  a  kind  of 
detached  appendix,  designated  the  anterior  lobule  of  the  lung. 

The  superior  border,  thick,  convex,  and  rounded,  is  lodged  in  the  vertebro- 
costal channel  or  concavity.  The  inferior,  much  shorter  and  thinner,  is 
deeply  notched  at  the  level  of  the  heart,  and  more  so  at  the  left  than  the 
right  side.  The  posterior  is  elliptical,  and  everywhere  circumscribed  by  the 
face  of  the  diaphragm,  which  it  separates  from  the  costal  and  mediastinal 
faces. 

Structure. — An  external  serous  envelope,  proper  fundamental  tissue, 
functional  and  nutrient  vessels,  lymphatics,  and  nerves :  such  are  the  elements 
which  enter  into  the  organisation  of  the  lung. 

Serous  Envelope. — This  is  the  pleura  pulmonalis  already  described. 
(There  has  also  been  described  a  subserous  connective  tissue,  containing  a 
large  proportion  of  elastic  fibres ;  it  invests  the  entire  surface  of  the  lung, 
and  extends  between  the  lobules.) 

FuNDAMENTAii  TissuE. — Physical  characters. — The  pulmonary  tissue  in 
the  adult  is  of  a  bright  rose-colom' ;  it  has  a  deeper  hue  in  the  foetus  which 
has  not  respired.  Although  soft,  it  is  yet  very  strong  and  resisting,  and 
can  with  difficulty  be  torn.  Its  elasticity  is  remarkable  ;  it  concurs  in  the 
collapse  the  lung  experiences  when  air  is  admitted  to  the  pleural  sacs.  It  is 
very  light :  plunged  in  water,  if  healthy,  it  floats :  this  specific  lightness 
ought  to  be  attributed  to  the  air  imprisoned  in  the  pulmonary  vesicles. 
This  may  be  proved  by  what  takes  place  when  the  lung  of  a  foetus  is 
inflated :  heavier  than  water  before  that  operation,  it  then  becomes  lighter, 
because,  notwithstanding  all  the  manipulation  that  may  be  employed  to  expel 
the  air  introduced  into  the  pulmonary  vesicles,  a  certain  quantity  always  re- 
mains. On  the  other  hand,  the  absolute  weight  of  the  lung  is  relatively  more 
considerable  in  the  adult  than  in  the  foetus,  the  first  representing  l-30th  of 
the  total  mass  of  the  body,  while  it  is    only  l-60th  in  the  second. 

A  knowledge  of  these  facts  may  be  utilised  in  determining  whether  a  given 
lung  has  belonged  to  an  animal  which  has  respired  or  has  died  before  birth. 
If  the  tissue  is  plunged  in  water,  this  test  is  called  hydrostatic  pulmonary 
docimacy ;  if  its  relative  weight  is  to  be  ascertained,  it  is  designated 
pulmonary  docimacy  by  weight. 

These  are  the  physical  characters  of  the  fundamental  tissue  of  the  lung ; 
we  will  now  study  its  anatomical  characters. 

Anatomical  characters. — The  pulmonary  tissue  is  partitioned  into  a  great 


468  THE  RESPIRATORY  APPARATUS  IN  MAMMALIA. 

number  of  small  polyhedral  lobules  by  sejDta  of  connective  tissue,  which 
appear  to  be  prolongations  of  the  corium  of  the  external  serous  membrane. 
This  segmentation  into  lobules  is  a  common  feature  in  the  organisation  of 
the  lungs  in  the  mammalia,  but  it  is  more  readily  demonstrated  in  some  than 
others :  not  very  evident  in  Solipeds,  and  less  so  in  the  Carnivora,  it  is  well 
defined  in  Kuminants  and  Pachyderms. 

The  organisation  of  these  lobules  resembles,  in  a  striking  manner,  that 
of  the  salivary  lobules.  Each  receives  a  small  bronchial  tube  (lobular 
bronchial  tube),  which  is  prolonged  into  the  lobule  by  several  short  terminal 
branches,  in  which  open  a  certain  number  of  elementary  vesicles.  In 
comparing,  for  the  moment,  the  lung  to  a  gland,  it  will  be  seen  that  this 
organ  should  be  ranged  in  the  category  of  racemose  glands. 

To  demonstrate  the  vesicular  structure  of  the  lung,  it  may  be  inflated 
and  dried,  and  sections  afterwards  made  to  show  the  pulmonary  vesicles. 
But  this  procedure  has  the  inconvenience  of  unduly  extending  the  vesicles, 
and  thinning,  and  even  destroying,  their  walls.  A  better  method  is  the 
following :  leave  the  lung  in  the  intact  thoracic  cavity  ;  by  the  jugular  vein, 
pour  into  the  right  side  of  the  heart  an  injection  of  very  hot  tallow, 
employing  a  certain  amount  of  force  to  propel  it  from  the  pulmonary  artery 
into  the  veins;  when  this  injection  has  cooled,  open  the  thoracic  cavity,  and 
take  out  the  lungs.  These,  being  impregnated  with  solidilied  fat,  do  not 
collapse  on  contact  with  the  air,  and  sections  made  in  different  directions 
then  exhibit  innumerable  perfectly-circular  porosities,  which  are  the  open 
pulmonary  vesicles. 

In  this  way  it  is  easy  to  demonstrate  the  presence  of  the  air-cells  ;  but, 
in  order  to  conveniently  study  their  arrangement,  it  is  necessary  to  take  a 
cast  of  them  by  means  of  a  solidifiable  material  introduced  by  the  bronchii, 
and  afterwards  destroyed  by  the  maceration  of  the  pulmonary  tissue.  The 
Darcet  alloy,  employed  in  this  manner,  often  gives  very  good  results.  It  is 
then  found  that  the  pulmonary  vesicles  form,  in  each  lobule,  saccular 
dilatations  or  culs-de-sac,  from  l-70th  to  l-200th  of  an  inch  in  diameter, 
grouped  around  the  infundihuli,  of  which  they  are  only 
Fig.  238.  diverticuli ;     these    infundibuli   commimicate   with    the 

terminal  bronchule  of  the  lobule  through  the  medium  of 
a  narrow  central  cavity,  into  which  they  all  open.  Such 
are  the  principal  histologic  details  relative  to  this  im- 
portant point  in  the  history  of  the  lungs ;  and  it  must 
necessarily  be  followed  by  a  notice  of  the  structure  of 
the  pulmonary  vesicles  (or  air-cells). 

The  pulmonary  vesicles  comprise,  in  the  organisation 
of  their   walls :  a    proper  membrane ;   epithelium  ;  and 
capillary  vessels. 
I  PLAN  OF  A  PUL-  !•  '^h.B  propcv  membrane  is  thin  and  homogeneous;  it 

MONARY  LOBULE.       coutaius  the  nuclei  of  connective  tissue  and  elastic  fibres, 
a,    Bronchule    termi-    and  its  external  face  is  applied  to  tliat  of  the  neighbour- 
nating   in  a  slight    ing  vesicles  ;   its  internal  face  is  lined  by  epitheliiun. 
dilatation  6;  c  Ail-  3.  The  epithelium  is  simply  tesselated,  and  is  com- 

sacs,  or  mtundibuli ;  i      /•       .  i     ,1  •  n  t,   •  ,•  J^  -i 

d.  Air  or  pulmonary    posecl  oi  extremely  thin  cells.     It  is  continuous  tbrougn- 

vesicles.  out  the  vesicles,  and  with  that  of  the  terminal  bronchule. 

In   a    properly-prepared  section,    the   polyhedral   cells 

lining    the    latter   can    be    seen    changing    gradually   and    rapidly    into 

squamous   epithelium  in    the  cavity  of  the  lobule,  at   the  entrance  to  the 

infundihuli. 


TEE  LUXGS 


469 


(The   minute   polygonal  cells   lining   the   air   or   pulmonary   vesicles 


an   inch   in   diameter,  and  from 


Fig.  239. 


,a 


measure  from  1-1 600th  to  l-2250th  of 
l-2800th  to  l-3800th  of  an 
inch  in  thickness.  Between  the 
vesicles  is  a  trabecular  tissue, 
mainly  composed  of  yellow  elas- 
tic with  a  few  muscular  fibres, 
some  of  which  are  united  with 
the  lining  membrane  to  strength- 
en it,  esjiecially  around  the 
apertures  of  communication  be- 
tween the  adjoining  air-cells.) 

3.  Capillary  vessels  ramify 
in  the  walls  of  the  vesicles,  and 
even  project  on  their  inner 
face. 


(The  capillary  plexuses  are 
so  arranged  between  the  two 
layers  forming  the  walls  of  two 
adjacent  cells,  as  to  exjiose  one 
of  their  surfaces  to  each,  in  order 
to  secure  the  influence  of  the 
air  upon  them.  These  networks 
are  so  close,  that  the  diameter 
of  the  meshes  is  scarcely  so 
great  as  that  of  the  capillaries 
which  inclose  them.) 

VESt>ELs. — The  lung  is  a 
very  vascular  organ.  The  nu- 
merous ramitications  it  receives 
divide  into  two  orders — the  functional  and  the  nutritive  vessels. 

Functional  vessels  of  the  lung. — We  know  that  the  blood  returns  from  all 
parts  of  the  body  by  the  veins,  after 
losing,    along  with   its    bright   red  '^' 

colour,  the  properties  which  render 
it  fit  to  maintain  the  vitality  of  the 
tissues.  It  thus  arrives  at  the  right 
side  of  the  heart,  whence  it  is  pro- 
pelled into  the  lung,  there  to  be 
regenerated  by  mediate  contact  with 
the  air.  It  is  the  pulmonary  artery 
which  conveys  this  fluid  into  the 
parenchyma  of  the  organ,  and  by 
the  pulmonary  veins  it  is  carried 
back  to  the  heart.  The  artery  is 
at  first  divided  into  two  branches, 
which  ramify  and  finally  terminate 
in  dense  capillary  plexuses  upon  the 
walls  of  the  air-cells.  The  veins, 
innumerable  and  attenuated  at  their 
origin,  like  the  arterial  capillaries,  terminate  in  from  four  to  eight  principal 
trunks,  which  open  into  the  left  auricle  of  the  heart. 

These  two  orders  of  vessels,  which  necessarily  participate  in  the  phvsiolo- 
83 


AIR-CELLS   OF   LUNG,   WCTH   rSTTERVENING  TISSUES. 

«,  Epithelium ;  h,  Elastic  trabecule ;  c,  Membranous 
wall,  with  fine  elastic  fibres. 


ARRAXGEIIEXT   OF     THE    CAPILLARIES    AROUND 
THE    AIR-CELLS. 


470  THE  EESPIRATORY  APPARATUS  IN  MAMMALIA. 

gical  functions  of  the  lung,  like  the  vena  portge  with  the  liver,  are  very 
properly  distinguished  from  the  other  arteries  or  veins  of  the  organ  by  the 
designation  of  functional  vessels.  But  though  they  are  so  named,  it  must 
not  be  inferred  that  they  are  excluded  from  all  participation  in  the  acts  of 
nutrition,  It  is  now  admitted  by  competent  authorities  that  the  blood 
of  these  vessels  concurs  to  sustain  vitality  in  the  tissue  of  the  lung,  in 
common  with  the  nutritive  fluid  carried  by  the  arteries  and  veins  now  to  be 
described. 

Nutrient  vessels. — By  this  name  is  designated  the  divisions  of  the 
hronchial  arteries  and  veins,  whose  terminal  ramifications  anastomose  with 
the  capillaries  of  the  pulmonary  vessels  at  the  ultimate  bronchules. 

Lymphatics. — These  vessels  are  divided  into  superficial  and  deep.  The 
first  form  a  network  beneath  the  pleui'a ,  the  second  exist  in  large  numbers 
around  the  lobules.  They  mix  together,  and  terminate  in  the  bronchial 
glands.  (Lymphatics  of  very  small  size  have  been  described  as  commencing 
in  the  alveolar  spaces,  on  leaving  which  they  gain  a  proper  coat  or  internal 
tunic,  and  are  subsequently  supplied  with  valves.) 

Nerves. — The  nervous  branches  supplied  to  tlie  tissue  of  the  lung  come 
from  the  same  source  as  those  of  the  bronchial  tubes — the  pneumogastric  and 
great  sympathetic  nerves.  Their  ramifications  accompany  the  pulmonary 
vessels  and  bronchiae,  and  they  show  small  ganglia  on  their  course. 

Functions. — To  know  that  the  lung  is  the  seat  of  the  absorption  of 
oxygen  and  the  expulsion  of  carbonic  acid  from  the  nutritive  fluid — 
phenomena  accompanied  by  the  transformation  of  the  dark  into  red-coloured 
blood,  and  probably  of  several  other  metamorphoses  yet  doubtful  or  un- 
known —is  the  only  authentic  fact  necessary  to  remember  with  regard  to  the 
functions  of  this  organ.  It  must  be  added  that  the  subtle  molecular  opera- 
tions from  which  all  these  phenomena  result,  take  place  in  the  lung  by  the 
mediate  contact  of  the  atmosphere  introduced  into  the  air-cells  during 
inspiration,  with  the  blood  traversing  the  walls  of  these  cells.  With  the 
intimate  mechanism  of  these  molecular  actions  we  have  nothing  to  do  here, 
however 

Development. — Although  the  lung  is  in  a  state  of  inactivity  in  the 
foetus,  yet  it  is  one  of  the  organs  early  developed.  During  the  whole  period 
of  foetal  existence,  its  lobular  texture  is  much  better  defined  than  in  the 
adult,  and  it  then  appears  to  be  formed  exactly  like  a  racemose  gland. 
Sections  of  it  prepared  for  microscopical  examination  distinctly  show  the 
vesicles  and  their  arrangement.  We  have  already  made  known  the  differ- 
ences in  colour  and  density  which  distinguish  the  pulmonary  tissue  of  the 
foetus  and  that  of  the  adult.  It  only  remains  to  repeat  what  has  been  said 
as  to  the  slight  vascularity  of  the  first,  and  to  note  that  the  blood  of  the 
pulmonary  artery  passes  almost  entirely  into  the  posterior  aorta  by  the 
arterial  canal  (or  ductus  arteriosus). 

DIFFERENTIAL   CHARACTEBS   IN   THE   LUNGS  OF   OTHER   THAN   SOLIPEB   ANIMALS. 

The  lungs  of  the  Ox,  Sheep,  and  Goat  are  remarkable  for  the  distinctness  with  which 
the  lobules  are  defined.  They  are,  in  fact,  separated  by  thick  layers  of  cellular  tissue, 
continuous  with  the  internal  face  of  the  visceral  pleura.  These  thick  septa  are  ratlier 
the  interlobular  ramifications  sent  off  from  the  subserous  envelope.)  Dietrichs,  who  was 
the  first  to  draw  attention  to  this  peculiarity  in  the  larger  Runnnauts.  has  justly  remarked 
that  it  perfectly  explains  the  altogether  special  characters  of  the  lesions  of  pneumonia  in 
these  animals. 

The  general  figure  of  the  lungs  of  Ruminants  does  not  differ  from  that  observed  in 
the  Horse ;  the  left  lung,  however,  is  divided  into  two  lobes,  and  the  right  into  four, 


THE  LUNGS. 


ill 


of  which  one,  an  anterior,  is  curved  in  front  of  the  heart 
this  peculiarity. 

In  the  Pig,  the  lungs  comport  themselves  like  those  of  Kuminants. 

In  the  Dog  and  Cat,  there  is  no  well- 
marked  fissure  in  either  lung   towards   the  Fig.  241 
heart,  which  causes  that  organ  to  be  almost 

completely  enveloped  by  pulmonary  tissue,  *'- 

Tlie  left  lung  has  three  lobes,  and  the  right 
four,  separated  from  one  another  by  deep 
furrows,  which  are  generally  prolonged  to 
the  root.  The  lobules  are  small,  very  close, 
and  the  pulmonary  tissue  is  exceedingly 
compact.  (The  pulmonary  vesicles  are  pro- 
portionately largtr  than  in  Rmninants.) 

COMPARISON   OP    THE    LARYNX,   TRACHEA,   AND 
LINGS   OF   MAN   WITH   THOSE   OF   ANIMALS. 

1.  Larynx. — The  human  larynx  is  pro- 
portionally shorter  and  wider  than  that  of 
animals.  The  principal  cartilages  are  those 
which  have  been  already  studied ;  but  there 
are,  besi<les,  small  cartilaginous  bodies,  to 
which  special  names  have  been  given  :  these 
are  the  cartilages  of  Santorini  and  of  "NVris- 
berg.  The  facets  on  the  cricoid  for  articu- 
lation with  the  thyroid  are  placed  on  the 
small  cornua  detached  from  the  external  face 
of  the  cartilage.  The  thyroid  is  wiJe,  and 
piotects  the  anterior  face  of  the  larynx;  the 
angle  formed  by  tiie  alae,  which  is  more 
marked  in  the  male  than  the  female,  is  very 
piominent,  and  is  named  the  pomum  Adami. 
Tne  epiglottis  is  short,  broad  in  its  middle, 
and  rounded  at  its  summit,  something  like 
that  of  the  Carnivora.  The  muscles  are  the 
same  in  number  and  disposition  as  in  these 
animals :  but  there  is  distinguished  iin 
oblique  arytenoideus — a  fasciculus  of  the 
arytenoid,  which  crosses  its  fellow  to  form 
an  X  in  passing  from  the  upper 
border  of  one  arytenoid  cartilage 
to  the  lower  border  of  the  other. 


The  annexed  figure  shows 


LTJNG   OF   THE   SHEEP;    INFERIOR   VIEW.   ■ 

1,  Eight  lung;  2,  Left  lung;  3,  Trachea; 
4,  Heart ;  5,  Carotid  arteries  ;  6,  Posterior 
vena  cava. 

Fig.  242. 


1,  Right  ventricle;  2,  Left  ventricle; 
3,  Right  auricle ;  4,  Left  auricle  ; 
5,  Pulmonary  artery;  6,  Right 
pulmonary  artery;  7,  Left  pul- 
monary artery ;  8,  Ligament  of 
ductus  arteriosus ;  9,  Arch  of 
aorta ;  10,  Superior  vena  cava ; 
11,  Arteria  innominata  ;  12,  Right 
subclavian  vein,  with  the  artery 
behind  it ;  13,  Right  common 
carotid  artery  and  vein ;  14,  Left 
vena  innominata;  15,  Lefl  caro- 
tid artery  and  vein ;  16,  Left 
subclavian  vein  and  artery;  17, 
Trachea;  18,  Right  bronchus; 
19,  Left'  bronchus;  20,  20,  Pul- 
monary veins;  21,  Superior  lobe 
of  right  lung ;  22,  Middle  lobe ; 
23,  Inferior  lobe ;  24,  Superior 
lobe  of  left  lung;  25,  Inferior 
lobe. 


HUMAN   LUNGS   AND    HEART;    FRONT   VIEW. 


472 


TEE  RESPIRATORY  APPARATUS  IN  MAMMALIA. 


Internally,  the  human  larynx  has  no  subepiglottic  or  subarytenoid  sinus  like  that  of 
Solipeds,  though  it  has  lateral,  or  Morgagni's,  ventricles  that  ascend  a  little  to  the  outside 
of  the  superior  vocal  cords. 

2.  Trachea.— Z.  Bronchi.— There  is  little  difference  to  be  remarked  in  these.  The 
trachea  is  about  four  inches  long  and  about  one  inch  wide,  and  is  composed  of  about 
twenty  C-shaped  rings,  which  are  closely  united,  as  in  animals.  It  is  situated  in  the 
median  plane,  in  the  upper  part  of  the  neck,  where  it  is  embraced  by  the  lobes  of  the 
thyroid  gland ;  at  its  entrance  into  the  chest  it  deviates  slightly  to  the  right.  The  two 
short  canals  between  its  lower  extremity  and  the  lungs  are  the  bronchi;  the  right 
bronchus  is  the  shortest  and  widest,  and  lias  an  almost  horizontal  direction,  entering 
the  right  lung  at  the  fourth  dorsal  vertebra ;  the  left  is  longer  and  less  voluminous,  and 
reaches  the  corresponding  lung  at  the  fifth  vertebra. 

4.  Lunqs. — The  lungs  weigh  about  forty  ounces.  As  in  all  animals,  the  right  is 
more  voluminous  than  the  left,  and  is  divided  into  three  lobes  ;  the  latter  has  only  two. 
The  inferior  vena  cava  is  not  surrounded  by  pulmonary  tissue  ;  the  principal  lobes  are 
partitioned  into  lobules,  which  are  visible  on  the  surface,  and  on  the  limits  of  which 
are  deposited,  only  in  the  adult,  a  notable  quantity  of  pigmentary  matter,  that  gives  the 
lungs  the  appearance  of  a  chess-board.  There  is  nothing  to  be  said  respecting  their 
internal  conformation  and  structure. 


THE   GLANDIFORM   BODIES   CONNECTED   WITH   THE   EESPIRATORY    APPARATUS. 

1.  Thyroid  Body  (or  Gland). 

Tlie  thyroid  gland,  or  hody,  is  composed  of  two  oval  lobes  of  a  reddish- 
brown  colour,  and  is  situated  close  to,  and  behind,  the  larynx,  beside  the  two 
first  rings  of  the  trachea. 

These  two  lobes,  distinguished  as  right  and  left,  appear  at  first  sight  to 
be  perfectly  independent ;  but  a  less  superficial  examination  shows  them  to 
be  united  by  an  intermediate  portion  (the  isthmus),  which  passes  across  the 
anterior  face  of  the  trachea. 

Each  lobe  of  the  .thyroid  body  corresponds,  inwardly,  to  that  tube ; 
outwardly,  it  is  covered  by  the  subscapulo-hyoid  muscle. 

Structure. — The  thyroid  body 
■^'  "  ■  ■  is  composed  of  a  fibrous  envelope, 

and  a  proper  tissue  or  parenchyma. 
The  fibrous  envelope  is  composed 
of  slender,  but  strong  connective 
tissue ;  it  sends  from  its  inner 
face  a  large  number  of  thin  nu- 
cleated lamiufB  that  intersect  each 
other,  forming  spaces  in  which  the 
proper  tissue  is  contained. 

The  imrencliyma  is  divided  into 
lobules,  whose  presence  is  mani- 
fested on  the  surface  of  the  organ. 
They  are  composed  of  vesicles,  the 
shape  and  contents  of  which  vary 
considerably  with  age  and  situa- 
tion. In  the  foetus,  or  very  young 
animal,  they  are  round  or  ellip- 
tical, and  constituted  by  a  thin 
amorphous  membrane,  lined  by 
polygonal  cells  with  a  large  nu- 
cleus, and  containing  a  granular 
fluid.  In  the  adult,  these  vesicles 
are  deformed,  and,  after  being  distended,  several  are  confounded  together ; 


GROUP  OF   GLAND  VESICLES  FROM  THE   THYROID 
BODY   OF   A   YOUNG   SUBJECT. 

a,  Connective  tissue ;  6,  Basement  membrane  of 
the  vesicles ;  c,  Epithelial  cells. 


THE  THYROID  AND  THYMUS  GLANDS.  473 

the  epithelmm  is  less  evident  and  uniform,  tlic  contents  have  become  brown, 
and  hold  granules  and  nuclei  in  suspension,  and,  finally,  often  assume  the 
character  of  colloid  matter  in  becoming  viscous  and  of  a  yellow  tint. 

Vessels  and  nerves. — The  thyroid  body  is  remarkable  for  the  relatively 
enormous  volume  of  its  blood-vessels ;  the  arteries  chiefly  come  from  the 
thyro-laryngeal  branch — a  collateral  of  the  primitive  (or  common)  carotid 
( they  form  plexuses  on  the  vesicle  walls) ;  the  veins  pass  to  the  jugular. 
Its  nervous  filaments  are  from  the  first  and  second  cervical  pairs,  with  twigs 
from  the  sympathetic.     It  has  an  abundance  of  lymphatics. 

Functions. — The  thyroid  is  one  of  the  organs  classed,  in  a  somewhat 
arbitrary  manner,  in  the  ill-defined  category  of  ductless  or  blood-vascular 
glands.  Our  knowledge  of  its  use  is  as  uncertain  at  present  as  in  the 
infancy  of  anatomical  science.  So  that  we  can  say  nothing  more  on  this 
subject,  except  that  the  successive  or  simultaneous  excision  of  the  two 
lobes  in  the  Horse  do  not  appear  to  cause  any  derangement  in  the  animal's 
health. 

Neither  does  the  study  of  its  development  throw  any  light  on  its  func- 
tions. It  is  certainly  relatively  larger  in  the  fcetus  and  young  animals  than 
in  adults ;  but  the  diflerence  is  not  sufficiently  marked  to  authorize  us  in 
drawing  any  physiological  inductions  therefrom. 

2.  Tliymus  Gland. 

The  thymus  gland  is  a  transitory  organ,  only  present  in  the  foetus  and 
very  young  animals,  and  in  its  nature  closely  resembling  the  thyroid  gland. 
Like  it,  it  is  divided  into  two  lateral  lobes  placed  close  together  in  the 
middle  line,  under  the  lower  face  of  the  trachea,  partly  without  and  partly 
within  the  chest,  between  the  two  layers  of  the  anterior  mediastinum.  It  is 
elongated  from  before  to  behind,  of  a  whitish  colour,  and  uneven  or 
lobulated  on  its  surface  like  a  salivary  gland. 

Structure. — It  owes  its  uneven  aspect  to  its  lobular  structure,  for  it  is 
effectively  reduced  by  dissection  into  a  multitude  of  granular  lobules,  in  the 
centre  of  which  are  found  vesicular  cavities  containing  a  lactescent  fluid. 
The  vesicles  are  larger  than  those  of  the  thyroid  gland,  and  have  for  their 
walls  a  very  thin  layer  of  delicate  connective  tissue ;  they  are  filled  by  a 
mass  of  nuclei.  A  wide,  irregular  cavity  has  been  described  as  existing  in  the 
middle  of  each  lobe  (reservoir  of  the  thymus),  and  evidently  communicating 
with  the  vesicles  of  the  lobules,  as  it  contains  a  notable  quantity  of  the  same 
milky  fluid.  This  cavity  is  certainly  not  present  at  all  periods  ;  for  I  have 
not  met  with  it  in  two  yoimg  foetuses  now  lying  before  me  as  I  write.  But 
without  dwelling  on  this  particular  point,  we  may  notice  enormous  blood- 
vessels, lymphatics,  and  nerves,  as  complementary  elements  in  the  organisa- 
tion of  the  gland,  whose  structure  is  very  similar  to  that  of  the  proper 
glands,  though  differing  from  them  in  an  important  featm-e — the  absence  of 
an  excretory  duct. 

Nothing  positive  is  known  as  to  the  functions  of  the  thymus  gland ; 
it  is  only  certain  that  they  are  exclusively  related  to  the  development  of  the 
young  animal,  as  it  generally  disappears  some  months  after  birth,  though  it 
is  sometimes  found  in  adult,  and  even  in  very  aged  animals. 

(Its  functions  are  supposed  to  be  the  same  as,  or  analogous  to,  those  of  the 
thyroid.  Structurally,  the  organ  may  be  said  to  consist  of  an  assemblage  of 
hollow  glandular  lobules  joined  together  by  connective  tissue,  each  having 
a  cavity  which  opens  into  a  central  canal  that  has  no  duct,  and  being  lined 


474 


THE  BE8PIBAT0RY  APPARATUS. 


externally  by  an  almost  amorphous  membrane  which  divides  it  into  "  acini," 
or  gland-granules.  Separate  acini  are  often  observed  on  the  main  canal. 
Each  lobule  is  made  up  of  its  greyish-white,  soft  parenchyma  composed  of 
free  nuclei  and  small  cells,  and  has  a  minutely-distributed  capillary  plexus* 


Fig.  244. 


Ficr.  245. 


PORTION  OF  THYMUS 
GLAND  OF  CALF, 
UNFOLDED. 


Main  canal ;  b, 
Glandular  lobules ; 
c,  Isolated  gland 
granules  seated  on 
the  main  canal. 


COURSE  AND  TERMINATION  OP  THE  ABSORBENT 
DUCTS  OF   THE  THYMUS   GLAND   OF   A  CALF. 

1,  Internal  jugular  veins  ;  2,  Superior  vena  cava; 
3,  Thoracic  duct,  dividing  into  two  branches, 
that  again  unite  before  terminating  in  the  root 
of  the  left  jugular  vein ;  4,  The  two  thymic 
ducts ;  that  on  the  left  side  opening  into  the 
thoracic  duct,  and  the  right  into  the  root  of 
the  corresponding  jugular  vein. 


The  lymphatics  terminate  in  two  large  ducts  that  commence  at  the  upper 
extremities  of  the  lobes  of  the  gland,  the  thymic  ducts,  and  pass  down- 
ward to  terminate  at  the  junction  of  the  jugular  and  axillary  veins  at  each 
side.) 


DIFFERENTIAL  CHARACTERS   IN   THE   GLANDIFOKM   BODIES   ANNEXED   TO   THE   RESPIRATORY 
APPARATUS    IN   OTHER   THAN   SOLIPED   ANIMALS. 

The  thyroid  hody,  peculiar  to  Mammals,  is  more  developed  in  Ruminants,  Pachy- 
derms, and  the  Carnivora,  than  in  Solipeds.  The  two  lobes  are  closer  together,  and 
often  joined  by  the  thyroid  isthmus.  In  the  Pig  this  is  very  marked,  and  the  gland 
well  merits  its  name,  as  it  forms  a  veritable  shield  in  front  of  the  trachea,  towards  the 
lower  part  of  the  neck. 


THE  liESPIIiA  TORY  APPARATUS  IN  BIRDS.  475 

Tlie  thymus  ginnd  in  young  Euiuinauts  is  more  vohiniinous  than  in  the  Foal,  and  is 
situated  higher  up  iu  the  cltvIciI  region.  (^In  tlie  Carnivora,  it  is  divided  into  two  ))ranches  ; 
but  it  is  small,  and  completely  ludged  between  the  layers  of  the  anterior  mediasiiuum. 
It  persists  for  some  time  after  birtli,  and  seldom  disappears  in  less  than  a  year.) 

'comparison  of  the  glandiform  bodies  annexed  to  the  kespiuatoky  apparatus  in 

MAN   with   those   OF   ANIMALS. 

In  Man  the  two  lobes  of  the  thyroid  body  are  connected  by  an  isthmus,  and  the  upper 
extremity  of  the  lobe  is  carried  up  to  the  side  of  the  thyroid  cartilage.  The  isthmus 
often  gives  origin  to  a  process  of  variable  length  and  size,  called  tlie  pyramid  or  third 
lobe,  which  is  generally  situated  to  the  left  A  muscle  is  sometimes  found  connected 
with  the  isthmus  or  pyramid,  and  is  attached  above  to  the  body  of  the  os  hyoides  or  to 
the  thyroid  cartilage ;  it  has  been  named  the  levator  glandulie  thyroidx. 

The  thymus  gland  is  composed  of  two  lobes,  a  right  and  left,  only  joined  by 
connective  tissue,  and  having  no  structural  communication.  There  is  a  cervical  and  a 
thoracic  portion,  the  whole  extending  from  the  fourth  rib  as  high  as  the  thyroid  gland. 
After  birth  it  continues  to  enlarge  until  the  end  of  tlie  second  year,  and  begins  to 
diminish  between  the  eighth  and  twelfth  yeais  ) 


CHAPTER  II. 

THE    KESPIEATORY   APPARATUS    IN    BIRDS. 

The  organs  composing  the  respiratory  apparatus  of  birds,  offer  conditions  altogether 
special,  and  which  have  a  remarkable  influence  on  the  mechanism  of  respiration.  The 
modifications  imposed  upon  the  performance  of  this  function  will  be  indicated  after  an 
examination  of  the  tubular  apjjaratm,  which  carries  the  air  into  the  lung,  and  the 
characters  of  that  organ,  as  well  as  the  air  reservoirs  (or  sacs   annexed  to  it. 

The  Tubular  Appakatus. — When  this  apparatus  is  compared  with  that  of  Mammals, 
no  very  si  nsible  ditferences  are  observed — at  least  in  domesticated  birds. 

The  nostrils,  pierced  through  the  upper  mandible  of  the  beak,  have  no  membranous 
and  movable  wings,  and  the  nasal  fossa}  open  into  the  pharynx  by  a  long,  narrow  si  t 
behind  the  bony  palate.  A  transverse  row  of  small,  l.orny  papillae,  placed  at  the 
anterior  extremity  of  this  aperture,  represents  the  soft  palate. 

The  larynx  has  no  epiglottis  :  a  defect  which  dees  not  prevent  the  complete  occlusion 
of  the  glottis  during  the  passage  of  food,  as  the  laiyngeal  orifice  is  ciicumscribed  by  two 
lateral  lips  which  then  meet  in  the  most  exact  manner. 

The  trachea  is  composed  of  complete  cartilaginous  rings,  and  not  simple  arcs.  In 
song-birds,  the  last  ring  is  a  second  larynx,  ti.e  real  organ  which  produces  the  modulated 
voice  of  these  creatures ;  it  only  exists  in  a  rudimentary  condition  in  poultry,  however, 
the  last  tracheal  piece  in  them  being  slightly  dilated,  and  sliowing  at  the  origin  of  the 
bronchi  a  membranous  layer,  from  whose  vibration  results  cries  or  crowing.  Other 
singular  peculiarities  beionging  to  the  trachea  deserve  to  be  described  here,  if  they 
•were  not  the  exclusive  appanage  of  some  wild  fowl.  We  are  content  to  mention  the 
presence  of  the  bony  drum  found  at  the  terminal  extremity  of  the  trachea  in  the 
whistling  duck,  and  the  remarkable  convolutions  that  tube  forms  in  the  breast-bone  of 
Cranes  and  male  Swans. 

The  bronchi  only  show  incomplete  rings  in  their  structure.  They  pass  into  the  lung 
by  its  inferior  face,  towards  the  union  of  its  anterior  .and  two  posterior  thirds.  When 
describing  this  organ,  their  mode  of  ramification,  and  the  nature  of  the  relations  they 
bear  to  its  proper  tissue  will  be  considered. 

The  Lungs. — M.  Sappey,  in  the  remarkable  memoir  published  by  him  in  1847,  has 
described  them  as  follows :""  The  lungs  of  birds  are  situated  on  the  lateral  parts  of  the 
vertebrae  of  the  back — which  sepinate  them,  and  lying  against  the  arch  of  the  thoracic 
cavity,  to  which  they  adhere.  Their  ro.sy  colour  resembles  that  presented  by  these 
organs  in  Man  and  the  Mammalia  during  uterine  life,  and  for  seme  time  after  birth; 
they  are  especially  remarkable  for  their  restricted  volume,  which  scarcely  represents  an 
eighth  part  of  the  thoracic  capacity.  Their  contiguration  is  far  removed  trom  the 
conical  form  of  the  lungs  in  ISlammnls.  and  the  oval  1orm  of  the  same  organs  in  reptiles  ; 
they  are  semi-elliptical,  and  if  the  two  lungs  of  a  Mammal  were  opposed  base  to  base, 


476  THE  RESPIRATORY  APPARATUS. 

their  likeness  would  be  produced ;  to  obtain  the  ^  ame  results  with  the  lungs  of  a  reptile,  it 
is  liecussary  to  divide  them  m  the  direction  of  their  great  axis. 

"  This  shape  enables  us  to  distinguish  in  the  lungs  of  a  bird,  two  faces — a  convex 
and  concave ;  two  borders— an  external  and  internal ;  and  iwo  extremities — an  anterior 
and  posterior. 

'•The  convex  face,  also  named  the  dorsal,  costal,  or  swper/or /ace,  corresponds  inwardly 
to  the  dorsal  vertebrae,  and  outwardly  to  the  ribs  aud  the  intercostal  muscles ;  it  is 
exactly  moulded  on  the  walls  of  the  thorax,  and  as  the  ribs  protrude  on  tlie  internal  face 
uf  these  walls,  it  results  that  this  surface  of  the  lungs  is  marked  by  transverse  furrows 
which  give  it  a  lobulated  aspect ;  but  these  lobts  or  lobules  show  nothing  cummou  with 
those  composing  the  same  organ  in  Mammalia.  In  that  class,  the  existence  of  lobes  and 
lobules  is  an  established  fact,  and  is  caused  by  the  dichotomous  division  of  the  bronchi ; 
ia  birds,  it  is  only  apparent,  and  depends  on  the  diminished  thickness  of  the  lung  at 
each  rib.  This  face,  quite  imperforate,  is  covered  by  a  thin  layer  of  cellular  tissue,  which 
unites  it  to  the  sides  of  the  thorax. 

"The  plane  or  concave  face  looks  downwards;  it  is  in  relation  with  the  diaphragm, 
which  separates  it  from  the  viscera  of  the  thorax,  and  frcjm  the  abdomen  ;  from  this  arises 
its  other  names  of  inferior,  diaphragmatic,  or  visceral  face.  Like  the  preceding,  it  is 
covered  by  a  very  fine  layer  of  cellular  tissue,  which  forms  adhesions  with  the  diaphiagm ; 
but  it  differs  from  it  by  the  orifices  it  presents,  which  are  five  in  number,  and  constitute 
veritable  canals,  through  which  tho  air  paases  and  repasses  incessantly  to  and  from  the 
sacs,  and  from  them  to  the  lungs. 

"  The  borders  are  purallel  to  the  axis  of  the  body ;  the  internal  is  rectilinear,  thick, 
and  rounded  ;  the  external,  convex,  thin,  and  sharp. 

"  Of  the  two  extremities,  the  anterior,  whicli  is  very  acute,  occupies  the  receding 
angle  formed  by  the  spine  within  and  the  first  rib  without ;  the  posterior,  more  consider- 
able, has  a  rounded  form." 

In  regard  to  structure,  that  which  distinguishes  the  lung  of  birds  from  that  of 
Mammals  is  the  mode  of  distribution  and  termination  of  the  air-passages.  In  Mammals, 
the  large  bronchial  tubes,  placed  in  the  centre  of  the  lung,  send  their  divisions  towards 
the  surface  of  the  organ,  or  in  a  centrifugal  manner ;  in  birds  they  are  disposed  at  the 
peripliery  of  the  lung,  and  direct  their  ditf.  rent  ramifications  towards  the  centre,  or  in  a 
centripetal  fashion.  On  the  other  hand,  the  arboreal  division  of  the  bronchi  in  Mammals 
is  replaced  in  birds  by  penniform  ram'ficution.  Lastly,  the  terminal  bronchial  tubes 
instead  of  opening  into  a  series  of  closed  vesicles,  as  in  Mammals,  anastomose  with  one 
another  in  birds,  so  as  to  form  an  inextricable  arial  network. 

M.  Sappey  has  further  developed  the  knowledge  acquired  on  this  interesting  subject 
in  the  following  terms:  "Arrived  in  the  pulmonary  tissue,  it  (the  bronchial  trunk) 
dilates,  divides,  gradually  contracts  in  following  its  primary  direction,  and  in  this  way 
gains  the  posterior  extremity  of  the  organ,  where  it  terminates  by  opening  iato  the 
abdominal  reservoir. 

"  This  ajrifying  trunk,  therefore  presents  two  very  distinct  portions,  the  one  extra- 
pulmonary, the  other  intra-pulmonary.  The  first  offers  the  greatest  analogy  to  the 
bronchi  of  Mammalia  ;  it  is  membranous  internally,  elastic  and  fibrous  elsewhere, 
provided  outwardly  with  cartilaginous  rings,  which  embrace  three-fourths  of  its  circum- 
ference, and  is  lined  by  mucaus  membrane  characterised  by  its  pale  rose-colour,  and  its 
marked  adherence. 

"  The  second  differs  from  the  preceding  in  its  dimensions,  form,  and  structure. 
Owing  to  its  dilatation  at  its  entrance  to  the  lung,  its  dimensions  are  more  considerable, 
and  may  be  stated  as  three  to  two  of  the  extra-pulmonary  portion.  Beyond  this  enlarge- 
ment, it  diminishes  in  capacity  by  the  emission  of  branches,  losing  its  cylindrical  form 
to  assume  that  of  a  cone  with  a  truncated  summit.  Its  walls  are  almost  entirelv  destitute 
of  cartilaginous  rings,  so  that  the  origin  of  the  principal  conduits  is  constantly 
membranous. 

"  The  air-passages  arising  from  this  common  trunk  to  constitute  the  framework  of 
the  lung,  are  remarkable  for  their  uniformity  in  numb,  r,  form,  and  the  direction  they 
offer  in  all  classes  of  birds.  They  are  generally  twelve,  and  their  origin  is  thus  distri- 
buted :  four  arise  from  the  infernal  wall  of  the  trunk  by  a  series  of  orifices  placed  one 
after  the  other  ;  seven  are  detached  from  its  external  wall  by  a  second  series  of  orifices 
also  disposed  in  rows  ;  the  twelfth  springs  from  its  inferior  wall,  and  immediately  benda 
downwards  and  outwards  to  open  into  the  posterior  diaphragmatic  reservoir,  which  may 
be  considered  as  a  terminal  branch  of  the  principal  trunk. 

'•  All  the  canals  which  have  their  origin  from  these  linear  series  of  openings  on  the 
internal  and  external  walls  of  the  generating  trunk,  show  this  common  disposition  :  that 
from  their  commencement  they  pass  towards  the  periphery  of  the  lung,  that  they  divide 


THE  BESPIBATORY  APPARATUS  IN  BIRB8.  ill 

and  subdivide  at  this  periphery,  that  they  cover  it  with  their  ramifications,  and  do  not 
leave  it  to  enter  tlie  jDulmonary  parenchyma  until  their  volume  has  been  considerably 
reduced. 

"  The  conduits  leaving  the  orifices  situated  on  the  inner  wall  of  the  ferial  truihk 
ramify  on  the  inferior  face  of  tlie  lung ;  those  proceeding  from  the  echeloned  orifices  on 
the  outer  wall  are  distributed  on  the  opposite  face.  The  first  constitute  the  diaphrag- 
matic, and  the  second  the  costal  bronchial  tubes. 

"  The  dwphraginatie  bronchial  tubes,  four  in  number,  like  the  orifices  from  which 
they  originate,  may  be  distinguished  by  the  numerical  names  of  first,  second,  third,  and 
fom'th,  in  proceeding  from  before  to  behind ;  the  first  bronchus  is  carried  forward 
horizontally,  the  second  transversely  inwards,  the  third  obliquely  inwards  and  back- 
wards, and  the  fourth  directly  backwards.  In  view  of  their  divergent  direction,  ■which 
resembles  a  fan,  they  might  be  designated  as  the  anterior,  internal,  and  posterior 
diaphragmatic  bronchial  tubes  ;  and  to  distinguish  the  last  tvv-o,  the  more  voluminous 
one,  which  is  directed  backwards  and  inwards,  might  be  named  the.  great  posterior 
diaphragmatic  bronchus,  and  the  one  passing  directly  backwards  the  small  posterior 
diaphragmatic  bronchus. 

"  The  costal  bronchial  tubes,  seven  in  number,  may  be  also  designated  as  first,  second, 
third,  etc.,  in  proceeding  from  before  to  behind ;  parallel  at  their  origin,  and  in  juxta- 
position, like  the  pipes  of  an  organ,  they  separate  after  following  a  certain  course,  and 
afiect,  by  their  divergence,  tlie  fan-shape  already  observed  in  the  disposition  of  the 
diaphragmatic  bronchias.  Like  Ihe  latter,  they  become  peripheral  from  their  origin,  and 
spread  out  from  centre  to  circiunference.  The  first  is  carried  very  obliquely  upwards 
and  inwards,  to  attain  the  anterior  extremity  of  the  lung ;  all  the  branches  it  furnishes 
arise  from  its  anterior  wall,  and  those  which  are  nearest  its  origin  are  inflected  to  gain 
the  external  border  of  the  organ ;  the  succeeding  tubes  are  directed  forwards,  the  others 
forwards  and  inwards ;  while  all  proceed  to  meet  those  coming  from  the  anterior 
diaphragmatic  bronchus,  though  they  do  not  anastomose  with  them.  Coming  in  contact, 
they  plunge  into  the  pulmonary  tissue  in  such  a  way,  that,  when  a  lung  is  inflated,  we 
observe  between  these  two  orders  of  ramifications  a  very  manifest  groove,  which  is 
perfectly  distinct  from  those  due  to  the  protrusion  of  the  ribs ;  this  groove  evidently 
represents,  though  in  a  rudimentary  state,  the  interlobular  fissures  in  the  lungs  of 
quadrupeds. 

"The  second,  third,  and  fourth  costal  bronchise  follow  a  transverse  course,  and 
ramify  on  the  inner  border  of  the  lung;  the  fifth  and  sixth  incline  towards  the 
posterior  extremity  of  the  organ ;  the  seventh,  very  small,  reaches  this  extremity  and 
disappears. 

"  The  first  costal  bronchus  is  the  most  voluminous :  those  succeeding  it  gratlually 
diminish  in  calibre.  At  their  point  of  emergence  they  adhere  closely  to  the  ribs ;  all  are 
imperforate,  and  this  feature  essentially  distinguishes  them  from  those  occupying  the 
opposite  face. 

"  The  cunaliculi  furnished  by  these  principal  tubes  do  not  sensibly  differ  in  calibre 
in  the  various  bronchi :  all  offer  an  equal  diameter,  and  their  dimensions  are  only  in 
relation  to  the  total  volume  of  the  lung.  All  are  detached  at  a  right  angle  from  the 
pulmonary  wall  of  each  bronchus,  and  descend  perpendicularly  into  the  lung;  and  all, 
from  their  origin  to  their  termination,  preserve  the  same  diameter,  and  consequently  the 
same  cylindrical  form.  If  this  mode  of  ramification  be  compared  with  that  observed 
in  Mammals,  it  will  be  seen  to  differ  considerably.  In  the  latter  class,  the  air-passages 
affect  the  dichotomous  division  proper  to  the  arteries  and  veins,  the  result  of  which  is  a 
series  of  arboreal  canals  decreasing  in  capacity.  In  birds  only  two  kinds  of  conduits  are 
observed,  the  primitive  and  peripheral,  disposed  around  a  generating  axis  like  the  barbs 
of  a  feather  on  their  stalk ;  and  the  secondary  and  parenchymatous,  implanted  on  the 
pulmonary  walls  of  the  first,  like  the  hairs  of  a  brush  on  their  common  base.  These 
two  arrangements  are  evidently  similar,  except  that  the  peripheral  canals,  which  are  few, 
only  form  a  single  row  on  each  side  ;  while  the  canaliculi,  very  numerous,  form  several. 
Consequently,  it  may  be  said  that  the  mode  of  ramification  proper  to  Mammalia  is  essen- 
tially dichotomous,  and  that  observed  in  birds  essentially  penniform. 

"  Independently  of  the  canaliculi  arising  from  the  pulmonary  walls  of  the  diaphragm- 
atic and  costal  bronchiae,  there  are  others  which  spring  directly  from  the  generative 
trunk ;  but  in  their  dimensions,  direction,  form,  and  general  disposition,  they  do  not 
difi'er  from  the  preceding. 

•'  How  do  these  canals  terminate  ?  Notwithstanding  the  importance  of  this  question, 
it  has  been  generally  neglected  ;  though  its  solution  alone  may  furnish  the  analogies  and 
differences  necessary  for  the  parallel  which  has  always  been  attempted  to  be  established 
between  the  lungs  of  birds  and  those  of  other  vertebrates.    Om*  special  researches  on  this 


478  THE  RESPIRATORY  APPARATUS. 

point  nave  led  us  to  the  conclusion  that  all  tlie  canuliculi  open  into  one  another,  and 
by  this  anastomosis  constitute  an  extiicable  plexus  whose  various  parts  communicate 
with  ea'^h  other." 

Fhially,  it  may  be  mentioned  that  "  the  walls  of  the  pulmonary  canaliculi,  examined 
microscopically,  appear  to  be  covered  iiittrually  with  irregular  septa  which  circumscribe 
the  areolae,  and  give  them  a  c.  llular  aspect." 

The  Air-sacs.' — "  In  birds,  the  pulmonary  mucous  membrane  is  continued,  at  the 
level  of  the  orifices  in  the  lung,  into  the  uiriculiform  cavities  which  are  developed 
between  the  walls  of  the  thorax  and  the  abdomen  on  the  one  side,  and  the  thoracic  and 
abdominal  viscera  on  the  other.  These  air-reservoirs  exist  in  all  the  vertebrata  of  the 
second  class.  In  all,  they  are  situated  at  the  periphery  of  the  viscera  in  the  trunk,  in 
such  a  manner  that  Cams  hus  justly  observed  that  the  lungs  of  birds  inclose  h11  the 
other  viscera ;  so  that  when  they  are  distended  by  the  entrance  of  air,  they  generally 
depress  these  viscera  by  pushing  them  towards  the  median  plane.  In  all,  they  are 
independent  of  each  other,  and  freely  communicate  either  with  the  lung  by  a  single 
aperture,  or  with  the  bones  by  one  or  more  openings.  Lastly,  in  all  they  are  nine  in 
number. 

"  These  reservoirs  are  •  the  thoracic  sac,  situated  at  the  anterior  part  of  the  thorax  • 
two  cervical  reservoirs,  situated  at  the  base  of  the  neck;  two  anterior  diuphrurjinutic 
reservoirs,  placed  between  the  two  diaphragms ;  two  posterior  diaphragmatic  reservoirs, 
also  between  these  two  diaphragms,  but  behind  the  preceding  and,  lastly,  two 
abdominal  reservoirs,  placed  against  the  superior  wall  of  the  abdomen.  Of  these  nine 
reservoirs,  the  first  only  is  single  and  symmetrical ;  the  others  are  pairs,  and  similarly 
arranged  on  each  side  of  the  median  plane. 

"  The  thoracic  and  cervical  reservoirs  are  situated  beneath,  and  in  front  of,  the  lungs ; 
the  abdominal  reservoirs  lie  behind  these  organs,  and  the  four  diapliragmatic  sacs  at 
their  inferior  part  and  between  the  preceding;  heune  the  denomination  of  middle 
reservoirs  sometimes  applied  to  the  latter,  in  opposition  to  the  first,  which  are  named  the 
anterior  reservoirs,  ami  to  the  second,  called  the  posterior  reservoirs." 

External  Confokmation  of  the  RESEavoius. — 1.  Thoracic  reservoir  (Fig.  246,  2). — 
"  It  is  situated  above  the  clavicles  and  the  inter-clavicular  space,  in  the  cavity  of  the 
thorax,  which  it  extends  beyond  on  each  side  to  the  roots  of  the  wings,  around  the 
articulation  of  the  slionlder.  It  is  related  with  :  above,  the  trachea  and  oesophagus  on 
the  middle  plane,  the  lungs  and  the  origin  of  the  cervical  reservoirs  on  the  lateral  parts ; 
below,  with  the  sternum,  the  clavicles,  and  the  interclavicular  aponeurosis;  behind, 
with  the  heart  and  anterior  diaphragn^atic  reservoirs,  beneath  which  it  is  prolonged  by 
forming  on  each  a  long  point ;  in  front,  with  the  integuments  of  the  neck,  which  it  raises 
into  a  hemisphere  in  Palmipeds,  but  which  is  angularly  depressed  in  other  classes  ;  on 
the  sides,  with  the  sternal  ribs,  the  two  clavicles,  and  the  membrane  unitmg  them. 

"  The  prolongations  which  arise  from  the  lateral  parts  of  these  reservoirs,  and  cross 
the  walls  of  the  thorax  to  pass  around  the  articulation  of  the  shoulder,  are  tiiree  in 
number,  and  may  be  distinguished  into  inferior  or  subpectoral,  superior  or  subscapular, 
and  middle  or  humeral. 

"  The  subpectoral  prolonrjatidn  (Fig.  246,  d)  issues  from  the  thoracic  reservoir  by  an 
orifice  situated  behind  the  posterior  clavicle,  and  passes  beneath  the  tendon  of  the  great 
pectoral  muscle,  where  it  spreads  out  as  a  lenticular  cavity.  The  relations  it  contracts 
with  that  muscle  are  remarkable :  in  birds,  still  moie  than  in  Jlan  and  a  great  number 
of  quadrupeds,  the  tendon  of  the  great  pectoral  is  formed  of  two  parts,  one  direct,  the 
other  refleited  ;  it  is  between  thes  two  jwrtions  that  this  .small  air-sac  is  insinuated,  and 
where  it  forms  a  very  firm  connection  with  them ;  the  eife;t  of  which  is,  that  at  the 
moment  the  great  pectoral  muscle  contracts,  it  dilates  the  subjacent  cell  and  draws  into 
it  a  greater  quantity  of  air. 

"  The  subscapular  and  humeral  prolongation  communicate  with  the  principal  reservoir 
by  a  common  opening  placed  behind  the  small  adductor  muscle  of  the  humerus.  After 
leaving  this  orifice,  the  subscapular  sac  spreads  under  the  scapular  and  subscapular 
muscle,  which  it  separates  from  the  ribs  and  corresponding  intercostal  muscles  ,  it  is 
developed  more  particularly  in  a  longitudinal  direction. 

"  The  humeral  prolongation  occupies  the  axilla  ;  it  is  smaller  than  the  preceding,  of  a 
pyramidal  form,  and  opens  by  its  summit  into  an  infundibular  fossa,  which  leads  to  the 
canal  of  the  humerus. 

"The   thoracic  reservoir   differs  from  all  the  others  by   the  extremely  numerous 


'  What  is  said  relating  to  these  air-sacs  is  tnken  fmm  the  Memoir  of  M.  Sajipey — 
'Kecherches  Sur  I'Appareil  Respiratoire  des  Oiseaux,'  Paris,  1847. 


THE  BESPIRATORY  APPARATUS  IN  BIRDS.  479 

membranous  folds  which  partition  its  cavity.  The  membrane  formini::  it  being  continued 
on  itself,  every  organ  traversing  tlie  thorax  becomes  the  cause  of  a  fold  in  which  it  is 
imprisoned ;  and  as  the  thoracic  cavity  is  traversed  by  the  traelina  and  the  cosophai^us,  the 
muscles  which  move  the  inferior  larynx,  and  tlie  arteries  and  veins,  it  will  be  understood 
how  this  reservoir  should  become  irregular  in  consequence  of  these  various  partitions, 
and  nlso  why  the  other  a3rial  sa^-s  situated  between  the  viscera  and  the  walls  of  the 
thorax,  or  the  simple  contiguous  surfaces,  should  preserve  their  regular  and  proper 
form. 

**  The  thoracic  reservoir  communicates  with  the  lungs  by  an  infundibular  orifice, 
situated  on  the  external  side  of  the  embouchure  of  each  bronchus.  This  orifice  is 
dilated  during  inspiration,  by  the  contraction  of  the  two  first  fasciculi  of  the  pulmonary 
diaphragm." 

2.  Cervical  reservoirs  (Fig.  246,  1,  1). — "They  are  situated  above  the  preceding, 
and  the  inferior  part  of  the  neck  and  anterior  part  of  tlie  lung ;  inflated  after  removal 
from  the  neighbouring  parts,  they  resemble  two  cones,  whose  rounded  base  looks 
forwards,  and  whose  pediculated  summit  is  directed  backwards. 

"  Superiorly,  these  reservoirs  lie  ag  dnst  the  cervical  muscles ;  inferiorly,  they  corres- 
pond to  the  air-sac  of  the  thorax,  from  which  they  are  separated  by  tlie  trachea,  tlie 
oesophagus,  the  pneumogastric  nerves,  and  the  jugular  veins.  Inwardly,  they  are  in 
juxtaposition,  and  consequently  form  a  median  septum  which  includes  in  its  substance 
the  two  common  carotid  arteries.  Outwardly,  they  are  related  to  the  origin  of  the 
cervical  nerves,  to  each  of  which  they  furnish  a  small  sheath,  and  with  the  vertebral 
artery  which  they  surround,  but  do  not  contain  in  their  cavity,  as  well  as  with  a 
subcutaneous  muscle  and  the  skin.  By  their  summits,  they  communicate  with  the 
anterior  diaphragmatic  bronchus  ;  and  by  their  base  they  send  out  a  prolongation  wliich 
conducts  the  air  into  all  the  vertebrae  of  the  neck  and  back,  into  all  the  vertebral  ribs, 
and,  finally,  into  the  spinal  canal. 

"  In  their  cervical  portion,  these  prolongations  present  themselves  in  the  form  of  two 
canals  extending  from  the  base  of  the  cervical  reservoirs  to  the  base  of  the  cranium, 
where  they  terminate ;  parallel  and  contiguous  to  the  vertebral  arteries,  like  them 
they  are  lodged  in  the  canals  excavated  in  the  substiince  of  the  transverse  processes. 

"  From  their  external  part  arises,  at  the  six  last  cervical  vertebra;,  as  many  diverticuli, 
whicli,  lying  against  each  other,  pass  from  each  side  in  the  muscles  of  the  neck,  sur- 
rounded by  a  common  fibrous  envelope,  and  apparently  form  a  kind  of  canal  at  the 
inferior  part  of  this  region  ;  when,  however,  this  fibrous  membrane  is  removed,  it 
becomes  easy  to  isolate  them,  and  it  is  then  seen  that  they  are  completely  indeijendent, 
and  resemble  small  cornua.  Highly  developed  in  Palmipeds,  they  are  only  present  in  a 
rudimentary  state  in  the  other  classes. 

"  On  the  internal  side  of  these  conduits,  we  see,  at  the  level  of  each  vertebra,  one  or 
more  orifices  by  which  the  air  enters  their  interior ;  and  at  the  intervertebral  foramina 
another  orifice,  which  allows  it  to  pass  into  the  spinal  canal.  From  the  communication 
established  by  these  orifices  between  the  respiratory  apparatus  and  the  spinal  canal,  it 
follows  that  in  birds  the  cervical  region  istiaversed  by  tliree  atmospherical  ciu'rents — 
two  lateral  or  intertransverse,  parallel  to  the  vertebral  arteries ;  the  third  median  or 
interspinal,  parallel  to  the  spinal  cord. 

"Just  as  the  medullary  tissue  is  replaced  by  air  in  the  bones  of  birds,  so  might  it  be 
imagined  tliat  the  sub-arachnoidean  fluid  was  also  replaced  by  air  around  their  spinal 
cord ;  and  observation  justifies  the  correctness  of  this  prevision.  The  dura  mater,  whose 
capacity  is  so  superior  to  the  volume  of  the  marrow  in  Mammals,  exactly  measures  the 
volume  of  that  organ  in  birds;  so  that  there  does  not  exist  between  the  fibrous  and 
nervous  surfaces  any  space  for  an  accumulation  of  liquid  ;  this  anatomical  fact  is 
sufficient  to  demonstrate  the  absence  of  sub-arachnoidean  fluid  in  birds.  In  denying  the 
existence  of  this  fluid,  it  ought  to  be  added  that  in  this  class  of  vertebrata,  as  in  the 
preceding,  the  spinal  prolongation  is  covered  by  a  triple  envelope  ;  that  in  each,  between 
the  pia  mater  and  dura  mater,  is  found  a  thin  transparent  membrane,  which  is  lubri- 
cated by  a  serous  fluid ;  but  here  this  fluid  does  not  collect,  it  only  moistens  the 
arachnoid  membrane. 

"  Considered  in  their  dorsal  portion,  the  prolongations  springing  from  the  cervical 
reservoirs  offer  an  entirely  different  arrangement  to  that  already  noticed.  The  inter- 
spinal current,  having  entered  the  thora.^,  terminates  by  passing  into  the  first  dorsal 
vertebra ;  after  coursing  through  every  part  of  this  vertebra,  it  escapes  by  a  lateral 
orifi  e  into  a  small  sac  situated  between  the  two  first  ribs,  at  the  origin  of  the  "first  dorsal 
nerve ;  from  this  sac,  it  passes  into  the  second  vertebra  by  an  opening  placed  on  its 
anterolateral  part,  then  it  flows  back  from  this  into  a  new  air-sac  developed  between 
the  second  and  third  ribs ;  and  passing  in  the  same  manner  into  the  third  vertebra  to 


480 


THE  BESPIBATORY  APPARATUS. 


sweep  through  a  third  intercostal   sac,  it  arrives  nearer  and  nearer  the   last   dorsal 
vertebra.      In  their  dorsal   portion,   the   prolongations   emanating  from   the  cervical 

reseivoirs    thus   form   two   currents, 
Fig.  246.  though   these  are  constituted  alter- 

nately by  the  vertebraj  and  the  small 
air-sacs  placed  uu  their  lateral  aspect. 
At  the  same  time  that  these  sacs 
receive  the  au*  from  the  vertebraj  pre- 
ceding them,  and  transmit  it  to  those 
which  follow,  they  communicate  it  to 
all  the  vertebral  ribs. 

"  In  no  order  of  birds  do  the  xrial 
cm-rents  leaving  the  cervical  reser- 
voirs communicate  with  those  which 
circulate  in  the  cranium.  Liquids 
injected  either  by  the  ajrial  portion 
of  the  vertebral  canal  or  the  lateral 
prolongations  of  the  neck,  never  enter 
the  bones  of  that  cavity.  Thinking 
that  the  injection  might  perhaps 
penetrate  if  passed  in  the  opposite 
direction,  we  have  perforated  the 
bones  of  the  cranium,  and  to  the 
aperture  have  adapted  tlie  extremity 
of  a  steel  syringe  filled  with  mercury  ,- 
but  the  metal  did  not  reach  the  serial 
prolongations  of  the  neck.  From  this 
double  experiment,  we  concluded 
that  the  cranial  bones  have  no  com- 
munication with  the  respiratory  appa- 
ratus." 

3.  Anterior  diaphragmatic  reser- 
voirs (Fig.  246,  3).— "Placed  be- 
tween the  two  diaphragms,  they  cor- 
respond :  in  front,  to  the  thoracic 
reservoirs,  against  which  they  stand  ; 
behind,  to  the  posterior  diai^hragm- 
atic  reservoirs;  outwardly,  to  the 
ribs  and  intercostal  muscles ;  in- 
wardly, to  the  thoraco-abdominal 
diaphragm  and  oesophagus ;  below, 
to  the  most  distant  part  of  the  tho- 
racic reservoir;  above,  to  the  pul- 
monary diaphragm,  which  separates 
them  from  the  corresponding  lung. 
These  air-sacs  communicate  with  the 
lungs  by  a  circular  opening,  which 
originates  from  the  great  posterior 
diaphragmatic  bronchus ;  there  is 
1,  1,  Anterior  extremity  of  the  cervical  reservoirs;  often  a  second  opening  of  communi- 
2,  Thoracic  reservoir ;  3,  Anterior  diaphragmatic  cation  beyond  the  embouchure  of  the 
reservoir;  4,  Posterior  ditto ;  5,  Abdominal  reser-  -        -  .  ... 

voir. — a,  Membrane  forming  the  antei'ior  dia- 
phragmatic reservoir;  6,  Membrane  forming  the 
posterior  ditto. — 6,  Section  of  the  thoraco-abdomi- 
nal diaphragm. — d,  Subpectoral  prolongation  of 
the    thoracic    reservoir ;    <?,    Pericardium ;   /,  /, 


GENERAL  VIEW  OF  THE  AIR  RESERVOIRS  OF  THE 
DUCK,  OPENED  INFERIORLY ;  ALSO  THEIR  RELA- 
TIONS WITH  THE  PRINCIPAL  VISCERA  OF  THE 
TRUNK. 


trunk ;  this  reservoir  is  the  only  one 
which  receives  air  from  the  lung  by 
a  double  orifice." 

4.  Posterior  diaphragmatic  reser- 
voirs (Fig.  246,  4). — "  Oval-shaped 
like  the  preceding,  and  situated  like 


Liver;    g,   Gizzard;    h,    Intestines;    77z,    Heart ;    them  in  the  interval  which  separates 


n,  n,  Section  of  the  great  pectoral  muscle  above 
its  insertion  into  the  humerus ;  o.  Anterior 
clavicle ;  p,  Posterior  clavicle  of  the  right  side 
cut  and  turned  outwards. — From  M.  Sappey's 
work. 


the  two  diaphragms,  these  air-sacs 
are  in  contact,  by  their  anterior  part, 
with  the  anterior  diaphragmatic  re- 
servoirs, with  which  they  form  a  ver- 
tical and  transverse  septum.  Some- 
times this  septum  is  carried  a  little 
more  forward,  and  then  the  anterior  reservoir  is  smaller;    this  is  most  frequent  in 


THE  BESPIBATORY  APFARATUS  IN  BIRDS.  481 

Palmipeds.  At  other  times  it  inclines  backwards,  and  the  anterior  reservoir  is  iaro-er ; 
this  arrangement  is  peculiar  to  the  Gallinacai.  And,  lastly,  this  pariition  divides  the 
intercepted  space  between  the  diaphragms  into  two  equal  cavities ;  rapacious  birds  offer 
numerous  examples  of  this. 

"Behind,  these  reservoirs  stand  against  the  abdominal  sacs,  from  which  they  are 
separated  by  the  thoraco-abdominal  diaphragm  :  below,  they  respond  to  the  sternal  ribs 
and  the  lateral  parts  of  the  sternum;  above,  to  the  pulmonary  diaphragm;  inwards, 
to  the  thoraco-abdominal  diaphragm  ;  outwards,  to  the  vertebral  ribs  and  intercostal 
muscles. 

"  A  parabolic  opening,  situated  in  the  middle  part  of  the  external  border  of  the  lung, 
or  a  little  more  behind,  establishes  tiieir  communication  with  that  organ  This  oriUce, 
which  is  remarkable  for  its  great  dimensions,  occupies  the  extremity  of  a  voluminous 
bronchial  tube  which  follows  th  j  direction  of  the  generating  trunk,  and  in  such  a  manner 
that  this  trunk  appears  to  pass  directly  towards  the  posterior  diaphragmatic  reservoir, 
and  to  open  as  a  canal." 

5.  Abdominal  reservoirs  (Fig.  246,  5). — "  The  two  air-^acs  situated  in  the  abdomen 
present  themselves,  when  inflated,  as  two  enormous  bladders,  the  capacity  of  each 
differing  but  little  from  the  volume  of  the  trunk.  Situated  between  the  superior 
and  lateral  parietes  of  the  abdomen  on  one  side,  and  the  abdominal  viscera  on  tue 
other,  they  cannot  be  dilated  without  driving  the  intestinal  mass  downwards  and 
inwards. 

"  Their  anterior  extremity,  continuous  with  the  lung,  is  somewhat  inflected  to  pass 
under  the  fibrous  arch  extending  from  the  spine  to  the  pelvi.s. 

"  Their  posterior  extremity,  dilated  and  volumnious  responds  to  the  cloaca.  Out- 
wardly, they  adhere  by  cellular  tissue  to  the  thoraco-abdominal  diaphragm,  the  parietes 
of  the  abdomen,  and  those  of  the  pelvis.  Inwardly,  they  are  in  contact  with  the  intes- 
tinal mass  and  the  testicles  or  ovaries.  Below  and  in  fnmt,  they  rest  on  a  fibrous 
septum,  which  in  all  birds  divides  the  abdomin  d  cavity  into  two  smaller  cavities:  one 
anterior,  which  represents  the  abdomen  and  lodges  the  liver,  the  other  posterior,  which 
represents  the  pelvis  and  contains  the  stomach  and  intestines.  This  fibrous  septum  is  ex- 
tremely remarkable  in  large  birds,  particularly  the  Ostrich,  in  which  it  has  been  described 
by  Perrault  as  a  transverse  diaphragm ;  it  is  inserted  into  the  entire  circumference  of  the 
pelvic  bones,  and  sustains  the  stomach  as  well  as  the  intestinal  tube.  Below  and 
behind,  the  abdominal  reservoirs  lie  on  the  intestines.  Above,  these  sacs  cover  the 
inferior  face  of  the  kidneys,  and  there  furnish  three  prolongations :  1,  A  suprarenal 
prolongation  ;  2,  Two  femoral  prolongations. 

"  The  suprarenal  prolongation  leaves  the  principal  reservoir  at  tlie  postero-external 
part  of  the  kidneys ;  from  thence  it  passes  obliquely  upwards  and  forwards,  to  spread 
over  the  superior  surface  of  the  kidney,  which  it  depresses  when  the  abdominal  sac  is 
inflated.  Arrived  at  the  internal  border  of  the  kidneys,  these  prolongations  are  intro- 
duced between  the  transverse  processes  of  the  sacral  vertebrae,  and  ascend  from  behind 
forwards  to  the  height  of  the  two  first  dorsal  vertebrae,  forming  two  triangular  canals 
situated  above  the  sacrum,  in  the  sacral  channels,  and  separated  from  one  another  by  a 
series  of  corresponding  spinous  processes.  The  suprarenal  prolongations  are  not 
present  in  all  birds ;  they  are  particularly  observed  in  the  Gallinacse  and  diurnal 
rapacious  birds.  In  some  Palmipeds,  the  Swan  for  exami^le,  they  are  equally  developed ; 
in  the  0.strich,  they  are  replaced  by  the  supraspinal  canals. 

"  The  femoral  prolongations  are  two  in  number — an  anterior  small  and  a  posterior 
large;  they  arise  from  the  abdominal  reservoir  at  the  cotyloid  cavities,  and  leave  the 
pelvis  in  traversing  the  bony  opening  through  which  the  crural  vessels  pass ;  after  clear- 
ing the  limits  of  these  cavities,  they  spread  around  the  coxo-femoral  articulation,  and 
terminate  in  a  cajcum  in  the  majority  of  birds.  In  diurnal  birds  of  prey,  they  commu- 
nicate with  the  femoral  canal  by  an  orifice  situated  at  the  anterior  part  of  the  great 
trochanter.  These  prolongations,  very  developeil  in  tlie  Ostrich,  also  open  in  it  into  the 
femoral  cavity ;  it  is  not  without  surprise  that  we  see  this  arrangement,  which  is  peculiar 
to  birds  remarkable  for  their  rapidity  and  power  of  flight,  also  present  in  those  to  which 
serial  locomotion  has  been  entirely  denied.  The  abdominal  reservoirs  communicate  with 
the  lung  by  an  orifice  situated  beneath  the  fibrous  arch  of  the  diaphragm,  and  disposed 
like  the  rose  of  a  watering-can." 

Communication  of  the  Reservoirs  with  the  Bones. — "  The  communications  of  the 
respiratory  apparatus  with  the  skeleton  in  birds  are  extremely  numerous.  Wc  will 
successively  examine  those  belonging  to  each  reservoir. 

"  The  bones  which  receive  air  from  the  thoracic  reservoir  are  :  1,  The  anterior  clavicle, 
which  is  perforated  at  its  two  extremities;  2,  The  posterior  clavicles,  which  are  also 
perforated  a  little  below  their  scapular  extremity    3,  The  sternum  which  presents  two 


482  THE  RESPIBATOBY  APPABATUS. 

series  of  openings— the  middle  ones  that  conduct  the  air  into  tlie  sternal  ridge,  and  the 
lateral  ones,  very  small,  six  to  eight  in  number,  corresponding  to  the  intercostal  spaces; 
4,  The  scapula},  which  olier  one  or  more  apertures  at  tlieir  anterior  extremity,  and  receive 
the  air  for  the  subscapular  prolongation  ;  5,  The  humerus,  which  obtains  the  air  for 
the  humeral  prolongation  by  a  fossa  situated  at  tlie  inferior  and  internal  part  of  its 
articular  head  ;  G,  The  sternal  ribs,  which  allow  the  atmosphere  to  penetrate  by  small 
openings  at  their  inferior  extremities.  To  sum  up,  eight  bones,  without  reckoning  the 
sternal  ribs  whose  number  varies,  receive  the  air  which  fills  them  from  the  thoracic 
reservoir. 

"  The  cervical  reservoirs  conduct  the  air :  1,  To  all  the  cervical  vertebrse ;  2,  To  all  the 
dorsal  vertebrte ;  3,  To  all  the  vertebral  ribs.  The  vertebrje  of  the  neck  are  serated  in 
their  anterior  part  by  the  currents  which  accompany  the  vertebral  artery,  and  in  their 
posterior  part  by  the  interspinal  current.  The  tirst  obtain  entrance  to  the  anterior 
segment  by  one  or  more  orifices  made  in  the  inner  wall  of  the  intertransverse  canals ; 
the  median  current  penetrates  the  posterior  segment  by  two  orifices,  a  right  and  left, 
situated  on  the  inner  and  medullary  wall  of  that  segment.  The  first  vertebra  of  the 
back  is  provided  with  air  in  the  same  manner,  by  the  middle  and  lateral  currents  of  the 
neck.  This  air,  after  passing  through  the  fij-st  vertebra,  leaves  by  its  lateral  parts,  to 
enter  a  small  sac ;  from  this  it  goes  into  the  superior  part  of  the  second  vertebra,  escapes 
from  this  by  its  lower  portion,  to  be  received  into  a  lateral  sac,  and  so  on  to  the  last  dorsal 
vertebra.  These  sacs  also  supply  the  vertebral  ribs  with  air,  which  enters  them  by  very 
small  apertures  situated  at  their  spinal  extremity. 

"  The  diaphragmatic  reservoirs  have  no  bony  communications.  The  abdominal 
reservoirs  supply  :  1,  The  sacrum  ;  2,  The  coccygeal  vertebraj ;  3,  The  iliac  bones  ;  4,  The 
femurs.  The  air  traversing  the  sacrum,  coccyx,  and  ileum,  comes  directly  Irom  the  supra- 
renal prolongations,  and  that  filling  the  femoral  cavity  from  the  femoral  prolongations. 
In  this  enumeration  of  the  communications  between  the  skeleton  and  the  respiratory 
apparatus,  we  have  taken  as  a  type  the  most  serated  skeleton  :  that  of  diurnal  birds  of 
prey,  like  the  eagle,  kite,  hawk,  etc. ;  the  bones  which  communicate  with  the  air- sacs 
are  not  so  numerous  in  the  other  classes.  In  this  respect,  they  may  be  ranged  in  three 
categories  :  1,  Those  which  are  auriferous  in  all  classes ;  2,  Those  in  certain  classes  only ; 
3,  And  those  which  are  not  so  in  any  class.  The  bones  always  serated  are  the  cervical 
and  dorsal  vertebraj,  the  sternum,  and  we  may  add  the  humerus,  though  it  is  not  so  in 
the  Ostrich.  Those  ajrated  in  some  classes  only  are  :  the  furculum,  clavicles,  scapul£e, 
vertebral  and  sternal  ribs,  the  sacrum,  coccyx,  and  femurs.  And  the  bones  which  are 
never  asrated  are  those  of  the  tore-arm  and  hand,  the  leg  and  foot." 

Structure  of  the  Reservoirs. — The  walls  of  these  cavities  are  essentially  formed  by  a 
thin  cellulo-serous  membrane,  strengthened  in  some  places  by  an  external  envelope  of 
elastic  fibrous  tissue.  Long,  thin  blood-vessels  are  distributed  to  the  substance  of  these 
walls  ;  they  do  not  belong  to  the  pulmonary,  but  to  the  general  circulation,  the  arteries 
being  derived  from  the  aorta,  and  the  veins  opening  directly  or  indirectly  into  the  venae 
cava.     No  lymphatics  have  been  found  in  the  air-sacs. 

Mechanism  of  Respiration  in  Birds. — The  anatomical  arrangement  described 
above  difiers  in  so  many  respects  from  that  existing  in  Mammals,  that  it  ought  to  bring 
about  important  modifications  in  the  mechanism  of  respiration.  It  does  not  come 
within  our  scope  to  write  the  history  of  these  modifications ;  but  we  cannot  dispense 
with  indicating,  in  a  summary  way,  their  principal  characters,  in  order  to  make  known 
in  a  general  manner  the  signification  of  the  special  organisation  this  apparatus  offei's  in 
birds. 

We  remark,  in  the  first  place,  that  the  slight  mobility  of  the  vertebial  ribs,  and  the 
adhesion  of  the  lung  to  their  inner  face,  only  allows  of  a  very  slight  dilatation  of  that 
viscus  during  insjiiration.  And  the  entrance  of  air  into  the  pulmonary  tissue  is  not 
due  to  this  dilatation ;  it  is  due  to  the  dilatation  of  the  diaphragmatic  reservoirs ;  the 
position  of  these  effectively  admits  of  their  expansion,  by  the  play  of  the  inferior  on  the 
superior  ribs.  The  air  is  then  drawn  into  their  cavity  after  traversing  the  larger 
bronchial  tubes  which  open  into  them,  and  also  after  passing  across  a  certain  region  of 
the  capillary  network  formed  by  the  canaliculi,  where  it  comes  into  mediate  contact 
with  the  blood,  and  is  submitted  to  the  necessary  transformations.  The  atmosphere, 
therefore,  arrives  in  the  diaplira^matic  sacs  partly  pure  and  partly  altered  by  its  contact 
with  the  blood.  During  expiration,  it  again  resumes  the  course  it  followed  on  its 
introduction,  traverses  a  second  time  the  lung,  and  is  thus  respired  once  more  before 
being  expelled  from  the  body.  It  is,  therefore,  obvious  that  the  hsematosic  transforma- 
tions accomplished  in  the  lung  take  place  during  the  two  acts  of  respiration — inspiration 
and  expiration. 

In  studying  the  part  that  the  other  reservoirs  play  in  this  function,  M.  Sappey  has 


TEE  RESPIBATOBY  APPARATUS  IN  BIRDS.  483 

been  able  to  prove  that  they  act  as  antagonists  to  the  first,  by  coiitractino;  during  inspira- 
tion and  expaniliug  in  expiration.  No  doubt,  at  the  time  of  the  contraction  of  the  middle 
reservoirs,  a  small  quantity  of  the  air  they  contain  is  driven  back  into  the  anterior  and 
posterior  sacs  in  passing  across  the  lung ;  and  without  doubt,  also,  these  h.tter  give  a  part 
of  their  contents  tu  the  diiphragmatic  sacs  at  the  moment  of  the  expansion  which  draws 
the  air  into  these  reservoirs.  M.  Sappey  has  also  noted  that  these  contents  are  always 
termed  of  entirely  vitiated  air,  while  the  air  of  the  middle  reservoirs  has  only  been 
partially  respired. 

It  is  necessary  to  add  that  the  functions  of  the  air-sacs  do  not  cease  here  ;  for  it  has 
been  demonstrated  that  they  exercise  a  very  marked  influence :  1,  On  locomotion,  by 
diminishing  the  weight  of  the  body,  and,  by  their  position,  rendering  equilibrium  more 
stable ;  2,  On  the  voice,  the  extent  and  power  of  which  they  augment. 


BOOK  IV. 

Urinaey  Apparatus. 

This  apparatus,  though  simple,  yet  plays  a  very  important  part  in  the 
animal  economy,  as  it  is  charged  with  the  duty  of  eliminating  from  the  hlood, 
along  with  the  superfluous  water  and  other  accessory  substances,  the  excre- 
mentitial  azotised  products  resulting  from  the  exercise  of  the  vital  functions. 
These  products  we  find  in  the  uriue — the  liquid  secreted  by  the  kidneys,  and 
which  is  carried  by  the  ureters  into  a  special  reservoir,  the  bladder,  where  it 
accumulates,  and  whence  it  is  expelled  from  the  body  by  the  urethral  canal,  at 
periods  more  or  less  distant,  according  to  the  requirements  of  the  animal. 

The  kidneys,  the  essential  organs  of  urinary  depuration,  will  be  first 
studied  ;  then  the  excretory  apparatm  ;  and,  finally,  a  brief  notice  will  be 
given  of  tlie  sujjrarenal  capsules — small  appendicular  bodies  annexed  to  the 
kidneys,  and  whose  function  is  not  yet  determined. 

Preparation. — Place  the  animal  in  the  first  position,  and  remove  one  of  the  posterior 
limbs.  Take  out  the  intestines,  adoi)tinL?  the  precautions  indicated  at  page  383.  Saw 
through  the  pelvic  symphysis,  as  well  us  the  neck  of  the  ilium  on  the  side  opposite  the 
remaining  abdominal  member,  removing  tlie  coxal  portion  between  these  sections.  The 
pelvic  cavity  being  now  opened,  the  urinary  apparatus  is  exposed,  and  to  complete  the  pre- 
paration it  is  necessary  to:  1,  Remove  ihe  peritoneum,  to  show  that  the  lu'iuary  appara- 
tus is  situated  external  to  that  membrane;  2,  Free  the  ureters  an  1  kiilnej^s  from  the 
cellulo-adipose  tissue  surrounding  them,  but  retaining  the  vessels  of  tlie  latter,  and 
leaving  undisturbed  their  relations  with  the  pancreas  and  suprarenal  capsules;  3,  Inflate 
the  bladder,  and  dissect  its  neck,  taking  care  to  preserve  the  orbicular  peritoneal  fold 
which  envelops  its  anterior  cul-de-sac. 

In  the  male,  the  inflation  of  the  bladder  is  very  simple,  and  requires  no  directions. 
In  the  female,  however,  it  is  requisite  first  to  close  the  meatus  urinarius,  which  is  ac- 
complished by  drawing  its  two  lips  towards  the  entrance  to  the  vulva,  by  means  of  two 
chain-hooks,  passing  two  pins  through  their  muciius  membrane,  and  tying  a  liuatuie 
behind  thrse  ;  the  bladder  is  then  inflated  by  the  ureter. 

Inilependently  of  this  dissection  in  situ,  it  is  ailvi^able  to  examine  the  urinary 
apparatus  when  isolated,  and  laid  arranged  upon  a  table,  as  in  Fig.  2-17.  We  can  then 
study  :  1.  By  dissection,  the  structure  of  the  kidneys  and  arrangement  of  the  pelvis 
reualis  ;  2,  The  mode  of  termination  of  the  ureters  ;  3,  The  interior  of  the  bladder. 

1.  The  Kidneys.     (Figs.  182,  247.) 

Situation. — These  are  two  glandular  organs  situated  in  the  abdominal 
cavity,  to  the  right  and  left  of  the  sublumbar  region,  lying  against  the 
great  psoas  muscles,  and  maintained  in  that  position  :  1,  By  an  envelojie 
of  cellulo-adipose  tissu.^  ;  2.  By  the  peritoneum,  which  passes  beneath  tbem  : 
3,  By  the  pressure  of  the  digestive  organs  contained  in  the  abdominal  cavity. 

Their  situation  is  not  absolutely  alike,  for  the  ric/ht  comes  forward  to 
beneath  the  two  last  ribs,  while  the  left  scarcely  reaches  beyond  the  eighteenth 
rib.     The  latter  is  therefore  more  posterior  than  the  former. 

External  conformation. — Studied  externally,  the  kidneys  present  a  special 
form,  which  often  serves  as  a  term  of  comparison,  and  resembles  more  or  less 
that  of  a  haricot  bean,  or  the  heart  on  a  playing  card.  The  latter  con- 
figuration is  most  frequently  noticed  in  tlie  right  kidney,  the  left  being 
generally  like  the  first. 


IHE  KIDNEYS. 


485 


Flattened  on  both  sides,  the  kidneys  show  two  perfectly  smooth  faces, 
the  inferior  of  which  always  exhibits  a  variable  number  of  furrows  which 


Fig.  247. 


A,  Left  kidney  ;  B,  Right  kid- 
ney ;  a,  b,  Ureters ;  c,  C, 
Supra-renal  capsules ;  D, 
Bladder ;  E,  E,  Testicles ; 
e,  Head  of  the  epididymus ; 
e',  Tail  of  the  epididymus ; 
F,  Deferent  canal ;  G,  Pel- 
vic dilatation  of  the  defe- 
rent canal  j  H,  Left  vesicula 
seminales ;  the  right  has 
been  removed,  along  with 
the  deferent  canal  of  the 
same  side,  to  show  the  in- 
sertion of  the  uretei's  into 
the  bladder;  i.  Prostate; 
J,  Cowper's  glands ;  K, 
Membranous,  or  intra-pel- 
vic  portion  of  the  urethral 
canal;  L,  Its  bulbous  por- 
tion; M,  Cavernous  body  of 
the  penis ;  m,  m,  Its  roots  ; 
N,  Head  of  the  penis. — 1, 
Abdominal  aorta ;  2,  2,  Ar- 
teries (renal)  giving  oft"  the 
principal  capsular  artery , 
3,  Spermatic  artery,  4^ 
Common  origin  of  the  umbilical  and  arteries  of  the  bulb;  5,  Umbilical  artery  6, 
Its  vesical  branch  ;  7,  Internal  artery  of  the  bulb  ;  8,  Its  vesico-prostatic  branch. 
34 


SUPERIOR  AND  GENERAL  VIEW  OF  THE  GENITO- 
URINARY APPARATUS  IN  THE  MALE,  WITH  THE 
ARTERIES. 


486  THE  UBINABY  APPARATUS. 

lodge  the  arteries ;  the  right  kidney  has  always  a  special  furrow  for  the 
ureter.  Each  kidney  has  a  cii'cumference  divisible  into  three  borders,  only 
the  internal  of  which  offers  a  certain  interest.  This  is  deeply  notched,  to 
form  the  fissure  or  hilus  of  the  kidney,  which  lodges  the  vessels  and  nerves 
of  the  organ,  as  well  as  the  origin  of  its  excretory  canal. 

Weight. — The  kidneys  vary  much  in  weight  in  individuals.  The  right 
is  always  more  voluminous  and  heavy  than  the  left,  its  average  weight 
being  27  ounces,  while  that  of  the  last  is  25  ounces. 

Relations. — The  relations  of  these  two  glands  with  the  neighbouring 
parts  ought  to  be  particularly  examined.  The  right  kidney  corresponds,  by 
its  upper  face,  to  the  great  psoas  muscle,  the  muscular  portion  of  the 
diaphragm,  and  to  the  last,  or  even  the  second-last  rib.  Its  inferior  face, 
incompletely  covered  by  peritoneum,  adheres,  for  the  greater  part  of  its 
extent,  either  to  the  pancreas  and  supra-renal  capsule,  or  to  the  base  of  the 
caecura,  by  means  of  a  loose  and  abundant  cellular  tissue.  The  internal 
border  is  in  contact  with  the  posterior  vena  cava  and  the  small  psoas 
muscle ;  the  anterior,  with  the  base  of  the  right  lobe  of  the  liver  and  the 
lobule  of  Spigel  (lobus  Spigelii),  through  the  medium  of  the  peritoneum ; 
the  posterior  border  is  enveloped  in  peritoneum.  The  left  kidney  affects,  by 
its  superior  face,  the  same  connections  as  the  right,  except  in  its  relation 
with  the  second  last  rib.  Its  inferior  face  is  almost  entirely  covered  by 
peritoneum,  and  responds,  in  front  and  inwardly,  to  the  supra-renal  caj^sule. 
The  internal  border  is  margined  by  the  aorta ;  the  anterior  touches  the  base 
of  the  spleen  and  the  left  extremity  of  the  pancreas ;  the  posterior  is,  like 
the  inferior  face,  in  contact  with  the  serous  membrane  of  the  abdominal 
cavity. 

Internal  conformation. — If  a  horizontal  section  is  made  of  the  kidney,  it 
will  be  found  to  possess  a  cavity  called  the  renal  pelvis,  into  which  the  urine 
secreted  by  the  gland  flows,  and  at  which  the  ureter  commences.  Placed  in 
the  middle  of  the  kidney,  near  the  hilus,  the  pelvis  is  elongated  from  before 
to  behind,  and  depressed  from  above  to  below.  Within  it  is  remarked  a 
wide  infundibulum,  the  origin  of  the  ureter  (the  sinus  renalis).  Opposite  to 
this  funnel-shaped  space  is  a  very  prominent  crest  that  runs  along  the  whole 
length  of  the  external  side  of  the  pelvis,  and  on  which  are  noticed  the 
orifices  of  the  uriniferous  tubes  ;  these,  by  pressing  the  tissue  of  the  kidney 
with  the  fingers,  can  be  made  to  pour  out  the  urine  accumulated  in  them. 
The  renal  cavity  forms  some  very  small  diverticuli  opposite  the  infundibulum, 
the  largest  of  which,  situated  before  and  behind  the  latter,  are  named  the 
arms  of  the  pelvis. 

This  cavity  is  lined  by  a  transversely  plicated  mucous  membrane, 
continuous  with  that  of  the  ureter,  and  is  covered  with  the  epithelium  of  the 
uriniferous  tubes  which  open  on  the  border  of  the  crest. 

Structuee. — The  kidneys  present  for  study  in  their  structure :  1,  An 
enveloping  tunic  ;  2,  Their  proper  tissue  ;  3,  A  cavity  named  the  renal  pelvis, 
into  which  the  urine  secreted  in  the  glandular  tissue  flows,  and  which  serves 
as  the  origin  of  the  ureter. 

1.  Enveloping  Tunic. — This  is  a  fibrous  membrane,  intimately  united 
to  the  proper  substance  of  the  kidney,  into  which  it  sends  a  multitude  of 
prolongations,  and  is  folded  around  the  blood-vessels  in  such  a  manner  as  to 
form  sheaths,  which  enter  with  them  into  the  organ.  (Some  authors — 
among  them  Leyh — describe,  in  addition  to  this  capsula  propria,  a  thin  layer 
formed  by  the  condensed  areolar  matrix  of  the  kidiiey,  from  which  it  can  be 
easily  torn.) 


THE  KIDNEYS. 


487 


Proper  Tissue. — The  glandular  tissue  of  the  kidneys  (areola  parenchyma 
or  matrix)  has,  externally,  a  reddish-brown  colour,  more  or  less  deep  in 
different  individuals.  It  is  dense  and  friable,  and  easily  torn  when  deprived 
of  its  fibrous  cai)sule.  Its  substance  is  not  everywliere  homogeneous  :  very 
dark-coloured  externally,  where  it  forms  the  cortical  layer,  it  becomes 
whiter  around  the  pelvis,  where  it  consitutes  the  medullary  layer  ;  where  the 
latter  comes  in  contact  with  the  former,  and  sometimes  even  near  the  pelvis, 
it  assumes  a  tint  like  that  of  wine. 

These  two  portions  are  not  well  defined,  but  penetrate  each  other 
reciprocally,  so  as  to  compose,  at  their  point  of  junction,  irregular  festoons, 
very  readily  perceived  in  a  horizontal  section  of  the  kidney  (Fig.  248). 

The  cortical  is  also  distinguished  from  the  medullary  substance  by  its 
gi-anular  aspect,  and  the  presence  of  minute,  reddish  spheres,  readily  visible 
to  the  naked  eye,  and  named  Malpighian  corpuscles ;  while  the  medullary 
substance  appears  composed  of  radiating  fibres. 

Fig.  248. 


HORIZONTAL   LONGITUDINAL   SECTION   OF   THE   HORSE'S   KIDNEY. 

a,  Cortical  (or  vascular)  portion;  6,  Medullary  (or  tubular)  portioa;  c,  Periphei'al 
portion  of  the  latter;  d,  Interior  of  the  pelvis;  d',  d',  Arms  of  the  pelvis;  e 
Border  of  the  crest ;  /,  Infundibulum  ;  g,  Ureter. 

In  the  Horse,  the  tissue  of  the  kidney  cannot  be  divided  into  lobules  or 
pyramids  ;  to  the  naked  eye  it  appears  to  be  composed  of  fibres  that  start 
from  every  part  of  its  exterior,  and  converge  towards  the  crest  of  the  pelvis. 
A  microscopical  examination  demonstrates  these  fibres  to  be  canals  or  tubes ; 
hence  they  are  designated  tuhuli  uriniferi  or  Bellini's  tiibes.  A  delicate 
connective  tissue,  a  kind  of  stroma,  which  is  very  rare  in  the  cortical,  but 
more  abundant  in  the  medullary  substance,  especially  in  the  vicinity  of  the 
pelvis,  sustains  the  vessels  and  nerves,  and  unites  the  tnbuli  uriniferi  to  each 
other. 

The  tuhuli  uriniferi  are  constituted  by  a  proper  amorphous  membrane, 
very  thin  and  elastic,  whose  internal  face  is  lined  by  simple  epithelium  that 
readily  alters  ;  the  cells  are  polygonal  in  certain  points,  polyhedral  in  others, 
and  transparent  or  granular 


488 


TEE  URINARY  APPARATUS. 


The  uriniferous  tube  has  not  everywhere  the  same  direction  or  diameter 
Taking  it  at  its  termination  on  the  crest  of  the  pelvis,  and  following  it  to  its 


Fis.  249. 


SECTION  OF  THE  CORTICAL  SUBSTANCE  OF  THE  KIDNEY 
A,  A,  Tubuli  uriniferi  divided  transversely,  showing  the  spheroidal  epithelium  in 
their  interior ;  B,  Malpighian  capsule ;  a,  Its  afterent  branch  of  the  renal  artery ; 
b,  Its  glomerulus  of  capillaries;   c,  c,  Secreting  plexus  formed  by  its  efferent 
vessels ;  d,  d,  Fibrous  stroma. 

Fis.  250.  origin  in  the  Malpighian  body,  it 

is  found  that  the  tubule  is  at  first 
single,  straight,  and  voluminous, 
but  that  during  its  course  across 
the  medullary  substance  it  divides 
into  three  or  four  tubes,  which,  in 
their  turn,  subdivide  in  a  dicho- 
tomous  manner.  These  divisions 
are  less  voluminous  and  straight, 
and  their  diameter  is  uniform  until 
they  reach  the  cortical  substance; 
here  they  bifurcate,  each  branch 
becomes  flexuous,  and  is  designated 
the  uniting  tube,  and  is  continued 
in  a  kind  of  elongated  U  shape,  the 
ansiform  tube  of  Henle,  which  des- 
cends towards  the  centre  of  the 
kidney.  The  ascending  branch  of 
this  ansiform  tube,  whose  diameter 
is  very  small,  suddenly  dilates  on 
entering  the  cortical  substance, 
describes  several  bends,  contracts 
into  a  narrow  neck,  and  then  opens 
into  a  Malpighian  body,  after  having 
taken  the  name  of  convoluted  tube. 

The    corpora   Malpighiana    (or 
capsules)  are  minute  vesicles,  whose 

DIAGRAM  OF  THE  COURSE  OP  THE  URINIFEROUS  walls  posscss  the  samo  structuTc  as 
TUBULE.  t]ie  uriniferous  tubes  ;  each  lodges 

a,  Orifice  of  tubule  at  pelvic  crest;  6,  Recurrent   a  cluster  of  arterial  capillaries  or 
branches  which  form  loops,  c,  in  the  medullary  ,  alomervlm   and  has  two  onPO- 

portion  of  the  kidney,  and  terminate  in  the    'f**"*  giometuius,  ana  nas  IWO  oppo 

Malpighian  capsules  in  the  cortical  portion.       Site  openings :  one  communicating 


THE  KIDNEYS. 


489 


Fis.  251. 


between  the  corpora  and  convoluted  tubes,  the  other  affording  a  passage 
to  the  afferent  and  efferent  vessels  of  the  glomerule. 

3.  Vessels  and  Nerves. — a.  The  kiduey  pos- 
sesses a  special  artery  and  vein^  remarkable  for 
their  enormous  volume. 

The  artery  forms  several  branches  which  reach 
the  kidney  by  its  inner  border  and  inferior  face, 
and  divide  into  a  certain  number  of  principal 
vessels,  which  are  disposed  in  a  wavy  manner  on  the 
limits  of  the  cortical  and  medullary  substances. 
From  them  are  given  off  branches  to  each  of 
these  substances,  and  among  those  distributed  to 
the  cortical  are  some  regularly  disposed,  which 
furnish,  on  each  side,  the  glomerule  ramifications ; 
these  are  the  afferent  vessels  or  3Ialjpighian  glome- 
rules  (or  tufts)  ;  the  others  form  a  polyhedral 
plexus  around  the  convoluted  tubes  and  corj)ora 
Malpighiana.  The  affh-ent  vessels  of  the  renal 
glomerules  enter  this  plexus. 

The  arterial  branches  of  the  medullary  sub- 
stance descend  parallel  to  the  straight  tubes,  and 
anastomose  by  transverse  branches,  so  as  to  form 
a  network  with  elongated  meshes. 

The  vein  issues  from  the  kidney  by  the  hilus, 
and  succeeds  the  arterial  capillaries.  In  the  me- 
dullary substance,  there  are  straight  veins  as  there 
are  straight  arteries.  On  the  surface  of  the  organ, 
beneath  the  fibrous  envelope,  are  the  stars  of 
Verheyen :  the  junction  of  five  or  six  venules  which  converge  towards  a 
central  vein.    The  vcinletsof  the  _.     .,- 

.  rio".  25J. 

two  sxibstances  collect  into  more  "' 

voluminous  vessels,  which  form 
complete  arches  at  their  limits  ; 
it  is  to  the  presence  of  these 
vascular  canals,  that  the  dark 
colour  observed  at  this  point  of 
the  renal  tissue  must  be  attri- 
buted. 

b.  The  lymphatics  are  abund- 
ant at  the  superficies  and  in  the 
mass  of  the  organ,  forming  plex- 
uses, whose  ultimate  branches 
pass  to  the  sublumbar  glands. 

c.  The  nerves  emanate  from 
the  solar  plexus,  and  compose  a 
particular  network  arotmd  the 
arteries,  exhibiting,  on  their 
course,  some  microscopic  gan- 
glia. It  is  not  known  how  they 
terminate. 

Development. — The  kidneys  appear  very  early  in  the  foetus,  above  and  a 
little  behind  the  Wolffian  bodies.  They  are  then  very  distinctly  lobulated,  but 
the  lobes  gradually  become  fused,  and  have  entirely  disappeared  at  birth ;  the 


DISTRIBUTION  OF  THE  RENAL 
VESSELS  IN  THE  HORSE's 
KIDNEY. 

a,  Branch  of  renal  artery ;  af, 
Afferent  vessel ;  m,  m,  Mal- 
pighian  tufts ;  ef,  ef,  Ef- 
ferent vessels  ;  jj,  Vascular 
plexus  surrounding  the 
tubes ;  st,  Straight  tube  ; 
ct,  Convoluted  tube. 


TRANSVERSE   SECTION  OF   THE   KIDNEY. 

1,  Inferior  border ;  2.  Cortical  tissue  ;  3,  Section  of 
blood-vessels  ;  4,  Pelvis ;  5,  Ureter  ;  6,  Superior 
border ;  7,  Renal  artery ;  8,  Proper  capsule. 


490  THE  UBINARY  APPAliATUS. 

small  irregularities  on  tlie  surface  being  the  only  indications  of  their  having 
existed  in  Solipeds. 

Functions. — The  kidneys  are  the  organs  which  secrete  the  urine  ;  but 
this  secretion  does  not  take  place  to  the  same  extent  in  all  parts  of  then- 
tissue.  The  abundance  of  vessels  in  the  cortical  substance,  the  presence  of 
the  Malpighian  corpuscles,  and  the  flexuosities  described  by  the  uriniferous 
tubes,  sufficiently  indicate  that  this  substance  should  be  the  principal,  if  not 
the  exclusive,  seat  of  the  secretory  function.  But  in  what  manner  does  this 
secretion  take  place  ?  At  present  it  is  generally  agreed  that  the  urinary 
secretion  is  simply  an  infiltration  of  the  elements  of  the  urine  contained  in 
the  blood,  through  the  walls  of  the  vessels  and  the  uriniferous  tubes.  A 
knowledge  of  the  phenomenon  of  dialysis,  discovered  by  Graham  ;  and  the 
difference  existing  between  the  diameter  of  the  afferent  and  efferent  vessels  of 
the  Malpighian  glomerules — a  fact  whose  importance  was  pointed  out  by 
Ludwig — sufficiently  explains  this  filtration  of  the  urine  through  the  tissue 
of  the  kidneys. 

2.  The  Ureters.     (Fig.  247.) 

Form. — The  ureter  is  a  membranous  canal,  having  the  diameter  of  a  thick 
goose  quill,  wliich  conveys  the  urine  from  the  pelvis  of  the  kidney  into  the 
bladder.  Its  origin,  course,  termination,  and  structure,  will  be  successively 
considered. 

Origin. — It  has  been  already  shown  that  the  origin  of  the  ureter  is  at  the 
infundibulum  of  the  pelvis  ;  it  leaves  the  kidney  by  the  internal  fissure  or 
hilus,  curves  outwards,  passes  along  its  lower  face,  and  is  inflected  backwards 
in  quitting  the  organ. 

Direction. — The  course  it  afterwards  follows  is  almost  in  a  straight  line 
towards  the  pelvic  cavity,  along  with  the  aorta  or  posterior  vena  cava, 
according  to  the  side  to  which  it  belongs ;  it  is  in  contact  with  the  small 
psoas  muscles,  and  proceeds  above  the  peritoneum.  After  passing  beyond 
the  terminal  branches  of  the  aorta,  which  it  crosses  very  obliquely,  it 
becomes  enveloped  in  a  short  peritoneal  fold  that  maintains  it  against  the 
lateral  wall  of  the  pelvis ;  it  afterwards  emerges  from  this  fold,  and  reaches 
ohe  jiosterior  and  superior  part  of  the  bladder. 

Termination. — Having  reached  that  viscus,  its  termination  takes  place  as 
follows  :  instead  of  opening  directly  into  the  bladder  by  traversing  at  once, 
and  perpendicularly,  the  two  membranes  composing  the  organ,  the  ureter  at 
first  pierces  the  muscular  coat,  between  which  and  the  mucous  membrane 
it  passes  for  about  an  inch,  and  then  opens  on  the  surface  of  the  latter. 
This  arrangement  prevents  the  flowing  back  of  the  urine  into  the  ureter 
during  its  expulsion,  the  intermembranous  portion  of  that  canal  being 
strongly  compressed  by  the  external  pressure  then  exerted  by  the  muscular 
coat,  and  by  the  internal  resistance  which  the  accumulation  of  urine  in  the 
bladder  opposes  to  this  pressure.  So  well  ar^  Nature's  intentions  fulfilled 
in  this  respect,  that  we  may  inflate  the  bladder  by  the  ureter,  after  tying  the 
canal  of  the  urethra,  and  press  vigorously  on  the  distended  organ,  without 
being  able  to  make  a  single  bubble  of  air  pass  through  the  perfectly  pervious 
canal. 

Structube. — The  excretory  canal  of  the  kidney  is  composed  of  three  tunics: 

1.  An  internal  mucous  tunic,  continuous,  in  front,  with  that  lining  the 
pelvis  of  the  kidney,  and  behind,  with  that  of  the  bladder.  It  is  very  thin, 
pale,  ridged  longitudinally,  and  has  a  stratified  tesselated  epithelium.  (It 
has  some  mucous  follicles,  but  no  villi.) 


THE  BLADDER.  491 

2.  A  middle  muscular  layer  arranged  in  two  orders :  a  superficial,  whose 
fibres  are  circular,  and  a  deep,  passing  in  a  longitudinal  direction.  (Leyh 
and  other  authorities  describe  the  arrangement  of  the  muscular  planes, 
which  are  composed  of  smooth  fibres,  to  be  the  reverse  of  this,  the  longi- 
tudinal being  superficial,  and  the  deep  circular.) 

3.  An  external  tunic,  composed  of  connective  tissue  and  elastic  fibres. 
The  muscular  tissue  of  the  ureter,  by  contracting,  accelerates   the  flow 

of  the  urine. 

3.  The  Bladder.     (Fig.  247.) 

Position. — This  is  a  membranous  reservoir,  lodged  in  the  pelvic  cavity, 
where  it  occupies  more  or  less  space,  according  to  the  quantity  of  urine  it 
contains  ;  it  may  extend  beyond  the  pubis,  into  the  abdominal  cavity. 

Form. — Considered  in  a  moderate  state  of  plenitude,  the  bladder  is  ovoid 
in  figure  ;  its  large  extremity  being  turned  forward,  forms  a  rounded  cul-de- 
sac  (fundns),  at  the  bottom  of  which  is  remarked  a  kind  of  cicatrice,  caused 
by  the  obliteration  of  the  urachus.  The  other  extremity  terminates, 
posteriorly,  by  a  well-marked  constriction,  the  neck  of  the  bladder,  which 
gives  rise  to  the  urethi-al  canal . 

Weight. — The  average  weight  of  the  empty  bladder  is  about  sixteen 
ounces. 

Belations  and  mode  of  attachment. — The  bladder  responds:  above,  to 
the  vesiculaB  seminales,  to  the  pelvic  dilatations  of  the  deferent  ducts,  as 
well  as  to  the  rectum ;  below,  to  the  inferior  wall  of  the  pelvis,  on  which  it 
rests  (by  its  6ase)  ;  on  the  sides,  to  the  lateral  walls  of  that  cavity.  In  the 
female,  the  superior  face  of  the  bladder  is  in  relation  with  the  uterus  and 
vagina,  which  entirely  separate  it  from  the  rectum.  The  posterior  extremity 
or  necJc  (cervix),  flanked  on  each  side  by  the  lobes  of  the  jirostate,  is  fixed 
below  to  the  ischio-pubic  symphysis,  by  means  of  a  particular  ligament  or 
fasciculus  of  elastic  and  contractile  fibres,  which  are  detached  from  the 
muscular  layer,  and  expanded  over  the  lower  face  of  Wilson's  muscle,  to 
be  carried  backvA'ards  and  downwards,  and  terminate  on  the  surface  of 
the  internal  obturator  muscle.  The  anterior  extremity,  ov  fundus,  usually 
responds  to  the  pelvic  curvature  of  the  large  colon. 

It  is  remarked  that  this  extremity  is  covered  by  a  serous  cap,  which  is 
prolonged  backwards  on  its  body,  but  further  above  than  below.  This 
covering  is  continuous  with  the  parietal  layer  of  peritoneum,  and  adheres 
closely  to  the  muscular  tunic  of  the  bladder,  so  that  it  constitutes  its  chief 
attachment ;  its  disposition  is  precisely  similar,  in  principle,  to  that  of  the 
other  serous  visceral  membranes. 

Thus  the  peritoneum,  after  covering  the  walls  of  the  pelvis,  is  reflected 
on  the  organs  contained  in  that  cavity,  and  in  particular  on  the  bladder, 
around  which  it  forms  an  orbicular  fold.  This  again  gives  rise  to  three 
secondary  folds,  a  kind  of  serous  layers,  which  are  usually  termed  the 
ligaments  of  the  bladder.  One  of  these  layers  is  single  and  vertical,  and  is 
fixed  to  the  inferior  part  of  the  fundus ;  it  is  not  rare  to  see  it  prolonged 
forward  on  the  lower  wall  of  the  abdomen,  as  far  as  the  umbilicus  ;  on  its 
free  border  it  is  said  to  have  a  thin  hem  or  cord,  the  last  vestige  of  the 
urachus.  If  this  cord  exists,  which  appears  doubtful  to  us,  it  cannot  possess 
the  signification  given  to  it ;  for  the  urachus  has  not,  like  the  umbilical 
arteries,  an  abdominal  portion ;  it  only  commences  at  the  umbilicus  to  be 
prolonged  in  the  cord  to  the  allantois.  The  other  two  serous  layers 
(umbilical  ligaments),  pairs  and  horizontal,  are  attached  to  the  sides  of  the 


492 


THE  UBINARY  APPARATUS. 


fundus,  and  present,  on  their   free   border,   a  thick  cord,  the   obliterated 
umbilicaL  artery. 

Owing  to  this  disposition  of  the  peritoneum,  the  bladder  is  divided  into 
two  perfectly  distinct  regions :  an  anterior,  enveloped  by  a  serous  layer ; 
the  other,  posterior,  is  brought  in  contact  with  the  surrounding  organs 
through  the  medium  of  the  loose  and  abundant  cellular  tissue  of  the  pelvic 


Fig.  253. 


THE  KIDNEYS   AND   BLADDER  IN  THE   FCETUS  OP   SOLIPEDS. 

A,  Supra-renal  capsules ;  b,  Kidney ;  b,  Ureter ;  C,  Bladder ;  D,  Uraehus. — 1, 
Abdominal  aorta ;  2,  External  iliac  artery  ;  3,  Umbilical  artery ;  4,  Umbilical 
vein. 

region.  This  tissue,  constantly  mixed  with  adipose  masses  around  the  neck 
of  the  bladder,  submits,  with  the  serous  membrane  of  the  anterior  region,  to 
the  changes  in  form  and  continual  displacements  of  the  urinary  sac. 


THE  URETHRA.  493 

Interior. — This  pouch,  studied  internally,  exhibits  folds  and  ridges  moro 
or  less  marked,  according  to  its  state  of  i)lenituLle.  It  also  shows,  pos- 
teriorly, the  opening  of  the  neck,  which  communicates  with  the  urethral 
canal,  and  a  little  higher,  the  orifices  of  the  ureters.  These  three  apertures 
circumscribe  a  triangular  space,  the  trigonum  vesicae. 

Structure. — The  structure  of  the  bladder  is  very  simple.  Two  mem- 
branes compose  its  walls,  the  internal  of  which  is  mucous,  and  the  external 
muscular.  Anteriorly,  the  latter  is  covered  by  the  serous  investment 
described  above. 

The  mucous  memhrane  is  pale  and  thin,  and  is  continuous  with  that  lining 
the  ureters  and  the  urethra.  It  bhows  some  j)apilljB  and  some  simple 
tubular  glands  towards  the  neck.  Its  epithelium  is  stratified  and  tesselated, 
the  superficial  cells  being  very  irregular. 

The  muscular  layer  is  composed  of  white  fibres,  the  arrangement  of  which 
is  very  complicated.  Certain  authorities  describe  three  superposed  planes, 
whose  fibres  pass  in  different  directions.  In  the  Horse,  the  walls  of  whose 
bladder  are  very  thin,  these  planes  are  difficult  to  demonstrate.  The  fibres  are 
longitudinal,  cii'cular,  oblique,  spiral,  and  even  twisted  towards  the  fundus 
of  the  bladder  ;  the  deep  fibres  are  reticulated.  In  the  posterior  region  they 
do  not  form  a  sphincter  around  the  neck  of  the  organ,  as  is  generally 
believed ;  the  real  sphincter  is  Wilson's  muscle,  which  encircles  the 
membranous  portion  of  the  urethral  canal. 

Vessels  and  nerves. — The  parietes  of  the  bladder  receive  their  blood 
from  several  sources.  The  principal  arteries  come  from  the  "^esico-prostatic 
branch  of  the  internal  pudic  ;  the  iimbilical  artery  also  furnishes  ramifications 
that  reach  the  fundus  of  the  organ.  The  lympliatics  pass  to  the  sublumbar 
glands.  The  nerves  are  furnished  by  the  pelvic  or  hypogastric  plexus,  and 
the  inferior  branches  of  the  two  last  sacral  pairs ;  their  twigs  are  spread 
more  especially  between  the  muscular  and  mucous  layers. 

Develop3ient, — The  study  of  the  development  of  the  urinary  reservoir 
is  very  interesting.  It  is  narrower  and  more  elongated  in  the  foetus  than 
the  adult,  and  is  relatively  more  capacious  during  the  whole  period  of  intra- 
uterine life.  It  then  occupies  the  abdominal  cavity  as  far  as  the  lunbilical 
opening,  and  is  flanked  by  the  two  umbilical  arteries.  Its  posterior 
extremity  alone  enters  the  pelvis  ;  the  anterior  extremity,  forming  a  veritable 
neck,  is  continuous  with  the  urachiis,  just  as  the  neck,  properly  so  called,  is 
continuous  with  the  urethral  canal  (Fig.  253).  At  birth,  this  anterior  neck 
separates  from  the  urachus,  and  is  transformed  into  a  free  cul-de-sac  ;  while 
the  bladder  is  gradually  withdrawn  into  the  pelvic  cavity,  carrying  with  it 
the  mnbilical  arteries,  and  finishes  by  acquiring  the  position  it  definitively 
preserves  in  the  adult. 

Functions. — The  part  played  by  the  bladder  is  one  of  incontestible 
utility.  In  permitting  the  accumulation  of  the  urine  and  the  intermittent 
expulsion  of  that  excrementitial  fluid,  it  spares  animals  the  disagreeable 
condition  in  w^hich  they  would  be  placed  if  the  liquid  secreted  by  the 
kidneys  was  continually  being  discharged  as  it  was  produced. 


4.   Urethra. 

The  description  of  this  organ  will  be  given  with  that  of  the  genital 
organs  ;  as  in  the  male  it  is  common  to  the  urinary  and  generative  apparatus ; 
even  in  the  female  it  is  intimately  connected  with  the  latter 


494  THE  URINARY  APPARATUS. 

5.  The  Sup-a  renal  Capsules.     (Fig.  247.) 

Situation — Form. — The  supra-renal  capsules  (or  adrenals)  are  two  small 
bodies  applied  to  the  lower  face  of  the  kidneys,  in  front  of  the  hilus,  and 
close  to  their  inner  horder. 

They  are  elongated  from  before  to  behind,  flattened  on  both  sides,  and 
irregularly  lobulated  on  their  surface.  Their  length  is  from  2  to  21  inches, 
and  width  from  Ik  to  1^  inches.  They  have  not  the  same  volume,  the 
right  being  larger  than  the  left. 

Relations. — A  large  amount  of  connective  tissue,  vessels,  and  nervous 
filaments  attach  these  bodies  to  the  neighbouring  organs.  The  right  is 
related,  in  front,  to  the  liver ;  above,  to  the  right  kidney ;  and  inwardly,  to 
the  posterior  vena  cava  and  the  ramifications  of  the  solar  plexus.  The  left 
does  not  touch  the  liver  or  spleen,  but,  by  its  inner  border,  is  applied  against 
the  posterior  aorta  and  great  mesenteric  artery. 

Structure. — At  present,  anatomists  are  not  agreed  as  to  the  structure  of 
the  supra-renal  caj)sules.  The  following  is  what  is  probably  most  reliable 
in  this  difficult  point  in  normal  histology. 

These  organs  offer  an  enveloping  membrane  and  parenchyma. 

The  enveloping  membrane  is  fibrous,  and  sends  off,  from  its  inner  face, 
prolongations  which  pass  into  the  parenchyma  and  form  cylindrical  spaces, 
subdivided  by  transverse  lamellfe.  These  spaces  are  named  glandular 
cavities ;  but  the  septa  soon  become  thin,  and  disajipear  ahnost  completely, 
leaving  nothing  but  some  very  few  trabeculsB  of  connective  tissue. 

The  parenchyma  is  divisible  into  two  layers  :  the  cortical  and  medullary 
substance.  The  first  is  of  a  dark-brown  colour ;  the  second  is  yellow  and 
soft,  and  does  not  show  any  cavity  in  its  centre ;  that  which  has  been 
described  is  the  result  of  the  destruction  of  its  proper  elements,  which  soon 
change  after  death. 

The  glandular  cavities  of  the  cortical  substance  are  filled  with  nucleated, 
granular,  and  often  fat  cells  in  the  adult  animal ;  near  the  central  substance 
these  cavities  only  contain  a  single  cell. 

The  medullary  substance  has,  for  its  basis,  a  very  delicate  reticulum, 
supporting  cells  analogous  to  those  of  the  cortical  substance,  and  stellate 
elements  whicli  Luschka  considered  were  nerve  cells. 

Vessels  and  nerves. — Like  the  kidneys,  which  are  contiguous  to  them,  the 
supra-renal  capsules  receive  a  largo  quantity  of  blood,  compared  with  their 
small  volume.  The  arteries  are  branches  of  the  neighbouring  vessels :  the 
mesenteric  and  renal.  They  form  a  very  delicate  plexus  in  the  parenchyma. 
(They  keep  to  the  stroma  of  the  trabeculae ;  consequently,  their  finest 
ramifications  are  found  in  the  secondary  septa  of  the  cortical  substance, 
where  they  form  elongated  plexuses,  which  are  rounder  in  the  medullary 
portion.  In  the  middle  of  the  latter,  the  venous  ramuscules  unite,  and  give 
rise  to  a  considerable  trunk,  the  vena  supra  renalis,  on  which  the  organ  is 
placed  as  on  a  pedicle.  It  is  this  vein  which  constitutes  the  debated 
cavity.) 

The  veins  are  satellites  of  the  arteries  in  the  tissue  of  the  organ,  and  pass 
into  the  renal  vein  or  posterior  vena  cava.     The  lymphatics  are  scarce. 

The  supra-renal  bodies  receive  many  ganglionic  nerves  derived  from  the 
solar  plexus,  and  whose  mode  of  termination  is  unknown.  (As  mentioned 
by  Chauveau,  the  nerves  of  these  organs  are  extremely  numerous,  they  being 
more  abundantly  supplied  than  any  other  structure  of  the  kind  in  the  body ; 
a  large  number  of  small  branches  enter  the  cortical   portion,  to  become 


THE  URINARY  APPARATUS.  495 

developed  in  the  medullary  tissue.  As  these  nerves  do  net  leave  the  medullary 
substance,  and  as,  besides,  its  cellular  elements  ai)pear  to  be  of  the  same 
nature  as  the  multipolar  ganglionic  cells,  it  is  presumed  that  the  nervous 
fibres  emerge  from  these  globules,  and  that  the  medulla  acts  as  a  ganglionic 
nervous  centre.  Though  Leydig  fully  believed  the  internal  portion  to  be 
of  a  nervous  character,  he  thought  another  function  might  be  attributed  to 
the  cortical,  in  consequence  of  its  bciug  most  frequently  of  a  fatty  nature. 
Berf^mann  was  the  first,  in  1839,  to  class  these  organs  with  the  nervous 
system,  and  Eemak,  in  1847,  by  his  researches  in  embryology,  was  led  to 
group  them  with  the  sympathetic  ganglia,  and  named  them  nervous  glands. 
Injury  to  the  dorsal  portion  of  the  spinal  cord  causes  congestion  and 
hypertrojihy  of  the  supra-renal  capsules.  In  a  watery  solution  of  the 
cortical  portion,  a  rose-tinted  substance  has  been  discovered,  which  changes 
to  green  with  per  salts  of  iron.) 

Development. — These  bodies  are  relatively  larger  in  the  foetus  than  the 
adult,  though  this  difierence  does  not  influence  their  structure. 

Functions. — Their  uses  are  still  unkno'mi ;  they  are  ranked  in  the 
category  of  blood-vascular  glands,  along  with  the  spleen  and  thyroid  body, 
whose  functions  are  also  not  yet  ascertained.  (Leydig  is  of  opinion  that 
these  bodies  should  be  regarded  as  belonging  to  the  nervous  system.) 

niFFERENTlAL   CHAKACTERS   IN   THE    rEINARY   ATPARATCS   OF    OTHER   THAN   SOLIPED 

AMIIALS 

1.  Kidney?.— In  other  than  Soliped  animals,  the  renal  glands  are  simple  or  multiple, 
or  in  other  words,  simple  or  lobulated.  In  the  Ox.  the  kidneys  huve  an  elongated  shape 
from  before  to  behind,  which  is  altogether  characteristic;  and.  in  addition,  they 
preserve  during  life  the  lobulated  form  only  seen  in  the  other  animals  durmg  intra- 
uterine existence.  Each  agglomeration  is  composed  of  from  fifteen  to  twenty  secondary 
kidnevs;  but  the  pelvis  is  not  formed  in  the  centre  of  this  aggh  raeration,  being  earned 
altoiie"ther  outwards,  and  occupving  an  excavation  in  the  inferior  face  of  the  organ,  which 
represents  the  hilus.  This  cavitv  is  divided  into  as  many  short,  wide  prolongations— the 
cuUces,  as  there  are  principal  "lobules ;  the  uriniferous  tubes  from  each  lobule  open 
on  a  small  papilla,  which  projects  into  the  bottom  of  the  calyx.  This  papilla  is.  theretoie, 
nothing  more  than  tlie  crest  of  the  simple  pelvis  in  the  kidney  of  Solipeds  (Fig.  256j. 

In  the  Sheep,  the  kidneys  are  not  lobulated,  and  the  pelvis  is  carried  to  the  inner 
border,  as  in  the  Horse. 

The  kidneys  of  the  Pig  are  simple  and  voluminous,  ard  their  pelvis  is  disposed  as  in 
the  Horse.     (There  are  10  or  12  papillfe,  and  as  many  calices.) 

In  the  Dog  and  Cat,  there  are  no  calices  absolutely  compnrable  with  those  of 
Kuminants.  The  pelvis  is  simple,  and  presents  at  the  bottom  a  single,  large,  elongated 
tubercle,  that  has  at  its  base  some  very  short  projections  or  pilLirs. 

2.  Bladder.— The  most  important  difference  in  the  bladder  of  the  domesticated 
animals  consists  in  the  extent  of  the  development  of  its  peritoneal  envelope.  In  non- 
soliped  animals  this  covers  all  the  organ  to  the  neck ;  the  ligaments  are  also  veiy  short, 
and  the  viscus  may  be  easily  projected  into  the  abdominal  cavity.  The  bladder  is  thin, 
and  of  a  considerable  capacity  in  Ruminants  and  the  Fig  :  in  the  Dog,  on  the  contrary, 
it  has  a  very-  thick  muscular"  laver,  its  fibres  forming  distinct  tasciculi.  especially  when 
in  a  state  of  "retraction.  (In  Euininants,  the  orifices  of  the  ureters  are  near  each  other  ; 
at  the  fundus  the  mucous  membrane  shows  a  small  fossa  which  is  continued  by  a  narrow 
canal  that  terminates  in  a  cul-de  sac,  and  constitutes  a  free  appendix  about  half  an  inch 
long,  and  of  the  thickness  of  a  goose-quill.) 

3.  Supra-renal  capsules. — These  small  organs  are  discoid  in  the  Sheep  and  Pig, 
reniform  in  the  Dog.  In  the  Ox.  they  are  situated  at  a  certain  distance  in  front  of  the 
kidneys,  and  their  shape  is  like  that  of  these  bodies  in  the  Horse;  though  they  are  a  little 
constricted  in  the  middle,  and  slightly  curved. 

In  Birds,  the  kidneys  "are  lodged  at  the  same  height,  behind  the  peritoneum, 
immediately  posterior  to  the  lungs,  and  in  the  lumbar  and  pelvic  regions,  where  they 
occupy  several  fossje  excavate  1  in  the  upper  face  of  the  pelvis.  Their  form  is  irregular 
and  more  or  less  elongated,  depending  upon  the  bones  and  other  parts  to  which  they  are 


496 


THE  URINARY  APPARATUS. 


applied,  and  on  which  they  are  moulded.  In  many  birds,  nevertheless,  three  portions, 
more  or  less  separated  by  fissures,  may  be  recognised.  The  ilco-lumbar  portion  (so  named 
because  of  its  constant  position  in  this  region)  is  the  most  advanced ;  it  is  often  the 
largest.  The  middle  is  the  narrowest ;  it  is  turned  towards  the  ileo-sacral  region,  to  enter 
the^pelvis.  The  posterior  is  contained  in  that  cavity,  and  is  again  larger.  These  two 
latter  portions  are  designated  as  the  anterior  or  superior  pelvic,  and  the  inferior  or  deep 
pelvic  portions.    Their  internal  and  superior  border  is  often  notched  by  a  series  of  trans- 


Fis.  254. 


Fis.  255. 


Fig.  256. 


KIDNEYS   OF    TlIK   OX. 

Fig.  254. — Right  kidney,  viewed  on  its  upper  and  external  face.  Fig.  255. — Left 
kidney,  from  its  internal  and  inferior  face;  a,  Pelvis;  b,  b,  b,  Branches  of  tlie 
pelvis  terminating  in  calices ;  c.  Ureter ;  d,  Renal  artery.  Fig.  256. — The  calices 
in  the  left  kidney.  The  contents  of  the  hilus,  including  the  branches  of  the 
pelvis,  have  been  removed  to  show  the  tubercles  at  the  bottom  of  these  calices. 
Only  seven  are  visible,  the  othei's  being  beneath  the  borders  of  the  renal  fissure. 

verse  fissures  produced  by  the  protrusion  of  the  transverse  processes  of  the  sacral  verte- 
brte,  as  the  lungs  are  furrowed  by  the  projection  of  the  ribs."' 

The  excretory  apparatus  is  incomplete,  and  is  only  formed  by  the  ureters,  which  open 
into  the  cloaca,  where  the  urine  is  mixed  with  the  faices.  Only  one  bird,  the  Ostrich, 
possesses  a  bladder,  which  is  disposed  in  a  particular  manner. 


OOMPAEISON   OF    THE   URINARY    APPARATUS   OF   MAN   WITH   THAT   OP   ANIMALS. 

1.  Kidneys. — The  two  kidneys  of  Man  have,  like  those  of  the  smaller  domesticated 
animals,  the  same  shape — that  of  a  haricot  bean.  The  average  weight  is  about  from  three 
to  five  ounces.  Contrary  to  what  is  observed  in  the  Horse,  the  left  kidney  is  more 
voluminous  than  the  right,  and  is  higher. 

The  kidneys  are  simple  externally,  though  their  tissue  is  disposed  in  distinct  lobes, 
which  number  from  eight  to  fifteen,  and  are  composed  of  a  Malpighian  pyramid  and  a 


Cuvier,  '■Anatomie  Compar^e,'  2nd  edition.    Paris,  1836-46. 


THE  URINARY  APPARATUS.  497 

superposed  pyramid  of  Ferrein;  they  terminate,  towards  the  hilus,  by  a  cone  or  renul 
papilla,  each  surrounded  by  a  calyx,  and  are  separated  by  small  prolongations  of  the 
cortical  substance — the  columnae  Bertini. 

2.  Ureters. — The  canals  are  disposed  at  their  origin  as  in  the  Ox ;  they  terminate  as 
in  the  other  animals.  In  the  hilus  of  the  kidney  are  from  eight  to  fifteen  prolongations  or 
calices,  which  unite  into  a  larger  cavity  or  great  calyx,  that  finally  opens  into  the  renal 
pelvis ;  this  is  immediately  followed  by  the  ureter. 

3.  Bladder. — The  large  extremity  of  this  organ  is  directed  downwards  in  the  bottom  of 
the  pelvis,  where  it  is  continuous  with  the  urethral  canal ;  its  summit  is  directed  upwards, 
and  is  frequently  pointed.  Its  mode  of  attachment  and  internal  conformation  are  the 
same  as  in  animals;  and,  as  in  the  Horse,  the  peritoneum  envelops  it  very  incompletely. 
The  muscular  fibres  are  arranged  into  three  planes :  a  superficial,  which  forms  a  baud 
that  is  carried  from  the  anterior  to  the  posterior  face  in  passing  over  the  summit ;  a 
middle  plane  whose  fibres  are  circular ;  and  a  deep  plane  with  reticulated  fibres. 

Supra-renal  capsules. — This  name  is  quite  appropriate  to  these  bodies,  as  in  Man,  or 
at  least  in  the  foetus,  they  form  a  kind  of  helmet  that  covers  the  upper  part  of  the 
kidney. 

There  is  nothing  to  add  respecting  their  structure. 


BOOK  V. 

ClECULATORY  ApPAEATUS. 

The  animal  economy  is  incessantly  traversed  by  two  fluids — blood  and 
hp^iph. 

The  blood  is  a  liquid,  coloured  bright-red  or  brown  by  particular  globules, 
from  which  the  tissues  derive  not  only  the  materials  for  nutrition  and 
secretion,  but  also  the  exciting  principle  which  vivifies  the  organic 
matter.  It  is  named  red  or  dark-coloured  blood,  according  to  its 
tint. 

The  lymph  or  ichite  blood  is  a  transparent,  citrine-coloured  fluid,  which 
can  be  obtained  from  the  majority  of  the  organs.  That  which  comes  from 
the  abdominal  portion  of  the  alimentary  canal  is  charged,  during  digestion, 
with  a  portion  of  the  reparative  materials  elaborated  in  that  apparatus,  and 
is  distinguished  by  its  lactescent  aspect ;  it  is  designated  the  chyle. 

Fig.  257. 


THEORETICAL   PLAN   OF   THE   CIRCULATORY   SYSTEM. 

(h,  D,  C,  E,  The  canal  for  red  blood ;  E,  B,  A,  G,  Canal  for  black  blood.  The  arrows 
indicate  the  course  of  the  blood.  The  two  canals  are  represented  in  their  middle 
portion,  ab,  CD,  as  isolated ;  but  in  nature  they  are  enveloped  at  this  point  in  a 
common  sac  that  concurs  to  form  the  heart.) 

These  fluids  are  carried  by  vessels — tubes  which  are  continuous  with  one 
another.  When  joined  together,  end  to  end,  these  tubes  give  rise  to  three 
principal  canals : 

"  One  of  these  canals  extends  from  the  lungs  to  all  parts  of  the  body, 
and  is  traversed  by  red  blood. 


TEE  HEART.  499 

'•  The  second  extends  from  all  parts  of  the  body  to  the  lungs,  and  carries 
dark  blood. 

"  The  third  passes  from  the  majority  of  the  organs  towards  the  canal 
carrying  dark  blood,  in  which  it  terminates ;  it  conveys  the  white  blood  or 
lymph. 

"  The  red-blood  and  dark-blood  canals  bear  the  greatest  analogy  to  each 
other.  Both  are  simple  in  their  middle  portion,  which  alternately  dilates 
and  contracts  to  impress  upon  the  blood  the  movement  necessary  to  life. 
Both  present  at  their  extremities  innumerable  ramifications,  which  ultimately 
join  each  other ;  so  that  the  fluid  they  carry  passes  from  one  to  the  other 
in  a  constant  and  circular  direction.  Both  are  composed,  at  their  origin, 
of  vessels  in  which  the  blood  moves  in  confluent  columns :  these  are  the 
veins ;  and  in  their  terminal  part,  of  vessels  in  which  the  same  liquid  is 
spread  in  divergent  columns :  these  are  the  arteries. 

"  The  canal  for  white  blood  is  composed  of  a  single  order  of  vessels,  the 
lymphatics  :  converging  tubes,  whose  common  trunk  opens  into  the  circulatory 
canal  that  results  from  the  abouchement  of  the  red  and  dark  blood  canals  ; 
the  relation  it  afiects  with  these  latter  is  that  of  a  tangent  with  its  cir- 
cumference."— Sappey. 

These  three  canals  constitute  the  circulatory  apparatus. 

This  apparatus  therefore  comprises :  1,  The  heart,  a  central  organ, 
charged  to  propel  the  blood  ;  2,  A  system  of  centrifugal  vessels,  the  arteries, 
which  carry  the  blood  from  the  heart  into  the  different  organs;  3,  A 
system  of  centripetal  vessels,  the  veins,  which  bring  the  nutritive  fluid  to 
the  heart ;  4.  The  lymphatics,  an  accessory  centripetal  system,  destined  to 
convey  the  lymph  into  the  blood-vascular  circle. 

In  many  anatomical  works,  the  study  of  this  apparatus — the  heart, 
arteries,  veins,  and  lymphatics,  is  designated  "  angiology." 


FIRST  SECTION. 
The  Heart. 


The  history  of  the  heart  comprises:  1,  A  general  view  of  the  organ; 
2,  The  study  of  .its  external  conformation  ;  3,  Its  interior  ;  4,  Its  structure  ; 
5.  A  description  of  the  pericardium,  the  serous  cavity  containing  it ;  6,  A 
glance  at  its  physiology. 

1.  The  Heart  as  a  Whole.  (Figs.  230,  234,  258,  259.) 
General  sJcetch. — The  heart,  the  central  portion  of  the  circulatory 
apparatus,  is  a  hollow  muscle,  whose  cavity  is  divided  by  a  thick  vertical 
septum  into  two  perfectly  independent  pouches.  Of  these  two  contractile 
pouches,  one  placed  on  the  track  of  the  dark  blood,  propels  it  into  the  lungs  ; 
the  other,  situated  on  the  course  of  the  red  blood,  distributes  it  to  all  parts 
of  the  body. 

Each  of  these  is  subdivided  into  two  superposed  compartments  by  a 
circular  constriction,  at  which  is  a  membranous  valve  that  at  certain  fixed 
periods  is  elevated,  and  then  forms  a  complete  horizontal  partition  extended 
between  the  two  compartments. 

The  superior  compartment  receives  the  convergent  or  centripetal  portion 


500  THE  CIRCULATORY  APPARATUS. 

of  the  blood  canal — that  is  the  veins  :  it  is  named  the  auricle.  The  inferior 
gives  origin  to  the  divergent  or  centrifugal  part  of  the  same  canal,  and  is 
designated  the  ventricle. 

The  cavities  of  the  heart  are  distinguished  into  right  or  anterim-,  and 
left  or  posterior,  because  of  their  relative  positions.  There  are,  then  :  a 
rigid  auricle  and  ventricle,  the  two  dark-blood  pouches  ;  and  a  left  auricle 
and  ventricle,  situated  on  the  track  of  the  red-blood  canal. 

Situation. — The  heart,  enclosed  as  it  is  in  a  fibro-serous  sac,  named  the 
pericardium,  is  placed  in  the  chest  between  the  two  layers  of  the  mediastinum, 
opposite  the  third,  fourth,  fifth,  and  sixth  ribs ;  in  front  of  the  diaphragm, 
which  separates  it  from  the  abdominal  viscera ;  above  the  sternum,  which 
appears  to  support  it ;  and  beneath  the  vertebral  column,  to  which  it  is 
suspended  by  means  of  the  large  vessels.  (Between  the  middle  of  the 
anterior  border  of  the  heart,  in  front,  and  the  entrance  to  the  chest,  is  an 
interval  of  about  four  inches  ;  and  behind,  at  the  same  level,  this  organ  is 
at  a  similar  distance  from  the  diaphragm.  It  is  distant  from  the  fifth  and 
sixth  dorsal  vertebrae,  from  which  it  is  suspended,  about  4i  to  5  inches 
in  an  average -sized  Horse.) 

Forra  and  direction. — The  heart  presents  the  form  of  an  inverted  cone, 
slightly  depressed  on  each  side,  and  whose  axis,  directed  obliquely 
downwards  and  backwards,  deviates  a  little  to  the  right  at  its  superior 
extremity. 

Volume. — In  a  middle-sized  Horse,  the  greater  axis  of  the  heart  is  about 
lOi  inches  in  length  ;  its  antero-posterior  diameter,  measured  near  the  base, 
is  equivalent  to  about  7^  inches.  Its  lateral  diameter  does  not  exceed 
from  5  to  5^  inches. 

Capacity. — It  is  very  difficult,  if  not  impossible,  to  obtain  the  exact 
cajjacity  of  the  heart's  cavities.  From  reasoning,  one  is  led  to  think  that 
the  two  hearts  have  exactly  the  same  capacity,  and  that  this  capacity  is 
equivalent  to  an  average  of  1  to  1\  pints.  The  amount  obtained  by 
measurement  is  much  more  considerable ;  but  then  the  heart  is  distended 
to  a  greater  degree  than  in  its  physiological  state. 

Weight. — The  weight  of  the  heart  varies  with  the  size  of  animals,  and 
that  to  a  considerable  degree.  Its  average  is  about  6f  pounds.  (The  volume 
and  weight  of  the  heart  are  very  much  greater  in  well-bred  than  in  under- 
bred Horses.  Its  dimensions  and  capacity  are  greater  in  the  living  than 
the  dead  animal ;  as,  after  death,  its  cavities  contract,  j^articularly  the  aortic 
ventricle,  whose  walls  are  the  thickest.  This  ventricle  will  then  scarcely 
contain  more  than  3-4ths  to  lith  gills ;  the  pulmonary  ventricle,  which 
is  not  so  thick,  and  consequently  less  contracted,  may  usually  receive  double 
that  quantity ;  while  in  animals  experimented  on  when  expiring,  it  was 
observed  that  these  two  ventricles  were  much  more  capacious,  and  that  each 
contained  at  least  from  1:|^  to  1^  pints.) 

External  Conformation  of  the  Heart.    (Figs.  258,  259.) 

The  cone  represented  by  the  heart  is  divided  by  a  horizontal  groove  into 
two  unequal  portions :  the  one  superior,  comprising  the  auricles  or  auricular 
mass  ;  the  other  inferior  or  principal,  formed  by  the  ventricles  or  ventricular 
mass. 

A.  Ventricular  Mass. — It  is  this  which  determines  the  conical  shape 
of  the  heart,  and  constitues  its  largest  portion.  Owing  to  the  slight  flatten- 
ing which  depresses  the  organ  in  a  lateral  sense,  it  may  be  considered  as 


THE  HEART. 


501 


having  a  right  and  left  face,  an  anterior  and  posterior  border,  an  apex,  and  a 
base. 

The  right  face,  smooth  and  rounded,  is  traversed  by  a  vascular  furrow 
parallel  to  the  axis  of  the  heart,  aud  which  divides  this  face  into  two 
sections :  an  anterior,  belonging  to  the  right  ventricle ;  and  a  posterior,  less 
extensive,  forming  part  of  the  left  ventricle  (Fig.  259). 

The  left  face,  disposed  in  the  same  manner,  also  shows  a  groove  on  the 
limit  of  the   two   ventricles,  whose   direction    slightly  crosses   the    great 


Ficr.  258. 


THE   HEART   AND   PRINCIPAL   VESSELS;   LEFT   FACE. 

a.  Right  ventricle ;  6,  Left  ventricle ;  c,  Right  auricle ;  d,  Left  auricle ;  e,  Pul- 
monary artery  ;  e',  Obliterated  arterial  canal ;  /,  Pulmonary  veins  ;  g.  Anterior 
aorta;  h,  Left  axillary  artery;  i,  Right  axillary  artery,  or  brachio-cephalic 
trunk;  j.  Origin  of  the  dorsal  artery;  k,  Origin  of  the  superior  cervical  artery; 
I,  Origin  of  the  vertebral  artery  ;  m,  Origin  of  the  inferior  cervical  arteiy ;  n. 
Origin  of  the  internal  thoracic  artery;  o.  Origin  of  the  external  ditto;  p,  Carotid 
arteries;  q,  Posterior  aorta;  r.  Anterior  vena  cava;  s,  Trunk  of  the  axillary 
vein;  t,  Trunk  of  the  internal  thoracic  vein;  u.  Trunk  of  the  dorso-cervical 
vein;  v,  Posterior  vena  cava;  v',  Embouchure  of  the  hepatic  and  diaphragmatic 
veins ;  x,  Vena  azygos ;  y,  Thoracic  duct ;  z,  Embouchure  of  that  vessel,  placed 
near  the  origin  of  the  anterior  vena  cava. — 1,  Right  cardiac  artery  ;  2,  Left 
cardiac  artery ;  3,  Auriculo-ventricular  branch  of  the  latter ;  4,  Its  ventricular 
branch  ;  5,  Cardiac  vein. 

diameter  of  the  heart  from  behind  to  before,  and  above  to  below,  and  which 
is  much  nearer  the  anterior  than  the  posterior  border  (Fig.  258). 
35 


502 


THE  CIBCJLATORY  APPARATUS. 


These  two  faces  respond,  thi-ough  tlie  medium  of  the  pericardium,  to  the 
plurfe  and  the  pulmonary  lobes  ;  the  latter  separate  them  from  the  thorax,  ex- 
cept towards  the  middle  and  apex  of  the  organ,  where  these  faces  come  directly 
in  contact  with  the  thoracic  parietes  through  the  notch  at  the  inferior  border 
of  the  lung,  and  which  we  know  is  more  marked  in  the  left  than  the  right. 
The  borders  are  thick,  smooth,  and  rounded.     The  anterior,  formed  by 

the  risht   ventricle,  is    very 
'''  oblique  from  above  to  below, 

and  befoi'e  to  behind  ;  it  then 
inclines  on  the  sternum  more 
or  less,  according  to  the  sub- 
jects. 

Tlhe posterior  border,  much 
shorter  than  the  anterior,  is 
nearly  vertical.  Superiorly, 
it  is  sejiaratcd  from  the  dia- 
phragm by  the  lung ;  but, 
below,  it  is  quite  close  to 
that  muscular  septum. 

The  apex,  or  point  of  the 
ventricular  cone,  is  blunt, 
slightly  rounded,  turned  to 
the  left,  and  formed  entirely 
by  the  left  ventricle. 

The  base  responds  on  the 
right,  in  front,  and  behind, 
to  the  auricular  mass  ;  it  gives 
exit  on  the  left,  and  a  little 
in  front,  to  the  two  arterial 
aortic  and  pulmonary  trunks. 
B.  Auricular  Mass. — 
Elongated  from  before  to  be- 
hind, disposed  like  a  crescent 
above  the  right  side  of  the 
base  of  the  ventricles,  con- 
stricted in  its  middle  part, 
on  the  limit  of  the  two  auri- 
cles, the  auricular  mass  pre- 
sents for  study  three  faces, 
two  extremities,  and  a  base. 

TliO  superior  face  is  di- 
vided by  a  middle  constric- 
tion into  two  convex  sections, 
horizontal  or  auriculo-ventricular  branch ;  o,  Ven-  each  of  which  corresponds  to 
tricular  branch  of  the  cardiac  vein;  p,  Auriculo-  an  auricle.  The  anterior,  or 
ventricular  branch  of  the  same.  •    i  i  i-  i  xi        • 

right  section,  shows  the  in- 
sertion of  the  anterior  vena  cava  and  vena  azygos ;  the  posterior,  or  left, 
that  of  the  pulmonary  veins.  The  trachea,  bronchi,  and  pulmonary  artery 
pass  above  this  face  (Figs.  258,  259). 

The  rigM  face,  the  most  extensive  in  the  antero-posterior  direction,  is 
divided  like  the  preceding,  and  disposed  in  a  similar  manner.  The  right,  or 
anterior  part,  receives,  behind  and  below,  the  insertion  of  the  posterior  vena 
cava,  and  the  coronary  and  bronchial  veins  (Fig.  259). 


THE   HEART   AND   I'UINCU'AL    VESSELS;   RIGHT   FACE. 

2,  Right  ventricle ;  6,  Left  ventricle ;  c,  Right  auricle ; 
d,  Anterior  vena  cava ;  e,  Vena  azygos ;  /,  Posterior 
vena  cava ;  g,  g,  Pulmonary  veins ;  h,  h,  Divisions 
of  the  pulmonary  artery  ;  i,  Posterior  aorta ;  j,  An- 
terior aorta ;  k,  Thoracic  duct ;  /,  Right  cardiac 
artery ;  m,  Its  vertical  or   ventricular  branch ;  n.  Its 


THE  HEART.  503 

The  left  face,  concave  from  before  to  behind,  includes  the  arterial  trunks 
which  leave  the  base  of  the  heart. 

Each  of  the  extremities,  anterior  and  posterior,  constitutes  a  detached 
portion,  named  the  appendix  auricidaris ;  these  appendages  are  curved 
towards  each  other  in  being  flattened  from  above  to  below.  Their  convex 
border  is  more  or  less  crenelated,  like  the  margin  of  a  cock's  comb,  and  their 
culminating  portion  advances  nearly  to  the  pulmonary  artery,  above  the 
trunk  of  the  cardiac  vessels  (Fig.  258). 

The  base  of  the  auricular  mass,  opposed  to  the  base  of  the  ventricles, 
is  separated  from  it  at  its  periphery  by  the  horizontal  groove  of  the  heart. 

3.  Internal  Conformation  of  the  Heart. 

Preparation. — It  suffices  to  make  a  longitudinal  incision  before  and  behind  the  orpjan, 
in  order  to  expose  its  cavities.  (I  have  followed  Wilson's  directions  for  many  years  when 
examining  the  interior  of  the  heart,  and  as  a  careful  inspection  of  it  is  often  necess.iry  in 
the  course  of  an  autopsy,  I  think  tlie  student  should  practise  the  best  method  of  laying 
open  these  cavities.  Tiie  riirht  auricle  is  prepared  by  making  a  transverse  incision  along 
its  ventricular  margin,  from  the  appendix  to  its  right  border,  and  crossed  by  a  perpendi- 
cular incision,  carried  from  the  side  of  the  anterior  to  the  posterior  cava.  The  right 
ventricle  is  laid  open  by  making  an  incision  parallel  with,  and  a  little  to  the  right  of,  the 
middle  line,  from  the  pulmonary  artery  in  front,  to  the  apex  of  the  heart,  and  thence  by 
the  side  of  the  middle  line  behind  to  the  auriculo-ventricular  opening.  The  interior  of 
the  left  auricle  is  exposed  by  a  J_-shaped  incition,  the  horizontal  section  being  made 
along  the  border  which  is  attached  to  the  base  of  the  ventricle.  The  latter  is  opened  by 
making  an  incision  a  little  to  the  left  of  the  septum  ventriculorum,  and  continuing  it 
around  the  apex  of  the  heart  to  the  auriculo-veutricular  opening  behind.) 

If  the  heart,  when  viewed  externally,  appears  to  be  a  single  organ,  it  is 
not  so  when  examined  internally.  The  vertical  septum  which  divides  it 
into  two  bilocular  pouches,  in  reality  makes  two  hearts  of  it — one  for  the 
dark,  the  other  for  the  red  blood.  We  will  successively  study  these  two 
cavites  by  commencing  with  the  jiartition  that  separates  them. 

A.  Cardiac  Septum. — The  superior  part  of  this  septum,  placed  between 
the  two  auricles,  is  named  the  interauricidar  partition  {septum  auricularum). 
The  inferior  jiortion  constitutes  the  interventricular  partition  [septum  ven- 
triculorum).  The  first,  thin  and  not  extensive,  is  perforated  in  the  foetus  by 
iim  foramen  of  Botal  [foramen  ovale).  The  second,  thick  in  its  centre,  thins 
a  little  towards  its  borders. 

B.  Dark-blood  (or  Pulmonary)  Heart. — The  two  superposed  cavities 
forming  this  pouch  are  situated  in  front  and  to  the  right.  They  are  indif- 
ferently named  the  anterior  or  rigid  cavities  of  the  heart :  the  latter  term 
being  in  most  general  use,  though  the  first  is  much  more  convenient  in 
Veterinary  Anatomy. 

Eight  Ventricle. — The  right  ventricle  represents  a  hollow  cone,  the 
horizontal  section  of  which  resembles  a  crescent,  its  posterior  plane  being 
pushed  into  the  cavity  by  the  left  ventricle. 

It  offers  two  walls,  an  apex,  and  a  base. 

Walls. — The  anterior  icall  is  concave  ;  its  thickness  is  more  considerable 
above  than  below,  and  averages  6-lOths  of  an  inch.  The  posterior  icall  is 
convex,  and  formed  by  the  septum  ventriculorum. 

Both  walls  are  uneven,  from  the  presence  of  fleshy  columns  (columnse 
carneae),  which  we  will  commence  examining  in  a  general  manner,  as  they  are 
found  in  the  four  compartments  of  the  heart.  They  are  of  three  kinds : 
one  kind,  named  the  pillars  of  the  heart  {columnx  or  musculi  papillares),  thick 
and  short,  and  fixed  by  their  base  to  the  walls  of  the  ventricles,  have  a  free 


504 


THE  CIRCULATORY  APPARATUS. 


¥iz.  260. 


summit,  into  which  are  implanted  the  tendinous  cords  [cliordce.  tendince) 
proceeding  from  the  auriculo-ventricular  valve ;  those  of  the  second  order 
are  free  in  their  middle  part,  and  attached  by  their  extremities  to  the  walls 
of  the  heart ;  while  the  third  description  adhere  throughout  their  length  to 
the  cardiac  tissue,  on  which  they  stand  as  if  sculptured  in  relief. 

In  the  right  ventricle,  two  columns  of  the  first  order,  rarely  three,  are 

met  with  :  one  on  the  anterior  wall, 
the  other  on  the  posterior.  The 
columns  of  the  second  order  num- 
ber two  or  three  principal  ones,  ex- 
tending from  one  wall  to  the  other, 
or  attached  to  two  different  points 
of  the  same  wall.  There  also  ex- 
ist a  considerable  number  of  small 
ones  intermixed  with  those  of  the 
third  order.  The  latter  are  par- 
ticularly abundant  in  the  angles 
formed  by  the  union  of  the  two 
faces,  where  they  interlace  and  give 
rise  to  more  or  less  complicated 
areolag. 

Apex. — The  apex  of  the  right 
ventricle  does  not  descend  to  the 
point  of  the  heart,  being  distant 
from  it  about  1^  inches. 

Base. — This  is  pierced  by  two 
large  orifices — the  auriculo-ven- 
tricular opening  and  the  pulmonary 
opening. 

Auriculo-ventricular  opening. — 
Placed  on  a  level  with  the  con- 
striction which  divides  the  right 
heart  into  two  superposed  compart- 
ments, this  orifice,  widely  open  and 
almost  a  regular  circle,  forms  tlie 
communication  between  the  auricle 
and  ventricle.  It  is  provided  with 
a  valvular  fold  that  exactly  closes 
the  orifice  when  the  ventricle  con- 
tracts to  propel  the  blood  into  the 
lungs,  and  which  is  termed  the 
tricuspid  (having  three  points)  valve, 
in  consequence  of  its  form.  This  valve  offers  :  1,  A  superior  border,  attached 
to  the  entire  margin  of  the  auriculo-ventricular  opening ;  2,  An  inferior 
opening,  free,  cut  into  three  festoons  by  three  deep  notches,  and  fixed  to 
the  ventricular  walls,  principally  on  the  summits  of  the  fleshy  columns,  by 
means  of  tendinous  cords  which  ramify  on  reaching  the  valve.  One  of  these 
festoons,  more  developed  than  the  others,  is  placed  on  the  limit  of  the 
auriculo-ventricular  and  pulmonary  openings ;  thereby  constituting  a  kind  of 
vertical  partition  which  divides  the  ventricular  cavity  at  its  base  into  two 
compartments  :  a  right  cr  auricular,  and  a  left  or  arterial.  The  other 
festoons  are  applied  to  the  anterior  and  jiosterior  walls  of  the  ventricle ; 
3,  An   external   face,  which  receives  the  insertion  of  a  great  number  of 


RIGHT    SIDE    OF    THE    HEART    LAID   OPEN. 

1,  Cavity  of  right  auricle;  2,  Appendix  auri- 
culse,  with  musculi  pectinati ;  3,  Anterior 
vena  cava  opening  into  the  upper  part  of 
the  right  auricle  ;  4,  Posterior  vena  cava ; 
5,  Fossa  ovalis,  surrounded  by  the  annulus 
ovalis  ;  6,  Eustachian  valve  ;  7,  Opening 
of  the  coronary  sinus  ;  8,  Coronary  valve  ; 
9,  Entrance  of  auricular-ventricular  open- 
ing.— a,  Right  ventricle  ;  6,  Its  cavity ;  c, 
Conus  arteriosus,  or  infundiljulum  ;  d,  Pul- 
monary artery ;  e,  f,  Tricuspid  valve ;  g, 
One  of  the  musculi  papillares  to  which 
the  curtains  of  the  tricuspid  valve  are 
attached  by  chorda;  tendina; ;  h,  Columnse 
carneas ;  i,  Two  musculi  papillares  of  val- 
vular curtain  ;  /,  I,  Chords  tendineee  ;  m, 
Semilunar  valves  of  pulmonary  artery ; 
M,  Apex  of  left  appendix  auriculae ;  o,  Left 
ventricle. 


THE  HEART. 


505 


tendinous  cords ;  4,  An  internal  face,  which  becomes  superior  when  the 
valve  is  raised  to  close  the  opening,  at  which  period  it  constitutes  the  floor 
of  the  auricular  cavity. 

Pulmonary  opening. — This  orifice  represents  the  embouchure  of  the 
pulmonary  artery.  Situated  iu  front  and  to  the  left  of  the  preceding,  and 
a  little  higher,  it  occupies  the  summit  of  a  kind  of  infundibulum  formed  by 
the  left  c  )mpartment  of  the  ventricle  being  prolonged  ujiwards.  It  is 
perfectly  circular,  smaller  than  the  artery  to  which  it  gives  origin,  as  well 
as  the  auriculo -ventricular  opening,  from  which  it  is  separated  by  a  species 
of  muscular  spur,  to   which  is 

attached   the   principal   festoon  F'g-  261. 

of  the  tricuspid  valve. 

The  pulmonary  opening  is 
furnished  with  tliree  valves  :  the 
sigmoid  (or  semicircular),  sus- 
pended over  the  entrance  to  the 
pulmonary  artery,  and,  as  has 
been  ingeniously  remarked  (by 
Winslow),  like  three  pigeon's 
nests  joined  in  a  triangle. 
These  valves  are  remarkable  for 
their  thinness;  a  circumstance 
which  does  not  interfere  with 
their  solidity.  They  present : 
an  external,  convex  border,  at- 
tached to  the  margin  of  the 
orifice  and  to  the  walls  of  the 
pulmonary  artery ;  a  free  bor- 
der, straight  when  pnlled  tense, 
concave  when  left  to  itself,  and 
sometimes  provided  in  its  middle 
with  a  small,  though  very  hard, 
tubercle,  the  nodule  of  Arantius 
{nodidi  Arantii)  ;  a  superior, 
concave  face ;  and  an  inferior,  convex  one.  The  sigmoid  valves  are  raised 
and  applied  to  the  walls  of  the  vessel  whose  entrance  they  garnish,  when 
the  ventricle  contracts  and  sends  the  venous  blood  into  the  lung.  When 
this  contraction  ceases,  they  fall  back  one  against  the  other  by  that  part 
of  their  inferior  face  next  to  their  free  border,  so  as  to  oppose  the  reflux  of 
the  blood  into  the  ventricular  cavity.' 

Eight  Auricle. — The  cavity  of  the  right  auricle  represents  a  very 
concave  lid  or  cover  surmounting  the  auriculo-ventricular  opening,  and 
is  prolonged,  anteriorly,  by  a  curved  cid-de-sac.  It  ofters  for  study  this 
anterior  cul-de-sac,  a  posterior,  external,  and  internal  wall,  as  well  as  a  superior 

'  It  has  been  repeated,  ad  nauseam,  that  the  occhision  of  the  arterial  opening's  results 
from  the  juxtaposition  of  the  free  border  of  the  siumoid  valves;  even  the  small  tubercle 
in  the  middle  of  this  border  has  been  considered  to  play  its  part  in  closing  the  triangular 
central  space  left  v.hen  thes»!  valves  meet.  In  passing  the  finger  into  the  pulmonary 
artery  of  a  living  animal,  to  explore  the  function  of  these  membranous  folds,  it  is  readily 
perceived  that  they  ccime  in  contact  by  a  large  poition  of  their  convex  face,  and  not  alone 
by  their  free  border.  Tiiis  arrangement  is  such,  thut  we  have  with  much  difficulty  tried 
to  prcxluce  an  insufficiency  of  contact  by  keeping  one  of  the  valves  up  against  the 
■walls  of  the  vessel  with  the  tinger;  but  the  others  came  down  against  the  finger  and 
applied  themselves  around  it  so  as  to  exactly  close  the  orifice. 


SECTION    OF    THE    HKAUT    AT    THE    LEVEL    OF    THE 
VALVES. 

P,  Pulmonary  artery  ;  A,  Aorta  ;  M,  Mitral  valve  ; 
T,  Tricuspid  valve. 


506  THE  CIRCULATORY  APPARATUS. 

wall  or  roof,  and  the  auriculo-ventricular  opening,  which  occupies  the  whole 
floor  of  the  cavity.     This  orifice  has  been  ah-eady  described. 

The  anterior  cul-de-sac  is  in  the  appendix  auriculae ;  it  is  divided  by  a 
great  number  of  muscular  columns  of  the  second  and  third  orders  (musculi 
pectinaii),  into  deep  and  complex  areolae. 

The  posterior  wall  responds  to  the  interauricular  septum ;  it  is  smooth, 
and  usually  marked  by  an  oblique  and  more  or  less  deep  cul-de-sac  (or  de- 
pression), the  remains  of  Botal's  foramen.  This  depression  is  surrounded 
by  the  ring  of  Vieussens  (annulus  ovalis)  and  is  named  the  fossa  ovalis  ;  it  is 
only  separated  from  the  left  auricular  cavity  by  a  thin  membrane,  a  vestige 
of  the  valve  circumscribing  the  interauricular  opening  in  the  foetus. 

The  external  loall  is  areolated,  and  perforated  behind  and  below  by  two 
orifices,  the  largest  of  which  is  the  embouchure  of  the  posterior  vena 
cava,  the  other  the  opening  of  the  largo  coronary  vein.  Both  are  destitute 
of  valves,  though  these  are  found  at  a  short  distance  in  the  coronary  vein. 
The  bronchial  vein  sometimes  opens  separately  beside  the  latter. 

The  internal  icall  is  smooth. 

The  superior  wall,  or  roof  of  the  auricle,  shows  the  openings  of  the 
anterior  vena  cava  and  vena  azygos ;  the  latter  only  is  provided  with  valves, 
which  are,  however,  not  always  present.  On  this  wall  are  also  remarked,  in 
front,  areolae  separated  by  muscular  columns. 

The  thickness  of  the  right  auricular  walls  is  very  irregular,  in  conse- 
quence of  the  reliefs  sculptured  on  the  inner  face  of  that  cavity.  In  some 
points  it  is  about  the  third  of  an  inch,  and  in  others,  particularly  in  the 
small  cids-de-sac  formed  by  the  reticulations,  it  is  sometimes  so  thin  as 
to  appear  exclusively  formed  by  the  union  of  the  external  and  internal 
serous  membrane. 

(When  the  vena  azygos  opens  behind,  there  is  between  it  and  the  orifice 
of  the  anterior  vena  cava,  a  muscular  lamella  with  a  free  concave  border, 
which  forms  a  kind  of  valve  whose  extent  is  very  variable.  Behind  this  vena 
cava  is  a  thick  eminence,  the  tuhercidum  Loweri ;  this  has  the  form  of  a 
crescent,  open  in  front,  and  elongated  from  right  to  left  at  the  superior 
border  of  the  septum.  The  anterior,  or  left  border  of  the  fossa  ovalis,  is 
thin  and  prominent,  and  constitutes  the  Eustachian  valve :  a  muscular 
membranous  fold  of  a  semilunar  shape,  with  a  concave  free  border  directed 
to  the  right  and  behind.  It  is  of  little  use  in  animals,  because  of  their 
horizontal  position.  Immediately  beneath  the  posterior  vena  cava,  and 
between  it  and  the  coronary  vein,  is  a  small  membranous  crescent — the  valve 
of  TJiehesius.) 

G.  Eed-blood  (or  Aortic)  Heart. — This  is  also  called  the  posterior 
heart,  and  more  frequently  the  left  heart,  because  it  is  situated  behind  and 
to  the  left  of  the  dark-blood  heart.  Its  general  disposition  otherwise  exactly 
resembles  that  of  the  latter  receptacle. 

Left  Ventricle. — This  is  a  cylindro-conical  cavity,  whoso  transverse 
section  gives  an  irregularly  circular  figure.  Its  walls  attain  a  thickness  of 
from  li  to  If  inches,  except  towards  the  apex  of  the  heart,  where  they  are 
extremely  thin.  They  are  less  reticulated  than  those  of  the  right  ventricle, 
and  exhibit  several  columns  of  the  second  order,  as  well  as  two  enormous 
muscular  pillars — an  external  and  internal,  for  the  attachment  of  the  tendons 
of  the  auriculo-ventricular  valve.  The  apex  of  the  cavity  forms  a  re- 
ticulated cul-de  sac,  which  occupies  the  point  of  the  heart.  The  base  is 
perforated  by  the  auriculo-ventricular  and  the  aortic  openings.  The  auriculo' 
ventricular  opening,   precisely   similar   to   that  of  the  right  ventricle,  is 


THE  HEART. 


507 


Ficr.  262. 


provided  with  a  circular  membrane,  tbe  mitral  (or  hicusjml)  valve,  because  it  is 
cut  into  several  festoons,  of  whicb  two  are  the  principal :  the  one  anterior, 
the  other  posterior,  simulating  in  their  outline  the  two  faces  of  a  bishop's 
mitre.  The  anterior  festoon  is  the  largest,  and  is  attached  to  the  limit  of 
.the  two  orifices,  isolating  from 
the  ventricular  cavity  a  diver- 
ticulum which  corresponds,  in 
every  respect,  to  the  pulmonary 
infundibulum.  The  posterior 
festoon  is  applied  to  the  walls 
of  the  ventricle.  Between  these 
two  there  are  usually  two  second- 
ary festoons,  making  up  the 
total  number  to  four  ;  fre- 
quently there  is  an  accessory 
fold,  situated  on  the  right  side, 
and  fairly  developed ;  the  valve 
is  then  tricuspid,  like  that  of 
the  right  ventricle.  Sometimes 
two  of  these  rudimentary  folds 
are  found  on  the  left  side 
—making  five  festoons  in  all. 
The  aortic  opening,  so  named 
because  it  constitutes  the  origin 
of  the  aorta,  is  i)laced  in  front 
and  to  the  left  of  the  auriculo- 
ventricular  ojiening,  from  which 
it  is  only  separated  by  a  thin 
muscular  spur,  to  which  is  at- 
tached the  adherent  border  of 
the  great  festoon  or  curtain  of 
the    mitral  valve.    It  does  not 

dift'er  in  anything  from  the  pulmonary  opening,  and  like  it,  is  provided  with 
three  sigmoid  valves. 

Left  Auricle. — As  in  the  right  auricle,  this  forms  a  kind  of  cover 
above  the  auriculo- ventricular  opening.  Smooth  behind,  in  front,  inwards 
and  outwards,  its  cavity  presents  a  reticulated  cul-de-sac,  which  occupies  the 
appendix  auriculae  ;  and  a  superior  wall,  also  reticular,  having  from  foui"  to 
eight  orifices,  the  openings  of  the  pulmonary  veins.  These  orifices  have  no 
valves.  (Carneae  columnje  of  the  third  kind  are  also  present,  but  chiefly 
between  the  two  j)osterior  pillars ;  small  ones  are  very  numerous  on  the 
borders  and  summit  of  the  ventricle.  The  columns  of  the  second  order  are 
simple  or  ramous,  and  pass  from  the  angles  of  union  of  the  walls  and  the 
point  of  the  cavity ;  others  on  the  posterior  wall  go  to  the  borders  and  the 
interval  between  the  two  pillars.  The  most  remarkable  are  bands  extending 
from  one  wall  to  the  other,  the  two  principal  of  which  are  long,  strong,  and 
ramous ;  they  are  fixed,  on  the  one  side,  to  the  centre  of  the  great  posterior 
reliefs,  and  ascend  to  be  implanted,  on  the  other  side,  into  the  middle  of 
the  anterior  wall.) 

4.  Structure  of  the  Heart. 

Preparation. — Before  proceedinj;  lo  dissect  the  muscular  fibres  of  the  heart,  it  is 
indispensable  to  keep  that  viscus  in  boiling  water  for  half  or  three-quarters  of  an  hour. 
It  should  then  be  immediately  immersed  in  cold  water,  to  prevent  the  desiccation  of  the 


LEFT   CAVITIES   OF   HEART   LAID   OPEN. 

1,  Cavity  of  left  auricle  ;  2,  Cavity  of  appendix 
auriculae  ;  3,  Opening  of  two  right  pulmonary 
veins ;  4,  Sinus  into  which  left  pulmonary  veins 
open  ;  5,  Left  pulmonary  veins ;  (3,  Auriculo-ven- 
tricular  opening ;  7,  Coronary  vein  lying  in 
auriculo-ventricular  groove ;  8,  Left  ventricle ; 
9,  9,  Cavity  of  left  ventricle. — a,  Mitral  valve, 
its  curtains  connected  by  chordae  tending  to  b,  b, 
Columns  carneae ;  c,  c.  Fixed  columnae  carnse 
on  inner  surface  of  ventricle  ;  t,  Point  of  appendix 
of  right  auricle. 


508  THE  CIRCULA  TOR  Y  AFPARA  TVS. 

serous  membrane  covering  it,  and  which  must  be  at  once  removed.  The  furrows  should 
then  be  cleared  of  their  vessels  and  fat ;  this  renders  tlie  superficial  muscular  fibres 
very  apparent.  The  same  result  may  be  attained  by  immersing  the  heart  in  vinegar  or 
dilute  hydrochloric  acid.  To  isolate  the  ventricles  and  unitive  fibres  from  each  other, 
the  following  procedure  may  be  adopted :  After  removing  the  auricular  mass  and 
dissectiug  the  fibrous  rings,  the  unitive  fibres  around  tliese  are  divided  with  tlie  point  of 
the  scalpel,  care  being  taken  not  to  injure  the  proper  fibres.  Then,  with  the  aid  of  the 
finger-nail  or  handleOf  the  scalpel,  follow  the  more  or  less  artificial  limit  of  these  two 
series  of  muscular  planes  in  a  spiral  manner;  the  vessels  passing  through  the  walls  of 
the  heart  must  be  cut  tlirongh.  The  same  course  is  followed  in  the  substance  of  the 
interventricular  septum,  in  oider  to  separate  the  two  sacs  formed  by  the  proper  fibres. 

(It  will  be  found  that  the  simplest  and  best  way  to  prepare  the  heart  for  an  examina- 
tion of  its  fibres,  is  to  steep  it  in  a  very  weak  dilution  of  hydrochloric  acid.  Remove  the 
serous  membrane,  and  the  fibres  can  then  be  traced,  layer  by  layer,  fiom  their  origin  to 
their  termination.) 

The  muscular  tissue  composing  the  heart  rests  on  a  fibrous  framework, 
disposed  in  rings  around  the  auriculo-ventricular  and  arterial  openings ;  it 
receives  vessels  and  nerves,  and  while  covered  in  the  internal  cavities  by  two 
independent  serous  membranes,  it  is  enveloped,  externally,  by  another 
membrane  of  the  same  kind.  An  annular  frameworJc,  muscular  tissue  proper, 
vessels  and  nerves,  and  serous  tunics — such  are  the  elements  entering  into 
the  organisation  of  the  heart. 

A.  Fibrous  Eings. — These  are  also  named  the  fibrous  zones  of  the  heart, 
and  are  four  in  number :  one  for  each  of  the  openings  at  the  base  of  the 
ventricles. 

The  two  arterial  zones  (the  pulmonary  and  aortic)  constitute  two  complete 
rings,  which  are  not  disjjosed  in  a  circular  manner  around  the  pulmonary 
aortic  openings,  but  are  divided  into  three  regular  festoons  with  their  con- 
cavities superior  and  internal,  and  which  corresjiond  to  the  insertions  of 
the  three  sigmoid  valves.  These  zones  are  continuous,  by  their  superior  and 
external  contour,  with  the  walls  of  the  arteries,  from  which  they  are  only  dis- 
tinguished by  their  whitish-grey  colour  and  slight  elasticity,  the  arterial 
tissue  being  yellow  and  very  elastic.  Their  internal  and  inferior  outline 
sends  three  thin  prolongations  into  the  serous  duplicatures  of  the  sigmoid 
valves. 

The  auriculo-ventricular  zones  do  not  completely  surround  the  openings 
they  circumscribe.  They  are  flattened,  brilliant-white  tendons,  laid  one 
against  the  other  at  the  level  of  the  ventricular  septum,  and  against 
the  aortic  ring ;  they  turn  to  the  right  and  left  around  the  auriculo- 
ventricular  openings,  but  without  joining  at  their  extremities,  which  are 
dispersed  as  fibrillas  in  the  muscular  tissue  of  the  ventricles.  Above,  these 
zones  give  attachment  to  the  muscular  fibres  of  the  auricles ;  below,  to  the 
ventricular  fasciculi.  Their  internal  and  inferior  border  is  jn'olonged  into 
the  mitral  and  tricuspid  valves,  and  is  continuous,  through  these  valves, 
with  the  tendinous  cords  fixed  to  the  walls  of  the  ventricles.  Some  of  these 
cords,  generally  the  strongest,  are  even  directly  insei'ted  into  the  auriculo- 
ventricular  zones. 

It  must  be  noted  that,  in  Solipeds,  there  is  constantly  found,  at  the 
point  where  the  aortic  and  auriculo-ventricular  zones  lie  against  each  other, 
a  more  or  less  developed  cartilaginous  body,  which,  in  the  larger  Ruminants, 
is  transformed  into  true  bone.  (Lavocat  speaks  of  two  cartilaginous  points, 
one  to  the  right,  at  the  junction  of  the  aortic  with  the  left  auriculo- 
ventricular  ring  and  the  cardiac  septum;  the  othei',  less  developed,  on  the 
left,  at  the  origin  of  the  left  ventricular  groove.) 

B.  MuscuLAU  Tissue. — The  muscular  tissue  composing  the  mass  of  the 


TEE  HEART, 


509 


heart  belongs  to  the  system  of  organic  life,  as  it  contracts  without  the 
participation  of  the  will.  Nevertheless,  it  is  formed  of  red  striated  fibres, 
wliich  only  differ  from  the  muscular  fibres  of  animal  life  in  being  less  in 
diameter.  As  in  the  tongue,  these  fibres  also  possess  ramifications  that  unite 
them  to  each  other:  they  are  likewise  very  granular.  (They  are  more 
friable  than  those  of  the  muscular  system  generally ;  the  sarcolemma  is 
more  delicate,  and  the  longitudinal  markings  and  nuclei  are  more  apparent, 
the  latter  being  placed  in  the  axis  of  the  fibre  along  with  rows  of  minute 
fatty  granules,  which  are  extremely  numerous  in  fatty  degeneration  of  the 
heart.  The  connective  tissue  is  scanty  ;  so  that  the  fibres  lie  closer  together 
while  forming  innumerable  anastomosing  networks  and  interlaciiigs— a 
character  peculiar  to  the  muscular  organisation  of  the  heart.  It  has  been 
asserted  that  there  is  no  sarcolemma.) 

The  striation  of  the  muscular  fibres  of  the  heart, 
which  constitutes  an  exception  in  the  laws  of  organisa- 
tion, may  be  explained  to  a  certain  point  by  the  nature 
of  the  functions  imposed  on  the  muscular  tissue  of  the 
organ.  Charged  to  j^ropel  the  blood  into  the  arterial 
ramifications  by  successive,  instantaneous,  and  vigorous 
contractions,  the  heart,  probably,  would  not  have  been 
capable  of  executing  such  movements  if  it  had  been  c(mi- 
posed  of  organic  fibres,  as  these  come  into  action  in  a 
steady,  slow,  and  prolonged  manner.  The  ramifications 
that  unite  the  fibres,  and  establish  a  kind  of  solidarity 
between  them,  afford  a  clue  to  the  simultaneousness  in 
the  movements  of  the  auricles  and  ventricles. 

It  is  also  worthy  of  remark,  that  between  these 
fibres  there  is  so  little  connective  tissue  that  the  majority 
of  anatomists  absolutely  deny  its  existence. 

The  arrangement  of  the  muscular  fasciculi  of  the 
heart  has  been  the  object  of  numerous  recent  investigations,  which  have 
only  complicated  what  was  already  known  on  the  subject.  We  will  endea- 
vour to  sum  uj),  as  simply  as  possible,  this  arrangement,  in  examining  it  in 
the  different  compartments  of  the  organ.  The  following  is  the  disposition 
of  the  fasciculi,  considered  successively  in  the  ventricles  and  auricles  : 

1.  Fibres  of  the  Ventricles. — According  to  the  remark  of  Winslow, 
we  may  compare  the  ventricles,  in  regard  to  the  arrangement  of  the  fibres 
essentially  composing  them,  to  "two  muscular  sacs  inchided  in  a  third:" 
that  is  to  say,  each  ventricle  is  formed  of  proper  muscular  fibres,  covered 
externally  by  a  layer  of  unitive  fibres,  which  envelop  the  two  ventricles  in 
common. 

a.  Proper  fibres  of  tit e  ventricles. — Taken  altogether,  these  fibres  repre- 
sent, for  each  cavity,  a  hollow  cone,  open  at  both  its  extremities  :  at  the 
superior  extremity,  by  the  auriculo-ventiicular  and  arterial  orifices ;  and  at  the 
inferior  extremity,  by  an  aperture  which  admits  the  reflected  fibres  of  the 
common  layer.  All  form  loops  attached,  by  their  extremities,  to  the  out- 
line of  the  superior  orifices,  on  the  fibrous  zones,  and  are  rolled,  more  or 
less  obliquely,  around  the  axis  of  the  ventricles.  It  is  from  the  apposition 
of  the  right  and  left  systems  that  the  ventricular  septum  is  formed. 

h.  Unitive  fibres  of  the  ventricles.— These  are  disposed  as  an  external 
shell  enveloping  the  ju-oper  fibres.  They  leave  the  fibrous  zones  at  the  base 
of  the  heart,  and  descend  towards  its  apex  :  those  of  the  right  side,  by  inclining 
forward  ;    the  anterior,  in  following  the  direction  of  the  great  axis  of  the 


AN  ASTOMOSING  Jl  U  S- 
CULAR  FIBRES  OF 
HEART. 


510  THE  CIRCULATORY  APPARATUS. 

ventricles ;  those  of  the  left  face,  by  directing  their  course  from  above  to 
below,  and  before  to  behind ;  and  the  posterior,  in  rolling  themselves  from 
left  to  right  around  the  left  ventricle.  On  arriving  near  the  point  of  the 
heart,  they  turn  from  left  to  right,  and  before  to  behind,  in  forming  a  twisted 
spire ;  then  they  are  reflected  from  below  upwards,  to  enter  the  inferior 
extremity  of  the  ventricles,  on  the  internal  face  of  whose  proper  fibres  they 
spread  and  ascend  to  the  fibrous  zones  at  the  base  of  the  heart,  where  they 
terminate.  Some  of  these  reflected  iibres  are  disposed  in  relief  to  constitute 
the  columnse  carnese,  and  I'each  the  auriculo-ventricular  zones  through  the 
medium  of  the  tendinous  cords  which  directly  connect  these  fibrous  rings 
with  the  summits  of  the  muscular  pillars. 

Such  is  the  general  disposition  of  the  unitive  fibres  of  the  ventricles  ; 
and  it  will  be  seen  that  they  form  a  superficial  and  a  deep  or  reflected  plane, 
between  which  are  comprised  the  fasciculi  proper  to  each  ventricular  pouch. 

The  unitive  fibres  of  the  ventricles,  therefore,  form  collectively  a  kind 
of  figure  8,  the  smallest  loop  of  which  is  at  the  jioint  of  the  heart ;  there 
the  fibres  ai'e  heaped  together,  leaving  in  the  centre  of  the  loop  a  very  small 
space,  through  which  it  is  possible  to  pass  a  probe  into  the  ventricle,  without 
piercing  anything  but  the  external  and  internal  sereus  membranes  of  the 
organ. 

2.  FiBEES  OF  THE  AuRiCLES. — The  fibres  of  the  auricles  are  either 
common  to  the  two  cavities,  or  proper  to  each.  The  unitive  fibres  con- 
stitute two  thin  bands — a  right  and  left,  cai'ried  from  one  auricle  to  the 
other. 

T\\Q  proper  fibres  are  divided  into  several  fasciculi,  some  of  which  are 
arranged  in  rings  around  the  auriculo-ventricular  opening;  others  in  inter- 
woven loops,  and  others,  again,  in  sphincters,  which  surround  the  embouchures 
of  the  veins.  These  fibres  are  arranged  in  such  a  manner  that,  in  contracting, 
they  diminish  the  auricles  by  their  superior  and  lateral  planes  and  ex- 
tremities, and  propel  the  blood  towards  the  auriculo-ventricular  openings. 

(The  arrangement  of  the  muscular  fibres  constitutes  the  most  remarkable 
feature  in  the  anatomy  of  the  heart.  We  have  seen  that  the  auricles,  as  well 
as  the  ventricles,  possess  not  only  fibres  proper  to  each  compartment,  but 
also  unitive  or  common  fibres  which  assure  the  simultaneousness  in  action 
of  the  similar  or  homologous  cavities.  Besides,  the  fibres  of  the  auricles 
and  those  of  the  ventricles  are  distinct,  and  not  continuous ;  so  that,  from 
their  independence  of  each  other,  it  results  tliat  these  two  sections  of  the  heart 
may  act  separately,  and  contract,  not  simultaneously,  but  alternately,  a  con- 
dition indispensable  to  the  free  course  of  the  blood.  The  extremely  fine 
and  close  connective  tissue  uniting  the  muscular  fibres,  is  another  peculiarity 
of  structure  that  must  be  favourable  to  tlie  solidarity  of  their  action, 
which  ought  to  be  simultaneous.  Adipose  tissue  is  only  found  in  the 
grooves  on  the  surface  of  the  organ,  around  the  vessels  lodged  in  them,  and 
particularly  at  its  base,  between  the  large  arterial  trunks.) 

C.  Vessels  and  Nerves  op  the  Heart. — Blood  is  carried  to  the  muscular 
tissue  of  the  heart  by  two  large  vessels,  the  coronary  arteries.  They  emanate 
from  the  trunk  of  the  aorta,  at  the  sigmoid  valves,  and  each  divides  into 
tivo  principal  branches  :  one  i^assing  along  the  horizontal,  the  other  in  the 
vertical  furrow  of  the  lieart.  Collectively,  these  arteries  form  two  circles, 
which  surround  the  heart  in  intersecting  it  at  a  right  angle  in  the  auriculo- 
ventricular  groove. 

The  blood  is  carried  from  the  walls  of  the  heart  by  a  single  but  impor- 
tant vein,  which  empties  itself  into  the  right  auricle. 


THE  HEART. 


511 


Tlie  lymphatics  follow  the  arteries,  passing  along  the  visceral  layer  of 
the  pericardium,  and  entering  the  cluster  of  glands  situated  near  the  base  of 
the  heart.  (The  eudocardiuni,  especially  in  the  ventricles,  has  a  network 
of  fine  lymphatics,  the  walls  of  which  consist  of  only  a  single  layer  of 
intimately-adhering  cells.  None  have  been  traced  upon  the  chordae  tendineae, 
and  very  few  upon  the  auriculo-ventricular  and  semilunar  valves.) 

The  nerves  of  the  heart,  furnished  by  the  cardiac  plexus,  come  from  the 
j)neumogastric  and  sympathetic.  The  tubes  are  small,  and  show  some  cells 
in  their  course.  In  addition  to  these,  the  heart  is  provided  with  a  particular 
ganglionic  system,  to  which  Eemak  has  called  attention.  It  is  believed  that 
there  exist  three  ganglia  in  different  points  of  the  cardiac  parietes,  and  that 
on  these  depend  the  movements  of  the  organ.  (According  to  Carpenter,  the 
nerves  of  the  heart  are :  1,  Minute  ganglia  and  fibres  of  the  sympathetic, 
situated  in  the  walls  of  the  cavities,  and  especially  in  the  auriculo- 
ventricular  furrow ;  2,  Fibres  derived  from  the  cervical  portion  of  the 
symi)athetic,  and  passing  to  the  cardiac  jjlexus,  between  the  aorta  and 
pulmonary  artery  ;  3,  Cerebro-spinal  fibres  entering  the  inferior  cervical  or 
stellate  ganglion,  and  proceeding  to  the  same  plexus,  and  probably  derived 
from  a  centre  situated  in  the  brain  and  spinal  cord ;  and,  4,  Fibres  coursing 
in  the  vagus,  and  originating  in  a  centre  situated  in  the  medulla  oblongata. 
The  first  three  of  these  ganglia  and  fibres  probably  collectively  con- 
stitute the  excito-motor  system  of  the  heart,  the  fourth  is  an  inhibitory, 
restraining,  or  regulo-motor  centre.) 

D.  Serous  Membranes  of  the  Hex\rt. — These  are  three  in  number  : 
two  internal,  or  endocardial,  one  of  which  occupies  the  right,  the  other  the 
left  cavity ;  and  an  external,  a  dependency  of  the  fibro-serous  sac  which 
contains  the  heart. 

1.  Internal  serous  membranes,  or  endocardia. — These  two  membranes, 
independent,  like  the  cavities  they  line,  are  spread  over  the  auricular  and 
ventricular  walls,  covering  the  tendinous  or  muscular  columns  attached  to 
these  walls,  and  are  prolonged  into  the  veins  and  arte- 
ries, to  form  the  internal  tunic  of  these  vessels.  At 
the  auriculo-ventricular  and  arterial  openings,  they  con- 
stitute a  duplicature  for  the  valves  situated  there. 
These  valves  are,  therefore,  due  to  the  projection  of  a 
circular  fold  of  the  endocardia,  between  the  two  layers 
of  which  a  thin  prolongation  of  the  fibrous  zones  from 
the  base  of  the  heart  is  insinuated.  In  the  auriculo- 
ventricular  valves  there  is  also  found,  beneath  the 
internal  or  superior  layer,  muscular  fibres  furnished  by 
the  auricles. 

The  endocardium  of  the  right  heart  has  a  red  tint, 
Avhich  is  deepest  in  the  ventricle.  In  the  left  heart, 
this  tint  is  slightly  yellow,  especially  in  the  walls  of 
the  auricular  appendix,  which  may  be  attributed  to  the 
presence  of  a  thin  layer  of  yellow  elastic  tissue  that 
covers  the  adherent  face  of  the  membrane. 

(Tlie  endocardium  consists  of  three  layers:  1,  A 
thin  bed  of  white  fibrous  tissue,  connecting  it  to  the 
muscular  structure ;  2,  A  middle  layer,  composed  of 
elastic  tissue  which  is  very  abundant  in  the  auricles ; 
and  3,  An  epithelium,  consisting  of  a  single  or  double 
layer  of  somewhat  elongated,  polygonal,  pavement  nucleated  cells.) 


Fig.  264. 


EPITHELIUM   OF   THE 
ENDOCARDIUM. 

1,  Nucleated  cells  as- 
suming the  fusiform 
figure ;  2,  Polygonal 
nucleated  cells. 


512  THE  CIRCULATORY  APPARATUS. 

2.  External  serous  membrane. — This  is  the  visceral  lining  membrane  of 
the  pericardium,  the  description  of  which  follows. 

5.  The  Pericardium.     (Fig.  234,  c.) 

Preparation. — Place  the  animal  in  the  second  position,  and  remove  the  sternal  ribs  by 
separating  the  cartilages  and  luxating  tlieir  costo-vertebral  articulations.  Tiiis  pro- 
cetlure  permitj  the  study  of  the  situation  and  general  dispo-ition  of  tiie  In  art  and 
pericardium  But  in  order  more  easily  to  exaraiue  tlie  reciprocal  arrangement  of  tluse 
two  parts,  it  is  necessary  to  extract  tliem  from  the  thoracic  cavity  by  tearing  through  the 
sternal  insertion  of  the  pericardium. 

The  pericardium,  or  proper  serons  membrane  of  the  heart,  is  a  membranous 
sac  inclosing  that  organ,  fixing  it  in  the  thoracic  cavity,  and  favouring  its 
movements  by  its  polished  surface. 

This  sac  is  formed  by  a  fibrous  layer,  within  which  is  spread  a  serous 
membrane,  divided  into  two  parts — one  parietal,  the  other  visceral. 

The  fibrous  layer  of  the  pericardium  presents  somewhat  the  general  form 
of  the  heart  Its  internal  surface  is  covered  by  the  parietal  portion  of  the 
serous  membrane.  The  external  surfiice  corresponds  to  the  two  laminas  of 
the  mediastinum.  lU  summit  (or  apex),  depressed  on  each  side,  and  elon- 
gated from  before  to  behind,  is  firmly  attached  to  the  superior  face  of  the 
sternum,  from  the  fourth  rib  to  the  origin  of  the  xiphoid  cartilage.  By 
its  base,  it  is  fixed  to  the  large  vessels  going  to  and  leaving  the  heart,  where 
it  is  continuous  with  their  cellular  sheath,  and  where  it  sends  some  fi])res  to 
the  longus  colli. 

The  serous  membrane  of  the  pericardium  has  been  well  compared  by 
Bichat  to  a  cotton  night-cap,  the  external  part  of  which  would  represent  the 
parietal  layer,  and  the  inverted  part  the  visceral  division  of  that  membrane. 
The  parietal  layer  adheres  in  the  most  intimate  manner  to  the  internal  face 
of  the  fibrous  tunic,  and  is  seen  to  be  reflected,  to  form  the  visceral  portion, 
around  the  pulmonary  arteries  and  the  aorta  to  a  certain  distance  from 
their  origin,  and  on  the  pulmonary  veins.  Tlie  visceral  layer  envelops 
in  common  the  two  arterial  trunlvs,  covers  a  small  part  of  the  venaj  cavae, 
particularly  the  anterior,  spreads  over  the  insertion  of  tlie  pulmonary  veins, 
and  then  descends  on  the  auricles  and  ventricles.  The  free  iace  of  this 
layer  is  in  contact  with  that  of  the  parietal  layer ;  the  adherent  face  is 
applied  to  the  tissue  of  tlie  heart  or  that  of  the  large  vascular  trunks,  except 
at  the  horizontal  and  vertical  grooves,  where  it  rests  on  the  coronary  vessels, 
and  on  the  mass  of  adipose  tissue  constantly  accumulated  on  their  track. 

In  the  living  animal,  the  cavity  of  the  pericardium  is  never  entirely 
filled  by  the  heart,  whose  movements  are,  therefore,  allowed  much  more 
liberty.  Otherwise,  as  it  does  not  contain  any  gas,  nor  a  sensible  proportion 
of  fluid, ^  its  walls  are  immediately  applied  to  the  surface  of  the  heart. 

Blood  reaches  the  pericardium  by  the  mediastinal  arteries.  Its  walls 
receive  some  sympathetic  nerve-fibres. 

(The  pericardium  is  composed  of  a  fine  network  of  elastic  fibres  adhering 
to  the  muscular  structure  of  the  heart  by  one  surface,  and  covered  by  a 
single  or  double  layer  of  tesselated  epithelium  on  the  other.     Gurlt,  in  1867, 

'  With  horses  in  lienUh,  the  fluid  exhaled  into  the  pericardium  is  barely  sufficient  to 
moisten  and  lubrify  the  free  surface  of  its  serous  membrane.  But  in  those  worn  out  and 
enfeebled  by  age,  privations,  or  disease,  it  is  not  rare  to  see  it  accumulated  in  grenter  or 
le-s  quantity.  To  verify  this,  however,  an  examination  ought  to  take  place  immedintely 
after  death,  as  the  accumulation  of  iluid  in  the  serous  cavities  by  cadaveric  exhalation  is 
common  in  all  animals. 


THE  HEART.  513 

described  a  thin  muscle,  nine  inches  long,  situated  between  the  pericardium 
and  the  diaphragm  of  the  Horse.) 

6.  Action  of  the  Heart. 

The  function  of  the  heart  is  to  maintain  the  circulation  of  the  blood,  bv 
the  rhythmical  contractions  of  its  two  pouches.  The  right  pouch  sends 
that  fluid  to  the  lungs,  whence  it  returns  to  the  left  pouch,  and  from 
this  it  is  thrown  into  all  parts  of  the  body,  and  is  brought  back  again  to  the 
right  heart.  These  contractions  take  place  simultaneously  in  the  two  cardiac 
compartments. 

In  taking  the  heart  at  the  moment  when  it  is  in  a  state  of  repose :  that 
is,  in  the  intervals  between  the  two  contractions,  we  find  that  its  two 
pouches  are  being  rapidly  filled  with  the  blood  brought  to  it  by  the  venous 
openings.  When  sufficiently  replete,  the  auricles  slightly  contract  and 
push  a  portion  of  the  fluid  they  contain  into  the  ventricles  :  these  contracting 
immediately  after,  to  propel  the  blood  into  the  arterial  ramifications.  This 
passage  of  the  blood  into  the  arteries  is  a  necessary  consequence  of  the 
contraction  of  the  ventricles,  as  at  the  moment  of  this  contraction  the 
auriculo-ventricular  valves  are  raised,  and  so  prevent  the  reflux  of  the 
blood  into  the  auricles.  This  fluid  is  then  forced  to  enter  the  arterial 
orifices,  whose  valves  are  separated  under  the  impulsive  effort  communicated 
to  the  column  of  blood.  When  the  heart  returns  to  a  state  of  repose,  these 
valves  fall  down,  preventing  the  return  of  the  blood  into  the  ventricular 
cavities ;  while  the  mitral  and  tricuspid  valves  subside  against  the  walls  of 
these  cavities,  and  thus  again  allow  the  passage  of  blood  through  the 
auriculo-ventricular  openings. 

By  the  term  systole  is  designated  the  contraction  of  the  heart's  cavities, 
and  by  diastole,  the  repose  or  relaxation  of  its  tissue.  For  each  revolution 
of  the  heart  there  is,  therefore :  1,  The  general  diastole  of  the  organ,  during 
which  the  two  cardiac  cavities  are  filled  by  the  afflux  of  venous  blood ; 
2,  The  systole  of  the  auricles,  the  effect  of  which  is  the  repletion  of  the 
ventricles  ;  3,  The  systole  of  the  ventricles,  propelling  the  blood  into  the 
arterial  systems  ;  after  which  comes  another  period  of  general  diastole. 

DIFFEREXTIAL   CHARACTERS   IN  THE   HEAKT   OF   OTHER   THAN   SOLIPED   ANIMALS. 

In  the  Ox,  Sheep,  and  Goat,  the  ventricnlar  mass  of  the  heart  is  more  regularly 
conical  than  in  Solipeds ;  it  has  three  longitudinal  furrows,  one  of  which  is  accessory 
and  passes  behind  the  (left)  ventricle. 

In  the  Ox  two  small  hones,  named  hones  of  the  heart,  are  found  in  the  substance  of 
the  aortic  zone.  The  largest  is  in  the  right  side,  at  the  jioint  where  the  arterial  ring  is 
approximated  to  the  auriculo-ventricular  zones :  the  other,  situated  in  the  left,  is  perhaps 
not  constantly  present.  The  first  is  triangular  in  shape,  curved  to  tlie  right  and  its 
base  directed  upwards.  The  right  face  lies  again&t  the  auriculo-ventricular  opening ; 
the  left  is  covered  by  tiie  walls  of  the  aorta  at  its  commencement.  It  is  about  an  inch  in 
length.  (The  Ox's  heart  averages  from  about  3i  to  4^  lbs.,  that  of  the  Sheep  from  54  to 
7  oz.  It  is  more  elongated  and  pointed  in  Ruminants  than  in  the  Horse  or  Pig.  The 
large  bone  in  the  Ox's  heart  is  elongated  from  before  to  behind,  flattened  laterally  and 
curved  to  the  left ;  its  surface  is  roughened,  arrd  its  length  is  sometimec  about  2  inches. 
The  left,  or  small  bone,  is  usually  flattened  on  each  side  and  triangular,  one  of  its  points 
is  directed  forwards,  another  backward,  and  a  third  inferiorly  ;  its  length  is  about  three- 
quarters  of  an  inch  when  fully  developed.  Besides  the  Ox,  a  small  cross-shaped  bone  is 
found  ill  the  heart  of  the  Sheep,  Pig,  Canrel,  Deer,  Giraffe,  and  i-ometimes  in  the  Horse. 
Kemak  found  in  the  pericardium  of  the  Oz,  at  the  border  of  the  left  auricle,  a  row  of 
villi  similar  to  those  discovered  in  the  border  of  the  chicken's  heart.) 

The  heart  of  the  Pig  resembles  that  of  the  Horse ;  its  direction  is  a  little  more  oblique, 


514 


TEE  CIRCULATORY  APPARATUS. 


and  the  pericardium  is  fixed  to  the  sternum  from  the  third  rib  to  the  xiphoid  appendix, 
as  well  as  to  the  diaphragm.     (The  cartilage  is  not  ossified  until  a  late  period.) 

In  the  Dog  and  Cat,  the  heart  is  oval  or  nearly  globular.  It  is  alraoat  entirely  resting 
on  the  upper  face  of  the  sternum  ;  its  anterior  face  has  become  the  inferior,  and  its 
point,  directeil  backwartis,  touches  the  anterior  surface  of  the  diaphragm.  The  pericardium 
is  attached  to  the  aponeurotic  centre  of  the  diaphragm. 


COMPARISON   OF   THE   HEART   OF   MAN   WITH   THAT   OF   ANtMALS. 

The  human  heart  is  ovoid,  and  similar  to  that  of  the  Carnivora ;  the  ventricular  mass  is 

not  acute  at  its  apex,  as  in 
Fio'.  265.  Soiipeds    and    Ruminants.      Its 

direction  is  modified  in  conse- 
quence of  the  antero-posterior 
flattening  of  the  chest.  It  is 
situated  across  the  median  plane 
of  the  thorax  ,  its  right  face  in 
animals  lias  become  the  anterior 
face  in  Man,  and  is  applied  to  the 
sternum;  the  anterior  burder  is 
in  liim  the  right  border,  and  the 
posterior  the  kft  border. 

The  organ  is  suspended  ob- 
liquely downwards,  forwards,  and 
ti  >  tliH  left ;  consequently,  the  right 
auricle  is  to  the  right  of  the 
sternum,  between  the  third  and 
fourth  rih.s,  and  the  point  on  a 
level  with  the  sixth  left  inter- 
costal space.  The  auricular  ap- 
pendages, paiticularly  the  right, 
are  more  rounded  and  bulging 
than  in  animals.  The  pulmonary 
veins,  four  in  number,  open  on 
the  upper  face  of  the  left  auricle. 

There  are  no  essential  ditfcr- 

HUMAN   LUNGS   AND   HEART;   FRONT   VIEW.  ^^^^^^   ^^   ^^    ,^^^^,1  j.^   j^^    i„t.rnal 

1,  Right  ventricle  2,  Left  ventricle  ;  3,  Right  auricle  ;  conformation.  We  may  indicate 
4,  Left  auricle  ;  5,  Pulmonary  artery ;  6,  Right  the  presence  of  a  fold  that  passes 
pulmonary  artery;  7,  Left  pulmonary  artery;  8,  from,  the  ring  of  Vieussens  to  the 
Ligament  of  ductus  arteriosus;  9,  Arch  of  aorta;  opi  ning  of  the  inferior  vena  cava  : 
10,  Superior  vena  cava  ;  11,  Arteria  mnominata;  12,  this  is  the  Eustachian  valve.  We 
Right  subclavian  vein,  with  the  artery  behind  it ;  niay  also  mention  tiie  Thebesian 
13,  Right  common  carotid  arter\  and  vein,  14,  Left 
vena  innominata ,  15,  Left  carotid  artery  and  vein  ; 
16,  Left  subclavian  vein  and  artery;  17,  Trachea; 
18,  Right  bronchus;  19,  Left  bronchus;  20,  20, 
Pulmonary  veins;  21,  Superior  lobe  of  right  lung; 
22,  Middle  lobe  ;  23,  Inferior  lobe  ;  24,  Superior  lobe 
of  left  lung;  25,  Inferior  lobe. 


valve  at  the  entrance  of  the  coro- 
nary vt  in. 

The  tibious  rings  and  muscular 
fiisciculi  are  disjiosed  as  in  the 
Horse. 

'I'he  pericardium  is  a  conical 
sac ;  but  instead  of  its  base  being 


presented  upwards,  it  rests  against 
the  aponeurotic  centre  of  the  diaphragm  ;  its  summit  is  lost  among  the  large  vestels, 
and  it  adheres  to  the  posterior  face  of  the  sternum. 


SECOND  SECTION. 
The  Arteries. 

CHAPTER  I. 

GENERAL   CONSIDERATIONS. 

The  name  of  arteries  is  given  to  the  centrifugal  vessels,  whicli  carry 
the  blood  from  the  heart  to  the  various  organs.  These  vessels  proceed  from 
the  heart  by  two  trunks,  which  are  perfectly  independent  in  the  adult 
animal ;  they  originate,  one  in  the  right  ventricle,  the  other  in  the  left. 

The  first  of  these  trunks,  destined  to  carry  the  dark  blood,  is  the  pul- 
monary artery.  The  second  conveys  the  red  blood,  and  is  named  the  aorta. 
There  exist,  therefore,  two  groups  of  arteries ;  the  pulmonary  system,  and 
the  aortic  system. 

General  Form.— -Single  at  their  origin,  the  two  arterial  systems  soon 
divide  into  less  voluminous  trunks,  which  again  subdivide  into  successively 
decreasing  canals,  until  at  last  their  diameter  becomes  reduced  to  an  extreme 
degree  of  tenuity.  In  a  word,  the  arterial  trunks  present  the  ramous  dis- 
position of  dicotyledonous  plants.  The  total  volume  of  the  secondary  trunks 
exceeds  that  of  the  primary  trunk,  and  the  same  relation  exists  between  the 
respective  dimensions  of  the  branches  and  their  ramifications,  to  the  ultimate 
divisions  of  the  artery.  In  tracing  all  the  ramifications  of  one  of  these  systems 
to  a  single  canal,  it  will  then  be  found  that  this  canal  is  incessantly  increas- 
ing from  its  origin  to  its  termination,  and  that  it  represents  a  hollow  cone 
whose  apex  corresponds  to  the  heart. 

Form  of  the  Arteries. — Each  aiterial  tube  affects  a  regularly  cylin- 
drical form,  whatever  its  volume  may  be.  When  the  diameter  of  these 
vessels  is  measured  at  their  origin  and  their  termination,  between  two 
collateral  branches,  no  sensible  difference  is  perceived. 

Mode  of  Origin. — The  arterial  ramifications  are  detached  in  an  angular 
manner  from  the  parent  branches  which  give  them  origin.  Sometimes  the 
angle  of  separation  is  more  or  less  acute — this  is  most  frequently  the  case ; 
sometimes  it  is  at  a  right  angle,  and  at  other  times  it  is  obtuse.  It  will  be 
readily  understood  that  the  opening  of  this  angle  exercises  a  somewhat 
marked  influence  on  the  course  of  the  blood  ;  for  example,  the  blood  from 
a  principal  vessel,  in  passing  into  the  canal  of  a  secondary  one  which  springs 
from  it  at  an  obtuse  angle,  must  experience  a  notable  check  in  its  impetus, 
because  of  the  change  in  direction  it  has  to  encounter ,  on  the  contrary,  the 
rapidity  of  the  current  is  not  modified  to  any  appreciable  degree  in  those 
vessels  which  separate  from  their  trunk  of  origin  at  a  very  acute  angle. 
Towards  the  point  of  separation,  there  is  always  remarked,  in  the  interior  of  the 
vessel,  a  kind  of  spur  whose  sharp  border  is  towards  the  heart,  thus  dividing 
the  current  of  blood  and  diminishing  the  resistance.  This  spur  resembles 
in  its  disposition  the  pier  of  a  bridge,  against  which  the  waters  are  divided 
to  pass  on  each  side.  (When  a  short  trunk  divides  abruptly  into  several 
branches,  proceeding  in  different  directions,  it  is  termed  an  axis.  A  very 
peculiar  feature  in  the  division  of  arteries,  however,  and  one  which  will  be 


516  TEE  ARTEBIES. 

made  amply  conspicuous  in  the  following  description,  is  their  bifurcation  or 
dichotomous  arrangement,  which  prevails  so  largely.) 

Course. — In  the  course  pursued  by  an  artery,  it  is  necessary  to  consider 
the  situation  occupied  by  the  vessel,  its  direction,  relations,  and  the  anastomoses 
which  establish  communication  between  it  and  the  neighbouring  vessels. 

Situation. — The  arteries  tend  constantly  to  recede  from  the  superficial 
parts  :  to  become  lodged  in  the  deep-seated  regions,  and  in  this  way  to  be 
removed  from  the  hurtful  action  of  external  causes,  a  tendency  all  the  more 
marked  as  the  arteries  are  more  considerable  in  volume,  and  which  ceases  to 
be  manifested  in  the  less  important  ramuscules.  These  vessels,  therefore, 
occupy  either  the  great  cavities  of  the  trunk,  or  the  deep  interstices  on  the 
internal  face  of  the  members ;  when  they  pass  over  an  articulation,  it  is 
always  on  the  side  at  which  flexion  occurs.  But  in  the  limbs,  for  instance, 
the  joints  are  flexed  alternately  in  opposite  directions,  and  it  then  happens 
that  the  arteries  in  these  regions  have  a  slightly  helicoid  (or  spiral)  disposi- 
tion. This  is  evident  in  the  case  of  the  femoral  artery,  which  passes  round 
the  inner  face  of  the  femur  to  become  the  popliteal  artery  ;  and  also  in  the 
luuneral  artery,  which  is  at  first  situated  to  the  inner  side  of  the  scapulo- 
humeral articulation,  then  turns  around  the  humerus  to  be  placed  in  front  of 
the  elbow  joint. 

Direction.- — The  arteries  are  sometimes  rectilinear,  and  at  other  times 
more  or  less  flexous.  The  latter  disposition  is  evidently  intended  to  prevent 
the  dilaceration  of  the  vessels  in  organs  susceptible  of  elongation  and  con- 
traction, as  may  be  remarked  in  the  tongue  or  to  moderate  the  impetus  of 
the  blood,  as  in  the  internal  carotid  arteries. 

Belations. — In  their  course,  the  arteries  may  be  in  contact  with  the 
viscera,  nerves,  muscles,  bones,  skin,  and  connective  tissue. 

a.  In  nearly  every  part  of  the  body,  the  arteries  maintain  the  most 
intimate  relations  with  the  veins  :  sometimes  with  two  of  these  vessels,  when 
the  artery  is  placed  between  them  ;  sometimes  with  only  one,  which  is  always 
more  superficial. 

h.  The  arteries  are  usually  accompanied  by  nerves  belonging  to  the 
cerebro-spinal  or  ganglionic  systems.  Those  of  the  latter  category  are 
distinguished  by  the  reticular  interlacing  they  form  around  the  visceral 
arteries  ;  their  structure  will  be  alluded  to  presently. 

c.  Lodged  for  the  most  part  in  the  interstices  of  the  muscles,  the  arteries 
contract  relations  with  these  organs  which  it  is  very  important  to  know  in  a 
surgical  point  of  view.  Some  of  these  muscles  lie  parallel  with  important 
arteries,  and  for  this  reason  have  been  designated  satellite  muscles;  they 
serve  to  guide  the  surgeon  in  searching  for  the  arteries,  by  the  more  or  less 
salient  relief  their  presence  affords  beneath  the  skin. 

It  is  worthy  of  remark  that  the  arteries  are  not  included  in  the  fibrous 
sheaths  enveloping  the  muscles ;  these  vessels  nearly  always  occupy,  with 
the  nerves  which  accompany  them,  special  lodgments  resulting  from  the 
approximation  of  several  aponeurotic  sheaths.  When  they  pass  through 
the  substance  of  a  muscle,  which  sometimes  happens,  they  are  covered 
by  an  arch  or  fibrous  ring,  which  protects  them  from  compression  during 
muscular  contraction :  the  arch  or  ring  receiving  on  its  convexity  the 
insertion  of  fibres  from  the  muscle. 

d.  Nothing  is  more  common  than  to  see  the  arteries  in  direct  contact 
with  the  bones :  as,  for  instance,  the  aorta,  intercostals,  &c.  Neither  is  it 
very  rare  to  find  a  more  or  less  thick  muscular  layer  between  the  arteries 
and  portions  of  the  skeleton.     In  every  case,  a  knowledge  of  the  connections 


(GENERAL  COXSIDERATIONS.  517 

of  the  arteries  with  the  bones  is  important  to  the  surgeon  ;  as  it  enables  him, 
temporarily,  to  interrupt  the  circulation  in  these  vessels  by  exercising  external 
pressure  on  the  points  of  their  coui'se  which  correspond  to  the  several  bones, 
and  thus  diminish  their  calibre  by  flattening  them. 

e.  By  virtue  of  their  deej)  situation,  the  arteries  are,  in  general,  distant 
from  the  skin  ;  there  are,  nevertheless,  some  which  course  immediately  beneath 
the  inner  face  of  that  membrane ;  these  are  only  fomid  about  the  head  and 
in  the  extremities. 

/.  Lastly,  all  the  arteries  are  enveloped  by  a  layer  of  connective  tissue, 
•wliich  forms  around  them  a  kind  of  sheath,  generally  difficult  to  tear  with 
the  fingers  alone,  and  which  isolates  from  the  neighbouring  parts,  but  chiefly 
the  veins.  This  connective  tissue,  more  or  less  abundant  according  to  the 
regions,  is  always  loose  enough  to  allow  the  arteries  to  roll  and  be  displaced 
with  the  greatest  facility,  and  thus  to  glide  away  from  incisive  bodies 
accidentally  introduced  into  the  tissues. 

Anastomosea. — Very  often  the  arterial  branches  are  united  to  each  other  by 
communications,  which  have  received  the  name  of  anastomoses,  and  which 
assure  the  distribution  of  the  blood  in  regulating  its  flow.  There  are 
distinguished : 

1.  Anastomoses  by  convergence  :  formed  by  two  vessels  joining  at  their 
terminal  extremity  in  an  angular  manner,  to  form  a  third  and  more 
voluminous  trunk. 

2.  Anastomoses  hy  arches  or  hy  inosculation :  due  to  the  junction  of  two 
principal  branches,  which  are  inflected  towards  each  other,  meet,  and  unite  to 
form  a  single  and  curvilinear  canal. 

3.  Anastomoses  by  transverse  communication  :  represented  by  ramifications 
thrown  transversely  between  two  parallel  arteries. 

4.  31ixed  or  composite  anastomoses :  in  which  are  found  a  combination  of 
the  different  types  enumerated  above. 

A  knowledge  of  the  anastomoses  of  vessels  is  of  the  highest  practical 
interest ;  as  these  communications  permit  the  surgeon,  in  extreme  cases,  to 
tie  the  principal  artery  of  a  region  without  the  latter  experiencing  any 
considerable  nutritive  disturbance ;  the  blood  continuing  to  arrive  by  the 
collateral  vessels  which,  at  first  very  small,  ■  gradually  dilate  from  the 
excentric  pressure  to  which  their  walls  are  submitted.  But  these  anasto- 
moses, if  they  offer  this  immense  advantage,  have  also  their  inconveniences  : 
we  allude  to  the  difficulties  experienced  in  arresting  hfemorrhage  in  wounds 
of  certain  organs,  owing  to  the  relations  of  the  principal  vessel  with  its 
communicating  collaterals. 

Mode  of  Distribution. — The  branches  an  artery  distributes  in  the 
neighbouring  organs  are  distinguished  as  terminal  and  collateral.  The 
arterial  trunks,  after  finishing  a  certain  course,  divide  into  several  branches — 
nearly  always  two,  which,  as  new  arteries,  continue  the  primary  vessel  and 
take  the  name  of  terminal  branches,  because  they  really  begin  at  the  terminal 
extremity  of  that  vessel. 

The  collateral  vessels  originate  at  various  distances  along  the  course  of 
the  arteries,  and  proceed  in  a  lateral  direction :  these  collateral  branches 
increase  in  number  as  the  arteries  become  more  superficial,  the  ramifications 
being  particularly  abundant  around  the  articulations,  and  in  the  organs  which 
are  prominent  on  the  surface  of  the  body.  This  abundance  of  vessels  is 
intended  to  maintain  a  moderate  temperature  in  those  parts  which,  by  their 
structure  or  situation,  are  exposed  to  sudden  chills. 

The  distinction  between  the  terminal  and  collateral  branches  of  arteries 
36 


518 


THE  ARTERIES. 


is  not  always  easy  to  establish,  and  is  far  from  having  an  absolute  value  ;  it 
possesses,  nevertheless,  some  importance,  as  it  greatly  facilitates  description. 
Termination.— The  arteries  terminate  in  the  substance  of  the  tissues 
by  extremely  fine  and  numerous  ramuscules,  which  so  frequently  anastomose 
with  each  other  as  to  form  a  plexus  or  microscopical  network,  whose  meshes 


Fig.  266. 


WEB    OF    FROCi'S   FOOT    STRETCHING     BETWEEN    TWO    TOES,   SHOWING    THE   BLOOD- 
VESSELS  AND   THEIR    ANASTOMOSES. 

a,  a,  Veins ;  6,  6,  b,  Arteries,  the  capillaries  being  between. 


Fiff.  267. 


are  very  close.  These  ramuscules  constitute  the  capillanj  system,  which 
again  gives  rise  to  ramifications  of  gradually  increasing  size,  the  veins. 
The  capillary  system  is,  therefore,  nothing  more  than 
a  network  of  microscopical  canals  intermediate  to  the 
arteries  and  veins. 

In  the  erectile  tissues,  the  mode  of  tefmination  is 
different :  the  small  arteries  sometimes  opening  directly 
into  the  cells  placed  at  the  origin  of  the  veins,  without 
jjassing  through  a  capillary  plexus.  In  describing  the 
genital  organs  we  shall  notice,  in  detail,  the  termination 
of  the  arteries  in  the  cavernous  tissues. 

Structure. — The  walls  of  arteries  offer  a  certain 
rigidity,  which  permits  tliese  vessels  to  remain  open 
when  they  are  emptied  of  blood.  The  ancients  believed 
this  was  their  normal  condition,  and  that  they  were 
filled  with  air  during  life.  This  was  a  grave  error,  as 
a  perfect  vacuum  exists  throughout  tlie  entire  circulatory 
system.  The  gaping  of  the  arteries  mtist  be  attributed 
solely  to  the  physical  properties  of  their  walls. 

These  wails  comi>rise  three  superposed  tunics :  an 
internal,  middle,  and  external. 

The  internal  tunic  is  continuous  with  the  endocardium  of  the  left  heart 


EPITHELIAL   CELLS    OF 
BLOOD-VESSELS. 

a,  b,  From  a  vein ;  c, 
From  an  artery, 
Magnified  350  dia- 
meters. 


GENERAL  CONSIDERATIONS. 


519 


Fig. 


Fig.  270. 


FENESTRATED  MEMBRANE 
FROM  THE  CAROTID 
ARTERY  OF  THE  HORSE. 

Magnified    350    diame- 
ters. 


Fig.  269. 


on  the  one  part,  and  on  the  other  with  the  capillaries  and  veins.  For  a 
long  time  it  has  been  assimilated  to  a  serous  membrane,  but  it  has  not 
absolutely  the  same  texture.  It  is  composed  of  a  simple  epithelial  layer 
which  is  in  contact  with  the  blood,  and  is  formed  by  fusiform  cells  that 
slightly  bulge  in  the  situation  of  their  nucleus. 
These  cells  sometimes  become  detached,  and  are 
carried  about  in  the  nutritive  fluid,  in  Avhich,  after  a 
certain  period,  they  resemble 
more  or  less  mis-shapen  blood- 
globules.  The  epithelium  lies 
upon  a  layer  of  amorphous 
elastic  tissue,  perforated  by 
openings,  and  named  the  fene- 
strated membrane ;  on  its  ex- 
ternal face  are  proper  elastic 
fibres  passing  in  a  longitudinal 
direction. 

The  middle  tunic  is  remark- 
able for  its  thickness,  its  elas- 
ticity, and  the  yellow  colour  it 
offers  in  the  principal  vessels. 
It  is  composed  of  a  mixture  of  elastic  fibres,  as  well  as 
smooth  muscular  fibres,  the  first  constituting  a  kind  of 
network,  in  the  meshes  of  which  the  contractile  fibres 
are  disposed  in  a  circular  manner  around  the  vessels. 
The  proportion  of  these  two 
elements  varies  with  the  size 
and  situation  of  the  artery. 
In  the  large  trunks,  such  as 
the  aorta,  the  elastic  is  more 
abundant  than  the  contractile  ; 
in  the  middle-sized  vessels 
they  are  about  equal ;  but  in 
the  small  arteries,  in  which 
the  contractile  force  of  the 
heart  is  lost  because  of  their 
distance  from  it,  the  muscular 
fibres  almost  exclusively  com- 
pose the  middle  tunic. 

The  external  tunic  is  only 
a  layer  of  connective  tissue, 
with  some  longitudinal  reticu- 
lated elastic  fibres  in  its  deeper 
part.  Though  this  tunic  is 
very  thin,  yet  it  is  strong  ;  as 
Jirgnified  35o"dYame-  a  ligature  tied  tightly  around  an  artery  will  rupture 
ters!  the  other  tunics,  but  not  this. 

The  structure  of  the  capillaries  is  not  the  same 
as  that  just  described,  but  is  modified  in  proportion  as  they  are  fine.  In 
the  smallest  capillaries,  the  walls  are  formed  by  a  thin  amorphous  mem- 
brane, in  which  (oblong)  nuclei  are  somewhat  regularly  disseminated ;  in 
medium-sized  vessels,  another  layer  containing  transverse  nuclei  is  observed  ; 
and   in   the  largest  capillaries — those  immediately   succeeding   the  small 


OP  COARSE 
TISSUE  FROM 
MIDDLE  COAT  OF  PUL- 
MONARY ARTERY  OF 
THE  HORSE,  THE  FIBRES 
BEING  PIERCED  WITH 
■  CIRCULAR         OPENINGS. 


TRANSITION  OF  A  MINUTE 
ARTERY  OF  THE  BRAIN 
TNTO  CAPILLARY  VES- 
SELS. 

1,  Minute  artery;  2, Tran- 
sitional capillary ;  3, 
Coarse  capillary  with 
thick  coat,  represented 
by  a  double  contour 
line;  4,  Fine  capillary, 
with  single  contour. 
The  nuclei  are  seen 
widely  scattered  in  4- 
and  3  ;  more  closely  con- 
gregated in  2  ;  and  still 
more  so  in  1,  where  they 
form  an  epithelium. — a, 
Transverse  elongated 
nuclei  of  muscular  cells, 
the  inci]iient  muscular 
coat  of  the  artery. 


520  THE  ARTERIES. 

arteries,  these  two  nucleated  layers  are  enveloped  by  a  thin  tunic  of  con- 
nective tissue. 

(Some  authorities  state  that  the  walls  of  the  very  finest  capillaries  ai'e 
merely  composed  of  closely-adhering  cells,  without  any  basement  membrane, 
which  only  becomes  apparent  in  tubes  of  a  large  diameter.) 

Vessels  and  nerves — Tlie  arteries  are  provided  with  vessels  termed  vasa 
lasorum,  which  are  furnished  either  by  the  arteries  themselves,  or  by  ueigh- 
bouring  vessels.  These  vasa  vasorum  form  a  superheial  network  witli  quad- 
rilateral meshes,  and  a  deep  plexus  whose  principal  branches  are  helicoidal. 
The  majority  of  anatomists  believe  that  this  plexus  does  not  extend  beyond 
the  external  tunic. 

The  lymphatic  vessels  maintain  intimate  relations,  in  certain  regions, 
with  the  capillaries.  In  the  brain  and  spleen  there  has  been  discovered, 
around  the  arterial  caiiillaries.  a  vessel  that  completely  envelops  them, 
and  which  has  been  named  the  lymphatic  sheath. 

The  nerves,  designated  vasa  motors,  accompany  the  vessels  and  penetrate 
the  muscular  tunic,  for  which  they  are  naturally  destined.  These  vaso- 
motor filaments  join  the  branches  of  the  capillary  plexuses,  and  form,  at  the 
points  where  they  meet  each  other,  ganglionic  enlargements,  from  which  arise 
the  fibres  of  Remak,  the  termination  of  which  is  unknown. 

Anomalies  in  the  Arteries. — In  their  arrangement,  the  arteries  very 
often  present  anomalies  which  the  surgeon  should  be  guarded  ag-ainst. 
These  usually  belong  to  their  number,  their  point  of  origin,  and  their 
volume.  In  a  purely  anatomical  and  jjliysiological  point  of  view,  however, 
these  anomalies  are  of  no  moment ;  as  it  matters  little  whether  the  blood 
comes  from  one  source  rather  than  another,  or  that  a  collateral  vessel  be- 
comes the  principal  at  the  expense  of  the  parent  trunk,  provided  its  rela- 
tions are  not  altered,  and  the  principle  of  immutability  of  connections  is 
maintained. 

Preparation  of  the  Arteries. — This  requires  two  successive  operations:  1,  In- 
jection; 2,  Dissection. 

Injection  of  the  arteries. — The  object  to  be  attained  in  injecting  these  vessels,  is  to 
introduce  into  their  interior  a  solidifiable  substance  whicli  •will  cause  them  to  assiune  the 
volume  and  conformation  they  presented  during  life,  when  they  are  filled  witii  blood. 

Tallow,  coloured  by  lamp-black,  is  the  most  convenient  and  gL-nera'i  injecting  mate- 
rial. Sometimes  a  solution  of  gelatine,  with  the  addiiion  of  a  certain  quantity  of  plaster 
of  Paris,  is  used  ;  but  this  is  seldom  employed  in  the  French  schools.  A  copper  or 
brass  syringe,  and  a  canula  with  a  stop-cock  to  fit  on  its  extremit}%  are  the  only  instru- 
ments necessary  to  propel  these  mutters  into  tlie  arteries. 

The  following  are  the  details  of  the  operation,  when  it  is  desired  to  make  a  general 
injection: — -The  animal  being  placed  on  a  table,  the  carotid  artery  is  exposed  by  iin 
incision  in  the  jugular  cliannel,  and  opened  longitudinally.  A  ligature  is  applied  above 
the  opening,  and  the  tube,  with  the  stop-cock,  is  firmly  fixed  in  the  cavity  of  the 
artery  towards  the  heart  by  a  second  ligature.  The  injection,  previously  prepared,  is 
tuken  up  by  the  syringe,  which  is  fitted  into  the  tube,  and  the  piston  pushed,  in  order 
to  drive  the  contents  of  the  instrument  into  the  arterial  canals. 

To  perform  the  operation  successfully,  the  following  precautions  are  to  be  attended 
to:  1.  Inject  the  vessels  of  an  animal  killed  by  eft'usion  of  blood,  and  yet  warm.  2.  If 
suet  is  employed,  and  which  is  always  to  be  reconunended,  make  it  so  hot  that  the  finger 
can  scarcely  endure  it.  When  it  is  colder  than  this  it  solidifies  too  quickly,  and  when 
liotter  it  shrivels  up  the  sigmoid  valves,  passes  into  the  left  ventricle,  and  from  thence 
into  the  auricle  and  pulmonary  veins;  an  accident  generally  attributed  to  the  tOD  power- 
ful force  applied  to  the  piston  of  the  syringe.  3.  Do  not  make  any  undue  pressure  on 
the  piston,  though  this  does  not  strain  the  sigmoid  valves  so  frequently  as  is  believed. 
4.  Cease  injecting  when  the  arteries  react,  by  their  elasticity,  on  the  piston,  so  as  to 
drive  it  back  in  the  syringe. 

In  order  to  insure  the  retention  of  the  injected  matter  in  the  arteries,  and  prevent 
the  sigmoid  valves  being  forced    a  cork  may  be  intioduced  into  the  aoita  througu  the 


PULMONARY  ARTERY.  521 

left  ventricle,  and  firmly  tied  there  by  a  strong  ligature  ;  the  cork  should  have  a  traiis- 
verse  notch  for  the  reception  of  the  liirature. 

In.itead  of  injecting  by  the  carotid,  a  long  curved  canula  may  be  fixed  to  the  aorta 
itself,  after  making  an  opening'  in  the  left  side  of  the  chest,  on  a  level  with  the  heart, 
by  the  ablation  of  two  segments  of  the  ribs,  and  incising  the  pericaiilium  and  left 
auricle  to  introduce  it.  This  mode  allows  the  tallow  to  be  injected  at  a  very  high 
temperature,  and  gives  tlie  best  results,  lor  it  can  then  penetrate  to  the  capillaries,  if  we 
only  know  how  to  manage  it ;  in  certain  organs  the  injected  matter  may  even  be  made 
to  return  by  the  veins. 

But  no  matter  what  procedure  may  be  adopted,  there  are  several  parts  into  which 
the  tallow  can  never  be  made  to  enter  by  a  general  injection  •  these  are  the  four  extre- 
mities. So  that  a  special  operation  must  be  resorted  to,  in  order  to  fill  their  vessels. 
After  separating  theur  from  the  trunk,  by  sawing  them  through  ahove  the  knees  and 
hocks,  they  should  be  allowed  to  steep  for  two  hours  in  water,  con.stantly  kept  up  to  a 
temperature  of  140^  to  I(3U'^  Fahr.  at  most ;  it  is  then  easy  to  inject  them,  either  by  the 
posterior  radial  artery,  or  the  a"terior  tibia!,  alter  tying  those  branches  wiiich  may  be 
open  at  the  cut  extremity  of  the  limbs. 

If  it  is  desired  to  make  partial  injections  in  other  parts  of  the  body,  it  will  be  better 
not  to  separate  them  from  tlie  trunk ;  but  only  to  tie  those  vessels  which  anastomose 
between  the  arteries  to  he  filled  and  those  which  are  not.  For  example,  to  inject  the 
arteries  of  the  head,  it  suffices  to  push  the  mixture  into  one  of  the  common  carotids, 
after  ligaturing  the  other  in  the  middle  of  the  neck,  and  both  vertebrals  in  the  space 
between  the  two  portions  of  the  scalenus  muscle. 

We  may  give  ilie  tallow  more  fluidity,  and  a  higher  degree  of  penetration,  by  mixing 
with  it  a  little  spirits  of  turpentine  ;  or  more  consistence,  in  adding  to  it  a  small  proportion 
of  beeswax. 

The  two  following  mixtures  are  borrowed  from  Cruveilhier's  Anatomy  : — 

Tallow 9  parts 

Turpentine 1     .? 

Ivory  Black,  mixed  with  spirits  of  turpentine  .     2     „ 

For  preservative  injections  : — 

Beeswax 1  part 

Tallow 3    „ 

Vermilion,  indigo,  or  Prussian  blue,  previously 

mixed  in  spirits  of  turpentine A  sufficient  quantity. 

Of  course  it  is  well  understood  that  these  instructions  are  only  intended  for  the 
diss -cting-room  injections  necessary  for  the  study  of  descriptive  anatomy.  To  inject  the 
capillaries,  it  is  requisite  to  have  recourse  to  other  substances  and  other  procedures. 
Sutfice  it  to  say  that  these  injections  are  made  with  cold  fluids,  such  as  varnish,  alcohol, 
or  spirits  of  turpentine,  holding  in  suspension  extremely  fine  colouring  matter,  gum  arable 
dissolved  and  coloured  by  a  substance  also  in  solution,  etc.,  or,  better  still,  colours 
rubbed  up  in  oil,  and  mixed  with  spirits  of  turpentine. 

Dissection  of  the  arteries. — There  are  no  general  rules  to  be  given  for  the  dissection 
of  arteries. 


CHAPTER  II. 

PULMONARY   ARTERY    (Fig.  258,  e). 

Preparation. — The  pulmonary  artery  is  not  filled  by  the  general  injection  mentioned 
above.  It  is  directly  injected  by  propelling  the  tallow  into  the  right  heart  by  the 
anterior  vena  cava,  after  tying  the  posterior  vena  cava. 

The  pulmonari/  artery  springs  from  the  infunflibulum  of  the  right 
ventricle,  is  directed  upwards  and  then  backwards,  describing  a  curve  whose 
concavity  is  infero-posterior,  and  arrives  above  the  left  auricle,  where  it 
divides  into  two  secondary  arteries,  one  for  each  lung.  These  arteries 
enter  the  pulmonary  tissue  with  the  bronchi,  and  exclusively  ramify  in  it. 

The  pulmonary  artery  accompanies  the  trunk  of  the  aorta  on  the  right 
side,  and  is  enveloped  with  it  in  a  serous  sheath,  a  dependency  of  the  visceral 
layer  of  the  pericardium.     At  its  origin,  it  is  flanked  before  and  behind  by 


522  THE  ARTERIES. 

the  appendages  of  the  auricles  and  the  cardiac  yessels.  About  the  middle 
of  its  coui'se,  it  is  united  to  the  posterior  aorta  by  means  of  a  yellow  elastic 
fibrous  cord  (the  ligamentmn  arteriosum),  the  remains  of  the  ductus  arteriosus 
wliich,  in  the  foetus,  establishes  a  large  communication  between  these  two 
vessels  (Fig.  258,  e). 

The  walls  of  the  pulmonary  artery  are  much  thinner  than  those  of  the 
aorta,  and  are  yellow  and  elastic,  as  in  the  other  canals  of  the  same  order. 
We  remember,  however,  having  seen  them  in  an  Ass,  formed  almost  entirely 
of  red  muscular  fibres,  analogous  to  the  fiisciculi  of  the  heart. 

It  may  be  repeated  that  the  pulmonary  artery  conveys  into  the  lungs 
the  dark  blood  carried  to  the  right  heart  by  the  veins  of  the  general 
circulation. ' 


CHAPTER  III. 

THE  AORTA. 

If  we  take  a  general  survey  of  the  aortic  trunk,  we  will  find  tliat  it  arises 
from  the  base  of  the  left  ventricle,  ascends  to  beneath  the  dorso-lumbar 
column,  curving  backwards  and  downwards,  and  reaches  the  entrance  to  the 
pelvis,  where  it  terminates  by  four  branches.  It  furnishes,  besides,  about 
2  to  2|-  inches  from  its  origin,  a  secondary  trunk,  which  soon  divides  into 
two  new  arteries,  the  right  and  largest  of  which  gives  off  a  particular 
trunk,  the  common  origin  of  the  two  long  vessels  destined  for  the  head. 

This  disposition  permits  us  to  recognise  in  the  aorta  seven  principal 
sections : 

1.  The  aortic  trunh  or  common  aorta :  the  source  of  all  the  arteries 
belonging  to  the  red-blood  system,  and  giving  rise  to  the  anterior  and 
posterior  aorta.     It  only  furnishes  blood  directly  to  the  heart  itself. 

2.  The  posterior  aorta :  the  veritable  continuation  of  the  (common  aorta, 
is  distributed  to  the  posterior  moiety  of  the  trunk  and  to  the  abdominal 
limbs ;    it  terminates  by  a  double  bifurcation. 

3.  The  internal  and,  4,  external  iliac  arteries:  branches  of  this  bifuraxtiou 
which  are  almost  entirely  expended  in  the  posterior  limbs. 

5.  The  anterior  aorta:  the  smallest  of  the  two  trunks  furnished  by  the 
common  aorta,  is  chiefly  destined  to  the  anterior  moiety  of  the  trunk  and 
the  thoracic  limbs. 

6.  The  axillary  arteries,  ov  brachial  trnnlcs:  these  come  from  the  bifurca- 
tion of  the  preceding  artery,  and  aie  continued  by  their  terminal  extremity 
into  the  fore-limbs. 

7.  The  carotid  arteries,  or  arteries  of  the  head  :  these  emanate  by  a 
common  trunk  from  the  right  brachial  bifurcation. 

Article  I, — Aortic  Trunk  or  Common  Aorta. 

The  point  of  departure  for  all  the  arteries  carrying  red  blood,  the  aortic 
trunk  proceeds  from  the  left  ventricle  by  becoming  continuous  with  the 
festooned  fibrous  zone  which  circumscribes  the  arterial  orifice  of  that 
cavity.  It  passes  upwards  and  a  little  forwards,  bifurcating,  after  a 
course  of  2  or  2-i  inches,  into  the  anterior  and  posterior  aortse. 

Its  volume,  mferior  to  that  of  its  two  terminal  branches,  is  not  uniform  ; 
as  at  its  origin,  and  opposite  the  sigmoid  valves,  it  presents  (an  enlargement 
— the  hulhus  aortse — caused  by)  three  dilatations  described  as  the  sinus  of 
the  aorta  {sinus  aortici,  sinus  Valsalvse). 


TEE  POSTERIOR  AORTA.  623 

Included,  on  the  right  side,  in  the  crescent  formed  by  the  auricular 
mass ;  in  relation,  on  the  left  side,  with  the  pulmonary  artery,  which 
is  joined  to  it  by  means  of  cellulo-adipose  tissue  traversed  by  the 
cardiac  nerves,  the  common  aorta  forms,  with  tlie  latter  artery,  a 
fasciculus  enveloped  by  the  visceral  layer  of  the  i^ericardium,  which  is 
reflected  as  a  sheath  around  these  two  vessels. 

Two  collateral  arteries  are  given  off  directly  from  the  aortic  trunk:  these 
are  the  cardiac  or  coronary  arteries. 

Cardiac  or  Coronary  Arteries.    (Figs.  258,  259.) 

There  are  two  cardiac  arteries,  a  right  and  left,  exclusively  destined  for 
the  tissue  of  the  heart. 

Right  Cardiac  Arteky  (Figs.  258,  259,  l). — This  originates  from 
the  front  and  to  the  right  of  the  aorta,  at  the  free  margin  of  the  sigmoid 
valves,  and  proceeds  perpendicularly,  or  at  a  right  angle,  from  the  trunk, 
passing  forwards  to  the  right  of  the  pulmonary  artery,  beneath  the  anterior 
auricle  ;  then  to  the  right  and  backwards,  to  reach  the  aiiriculo- ventricular 
groove,  which  it  follows  till  near  the  origin  of  the  right  ventricular  furrow. 
Here  it  divides  into  two  branches :  one  vertical,  descending  in  this  furrow 
to  the  apex  of  the  heart,  which  it  bends  round  to  the  front,  and  anastomoses 
with  an  analogous  branch  of  the  left  coronary  artery  ;  the  other  is  horizontal, 
is  smaller  than  the  first,  aud  follows  the  primitive  course  of  the  artery 
in  the  auriculo-ventricular  gi'oove,  also  inosculating  with  the  artery  of  the 
left  side. 

Left  Cardiac  Artery  (Fig.  258,  2). — This  arises  opposite  the  pre- 
ceding, at  the  same  angle  of  incidence,  passes  behind  the  pulmonary  artery, 
and  divides,  under  the  left  or  posterior  auricle,  into  two  branches  similar 
in  every  respect  to  those  of  the  right  artery.  The  vertical  branch  descends 
in  the  left  perpendicular  furrow ;  the  horizontal  is  lodged  in  the  coronary 
groove  ;  aud  both  anastomose  with  the  analogous  branches  of  the  opposite 
vessel. 

From  this  arrangement,  it  results  that  the  heart  is  surrounded  by  two 
arterial  circles  :  a  vertical,  or  ventricular,  which  has  been  compared  to  a 
meridian ;  and  a  horizontal,  or  auriculo-ventricular,  analogous  to  an 
equatorial  circle. 

In  tlieir  course,  which  is  more  or  less  tortuous,  the  coronary  arteries 
throw  out  a  considerable  number  of  ramuscules,  which  enter  the  muscular 
tissue  of  the  heart.  The  vertical  circle  gives  off  branches  which  are 
entirely  ventricular ;  while  from  the  horizontal  circle  come  the  superior  or 
auricular,  and  inferior  or  ventricular  branches.  Among  the  latter  there  is 
one  which,  rising  from  the  right  artery  where  it  bends  at  an  angle  beneath 
the  auricle,  enters  the  substance  of  the  right  ventricle  by  passing  round 
the  pulmonary  infundibulum ;  its  ramifications  anastomose  with  those  of  a 
similar  branch  from  the  left  artery,  and  in  this  way  establish  another  com- 
munication between  the  two  vessels. 

Article  II. — Posterior  Aorta. 

Cuurse.^This  artery  is  a  continuation  of  the  aortic  trunk,  which  it 
neai'ly  equals  in  volume,  and  from  which  it  passes  upwards  and  backwards, 
describing  a  curve  whose  convexity  is  antero-superior,  and  which  is  known 
as  the  arch  of  the  aorta.  It  thus  reaches  tlie  left  side  of  the  inferior  face  of 
the  spine,  about  the  8e>^nth  dorsal  vertebra,  behind  the  posterior  extremity 
of  the  longus  coUi  muscle,  and  is  then  carried  directly  backwards,  following 


524  THE  ARTERIES. 

the  vertebral  bodies,  though  a  little  to  the  left  at  first ;  it  gradually  incliues 
to  the  right,  however,  and  reaches  the  median  plane  at  the  pillars  of  the 
diaphragm.  Here  it  passes  through  the  opening  circumscribed  by  these 
two  pillars,  enters  the  abdominal  cavity,  and  extends  to  the  entrance  of  the 
pelvis,  under  the  spine,  still  preserving  its  median  position.  On  reaching 
the  last  intervertebral  articulation,  the  posterior  aorta  tei'minates  by  a 
double  bifurcation,  from  which  arises  the  external  and  internal  iliac  arteries. 

Helations. — To  facilitate  the  study  of  its  connections,  tlie  posterior  aorta 
may  be  divided  into  two  sections  :  one  thoracic,  the  other  abdominal. 

a.  At  its  origin  or  arch,  the  thoracic  aorta  is  crossed  to  the  right  by  the 
trachea  and  oesophagus ;  on  the  opposite  side,  it  responds  to  the  pulmonary 
artery  and  the  left  lung.  For  the  remainder  of  its  extent,  it  is  comprised 
between  the  two  layers  of  the  jjosterior  mediastinum,  and  through  these 
is  in  relation  with  the  jmlmonary  lobes,  which  are  fissured  for  its  reception ; 
this  fissure  is  much  deeper  in  the  left  than  the  right  lung.  Above,  it  is 
ill  contact  with  the  bodies  of  the  last  twelve  dorsal  vertebrae,  and  is 
accompanied  on  the  right  by  the  large  vena  azygos  and  tlie  tlioracic  duct ; 
the  latter  is  often  carried  to  the  left  for  the  whole  or  a  j^ortion  of  its  extent. 

(Remak  observed  muscular  fibres  on  the  external  face  of  the  aortic 
arch  and  thoracic  aorta  in  the  Horse,  Sheep,  and  Pig  ;  the  fasciculi  they  form 
are  so  large  as  to  be  visible  to  the  naked  eye.) 

h.  The  abdominal  aorta,  enlaced  by  the  abdominal  nerves  of  the  great 
sympathetic,  corresponds,  above,  with  the  bodies  of  the  lumbar  vertebrje, 
the  originating  tendon  of  the  diaphragmatic  pillars,  Pecquet's  reservoir.,  and 
the  common  inferior  vertebral  ligament ;  it  passes  above  the  pancreas  and 
the  peritoneum,  the  latter  by  its  sublumbar  layer  covering  the  posterior 
two- thirds  of  the  vessel.  On  the  right,  it  is  accompanied  by  the  posterior 
vena  cava,  which  perhaps  it  slightly  pushes  to  the  left  of  the  median  plane. 

Collateral  branches. — The  arteries  emanating  from  the  posterior  aorta 
during  its  long  course,  very  naturally  form  two  classes;  some  are  desig- 
nated parietal,  because  they  are  distributed  to  the  jiarietes  of  the  great 
splanchnic  cavities;  the  others  are  the  visceral  branches,  destined  for  the 
organs  lodged  in  these  cavities. 

Among  the  parietal  branches,  may  be  noticed  : 

1.  The  intercostal  arteries,  furnished  by  the  thoracic  aorta. 

2.  The  diaghragmatic  arteries,  whose  origin  is  j)laced  on  the  limits  of  the 
two  portions  of  the  vessel. 

3.  The  lumbar  arteries,  and  the  middle  sacral  artery,  springing  from  the 
abdominal  aorta. 

The  visceral  branches  are  : 

1.  The  broncho- oesophageal  <?•«?»/«,  emitted  by  the  thoracic  portion  of  the 
aorta. 

2.  The  coeliac  trunk,  great  mesenteric  artery,  small  mesenteric  artery,  renal 
arteries,  spermatic  arteries,  and  small  testicular  or  uterine  arteries,  which 
emerge  from  the  abdominal  jjortion. 

Preparation  of  the  posterior  aorta  and  Us  collateral  branches. — Tnimediately  after 
injecting  according  to  one  of  the  modes  recommended  at  p.  519,  place  the  subject  iix 
the  first  position,  the  two  posterior  members  being  well  extended  backwards.  Open  the 
Hbdominal  cavity,  and  remove  from  it  the  intestines  in  the  manner  already  indicated. 
The  tallow  liaving  become  perfectly  solidified  during  these  necessary  manipulations, 
dissection  may  be  proceeded  with  at  once.  It  is  requisite,  however,  to  remove  the  light 
and  left  walls  of  the  thoracic  cavity  beforehand,  by  sawing  through  the  last  fourteen  or 
fifteen  ribs  at  tix  or  seven  inches  from  their  sujierior  extren^ity,  and  aftei'wards  sepa- 
rating them  from  the  sternum  by  the  saw,  taking  the  precaulion  of  detaching  the  peri- 


THE  POSTERIOR  AORTA.  525 

phcral  insertion  of  the  diaphragm.  It  is  recommended  to  prepare,  from  before  to  behind, 
tlie  various  visceral  braui.hes  of  the  vessel ;  tirst,  the  broncho-ccsoplmgeal  trunk,  then 
the  ccjeliac  trunk,  next,  the  great  mesenteric  artery  and  the  renal  arteries,  after  spreading 
out  the  intestinal  mass  as  in  figure  271 ;  and.  lastly,  the  small  mesenteric  and  testicular 
arteries,  alter  arranging  the  intestines  as  in  figure  272. 

PAUIETAL   BRANCHES    OF    THE    POSTERIOR    AORTA. 

1.  Intercostal  Arteries.     (Fig.  237.) 

The  intercostal  arteries,  placed,  as  their  name  indicates,  in  the  intervals 
of  the  ribs,  number  seventeen  pairs. 

Origin,  Course,  and  Distribution. — The  last  thirteen  emanate  from  the 
thoracic  aorta  only ;  the  first  comes  from  the  cervical  artery ;  and  the  next 
three  are  furnished  by  a  special  branch  of  the  dorsal  artery. 

The  aortic  intercostals  escape  at  a  right  angle  from  the  superior  plane 
of  the  trunk,  on  a  level  with  the  bodies  C)f  the  dorsal  vertebrae,  and  at 
regular  intervals.  Their  origin  is  nearer  that  of  the  arteries  on  the 
opposite  side  as  they  are  more  anterior,  the  first  two  or  three  arising  in  pairs 
from  a  common  trunk. 

These  aortic  intercostals  ascend  to  the  vertebral  bodies,  beneath  the 
pleura,  in  crossing  the  direction  of  the  sympathetic  nervous  chain  and  (the 
arteries  of  the  right  side  only),  in  addition,  that  of  the  vena  azygos  and 
the  thoracic  duct,  to  the  superior  extremity  of  the  intercostal  spaces,  where 
those  of  both  sides  divide  into  two  branches :  the  one  inferior,  or  proper 
intercostal ;  the  other  superior,  or  dorso-spinal. 

The  inferior  and  superior  branches  of  the  first  four  intercostal  arteries 
emanate  solely  from  the  trunk  which  furnishes  them,  and  which  is  the 
superior  cervical  artery  for  the  first  intercostal,  and  the  subcostal  branch 
of  the  dorsal  artery  for  the  succeeding  three. 

Inferior  or  intercostal  branch. — This  branch,  the  most  considerable  of 
the  two,  placed  at  first  beneath  the  2:)leura,  then  between  the  two  intercostal 
muscles,  is  lodged,  along  with  a  satellite  vein  and  nerve,  in  the  furrow  on 
the  posterior  face  of  the  rib,  and  descends  to  the  inferior  extremity  of  the 
intercostal  space,  where  it  terminates  in  the  following  manner  :  the  first 
twelve  or  thirteen  branches  anastomose  with  the  intercostal  ramifications 
of  the  internal  thoracic  artery  and  its  asternal  branch  ;  the  others  are 
prolonged  into  the  abdominal  muscles,  where  their  divisions  communicate 
with  those  of  the  anterior  and  posterior  abdominal  arteries,  as  well  as  with 
the  circumflex  iliac. 

In  their  course,  these  intercostal  branches  give  arterioles  to  the  pleurae, 
the  ribs,  and  the  thoracic  muscles,  with  the  perforating  ramuscules  which 
cross  these  muscles  to  ramify  in  the  skin  and  the  panniculus  carnosus,  but 
which,  of  course,  are  absent  where  the  pectoral  wall  is  covered  by  the  thoracic 
limb. 

Superior  or  dorso-spinal  branch. — This  passes  directly  upwards  to  be 
distributed  to  the  spinal  muscles  of  the  dorsal  region  and  the  integument 
covering  them,  after  giving  ofi",  when  passing  the  intervertebral  foramen,  a 
branch  which  enters  the  spinal  canal  by  that  opening,  and  is  destined  for  the 
spinal  cord  and  its  envelopes.  An  auxiliary  of  the  middle  spinal  artery, 
this  branch  will  be  studied  at  greater  length  when  the  cerebro-spinal  artery 
comes  to  be  described. 

Variations  in  origin.^Not  unfrequently  the  first  two  pairs  of  aortic 
intercostal  arteries  proceed  from  a  single  trunk,  w-hich  thus  gives  rise  to 
four  branches ;  and  this  trunk  is  also  often  the  common  source  of  these  four 


520  THE  ARTERIES. 

intercostals  and  the  bi-onchial  and  oesophageal  arteries,  when  its  volume  is 
very  considerable.  It  is  much  smaller  when  it  only  gives  off  the  second 
pair  of  intercostals,  which  is  sometimes  the  case. 

2.  Lumbar  Arteries. 

These  are  five  or  six  in  number,  and  do  not  differ  in  their  general 
arrangement  from  the  intercostal  arteries ;  they  having  the  same  mode  of 
origin,  the  same  division  into  two  branches,  and  the  same  distribution.  The 
superior,  or  lumho-sjnnal  branch,  is  much  larger  than  the  inferior,  and  goes  to 
the  muscles  and  integuments  of  the  lumbar  region  ;  it  also  furnishes  a 
branch  to  the  spinal  cord.  The  inferior  branch  passes  above  the  large  and 
small  psoas  muscles,  giving  them  numerous  twigs,  and  extending  to  the 
muscular  portions  of  the  transverse  and  small  oblique  abdominal  muscles, 
where  their  ramifications  anastomose  with  those  of  the  circumflex  iliac 
artery. 

The  last,  and  sometimes  also  the  second-last  lumbar  artery,  arises  from 
the  internal  iliac  trunk  ;  the  others  emerge  directly  from  the  abdominal 
aorta. 

3.  Diaphragmatic  (^or  Phrenic)  Arteries. 

These  are  two  or  three  small  vessels  which  spring  from  the  aorta  as  it 
passes  between  the  two  pillars  of  the  diaphragm,  and  are  destined  for  that 
muscle.  The  left  pillar  receives  a  very  insignificant  branch  ;  but  the  right 
has  two,  the  most  considerable  of  which  is  alone  constant ;  it  sometimes  sends 
subpleural  ramuscules  to  the  right  lung. 

4.  Middle  Sacral  (Sacra  Media)  Artery. 

This  vessel  is  often  absent,  and  when  it  exists  is  very  variable  in  size, 
though  always  extremely  slender.  It  arises  from  the  terminal  extremity  of 
the  aorta,  in  the  re-entering  angle  comprised  between  the  two  internal  iliac 
arteries,  and  is  carried  to  the  inferior  fixce  of  the  sacrum,  where  it  is. 
expended  in  lateral  ramifications  which  go  to  the  periosteum.  It  has  been 
thought  necessary  to  notice  this  artery,  as  it  attains  a  considerable  volume 
in  Man  and  some  animals,  and  continues  the  aortic  tree  beneath  the  sacral 
portion  of  the  vertebral  column. 

VISCERAL   BRANCHES    OF    THE    POSTERIOR    AORTA. 

1.  Broncho-cesophageal  Trunk. 

Destined  for  the  lung,  the  visceral  pleura,  the  mediastinum,  and  the 
oesophagus,  this  artery  arises,  not,  as  is  generally  said,  in  the  concavity  of 
the  arch  of  the  aorta,  but  opposite  to  it,  and  very  near,  but  to  the  right 
of,  the  first  pair  of  intercostals ;  often  even  in  common  with  these  arteries 
and  with  the  second  pair.^  After  leaving  the  aorta,  it  insinuates  itself 
between  that  trunk  and  the  oesophagus,  and  above  the  bifurcation  of  the 
trachea  divides  into  branches,  the  bronchial  arteries.  In  its  short  course,  it 
gives  off  the  two  oesophageal  arteries  and  a  certain  number  of  innominate 
ramuscules. 

Bronchial  Arteries. — The  disposition  of  these  two  vessels  is  extremely 
simple  ;  they  enter  the  lung  with  the  bronchi,  one  to  the  right,  the  other  to 
the  left,  and  there  break  up  into  arborescent  ramifications  which  follow  the 
air-tubes  to  the  pulmonary  lobules. 

CEsophageal  Arteries. — These  two  arteries  are  placed  in  the  posterior 
'  See  Intercostals. 


THE  POSTERIOR  AORTA.  527 

mediastinum,  one  above,  the  otbei-  below  the  oesophagus,  which  they  accompany 
for  a  short  distance,  from  before  to  behind,  to  the  extremity  of  that  canal. 

The  superior  oesophageal  artery,  much  more  voluminous  than  the  inferior, 
inosculates  with  a  branch  of  the  gastric  artery.  In  its  course  it  gives  descend- 
ing branches  to  the  oesophagus,  and  ascending  ones  to  the  mediastinum. 

The  inferior  oesophageal  artery  also  anastomoses  with  a  branch  of  the 
gastric ;  most  frequently  with  that  noticed  above.  It  likewise  furnishes 
ascending  and  descending  divisions ;  the  latter,  however,  going  to  the 
mediastinum,  and  the  former  to  the  oesophagus. 

Innominate  Eamuscules.— The  innominate  ramuscules  of  the  broncho- 
oesophageal  trunk  do  not  all  come  directly  from  it ;  there  being  always 
a  certain  number  which  emerge  from  the  bronchial  or  cesophageal  arteries. 
They  are  more  particularly  distributed  to  the  trachea,  to  that  portion 
of  the  CESophagus  which  is  in  contact  with  the  posterior  extremity  of  this 
cartilaginous  tube,  to  the  bronchial  glands,  the  mediastinum,  and  the 
pulmonary  pleura.  Those  destined  for  the  latter  form  on  the  surface  of 
the  lung,  along  with  the  divisions  of  the  pleui'al  branch  furnished  by  the 
gastric  artery,  a  beautiful  plexus. 

2.  Coeliac  Artery  or  Trunk  (or  Axis). 

This  artery  arises  at  a  right  angle  from  the  inferior  face  of  the  aorta, 
immediately  on  the  entrance  of  that  vessel  into  the  abdominal  cavity. 
After  a  course  of  from  half  to  three-fourths  of  an  inch  at  most,  in  the 
middle  of  the  solar  plexus,  and  beneath  the  superior  face  of  the  pancreas,  tliis 
trunk  separates  into  three  branches :  a  middle,  the  gastric  artery  ;  a  right, 
the  hepatic  artery  ;  and  a  left,  the  splenic  artery. 

1.  Gastric  Auteky  (the  coyonaria  ventricuU  of  Man.) — This  artery 
descends  on  the  large  tuberosity  of  the  stomach,  extends  to  near  the 
insertion  of  the  oesophagus,  and  then  divides  into  two  brandies  :  the  anterior 
and  posterior  gastric.  The  first  jmsses  behind  and  to  the  right  of  the 
oesophagus,  and  crossing  the  small  curvature  of  the  stomach,  gains  the 
anterior  face  of  that  viscus,  where  it  separates  into  flexuous  and  divergent 
branches  which  run  beneath  the  serous  membrane,  and  are  carried  more 
particularly  towards  the  left  cul-de-sac  and  around  the  cardia.  The  second 
vessel  is  distributed  in  the  same  manner  to  the  posterior  wall  of  the  organ, 
but  chiefly  to  the  right  sac. 

Independently  of  these  two  arteries,  the  gastric  trunk  gives  off  a  third 
and  constant  branch,  which  often  comes  from  one  of  the  two  branches 
of  this  trunk,  and  sometimes  also  from  the  coeliac  artery  itself,  or  from  the 
splenic.  This  branch  accompanies  the  oesophagus,  along  with  the  right 
pneumogastric,  crosses  the  opening  of  the  right  pillar  of  the  diaphragm  to 
enter  the  pectoral  cavity,  and  then  divides  into  two  branches,  each  of  which 
anastomoses  with  one  of  the  oesophageal  arteries,  and  is  then  thrown  over 
the  posterior  extremity  of  pulmonary  lobe,  which  it  covers  with  a  magnifi- 
cent siibpleural  reticular  arborisation.  This  gastro-pulmonary  artery  often 
anastomoses  with  the  superior  oesophageal  branch  only,  and  goes  exclusively 
to  the  right  lung ;  for  the  left  lung  and  the  inferior  oesophageal  artery, 
in  this  case  there  is  a  special  branch  which  emanates  from  the  anterior 
gastric.  It  is  not  rare  to  meet  with  varieties  of  another  kind,  but  of  which 
it  is  not  necessary  to  speak  ;  inasmuch  as  in  these  pleural  ramifications  we 
find  a  disposition  common  to  the  whole  arterial  system :  distribution  almost 
invariable,  origin  very  inconstant. 

2.  Splenic  Artery. — The  largest  of  the  three  branches  of  the  coeHao 


528  THE  ARTERIES. 

axis,  this  sirtery  is  directed  downwards  and  to  the  left,  lying  beside  its 
satellite  vein  and  the  superior  face  of  the  left  exti-eaiity  of  the  pancreas. 
It  reaches  the  anterior  fissure  of  the  spleen  in  turning  round  the  large  tube- 
rosity of  the  stomach,  passes  along  the  entire  length  of  that  fissure,  and  leaving 
it  only  near  the  point  of  the  organ  to  throw  itself  into  the  great  omentum, 
where  it  is  named  the  left  gastro-omental  artery  (or  gastro-epiploica  sinistra). 
The  splenic  artery  gives  off,  during  its  course,  very  numerous  collateral 
branches.     These  are : 

1.  External  or  splenic  ramifications,  which  immediately  enter  the 
substance  of  the  spleen. 

2.  Internal  or  gastric  ramifications,  also  called  the  sliort  vessels  (yasa 
brevia)  in  Man,  which  are  comprised  between  the  two  layers  of  the  gastro- 
sijlenic  omentum,  and  go  to  the  great  curvature  of  the  stomach,  where  they 
nearly  always  divide  into  two  branches  :  one  which  ramifies  on  the  anterior 
wall  of  the  viscus,  the  other  on  its  posterior  wall.  These  vessels  inosculate 
with  those  sent  to  the  membranes  of  the  stomach  by  the  proper  gastric  artery. 

3.  Posterior  or  omental  twigs  of  little  importance,  destined  for  the  great 
omentum. 

Left  gastro-omental  artery. — This  artery  follows  the  great  curvature 
of  the  stomach  to  a.  distance  varying  with  the  state  of  repletion  of  that 
viscus,  passing  between  the  two  layers  of  the  omentum,  and  inosculating 
with  the  right  gastro-omental  artery.  The  branches  it  sends  oft"  on  its 
track  are  descending  or  omental,  and  ascending  or  gastric  ;  the  latter  being 
disposed  exactly  like  the  analogous  branches  emanating  directly  from  the 
splenic  artery. 

3.  Hepatic  Artery. — Applied  to  the  superior  face  of  the  pancreas,  and 
incrusted,  as  it  were,  in  the  tissue  of  that, gland,  whose  anterior  border  it 
follows,  the  hej)atic  artery  is  directed  from  left  to  right,  passes  under  the 
posterior  vena  cava,  which  it  crosses  obliquely,  reaches  the  posterior  fissure 
of  the  liver,  and  enters  it  with  the  vena  portse  to  become  broken  up  into 
several  branches,  whose  ultimate  divisions  carry  nutritive  blood  to  the  lobules 
of  the  liver. 

Before  reaching  that  organ,  however,  the  hepatic  artery  furnislies  the 
pancreatic  branches,  the  pyloric  artery,  and  the  rigid  -gastro-omental  artery. 

Pancreatic  arteries. — Irregular  and  very  numerous,  these  branches  are 
detached  from  the  hepatic  artery  on  its  passage  over  the  superior  face 
of  the  pancreas,  and  plunge  into  the  tissue  of  that  gland,  whose  arterial 
blood  is  chiefly  derived  from  this  source. 

Pyloric  artery.— T\\\^  vessel  arises  at  the  dilatation  towards  the  origin 
of  the  duodenum,  before  the  hepatic  artery  enters  the  posterior  fissure 
of  the  liver,  and  most  frequently  by  a  trunk  common  to  it  and  the  right 
gastro-omental  artery.  It  passes  towards  the  small  curvature  of  the 
stomach,  and  sends  off  branches  around  the  pylorus,  which  anastomose 
with  the  posterior  gastric  arteries  and  the  right  gastro-omental  arteiy. 

Right  gastro-omental  artery  (gastro-epiploica  dextra). — This  artery  crosses 
the  duodenal  dilatalicm  inferiorly  and  posteriorly,  to  place  itself  in  the 
substance  of  the  great  omentum ;  in  doing  which  it  passes  along  the  great 
curvature  of  the  stomach,  and  anastomoses  by  inosculation  with  the  left 
gastro-omental  artery.  In  its  course,  it  throws  off  omental  and  gastric 
branches,  which  are  analogous  to  those  emanating  fi-om  the  latter  vessel. 
Before  crossing  the  duodenum,  it  also  emits  a  particular  branch,  designated 
in  treatises  on  Veterinary  Anatomy  the  duodenal  artery ;  this  is  a  somewhat 
considerable  division,  which  follows  the  small  curvature  of  the  duodenum  in 


THE  POSTEEIOR  AORTA.  529 

the  substance  of  tlie  meseutery,  and  joins  the  first  artery  belong'ng  to  the  left 
fasciculus  of  the  great  mesenteric,  after  furnishing  some  twigs  to  the 
pancreas,  and  numerous  branches  to  the  duodeuum. 

In  terminating  the  description  of  the  right  gastro-omental  artery,  it  may 
be  remarked  that  the  stomach,  owing  to  the  anastomoses  uniting  that  vessel 
with  the  artery  of  the  left  side,  is  suspended,  as  it  were,  in  a  vertical  arterial 
circle,  formed  by  the  si)lenic  and  left  gastro-omental  arteries  on  the  one 
part,  and  the  liepatic  and  right  gastro-omental  arteries  on  the  other — a  circle 
whose  concavity  sends  out  on  the  stomach  a  great  number  of  divisions, 
which  communicate  with  the  arterial  ramuscules  proper  to  that  viscus. 

3.  Great  Mesenteric  Artery.     (Fig.  271.) 

The  great  mesenteric  artery,  which  almost  entirely  supplies  the  intestinal 
mass  with  blood,  is  as  remarkable  for  its  volume  as  for  its  complicated 
distribution.  This  complexity,  together  with  that  of  the  intestine  itself, 
gives  rise  to  some  difficulty  in  the  study  of  this  vessel ;  but  this  may  be 
averted  by  adopting  the  mode  of  description,  as  simple  as  it  is  methodical, 
resorted  to  in  his  lectures  by  M.  Lecoq. 

The  great  mesenteric  arises  at  a  right  angle  from  the  abdominal  aorta, 
at  the  renal  arteries,  and  at  2  or  2i  inches  behind  the  cceliac  trunk,  from 
w^hich  it  is  separated  by  the  pancreas  ;  it  is  directed  immediately  downwards, 
enlaced  by  the  anastomosing  nervous  branches  of  the  solar  j)lexus,  and  divides, 
after  a  course  of  from  1  to  1^  ^  inches,  into  three  fasciculi  of  branches,  wliich 
are  distinguished  as  left,  right,  and  anterior.  The  left  fasciculus  goes  to  the 
small  intestine  ;  the  right  is  distributed  to  the  termiiuil  jjortion  of  that  intes- 
tine, to  the  c9Bcum,  and  to  the  first  portion  of  the  loop  or  flexure  formed  by 
the  large  colon ;  the  anterior  is  carried  to  the  second  portion  of  that  flexure, 
and  to  the  origin  of  the  small  colon.  The  order  in  which  these  three  fasci- 
culi have  been  'indicated  will  also  be  that  followed  in  their  description ;  it 
has,  as  will  be  observed,  the  advantage  of  recalling  to  the  memory  the 
regular  succession  of  the  various  parts  of  the  intestine,  and  consequently 
the  passage  of  the  food  in  this  important  portion  of  the  digestive  canal. 

A.  Arteries  of  the  Left  Fasciculus  (Fig.  271,  2). — These  arteries 
number  from  fifteen  to  twenty,  and  are  named  the  arteries  of  the  small 
INTESTINE  (rasa  intestini  tenuis).^  because  of  their  destination.  All  spring  at 
once  from  the  great  mesenteric  artery,  either  separately,  or  several  in 
common,  and  pass  between  the  two  layers  of  the  mesentery  to  gain  the 
intestine.  Before  reaching  the  small  curvature  of  that  viscus,  each  divides 
into  two  branches,  which  go  to  meet  corresponding  branches  from  the 
neighbouring  arteries,  and  to  anastomose  with  them  by  inosculation ;  from 
this  arrangement  results  a  series  of  uninterrupted  arterial  arches,  whose 
convexity  is  downwards,  and  which  exist  for  the  whole  length  of  the  intestine 
opposite,  and  in  proximity  to,  its  concavity.  From  the  convexity  of  these 
arches  emanate  a  multitude  of  branches  that  arrive  at  the  inner  curvature 
of  the  intestine,  and  whose  divisions  pass  to  each  of  the  faces  of  that  viscus  to 
rejoin  and  anastomose  on  its  great  cmwature.  These  divisions  are  situated  be- 
neath the  peritoneum  or  in  the  muscular  layer,  and  send  the  majority  of  their 
ramuscules  to  the  mucous  tunic,  which  is  therefore  distinguished  by  its  great 
vascularity  :  a  feature  common  to  all  the  hollow  organs  in  the  abdominal  cavity. 

'  This  trunk  of  the  great  mesenteric  is  usually,  in  the  old  horses  killed  for  dissec- 
tion, the  seat  of  a  more  or  less  voluminous  aneurism,  which  sometimes  extends  to  the 
arterial  tube  placed  at  the  origin  of  the  branches  of  the  right  fasciculus,  and  it  is  not 
unfrequently  met  with  in  one  or  the  other  section  of  the  great  mesenteric  artery. 


530 


TBE  ARTERIES. 


Abdominal  aorta ;  2,  2, 
2,  Arteries  of  the  left  fas- 
ciculus, destined  for  the 
small  intestine ;  3,  Ileo- 
ctecal  artery  ;  4,  Superior 
ctecal  ai'tery ;  5,  Inferior 
Ciccal  artery ;  6,  Artery 
of  the  arch  of  the  cacum  ; 
7,  Right  colic  artery;  8, 
Left  colic  artery  ;  9,  First 
artery  of  the  small  colon. 


DISTRIBUTION   OF   THE   GREAT   MESENTERIC   ARTERT. 


TEE  POSTERIOR  AORTA.  631 

Such  is  the  general  arrangement  of  the  arteries  of  the  small  intestine ; 
and  it  remains  to  indicate  some  of  their  special  characters,  which  are  as 
follows  :  1,  The  longest  arteries  of  the  small  intestine  are  the  most  posterior, 
as  they  follow  the  development  of  the  mesentery,  by  which  they  are  sus- 
tained ;  2,  The  anterior  arteries  generally  form  two  series  of  sujjerposed 
arches,  before  sending  their  divisions  to  the  intestine ;  3,  The  first  reaches 
the  duodenum  and  anastomoses  with  the  duodenal  artery — a  branch  given  off 
by  the  cceliac  axis  ;  4,  The  last  communicates  with  the  ileo-ca^cal  artery — one 
of  the  branches  of  the  right  fasciculus. 

B.  Arteries  of  the  Eight  Fasciculus. — The  right  fasciculus  of  the 
great  mesenteric  artery  constitutes,  at  first,  a  single  trunk  some  inches  in 
length,  which  soon  divides  into  four  branches  ;  these  are  as  follows :  the 
ileo-ccecal  artery,  the  tico  ccecal  arteries,  and  the  right  or  direct  colic  artery. 

Ileo-C^cal  Artery  (Fig.  271,  3). — This  vessel  often  has  its  origin 
from  the  internal  cfecal  artery.  It  is  placed  between  the  two  layers  of  the 
n^esentery,  follows  for  a  short  distance,  and  in  a  retrogade  manner,  the  ileo- 
(jecal  portion  of  the  small  intestine,  and  wholly  anastomoses  with  the  last 
artery  of  the  left  fasciculus,  after  emitting  a  series  of  branches,  which  are 
distributed  to  the  intestinal  membranes. 

C-ECAL  Arteries. — Distinguished  into  internal  or  superior,  and  external 
or  inferior,  these  two  arteries  pass  downward  and  a  little  to  the  right, 
towards  the  concavity  of  the  csecal  flexure,  embracing  between  them  the 
terminal  extremity  of  the  small  intestine,  and  lying  at  the  middle  part 
of  the  caecal  sac,  whose  direction  they  follow. 

The  superior,  or  internal  ccecal  artery,  is  lodged  in  the  most  anterior 
of  the  fissures  formed  by  the  longitudinal  bands  of  the  caecum,  and  extends 
beneath  the  serous  tunic  to  nearly  the  point  of  the  viscus,  where  it  terminates 
by  anastomosing  with  the  external  csecal  artery.  The  branches  furnished 
hj  this  artery  during  its  course  escape  in  a  perpendicular  direction,  and 
distribute  their  ramifications  on  the  walls  of  the  cascum  (Fig.  271,  4). 

The  external,  or  inferior  csecal  artery,  passes  between  the  caecum  and  the 
origin  of  the  colon,  to  descend  along  the  first-named  receptable  by  placing 
itself  in  one  of  the  external  fissures,  which  is  situated  outwardly  and 
posteriorly.  Arriving  at  the  point  of  the  organ,  this  artery  bends  over  it  to 
anastomose  with  the  vessel  just  described  (Fig.  271,  7).  It  gives  off  on  its 
track  a  series  of  transverse  ramifications,  similar  to  those  of  the  latter  artery  ; 
and  besides  these,  a  remarkable  branch  which  may  be  named  the  artery  of 
the  ccecal  arch.  This  branch  is  detached  from  the  principal  vessel  near  the 
origin  of  the  colon,  and  ascends  to  the  caecal  arch,  whose  concavity  it  follows 
outwardly  to  pass  forwards  and  downwards  to  the  initial  portion  of  the  large 
colon,  where  it  disappears  after  following  a  certain  course.  The  numerous 
collateral  branches  detached  by  this  ai-tery  are  sent  to  the  walls  of  the  latter 
portion  of  intestine,  and  the  arch  of  the  cfecum  (Fig.  271,  6 ). 

Right  or  Direct  Colic  Artery  (Fig.  271,  7). — This  is  the  largest  of 
the  branches  composing  the  right  fasciculus  of  the  great  mesenteric  artery. 
Destined  for  the  right  portion  of  the  flexure  formed  by  the  large  colon,  it 
lies  immediately  beside  that  viscus,  beneath  the  peritoneal  membrane, 
following  it  from  its  origin  to  its  pelvic  curvature,  Avhere  the  artery 
anastomoses  by  inosculation  with  the  left  colic  or  retrograde  artery. 

C.  Arteries  of  the  Anterior  Fasciculus. — These  are  only  two  in 
nmnher:  the  left  colic  or  retrograde,  and  the  first  artery  of  the  small  colon, 
joined  at  their  origin  to  an  extremely  short  trunk. 

Left  Colic  ok   Eetrograde   Artery  (Fig.   271,  8). — This  is  carried 


532  THE  ARTERIES. 

to  the  left  portion  of  tlie  colic  flexure,  which  it  passes  over,  beneath  the 
peritoneum,  from  the  terminal  extremity  of  the  viscus  to  the  pelvic  curvature, 
where  it  meets  the  right  artery ;  in  tiiis  manner  it  follows  a  course  the 
inverse  of  that  i)ursucd  by  the  aliment,  and  whence  its  name  of  retrograde 
colic  artery. 

Considered  collectively,  the  two  colic  arteries  represent  a  loop  or  flexure 
exactly  like  that  formed  by  the  large  colon  itself.  They  proceed  parallel  to 
each  other,  and  finish,  after  being  slightly  separated,  by  uniting  to  form  a 
parabolic  curve.  This  arterial  loop  occupies  a  deep  position  on  the 
intestinal  loop,  being  found  on  the  inferior  face  of  the  first  and  fourth 
sections  of  the  large  colon,  in  the  concavity  of  the  flexure  which  gives 
rise  to  the  suprasternal  and  diaphragmatic  curvatui'es,  and  on  the  superior 
plane  of  the  second  and  third  jjortions  of  the  viscus. 

A  considerable  number  of  collateral  branches  escape  perpendicularly 
from  this  arterial  loop,  and  jiass  into  the  membranes  of  the  intestine; 
some  of  them  establish  a  transverse  communication  between  the  two  vessels. 

First  Artery  of  the  Small  Colon  (Figs.  271,  9 ;  272,  4). — This 
branch,  whose  calibre  is  often  considerable,  is  inflected  to  the  left, 
downwards  and  backwards,  to  be  placed  in  the  substance  of  the  colic 
mesentery,  very  near  the  lesser  curvature  of  the  floating  or  small  colon.  It 
soon  meets  a  branch  of  the  small  mesenteric  artery,  with  which  it  anasto- 
moses by  inosculation. 

D.  Innominate  Branches  of  the  Great  Mesentery. — These  are  the 
twigs  sent  to  the  lymphatic  glands,  supra-renal  capsules,  mesentery,  and 
pancreas,  and  whose  existence  it  is  sufficient  merely  to  mention.  Among 
those  supplied  to  the  pancreas,  there  is  one  of  somewhat  considerable  volume. 

E.  The  Anastomoses  of  the  Great  Mesenteric  Artery. — The 
multiplicity  and  calibre  of  these  anastomoses  assure,  in  the  most  favourable 
manner,  the  circulation  of  the  blood  in  the  intestinal  mass,  which,  by  reason 
of  its  great  mobility,  is  exposed  to  displacements  capable  of  inducing  more  or 
less  extensive  compression.  Not  only  do  these  anastomoses  unite  the 
different  branches  destined  to  the  same  portion  of  the  viscera,  be  it  the  small 
intestine,  the  cfecum,  or  the  large  colon  ;  but  they  also  establish  communica- 
tions between  the  great  mesenteric  artery  and  the  neighbouring  trunks, 
which  in  case  of  need  can  maintain  the  circulation :  as,  for  example,  when  the 
two  intestinal  arteries  are  completely  obstructed.  The  blood  from  the 
coeliac  trunk  can  really  pass  from  the  duodenal  artery  into  the  branches 
of  the  left  fasciculus  of  the  great  mesenteric  artery  :  then  by  the  ileo-cascal 
artery  into  the  branches  of  the  right  fasciculus,  and  thence  into  the  left 
colic  artery,  which,  finally,  transmits  it  to  the  first  artery  of  the  small  colon, 
as  well  as  to  the  arches  of  the  small  mesenteric  artery.  The  communica- 
tion existing  between  the  broncho-cesophageal  and  the  coeliac  trunks,  through 
the  medium  of  the  oesopliageal  and  gastric  arteries,  even  allows  a  collateral 
circulation  to  be  formed,  and  which  would  be  capable  of  supplementing  the 
posterior  aorta,  supposing  that  vessel  tied  behind  the  trunk  that  distributes 
blood  to  the  bronchi  and  oesophagus. 

4.  Small  Mesenteric  Artery.     (Fig.  272.) 

This  artery  carries  blood  to  the  small  colon  and  rectum,  and  arises  at  a 
right  angle  from  the  inferior  face  of  the  abdominal  artery,  from  4^  to 
6  inches  behind  the  great  mesenteric.  It  descends  between  the  two  layers 
of  the  colic  mesentery,  and  is  soon  inflected  back  in  describing  a   curve 


TEE  POSTERIOB  AORTA.  533 

upwards,  to    pass   above   the   rectum ;    when  near  the   anus,  its  terminal 
divisions  enter  the  walls  of  that  intestine. 

In  its  course  this  artery  gives  otit",  at  pretty  regular  intervals,  thirteen  or 
fourteen  branches,  the  foremost  of  which  are  the  largest  and  longest ;  they 
orif^inate  from  the  convexity  of  the  artery — that  is  from  below,  and  either 

Fig.  272. 


DISTRIBUTION  OF  THE  SMALL  MESENTERIC  ARTERY;  THE  SMALL  COLON  WITH  ITS 
MESENTERY  IS  SPREAD  OUT,  AND  THE  SMALL  INTESTINE  THROWN  BACK  TO  THE 
RIGHT   UNDER   THE   LARGE   COLON. 

1,  Trunk  of  the  small  mesenteric  artery;  2,  Great  mesenteric  artery;  3,  Its 
anterior  fasciculus ;  4,  First  artery  of  the  small  colon,  forming  part  of  that 
fosciculus  ;  5,  Retrograde  colic  artery ;  6,  Right  fasciculus  of  the  great  mesen- 
teric; 7,  Branches  of  the  left  fasciculus;  8,  Renal  artery;  9,  Terminal  extremity 
of  the  aorta;  10,  External  iliac  artery  ;  11,  Circumflex  iliac  artery  ;  12,  Internal 
iliac  artery. 

singly  or  in  clusters ;  the  latter  disposition  is  the  most  common  for  the  first 
four  or  five.  They  descend  into  the  mesentery  and  arrive  near  the  superior 
curvature  of  the  intestine,  where  they  are  disposed  in  the  following  manner: 
The  first  seven  or  eight  bifurcate,  and  form  arches  like  those  of  the  artei-ies 
supplying  the  small  intestine,  differing  from  them  only  in  being  nearer  the 
37 


534  THE  ARTERIES. 

small  curvature  of  the  colon ;  the  other  branches,  which  are  destined  for 
the  terminal  part  of  that  viscus  and  the  rectum,  ramify  in  the  intestinal 
membranes  without  having  previously  formed  any  arches. 

The  anterior  ramuscule  of  the  first  branch  anastomoses  directly  with  the 
artery  sent  to  the  small  colon  by  the  great  mesenteric,  and  from  this 
anastomosis  results  the  first  colic  arterial  arch. 

5.  Eenal  or  Eniulgent  Arteries.     (Fig.  275,  2.) 

These  are  two  arteries,  one  for  each  kidney,  detached  laterally,  and  at  a 
right  angle,  from  the  abdominal  aorta,  near  the  great  mesenteric  artery ; 
passing  outwards  to  the  internal  border  of  these  organs,  each  divides 
into  several  branches,  which  enter  the  gland  either  by  its  notch  or  by  its 
inferior  face.  Eeaching  the  interior  of  the  kidney,  these  branches  subdivide, 
and  form  a  network  of  large  vessels  placed  on  the  limit  between  the  cortical 
and  medullary  substances,  from  which  a  multitude  of  ramuscules  are  given 
off,  and  pass  almost  exclusively  into  the  tissue  of  the  cortical  portion.  (See 
the  description  of  the  kidneys.) 

The  right  renal  artery,  longer  than  the  left,  passes  between  the  small 
psoas  muscle  and  the  posterior  vena  cava,  to  reach  the  right  kidney.  Both 
arteries  are  in  relation  with  the  posterior  extremity  of  the  supra-renal 
capsules. 

Remarkable  for  their  iclatively  enormous  volume,  when  compared  with 
that  of  the  glands  receiving  them,  these  arteries  do  not,  before  penetrating 
the  proper  tissue  of  the  kidneys,  give  off  any  but  a  few  unimportant 
ramuscules,  the  principal  of  which  proceed  to  the  supra-renal  capsules 
(Fig.  275).  Other  twigs  from  the  great  mesenteric  artery,  or  even  from  the 
aorta  itself,  also  supply  these  small  bodies.  It  is  not  unusual  to  find 
the  kidneys  receiving  vessels  from  the  arteries  in  their  vicinity.  Thus,  we 
have  seen  an  artery  from  the  external  iliac  pass  into  a  kidney  by  its  lower 
face ;  and  we  have  also  observed  an  artery,  detached  from  the  aorta  along 
with  the  great  mesenteric,  enter  the  kidney  by  its  anterior  border. 

6.  Spermatic  Arteries. 

These  arteries  differ  in  the  male  and  female  ;  in  the  male  they  are 
also  named  the  great  testicular  arteries ;  in  the  female  they  are  exclusively 

■  designated  as  the  utero-ovarian  arteries. 

Great  Testicular  Artery  (Fig.  275,  3). — This  arises  close  to 
the  small  mesenteric  artery,  either  before,  behind,  or  to  one  side  of  it,  but 
rarely  on  the  same  level  as  the  artery  of  the  opposite  side;    it   is   then 

■  directed  backwards  and  downwards,  sustained,  with  its  satellite  vein,  in  a 
particular  fold  of  peritoneum,  and  reaches  the  entrance  to  the  vaginal  sheath 
(internal  abdominal  ring),  into  which  it  is  seen  to  pass  with  the  other 
constituent  portions  of  the  spermatic  cord,  and  to  descend  on  the  testicle 
by  forming  remarkable  flexuosities  united  in  an  elongated  mass.  Arrived 
within  the  head  of  the  epididymis,  this  artery  insinuates  itself  under  the 
tunica  albuginea,  becomes  incrusted,  as  it  were,  in  its  substance,  and 
successively  passes  round  the  superior  border,  posterior  extremity,  and_  the 
inferior  border  and  anterior  extremity  of  the  testicle.  In  this  course  it  is 
very  sinuous,  and  detaches  at  a  right  angle  a  large  number  of  equally 
flexuous  branches,  which  creep  over  the  faces  of  the  organ  while  sending 
numerous  ramuscules  into  its  structure.  The  epididymis  also  receives  its 
blood  by  this  artery. 


THE  POSTERIOR  AORTA.  535 

Utero-ovarian  Artery. — The  origin  of  this  vessel  is  conformable  with 
that  of  the  preceding  artery.  It  is  placed  between  the  two  laminae  of  the 
broad  ligament,  and  soon  bifurcates  into  the  ovarian  and  uterine  arteries.  The 
ovarian  branch  describes  numerous  flexuosities,  like  the  corresponding  artery 
in  the  male,  and  comports  itself  on  the  ovary  in  the  same  manner  as  the 
latter  vessel  does  on  the  testicule.  The  uterine  branch  passes  to  the  cornu 
of  the  uterus,  where  its  divisions  anastomose  with  the  proper  uterine  artery. 

7.  Small  Testicular  Arteries:  Male.     Uterine  Arteries:  Female. 

Small  Testicular  Artery  (Cremasteric  Artery,  Artery  op  the 
Cord). — A  pair,  like  the  great  testicular  artery,  this  vessel  is  very  slender, 
and  originates  either  from  the  aorta  between  the  internal  and  external  iliacs, 
or  from  the  latter,  near  its  commencement.  The  last  being  the  most 
common,  it  is  usual  to  describe  it  as  a  collateral  branch  of  the  crural  (external 
iliac)  trunk.  We  have  regarded  it  as  an  artery  emanating  directly  from 
the  posterior  aorta,  in  order  to  include  its  description  with  that  of  the  great 
testicular  and  the  utero-ovarian  arteries. 

Whatever  may  be  its  mode  of  origin,  it  gains  the  entrance  to  the  vaginal 
sheath,  and  enters  it  with  the  spermatic  vessels,  to  be  distributed  to  the 
various  parts  constituting  the  cord.  Before  penetrating  the  substance  of  this 
cord,  it  gives  oflf  several  ramuscules  destined  for  the  peritoneum,  iliac  glands, 
ureter,  and  deferent  canal. 

Uterine  Artery. — This  has  the  same  point  of  origin  as  the  preceding, 
its  analogue,  but  differs  from  it  in  its  larger  volume.  It  is  placed  between 
the  two  layers  of  the  lumbar  ligament,  and  is  divided  into  two  branches  on 
arriving  at  the  small  curvature  of  the  uterine  cornu :  the  anterior  branch 
anastomoses  by  its  divisions  with  the  utero-ovarian  artery ;  the  posterior 
passes  to  the  body  of  the  matrix,  where  it  communicates  with  the  vaginal 
artery. 

deffebential  characters  of  the  posterior  aorta  and  its  collateral  branches  in 
other  than  soliped  animals. 

1.  Posterior  Aorta  in  Ruminants. 

The  artery  pursues  the  same  course  as  in  Solipeds,  and  also  terminates  by  four 
branches,  towards  the  entrance  to  the  pelvic  cavity. 

Parietal  Branches. — The  intercostal  arteries  only  differ  from  those  of  the  Horse  in 
their  number ;  as  but  twelve  are  met  with,  of  which  eight  or  nine  alone  are  furnished  by 
the  posterior  aorta. 

The  lumbar  and  diaphragmatic  branches  are  absolutely  identical,  in  their  disposition, 
with  the  analogous  arteries  of  Solipeds. 

The  middle  sacral  artery  is  more  considerable  in  volume,  particularly  in  the  Sheep 
and  Goat.     This  will  be  referred  to  hereafter  (see  interjial  iliac  artery  of  EuminantsJ. 

Visceral  Branches. — Broncho-oesophageal  trunk. — This  offers  nothing  particular. 

Coeliac  trunk  (Fig.  273,  1 ). — This  artery  descends  on  the  rumen,  a  little  behind  the 
insertion  of  the  oesophagus,  is  directed  to  the  right,  and  divides  near  the  omasum  into 
two  terminal  branches — the  superior  and  inferior  arteries  of  the  omasum  and  dbomasum. 

The  collateral  branches  escaping  from  this  trunk  are  : 

1.  Several  diaphragmatic  arteries. 

2.  The  splenic  artery,  almost  exclusively  destined  for  the  spleen  (Fig.  273,  8). 

3.  The  superior  artery  of  the  rumen,  always  arising  from  a  very  short  trunk  common 
to  it  and  the  prece<ling  vessel,  is  carried  backward  to  the  superior  face  of  the  rumen,  and 
from  this  descends  between  the  two  conical  vesicae  to  anastomose  with  the  artery  of  the 
inferior  face  of  the  viscus  (Fig.  273,  2). 

4.  The  inferior  artery  of  the  rumen,  which  is  insinuated  between  the  two  anterior 
culs-de-sac,  and  afterwards  runs  along  the  inferior  face  of  the  organ,  passing  towards 
the  notch  separating  the  two  conical  vesicaB,  to  meet  the  superior  vessel  (^Fig.  273,  3). 


536 


TSE  ARTERIES. 


5.  The  artery  of  the  reticulum,  having  usually  a  common  origin  with  the  inferior 
artery  of  the  rumen,  and  passing  forward  on  the  left  of  the  cesophagus,  to  be  divided, 
near  the  insertion  of  that  conduit,  into  two  branches :  one,  the  superior,  inclines  to  the 
right  to  the  small  curvature  of  the  viscus  (Fig.  273,  5) ;  the  other,  the  inferior.,  occupying 
the  fissure  separating  the  great  curvature  of  the  reticulum  from  the  right  sac  of  the 
paunch,  and  giving  to  the  latter  organ  a  great  number  of  branches  (Fig.  273,  4). 

6.  The  hepatic  artery,  which  is  not  only  distributed  to  the  liver,  but  also  furnishes  a 
branch  for  the  gall-bladder,  and  a  duodenal  artery  breaking  up  into  two  branches  :  the 
posterior  branch  forming  with  the  first  artery  of  the  small  intestine  an  arching  anasto- 
mosis ;  the  anterior  communicating  with  the  superior  artery  of  the  omasum  and  abomasum. 
This  hepatic  artery  always  originates  between  the  trunk  common  to  the  splenic  artery 
and  the  superior  branch  of  the  rumen,  and  that  which  gives  rise  to  the  superior  branch 
of  the  same  viscus  and  the  artery  of  the  reticulum. 

The  terminal  branches  of  the  cceliac  artery  comport  themselves  as  follows  : 
1.  The  superior  artery  of  the  omasum  and  abomasum  passes  successively  to  the  great 
curvature  of  the  first  of  these  reservoirs,  and  to  the  concave  curvature  of  the  second ;  then 
it  goes  beyond  the  pylorus  to  unite  with  the  duodenal  branch  of  the  hepatic  artery  by 
inosculation  (Fig.  273,  6). 

Fig.  273. 


ARTERIES  OF   THE   STOMACH   IN   RUMINANTS. 

1,  Coeliac  trunk ;  2,  Superior  artery  of  the  rumen ;  3,  Inferior  artery  of  the 
rumen  ;  4,  Inferior  artery  of  the  reticulum  ;  5,  Superior  artery  of  the  reticulum ; 
6,  Superior  artery  of  the  omasum  and  abomasum ;  7,  Inferior  artery  of  ditto ; 
8,  Splenic  artery ;  A,  Oesophagus  ;  B,  Left  sac  of  the  rumen ;  b'.  Left  conical 
vesica ;  c,  Right  sac  of  the  rumen  ;  o',  Right  conical  vesica ;  D,  Reticulum ;  E, 
Omasum ;  r,  Abomasum  ;  G,  Duodenum ;  R,  Spleen 


2.  The  inferior  artery  of  the  omasum  and  abomasum,  on  the  contrary,  passes  at  first 
over  the  sma'h  curvature  of  the  omasum,  afterwards  the  great  curvature  of  the  abomasum, 
and  disappears  in  the  omentum,  to  which  on  its  course  it  furnishes  a  great  number  of 
branches  (Fig.  273,  7). 

In  small  Ruminants,  the  distribution  of  the  arteries  of  the  cceliac  trunk  presents 
some  modifications.  We  will  cite  the  principal,  which  belong  to  the  mode  of  origin  of 
the  two  branches  destined  for  the  reticulum :  these  branches  form  two  particular 
vessels  which  arise  singly  from  the  cceliac  trunk  ;  the  inferior  artery  at  tlie  same  point  as 
the  superior  artery  of  the  rumen,  the  superior  towards  the  terminal  bifurcation  of  the 
trunk. 

Great  mesenteric  artery. — Its  origin  approaches  very  closely  that  of  the  cceliac  trunk. 
After  a  course  of  from  6  to  8  inches,  it  divides  into  two  branches— an  anterior  and  a 


THE  POSTERIOR  AORTA.  537 

posttrior.  The  first,  destined  for  the  small  intestine,  creeps  above  it,  between  the  two 
layers  of  the  mesentery,  and  passes  backward  by  describing  a  curve  which  gives  off  from 
its  convexity — that  is,  below,  a  great  number  of  branches,  analogous  in  their  mode  of 
termination  to  the  arteries  of  the  small  intestine  in  the  Horse.  The  posterior  branch  goes 
to  the  large  intestine,  where  it  separates  into  two  principal  branches  :  one  which  passes 
to  the  colon,  and  whose  divisions  cross  to  the  right,  from  before  to  behind  and  from  above 
to  below,  the  convolutions  described  by  that  viscus  ;  another  which  reaches  the  concave 
curvature  of  the  caecum,  and  anastomoses  by  an  arch  with  the  terminal  extremity  of  the 
parent-branch  of  the  arteries  supplying  the  small  intestine. 

SmaU  mesenteric  artery. — Very  short  and  narrow. 

Renal,  spermatic,  and  small  testicular  arteries. — These  do  not  differ  in  their  essential 
disposition  from  the  analogous  vessels  in  Solipeds. 

2.  Posterior  Aorta  in  the  Pig. 

With  the  exception  of  the  mesenteric  vessels,  whose  distribution  resembles  that 
already  indicated  for  Ruminants,  and  with  the  exception,  also,  of  the  middle  sacral  artery, 
which  will  be  alluded  to  when  describing  the  internal  iliac  arteries,  all  the  branches 
given  off  by  the  posterior  aorta  comport  themselves  almost  as  in  the  Horse. 

3.  Posterior  Aorta  in  Carnivora. 

In  these  animals,  as  well  as  in  the  Pig,  the  denomination  of  posterior  aorta  is  not 
justifiable,  because  the  arteries  of  the  head  and  thoracic  limbs  spring  directly  from  the 
aortic  arch. 

The  branches  of  the  aorta  are  distinguished  as  parietal  and  visceral. 

A.  Parietal  Branches. — Beyond  the  fourth  space,  the  intercostal  arteries  are  fur- 
nished by  the  aorta  •  the  first  is  voluminous,  and  throws  off  some  considerable  filaments 
to  the  muscles  of  the  withers.  The  first  two  lumbar  arteries  arise  from  the  thoracic 
portion  of  the  aorta,  because  of  the  very  backward  insertion  of  the  diaphragm  ;  the  third 
is  detached  between  the  two  pillars  of  that  partition.  In  the  abdominal  cavity,  close  to 
the  great  mesenteric,  the  aorta  gives  oft'  a  branch  that  soon  divides  into  two  :  one  is 
diaphragnuitic,  and  descends  on  the  posterior  face  of  tliat  muscle  ;  the  other  reaches  the 
sublumbar  region,  passes  over  the  psoas  muscle,  and  traverses  the  abdominal  wall  in  the 
vicinity  of  the  transverse  processes  of  the  lumbar  vertebrae.  We  will  speak  presently  of 
the  middle  sacral. 

B.  Visceral  Bbaxches. — I  have  not  found  in  the  Dog  any  special  bronchial  arteries ; 
but  there  are  four  or  five  cesophageal  arteries  that  arise  from  difi'erent  points  of  the 
thoracic  aorta  ;  they  descend  into  the  mediastiimm,  to  the  right  and  left  of  the 
oesophagus,  to  which  they  are  distributed.  They  furnish  branches  that  accompany  the 
bronchi  and  enter  the  lungs. 

The  cceliac  trunk  is  again  divided  into  three  branches,  whose  disposition  is  as  follows : 
The  gastric,  or  stomachic  coronary  artery,  does  not  divide  into  two  branches  fanterior  and 
posterior  gastric j  as  in  Solipeds.  Near  its  origin  it  furnishes  a  pancreatic  branch ;  then 
it  expends  itself  in  a  great  number  of  filaments  that  are  spread  over  the  posterior  face 
and  great  tuberosity  of  the  stomach,  or  over  its  anterior  face  after  crossing  the  small 
curvature. 

The  splenic  artery  reaches  the  spleen  at  the  middle  of  its  upper  border.  It  gives  on 
its  course :  1,  A  splenic  branch  that  enters  the  upper  extremity  of  that  organ ;  2,  The 
left  gastro-omental.  The  hepatic  artery  provides  the  principal  hepatic  vessel  at  the 
posterior  fissure  of  the  liver;  it  is  then  continued  by  the  right  gastro-omental  artery. 
On  the  duodenum,  the  latter  gives  origin  to  the  pyloric  and  the  pancreatico-duodenal 
branches ;  the  latter  is  voluminous,  is  lodged  in  the  substance  of  the  pancreas,  and 
anastomoses  by  its  last  filaments  with  the  great  mesenteric. 

The  great  mesenteric  artery  arises  in  the  vicinity  of  the  cceliac  artery ;  it  forms  a  curve 
whose  convexity  is  backward,  and  anastomoses  by  its  extremitj'  with  the  pancreatico- 
duodenal branch  of  the  hepatic.  From  its  convexity  are  detacht  d  several  filaments 
(filaments  to  the  small  intestine),  that  form  arches  towards  the  smaller  curvature  of  that 
viscus.  Behind,  and  at  a  short  distance  from  its  origin,  it  gives  a  branch  to  the  caecum 
and  branches  to  the  colon ;  the  latter  are  sometimes  large. 

The  smdl  mesenteric  commences  near  the  termination  of  the  aorta,  and  divides  into 
two  brandies  .  one  passing  forward,  and  the  other  backward ;  they  form  the  haemorrhoidal 
vessels  (see  Fig.  209). 

There  is  nothing  special  to  note  with  regard  to  the  renal  and  spermatic  arteries. 


538  THE  ARTERIES. 

COMPARISON  OF  THE   AORTA   OP  MAN  WITH  THAT   OF  ANIMALS. 

The  aorta  in  Man  offers  the  same  general  disposition  as  in  the  Carnivora,  the  trunk 
being  inflected  across,  to  be  placed  along  the  body  of  the  dorsal  and  first  lumbar  vertebrae, 
where  it  terminates  in  the  iliac  vessels. 

It  furnishes  the  coronary  arteries,  the  arteries  of  tlie  head  and  thoracic  members — 
which  will  be  noticed  hereafter  ;  and  the  parietal  and  visceral  branches  to  the  chest  and 
abdomen.  At  first  these  are  the  intercostals,  beyond  the  third  space ;  the  diaphracjmatic 
arteries,  superior  and  inferior  according  as  tliey  occupy  one  or  other  face  of  the  duipliragm ; 
and,  lastly,  the  lumbar  arteries. 

Among  the  visceral  branches  are  distinguished:  I,  The  bronchial  arteries,  two  in 
number ;  the  left  arises  from  the  concavity  of  the  aortic  arch,  and  enters  the  lungs  with 
the  left  bronchus ;  the  right  originates  alone  or  in  common  with  the  preceding,  and  enters 
on  the  right  bronchus ;    2,  The  oesophageal  arteries  disposed  somewhat  as  in  tlie  Dog  ; 

3,  The  cceliac  trunk,  whose  distribution  is  nearly  identical  with  that  of  the  Carnivora  ; 

4,  The  superior  or  great  mesenteric,  disposed  in  arches  as  in  the  Dog  (see  Fig.  27G,  9).  Its 
last  branches  pass  to  the  csecum,  and  the  ascending  and  origin  of  the  transverse  portion  of 
the  colon  ;  5,  The  inferior  or  small  mesenteric,  which  arises  1|  to  2  inches  from  tlie  bifur- 
cation of  the  aorta ;  this  artery  descends  into  the  meso-colon,  and  terminates  on  the  sides 
of  the  rectum  by  the  hseraorrhoidal  vessels ;  to  the  left,  they  emit  branches  to  the  large 
intestine ;  the  first  ascend  along  the  descending  colon,  and  anastomose  on  the  transverse 
colon  with  the  right  colic  branch  of  the  superior  mesentetic ;  6,  The  renal  and  capsular 
arteries,  which  do  not  offer  important  differences  ;  7,  Lastly,  the  spermatic  arteries,  which 
are  remarkable  for  the  length  of  their  course,  commencing,  as  tliey  do,  at  the  aorta,  a 
short  distance  below  the  renal  vessels 

Article  III.— Internal  Iliac  Arteries  or  Pelvic  Trunks,    (Fig.  277,  2.) 

The  two  internal  iliac  arteries  represent  the  middle  or  internal  branches 
of  the  quadrifurcation  formed  by  the  posterior  aorta  at  its  terminal  extremity. 
•  Extending  from  the  body  of  the  last  lumbar  vertebraB,  to  near  the 
terminal  insertion  of  the  small  psoas  muscle,  in  an  oblique  direction 
downvs^ards,  outwards,  and  backwards,  these  arteries  correspond :  in  front, 
with  the  trunks  of  the  common  iliac  veins,  which  separate  them  from  the 
external  iliacs ;  inwards,  to  the  peritoneum ;  above  and  outwards,  to  the 
sacro-iliac  articulation  and  to  the  ilium. 

In  its  course,  the  internal  iliac  artery  emits  the  following  branches  :  the 
umbilical  artery,  artery  of  the  hulb,  ileo-lumhar,  gluteal,  and  subsacral  arteries. 
At  its  terminal  extremity,  it  is  divided  into  two  branches  which  ride  on  the 
superior  border  of  the  tendon  belonging  to  the  small  psoas  muscle :  the  one 
within,  the  other  without  that  tendon.  The  first  is  the  obturator  artery,  the 
second  the  ileo-femoral  artery.  All  these  branches  will  be  studied  in  the 
order  of  their  enumeration. 

Preparation  of  the  internal  iliac  artery. — Place  the  subject  in  the  first  position; 
remove  one  of  the  posterior  limbs,  leaving  the  rectum  and  bladder  in  the  pelvis,  and 
slightly  inflating  the  latter  organ.  Dissect,  on  the  side  from  which  the  limb  has  been 
removed,  the  origin  and  visceral  ramifications  of  the  branches  furnished  by  the  trunk  of 
the  artery.  Follow,  on  the  opposite  side,  the  ramifications  given  oft'  by  these  branches  to 
the  muscles.  To  conveniently  prepare  the  coccygeal  arteries,  it  is  necessary,  after 
removing  the  great  sciatic  ligament  and  dissecting  the  internal  artery  of  the  bulb  along 
with  the  subsacral  trunk,  to  raise  up  the  rectum  and  bladder  by  means  of  the  chain-hooks. 

.   Umbilical  Artery.     (Figs.  274,  5  ;  277,  3.) 

This  artery  forms  a  considerable  vessel  during  foetal  life,  and  carries  the 
blood  of  the  foetus  to  the  placenta ;  it  will  be  described  in  detail  in  the 
anatomy  of  the  fostus. 

In  the  adult  it  is  almost  entirely  obliterated,  appearing  only  as  a  fibrous 
cord  extending  from  the  internal  iliac  artery  to  the  fundus  of  the  bladder, 
and  placed  at  the  free  margin  of  the  lateral  serous  fold  detached  from  the 


THE  INTERNAL  ILIAC  ARTERIES. 


539 


cul-de-sac  of  that  organ.     This  cord  throws  oflf  on  its  track,  one  or  more 
vesical  branches,  beyond  which   its  canal  altogether  disappears.      These 

Fig.  274. 


A,  Left  kidney ;  B,  Right  kid- 
ney ;  a,  b,  Ureters ;  C,  C, 
Supra-renal  capsules ;  D, 
Bladder ;  e,  e,  Testicles ; 
e,  Head  of  the  epididymis ; 
e',  Tail  of  the  epididymis ; 
F,  Deferent  canal  ;  G,  Pel- 
vic dilatation  of  the  defe- 
rent canal ;  H,  Left  vesicula 
seminales ;  tlie  right,  with 
the  deferent  canal  of  the 
same  side,  has  been  I'emoved, 
to  show  the  insertion  of 
the  ureter  into  the  bladder ; 

1,  Prostate ;  J,  Cowper's 
glands ;  K,  Membranous 
portion  of  the  urethral 
canal ;  L,  Bulbous  portion 
of  the  same  ;  M,  Cavernous 
body  of  the  penis  ;  m,  m. 
Its  roots ;  N,  Head  of  the 
penis. — 1,  Abdominal  aorta; 

2,  2,  Renal  arteries  giving 
off  the  principal  capsular 
artery ;     3,    Spermatic,     or 

great  testicular  artery ;  4,  Common  origin  of  the  internal  pudic  and  umbilical  arteries; 
5,  Umbilical  artery ;  6,  Its  vesical  branch ;  7,  Internal  pudic  artery ;  8,  Its  vesico- 
prostatic  branch. 


UPPER   AND   GENEKAL   VIEW   OF   THE   GENITO-URINAEY 
APPARATUS    AND    ARTERIES    IN    THE    MALE. 


540  TRE  ARTERIES. 

vesical  branches  also,  though  very  rarely,  come  from  the  internal  artery  of 
the  bulb ;  in  which  case  the  obliteration  of  the  umbilical  artery  is  complete. 

2.  Internal  Pudic  Artery,  or  Artery  of  the  Bulb. 
(Figs.  274,  7 ;  275,  16  ;  277,  4.) 

This  vessel  differs  in  its  distribution  in  the  male  and  female. 

Internal  Pudic  Artery  in  the  Male.—  It  proceeds  from  the  internal 
iliac,  near  the  origin  of  that  vessel,  by  a  trunk  common  to  it  and  the 
umbilical  artery  ;  it  is  then  directed  backwards,  following  the  superior  border 
of  the  internal  obturator  (pyriformis)  muscle,  and  placed  either  without  or 
within  the  texture  of  the  great  ischiatic  ligament.  Arrived  at  the  neck  of  the 
bladder,  it  enters  the  pelvic  cavity,  lying  beside  the  prostate  and  Cowper's 
glands,  and  is  finally  inflected  downwards,  passing  roimd  the  ischial  arch  to 
reach  the  bulb  of  the  urethra. 

In  its  progress  it  furnishes  : 

1.  Insignificant  ramuscules  to  the  muscle  adjoining  the  sacro-ischiatic 
ligament. 

2.  The  vesico-prostatic  artery  (Figs.  274,  8;  275,  17).  This  is  a 
branch  constant  in  its  distribution,  but  variable  in  its  origin.  Destined  to 
supply  the  prostate  gland,  vesiculae  seminales,  the  pelvic  dilatation  of  the 
deferent  canal  and  the  canal  itself,  as  well  as  the  bladder,  it  usually 
commences  near  the  prostate  gland,  and  passes  from  behind  to  before,  in  a 
flexuous  manner,  on  the  vesiculae  seminales  and  the  deferent  canal. 

3.  Slender  ramifications  for  the  pelvic  portion  of  the  urethral  canal, 
Cowper's  glands,  the  anus,  and  the  ischio-cavernous  muscle  (erector  penis). 

The  terminal  extremity  of  the  vessel  is  insinuated  beneath  the  accel- 
erator muscle,  and  immediately  divides  into  a  multitude  of  ramuscules 
which  enter  the  erectile  tissue  of  the  urethral  bulb,  where  they  comport 
themselves  as  in  all  tissues  of  this  kind. 

Varieties.— It  is  not  rare  to  see  the  artery  of  the  bulb  detach,  before 
attaining  Cowper's  gland,  the  cavernous  artery,  which  then  passes  round  the 
ischial  arch  along  with  the  nerve  of  the  penis.  Sometimes  it  only  gives  ofi 
the  posterior  dorsal  artery  of  the  penis,  a  branch  of  the  cavernous. 

Distribution  op  the  Internal  Pudic  Artery  in  the  Female.  (Fig. 
277,  4.) — This  artery  terminates,  towards  the  vagina,  by  rectal,  vulvular, 
vaginal,  and  bulbous  branches  ;  the  latter  are  for  the  bulb  of  the  vagina. 
As  in  the  male,  it  does  not  give  off  more  than  one  important  branch  on  its 
course  ;  this,  the  vaginal  artery  (Fig.  277,  5)  is  analogous  in  every  respect  to 
the  vesico-prostatic  artery  ;  its  terminal  divisions  go,  not  only  to  the  middle 
portion  of  the  vagina,  but  also  to  the  body  of  the  uterus,  where  they 
anastomose  largely  with  the  branches  of  the  uterine  artery,  and  even  pass 
to  the  bladder  and  rectum. 

The  internal  pudic  artery  of  the  female,  as  in  the  male,  is  liable  to  nu- 
merous variations.  It  may  furnish  the  cavernous  artery,  or  only  the  dorsal 
artery  of  the  clitoris.  We  have  seen  the  vaginal  artery  come  from  the 
umbilical. 

3.  Suhsacral  or  Lateral  Sacral  Artery.     (Figs.  275,  2;  277,  6.) 

Rising  within  the  internal  iliac  artery,  at,  or  a  little  behind  the  lumbo- 
sacral articulation,  lying  above  the  peritoneum,  and  beneath  the  sacral 
foramina  and  the  large  nerves  passing  through  them,  this  vessel  is  directed 
backwards  and  arrives  near  the  posterior  extremity  of  the  sacrum,  where 


THE  INTERNAL  'ILIAC  ARTERIES.  541 

it  ends  in  two  branches :  the  iscldatic  and  lateral  coccygeal  arteries,  to  which 
must  bo  added  the  middle  coccygeal  artery,  usually  emitted  by  the  subsacral 
vessel  of  the  right  side. 

Collateral  Branches. — The  lateral  sacral  artery  distributes  on  its 
course  several  insignificant  ramuscules  destined  for  the  neighbouring  parts, 
and  four  spinal  branches  which  enter  the  vertebral  canal  by  the  inferior 
sacral  foramina,  and  leave  it  again  by  the  superior,  after  throwing  off  some 
divisions  to  the  posterior  extremity  of  the  spinal  cord  and  the  nerves  of 
the  tail ;  these  branches  ramify  in  the  muscles  lying  on  the  sacral  spine. 

Terminal  Branches. — 1.  Ischiatic  Artery. — It  crosses  the  ligament  of 
the  same  name  to  place  itself  under  the  superior  extremity  of  the  anterior 
portion  of  the  long  vastus,  passes  backwards  and  downwards,  and  divides 
into  several  branches  which  descend  into  the  substance  of  the  ischio-tibial 
muscles  (semimembranosis  and  semitendinosis),  to  beneath  the  ischial 
tuberosity.  These  branches  anastomose,  by  their  extremitiess,  with  the 
ascending  branches  from  the  the  femoro-popliteal  as  well  as  with  the 
divisions  of  the  obturator  and  deep  femoral  arteries. 

2.  Lateral  Coccygeal  Artery. — This  vessel  represents  the  continua- 
tion of  the  lateral  sacral  artery,  though  not  by  its  volume,  which  is  much 
less  than  the  ischiatic  artery,  but  in  its  direction.  It  proceeds  from  before 
to  behind,  for  the  whole  length  of  the  coccyx,  between  the  rudimentary 
vertebrae  of  that  region  and  the  depressor  muscles  of  the  tail,  gradually 
diminishing  in  volume,  and  detaching  on  its  course  a  series  of  collateral 
ramuscules  which  are  expended  in  the  muscles  and  integuments  of  the  tail. 

There  has  been  described  a  superior  lateral  artery,  a  branch  of  the  pre- 
ceding, and  which  passes  between  the  elevator  muscle  of  the  tail  and  the 
superior  face  of  the  coccygeal  vertebrae  ;  but  this  artery  never  exists  :  the 
superior  coccygeal  muscle  receives  its  blood  by  branches  analogous  to  the 
spinal  branches  of  the  intercostal,  lumbar,  and  sacral  artei'ies,  and  which 
emanate  from  the  lateral  coccygeal  artery  at  each  of  the  vertebral  bodies. 

3.  Middle  Coccygeal  Artery. — The  origin  of  this  vessel  iS  liable  to 
numerous  variations.  Ordinarily,  it  is  detached  from  the  right  subsacral 
artery,  in  common  with  the  lateral  coccygeal  of  the  same  side.  At  other 
times,  it  escapes  from  the  lateral  at  5  or  6  inches  from  its  origin.  In  a 
specimen  now  before  us,  it  arises  nearly  from  the  middle  of  the  subsacral 
artery.  And  it  may  also  proceed  from  either  the  left  sacral  or  the  corres- 
ponding lateral  coccygeal  artery. 

Whatever  maybe  its  point  of  emergence,  this  vessel  is  placed  "beneath  the  in- 
ferior face  of  the  caudal  vertebrae,  between  the  two  depressor  muscles  of  the  tail, 
crosses  t^ie  suspensory  ligament  of  the  rectum,  and  extends  to  the  extremity 
of  the  cuccyx,  distributing  ramuscules  to  right  and  left,  and  even  below. 

4.  Bio-muscular  or  llio-lumhar  Artery.     (Figs.  275,  14  ;  277,  8.) 

Immediately  after  clearing  the  inferior  face  of  the  lateral  angle  of  the 
sacrum,  and  even  often  before,  the  pelvic  trunk  gives  off  from  its  external 
side,  and  at  a  right  angle,  the  ilio-lumbar  artery,  which  passes  directly 
outwards,  behind  the  sacro-iliac  articulation,  between  the  iliacus  muscle  and 
the  bony  sm-face  covered  by  it,  and  emits  divisions  that  proceed  to  the 
above-named  articulation,  as  well  as  to  the  muscles  of  the  sublumbar 
region.  Near  the  angle  of  the  haunch,  it  terminates  in  several  branches, 
which  bend  upwards  on  the  external  border  of  the  ilium,  to  penetrate  the 
principal  gluteal  muscle,  or  the  muscle  of  the  fascia  lata  (tensor  vaginsa 
femoris.) 


542 


THE  ARTERIES. 


5.  Gluteal  Artery.     (Figs.  275,  13  ;  277,  7.) 

This,  the  most  voluminous  of  the  branches  emanating  from  the  pelvic 
trunk,  arises  opposite  the  preceding,  and  from  8-lOths  of  an  inch  to  li 
inches  behind  the  subsacral.      It  is  immediately  reflected  on  the  internal 

Fig.  275. 


LATERAL  VIEW  OF   THE   GENITO-URINARY   ORGANS   IN  THE  MALE. 

1,  Abdominal  aorta ;  2,  External  iliac  artery ;  3,  Common  origin  of  the  prepubic 
and  deep  femoral  arteries  ;  4,  Prepubic  artery  ;  5,  Posterior  abdominal  artery  ;  6, 
External  pudic  artery  ;  7,  Subcutaneous  abdominal  artery ;  8,  Anterior  dorsal 
artery  of  the  penis ;  9,  9,  Anterior  and  posterior  branches  of  that  artery  ;  10, 
Internal  iliac  artery;  11,  Last  lumbar  artery  ;  12,  Subsacral  artery;  lo,  Gluteal 
artery;  14,  Iliaco-muscular  artery;  15,  Umbilical  artery;  16,  Internal  pudic 
artery*  17,  Its  vesico-prostatic  branch;  18,  Iliaco-femoral  artery;  19,  Obturator 
artery;  20,  Artery  of  the  corpus  cavernosum  ;  21,  Posterior  dorsal  artery  of  the 
penis — a  branch  of  the  preceding ;  22,  Spermatic  artery  ;  23,  Posterior  mesen- 
teric artery;  c,  Termination  of  the  small  colon;  R,  Rectum  ;  s,  Sphincter  of  the 
anus ;  I,  Suspensory  ligament  of  the  penis  ;  I',  Suspensory  ligament  of  the  rectum  ; 
V,  Bladder ;  u,  Ureter ;  T,  Testicle ;  E,  Epididymis ;  D,  Deferent  canal ;  v,  Vesi- 
cul£e  seminales ;  p.  Prostate  ;  p,  Cowper's  gland  ;  r,  Crus  penis ;  s.  Ligament  of 
the  corpus  cavernosum. 

border  of  the  ilium,  and  emerges  from  the  pelvis  by  the  great  sciatic  notch, 
along  with  the  anterior  gluteal  nerves,  dividing  into  several  branches  which 
ramify  in  the  texture  of  the  great  and  small  gluteal  muscles. 

6.  Obturator  Artery.     (Figs.  275,  19  ;  232,  10.) 
This  vessel,  the  origin  of  which  has  been  already  indicated,  directs  its 


THE  INTERNAL  ILIAC  ARTERIES.  543 

course  backward  and  downward,  accompanied  by  a  satellite  vein  and  nerve, 
passes  beween  the  peritoneum  and  ilium  in  following  the  inferior  border 
of  the  internal  obturator  muscle,  and  finally  insinuates  itself  beneath  thai 
muscle  to  make  its  exit  from  the  pelvis  by  creeping  through  the  oval  (obtu- 
rator) foramen,  after  furnishing  a  constant  vesical  twig.  Placed  between  the 
external  obturator  muscle  and  the  inferior  face  of  the  ischium,  it  separates 
into  several  branches,  the  majority  of  which  descend  into  the  internal 
crural  and  ischio-tibial  muscles  (long  or  external  vastus,  and  the  semi- 
membranosis  and  semitendinosis),  anastomosing  with  the  ultimate  divisions 
of  the  ischiatic  and  deep  femoral  arteries.  Among  these  branches  there 
are  two  or  three  which  go  to  the  roots  of  the  penis,  and  enter  the  erectile 
tissue  of  the  cavernous  body  ;  one  of  them,  more  important  than  the  others  by 
its  volume,  is  designated  the  artery  of  the  corpus  cavernosum. 

Aktery  of  the  Corpus  Cavernosum  (Fig.  275,  20). — This  vessel 
creeps  on  the  inferior  face  of  the  ischium,  backwards  and  inwards,  reaches 
the  crus  penis,  and  i^ierces  it  by  several  branches,  after  supplying  some 
muscular  divisions  and  the  posterior  dorsal  artery  of  the  penis. 

The  latter  is  situated  on  the  dorsal  margin  of  the  penis,  passes  forward 
between  the  two  ligaments  attaching  that  organ  to  the  symphysis  pubis, 
and  proceeds  to  anastomose  with  the  posterior  branch  of  the  anterior  dorsal 
artery  (Fig.  275,  21.) 

7.  Biaco-femoral  Artery    (Figs.  275,  18  ;  277,  9.) 

Noticed  as  one  of  the  terminal  branches  of  the  pelvic  trunk,  the  iliaco- 
femoral  artery  only  exists  as  a  vessel  of  a  certain  volume  in  Solipeds.  In 
other  animals,  as  in  Man,  it  is  merely  an  insignificant  and  innominate  branch 
of  the  obturator  artery.  It  proceeds  outside  the  tendon  of  the  small  psoas 
muscle,  between  the  iliacus  and  the  neck  of  the  ilium,  which  it  passes  round 
obliquely,  above  the  origin  of  the  anterior  rectus  muscle,  to  descend  on  the 
external  side  of  the  latter,  and  plunge  into  the  mass  of  the  patellar  muscles, 
catering  them  between  the  anterior  rectus  and  vastus  externus,  after  sending 
out  some  branches  to  the  psoas,  gluteal,  and  muscles  of  the  fascia  lata. 

DIFFERENTIAL   CHARACTERS  OP  THE   INTERNAL   ILIAC   ARTERIES  IN   OTHER  THAN  SOLIPED 

ANIMALS. 

1.  Infernal  Iliac  Arteries  of  Ruminants. 

The  tenninal  extremity  of  the  aorta,  after  g:iving  off  the  external  iliac  arteries, 
bifurcates  to  constitute  the  pelvic  trunks,  and  in  the  angle  of  bifurcation  throws  out  a 
very  large  branch — the  saa-a  media — from  which  emanate  the  arteries  of  the  tail. 
This,  however,  is  not  the  only  important  peculiarity  to  be  noted  in  the  disposition  of  the 
pelvic  arteries.  Tlie  internal  iliac  artery  emits  at  its  origm  a  very  short,  but  very  large 
branch,  which  divides  to  form  the  nmhilical  artery^  and  an  enormous  uterine  artery,  that 
supplants,  to  a  great  extent,  the  utero-ovarian  artery ;  it  is  then  directed  backwards,  on 
the  internal  face  of  the  great  ischiatic  ligament,  crossing  the  direction  of  the  lumbo-sacral 
plexus.  In  its  course  it  furnishes  branches  resembling  the  iliaco-mitscular,  the  gluteal, 
and  the  ischiatic,  and  is  continued  about  the  middle  of  the  pelvis  by  the  internal  pudic 
artery,  which  terminates  by  forming  the  doisal  artery  of  the  clitoris,  after  distributing 
branches  to  the  rectum  and  the  genito-urinary  organs  lodged  in  the  pelvic  cavity. 

It  will  be  seen  from  this  description — which  refers  only  to  female  animals,  but  is 
easily  applicable  to  males — that  no  mention  is  made  of  an  iliaco-femoral  or  obturator 
artery.  This  is  because  these  two  vessels  are  entirely  absent  in  the  Sheep,  and  the  last, 
though  present  in  the. larger  Kuminants,  is  yet  in  a  very  rudimentary  state,  buih  being 
supplemented  by  the  deep  femoral,  whose  dimensions  are  considerable.  Neither  is 
the  lateral  sacral  or  suhsacral  artery  described,  as  it  is  also  wanting,  its  ischiatic  branch 
coming  directly  from  the  pelvic  trunk,  and  its  coccygeal  divisions  being  supplied  by  tha 
jniddle  sacral  arteiy. 


544 


THE  ARTERIES. 


276. 


2.  Internal  Iliac  Arteries  of  the  Pig. 

Two  single  branches,  originating  one  above  the  other,  arise  from  the  extremity  of 
the  aorta,  between  the  two  internal  iliac  arteries;  one  divides  almost  at  once  into  two 
lateral  branches,  which  go  to  right  and  left  bene  ath  the  iliacus,  and  are  the  representa- 
tives of  the  iliaco-muscular  arteries  of  the  Horse;   the  other,  or  sacra  media,  placed  in  the 

middle  line,  proceeds  backwards  on  the 
inferior  face  of  the  os  sacrum,  and  con- 
stitutes the  coccygeal  arteries,  after  giving 
off,  at  about  1.^  inches  from  its  origin,  two 
lateral  branches,  traces  of  the"  lateral 
sacral  arteries,  which  furnish  the  spinal 
ramuscules  of  the  sacral  region. 

The  iliac  trunk  near  its  origin  sends 
oif  the  timbilical  artery,  is  directed  back 
towards  the  great  sciatic  notch,  there 
detaches  gluteal  branches,  and  is  pro- 
longed beyond  the  notch  to  the  external 
sm-face  of  the  great  ischiatic  ligament  in 
forming  the  internal  pudic  artery. 

The  latter  emits,  before  leaving  the 
pelvic  cavity,  a  long  hemorrhoidal  artery, 
that  creeps  back  by  the  side  of  the  rectum, 
to  be  distributed  to  the  posterior  extre- 
mity of  that  intestine  and  the  adjoining 
genito-urinary  organs.  Without  the  pel- 
vis, it  abandons  some  gluteal  branches, 
the  most  considerable  and  posterior  of 
which  represent  the  ischiatic  artery  of 
Solipeds.  It  then  re-enters  the  cavity 
of  the  pelvis,  and  terminates  at  the  base 
of  the  penis  by  forming  the  cavernous 
and  dorsal  arteries  of  that  organ. 


3.  Internal  Iliac  Arteries  of  Carnivora. 

The  internal  iliac  arteries  in  the  Car- 
nivora result  from  the  bifurcation  of  an 
arterial  trunk,  that  prolongs  tlVe  aorta 
beyond  the  origin  of  the  external  iliacs, 
as  far  as  the  first  intersacral  articula- 
tion. 

The  pelvic  trunk  of  the  Dog  at  first 
transmits  the  umbilical  artery,  which  is 
remarkable  for  its  small  calibre,  and  the 
flexuosities  it  describes  before  reaching 
the  bladder. 

Then  the  internal  iliac  courses  for  1  or 
1 J  inches  behind,  and  to  the  inside  of,  the 
pelvi-crural  venous  trunk,  dividing  into 
two  brunches  at  the  entrance  to  the  pelvis. 

One  of  these  branches  goes  towards 
the    viscera    contained    in    the    pelvic 


ABDOMINAL  AORTA,  WITH  ITS  BRANCHES,  IN 
MAN. 

1,  Phrenic  arteries;  2,  Coeliac  axis;  3,  Gastric 
artery ;  4,  Hepatic  artery,  dividing  into  right 
and  left  hepatic  branches ;  5,  Splenic  artery, 
passing  outwards  to  the  spleen ;  6,  Supra- 
renal artery  of  right  side ;  7,  Right  renal 
artery  longer  than  the  left,  passing  outward 

to  right  kidney ;  8,  Lumbar  arteries ;  9,  Su-  cavity  ;  this  is  the  internal  pudic  artery. 
perior  mesenteric  artery;  10,  The  two  sper-  It  passes  backwards,  turns  the  ischial 
matic  arteries;  11,  Inferior  mesenteric  artery;  arch,  and  terminates  in  the  cavernous 
12,  Sacra  media  ;  13,  Common  iliacs  ;  14,  Right  and  dorsal  arteries  of  the  penis,  after 
internal  iliac ;  15,  External  iliac ;  16,  Epigas-  furnishing  vesical,  hemorrhoidal,  and 
trie  artery  ;  17,  Circumflexa  ilii ;  18,  Common  urethral  brandies,  as  well  as  the  uterine 
femoral  artery,  dividing  into  superficial  and  artery  of  the  female.  The  latter  is  very 
deep  femoral.  voluminous,  and  is  placed  in  the  sub- 

stance of  the  broad  ligament,  above  the 
email  curvature  of  the  uterine  cornu,  whence  it  is  directed   forward  to  the  ovary, 
where  it  meets  the  utero-ovarian  artery,  after  emitting  numerous  collateral  branches, 
remarkable  for  the  richness  of  the  vascular  network  they  form  in  the  walls  of  the  uterus. 
The  second  branch  of  the  internal  iliac  artery  resembles  the  subsacral  artery  and  its 


THE  EXTERNAL  ILIAC  ARTERIES.  545 

iscliiatic  branch  in  Solipeds;  it  escapes  from  the  pelvic  cavity  with  the  p-eat  sciatic 
nerve,  which  it  accompanies  to  behind  the  thigh,  where  it  is  expended,  after  giving  off 
on  its  course  spinal  and  gluteal  twigs.  It  is  not  this  branch  which  supplies  Ihe  coccy- 
geal arteries  ;  these  come,  as  in  the  Pig  and  Ruminants,  from  the  middle  sacral  artery. 

COMPARISON   OF  THE   INTERNAL   ILIAC  ARTERIES  IN   MAN   WITH   THOSE  OF   ANIMALS. 

The  aorta  in  3Ian  bifurcates  at  the  fourth  lumbar  vertebra  to  form  the  primitive  (or 
common)  iliac  arteries,  which  descend  to  each  side  of  the  margin  of  the  j^elvis,  where 
they  divide  into  two  branches,  the  internal  and  external  iliacs. 

The  internal  iliac,  or  hypogastric  artery,  passes  beneath  the  sacro-iliac  articulation, 
and  breaks  up  into  nine  or  eleven  branches  that  go  to  the  walls  of  the  pelvic  cavity,  or 
to  the  organs  contained  in  it.  Their  disposition  somewhat  resembles  that  of  Car- 
nivora ;  in  their  distribution  they  represent  the  various  branches  of  the  internal  iliac  of 
Solipeds.  'i'lius  we  find :  1,  An  umbilical  artery ;  2,  The  vesico-prosfatic  artery,  re- 
sembling tlie  branch  of  the  same  name  given  off  in  the  Horse  by  the  internal  pudic  ; 
3,  The  middle  hxmorrlwidal  artery,  that  passes  to  the  rectum  like  the  branch  of  the 
internal  pudic  ;  4,  The  ileo-lumbar  artery,  the  iliaco-muscular  of  Solipeds;  5,  The  lateral 
sacral  artery,  which,  behind,  joins  the  middle  sacral  instead  of  dividing,  as  in  the  Horse, 
into  ischiatic  and  lateral  coccygeal;  6,  The  obturator  artery;  7,  Gluteal  artery :  8,  Is- 
chiatic ;  9,  Internal  pudic,  that  terminates,  as  in  animals,  by  the  cavernous,  dorsalis 
penis,  and  the  transversa  perinei  arteries.  The  arterial  branches  of  the  rectum,  or 
inferior  hxmorrhoidal,  are  furnished  by  the  internal  pudic  artery. 

Abticle  IV. — External  Iliac  Arteries  or  Crural  Trunks.  (Fig.  277, 11.) 

The  external  branclies  of  tlie  terminal  quadrifurcations  of  the  posterior 
aorta,  the  crural  trunks  descend  on  the  sides  of  the  entrance  to  the  pelvic 
cavity,  in  describing  a  curve  downwards  and  forwards,  and  a  direction 
oblique  from  above  to  below,  before  to  behind,  and  within  outwards. 
Maintained  within  the  small  psoas  and  iliacus  muscles  by  the  peritoneimi 
covering  them,  they  are  bordered  posteriorly,  ard  to  the  inner  side,  by 
the  iliac  vein,  which  isolates  them  from  the  pelvic  trunk.  When  they 
arrive  at  the  anterior  border  of  the  pubis,  in  the  interstice  which  separates 
the  pectineus  from  the  long  adductor  of  the  leg,  each  is  prolonged  to 
the  thigh,  and  takes  the  name  of  femoral  artery  ;  and  thence  into  the  angle 
of  the  femoro-tibial  articulation,  where  it  receives  the  denomination  of 
popliteal  artery. 

Before  passing  to  the  description  of  these  two  vessels — continuations 
of  the  external  iliac  artery,  we  will  indicate  the  collateral  branches  which 
emanate  from  this  trunk  itself.  These  are  two  principal :  the  small 
testicular  or  uterine  {cremasteric),  and  the  circumflexa  ilii.  The  first  having 
been  already  described  (p.  534),  we  have  only  to  notice  the  second. 

Circumflex  Iliac  Artery  (Fig.  272,  11). — This  artery  commences  at 
an  acute  angle  near  the  origin,  and  in  front  of,  the  external  iliac ;  it 
sometimes  emerges  directly  from  the  abdominal  aorta.  It  is  directed 
outwards,  passes  between  the  peritoneum  and  the  lumbo-iliac  aponeurosis, 
and  arriving  at  the  external  border  of  the  great  psoas  muscle,  or  even 
beyond  that,  it  bifurcates.  The  anterior  branch  sends  its  ramifications  into 
the  transverse  and  small  oblique  muscles  of  the  abdomen,  where  they 
anastomose  with  the  abdominal  ramuscules  of  the  lumbar  and  intercostal 
branches ;  the  posterior  hifurcation,  after  giving  some  vessels  to  the  same 
muscles,  traverses  the  abdominal  wall  a  little  below  the  external  angle  of  the 
ilium,  in  passing  between  the  small  oblique  and  iliacus  muscles,  to  descend 
within  the  anterior  border  of  the  ilio-aponeuroticus  (tensor  vaginre)  muscle, 
and  expend  itself  in  front  of  the  thigh  by  subcutaneous  divisions. 


546 


DISTRIBUTION  OF  THE  EXTERNAL  AND 
INTERNAL   ILIAC   ARTERIES   IN   THE   MARE. 

1,  Abdominal  aorta;  2,  Internal  iliac  artery; 
3,  Common  origin  of  the  internal  pudic  and 
the  umbilical  arteries — the  latter  is  cut ;  4, 
Internal  pudic  artery ;  5,  Vaginal  artery ; 
6,  Lateral  sacral  artery ;  7,  Origin  of  the 
gluteal  artery,  which  springs  in  this  instance 
from  the  lateral  aacral,  a  circumstance  most 
frequently  observed  in  the  Ass ;  8,  Origin 
of  the  ilio-muscular  artery ;  9,  Origin  of 
the  iliaco-femoral  artery;  10,  Obturator  artery ;  11,  External  iliac  artery;  12,  Cir- 
cumflex iliac  artery,  cut;  13,  Femoral  artery;  14,  Common  origin  of  the  deep 
femoral  and  prepubic  arteries;  15,  Origin  of  the  anterior  great  muscular  artery;  16, 
Origin  of  the  saphena  artery,  cut;  17,  Innominate  branch;  18,  Popliteal  artery; 
19,  Femoro-popliteal ;  20,  Satellite  artery  of  the  groat  femoro-popliteal  nerve;  21, 
Posterior  tibial  artery;  22,  Its  communicating  branch  with  the  saphena;  23,  Ex- 
ternal plantar  artery  ;  24,  Satellite  artery  of  the  internal  plantar  nerve ;  25,  Digital 
artery. 


THE  EXTERNAL  ILIAC  ARTERIES.  547 

FEMORAL  ARTERY.   (Fig.  277,  13). 

The  femoral  artery,  a  prolongation  of  the  external  iliac,  which  changes 
its  name  on  leaving  the  anterior  border  of  the  pubis,  at  first  lies  beneath  the 
crui-al  arch,  beside  a  cluster  of  lymphatic  ghxnds,  in  the  space  comprised 
between  the  pectineal  muscles,  the  long  adductor  of  the  leg,  and  the  iliacus. 
From  this  interstice  it  descends,  accompanied  by  its  satellite  vein,  which  lies 
behind  it,  and  the  internal  saphena  nerve,  along  the  pectineus  and  vastus 
internus,  at  the  posterior  border  of  the  long  adductor  of  the  leg.  It  soon 
leaves  that  muscle,  however,  to  traverse  the  ring  formed  by  the  two  branches 
of  the  great  adductor  of  the  thigh  and  the  oblique  concavity  on  the  posterior 
face  of  the  femur,  and  reaches  the  superior  extremity  of  the  gastrocnemii, 
between  which  it  is  continued,  and  assumes  the  name  oi  popliteal  artery. 

On  its  course  the  femoral  artery  distributes  a  certain  number  of  collateral 
branches  to  the  adjacent  parts.  These  are  :  the  prepuhic,  deep  muscular, 
superficial  muscular,  the  small  muscular,  and  saphena  arteries. 

Preparation. — The  animal  being  placed  in  the  first  position,  and  the  limb  raised,  the 
skin  is  carefully  removed  from  the  inner  aspect  of  the  thinh,  the  external  generative 
organs  in  the  inguinal  region,  and  the  inferior  abdominal  wall.  Tlie  sapliena  vein  is 
first  to  be  exposed,  and  the  branches  of  the  artery  of  that  name  dissected ;  next,  the 
prepubic  artery,  which  is  to  be  sought  for  in  the  inguinal  canal,  and  its  branches 
prepared  by  dissecting  fiom  their  origin  to  their  termination.  The  excision  of  a  portion 
of  tlie  adductors  of  the  leg,  and  the  great  adductor  of  the  thigh  will  sufficiently  expose 
tlie  femoral  artery  and  its  other  collateral  branches. 

1.  Prepubic  Artery.     (rig^275,  4.) 

This  artery  originates  at  the  artificial  line  of  demarcation  which  separates 
the  external  iliac  from  the  femoral  artery,  at  the  superior  extremity  of  the 
latter.  It  therefore  emerges  from  that  vessel  at  the  anterior  border  of 
the  pubis,  and  never  alone,  but  always  with  the  deep  muscular  branch, 
by  means  of  a  common  and  generally  very  short  trunk,  which  springs  at 
an  acute  angle  from  the  inner  side  of  the  femoral  artery. 

The  prepubic  artery  traverses  the  crural  ring,  opposite  which  it  arises ; 
it  lies  on  the  anterior  face  of  Poupart's  ligament,  behind  the  neck  of  the 
vaginal  sheath,  and  after  a  very  short  course  separates  into  two  branches — 
the  posterior  abdominal  and  external  pudic  arteries. 

Posterior  Abdominal  Artery  (Epigastric  of  Man) — (Fig.  275,  5), — 
This  leaves  the  external  pudic  artery  at  an  acute  angle,  enters  the  femoral 
ring  by  crossing  the  direction  of  the  spermatic  cord,  places  itself  between  the 
small  oblique  and  transverse  muscles  of  the  abdomen,  passes  forward 
along  the  external  border  of  the  great  rectus  muscle,  and  finally  enters  the 
substance  of  that  muscle,  where  its  terminal  divisions  anastomose  with  those 
of  the  anterior  abdominal  artery.  The  numerous  collateral  branches  this 
artery  throws  off  on  its  track  principally  go  to  the  rectus  muscle,  or  the 
other  parts  composing  the  inferior  abdominal  wall,  the  skin  included ;  the 
superior  branches  communicate  with  the  circumflexa  ilii. 

The  position  this  artery  occupies  at  its  origin,  and  with  reference  to  the 
abdominal  ring,  is  worthy  of  remark ;  indicating,  as  it  does,  that  in 
strangulated  inguinal  hernia  division  of  the  ring  should  be  made  outwards, 
to  avoid  wounding  the  vessel. 

External  Pudic  Artery  (Fig.  275,  6). — This  artery  descends  at  first 
on  the  posterior  wall  of  the  inguinal  canal,  behind,  and  a  little  to  the  inside 
of,  the  spermatic  cord  ;  then,  having  passed  the  inferior  ring  of  the  canal,  it 


548  THE  ARTERIES. 

bifurcates  into  the  subcutaneous  abdominal  artery,  and  the  anterior  dorsal 
artery  of  the  penis. 

The  subcutaneous  abdominal  artery  is  directed  forward  on  the  superficial 
face  of  the  abdominal  tunic,  bordering  in  its  course  the  insertion  of  the 
suspensory  ligament  of  the  sheath.  Arriving  at  the  anterior  extremity 
of  that  ligament,  it  terminates  in  several  subcutaneous  divisions,  one  of 
which  is  inflected  beyond  the  umbilicus  to  anastomose  en  arcade  with 
a  similar  branch  from  the  opposite  artery.  It  gives  off  twigs  to  the  scrotum, 
sheath,  superficial  inguinal  glands,  skin,  &c.  (Fig.  275,  7). 

The  anterior  dorsal  artery  of  the  penis  gains  the  superior  border  of 
that  organ,  after  supplying  one  or  two  scrotal  branches,  and  separates  into 
two  portions  ;  one,  posterior,  meets  the  dorsal  cavernous  artery  of  the  penis 
and  anastomoses  with  it ;  the  other,  anterior,  longer,  more  voluminous,  and 
very  flexuous  during  retraction  of  the  penis,  follows  the  dorsal  border  of  the 
organ  to  its  anterior  extremity,  where  it  enters  the  erectile  tissue  that  forms 
this  part.  From  the  two  branches  of  this  anterior  dorsal  artery,  there  are 
given  off,  as  in  the  posterior  one,  ramuscules  which  penetrate  the  corpus 
cavernosura,  and  the  walls  of  the  urethra ;  they  give,  besides,  some  prasputial 
twigs  (Fig.  275,  8). 

In  the  FEMALE,  the  external  pudic  artery  offers  a  disposition  which,  if  not 
similar,  is  yet  analogous  to  that  just  indicated.  As  in  the  male,  this  vessel 
traverses  the  inguinal  canal,  and  after  leaving  it  divides  into  two  branches : 
one,  the  anterior,  or  subcutaneous  abdominal  artery,  the  other  the  posterior,  or 
mammary  artery.  The  last,  the  most  voluminous,  represents  the  dorsal 
artery  of  the  penis.  It  distributes  several  branches  to  the  mammary  tissue, 
and  is  prolonged  between  the"  thighs  by  a  perineal  branch,  which  terminates 
in  the  inferior  commissure  of  the  vulva,  after  giving  off  glandular  and 
cutaneous  branches. 

2.  Profunda  Femoris,  Great  Posterior  Muscular  Artery  of  the  Thigh,  or  Deep 

Muscular  Artery.     (Fig.  277,  14). 

Arising  in  common  with  the  prepubic  artery,  the  profunda  femoris  passes 
backward,  penetrates  between  the  iliacus  and  the  pectineus  muscles,  afterwards 
between  the  latter  and  the  external  obturator  muscle.  In  this  way  it  arrives 
beneath  the  deep  face  of  the  adductors  of  the  thigh,  when  it  becomes  inflected 
behind  the  femur,  and  disappears  in  the  substance  of  the  interaal  and 
posterior  crural  muscles  by  ascending  branches,  which  anastomose  with  the 
ischiatic  artery,  and  descending  and  internal  branches,  whose  terminal 
ramifications  open  into  those  of  the  obturator  artery. 

The  principal  twigs  of  the  coxo-femoral  articulation  are  derived  from  this 
vessel. 

3.  Superficial  Muscular,  or  Great  Anterior  Muscular  Artery.     (Fig.  277,  15.) 

Smaller  than  the  preceding,  and  commencing  opposite  to  it,  but  a  little 
lower,  this  artery  passes  downwards,  outwards,  and  forwards,  runs  between 
the  long  adductor  of  the  leg  and  the  musculo-tendinous  cone  which  terminates 
in  common  the  psoas  magnus  and  iliacus,  furnishes  some  ramuscules  to  these 
muscles,  dips  into  the  interstice  separating  the  vastus  internus  from  the 
anterior  rectus  of  the  thigh,  and  is  lost  in  the  mass  of  the  triceps  cruris. 

This  vessel,  therefore,  resembles  the  iliaco-femoral  artery,  which  we 
observed  to  enter  this  triceps  by  penetrating  between  the  anterior  rectus  and 
the  vastus  externus. 


THE  EXTERNAL  ILIAC  AUTEBIES.  549 

4.  Innominate  or  Small  Muscular  Arteries. 

The  femoral  artery  gives  off  on  its  course  numerous  small  branches 
destined  for  the  neighbouring  muscles,  though  too  diminutive  to  merit  parti- 
cular description.  One  of  these  furnishes  the  nutritive  artery  of  the  femur, 
the  largest,  perhaps,  of  all  the  arteries  supplying  bones.  Another  (Fig.  277, 
17)  sends  to  the  stifle  a  long  articular  branch,  analogous  to  the  great 
anastomoticus  of  Man,  which  descends  along  the  vastus  iuternus,  beneath  the 
adductors  of  the  leg,  at  the  interstice  which  separates  these  two  muscles. 

5.  Saphena  Artery.     (Fig.  277,  16.) 

This  artery,  remarkable  for  its  small  volume,  the  length  of  its  course,  and 
its  connections  with  the  vein  whose  name  it  bears,  is  destined  for  the  skin  on 
the  inner  side  of  the  thigh  and  leg. 

It  takes  its  origin  at  an  acute  angle,  from  nearly  the  middle  of  the  femoral 
artery,  either  alone  or  in  common  with  one  of  the  principal  innominate 
muscular  branches,  and  becomes  superficial  in  passing  into  the  interstice  of 
the  two  adductors  of  the  leg,  or  in  traversing  one  of  these,  usually  the  short 
one  or  gracilis.  It  lies  on  the  surface  of  this  muscle,  beside  the  saphena 
vein,  and  bifurcates  at  the  angle  of  union  of  the  two  roots  which  constitute 
that  vessel.  One  of  the  branches  accompanies  the  anterior  vein  to  nearly 
the  lower  third  of  the  leg  ;  the  other  follows  the  posterior  vein,  and  usually 
anastomoses  in  the  hollow  of  the  hock,  above  the  calcaneus,  with  a  branch 
from  the  posterior  tibial  artery,  and  which  also  communicates  with  one  of  the 
branches  of  the  femoro-popliteal  artery. 

Popliteal  Artery.     (Fig.  277,  18.) 

Preparation. — The  preparation  which  has  served  for  1  he  study  of  the  femoral  artery 
being  nearly  arranged  as  in  figure  277,  remove  from  it  the  internal  gastrocnemius  and 
popliteus  muscles. 

The  above  name  is  given  to  the  continuation  of  the  femoral  artery. 
This  vessel  follows  a  descending  direction  behind  the  femoro-tibial  articula- 
tion, between  the  two  gastrocnemii  muscles,  insinuates  itself  beneath  the 
popliteus,  and  bifurcates  at  the  peroneal  arch  after  a  course  of  from  6  to 
8  inches,  to  form  the  posterior  and  anterior  tibial  arteries. 

The  popliteal  artery  emits  on  its  track  :  1,  The  femoro-popliteal  artery  ; 
2,  Articular  branches ;  3,  Muscular  branches  chiefly  destined  to  the 
gastrocnemii  muscles,  of  which  it  is  necessary  to  particularise  one  long 
division  that  descends  within  the  perforatus,  in  company  with  the  great 
femoro-popliteal  nerve,  to  terminate  superficially  near  the  tendo-Achillis, 
where  it  anastomoses  with  a  recurrent  branch  of  the  posterior  tibial 
artery  (Fig.  277,  20). 

The  femoro-popliteal  artery  is  the  only  one  of  these  collateral  branches 
deserving  particular  mention.  Its  origin  indicates  the  limit  of  the  femoral 
and  popliteal  arteries,  as  it  is  detached  at  a  right  angle  below  the  ring  of 
the  great  abductor  of  the  thigh,  at  the  intermediate  point  of  these  two 
vessels.  Placed  between  the  semimembranosis  and  semitendinosis 
muscles  on  the  one  part,  and  the  long  vastus  on  the  other,  this  vessel  is 
directed  from  before  to  behind,  and  arrives  at  nearly  the  posterior  border  of 
the  buttock,  where  it  terminates  in  subcutaneous  branches,  after  emitting 
descending  and  ascending  branches.  Among  the  first  of  these,  which  are 
principally  destined  to  the  gastrocnemii  muscles,  sometimes  exists  the 
38 


550  THE  ARTERIES. 

satellite  branch  of  the  sciatic  nerve,  and  a  thin  twig  which  descends  with 
the  external  saj^hena  nerve  into  the  hollow  of  the  hock,  where  it  meets,  like 
the  preceding,  a  branch  of  the  posterior  tibial  artery.  Several  of  the 
ascending  branches  pass  along  tlie  great  femoro-popliteal  nerve,  and  all 
anastomose  either  with  the  deep  femoral,  or  with  the  ischiatic  arteries  in  the 
substance  or  interstices  of  the  ischio-tibial  muscles  (Fig.  277,  19). 

TERMISAL  BRANCHES  OF  THE  POPLITEAL  ARTERY. 

1.  Posterior  Tibial  Artery.     (Fig.  277,  21.) 
Treparation.— Follow  the  indications  furnished  by  figure  277. 

At  first  situated  deeply  behind  the  tibia,  beneath  the  popliteal  muscles 
and  the  oblique  and  deep  flexors  of  the  phalanges,  this  artery  descends 
towards  the  hollow  of  the  hock,  becoming  gradually  more  and  more  super- 
ficial, and  lying  below  the  tibial  fascia,  behind  the  tendon  of  the  oblique 
flexor  muscle,  along  with  its  satellite  vein.  Arriving  at  the  apex  of  the 
OS  calcis,  it  crosses  the  precited  fascia,  describes  an  S  curve,  and,  along 
with  the  sciatic  nerve,  passes  beneath  the  tarsal  arch;  at  the  astragalus  it 
separates  into  two  terminal  branches— the  plantar  arteries. 

Collateral  branches. — We  cite:  1,  Numerous  branches  destined  to  the 
posterior  deep  tibial  muscles ;  2,  The  medullary  artery  of  the  tibia  ;  3,  The 
tarsal  articular  arteries,  a  principal  of  which,  with  a  large  venous  arch, 
passes  under  the  perforans,  near  the  inferior  extremity  of  the  tibia,  to  be 
distributed  outside  the  tarsus  by  descending  ramuscules  and  ascending  twigs, 
which  extend  as  far  as  the  gastrocnemii  tendons ;  4,  A  superficial  ascending 
branch,  arising  ordinarily  from  the  second  inflexion- of  the  S  curvature 
formed'  by  the  artery  at  its  lower  extremity,  situated  in  the  hollow  of  the 
hock,  anastomosing  with  the  saphena  artery,  as  well  as  with  the  satellite 
popliteal  branch  of  the  sciatic  nerve,  and  whose  ramifications,  nearly  all 
subcutaneous,  are  scattered,  within  and  without,  on  the  sides  of  the  hock 
and  the  inferior  extremity  of  the  thigh. 

Terminal  branches.. — The  two  terminal  branches  of  the  posterior  tibial 
artery  are  slender  vessels,  vestiges  of  the  plantar  arteries  in  Man.  Lying  on 
the  outer  side  of  the  synovial  tendinous  sheath  lining  the  tarsal  groove,  they 
are  placed,  one  within,  the  other  without,  the  perforans  tendon,  and  descend 
along  with  the  plantar  nerves  to  the  upper  extremity  of  the  metatarsus, 
where  they  leave  the  nerves,  each  to  anastomose  with  the  perforating  pedal 
artery,  and  form  a  kind  of  deep  arcade  across  the  upper  extremity  of  the 
suspensory  ligament  of  the  fetlock  :  that  is,  from  the  post-metatarsal  fibrous 
band  which  represents  the  interosseous  plantar  muscles  of  tetradactylous  or 
pentadactylous  animals. 

In  their  course,  these  plantar  arteries  only  distribute  some  insignificant 
ramuscules  to  the  tarsal  articulations. 

From  the  convexity  of  the  arch  they  form  in  uniting  with  the  perforating 
pedal  artery,  arise  four  long  descending  branches:  1,  Two  superficial, 
innominate  and  very  fine  twigs  accompanying  the  plantar  nerves,  and 
creeping  by  the  side  of  the  flexor  tendons  to  the  sesamoid  groove,  where 
they  inosculate  with  the  collaterals  of  the  digit  (Figs.  277,  24;  278,  8); 
2.  Two  deep  branches  constituting  the  plantar  interosseous  arteries,  dis- 
tinguished into  external  and  internal.  The  first  is  only  an  extremely  fine 
vascular  thread,  very  uncertain  in  its  disposition,  and  possesses  no  other 
importance   in   Solipeds   than    representing,    in    a   rudimentary    state,    an 


TEE  EXTERNAL  ILIAC  ARTERIES.  551 

artery  wliicli  is  of  considerable  size  in  other  animals.  Placed  witliin  the 
external  metatarsal  bone,  it  anastomoses,  by  its  inferior  extremity,  with  a 
branch  of  the  metatarsal  pedal  artery.  The  internal  interosseous  plantar  artery 
may  be  considered,  if  we  would  neglect  the  study  of  analogies,  as  the  continua- 
tion of  the  perforating  jjedal  artery,  which  it  rivals  in  volume.  It  descends 
to  the  external  side  of  the  internal  metatarsal  bone,  beneatli  the  margin  of  the 
suspensory  ligament  of  the  fetlock,  and  terminates  a  little  above  the  tubercle 
of  the  external  metatarsal  bone,  in  uniting  at  a  very  acute  angle  with  the 
metatarso-pedal  artery.  It  gives  oflf  on  its  tract :  the  medullary  branch  of 
the  princijml  metatarsal  bone ;  a  small  branch  to  the  external  interosseous 
artery ;  several  ramuscules  which  transversely  cross  the  jwsterior  border 
of  the  internal  metatarsal  bone  to  supply  the  cellular  tissue,  the  skin,  and 
the  tendons  applied  to  the  median  metatarsal  bone. 

2.  Anterior  Tibial  Artery.     (Fig.  278,  1.) 
Preparation. — Expose  the  artery  by  removing  the  anterior  muscles  of  the  leg. 

The  anterior  tibial  artery  is  the  largest  of  the  two  branches  terminating 
the  popliteal  trunk.  It  traverses  the  tibia^.  or  tibio-peroneal  arch,  and,  with 
its  satellite  veins,  places  itself  on  the  anterior  aspect  of  the  tibia,  down 
which  it  passes  by  following  the  deep  face  of  the  flexor  muscle  of  the 
metatarsus.  On  reaching  the  front  of  the  tibio-tarsal  articulation,  it  loses 
its  name  and  takes  that  of  the  pedal  artery. 

The  anterior  tibial  artery  gives  oif  a  great  number  of  collateral  branches, 
which  are  principally  distributed  among  the  tibial  muscles.  One  of  them, 
descending  along  the  fibula,  beneath  tlie  lateral  extensor  muscle  of  the 
phalanges,  clearly  represents  a  trace  of  the  peroneal  artery  of  Man. 

3.  Pedal  Artery.     (Fig.  278, 1'.) 

A  continuation  of  the  anterior  tibial  artery,  whoso  name  changes  on  its 
arrival  in  the  region  of  the  foot,  the  pedal  artery  courses  downward  over  the 
anterior  face  of  the  tibio-tarsal  articulation,  by  bending  slightly  outwards, 
and  passing  beneath  the  cuboid  branch  of  the  flexor  muscle  of  the  metatarsus. 
At  the  second  row  of  tarsal  bones  it  divides  into  two  branches,  which  we 
will  designate  the  perforatincj  pedal,  and  the  metatarso-pedal  arteries,^  the 
latter  continued  inferiorly  by  the  digital  arteries,  or  collaterah  of  the  dir/it. 

The  collateral  branches  emanating  from  this  vessel  are  all  articular 
cutaneous,  and  of  no  importance.^ 

Perforating  Pedal  Artery. — It  crosses  the  tarsus  from  before  to 
behind,  by  passing,  with  a  venous  branch,  into  the  canal  between  the 
cuboid,  scaphoid,  and  great  cuneiform  bones ;  it  then  joins  the  arch  formed 
by  the  anastomoses  of  the  two  plantar  arteries — terminal  divisions  of  the 
posterior  tibial  (Fig.  278,  2). 

Metatarso-pedal    or    Collateral  Artery   of    the    Cannon.^— Much 

'  The  vessel  we  have  here  named  the  perforating  pedal  artery  is  only  the  like 
termination  of  the  same  artery  in  Man.  The  metatarso-pedal  artery  ought  to  be  regarded 
as  the  representative  of  one  of  the  dorsal  interossei  arteries,  because  of  its  position  in  the 
interstice  of  the  middle  and  external  lateral  metatarsal  bones.  The  dorsal  interstice  of 
the  inner  side  also  lodges  an  interosseous  branch,  usually  supplied  by  the  external 
plantar  artery  ;  but  its  diameter  is  so  diminished  that,  in  order  to  avoid  complexity  by 
introducing  an  ahnost  useless  element  into  the  didactic  description  of  the  posterior 
tibial  artery,  we  have  thought  it  our  duty  to  neglect  its  indication. 

"  One  of  these  may  be  regarded  as  the  analogue  of  the  dorsalis  pedis  of  Man. 

^  Rigot  has  designated  this  artery — we  do  not  know  why — the  superficial  plantar  artery. 


552 


THE  ARTERIES. 


Ficr.  278. 


larger  than  the  preceding,  this  vessel  (Fig.  278,  3)  may  be  considered  as  a 
continuation  of  the  primitive  pedal  artery.  It  is  lodged  at  first  in  the 
fissure  situated  outside  the  middle  metatarsal  bone,  in  front  of  the  external 
metatarsal  bone,  and  afterwards  passes  between  these  two  bones,  above  the 
tubercle  terminating  the  latter,  reaching  the  posterior  face  of  the  first, 
between  the  two  inferior  branches  of  the  suspensory 
ligament,  above  the  sesamoid  groove,  where  the  vessel 
bifurcates  to  form  the  collateral  arteries  of  the  digit. 

The  collateral  artery  of  the  cannon  receives,  a  short 
distance  above  this  terminal  bifurcation,  the  internal 
plantar  interosseous  artery. 

On  its  course  it  gives  off:  1,  Numerous  anterior 
ramuscules  for  the  cellular  tissue,  tendons,  ligaments, 
and  the  skin  on  the  anterior  face  of  the  metatarsus  aud 
fetlock ;  2,  Some  thin  posterior  divisions,  one  of  which 
ascends  within  the  external  metatarsal  bone  to  anastomose 
with  the  external  plantar  interosseous  artery,  after  fur- 
nishing several  ligamentous,  tendinous,  and  cutaneous 
ramuscules  in  the  posterior  metatarsal  region. 

Digital  Aeteries,  or  Collateral  Arteries  of  the 
Digit  (Figs.  277,  25;  278,  4;  283,  11).— Remarkable 
for  their  volume,  these  arteries  carry  blood  to  the 
keratogenous  apparatus  enveloping  the  ungual  phalanx, 
and  from  this  destination  derive  such  importance  that 
they  deserve  a  detailed  study. 

Origin. — The  digital  arteries  succeed  the  terminal 
extremity  of  the  collateral  of  the  cannon,  and  separate 
from  one  another  in  forming  an  acute  angle  below  the 
sesamoid  venous  arch,  above  the  fetlock  joint,  between 
the  two  branches  of  the  suspensory  ligament,  behind  the 
inferior  extremity  of  the  principal  metatarsal  bone,  and 
in  front  of  the  flexor  tendons  of  the  phalanges. 

Course  and  Belations. — These  vessels  descend,  one  to 
the  right,  the  other  to  the  left,  from  the  lateral  parts  of 
the     metacarpo-phalangeal     (and     metatarso-phalangeal) 
articulation  to  tJae  internal  face  of  the  basilar  process, 
PRINCIPAL  ARTERIES  -^vhere  they  bifurcate  to  fonn  the  plantar  and  preplantar 

AND  VEINS  OF  THE  7         j       • 

POSTERIOR  FOOT,      ungueol  urtenes 

1  Anterior  tibial  ar-  " -'"'^  *"®  whole  of  this  course,  it  (the  digital  artery) 

'  tery ;  1',  Pedal  ar-  follows  the  track  of  the  flexor  tendons,  on  whose  margin 

tery ;    2,  Perfora-  it  rests,  and  where  it  is  maintained  by  loose  connective 

ting  pedal  artery ;  tissue.    Behind,  it  is  flanked  by  the  plantar  nerve,  which 

3,  Metatarso-pedal,  '  J  r  j 

or  collateral  artery . 

of  the  Ciinnon ;    4, 

Digital  artery  ;    5,  It  would  have  been  better  to  have  allowed  it  to  retain  the  name 

Anterior  tibial  ar-  given  to  it  by  Girard— tlie  lateral  artery  of  the  cannon.     This  is 

tery;    6,  Posterior  not  the  only  instance  in  which  the  attempts  of  Rigot  to  conform  the 

root  of  the  internal  nomenclature  of  the  arteries  to  that  of  anthropotomists  has  proved 

saphena    vein  ;    7,  unfortunate,  as  he  has  not  always  succeeded    in  finding  in  the 

Origin  of  the   ex-  Horse  the  real  representatives  of  arteries  in  Man.     The  aim  of 

ternal  saphena  vein;  this  work  does  not  allow  us  to  discuss  the  vicious  determinations 

8, 9, 10,  Metatarsal  and  denominations   of  Rigot   every   time   we   meet   them.      We 

veins;    11,  Digital  are  content   to  change  them,  purely  and   simply,  leaving  to  the 

vein  ;    12,   Venous  judgment  of  the  reader,  should  this  matter  interest  him,  the  task 

plexus  of  the  foot,  of  deciding  if  we  are  right. 


THE  EXTERNAL  ILIAC  ARTERIES.  553 

covers  a  portion  of  its  surface,  enlaces  it  with  numerous  filaments,  and  is  so 
closely  associated  with  it  in  all  its  flexuosities  as  to  form  but  a  single  cord 
with  it. 

'■  In  front,  it  is  margined,  though  for  a  short  distance,  by  its  satellite 
vein,  which  for  the  whole  of  its  track  rests  on  the  lateral  faces  of  the  t^'o 
first  phalanges. 

"  At  its  iij)per  part,  near  its  origin,  and  on  the  lateral  portions  of  the 
metacarpo-phalangeal  articulation,  the  digital  artery  is  crossed  from  behind 
to  before  by  the  anterior  branch  of  the  plantar  nerve,  and  it  is  covered  for 
the  whole  of  its  extent  by  the  fascia  which  continues  the  proper  tunic  of  the 
plantar  cushion,  whose  lateral  ligamentous  band  cuts  its  direction  obliquely 
from  above  to  below  and  behind  to  before,  at  the  middle  portion  of  the  first 
phalanx.'" 

Collateral  divisions. — These  are :  1.  At  the  fetlock,  nimierous  fine 
branches  distributed  to  the  metacarpo-phalangeal  articulation,  but  par- 
ticularly to  the  sesamoid  sheath,  and  the  tendons  lodged  in  it. 

2.  To  the  environs  of  the  upper  extremity  of  the  first  phalanx,  a  slightly 
ascending  and  sometimes  voluminous  twig,  for  the  tissue  of  the  ergot  (the 
horny  tubercle  behind  the  fetlock). 

3.  Towards  the  middle  of  the  same  bone,  the  vessel  named  by  Percivall 
the  perpendicular  artery,  and  correctly  so,  for  it  arises  at  a  right  angle  from 
the  digital  artery  to  divide  almost  immediately  afterwards  into  two  series  of 
ramifications — anterior  and  posterior.  The  anterior  branches  are  in  nearly 
every  instance  two  principal :  one  ascending,  passing  beneath  the  check 
band  of  the  extensor  tendon,  and  climbing  to  the  capsular  ligament  of  the 
fetlock  joint  to  meet  the  arterial  divisions  furnished  directly  to  that  ligament 
by  the  collateral  artery  of  the  cannon  ;  the  other  descending,  which  reaches 
the  side  of  the  second  phalanx,  where  its  ramuscules  anastomose  with  the 
coronary  circle  and  the  circumflex  artery  of  the  coronary  substance  (cushion). 
The  posterior  ramifications  consist  most  frequently  of  two  principal  branches, 
— one  ascending,  the  other  descending  :  these  insinuate  themselves  between 
the  flexor  tendons  and  the  sesamoid  ligaments,  to  be  distributed  to  these 
organs,  but  especially  to  the  synovial  membrane  lining  the  large  sesamoidean 
sheath.  Sometimes  it  is  seen  to  arise  alone  from  the  digital  artery.  It  must 
here  be  noted,  that  the  divisions  furnished  by  the  anterior  branches  of  this 
perpendicular  artery  communicate  with  those  of  the  opposite  side  in  front 
of  the  first  phalanx,  either  above  or  below  the  principal  extensor  of  the 
digit  ^  and  that  the  posterior  branches  exhibit  a  series  of  analogous  anasto- 
moses. The  body  of  the  first  phalanx  is  therefore  enveloped  on  every  side 
by  an  arterial  plexus. 

4.  At  different  elevations  on  the  first  and  second  phalanges,  several 
tendinous  and  cutaneous  twigs,  which  are  of  no  importance. 

5.  The  artery  of  the  plantar  cushion,  which  (irises  at  the  superior  border 
of  the  lateral  cartilage,  is  directed  obliquely  backward  and  downward,  and 
placed  within  the  posterior  border  of  that  cartilage,  to  be  distributed  to 
the  middle  portion  of  the  complementary  apparatus  of  the  third  jihalanx.  as 
well  as  to  the  villous  tissue  and  the  coronet.  The  branch  expended  in  the 
latter  sometimes  proceeds  directly  from  the  digital  artery ;  it  is  a  very 
remarkable  vesssel,  is  inflected  from  before  to  behind,  crossing  the  posterior 
border  of  the  pedal  cartilage,  creeping  on  the  internal  face  or  in  the  texture 
of  the  skin,  a  little  above   the  coronet,  parallel  with  that  portion  of  the 

*  H.  Bouley. — '  Traite  de  rOrganisation  du  Pied  du  Cheval.'    Paris,  1S51. 


554  THE  ARTERIES. 

keratogenous  apparatus,  and  terminates  by  anastomosing  witli  a  branch  of 
the  artery  now  to  be  noticed. 

6.  The  coronary  circle,'^  formed  by  two  transverse  branches — one  anterior, 
the  other  posterior,  springing  at  a  right  angle  from  the  digital  artery,  under 
the  cartilaginous  plate  of  the  os  pedis — passes  around  the  coronary  bone  to 
meet  the  analogous  branches  of  the  opposite  artery,  to  anastomose  with  them 
directly  and  by  inosculation.  The  coronary  circle  therefore  presents  two 
distinct  portions:  one  posterior,  jilaced  above  the  superior  border  of  the  small 
sesamoid,  beneath  the  perforans  tendon  ;  the  other  anterior,  more  extensive 
and  volimiinous,  covered  on  the  sides  by  the  lateral  cartilages  of  the  foot, 
and  in  its  front  or  middle  part  by  the  expansion  of  the  anterior  extensor 
tendon  of  the  phalanges. 

The  collateral  ramuscules  furnished  by  the  posterior  part  of  the  circle 
are  small,  few,  and  of  no  interest. 

Among  the  branches  arising  from  the  anterior  portion,  there  is  only  a 
single  pair  of  arteries  to  be  noted,  which  are  remarkable  for  their  mode 
of  "distribution  and  their  volume.  They  originate  near  the  border  of 
the  extensor  tendon,  and  immediately  divide  into  two  divergent  branches : 
one  the  internal,  which  passes  across  that  tendon  to  anastomose  with  the 
homologous  branch  of  the  opposite  side ;  the  other,  external,  passes  backward 
to  meet  the  cutigeral  branch  furnished  by  the  artery  of  the  i)lantar 
cushion,  and  joins  that  vessel.  From  this  disposition  results  a  very  fine 
superficial  vascular  arch  around  the  coronet,  which  is  well  named  the 
circumflex  artery  of  the  coronary  cushion ;  it  is  situated  a  little  above  the 
cutidural  artery,  beneath  the  skin  of  the  coronet,  and  looks  as  if  incrusted 
in  that  membrane ;  by  its  two  extremities  it  rests  on  the  arteries  of  the 
plantar  cushion,  and  is  fed  by  the  two  principal  vessels  of  the  coronary 
circle ;  while  it  furnishes  ascending  anastomosing  ramuscules  to  the  inferior 
divisions  of  the  perpendicular  artery,  as  well  as  numerous  descending 
branches  passing  into  the  coronary  cushion  and  the  laminal  tissue  of  the 
foot. 

Such  is  the  ordinary  disposition  of  the  coronary  circle  and  its  super- 
ficial arch — the  circumflex  artery  of  the  coronary  substance  ;  though  it  varies 
much  in  different  animals,  and  even  in  the  feet  of  the  same  animal.  To  attempt 
to  describe  here  the  variations  we  have  seen  would  be  supererogatory,  and  we 
may  limit  ourselves  to  saying  that  these  varieties  were  almost  exclusively 
confined  to  the  origin  of  the  branches  composing  these  two  circular  vessels 
and  their  manner  of  arrangement,  without  modifying  in  any  way  the  general 
disposition  of  the  circles.^ 

Terminal  divisions.— These  are,  as  has  been  already  mentioned,  the  pZantor 
and  i^replantar  ungual  arteries.^ 

a.  The  preplantar  ungual  artery  is  the  smallest  of  these  two  terminal 
branches.  Situated  at  first  inside  the  basilar  process  of  the  third  phalanx, 
it  turns  round  this  to  traverse  the  notch  which  separates  this  process  from 
the  retrossal  eminence,  is  lodged  with  a  satellite  nerve  in  the  preplantar 

1  So  named  because  it   ncircles  the  coronet. 

-  We  may  notice  here  one  of  these  variations,  which  is  somewhat  frequently  met 
with  in  the  anterior  limb.  This  consists  in  the  anterior  descending  branch  of  the 
perpendicular  artery  uniting  at  its  terminal  extremity  with  the  circumflex  artery  of  the 
coroniiry  substance,  which  it  concurs  to  form. 

•*  In  all  treatises  on  anatomy  these  vessels  are  simply  designated  the  plantar  and 
preplantar  arteries.  "We  have  added  the  epithet  ungueal  to  distinguish  these  arteries 
from  tlie  properly  so-cailel  plantar  branches  — the  terminal  divisions  of  the  posterior 
tibial  artery. 


TEE  EXTERNAL  ILIAC  ARTERIES.  555 

fissure,  wliicli  it  crosses  from  before  to  behind,  and  terminates  near  its 
anterior  extremity  by  several  divisions  that  bury  themselves  in  the  os 
pedis.  In  its  course,  it  distributes :  1,  Before  passing  into  the  sub-basilar 
notch,  a  deep  retrograde  branch  destined  to  the  bulb  of  the  heel  and  the 
villous  tissue;  2,  Ltnmediately  after  leaving  that  notch,  a  second  retrograde 
branch,  whose  divisions  pass  backward,  behind  the  great  circumflex  artery  of 
the  pedal  bone  ;  3,  During  its  passage  in  the  preplantar  fissure,  several  ascend- 
ing and  descending  branches  which  ramify  in  the  lamiual  tissue ;  the  first 
anastomose  with  the  descending  divisions  of  the  coronary  circle  and  the 
cu-cumflex  artery  of  the  coronary  cushion. 

h.  The  ■plantar  ungual  artery  ought  to  ba  regarded  as  a  continuation  of 
the  digital  artery,  because  of  its  volume  and  direction.  Lodged  at  first, 
with  a  fine  nervous  branch,  in  the  plantar  fissure,  it  afterwards  enters  the 
canal  of  the  same  name,  and  thus  penetrates  into  the  semilimar  sinus  of  the 
OS  pedis,  where  it  anastomoses  by  inosculation  with  the  opposite  artery, 
forming  a  deep  vascular  arcade  which  we  designate  the  plantar  arcade  or 
circle,  or,  after  M.  H.  Bouley,  the  semilunar  anastomosis  (Fig.  283,  12). 

Two  orders  of  branches  emanate  from  the  convexity  formed  by  this 
anastomotic  loop.  The  ascending  order  "  irradiate  in  the  spongy  framework 
of  the  third  phalanx,  and  like  so  many  hair-roots,  escape  by  numerous  open- 
ings fi'om  its  anterior  face,  where  they  form  a  very  intricate  plexus  by  anasto- 
mosing, in  the  texture  of  the  laminal  tissue,  with  the  extreme  divisions  of  the 

anterior  branch  of  the  digital  artery  and  those  of  the  coronary  circle 

It  is  to  these  divisions  that  Spooner  has  given  the  name  of  anterior  laminal 
arteries." — H.  Bouley. 

The  descending  order,  much  more  considerable,  named  by  Spooner  (W.  C, 
of  Southampton)  the  inferior  communicating  arteries,  arise  at  a  right  angle  from 
the  anterior  circumference  of  the  semilunar  anastomosis,  traverse  in  a  diver- 
gent manner  the  tissue  of  the  phalanx,  and  make  their  exit  by  the  large  fora- 
mina situated  a  little  above  the  inferior  border  of  the  bone,  where  they  furnish 
a  multitude  of  ascending  ramuscules  which  concur  to  form  the  arterial  net- 
work of  the  laminal  tissue.  "  Then  they  anastomose  transversely  by  a 
succession  of  little  arcades  which  are  thrown  from  one  to  the  other,  and  in 
.this  way  give  rise  to  a  great  circumflex  canal  which  follows  the  contour  of  the 
parabolic  curve  exhibited  by  the  thin  border  of  the  os  pedis,  on  its  inferior 
face  " — H.  Bouley.  This  vascular  ai'cade,  which  we  purpose  naming  the  in- 
ferior circumflex  artery  of  the  foot,  to  distinguish  it  from  the  circumflex  of  the 
coronary  cushion,  is  joined  by  its  extremities  to  the  preplantar  artery,  in  the 
same  manner  that  the  latter  circiunflex  is  united  to  the  artery  of  the  plantar 
cushion.  From  its  concavity  it  throws  ofl'  some  fourteen  or  fifteen  con- 
vergent branches,  w  hich  are  destined  to  the  villous  tissue  of  the  sole. 

DIFFERENTIAL   CHARACTERS    OF  THE   EXTERNAL   ILIACS    IS  OTHER  THAN   SOLIPED   ANIMALS. 

1.  External  Iliac  Arteries  of  Ruminants. 

In  the  Ox,  apart  from  the  considerable  volume  of  the  great  muscular  arteries  of  tbe 
thigh,  the  crural  trunk,  as  well  as  the  femoral  and  popliteal  arteries  continuing  it, 
comport  themselves  almost  tlie  same  as  in  the  Horse.  It  is  only  when  we  reach  the 
foderior  and  anterior  tibial  arteries  that  we  find  some  peculiarities  worthy  of  notice. 

Posterior  tibial  artery. — Much  more  voluminous  than  that  of  Solipeds,  this  artery  f.  .Hows 
the  same  track,  and  terminates  in  an  analogous  manner  :  forming  at  its  lower  extremity 
two  plantar  branches,  which  anastonioje  witli  the  perforating  pedal  artery  behind  the 
superior  extremity  of  the  princiiial  metatarsal  Ivme.  and  beneath  tue  suspensory  ligament. 
But  these  two  branches  are  fir  from  possessing  the  s-ame  volume;  the  internal  is  in- 
comparably the  largest,  and  appears  to  be  the  dii-ect  continuation  of  the  pos'eriijr  t.bial 
artery. 


556  THE  ARTERIES. 

From  this  anastomosis  results,  as  in  the  Horse,  two  series  of  metatarsal  branches — a 
profound  and  a  superficial. 

The  profound  branches,  two  or  three  in  number,  form  on  the  posteiior  face  of  the 
metatarsal  bone,  below  the  suspensory  ligament,  the  posterior  interosseis,  mixed  witli 
two  or  three  reticuhited  venous  branches,  and  anastomose  by  their  inferior  extremity 
with  a  perforating  branch  of  the  collateral  of  the  cannon. 

Tlie  superficial  branches,  similar  to  those  which  accompany  the  plantar  nerves  in  the 
Horse,  are  of  very  unequal  calibre:  tlie  external  is  so  rudimentary  that  it  often  escapes 
dissection ;  the  internal  in  reality  continues  the  plautar  artery  of  the  same  side.  Both  are 
uuited  tu  the  perforating  branch  already  noticed. 

Anterior  tibial  artery. — After  passing  down  along  the  leg  on  its  antero-external  face, 
as  in  Solipeds,  this  vessel  arrives  on  the  hock,  where  it  takes  the  name  of  pedal 
artery,  and  furnishes  the  perforating-pedal  artery ;  it  is  continued  by  the  metatarso  pedal 
or  collateral  artery  of  the  cannon. 

a.  The  perforating  pedal  artery  does  not  differ  from  that  of  the  Horse. 

b.  The  metatarso-pedal,  or  collateral  of  the  cannon,  descends,  flanked  by  two  satellite 
veins,  in  the  channel  on  the  anterior  face  of  the  metatarsal  bone,  giving  oft"  towards  the 
inferior  extremity  of  tiiat  channel  the  perforating  branch  already  spokea  of,  and  is 
continued  into  the  digital  region  as  the  common  digital  artery. 

The  perforating  branch  of  the  collateral  of  the  cannon  passes  into  the  foramen  pierced 
from  before  to  behind,  across  the  inferior  extremity  of  the  metatarsal  bone,  arriving 
beneath  the  suspensory  ligament,  and  then  divides  into  several  ascending  Mid  descending 
branches.  The  first  join  the  deep  and  superficial  postei  ior  metatarsal  arteries  furnished 
by  the  plantar  and  pedal  perforating  arteries.  Among  the  second,  we  notice  three  digital 
arteries,  facsimiles  in  miniature  of  those  which  will  be  described  in  the  anterior 
limb :  two  lateral,  descending  on  the  excentric  side  of  the  phalanges ;  a  median, 
turning  within  the  flexor  tendons  to  place  itself  behind  them  on  the  middle  line  of  the 
digital  region,  and  prolonged  into  the  interdigital  space,  where  it  anastomoses  with  a 
branch  of  the  principal  artery  of  the  digits. 

The  latter  artery,  the  common  digital,  descends  into  the  space  between  the  digits, 
after  passing  beneath  the  capsular  ligament  of  the  metatarso-phalangeal  articulations,  in 
the  notch  comprised  between  the  two  articular  surfaces  of  the  metatarsal  bone,  and 
terminates  above  the  inferior  extremity  of  fhe  first  phalanx  by  two  ungueal  arteries, 
whose  description  will  be  reserved  until  describing  the  arteries  of  the  anterior  limb, 
In  the  number  of  collateral  branches  emanating  from  this  vessel,  there  may  be  particularly 
remarked  a  large  off-shoot  which  arises  a  little  before  the  separation  of  the  two  ungueal 
arteries,  and  is  directed  from  before  to  behind,  dividing  at  the  posterior  part  of  the 
interdigital  space  into  several  divisions,  the  principal  of  which  are :  1,  Two  transverse 
branches  passing  between  the  flexor  tendons  and  the  phalanges,  to  be  joined  to  the 
lateral  digital  arteries ;  2,  A  single  ascending  branch,  joining  witli  the  posterior  median 
digital  artery ;  3,  A  descending  branch,  also  single,  dividing  into  two  portions  which 
reach  the  heels,  to  be  distributed  to  the  plantar  cushion  and  the  villous  tissue.  These 
branches  represent  the  arteries  of  the  plantar  cushion  in  the  Horse,  and  will  be  noticed 
more  in  detail  in  the  description  of  the  arteries  of  the  anterior  limb,  where  iu 
principle  they  are  found  to  be  exactly  like  these. 

2.  External  Iliac  Arteries  of  the  Pig. 

The  distribution  of  these  vessels  in  the  Pig  is  remarkably  like  that  we  have  described 
as  existing  in  Ruminants,  even  in  the  terminal  portions  of  the  limbs,  notwithstanding 
the  complete  development  of  the  two  lateral  digits.  It  may  be  noted,  however,  that  the 
posterior  tibial  artery  is  somewhat  slender,  and  that  it  is  singularly  reinforced  by  its 
anastomosis  with  the  saphena  artery,  whose  dimensions  are  relatively  considerable.' 

3.  External  Iliac  Arteries  of  Carnivora. 

The  crural  trunk  is  divided  in  the  Carnivora,  as  in  the  other  animals,  into  three 
sections:  the  proper  iliac  artery,  the  femoral  artery,  and  the  popliteal  artery,  terminated 
by  the  tibial  branches. 

Proper  iliac  artery. — ^Tliis  vessel  does  not  give  rise  to  any  branch,  as  the  cir- 
cumflexa  ilii  comes  directly  from  the  abdominat  aorta. 

*  In  small  Ruminants,  the  posterior  tibial  artery,  properly  speaking,  is  equally 
rudimentary ;  the  saphena  artery  constitutes  the  principal  vessel.  From  a  note  which 
we  made  a  long  time  ago,  it  appears  the  first  vessel  is  altogether  absent  sometimes,  and 
that  the  plantar  divisions  come  exclusively  from  the  saphena,  as  in  the  Carnivora. 


THE  EXTERNAL  ILIAC  ARTERIES.  557. 

Femoral  miery. — As  in  the  Horse,  this  gives  off:  1,  Several  muscular  innominate 
branches ;  2,  Two  great  muacular  arteries,  the  posterior  of  whicli  furnishes  the  prepubic 
artery  ;  3,  A  sapheual  brunch. 

In  the  Bitch,  the  external  piulic  artery,  emanating  from  the  prepubic  division,  presents 
some  peculiarities  in  it^s  distribution :  it  gives  oil'  a  long  branch  whicli  is  placed  in  the 
texture  of  the  maminse,  and  passes  forward  to  meet  and  unite  with  the  mammary  branch 
furaished  by  the  internal  thoracic  artery ;  it  then  runs  between  the  two  thighs  in  a 
Hexuous  manner,  and  reaches  the  lips  of  the  vulva,  where  it  ends  in  numerous  ramuscides 
that  anastonii'se  witti  the  vidvular  divisions  of  the  internal  pudic  artery. 

The  sapheua  artery  is  as  remarkable  for  its  large  volume  as  for  its  destination.  It 
descends  on  the  internal  face  of  the  leg,  furnishing  numerous  subcutaneous  divisions, 
and  tirminates  at  the  hock  by  several  slender  plantar  twigs,  which  accompany  the  flexor 
tendons.  Among  the  branches  given  otf  by  this  vessel  in  its  course,  it  is  necessary  to 
distinguish  two:  one  which  follows  the  anterior  branch  of  the  taphena  vein  to  the 
hock,  where  it  communicates  by  its  terminal  divisions  with  the  tarsal  artery ;  the  other 
arises  a  little  lower,  passes  beneath  the  phalangeal  Hexor  muscles,  and  is  expended  on  the 
hock  in  articular  and  malleolar  branches.  In  the  latter  branch  we  see  a  trace  of  the 
peroneal  artery  of  Man.  The  saphena  itself,  considered  as  a  whole,  and  particularly 
towards  its  interior  moiety,  supplements  the  posterior  tibial  artery. 

Popliteal  artery. — This  artery  gives  an  important  femoro-popliteal  branch,  and  enters 
the  tibio-peroneal  arcade  to  constitute  the  anterior  tibial  artery,  after  distributing  on 
its  course  muscular  ramuscules — rudiments  of  the  posterior  tibial  artery  of  other  animals. 

The  anterior  tibial  artery,  arriving  in  front  of  the  hock,  detaches  the  tarsal  artery  : 
a  voluminous  branch  divided  near  its  origin  into  several  superficial  superior  and  inferior 
branches.  It  continues  to  descend,  traverses  from  before  to  behind  tlie  superior  part  of 
the  third  intermetatarsal  space,  and  terminates  by  an  arterial  arcade  situated  beneath 
the  flexor  tendons ;  from  this  arcade  emanate  ascending  divisions,  which  anastomose 
with  the  plantar  arteries,  and  three  large  descending  or  digital  branches,  which  affect  the 
same  dispcjsition  as  three  analogous  principal  arteries  emanating  from  the  superficial 
palmar  arcade  of  the  anterior  limb. 

COMPARISON   OF   THE   EXTERNAL   ILIAC3   OP    MAN   WITH   THOSE    OF   ANDTALS. 

In  Man,  the  external  iliac  forms  the  external  branch  of  the  bifurcation  of  the 
common  iliac  ;  it  extends  to  the  crural  arch,  where  it  takes  the  name  of  femoral  artery. 
It  furnishes  the  circumflexa  ilii  and  epigastric  :  the  latter  resembling,  in  its  distribution, 
the  posterior  abdominal  branch  given  otf  by  the  prepubic  artery  in  the  Horse. 

The  femoral  artery  has  the  same  general  disposition  as  in  animals,  and  almost  the 
sam»^  collateral  branches.  There  is  no  prepubic  artery  ;  the  divisions  furnished  by  this 
trunk  in  Solipeds  originate  separately  from  the  femoral  artery ;  these  are :  the  abdominal 
tegumental  artery  (superficial  epigastric),  and  the  external  pudic  arteries — the  one  re- 
sembling the  subcutaneous  abdominal  artery,  and  the  others  the  branches  of  the  external 
pudic  artery  of  animals. 

The  popliteal  artery  is  a  superficial  vessel  fifuated  at  the  posterior  face  of  the  knee- 
joint,  in  a  lozenge-shaped  space  limited  by  the  muscles  of  the  region,  and  named  the  . 
popliteal  space.     At  the  tibio-peroneal  arch    it  bifurcates,  and  constitutes  the  anterior 
tibial  and  the  tibio-peroneal  trunks. 

The  tihio-peroneal  trunk  does  not  exist  in  animals  in  which  the  peroneal  artery 
is  in  a  rudimentary  state,  in  consequence  of  the  feeble  development  of  the  peroneus. 
This  trunk  is  short,  and  furnishes  the  nutrient  artery  of  the  tibia,  then  divides  into  the 
peroneal  and  posterior  tibial  arteries.  The  first  descends  to  the  external  malleolus, 
along  the  inner  face  of  the  tibia,  and  terminates  in  two  branches,  one  of  which,  the 
anterior  peroneal,  communicates  with  the  dorsal  artery  of  the  tarsus — a  branch  of  the 
pedal.  The  posterior  tibial,  on  reaching  the  concavity  of  the  calcis,  constitutes  the 
internal  and  external  plantar  arteries.  The  internal  pAantar  is  directed  forwards,  beneath 
the  sole  of  the  foot,  and  is  lost  in  the  muscles  of  the  great  toe,  or  forms  the  collateral  of 
the  latter  vessel.  Beneath  the  tarsal  articulations,  the  external  plantar  describes  a  curve, 
having  its  con.-avity  backwards,  and  anastomoses,  at  the  fourth  intermetatarsal  space, 
with  the  termination  of  the  dorsalis  pedis;  from  this  results  a  plantar  arch,  which  givts 
otf,  from  without  to  within:  1,  The  external  collateral  of  the  little  toe;  2,  3,  4,  5,  the 
interosseous  plantar  ('or  digital)  arteries  of  the  first,  second,  third  and  fourth  inter- 
metatarsal spaces ;  these  arteries,  at  the  root  of  the  toes,  bifurcate  to  furnish  collaterals 
to  these  organs. 

The  anterior  tibial  artery,  situated  on  the  anterinr  face  of  the  interosseous  ligament 
that  unites  the  tibia  to  the  peroneus,  extends  to  the  annular  ligament  of  the  tarsus, 


558 


THE  ARTERIES. 


where  it  is  continued  by  the  dorsalis  pedis,  which  descends  along  the  dorsum  of  the  foot 
to  gain  the  summit  of  the  fourth  interosseous  space. 

The  dorsal  artery  of  the  metatarsus  {metatarsea)  is  almost  nil  in  Solipeds.    In  Man  it 


Fisf.  279. 


Fia:.  280. 


i\\ 


m/ 


ANTERIOR  ASPECT  OF  HUMAN  LEG  AND  FOOT. 

1,  Tendon  of  insertion  of  the  quadriceps  ex- 
tensor muscle;  2,  Insertion  of  the  ligamen- 
tum  patella  ;  3,  Tibia  ;  4,  Extensor  longus 
digitorum ;  6,  Peronei ;  7,  Inner  belly  of 
gastrocnemius  and  soleus ;  8,  Annular 
ligament ;  9,  Anterior  tibial  artery  ;  10, 
Its  recurrent  branch  inosculating  with  (2) 
inferior  articular  and  (1)  superior  articular 
arteries,  branches  of  the  popliteal  ;  11, 
Internal  malleolar  artery;  17,  External 
ditto,  inosculating  with  anterior  peroneal 
artery,  12;  13,  Dorsalis  pedis  artery;  14, 
Tarsea  and  metatarsea ;  15,  Dorsaiis  hal- 
lucis  artery ;  16,  Continuation  of  dorsalis 
pedis  into  sole  of  foot. 


POSTERIOR   ASPECT   OF   HUMAN   LEG. 

1,  Tendons  of  inner  ham-string  ;  2,  Ditto  ot 
biceps ;  3,  Popliteus  muscle ;  4,  Flexor 
longus  digitorum  ;  5,  Tibialis  posticus  ; 
6,  Fibula  ;  7,  Peronei  muscles ;  8,  Lower 
portion  of  flexor  longus  pollicis,  with  its 
tendon  ;  9,  Popliteal  artery,  giving  off 
articular  and  muscular  branches  ;  10,  An- 
terior tibial  artery;  11,  Posterior  tibial 
artery;  12,  Relative  position  of  tendons 
and  artery;  13,  Peroneal  artery;  14,  Pos- 
terior peroneal. 


is  directed  transversely  to  the  tarsus,  from  within  to  without ;  its  terminal  branches 
unite  on  the  dorsum  of  the  tarsus,  and  the  arch  it  forms  gives  oft'  tiie  dorsal  interosseous 
arteries  of  the  three  first  spaces.     These  communicate  above  and  below  in  the  inter- 


THE  BRACHIAL  OR  AXILLARY  ARTERIES. 


559 


metatarsal  spaces,  with  tlie  plantar  intLTOsseous  arteries  by  the  anterior  and  j^osterior 
ptrforating  arteries;  finally,  at  the  base  of  the  tees  they  bii'urcate  to  form  the  collateral 
arteries  of  the  toes. 

The  dorsal  collateral  artery  of  the  fourth  space  represents 
the  vessel  described  in  the  Horse  by  the  name  of  metatarso-  Fig.  281. 

pedal  artery,  or  collateral  of  the  cannon  ;  it  forms  the  in- 
ternal collateral  dorsal  of  the  fourth  toe,  and  external  collateral 
of  the  great  toe. 

Tlje  dorsalis  pedis,  after  giving  oS"  the  last-named  vessel, 
dips  into  the  fourth  space  and  reaches  the  lower  surface  of 
the  foot,  whore  it  anastoniosL-s  with  the  internal  plantar  artery. 
In  this  hist  portion  of  its  course  it  resembles  the  vessel  we 
have  named  the  perforating  pedal  in  Solipeds. 

Article  V. — Anterior  Aorta.     (Fig.  282,  1.) 

This  vessel,  tlie  smallest  of  tlie  two  trirnks  suc- 
ceeding the  common  aoi-ta,  is  no  more  than  2  or  2^ 
inches  in  length  at  the  most.  It  leaves  the  pericar- 
dium to  pass  between  the  two  layers  of  the  medias- 
tinum in  an  oblique  direction  from  below  iipwards 
and  behind  forwards,  above  the  right  aui'icle,  below 
the  trachea,  and  to  the  left  of  the  anterior  vena  cava. 
After  furnishing  some  insignificant  twigs  to  the 
peric.irdium  and  mediastinum,  it  divides  into  two 
branches  w^hich  constitute  the  brachial  trunJcs  or 
axillary  arteries. 

In  the  Pachyderms  and  Carnivora,  the  anterior 
aorta  does  not  exist,  and  the  axillary  arteries  arise 
directly  from  the  aortic  trunk,  towards  the  point 
from  which  the  anterior  aorta  springs  in  other 
animals. 


ARTERIES   OF   SOLE   OP 
HUMAN    FOOT. 

Under  surface  of  os  cal- 
cis ;  2,  Musculus  acces- 
sorius;  3,  Long  flexor 
tendons ;  4,  Tendjin  of 
peroneus  longus ;  5,  Ter- 
mination of  posterior 
tibial  artery ;  6,  Internal 
plantar ;  7,  External 
plantar;  8,  Plantar  arch 
giving  oil'  four  digital 
branches,  three  of  which 
are  seen  dividing  into 
collaterals  for  adjoining 
toes. 


Article  YI. — Brachial  Trunks  or  Axillary 
Arteries.     (Fig.  282,  2,  3.) 

The  brachial  trunks,  terminal  branches  of  the 
anterior  aorta,  are  distinguished  into  left  and  right. 
The  latter  is  much  larger  than  the  former,  because 
it  furnishes  the  arteries  of  the  head.  It  is  also 
named  the  hrachio- cephalic  trunk  (or  arteria  innomi- 
nata). 

Origin. — They  separate  from  one  another  at  an 
acute  angle,  the  left  being  a  little  more  elevated 
than  the  right. 

Course  and  direction. — Both  branches  are  directed  forwards,  between  the 
laminte  of  the  anterior  mediastinum  and  beneath  the  trachea ;  gaining  the 
entrance  to  the  chest,  and  leaving  it  by  turning  round  the  anterior  border 
of  the  first  rib,  under  the  insertion  of  the  scalenus,  they  become  inflected 
backwards  and  downwards,  to  be  placed,  one  to  the  right,  the  other  to  the 
left,  at  the  internal  face  of  the  anterior  limb,  in  the  middle  of  the  nervous 
branches  of  the  brachial  plexus,  and  continue  within  the  arm,  assuming  the 
name  oi  humeral  artery  on  leaving  the  interstice  which  separates  the  sub- 
scapularis  muscle  from  the  adductor  of  the  arm. 

In  its  thoracic  course,  the  left  trunk  describes  a  curve  whose  convexity 
is  upwards,  the  right  taking  a  rectilinear  direction. 

Belations. — In  studying  the  relations  of  the  brachial  trunks,  we  recognise 
two  principal  portions :  one  thoracic,  placed  in  the  cliest ;  the  other  axillary, 


560  THE  ARTERIES. 

situated  beneath  the  limb.  In  tbeir  thoracic  portion,  the  orachial  trunks, 
at  first  lying  beside  each  other,  separate  slightly  in  front  to  reach  the  interna] 
face  of  each  of  the  two  first  ribs.  They  are  accompanied  by  the  cardiac, 
pneumogastric,  inferior  laryngeal,  and  diaphragmatic  nerves,  and  are  in- 
cluded, as  already  noticed,  between  the  two  layers  of  the  anterior  medias- 
tinum. The  right  occupies  nearly  the  median  line  beneath  the  inferior  face 
of  the  trachea,  to  the  left  and  above  the  anterior  vena  cava.  The  left 
slightly  rises  on  the  side  of  the  trachea,  and  generally  corresponds  inwardly 
to  the  thoracic  duct. 

In  their  axillary  portion,  these  vessels  accompany  the  corresponding 
venous  trunks,  cross  the  terminal  tendon  of  the  subscapularis  muscle  in 
passing  below  the  humeral  insertion  of  the  pectoralis  magnus,  and  among 
the  branches  of  the  brachial  plexus,  but  embraced  more  particularly  by 
the  median,  anterior  humeral,  and  ulnar  nerves. 

Distribution. — The  axillary  arteries  give  off,  on  their  course,  eight  col- 
lateral branches.  Four  arise  from  the  thoracic  portion :  three  ujiper,  the 
dorsal,  superior  cervical,  and  vertebral  arteries ;  and  an  inferior,  the  internal 
thoracic.  Two  are  detached  at  the  first  rib :  one  downwards,  the  other 
forwards ;  these  are  tSe  external  thoracic  and  superior  cervical  arteries.  Two 
originate  from  the  axillary  portion  of  the  trunk  and  pass  upwards  :  they  are 
the  super-  and  subscapular  arteries.  After  furnishing  the  latter  vessel,  the 
brachial  trunk  is  continued  by  the  humeral  artery. 

Independently  of  all  these  branches,  the  right  axillary  artery  gives  off, 
near  its  origin,  the  common  trunk  of  the  two  carotid  arteries,  which  will  be 
studied  in  a  separate  article. 

Preparation. — The  subject  being  placed  on  the  right  side,  remove  the  skin  and  the  left 
anterior  limb,  in  order  to  make  the  dissection  at  two  periods. 

Fird  period. — Dissect  all  the  intra-thoracic  portion  of  the  left  axillary  artery  and  its 
collateral  branches,  as  in  figure  282,  taking  care  to  leave  the  inferior  cervical  artery  (which 
has  been  cut  in  the  figure  to  render  the  drawing  more  distinct;  attached  by  its  superior 
extremity  to  the  middle  portion  of  the  mastoido-humeralis,  which  has  not  been  disturbed. 

Second  ^)er«orf.— Prepare,  on  the  separated  limb,  the  extra-thoracic  portion  of  the 
vessel  and.  all  the  arteries  it  furnishes,  in  taking  as  guides  figures  283,  290,  and  291. 

COLLATERAL  BRANCHES  OF  THE  AXILLARY  ARTERIES. 

1.  Dorsal,  Dorso-muscular  or  Transverse  Cervical  Artery.     (Fig.  282,  4.) 

Chiefly  destined  to  the  muscles  of  the  withers,  this  artery,  the  first  given 
off  by  the  brachial  trunk,  crosses  outwardly  the  trachea,  thoracic  duct, 
oesophagus,  great  sympathetic  nerve,  and  the  long  muscle  of  the  neck,  in 
proceeding  beneath  the  mediastinal  layer ;  it  reaches  and  passes  over  the 
second  intercostal  space,  bends  slightly  backwards,  and  places  itself  in  the 
interstice  which  separates  the  angular  muscle  of  the  scapula  and  great 
serratus  muscle  from  the  inferior  branch  of  the  ilio-spinal  muscle  (longis- 
simus  dorsi),  where  it  separates  into  several  divergent  branches.  The  majority 
of  these  ascend  towards  the  superior  border  of  the  withers,  neck,  and 
shoulders,  by  gliding  between  the  latter  muscles,  the  splenius,  and  the 
small  anterior  serratus  on  the  one  part,  and  the  great  serratus,  rhomboideus, 
and  proper  elevator  of  the  shoulder  on  the  other,  to  be  distributed  to  those 
muscles  and  the  integuments  covering  them.  The  most  anterior  of  these 
branches  passes  between  the  splenius  and  the  great  comjilexus  muscles, 
parallel  Avith  the  superior  cervical  artery,  which  is  in  front  of  it,  and  com- 
municates by  its  ramuscules  with  the  latter  vessel,  as  well  as  with  the 
vertebral  and  occipito-muscular  arteries.     The  last-named  branch  is  some- 


THE  BRACHIAL  OR  AXILLARY  ARTERIES.  561 

times  long  and  voluminous,  and  partly  supplements  the  superior  cervical, 
as  is  exemj^lified  in  the  specimen  which  served  for  Fig.  282. 

Before  leaving  the  thorax,  the  dorsal  artery  gives  off  some  unimportant 
ramuscules  and  the  subcostal  artery  (siijperior  intercostal  of  Man).  This 
branch  (Fig.  282,  5)  curves  backwards  and.  with  the  sympathetic  chain,  places 
itself  beneath  the  costo-vertebral  articulations,  against  the  long  muscle  of 
the  neck,  furnishing  the  second,  third  and  fourth  intercostal  arteries  and 
the  corresponding  spinal  branches,  and  terminating  at  the  fifth  intercostal 
space  by  either  forming  the  artery  which  descends  into  that  space,  in 
anastomosing  by  inosculation  with  a  branch  emanating  from  the  first 
posterior  intercostal  artery,  or  by  expending  itself  in  the  spinal  muscleso 
Frequently  the  second  intercostal  and  its  spinal  branch  come  directly  from 
the  dorsal  artery  ;  the  fifth  also  often  arises  from  the  posterior  aorta.^ 

On  the  right  side,  the  dorsal  artery  always  proceeds  from  a  trunk  common 
to  it  and  the  superior  cervical  artery :  a  circumstance  sometimes  observed  in 
the  left.     This  trunk  has  no  relation  with  the  oesophagus, 

2.  Superior  Cervical,  Cervico-muscular,  or  Deep  Cervical  Artery. 
(Fig.  282,  6.) 

This  vessel  arises  in  front  of  the  preceding  artery,  affects  the  same 
relations  in  the  thoracic  cavity,  which  it  leaves  by  passing  between 
the  two  first  ribs,  behind  the  last  costo-transverse  articulation;-  it  is 
then  directed  upwards  and  forwards,  passing  beneath  the  inferior  branch  of 
the  ilio-spinal  and  great  complexus  muscles,  courses  in  a  flexuous  manner 
through  the  space  comprised  between  the  latter  muscle  on  one  side,  and 
the  superior  branch  of  the  ilio-spinalis  and  cervical  ligament  on  the 
other,  and  arrives  at  the  second  vertebra  of  the  neck,  where  its  terminal 
divisions  anastomose  with  the  branches  of  the  occipito-muscular,  vertebral, 
and  even  the  dorsal,  arteries. 

The  superior  cervical  artery  distributes  in  its  course  :  1,  The  first  inter- 
costal artery  and  the  first  spinal  branch  ;  2,  Very  numerous  branches  which 
are  expended  in  the  muscles  and  integuments  of  the  cervical  region,  as  well 
as  in  the  large  ligament  occupying  the  middle  plane  of  that  region  ;  among 
these  branches,  one  longer  than  the  others  traverses  the  great  complexus 
muscle  to  place  itseK  between  it  and  the  splenius,  and  which  is  sometimes 
supplemented  in  great  part  by  the  dorsal  artery. 

3.  Vertebral  Artery.     (Fig.  282,  7.) 

Arising  at  an  acute  angle  from  the  axillary  artery  at  the  first  intercostal 
space,  and  covered  at  its  origin  by  the  mediastinal  layer,  the  vertebral 
artery  proceeds  forward  and  upward,  within  the  first  rib,  outside  the 
oesophagus,^  the  trachea,  and  the  inferior  cervical  ganglion,  and  is  situated 
at  the  bottom  of  the  interstice  separating  the  two  portions  of  the  scalenus, 
with  the  fasciculus  of  branches  originating  from  the  brachial  plexus,  which 
is  a  little  above  the  vessel.  It  then  passes  beneath  the  transverse  process 
of  the  seventh  cervical  vertebra,  and  traverses  the  series  of  cervical 
foramina,  hidden  beneath   the  intertransverse   muscles,   to  anastomose  in 

1  For  the  description  of  these  arteries,  see  page  524. 

-  We  have  seen  it  escape,  along  with  the  dorsal  artery,  by  tlie  second  intercostal 
space. 

^  On  the  right,  these  relations  with  the  oesophagus  are  not  present. 


THE  ARTERIES, 
Fig.  282. 


DISTRIBUTION  OF   THE   ANTERIOR   AORTA. 

T,  Anterior  aortca;  2,  Left  axillary  artery;  3,  Right  axillary  artery;  4,  Dorsal 
artery ;  5,  Subcostal  artery ;  6,  Superior  cervical  artery ;  7,  Vertebral  artery ; 
8,  8',  Inferior  cervical  artery;  9,  Origin  of  the  internal  thoracic  artery;  10, 
Origin  of  one  of  the  external  or  intercostal  branches  of  this  artery;  11,  One  of 
its  inferior  ramuscules;  12,  External  thoracic  artery  ;  13,  Origin  of  the  super- 
scapular  artery  ;  14,  Primitive,  or  common  carotid  artery  ;  14',  Accessory  thyroid 
artery;  14"  Thyro-laryngeal  artery  ;  15,  Atloido-muscular  artery  ;  16,  Occipito- 
muscular  artery;  17,  Posterior  aorta. — A,  Pulmonary  aorta;  B,  Trachea;  c,  Q^^so- 
phagus ;  D,  Cervical  ligament ;  E,  Superior  bi'anch  of  the  ilio-spinal  muscle ;  F, 
Inferior  branch  of  the  same ;  G,  Great  complexus  muscle ;  H,  Splenius  muscle  ; 
I,  I,  Originating  aponeurosis  of  the  splenius  and  the  small  anterior  serratus 
muscles  ;  K,  Section  of  the  great  oblique  muscle  of  the  head  ;  L,  Great  posterior 
rectus  muscle  of  the  head;  M,  Great  anterior  ditto;  N,  Sterno-maxillaris  muscle; 
O,  P,  Gre.at  pectoral  and  sterno-prescapularis  muscles  turned  downwards. 


THE  BRACHIAL  OB  AXILLAEY  ARTERIES.       .  563 

full  canal  witli  the  retrogvatlo  brancli  of  the  occipital  artery,  at  the  atlo-axoid 
articulation,  underneath  the  great  oblique  muscle  of  the  head. 

In  its  track,  it  detaches  at  each  intervertebral  space  numerous  branches, 
which  may  be  divided  into  inferior,  superior,  external,  and  internal.  The 
first  chiefly  pass  to  the  scalenus,  longus  colli,  and  the  great  anterior  rectus 
muscle  of  the  head.  The  second,  winch  are  incomparably  larger  and  more 
numerous  than  all  the  others,  are  destined  to  the  two  complex  muscles,  the 
transverse-spinous  (semispinalis)  muscles  of  the  neck,  and  to  the  ilio-spinal 
muscle ;  they  anastomose  with  the  divisions  of  the  superior  cervical  and 
occipito-muscular  arteries.  The  external  branches,  are  very  small,  and 
pass  to  the  intertransverse  muscles.  The  internal  branches  enter  the  inter- 
vertebral foramina  to  join  the  middle  spinal  artery. 

4.  Internal  Thoracic,  or  Internal  Mammary  Artery.     (Fig.  282,  9.) 

The  internal  thoracic  artery  emerges  from  tbe  brachial  trunk  at  the 
first  rib,  and  immediately  descends  along  the  inner  face  of  that  bone  to  the 
sternum,  remaining  covered  by  the  pleura.  It  then  bends  backwards,  passes 
under  the  triangular  muscle  and  above  the  sternal  cartilages,  which  it 
crosses  near  the  chondro-sternal  articulation,  and  reaches  the  base  of  the 
xiphoid  appendix,  where  it  ends  in  two  branches  :  one  abdominal,  the  other 
thoracic,  and  which  have  been  named  the  anterior  abdominal  and  asternal 
arteries. 

In  its  course,  the  internal  thoracic  artery  sends  off  collateral  branches 
which  may  be  distinguished  into  superior,  inferior,  and  external.  The 
superior  are  always  very  slender,  and  proceed  to  the  j)ericardium  and 
mediastinum.  The  inferior  (Fig.  282,  11)  are  very  large,  and  traverse  the 
intercostal  spaces  to  enter  the  pectoral  muscles,  where  they  meet  the  ramifi- 
cations of  the  external  thoracic  artery.  The  external  branches  (Fig.  282,  10) 
follow  the  intercostal  spaces ;  each  generally  divides  into  two  branches, 
which  finally  anastomose  by  inosculation  with  the  terminal  divisions  of  the 
first  seven  intercostal  arteries. 

Terminal  branches  of  the  internal  thoracic  artery. — 1.  Anterior  ab- 
dominal artery. — This  vessel  separates  from  the  asternal  artery  at  an  acute 
angle,  and  passes  directly  backward  to  escape  from  the  chest  by  coursing 
beneath  the  xiphoid  appendix ;  it  then  places  itself  on  the  superior  face  of 
the  rectus  muscle  of  the  abdomen,  which  it  enters,  after  detaching  lateral 
branches  to  the  abdominal  walls,  and  anastomoses  by  its  terminal  ramifica- 
tions with  the  posterior  abdominal  artery. 

2.  Asternal  artery. — This  vessel  glides  within  the  cartilaginous  circle 
formed  by  the  false  ribs,  in  crossing  the  digitations  of  the  transverse  muscle 
of  the  abdomen,  and  terminates  at  the  thirteenth  intercostal  space,  in  which 
it  ascends  to  anastomose  with  the  corresponding  intercostal  artery.  It 
supplies  in  its  track :  intercostal  branches,  which  comport  themselves  like 
the  analogous  branches  of  the  internal  thoracic  artery  ;  fine  diaphragmatic 
twigs ;  and  abdominal  divisions,  which  particularly  ramify  in  the  tran verse 
muscle. 

5.  External  or  Inferior  Thoracic,  or  External  Mammary  Artery. 
(Fig.  282,  12.) 

Principally  destined  to  the  deep  pectoral  muscles,  this  artery  commences 
at  an  acute  angle  in  front  of,  but  close  to,  the  preceding,  turns  the  anterior 
border  of  the  first  rib,  and  then  passes  back  against  the  internal  face  of  the 
great  pectoral  and  steruo-prescapular  muscles,  in  which  are  expended  its 


564  TEE  ARTERIES. 

collateral  and  terminal  divisions.     It  gives  oflf  a  fine  branch  whicLi  accom- 
panies the  spur  vein,  and  ramifies  in  the  panniculus  carnosus. 

This  artery  sometimes  rises  from  the  suprasternal  vessel ;  its  volume 
is  subject  to  great  variations,  and  we  have  seen  it  entirely  absent. 

6.  Inferior  Cervical,  or  TracJielo-muscular  Artery.     (Fig.  282,  8,  8'.) 

Originating  opposite  the  two  preceding  vessels,  sometimes  near  the 
external,  and  at  other  times  near  the  internal  mammary  arteries,  this  vessel 
is  at  first  situated  in  the  gulf  between  the  jugulars,  within  the  sterno-pre- 
scapular  muscle,  and  above  the  glands  at  the  entrance  to  the  chest ;  it  divides 
after  a  short  course  into  two  branches,  which  separate  at  a  very  acute  angle. 
One  of  these,  the  superior  (^ascending  cervical  of  Man),  rises  between  the 
mastoido-humeralis  and  subscapulo-hyoideus  muscles,  to  which  it  is  dis- 
tributed, as  well  as  to  the  glands  at  the  point  of  the  shoulder,  and  the  sterno- 
prescapularis  and  triangularis  scapulae  muscles. 

The  inferior  hranch  (tlioracica  acromialis  of  Man)  descends  in  the  in- 
terstice comprised  between  the  mastoido-humeralis  and  the  sterno-humeralis 
(pectoralis  parvus)  muscles,  accompanying  the  cephalic  vein;  it  is  distri- 
buted to  these  two  muscles,  the  sterno-aponeuroticus  (j)ectoralis  tiansversus), 
and  the  storno-prescapularis. 

7.  Super  scapular,  or  Superior  Scapular  Artery.     (Fig.  282.  13.) 

A  small  and  slightly  tortuous  vessel,  which  arises  from  the  axillary 
artery,  a  little  before  it  reaches  the  tendon  of  the  subscapularis  muscle. 
It  is  directed  upwards,  and  enters  the  space  included  between  that  muscle 
and  the  super-  (antea-)  spinatus,  after  sending  off  some  divisions  to  the  sterno- 
prescapularis  muscle.  Its  terminal  branches  are  expanded  in  the  inferior 
extremity  of  the  super-  and  subspinati  muscles,  the  tendon  of  the  coraco- 
radialis,  and  in  the  articulation  of  the  shoulder. 

8.  Inferior,  or  Subscapular  Artery.     (Fig.  347.) 

This  artery  is  remarkable  for  its  considerable  volume;  it  arises  at  a 
right  angle  from  the  axillary  artery,  at  the  space  separating  the  subscapularis 
from  the  adductor  of  the  arm.  Its  origin  indicates  the  limit  artificially 
fixed  between  the  brachial  trunk  and  the  humeral  artery.  It  is  seen  to 
proceed  upwards  and  backwards  in  this  interstice,  within  the  large  extensor 
of  the  fore-arm,  until  near  the  dorsal  angle  of  the  scapula,  where  it 
terminates. 

It  gives  oflf  on  its  track  : 

1.  An  artery  which,  following  the  inferior  border  of  the  great  dorsal 
muscle,  ascends  to  its  inner  face,  throwing  oflf  twigs  into  the  substance  of 
the  muscle  as  well  as  into  the  panniculus  carnosus. 

2.  The  scapula-humeral,  ov  posterior  circumflex  artery  of  the  shoulder,  which 
passes  from  within  that  articulation,  beneath  the  great  extensor  muscle  of 
the  shoulder,  to  reach  its  external  face  ;  after  giving  off  some  collateral 
branches,  it  arrives,  with  the  circumflex  nerves,  underneath  the  abductors  of 
the  arm,  where  it  breaks  up,  like  its  satellite  nerve,  into  several  divergent 
branches  destined  to  the  three  muscles  above  named,  the  oblique  flexor  and 
short  extensor  of  the  fore-arm,  and  to  the  mastoido-humeralis  and  panniculus 
carnosus. 


TEE  BRACHIAL  Oil  AXILLARY  ARTERIES.  565 

3.  Muscular  branches,  which  escape  at  intervals  during  the  course  of  the 
vessel,  and  are  sent  forwards  and  backwards.  The  anterior  pass  either  to  the 
internal  or  external  side  of  the  scapula,  or  to  both  sides  of  that  bone,  whose 
posterior  border  they  embrace  in  their  bifurcation.  The  internal  divisions 
creep  in  the  fissures  on  the  deep  face  of  the  bone,  throwing  their  ramuscules 
into  the  subscapularis  muscle,  and  even  reaching  the  super-  (antea-J  spinatus, 
as  well  as  the  insertion  of  the  angularis  and  gi'eat  seri-atus  muscles.  The 
external  divisions  traverse  the  large  extensor  of  the  fore-arm,  to  be  dis- 
tributed to  the  super-  and  subspinati  and  the  abductor  muscles  of  the  arm, 
one  furnishing  the  nutrient  artery  of  the  scapula.  The  posterior  branches 
supply  the  abductor  of  the  arm,  and  the  large  extensor  of  the  fore-arm. 


HUMEEAL  ARTERY,  OR  TERMINAL  ARTERY  OF  THE  BRACHIAL  TRUKK. 

(Fig.  347,  A.) 

Course. — This,  a  continuation  of  the  axillary  artery,  which  changes  its 
name  after  giving  off  the  subscapular  branch,  at  first  describes  a  slight 
curve  forwards  to  descend  almost  vertically  within  the  thoracic  limb  by 
crossing  obliquely  the  direction  of  the  humerus,  and  terminates  above  the 
inferior  extremity  of  that  bone  by  two  branches  which  constitute  the  anterior 
and  posterior  radial  arteries. 

Belations. — In  its  course,  the  humeral  artery  corresponds :  in  front,  to 
the  median  or  ulno-plantar  nerve,  and  to  the  posterior  border  of  the  coraco- 
humeralis  muscle,  which  it  closely  follows ;  behind,  to  the  vein  of  the  arm, 
and  through  it  to  the  ulnar  nerve  ;  outwardly,  to  the  common  tendon  of  the 
great  dorsal  muscle  and  the  adductor  muscle  of  the  arm,  to  the  middle 
extensor  of  the  fore-arm,  and  to  the  humerus ;  inwardly,  to  the  sheath  of  the 
coraco-radialis  muscle,  which  separates  the  pectoralis  magnus  from  the 
artery  of  the  arm,  and  in  which  this  vessel  is  inclosed,  in  common  with  its 
satellite  vein,  the  lymphatic  glands  and  vessels  of  the  arm,  as  well  as  with 
the  nerves  of  the  fore-limb. 

Collateral  branches. — Among  these  may  be  distinguished  four,  which 
merit  particular  mention.  They  are  the  prehmneral,  external  and  internal 
collateral  arteries  of  the  elbow,  and  the  principal  artery  of  the  coraco-radialis 
muscle.  We  need  only  indicate,  besides  these,  several  ii'regular  ramuscules 
which  go  to  the  latter  muscle,  to  the  coraco-humeralis,  and  to  the  middle 
extensor  of  the  fore-arm. 

1.  Prehumeral,  or  anterior  circumflex  artery  of  the  shoulder. — This 
arises  at  a  right  angle,  is  directed  forward,  passes  between  the  two  branches 
of  the  coraco-humeralis,  turns  round  the  anterior  face  of  the  humerus, 
beneath  the  bicij^ital  groove,  and  terminates  in  the  mastoido-humeralis 
muscle.  During  its  progess  it  gives  off  branches  to  the  scapulo-brachial 
and  biceps  muscles,  as  well  as  to  the  articulation  of  the  shoulder.  Among 
the  articular  ramifications,  there  is  one  which  ascends  outwai'dly  on  the 
tendon  of  the  subspinatus,  and  whose  ultimate  divisions  anastomose  with  the 
ramuscules  of  the  posterior  circumflex  artery. 

2.  Deep  humeral,  or  external  collateral  artery  of  the  elboio. — A  very  large 
branch  which  emerges  from  the  humeral  trunk,  by  forming  with  that  artery 
an  almost  right  angle  at  the  common  terminal  tendon  of  the  great  dorsal 
muscle  and  the  adductor  of  the  arm.  After  a  very  short  course,  it  divides 
into  two  principal  branches;  one  of  these  sends  its  ramuscules  into  the 
body  of  the  large  extensor  muscle ;  the  other  passes  under  that  muscle  in 

39 


566  THE  ARTERIES. 

turning  round  the  oblique  flexor  of  the  fore-arm,  along  witli  the  radial 
nerve,  and  reaching  beneath  the  short  extensor,  to  descend,  still  with  its 
satellite  nerve,  in  front  of  the  articulation  of  the  elbow,  where  this  branch 
anastomoses  with  the  anterior  radial  artery ;  it  supplies  all  the  olecranian 
muscles,  except  the  long  extensor,  as  well  as  the  oblique  flexor  of  the  fore- 
arm and  the  anterior  extensor  of  the  metacarpus. 

3.  Emcondyloid,  internal  collateral  of  the  elboio,  or  ulnar  artery. — 
Smaller  than  the  external  collateral,  this  artery  arises  at  the  nutiieut 
foramen  of  the  humerus,  and  proceeds  backwax'ds  on  the  internal  face  of 
that  bone,  to  pass  beneath  the  long  extensor  of  the  fore-arm,  by  following  in 
a  more  or  less  flexous  manner  the  inferior  border  of  the  middle  extensor; 
it  then  descends,  at  first  behind  the  epicondyle,  then  on  the  fore-arm,  which 
it  i)asses  along  for  its  whole  length,  underneath  the  aponeurotic  sheath  of 
this  region,  between  the  oblique  and  the  external  flexor  of  the  metacarpus, 
accompanied  by  the  ulnar  vein  and  nerve  of  the  same  name,  and  the  tendon 
of  the  ulnar  portion  of  the  perforans  muscle.  Arriving  near  the  carpus, 
this  long  branch  anastomoses  by  inosculation  with  a  branch  from  the 
posterior  radial  artery. 

In  its  antibrachial  course,  this  artery  only  gives  off  very  attenuated 
branches,  whose  study  is  of  little  importance.  But  before  attaining  the 
fore-arm,  it  furnishes  :  1,  The  nutrient  artery  of  the  humerus ;  2,  Articular 
ramuscules ;  3,  More  or  less  voluminous  muscular  branches,  particularly 
for  the  long  extensor  of  the  fore-arm,  the  middle  extensor,  and  the  sterno- 
aponeuroticus  :  those  which  arrive  in  the  latter  muscle  traverse  it  only  to 
become  subcutaneous  alternately  ;  one  of  them  accompanies  the  principal 
superficial  vein  of  the  fore-arm,  and  sends  ramuscules  into  the  bend  of  the 
elbow.  Eegular  in  their  distribution,  these  diff'erent  arteries  present 
numerous  varieties  of  origin,  amouij  which  it  is  difficult  to  distinguish  the 
most  constant  disposition.  The  last-mentioned  vessel  and  the  nutrient 
artery  of  the  humerus,  often  emanate  directly  from  the  humeral  trunk. 

4:.  Principal  artery  of  the  biceps,  or  coraco-radialis  artery. — This 
originates  a  little  below  or  above  the  preceding :  opposite  to,  or  in  front  of 
it.  it  usually  divides  into  two  branches :  one  ascending,  the  other  descending, 
which  enter  the  substance  of  the  muscle. 


1.  Anterior  Badial  Artery.     (Fig.  348,  A.) 

The  anterior  radial  artery,^  the  smallest  of  the  two  terminal  branches  of 
the  humeial,  separates  itself  at  an  acute  angle  from  the  posterior  artery, 
above  the  articular  condyle  of  the  humerus.  It  descends  on  the  anterior 
face  of  the  ulnar  articulation,  passing  beneath  the  inferior  extremity  of  the 
flexor  muscles  of  the  fore-arm  and  the  superior  extremity  of  the  principal 
extensor  of  the  metacarpus,  where  it  meets  the  radial  nerve ;  in  company 
with  this  nerve  it  extends  on  the  anterior  face  of  the  radius,  below  the 
anterior  extensor  muscle  of  the  phalanges,  to  the  knee,  where  it  becomes 
very  thin  and  breaks  up  into  several  ramuscules,  which  are  continued  on 
the  capsular  ligament  of  the  carpal  articulations,  after  anastomosing  on 
the  inner  side  with  the  divisions  of  a  branch  furnished  by  the  posterior 
radial  artery,  and  on  the  outside  with  the  ramifications  from  the  interosseous 
artery  of  the  fore-arm. 

'  In  Man  this  artery  is  absent,  or  rather  it  is  represented  by  an  insignificant 
muscular  twisr. 


THE  BRACHIAL  OR  AXILLARY  ARTERIES.  567 

These  terminal  ramuscules  of  the  anterior  radial  artery  are  distributed 
to  the  carpal  articulation,  or  the  sheaths  of  the  extensor  tendons,  and  com- 
municate with  the  dorsal  interosseous  metacarj^al  arteries. 

The  collateral  branches  given  otf  by  this  artery  are  very  numerous,  the 
majority  of  them  being  detached  from  the  superior  portion  of  the  vessel 
near  the  elbow ;  they  are  intended  to  supply  that  articulation,  but  more 
especially  the  muscular  masses  lying  in  its  neighbourhood,  or  covering  it. 

Such  is  the  usual  disposition  of  the  anterior  radial  artery ;  though  it  is 
liable  to  numerous  variations :  principally  in  the  manner  in  which  it  comports 
itself  with  the  interosseous  artery  of  the  fore-arm,  which  may  even  supple- 
ment it  for  the  whole  of  the  middle  and  lower  part  of  its  coui'se.  This  will 
be  noted  in  describing  the  next  artery. 


2.  Posteriw  Badial  Artery.     (Figs.  283,  1 ;  347,  b.) 

This  vessel,  in  its  volume  and  direction,  represents  the  continuation  of 
the  humeral  artery.  It  descends,  along  with  the  ulno-plantar  nerve,  on  the 
internal  ligament  of  the  humeroradial  articulation,  behind  the  terminal 
extremity  of  the  coraco-radialis ;  then  imder  the  internal  flexor  of  the  meta- 
carpus, its  satellite  muscle.  Arriving  at  the  inferior  extremity  of  the  radius, 
it  divides  into  two  terminal  branches;  which  are,  the  common  trunk  of  the 
interosseous  metacarpal  arteries  and  the  collateral  artery  of  the  cannon. 

Tiie  following   are   the   principal    collateral  branches  furnished  by  the 
posterior  radial  artery  : 

1.  At  the  superior  extremity  of  the  radius,  articular  ramuscules  which 
anastomose  with  analogous  branches  from  the  epicondyloid  artery. 

2.  A  little  lower,  large  divisions  destined  for  the  muscles  of  the  posterior 
antibrachial  region,  some  of  them  arising  from  the  next  artery. 

3.  The  interosseous  artery  of  the  fore-arm,  a  considerable  vessel  which 
originates  at  the  same  point  as  the  preceding — the  radio-ulnar  arch,  and 
which  crosses  this  from  within  to  without,  after  traversing  the  posterior  face 
of  the  radius,  beneath  the  perforaus  muscle,  to  descend  along  the  lateral 
extensor  muscle  of  the  phalanges,  in  the  channel  formed  outwardly  by  the 
imion  of  the  two  bones  of  the  fore-arm.  This  interosseous  artery  furnishes, 
immediately  after  its  exit  from  the  radio-ulnar  arch,  several  branches  to  the 
articulation  of  the  elbow  and  the  antibrachial  muscles.  At  its  terminal 
extremity  it  usually  divides  into  a  number  of  branches,  the  majority  of 
which  join  the  branches  sent  to  the  carpus  by  the  anterior  radial  artery.  It 
is  rare  that  it  does  show  some  fine  anastomoses  with  one  of  the  divisions  of 
the  latter  artery  in  front  of,  or  outside  the  articulation  of  the  elbow  ;  some- 
times it  directly  joins  that  vessel ;  and  I  have  seen  it,  on  the  contrary,  receive 
the  anterior  radial  artery,  which  it  in  part  supplanted, 

4.  Several  muscular  and  musculo-cutaneous  ramuscules  without  any  fixed 
arrangement,  arising  from  different  points  of  the  com'se  of  the  parent  artery, 
below  the  preceding  divisions. 

5.  A  deep  branch,  also  liable  to  very  numerous  variations,  having  its 
origin  at  the  radial  insertion  of  the  perforatus  muscle,  descending  on  the 
posterior  face  of  the  radius,  chiefly  destined  to  the  carpus,  and  remarkable 
for  the  anastomoses  that  its  internal  divisions  contract  with  the  anterior 
radial  artery,  and  for  those  which  occasionally  unite  its  external  ramifications 
to  the  ultimate  branches  of  the  interosseous  artery  of  the  fore-arm  or  the 
epicondyloid  artery  (Fig.  283,  2). 


568 


THE  ABTEBIES. 


Fig.  283. 


^' 


i-4 


i2Z- 


1.  First  Terminal  branch  of  the  Posterior  Hadial  Artery, 
or  Common  Trunk  of  the  Interosseous  Metacarpal 
Arteries.'     (Fig.  283,  5.) 

This  arterial  branch  separates  at  a  very  acute  angle 
from  the  collateral  artery  of  the  cannon.  It  descends 
inside  and  behind  the  carpus,  accompanied  by  the  prin- 
cipal subcutaneous  vein  of  the  limb,  and  with  it  is 
included  underneath  a  superficial  fascia,  which  maintains 
them  in  a  channel  hollowed  on  the  external  face  of  the 
carpal  fibrous  sheath.  It  thus  arrives  within  the  head  of 
the  inner  metacarpal  bone,  where  it  is  inflected  to  the 
outer  side  by  crossing  the  superior  extremity  of  the  sus- 
pensory ligament,  and  between  it  and  the  metacarpal  liga- 
ment the  latter  furnishes  to  the  perforans  tendon  ;  it  anas- 
tomoses by  inosculation  with  a  descending  branch  which 
emanates  from  the  superficial  arch  that,  above  the  car^jus, 
unites  the  epicondyloid  or  ulnar  artery  to  the  origin 
of  the  collateral  artery  of  the  cannon  (Fig.  283,  6).  The 
loop-like  anastomosis  thus  formed  by  the  radio-palmar 
artery,  exactly  corresponds  to  the  deep  palmar  arch  of 
pentadactylous  animals,  particularly  to  that  of  Man.  We 
propose  to  name  it  also  the  suhcarpal  arch,  by  reason  of 
the  position  it  occupies  in  regard  to  the  carpus,  reser- 
ving the  appellation  of  supracarpal  arch  for  the  super- 
ficial palmar  arch,  which  is  represented  by  the  anastomosis 
established  between  the  collateral  artery  of  the  cannon 
and  the  epicondyloid  artery. 

Four  principal  branches  emanate  from  this  subcarpal 
arch  :  these  are  the  metacarpal  interosseous  arteries,  dis- 
tinguished into  posterior  or  palmar,  and  anterior  or  dorsal. 

a.  The  posterior  interosseous  arise,  one  on  the  right, 
the  other  on  the  left,  at  the  head  of  the  lateral  meta- 
carpal bones,  each  descending  on  its  own  side,  and  in  a 
flexuous  manner,  along  these  rudimentary  bones,  in  the 
angular  groove  formed  by  their  inner  face  and  the  pos- 
terior face  of  the  principal  metacarpal  bone,  terminating 


i^jK) '  The  muscles  and  tendons  have  been  removed,  only  a  small  portion  of 
the  perforans  tendon  being  left ;  the  os  pedis  has  been  chiselled 
away  on  its  plantar  face  to  expose  the  semilunar  anastomosis. 
1,  Posterior  radial  artery ;  2,  Innominate  carpal  branch ;  3,  Supra- 
carpal  arch ;  4,  Epicondyloid  (ulnar)  artery ;  5,  Radio-palmar 
arterv,  or  common  trunk  of  the  interosseous  metacarpal  arteries ; 
6,  Subcarpal  arch ;  7,  7,  Posterior  interosseous  metacarpal  arteries  ; 
7',  7',  Anterior  interosseous  metacarpal  arteries;  8,  8,  Their  origm; 
9,  Collateral  artery  of  the  cannon ;  10,  Its  communicating  branch 
with  the  interosseous  arteries ;  11,  11,  Digital  arteries,  12,  Semi- 
lunar anastomosis  in  the  os  pedis ,  13,  Emergent  branches  of  this 
anastomosis ;  14,  Plantar  ungueal  artery,  forming  this  anastomotic 
arch  •  15  Orio-in  of  the  preplantar  ungueal  artery ;  16,  Origin  of  the  plantar-cushion 
artery;  17,  Origin  of  the  anterior  branch  of  the  coronary  circle;  18,  Posterior  branch  of 
the  same. 

»  This  vessel  corresponds  to  the  radio-palmar  artery  of  Man,  by  which  name  it  is 
sometimes  designated.    Rigot  has  improperly  named  it  the  deep  plantar  artery. 


ARTERIES      OP 
FORE-FOOT,       S: 
FROM   BEHIND. 


THE  BRACHIAL  OB  AXILLARY  ARTERIES.  569 

at  the  inferior  extremity  of  the  lateral  bones  bv  anastomosing  in  full 
canal  ^nth  a  branch  of  the  collateral  of  the  cannon.  They  furnish  some 
ramifications  to  the  suspensory  ligament  which  cuvers  them,  and  several 
tendinous  and  cellulo-cutaneous  twigs ;  one  supplies  the  medullaiy  artery 
of  the  principal  cannon  bone  (Fig.  283,  7). 

b.  The  anterior  interosseous  arteries  arise  from  nearly  the  same  point  as 
the  preceding,  one  outwards,  the  other  inwards,  turning  back  round  the  head 
of  the  lateral  metacarpals  to  place  themselves  in  the  groove  which  separates 
these  from  the  principal  metacarpal  bone,  on  their  external  or  dorsal  face, 
after  having  thrown  off  several  anastomosing  ramuscules  v/hich  communicate 
between  the  two  arteries  in  front  of  the  upper  extremity  of  the  median  meta- 
carpal bone,  or  with  the  terminal  branches  of  the  anterior  radial  and  the 
interosseous  arteries  of  the  fore-arm.  By  their  terminal  extremity,  these  two 
arteries  anastomose  with  a  branch  of  the  collateral  of  the  cannon — that 
which  receives  the  posterior  interosseous  arteries  ( Fig.  282,  7',  8). 

The  dorsal  interosseous  arteries,  although  much  finer  than  the  palmar  (in 
Solipeds  these  arteries  are  quite  rudimentary),  nevertheless  furnish  collateral 
divisions  destined  for  the  anterior  tendons  of  the  metacarpus,  the  periosteum, 
the  connective  tissue,  and  the  skin.  They  often  communicate  with  the 
posterior  arteries  by  deep  branches,  which  cross  the  intermetacarpal 
ligaments. 

Variations. — The  existence  of  the  interosseous  metacarpal  arteries,  their 
position,  and  their  anastomoses  with  the  inferior  extremity  of  the  collateral 
of  the  cannon,  are  constant ;  though  this  is  not  the  case  with  regard  to  their 
origin,  or  the  source  from  which  they  arise.  In  the  typical  description  we 
have  given,  we  have  considered  them  all  as  being  furnished  by  the  radio- 
palmar  artery ;  but  it  is  necessary  to  add  that  one  of  the  four,  the  external 
dorsal,  often  comes  directly  from  the  arterial  branch  that,  from  the  supra- 
carpal  arch,  descends  along  the  carpus  to  concur  in  forming  the  suhcarpal 
arch,  by  anastomosing  with  the  radio-palmar,  or  rather  with  a  branch  of  the 
interosseous  of  the  fore-arm.  It  is  also  necessary  to  add  that  these  meta- 
carpal arteries  sometimes  arise  together  from  one  large  branch  furnished  by 
the  collateral  of  the  cannon,  at  the  superior  extremity  of  the  metacai-pus, 
and  w  hich  receives  the  now  rudimentary  radio-palmar  artery,  as  well  as  that 
given  off  by  the  supracarpal  arch  ;  so  that  we  may  have  two  superposed 
supracarpal  arches.  We  have  met  other  anomalies  which  need  not  be  noticed 
here,  as  they  are  without  interest. 

2.  Second  Terminal  Branch  of  the  Posterior  Radial,  or  Collateral  Artery  of  the 
Cannon.^     (Fig.  283,  9.) 

The  collateral  artery  of  the  cannon  continues,  in  its  volimie  and  direction, 
the  posterior  radial  artery.  It  passes,  with  the  flexor  tendons,  under  the 
carpal  arch,  and  descends  on  the  inner  side  of  these  tendons,  accompanied 
by  the  internal  plantar  nerve,  to  above  the  fetlock  and  near  the  great 
sesamoid  bones,  where  it  bifiu-cates  into  the  digital  arteries. 

Collateral  branches. — We  observe  : 

1.  Xear  the  origin  of  the  artery,  and  very  often  from  the  posterior  radial 
artery  itself,  a  branch  which  anastomoses  above  the  pisiform  bone  with  the 
epicondyloid  artery,  forming  an  arch  whose  convexity  is  inferior  (Fig.  283,  3), 
and  which  has  been  already  noticed  as  the  supracarpal  or  superficial  palmar 

^  Tliis  artery,  the  superficial  plantar  of  Eigot,  represents  one  of  the  metacarpal 
palmar  branches  furnished  by  the  superficial  palmar  arch  in  Man  and  other  pentadactylona 
animals. 


570  THE  ABTERIES. 

arch,  in  contradistinction  to  the  suhcarpal  or  deep  palmar  arch,  the  source 
of  the  interosseous  arteries  of  the  metacarpus.  This  ramification  furnishes 
one  or  more  muscular  twigs  that  usually  anastomose  with  the  other  branches 
of  the  posterior  radial  artery ;  and  an  inferior  division,'  which  descends  in 
the  carpal  arch,  within  the  pisiform  bone,  to  the  superior  extremity  of  the 
metacarpus,  where  it  inosculates  with  the  radio-palmar  artery,  after  detach- 
ing several  carpal  ramuscules,  the  principal  of  which  turns  round  the  inferior 
border  of  the  pisiform  bone. 

2,  On  its  course,  numerous  and  fine  synovial  tendinous  and  cutaneous 
divisions. 

3.  A  trunk  springing  from  the  terminal  extremity  of  the  vessel,  between 
the  two  digital  arteries,  sometimes  even  from  one  of  these,  which  is  placed, 
at  the  posterior  face  of  the  principal  metacarpal  bone,  within  the  two 
branches  of  the  suspensory  ligament,  and,  passing  upwards,  soon  divides  into 
two  branches  ;  these  anastomose  by  inosculation  with  the  posterior  inter- 
osseous arteries  of  the  metacarpus,  after  giving  off  on  each  side  two  other 
ramuscules  which  wind  round  the  borders  of  the  middle  metacarpal  bone, 
receiving  the  dorsal  interosseous  arteries,  and  ramify  in  front  of  the  fetlock, 
on  the  anterior  face  of  the  cannon  bone,  and  in  the  texture  of  the  capsular 
ligament  of  the  metacarpo-phalangeal  articulation  (Fig.  283,  10). 

Terminal  branches. — These  are,  as  we  said,  the  digital  arteries,  whose  dis- 
position almost  exactly  repeats  that  of  these  vessels  in  the  posterior  limb, 
and  which  have  been  described  at  page  551. 

DIFFEEENTIAL  CHAKACTERS  IN  THE  AXILLARY  ARTERIES  OF  OTHER  THAN  SOLIPED  ANIMALS. 
1.  Axillary  Arteries  of  Ruminants. 

These  vessels  comport  themselves  in  their  origin,  course,  and  relations,  as  in  Solipeda. 
The  special  characters  they  present  in  their  distribution  are  as  follows : 

1.  Dorsal  artery. — This  arises  from  a  trunk  common  to  it  and  the  vertebral  artery, 
and  usually  leaves  the  thorax  by  passing  above  the  tirst  costo-vertebral  articulation.  Its 
subcostal  branch  proceeds  directly  from  the  above-named  trunk. 

2.  Superior  cervical  artery. — This  is  absent,  and  is  replaced  by  a  branch  of  the  dorsal 
artery,  but  particularly  by  the  superior  muscular  divisions  of  the  vertebral  artery. 

3.  Vertebral  artery. — JExtremely  voluminous,  and  terminates  in  the  muscles  of  the 
neck,  after  passing  through  the  foramen  of  the  axis ;  it  is  remarkable  for  the  considerable 
size  of  its  spinal  branches. 

4.  Inferior  cervical,  internal  and  external  thoracic  arteries. — These  do  not  present 
anything  worthy  of  special  consideration,  except  that  the  last  is  very  voluminous  in  the 
Ox  and  very  slender  in  the  Sheep,  and  supplies  the  satellite  arterial  branch  of  the 
cephalic  vein,  which,  in  Solipeds,  arises  from  the  inferior  cervical  artery. 

5.  Superscapular  artery.— This,  vessel  appears  to  us  to  be  absent  in  the  Sheep,  and 
its  place  supplied  by  the  divisions  of  the  inferior  cervical  artery. 

6.  Subscapular  artery. — The  scapulo-humeral  branch  gives  ofl  the  majority  of  the 
branches  destined  to  the  posterior  brachial  muscles. 

7.  Humeral  artery. — The  muscular  arteries  are  of  small  size,  particularly  the  deep 
humeral,  which  is  largely  replaced  by  the  scapulo-liumeral  branch. 

8.  Anterior  radial  artery.— This  comports  itself  similarly  to  that  of  the  Horse,  and 
is  liable  to  as  frequent  anomalies.  t 

9.  Posterior  radial  artery. — This  artery  follows  the  same  course  as  in  Solipeds  ;  only 
instead  of  furnishing  the  radio-palmar  artery  near  the  carpus,  at  the  point  where  it 
becomes  the  collateral  artery  of  the  cannon,  it  gives  off  that  vessel  much  highex,  and  near 
the  upper  third  or  middle  of  the  fore-arm.  Its  interosseous  branch,  lodged  in  the  deep 
channel  on  the  outside  of  the  bones  of  this  region,  where  the  radius  and  ulna  join,  is 
separated  into  two  branches  near  the  inferior  extremity  of  that  groove.  The  anterior  of 
these  ramifies  on  the  dorsal  face  of  the  carpus,  and  anastomoses  with  the  divisions  of  the 


Analogous  to  the  radio-ulnar  artery  of  Man. 


THE  BRACHIAL  OB  AXILLARY  ARTERIE.<.  571 

anterior  radial  artery ;  the  posterior  traverses  the  inferior  radioulnar  arch,  to  distribute 
the  majority  of  it«  branches  behind  the  carpal  articulations. 

10.' Rajio-piilmur  artery.— Xrum^,  as  we  have  already  seen,  from  tlie  posterior 
radial  artery,  towards  the  upper  third  of  tiie  fore-arm,  this  branch  liescends  tc  the 
superior  cxtieniity  of  the  metacarpus  iu  following,  as  in  the  Horse,  a  buperticLd  course, 
and  ends  in  four  metacarpal  interosseous  arteries  three  posterior  or  palmar,  and  one 
anterior  or  dorsal.  The  posterior  interosseous  arteries  are  very  irregular  and  incouitant 
in  tbeir  disposition;  they  communicate  with  each  other  by  several  branches,  and 
anastomose,  inferiorly,  either  with  the  lateral  digital  arteries,  the  collateral  of  the  cannon, 
or,  as  is  most  commonly  the  case,  with  a  branch  of  the  latter  vessel.  'I'hese  uiterosseous 
arteries  are  distinguished  iute  external,  midtUe,  and  internal ;  the  tirst  two  are  comprised 
between  the  posterior  face  of  the  metacarpus  and  the  suspensory  ligament ;  the  third, 
placed  at  the  inner  border  of  that  ligament,  is  more  considerable  than  the  others,  and  by 
its  volume  and  direction  represents  the  continuation  of  the  radio-palmar  artery.  The 
anterior  interosseous  artery  passes  through  the  foramen  at  the  superior  extremity  of  the 
metacarpus,  and  arriving  at  the  dorsal  face  of  the  bone,  it  bifurcates,  its  ascending 
branch  reaching  the  capsular  ligament  of  the  carpal  articulations,  where  it  anastomoses 
with  the  divisions  of  the  anterior  radial  and  interosseous  arteries  of  the  fore-arm;  the 
descending  is  lodged  in  the  anterior  grouve  of  the  metacarpal  bone,  and  joins  a  perforating 
branch  of  the  collateral  artery  of  the  cannon — a  branch  whicli  crosses  the  foramt  n 
pierced  towards  the  iuferiur  extremity  of  the  bony  diaphysis.  If  it  is  desired  to  ascertain 
the  signification  of  these  interosseous  arteries  in  their  relation  to  the  elements  composing 
the  foot  of  Kuminants,  we  readily  recognise :  in  the  posterior  median  artery,  the 
interosseous  palmar  of  the  two  great  digits;  in  the  posteiior  lateral  arteries,  the 
interosseuus  palmar,  intermediates  to  these  middle  digits,  and  the  rudimeuiary  lateral 
digits  represented  by  the  ergots  or  dew  claws  ;  and  in  the  single  anterior  artery,  the  dorsal 
interosseous  of  the  two  <;reat  iligits.  We  may  even  prove,  by  a  more  minute  examination, 
the  existence  of  dorsal  interosseous  arteries  corresponding  to  the  lateial  palmar  inter- 
osseous vessels. 

11.  Collateral  artery  of  the  cannon. — This  artery  follows  the  same  trai-k  as  in  the 
Horse,  as  far  as  the  lowerthird  or  fourth  of  the  metacarpus.  Arrived  at  this  point,  it 
abandons,  as  in  the  Horse,  a  branch  whose  divisions  communicate  with  the  interosseous 
arteries,  and  are  continued  by  the  digital  arteries,  three  in  number:  a  middle  and  tsxo 
lateral  (Fig.  .349). 

a.  The" communicating  branch  u-i.th  the  metacarpal  interosseous  arteries  very  eften 
arises  from  the  internal  digital  artery. 

It  is  insinuated  between  the  divisions  of  the  suspensoiy  ligament,  and  ascends  on  the 
posterior  face  of  the  metacarpus,  breaking  up  into  a  number  of  branches  which  near.y 
all  join  the  precited  arteries,  or  even  the  lateral  digital,  in  afttcting  a  variable  and 
complicated  disposition  which  it  is  needless  to  notice  here.  One  of  these  branches— a 
true  perforating  artery,  traverses  the  inferior  extremity  of  the  cannon  bone,  and  ascends 
in  its  anterior  groove  to  join  the  anterior  interosseous  artery,  after  detaching  ramutcules 
to  the  metacarpo-phalangeal  articulation. 

b.  The  middle  digital  artery  represents,  by  its  dimensions,  the  continuation  of  the 
collateral  artery  of  the  cannon,  and  is  a  very  voluminous  vessel.  It  is  at  first  inflected 
backwards  and  outwards  to  be  placed  on  the  posterior  face  of  the  perforatus  tendon;  thin  . 
it  descends  into  the  interdigital  sjiaee  by  passing  behind  the  great  sesamoid  sheath, 
beneath  the  ligament  uniting  the  two  claws.  Reaching  the  inferior  extremity  of  the 
first  phalanx,  it  divides  into  two  unaueal  arteries,  one  for  each  digit,  which  are  inflected 
forwards,  pass  beneath  the  internal  ligament  common  to  the  two  interphalangeal  articu- 
lations, and  enter  by  the  foramen  pierced  at  the  inner  side  of  tiie  pyratnidal  eminence 
into  the  internal  sinus  of  the  third  plialanx,  where  each  ramifies  in  the  same  manner 
as  the  plantar  ungueal  arteries  of  the  Horse. 

Several  collateral  branches,  remarkable  for  the  richness  of  their  arborisations,  escape 
from  this  median  artery  of  the  digits  and  its  terminal  divisions.  The  most  important  of 
these  are:  1.  At  the  middle  of  the  first  phalanx,  two  short  transverse  branches — a  right 
and  left,  passing  beneath  tiie  flexor  tendons  and  going  from  the  median  digital  artery 
to  the  lateral  arteries  of  the  digits;  2.  Nearly  at  the  same  point,  a  single  artery  which 
traverses  the  interdigital  space  from  behind  to  before,  to  pass  between  the  t«o  tendons 
of  the  common  extensor  of  the  phalanges,  whence  it  ramifies  on  the  anterior  fa'^e  of 
the  digits  by  ascending  along  the  anterior  median  vein,  and  anastomosing:  with  a 
descending  branch  of  the  perforating  artery  which  crosses  the  inferior  extremity  of  the 
metacarpus :  3,  A  double  branch  analogous  to  the  artery  of  the  plantar  cushion  of  the 
Horse,  having  its  origin  at  the  terminal  extremity  of  the  digital  artery,  often  arisins:  from 
the  ungueal  artery,  either  on  one  side  or  both,  and  communicating,  by  a  transverse  branch, 


572  THE  ARTERIES. 

with  its  homologiie ;  it  is  directed  backward  and  downward  on  the  bulb  of  the  heel, 
where  it  forms  an  anastomotic  arch  with  the  lateral  digital  artery ;  from  the  convexity 
of  this  arch,  which  is  turned  downwards,  there  escape  a  large  number  of  reticulating 
ramuscules,  destined  for  the  keratogenous  membrane  and  the  plantar  cushion. 

c.  The  lateral  digital  arteries  are  distinguished  into  internal  and  external.  The  first 
has  its  origin  at  the  bend  formed  by  the  collateral  of  the  cannon,  when  that  vessel  is 
inflected  on  the  posterior  ftice  of  the  perforatus  tendon  to  become  the  median  digital 
artery,  most  frequently  in  common  with  the  branch  whose  divisions  join  the  metacarpal 
interosseous  arteries.  The  second  commences  a  little  further  off,  after  having  received  u 
branch  from  either  this  communicating  artery,  or  from  the  external  interosseous  palmar ; 
it  is  not  rare  to  see  it  entirely  formed  by  one  of  these  bi  anches,  or  by  the  two  together, 
Whatever  may  be  their  point  of  origin,  the  lateral  digital  arteries  descend  on  the  ex- 
ceiitiic  side  of  the  digits,  without  the  flexor  tendons,  and  terminate  in  anastomosiu" 
by  inosculation  with  the  artery  of  the  plantar  cushion.  Among  the  collateral  branches 
emanating  from  these  arteries,  there  ought  to  be  distinguished  that  which  goes  to  tho 
ergot,  and  the  transverse  branch  thrown  across  between  each,  as  well  as  tuc  median 
digital  artery.' 

2.  Axillary  Arteries  of  the  Pig. 

Both  spring  separately  from  the  arch  of  the  aorta;  consequently,  there  is  no  anterior 
aorta.  The  right  artery,  or  hracMo-cephalic  trunk,  first  arises ;  the  left  comes  immediately 
after. 

a.  The  hrarhio-cephalic  trunk  is  directed  forwards,  under  the  inferior  face  of  the  trachea, 
and  leaves  the  thorax  to  reach  the  inner  face  of  the  anterior  limb,  as  in  other  animals. 

It  furnishes  successively  : — 

1.  At  the  fii'st  rib,  and  below,  the  two  carotid  arteries,  rising  singly  from  nearly  the 
same  point. 

2.  Directly  opposite  to  these  vessels,  a  trunk  remarkable  for  the  complication 
attending  its  mode  of  distribution ;  it  is  directed  upwards  and  backwards,  on  the  side 
of  the  trachea  and  longus  colli,  crosses  the  interval  between  the  second  and  third  ribs, 
and  elevates  itself  into  the  deep  cervical  muscles,  to  terminate  in  the  vicinity  of  the  nape 
of  the  neck.  It  evidently  represents  the  deep  or  superior  cervical  artery.  Near  its  origin 
it  gives  oiFthe  vertebral  artery,  whose  mode  of  termination  is  exactly  the  same  as  in  the 
Horse.  Beyond  this,  it  detaches  the  dorsal  artery,  which  ascends  into  the  muscles  of 
the  withers,  after  passing  into  the  first  intercostal  space.  Lastly,  it  supplies,  before 
leaving  the  thorax,  the  subcostal  or  superior  intercostal  artery,  j^laced  across  the  superior 
extiemities  of  the  third,  fourth,  and  fifth  i"ibs. 

3.  Always  within,  but  a  little  more  forward  than  the  first  rib,  a  voluminous  inferior 
cervical  artery,  divided  into  several  ascending  bi  anches ;  and  the  tivo  thoracic  arteries, 
which  offer  nothing  particular  for  description. 

4.  Without  the  thorax,  on  the  internal  face  of  the  scapulo-humeral  articulation,  the 
humeral  or  subscapular  arteries ;  the  first,  less  voluminous  than  the  other,  presents,  from 
its  origin  to  the  distribution  of  its  branches  in  the  foot,  a  disposition  essentially 
resembling  that  observed  in  this  vessel  in  Ruminants ;  the  second  courses  upwards  in 
the  space  between  the  subscapular  muscle  and  the  teres  major,  and  soon  divides  into 
two  terminal  branches,  one  of  which  continues  the  primitive  track  of  the  vessel,  while 
the  other  passes  beneath  the  subscapular  muscle  to  carry  its  ramifications  into  the 
antero-external  muscles  of  the  shoulder,  furnishing  m  its  course :  1,  The  great  dorsal 
arteiy,  throwing  a  part  of  its  ramifications  into  the  olecranian  muscles:  2,  A  volu- 
minous branch  which  provides  the  greater  number  of  the  divisions  given  off",  in  the 
Horse,  by  the  deep  humeral  and  prehumeral  arteries ;  3,  Two  articular  branches,  one 
of  which  closely  represents  the  superscapular  artery. 

b.  The  left  brachial  trunk  only  differs  from  the  right  in  the  disposition  of  the 
superior  cervical,  dors'd,  and  vertebral  arteries,  which  have  distinct  origins;  the  two 
last  are  very  close  to  each  other,  and  the  first  furnishes  the  sidjcostal  branch. 

3.  Axillary  Arteries  of  Carnivora.  ft 

These  arise  separately  from  the  convexity  of  the  arch  of  the  aorta,  as  in  the  Pig,  and 
furnish  successively,  apart  from  the  carotids,  sjiccial  branches  of  the  brachio-cephalio 
trunk : — 

1.  A  voluminous  trunk,  the  common  origin  of  the  dorsal,  superior  cervical,  and  sub- 


'  In  several  instances,  we  have  seen  the  lateral  digital  arteries  stop  at  this  trails  verse 
anastomosis,  which  then  received  them  entirely. 


THE  BRACHIAL  OB  AXILLARY  ARTERIES.  573 

costal  or  superior  intercostal  arteries  the  first  passes  between  tlie  two  anterior  ribs  ;  tho 
second  in  front  of  tho  first ;  the  third  across  the  internal  face  of  the  first,  second,  and 
third  ribs  near  their  cartilages,  where  it  emits  ascending  and  descending  intercostal 
blanches. 

2.  The  vertebral  artery,  anastomosing,  as  in  Solipeds,  with  a  retrograde  branch  from 
the  occipital  artery ;  it  snpplements,  iu  very  great  part,  the  superior  cervical,  whose 
volume  is  diminutive,  and  which  is  only  distributed  to  the  posterior  part  of  the  neck, 

3.  The  inferior  cervical  artery,  giviug  otf  the  pectoral  branches. 

4.  The  internal  thoracia  artery,  remarkable  for  its  large  volume,  and  for  a  superficial 
division  chiefly  destined  to  the  mammse,  which  joins  an  analogous  branch  from  the 
external  pudic  artery. 

5.  An  external  thoracic  branch,  whose  origin  more  resembles  that  of  the  super- 
scapular  artery,  which  appears  to  be  absent. 

6.  The  subscapular  artery.  After  furnishing  this  vessel,  the  brachial  trunk  is  pro- 
longed by  the  humeral  artery,  which  we  will  now  examine  in  detail. 

Humeral  Artery. — Placed  at  first  immediately  behind  the  coraco-radial  or  biceps 
muscle,  this  vessel  descends  beneath  the  round  pronator,  and  divides  at  the  superior 
extremity  of  the  radius  into  two  terminal  brauclies ;  these  are  the  ulnar  and  radial 
arteries. 

It  detaches  on  its  course  collateral  branches,  analogous  to  those  which  have  been 
described  for  Solipeds,  and  among  which  is  a  thin  vessel,  a  vestige  of  the  anterior  radial 
artery,  that  passes  beneath  the  terminal  extremity  of  the  biceps  to  supply  the  muscles 
covering,  anteriorly,  the  articulation  of  the  elbow. 

Ulnar  artery. — Much  smaller  than  the  radial,  this  vessel  transmits,  near  its  origin, 
the  interosseous  artery,  which  sometimes  proceeds  directly  from  the  humeral  artery,  and 
whose  calibre  always  exceeds,  in  animals,  that  of  the  ulnar  artery.  The  latter  is  directed 
obliquely  outwards  and  downwards,  passing  under  the  perforans,  and  gains  the  internal 
face  of  the  anterior  ulnar  or  oblique  flexor  of  the  metacarpus,  where  it  lies  beside  the 
ulnar  nerve,  to  descend  with  it  inside  the  unciform  bone,  and  join  the  posterior  interosseous 
artery,  or  one  of  its  terminal  branches.  On  its  track  it  gives  otf  a  number  of  muscular 
or  cutaneous  branches,  several  of  which  anastomose  with  the  internal  collateral  artery 
of  the  elbow,  as  well  as  with  divisions  of  the  radial  artery. 

Interosseous  artery.— This  artery  is  placed  between  the  cubitus  and  radius,  under- 
neath the  square  pronator,  and  is  prolonged  to  the  lower  third  of  the  fore-arm,  where  it 
separates  into  two  branches — the  anterior  and  posterior  interosseous  arteries,  after 
abandoning  on  its  way  several  branches,  mostly  anterior,  which  enter  the  antibrachial 
muscles  by  traversing  the  space  comprised  between  the  two  bones  of  the  fore-arm,  the 
principal  escaping  by  the  radio-ulnar  arch. 

The  anterior  interosseous  artery,  after  passing  between  the  radius  and  ulna,  descends 
on  the  anterior  face  of  the  carpus,  where  its  divisions  meet,  inwardly,  the  collateral 
ramuscules  of  the  radio-palmar  artery,  and  outwardly,  the  arborisations  of  a  branch  from 
the  posterior  interosseous  artery,  forming  with  these  vessels  a  wide-meshed  plexus, 
from  which  definitively  proceed  several  filaments  that  join  the  dorsal  interosseous 
metacarpal  arteries. 

The  posterior  interosseous  artery  may  be  regarded,  by  its  volume  and  direction,  as  the 
continuation  of  the  interosseous  trunk.  After  emerging  from  beneath  the  square  pronator, 
it  detaches  an  internal  flexuous  branch  anastomosing  with  the  radio-palmar  artery,  then 
several  external  musculo-cutaneous  branches ;  after  which  it  is  placed  within  the 
pisiform  bone,  where  it  divides  into  two  branches,  after  receiving  the  ulnar  artery.  The 
smallest  of  these  branches  anastomoses  by  inosculation  with  tlie  superficial  palmar  arch; 
the  other,  larger  and  deeper-seated,  is  carried  in  front  of  the  flexor  tendons,  beneath  the 
aponeurosis  covering  the  interosseous  muscles,  across  the  superior  extremity  of  these,  and 
so  forming  the  deep  palmar  arch,  which  unites  witli  a  thin  tilament  from  the  radio-palmar 
artery.  This  arch  supplies,  with  some  ramuscules  destined  to  the  muscles  of  the  hand 
(or  paw),  eic/ht  interosseous  metacarpal  arteries :  four  posterior  or  palmar,  which  are  united 
by  their  inferior  extremity  with  the  collaterals  of  the  digits,  after  giving  several  divisions 
to  the  muscles  of  the  hand;  and /our  anterior  or  dorsal,  traversing  the  superior  extremity 
of  the  intermetacarpal  spaces,  like  the  perforating  arteries  in  Man,  joining  the  anterior 
interosseous  branches  of  the  fore-arm,  and  descending  afterwards  into  the  intermetacarpal 
spaces,  to  unite  with  the  collateral  arteries  of  the  digits  at  the  metacarpo-phalangeal 
articulations. 

Radial  artery :  the  posterior  radial  of  the  other  animals.  Lying  alongside  the 
Ions:  flexor  of  the  thumb  and  the  perforans  muscle,  this  artery  follows  the  inner  face  of 
the  perforatus  muscle,  and  curving  outwards  to  be  united  to  a  branch  fiom  tlie  posterior 
antibrachial  interosseous  artery,  forms  the  superficial  palmar  arcade,  from  which  escape 


574 


THE  ABTERIES. 


Fig.  284. 


ARTERIES   OF   THE   HUMAN 
FORE-ARM. 

1,  Lower  part  of  biceps;  2, 
Inner  condyle  of  humerus ; 
3,  Deep  portion  of  pronator 
radii  teres ;  4,  Supinator 
longus ;  5,  Flexor  longus 
pollicis ;  6,  Pronator  quad- 
ratus  ;  7,  Flexor  profundus 
digitorum ;  8,  Flexor  carpi 
ulnaris ;  9,  Annular  liga- 
ment ;  10,  Brachial  artery  ; 
11,  Anastomotica  longus 
magna,  inosculating  above 
with  the  inferior  profunda, 
and  below  with  the  anterior 
ulnar  recurrent ;  12,  Radial 
artery ;  13,  Radial  recurrent 
inosculating  with  the  supe- 
rior profunda ;  14,  Super- 
ficialis  voire ;  15,  Ulnar  ar- 
tery ;  16,  Superficial  palmar 
arch,  giving  off  digital 
branches  to  three  fingers 
and  a  half;  17,  Magna 
pollicis  and  radialis  indicis  ; 
20,  Posterior  interosseous. 


four  branches — the  palmar  or  collateral  of  the  digits. 
These  are  at  first  situated  between  the  perforatus  ami 
perforans  tendons,  and  reach  the  superior  extremity  of 
the  interdigital  spaces,  where  they  receive  the  metacarpal 
interosseous  arteries,  and  comport  themselves  in  the  fol- 
lowing manner:  the  internal  goes  to  the  thumb;  the 
secojid— counting  from  within  outwards— gains  the  con- 
centric side  of  the  index ;  the  third,  the  largest,  divides 
into  tw^o  branches  which  lie  alongside  the  great  digits; 
the  last  goes  to  the  external  digit. 

COMPARISON   OF   THE   AXILLARY   ARTERIES   IN   MAN   WITH 
THOSE    OF   ANIMALS. 

The  arteries  of  the  thoracic  limbs  and  head  arise  sepa- 
rately from  the  arch  of  the  aorta ;  consequently,  in  Man 
there  is  no  anterior  aorta. 

The  vessel  of  the  limb  that  represents  the  axillary  of 
animals  is  here  resolved  into  two  portions  :  the  stibclavian 
artery  and  axillary  artery. 

The  SUBCLAVIAN  ARTERY  has  uot  the  same  oiigin  on 
both  sides;  on  the  right  it  arises  from  the  aorta  by  a  trunk 
common  to  it  and  the  carotid  of  that  side — tlie  brachio- 
cephalic trunk  {arteria  innominata) ;  while  the  left  is 
detached  separately  from  the  most  distant  part  of  the 
aortic  arch.  The  subclavian  vessels  extend  to  the  in- 
ferior border  of  the  clavicles,  and  furnish  seven  impoi  tant 
collateral  branches,  which  are  present  in  the  domesticated 
animals.     They  are  : — 

1.  The  vertebral  artery,  situated  in  the  vertebral  fora- 
mina of  the  cervical  vertebrae,  as  far  as  the  axis ;  there  it 
anastomoses,  as  in  Solipeds,  with  a  branch  of  the  carotid, 
enters  the  spinal  canal  by  the  foramen  magnum,  and 
unites  with  its  fellow  at  tlie  lower  border  of  the  pons 
Varolii  to  form  the  basilar  artery  which,  in  the  Horse, 
comes  from  the  cerebro-spinal  artery  of  the  occipital. 

2.  The  inferior  thrjroid,  whote  origin  and  some  bianches 
we  find  in  the  ascending  branch  (ascending  cervical)  of 
the  inferior  cervical  artery  in  the  Horse 

3.  The  internal  mammary  artery  divides  into  two 
branches  at  the  xiphoid  appendix  of  tlie  sternum. 

4.  The  superior  intercostal  artery,  whose  analogue  we 
see  in  Solipeds,  in  the  subcostal  branch  of  the  dorsal. 

5.  The  superscapular  artery,  present  in  all  animals 
and  disposed  in  tlie  same  manner. 

6.  The  transverse  cervical  (traiisvema  colli),  represented 
by  the  extra-thoracic  branches  of  the  dorsal  artery. 

7.  The  deep  cervical  (cervicalis  profunda)  corresponds 
to  the  superior  cervical  in  the  Horse. 

The  AXILLARY  ARTERY,  or  extra-thoracic  portion  of  the 
subclavian  trunk,  extends  to  the  external  border  of  the 
pectoral  muscle,  where  it  is  continued  by  the  humeral 
artery.  The  axillary  gives  off:  the  thoracica  acromialis, 
resembling  the  descending  branch  of  the  inferior  cervical 
artery  of  large  quadrupeds  ;  the  external  mammary  ,  sub- 
scapular ;  and  poderior  and  anterior  circumflex,  branches 
of  the  preceding  in  Solipeds. 

Humeral  (BRAcnrAL)  Artery. — This  artery  extends 
from  the  external  border  of  tlie  pectoral  muscle  to  the 
bend  of  tlie  elbow :  here  it  divides  into  two  terminal 
branches — the  ulnar  and  radial. 

In  its  course  it  gives  off  several  muscular  branches, 

18,  Posterior  ulnar  recurrent ;  19,  Anterior  interosseous ; 


THE  BRACHIAL  OR  AXILLARY  ARTERIES.  575 

and  an  external  and  internal  collateral  of  the  elbow  (collateralis  ulnaris  superior  and 
inferior).  In  the  lower  third  of  the  arm,  the  brachial  artery  is  comprised  between 
tiie  brachialis  anticus  and  inner  border  of  the  biceps;  so  tliat,  during  flexion,  and 
especially  active  and  forced  flexion,  of  the  fore-arm  on  the  arm,  in  vigorous  subjects,  the 
circulation  is  arrested  in  the  vessels  of  the  hand. 

The  radial  artery  of  Man  is  represented  in  the  Horse  by  the  posterior  radial  artery. 
It  is  directed  downward  and  a  little  Inward,  supposing  the  hand  to  be  in  a  state  of 
pronation ;  it  crosses  the  carpus  in  front  of  the  trapezium  and  scaphoides,  iit  the  bottom 
of  the  anatomical  snutt-box,  and  beneath  the  flexor<  tendons  of  the  phalanges  furms  the 
deep  palmar  arch,  finally  anastomosing  with  a  branch  of  the  ulnar  at  the  hypothenar 
eminence.  Along  its  course  it  furnishes  muscular  branches:  the  curpea  anterior ;  radio- 
palmar,  which  passes  outwards,  and  unites  with  a  branch  of  the  ulnar  artery  to  form  the 
superficial  palmar  artery  ;  the  dormlis  polUeis  ;  the  carpea  posterior,  which  concurs  in 
the  formation  of  the  dorsal  arch  of  the  carpus  that  gives  origin  to  the  dorsal  interosseous 
branches. 

The  ulnar  artery,  formed,  in  Solipeds,  by  the  anterior  radial,  passes  downward  and 
outward ;  it  is  at  first  covered  by  the  great  pronator  muscles,  great  and  small  palmar, 
and  superficial  flexor ;  lower,  it  is  only  protected  by  the  antibracliial  aponeurosis  and 
the  skin.  On  the  anterior  face  of  the  carpus,  it  passes  within  the  pisiform  bone,  and 
anastomoses  with  the  radio-palmar  artery,  whence  results  the  superficial  palmar  arch. 
It  gives  rise  to  two  recurrent  arteries  that  ascend  to  receive  the  collateral  vessels  of  the 
elbow,  then  to  a  trunk  seen  in  animals,  and  which  divides  into  the  anterior  and  posterior 
interosseBe. 

The  three  arches  that  exist  in  the  vicinity  of  the  carpus,  the  constitution  of  which 
has  been  already  given,  are  distributed  in  the  following  manner 

The  superficial  palmar  arch  is  situated  at  the  surface  of  the  flexor  tendons ;  from  its 
convexity  it  emits  four  or  five  metacarpal  branches :  the  first  reaches  the  external 
border  of  the  little  finger  as  the  external  collateral  of  that  organ  the  other  four 
are  lodged  in  the  interosseous  spaces,  and  when  they  reach  the  roots  of  the  fingers 
they  bifurcate  and  constitute  the  external  or  internal  collateral  arteries  of  the  five  fingers. 
The  deep  palmar  arch  furnishes :  articular  branches  to  the  wrist,  the  perforating  branches 
which  cross  the  interosseous  spaces  to  unite  with  the  dorsal  interossese ;  the  palmar 
interosseie,  wliich  join  the  superficial  interosseas  before  their  division  into  collateral 
branches.  Lastly,  the  carpal  dorsal  arch  gives  off  the  dorsal  interossex,  which  receive 
perforating  filaments  above  and  below  the  metacarpus,  and  are  expended  in  the 
articulations  and  skin  of  the  fingers. 

Article  VII. — Prikiitive  (or  Common)  Carotid  Arteries. 
(Figs.  282,  14  ;  286,  1.) 

Origin.—  These  two  vessels  (named  from  Kapa,  the  head)  arise  from  the 
right  axillary  artery,  at  a  short  distance  from  its  origin,  by  a  common 
trunk,  the  cephalic,  which  is  detached  at  a  very  acute  angle,  and  is  directed 
forward  beneath  the  inferior  face  of  the  trachea,  and  above  the  anterior  vena 
cava,  to  terminate  near  the  entrance  to  the  chest  by  a  bifurcation  that 
commences  the  two  common  carotids. 

Course. — Each  of  these  arteries  afterwards  ascends  in  the  midst  of  an 
abundant,  though  dense,  connective  tissue,  along  the  trachea,  at  first  beneath 
that  tube,  then  at  its  side,  and  finally  a  little  behind  its  lateral  plane. 
Each  carotid  arrives  in  this  way  at  the  larynx  and  guttural  pouch,  where  it 
divides  into  three  branches. 

Belations. — In  its  course,  this  vessel,  independently  of  the  connection 
between  it  and  the  trachea,  affects  the  following  relations : — 

Throughout  its  entire  length,  it  is  accompanied  by  the  cord  that  rasults 
from  the  union  of  the  pneumogastric  nerve  with  the  cervical  portion  of  tho 
sympathetic,  and  by  the  recurrent  nerve ;  the  latter  is  placed  below  or  in 
front  of  the  vessel,  from  which  it  is  somewhat  distant  in  the  lower  part  of 
the  neck ;  the  first  is  situated  above  or  behind  the  artery,  and  lies  close  to 
it. 

It  also  corresponds :  behind,  in  its  upper  two  thirds,  to  the  longus  colli 


576  THE  ARTERIES. 

and  the  rectus  anticus  major;  outwardly,  to  the  scalenus,  towards  the 
inferior  extremity  of  the  neck,  and  to  the  subscaj^ulo-hyoideus,  which 
separates  the  artery  and  jugular  vein  in  the  middle  and  superior  part.  But 
near  the  entrance  to  the  chest,  these  two  vessels  are  in  direct  relationship, 
the  vein  below  and  the  artery  above. 

It  is  also  to  be  noted,  that  the  glands  at  the  entrance  of  the  chest  are  in 
contact  with  the  carotids,  and  that  the  left  artery  corresponds,  besides,  to 
the  oesophagus. 

Collateral  Branches. — The  branches  furnished  by  the  common  carotid 
on  its  coui'se  are  somewhat  numerous,  but  they  are  of  such  inconsiderable 
diameter  that  their  successive  emission  does  not  sensibly  vary  the  calibre 
of  the  vessel  from  which  they  emanate ;  so  that  the  carotids  represent,  from 
their  origin  to  their  termination,  two  somewhat  regular  cylindrical  tubes. 
These  collateral  branches  are  destined  either  to  the  muscles  of  the  cervical 
region,  or  to  the  oesophagus  and  trachea.  Two  of  them,  the  thyro-laryngeal 
and  accessory  thyroid  arteries,  will  occupy  us  in  a  special  manner. 

Thyro-laryngeal  Artery  (Fig,  282,  14"). — This  vessel,  which  corre- 
sponds exactly  to  the  superior  thyroid  artery  of  Man,^  arises  from  the 
common  carotid  at  a  short  distance  from  its  termination,  a  little  behind  the 
larynx  or  above  the  thyroid  body  ;  it  passes  on  that  organ,  into  which  it 
enters  by  two  principal  branches  that  turn  round  its  superior  extremity  and 
anterior  border,  after  sending  two  branches  to  the  larynx — a  superior,  des- 
tined also  to  the  pharyngeal  walls ;  and  an  inferior,  much  more  considerable, 
which  is  exclusively  distributed  to  the  laryngeal  aj^paratus. 

It  sometimes  happens  that  the  thyro-laryngeal  artery  is  found  divided 
from  its  origin  into  two  quite  distinct  branches,  each  furnishing  a  laryngeal 
and  a  thyroid  division,  as  in  figure  286,  3,^ 

We  have  already  remarked  the  disproportion  that  exists  between  the 
considerable  calibre  of  the  branches  sent  by  this  artery  to  the  thyroid  body, 
and  the  slender  volume  of  that  organ  ;  so  that  it  will  at  present  suffice  to 
remind  the  student  of  this  peculiarity. 

Accessory  Thyroid  Artery  (Figs.  282  14'  ;  286,  2). — The  origin  of 
this  vessel  precedes  that  of  the  first ;  it  is  much  smaller,  and  enters  the 
thyroid  body  by  the  posterior  or  inferior  extremity  of  this  glandiform 
lobe. 

This  artery  often  sends  only  some  excessively  fine  ramuscules  to  the 
thyroid  gland,  and  expends  itself  almost  entirely  in  the  cervical 
muscles.^ 

Terminal  Branches. — The  three  branches  which  terminate  the  common 
carotid  are  the  occipital,  and  internal  and  external  carotid  arteries ;  the  latter 
is  incomparably  larger  than  the  other  two,  which  only  appear  to  be  collateral 
twigs  from  the  principal  vessel.  It  is  these  branches  which  distribute  the 
blood  to  the  various  parts  of  the  head.  We  will  devote  three  special 
paragraphs  to  theii-  study ;  but  their  preparation  will  previously  demand 
some  notice. 

•  We  would  have  given  it  the  same  name  if  we  could  have  found  the  true  repre* 
sentative  of  the  inferior  thyroid  artery. 

^  It  was  doubtless  a  case  of  this  kind  that  Kigot  had  before  him  when  he  described 
the  above  vessel,  and  made  two  arteries  of  it — the  thyroid  and  laryngeal.  But,  we 
repeat,  this  example  is  only  exceptionally  met  with,  and  does  not  authorize  its  being 
supposed  to  be  the  rule,  and  cause  the  creation  of  a  distinct  thyroid  and  laryngeal  artery; 
since  each  branch  of  the  vessel  is  distributed  to  the  larynx  and  thyroid  body  at  the 
same  time. 

*  We  regard  it  as  the  analogue  of  the  middle  thyroid  of  Man. 


THE  COMMON  CAROTID  ARTERIES.  577 

Preparation  of  the  arteries  of  the  head. — After  carefully  removing  tlie  skin,  dissect  the 
superficial  arteries  of  one  side — that  is,  the  external  maxillary,  maxillo-muscular,  the 
temporal  trunk,  and  the  posterior  auricular  arteries,  excising  the  parotid  to  expose  the 
origin  of  the  three  last-named  vessels.  On  the  opposite  side,  the  deep  arteries  are 
prepared,  after  disposing  of  the  branch  of  the  maxilla,  as  in  the  preparation  of  the 
muscles  of  the  tongue ;  the  orbital  and  zygomatic  processes  being  removed  in  three 
sections  with  the  saw,  as  in  figure  2SG,  whicli  will  serve  as  a  guide  iu  the  dissection  of 
all  these  arteries. 

OCCIPITAL    AKTERY.      (Fig.  286,  6.) 

The  occipital  artery  is  a  slightly  flexuous  vessel,  lying  beside  the  upper 
third  of  the  internal  carotid.  It  ascends  beneath  the  transverse  process 
of  the  atlas  in  passing  behind  the  guttural  pouch,  between  the  maxillary 
gland  and  the  straight  anterior  muscles  of  the  head.  It  then  insinuates 
itself  between  the  small  lateral  sti'aight  muscle  and  the  inferior  arch  of  the 
above  vertebra,  to  pass  through  its  anterior  foramen,  and  terminate  by  two 
branches,  after  coursing  along  the  short  fissure  which  unites  this  foramen 
with  the  superior.  In  its  track,  this  artery  is  crossed,  outwai'dly,  by  the 
pneumogastric  and  spinal  nerves,  and  the  occipital  nerve  of  the  great  sym- 
pathetic, and  is  accompanied  by  the  divisions  of  the  inferior  branch  of  the 
fii'st  pair  of  cervical  nerves. 

The  two  teiTninal  branches  of  the  vessel  are  the  occipito-muscular  and 
cerebrospinal  arteries. 

The  collateral  branches  are  three  in  number,  and  in  the  order  of  their 
emission  are  named  :  1,  The  prevertebral  artery ;  2,  The  mastoid  artery ;  3, 
The  atloido-muscular  artery. 

Collateral  Branches. — 1.  Prevertebral  Artery  (Fig.  286,  9). — The 
smallest  of  all  the  branches  emanating  from  the  occipital,  this  artery  is 
detached  at  a  very  acute  angle,  and  immediately  divides  into  several 
filaments,  some  muscular,  the  others  meningeal.  The  majority  of  the  fii'st 
pass  between  the  occipito-atloid  articulation  and  the  small  anterior  rectus 
muscle  of  the  head,  and  expend  themselves  either  in  that  muscle,  or  the 
great  rectus ;  the  second,  generally  two  in  number,  are  always  very  slender, 
and  reach  the  dura  mater  by  entering,  one  through  the  posterior  foramen 
lacerum,  the  other  by  the  condyloid  foramen. 

2.  Mastoid  Artery  (Fig.  286,  8). —  This  vessel  arises  at  an  acute 
angle  above  the  preceding,  and  goes  towards  the  mastoid  foramen  by 
creeping  on  the  external  sm-face  of  the  styloid  process  of  the  occipital  bone, 
beneath  the  small  oblique  muscle  of  the  head.  It  enters  the  parieto- 
temporal canal  by  tliis  foramen,  to  anastomose  by  inosculation  with  the 
spheno-spinous  artery. 

In  its  course  it  describes  a  curve  downwards,  and  throws  off  a  large 
number  of  collateral  branches.  Among  these  are  some  which  originate 
before  the  artery  enters  its  bony  canal,  and  which  are  destined  for  the 
muscles  of  the  nape  of  the  neck.  Others  arise  in  the  interior  of  this  canal, 
and  escape  from  it  by  the  orifices  that  cribble  the  temporal  fossa,  to  expend 
themselves  in  the  temporal  muscle.     Some  ramuscules  reach  the  dura  mater. 

We  have  seen  the  mastoid  artery  arise  directly  from  the  common 
carotid,  and  furnish  a  parotideal  branch. 

3.  Atloido-muscular  or  Eetrograde  Artery  (Fig.  286,  7), —  This 
branch  is  not  constant,  and  when  it  does  exist  it  presents  a  variable  volume.  It 
is  detached  from  the  occipital,  underneath  the  transverse  process  of  the  atlas, 
by  forming  with  the  parent  branch  a  right,  or  even  an  obtuse  angle  ;  it  is 
directed  backwards,  traverses  the  inferior  foramen  of  the  process  of  the 


578  THE  AETEBIES. 

atlas,  places  itself  beneath  tbe  atlo  axoid  muscle,  and  in  a  flexuous  manner 
advances  to  meet  the  vertebral  artery,  which  it  directly  joins,  after  giving 
off  some  branches  to  the  great  oblique  and  neighbouring  muscles.  This 
anastomosis  is  the  means  of  establishing  a  collateral  communication  between 
the  vertebral  artery,  and  the  divisions  furnished  by  the  common  carotid  ;  so 
that  these  two  arteries  can  mutually  assist  or  supplant  each  other. 

Terminal  Branches. — -1.  Occipito-muscular  Artery  (Fig.  286, 10). — 
Covered  at  its  origin  by  the  great  oblique  muscle,  the  occipito-muscular 
artery  is  directed  transversely  inwards  to  the  surface  of  the  posterior 
straight  (recti)  muscles,  and  soon  separates  into  several  branches — ascending 
and  descending — mixed  with  the  nervous  divisions  of  the  first  superior 
cervical  branch,  all  of  which  are  destined  to  the  muscles  and  integuments  of 
the  occipital  region.  The  descending  branches  anastomose  with  the  ter- 
minal divisions  of  the  superior  cervical  artery. 

2.  Cekebro-spinal  Artery.  ^ — This  vessel  enters  the  spinal  canal  by  the 
anterior  foramen  of  the  atlas,  traverses  the  dura  mater,  and  divides  into  two 
branches  on  the  inferior  face  of  the  spinal  cord.  Of  these  two  branches,  the 
anterior  is  united,  by  convergence,  with  the  analogous  branch  of  the 
opposite  artery  on  its  arrival  at  the  middle  of  the  length  of  the  bulb  (medulla 
oblongata),  and  so  forms  the  basilar  trunk ;  the  other  passes  backwards,  and 
constitutes  the  origin  of  the  median  spinal  artery,  by  anastomosing,  after  a 
short  course,  with  the  corresponding  branch  of  the  other  cerebro-spinal 
artery.  There  results  from  this  distribution  a  kind  of  vascular  lozenge, 
situated  at  the  lower  face  of  the  medulla  oblongata,  which  receives  in  its 
middle  the  two  cerebro-spinal  arteries.  This  regular  arrangement  is  not, 
however,  always  observed  ;  these  arteries  may  unite  at  the  posterior  extremity 
of  this  lozenge,  as  is  shown  in  figure  285. 

Basilar  trunk. — This  is  a  single  vessel  which  creeps  in  a  somewhat 
flexuous  manner  on  the  inferior  face  of  the  medulla  oblongata,  beneath  the 
visceral  arachnoid  membrane,  and  passing  over  the  annular  protuberance 
(pons  Varolii),  terminates  at  the  anterior  border  of  this  portion  of  the 
encephalic  isthmus,  by  anastomosing  with  the  two  posterior  cerebral  arteries 
(Fig.  285,  11,  11). 

On  its  course  it  gives  off: 

1.  A  multitude  of  plexuous  ramuscules,  which  enter  the  substance  of  the 
medulla  oblongata  and  the  pons  Varolii,  or  are  distributed  to  the  roots  of  the 
nerves  emanating  from  the  medulla  oblongata. 

2.  The  posterior  cerebellar  arteries,  vessels  liable  to  numerous  anomalies 
in  their  origin ;  they  usually  arise  from  the  basilar  trunk  at  a  right  angle, 
behind  the  posterior  border  of  the  pons  Varolii,  and  bend  outwards,  one  to 
the  right,  the  other  to  the  left,  by  gliding  along  the  surface  of  the  bulb 
(medulla  oblongata),  whose  external  border  it  thus  reaches,  and  is  then 
inflected  backwards  beneath  the  cerebellar  plexus  choroides,  whence  they 
spread  their  ramifications  on  the  lateral  and  posterior  parts  of  the  cere- 
bellum. 

3.  The  anterior  cerebellar  arteries,  two  or  three  on  each  side,  only  one  of 
which  is  constant.  These  vessels  are  very  variable  in  their  disposition,  and 
arise  from  the  terminal  extremity  of  the  basilar  trunk,  in  front  of  the  pons 
Varolii,  and  sometimes  even  from  the  posterior  cerebral  arteries.  Usually 
united  in  fasciculi,  they  are  directed  outwards  and  a  little  backwards  in 
turning  round  the  cerebral  pedunculi,  and  plunge  into  the  anterior  jiart  of 
the  cerebellum. 

4.  Two  branches  anastomosing  with  the  internal  carotid  artery ;    these 


THE  COMMON  CAROTID  ARTERIES.  579 

brandies  are  not  constant,  and  are  most  frequently  met  with  in  the  Ass. 
They  begin  at  the  basilar  trunk,  in  front  of  the  posterior  border  of 
the  annular  protuberance,  traverse  the  dura  mater  to  enter  the  cavernous 
sinus,  and  join  the  carotid  arteries  at  their  second  curvature. 

Posterior  Cerebral  Arteries. — These  terminate  the  basilar  trunk,  and 
separate  into  right  and  left  of  it,  behind  the  pisiform  tubei'cle  (Fig.  285,  11). 
They  first  proceed  forward,  receiving  posterior  communications,  then  pass 
outward  and  upward,  to  turn  round  the  cerebral  peduncles  and  reach  Bichat's 
fissure.  On  their  course,  they  furnish  a  multitude  of  hair-like  twigs  that  enter 
the  substance  of  the  peduncles ;  but  the  principal  branches  they  give  off  are 
flexuous,  and  directed  either  toAvards  the  great  cerebral  fissure,  where  tliey 
terminate,  to  the  posterior  extremity  of  the  hemisphere  of  the  cerebrum,  or  its 
interior,  to  the  plexus  chorides  more  particularly,  or  even  to  tlie  cerebellum. 
The  disposition  and  number  of  these  branches  are  very  variable. 

Median  Spinal  Artery. — A  very  long  vessel,  lodged  in  the  inferior 
fissure  of  the  spinal  cord,  and  measuring  the  whole  extent  of  that  organ, 
which  it  follows  from  before  to  behind.  It  is  from  this  artery  that  are 
given  off  the  branches  which  cover  with  their  arborisations  the  medullary 
tissue,  or  penetrate  its  substance.  This  emission,  which  ought  soon  to 
exhaust  the  artery,  does  not  sensibly  diminish  its  diameter,  as  it  receives  on 
both  sides,  during  its  course,  numerous  additional  filaments.  Two  series  of 
ramuscules,  in  fact,  emanate  either  from  the  vertebral,  intercostal,  lumbar, 
or  sacral  arteries,  and  enter  the  spinal  canal  by  the  intervertebral  foramina, 
and  go  to  join  this  artery.  Generally,  however,  they  do  not  pass  to  the 
spimil  cord  until  they  have  anastomosed  with  each  other  outside  the  dura 
mater,  so  as  to  form  on  the  floor  of  the  vertebral  canal  two  lateral  conduits 
placed  beside  the  venous  sinus,  and  united  by  transverse  anastomoses  ;•  this 
disposition  is  most  evident  in  the  cervical  region  of  the  Ox  (Fig.  288). 


INTERNAL   CAROTID   ARTERT.      (FigS.    285,  8;    286,  5.) 

One  of  the  terminal  branches  of  the  common  carotid,  the  internal  carotid 
ascends  at  first  to  beneath  the  base  of  the  cranium,  outside  the  anterior 
rectus  muscles  of  the  head,  and  bends  forward  to  reach  the  lacerated 
foramen.  In  this  primary  portion  of  its  course,  it  is  suspended  in  a  par- 
ticular fold  of  the  guttural  pouch,  margined  by  the  superior  cervical 
ganglion,  accompanied  by  the  cavernous  branch  of  the  symj)athetic  nerve, 
and  crossed  in  various  directions  by  the  nerves  which  form  the  guttural 
})lexus.  On  arriving  at  the  middle  of  the  occipito-spheno-temporal  hiatus, 
it  enters  the  cavernous  sinus,  and  in  the  interior  of  that  cavity,  where  it  is 
bathed  in  venous  blood,  describes  two  successive  and  opposite  curvatures ; 
the  first  looking  forwards,  occupies  the  carotid  fossa  of  the  si)henoid  bono  : 
the  second,  with  its  convexity  posterior,  at  which  the  internal  carotid 
receives  an  anastomosing  branch  from  the  basilar  trunk  :  which  branch  is 
voluminous  and  nearly  constant  in  the  Ass  ;  but  is  rare  and,  when  present, 
very  slender  in  the  Horse.  After  the  last  inflexion,  the  two  internal  carotids 
commimicate  by  a  very  large  transverse  branch,  which  is  always  flexuous, 
often  reticulated,  and  leave  the  cavernous  sinus  in  crossing  the  dura  mater, 
to  gain  the  cranial  cavity. 

These  arteries  are  then  placed  at  the  sides  of  the  pituitary  gland,  within 
the  superior  maxillary  nerve,  proceed  from  behind  forward,  and  terminate 
in  two  branches  before  reaching  the  optic  nerve.     One  of  these  branches 


580 


THE  ARTERIES. 


constitutes  the  posterior  communicating  artery 
form  the  middle  and  anterior  cerebral  arteries. 

Fig.  285. 


the  other  soon  bifurcates  to 


ARTERIES  OF   THE   BRAIN. 

B,  Medulla  oblongata ;  P,  Pons  Varolii ;  L,  Mastoid  lobule ;  0,  Olfactory  lobule ; 
C,  Chiasraa  of  the  optic  nerves;  M,  Mamillary,  or  pisiform  tubercle;  H,  Pituitary 
gland  ;  three-fourths  have  been  excised. — 1,  1,  Cerebro-spinal  arteries  ;  2,  Median 
spinal  artery ;  3,  Lozenge-shaped  anastomosis  of  the  two  cerebro-spinal  arteries, 
from  which  result,  in  front : — 4,  The  basilar  trunk  (usually  the  cerebro-spinal 
arteries  arrive  in  the  middle  of  the  lozenge) ;  5,  5,  Posterior  cerebellar  arteries  ; 
6,  Anterior  ditto ;  7,  Internal  carotid  artery,  with  the  two  curves  it  makes  in 
the  cavernous  sinus  ;  8,  Internal  carotid  on  the  sides  of  the  pituitary  gland ;  9, 
Transverse  reticulated  anastomosis  thrown  between  the  two  internal  carotids 
behind  the  pituitary  gland;  10,  Bifurcation  of  the  internal  carotid;  11,  11, 
Posterior  cerebral  arteries  anastomosing  behind  the  pisiform  tubercle,  i-eceiving 
in  the  middle  of  this  anastomosis  the  two  terminal  branches  of  the  basilar  trunk ; 
12,  Middle  cerebral  artery;  13,  Anterior  cerebral  artery;  14,  Posterior  com- 
municating artery. 


TEE  COMMON  CAROTID  ARTERIES.  581 

Posterior  Communicating  Aeteky. — This  vessel  is  inflected  backward  on 
the  side  of  the  pituitary  gland,  and  anastomoses  behind  it  with  the 
l)osterior  cerebral  artery. 

Middle  Cekebual  Artery. — This  vessel  separates  itself  from  the  an- 
terior cerebral  artery,  external  to  the  chiasma  of  the  optic  nerves,  is  lodged 
in  the  fissure  of  Sylvius,  passing  through  it  in  a  flexuous  manner,  and  at  its 
extremity  separates  into  several  branches  which  ramify  on  the  lateral  and 
superior  faces  of  the  brain,  and  anastomose  by  their  terminal  divisions  with 
the  posterior  and  anterior  cerebral  arteries. 

Anterior  Cerebral  Artery. — This  enters  immediately  above  the  com- 
missure of  the  optic  nerves,  and  proceeds  inwards  to  unite,  in  the  middle 
line,  with  the  opposite  artery,  forming  with  it  a  single  vessel.  This  median 
artery  (or  arteria  corporis  callosi)  enters  the  longitudinal  fissure  of  the  brain 
by  bending  round  the  anterior  extremity  of  the  corpus  callosum,  and,  after 
a  short  course,  divides  into  two  branches  which  pass  from  before  to  behind, 
one  to  the  right,  the  other  to  the  left,  on  the  internal  face  of  the  hemisplieres, 
a  short  distance  livnn  the  corpus  callosum,  and  near  the  posterior  extremity 
of  that  great  commissure.  The  branches  emitted  by  these  arteries,  either  in 
their  track  or  at  their  termination,  anastomose  with  those  of  the  posterior  and 
middle  cerebral  arteries,  as  well  as  with  the  lobular  branch  of  the  oijhthalmic. 

Before  uniting  in  a  common  trunk,  the  two  anterior  cerebral  iirteries 
receive  the  meningeal  branch  of  the  ophthalmic,  the  calibre  of  which  often 
even  surpasses  that  of  these  vessels. 

external  carotid  artery.     (Fig.  286,  12.) 

This  artery  ought  to  be  considered,  because  of  its  volume  and  direction, 
as  the  continuation  of  the  common  carotid.  It  is  directed  forward,  arrives 
at  the  posterior  border  of  the  great  branch  of  the  os  hyoides,  passes  between 
it  and  the  great  hyoid  muscle,  and  is  inflected  so  as  to  form  an  elbow  which 
is  turned  forward,  and  afterwards  ascends  vertically  to  near  the  neck  of  the 
condyle  of  the  inferior  maxilla,  at  the  posterior  angle  of  the  hyoid  branch. 
There  it  bifurcates  to  give  rise  to  the  superficial  temporal  and  internal 
maxillary  arteries. 

In  the  first  part  of  its  course — that  is,  from  its  origin  to  the  hyoid 
bone,  the  extsrnal  carotid  artery  responds  :  inwardly,  to  the  guttural  pouch 
and  the  glosso-pharyngeal  and  superior  laryngeal  nerves  ;  outwardly,  to  the 
outer  belly  of  the  digastric  muscle,  and  the  hypoglossal  nerve. 

In  its  second  portion,  it  is  comjirised  between  the  guttural  pouch,  the 
parotid  gland,  the  great  branch  of  the  os  hyoides,  and  the  inner  side  of 
the  posterior  border  of  the  inferior  maxilla. 

The  collateral  branches  this  artery  furnishes  are  three  principal :  the 
glosso-facial,  maxillo-miiscular,  and  posterior  auricular.  But  it  also  gives  off 
others  of  less  importance,  which  are  distributed  to  the  guttural  pouch,  the 
guttural  glands,  and  the  parotid  gland. 

1.  External  Maxillary,  Facial,  or  Glosso-facial  Artery.     (Fig.  286,  13.) 

It  originates  from  the  external  carotid,  at  the  point  where  that  vessel 
pass(^s  beneath  the  great  hyoid  muscle,  and  is  immediately  inflected  downwards 
on  the  side  of  the  pharynx,  between  the  posterior  border  of  the  large  branch 
of  the  hyoid  bone  and  the  above  muscle.  It  passes  in  proximity  to  the 
anterior  extremity  of  the  maxillary  gland,  crossing  Wharton's  duct  outwardly, 
40 


582  THE  ARTERIES. 

and  leaves  the  deep  situation  it  at  first  occupied,  to  become  more  superficial 
in  the  submaxillary  sj)ace,  where  it  rises  on  the  surface  of  the  internal 
pterygoid  muscle,  and  is  directed  forwards  to  the  maxillary  fissure.  Turning 
round  this  fissure,  it  climbs  on  the  face,  in  front  of  the  masseter  muscle,  to 
above  the  maxillary  spine,  where  it  terminates  in  two  small  branches. 

In  its  long  and  complicated  course,  the  glosso-facial  artery  describes 
a  semicircle  upwards,  and  is  very  naturally  divided,  for  the  study  of 
its  relations,  into  three  portions :  a  deep,  an  intermaxillary,  and  a  facial. 
The  first,  or  deep  portion,  accomijanied  in  its  superior  moiety  by  the  glosso- 
pharyngeal nerve,  responds,  outwardly,  to  the  internal  masseter  (internal 
pterygoid)  muscle ;  inwardly,  to  the  guttural  pouch,  the  hyo-pharyiigeal 
muscle,  hypoglossal  nerve,  middle  tendon  of  the  digastricus,  the  basio- 
glossiis,  canal  of  Wharton,  and  the  subscapulo-hyoideus.  The  inter- 
maxillary, or  middle  portion,  is  bordered  by  the  glosso-facial  vein,  lies 
against  the  pterygoideus  internus,  and  is  in  contact  with  the  submaxillary 
glands.  The  facial,  or  terminal  part,  is  lodged,  at  its  commencement,  in  the 
maxillary  fissure,  in  front  of  the  glosso-facial  vein  and  the  parotid  duct ;  it 
ascends  with  thes3  two  vessels  along  the  anterior  border  of  the  masseter. 
on  the  maxillo-labial  and  buccinator  muscles,  beneath  the  subcutaneous  and 
zygomat' co-labial  muscles  and  the  ramifications  of  the  facial  nerve,  which 
peri^endicularly  crosses  the  direction  of  the  artery. 

Terminal  Branches. — The  external  maxillary  artery  terminates  in  two 
small  branches  which  separate  from  each  other  at  an  obtuse  angle,  one  being 
directed  upwards,  the  other  downwards.  The  ascending  branch  passes 
to  the  surface  of  the  elevator  muscle  of  the  upper  lip,  below  the  lachrymal 
muscle,  and  anastomoses  with  the  divisions  of  a  palpebral  branch  emanating 
from  the  supermaxillo-dental  artery  (Fig.  286,  19").  The  descending 
branch  goes  to  the  false  nostril  and  the  entrance  to*  the  nasal  cavities, 
by  creeping  beneath  the  supernasalis-labialis  muscle  (Fig.  286,  20). 

Collateral  Branches. — These  are  five  principal  branches  :  1,  'The 
pharyngeal ;  2,  lingual ;  3,  sublingual ;  all  of  which  arise  from  the  first 
portion  of  the  glosso-facial  artery ;  4,  The  inferior  and  superior  coronary 
arteries,  emanating  from  the  facial  portion.  Besides  these,  there  are  a  great 
number  of  innominate  branches  of  secondary  importance,  which  proceed 
to  the  neighbouring  parts,  and  principally  to  the  maxillary  gland,  sub- 
maxillary glands,  the  masseter  muscle,  and  the  muscles  and  integuments  of 
the  face.  We  will  content  ourselves  with  merely  noting  the  existence 
of  these  latter  branches. 

1.  Pharyngeal  Artery  (Fig.  286,  14). — This  arises  from  the  glosso- 
facial,  at  a  variable  distance  from  its  origin,  and  sometimes  even  in  the 
angle  formed  by  that  vessel  and  the  external  carotid  artery.  Whatever  may 
be  its  commencement,  it  is  always  directed  forwards,  passes  between  the  hyo- 
pharyngeus  muscle  and  the  great  branch  of  the  hyoid  bone,  and  describing 
some  flexuosities,  goes  towards  the  pterygoid  process,  beneutb  the  elastic 
layer  which  covers  the  pterygo-pharyngeus  muscle  (anterior  constrictor 
of  the  pharynx).  It  terminates  in  the  soft  palate,  after  giving  off  on 
its  course  ascending  and  descending  branches,  which  expend  themselves  in  the 
walls  of  the  pharynx. 

2.  Lingual  Artery  (Fig.  286,  15). — As  considerable  in  volume  as  the 
parent  branch,  this  artery  is  detached  at  an  acute  angle  from  it,  at 
the  extremity  of  the  hyoid  cornu.  With  the  glosso-pharyngeal  nerve,  it 
passes  beneath  the  basio-glossal  muscle,  crossing  the  small  branch  of  the  os 
hyoides,    and   extends  to  the  extremity  of  the  tongue  by  gliding  in   the 


THE  COMMON  CAROTID  ARTERIES. 


583 


Fig.  2S 


ARTERIES   OF   THE   HEAD. 

1,  Common  carotid  artery ;  2,  Accessory  thyroid  artery ,  3,  4,  Thyro-laryngeal 
artery,  divided  into  two  branches ,  5,  Internal  carotid  artery , '  6,  Occipital 
artery;  7,  Atloido-muscular  artery  at  its  exit  from  the  inferior  foramen  of  the 
atlas  ;  8,  Mastoid  artery  ;  9,  Prevertebral  artery  ;  10,  Occipito-muscular  artery  ; 


•584  THE  ARTERIES. 

interstice  between  the  genio-glossus  and  basio-glossus  muscles,  where 
it  meets  the  branches  of  the  lingual  and  hypoglossal  nerves. 

Flexuous  in  its  course,  in  order  to  adapt  itself  to  the  elongation  of  the 
tongue,  the  lingual  artery  emits  a  very  great  nimiber  of  collateral  branches, 
which  escape  perpendicularly  from  the  entire  periphery  of  the  vessel; 
but  chiefly  above,  below,  and  on  the  inner  side,  to  ramify  in  the  muscles 
and  integuments  of  the  tongue. 

Eunning  parallel  to  each  other,  the  two  lingual  communicate  by 
five  transverse  ramuscules,  and  join  at  theu-  terminal  extremity,  which 
becomes  very  slender. 

3.  Sublingual  Artery  (Fig.  286,  16). — This  artery  has  its  origin 
at  the  anterior  extremity  of  the  maxillary  gland,  and  runs  forward  along  the 
external  surface  of  the  mylo-hyoideus  muscle,  which  it  afterwards  crosses 
towards  the  posterior  extremity  of  the  sublingual  gland.  It  then  follows 
the  inferior  border  of  this  gland,  sending  iuto  it  numerous  branches, 
and  after  giving  some  filaments  to  the  geuio-giossus  and  genio-hyoideus 
muscles,  is  prolonged  on  the  sides  of  the  frjenum  liuguse,  where  it  ends  by 
fine  ramuscules  in  the  buccal  mucous  membrane. 

Among  the  branches  this  artery  detaches  before  attaining  the  sublingual 
gland,  it  is  necessary  to  distinguish  those  which  are  destined  to  the  myLi- 
hyoideus  muscle,  some  of  which,  the  descending,  are  thin  and  irregular ; 
and  others,  ascending,  being  long,  thick,  and  parallel  to  each  other. 

Sometimes  this  artery  does  nut  reach  the  sublingual  gland ;  it  then 
remains,  for  the  whole  of  its  extent,  external  to  the  mylo-hyoideus  muscle, 
and  sends  its  terminal  divisions  to  the  vicinity  of  the  symphysis  of  tl  e 
chin.  In  this  case,  the  gland  receives  a  special  branch  from  the  lingual 
artery,  a  circumstance  which  is  usual  in  Man,  in  whom  this  artery  is  named 
the  submental.. 

4.  Coronary  oe  Inferior  Labiat,  (Fig.  286,  17).— Srringing  from  the 
glosso-facial  artery  at  an  acute  angle,  shortly  before  that  vessel  arrives 
at  the  maxillo-labial  muscle,  the  inferior  coronary  artery  passes  under  that 
muscle,  and  following  its  direction,  descends  into  the  texture  of  the  lower 
lip,  where  it  is  mixed  up  witli  the  ramifications  of  the  mental  nerve, 
and  where  it  terminates  by  forming  a  very  fine  anastomotic  arch  with 
the  vessel  of  the  opposite  side. 

In  its  track,  it  gives  branches  to  the  buccinator  and  maxillo-labial 
muscles,  and  to  the  tissues  of  the  lower  lip,  to  which  it  is  chiefly  destined. 
In  its  passage  near  the  mental  foramen,  it  receives  the  inferior  denial  artery 
as  it  leaves  that  opening. 

5.  Coronary  or  Superior  Labial  Artery  (Fig.  286,  18). — Smaller 
than  the  iireceding  vessel,  and  often  altogether  rudimentary,  this  artery 
is  detached  from  the  principal  trunk   at  nearly  a   right  angle,  above  the 

11,  Terminal  extremity  of  the  vertebral  artery  joining  the  atloido-muscular 
branch;  12,  External  carotid  artery;  13,  External  maxillary  artery  ;  14,  Pha- 
ryngeal artery;  15,  Lingual  artery;  16,  Sublingual  artery;  17,  Coronary,  or 
inferior  labial  artery;  18,  Coronary,  or  superior  labial  artery,  19,  Superior 
terminal  branch  of  the  external  maxillary  artery  ;  20,  Inferior  terminal  branch 
of  ditto;  21,  Maxillo-muscular  artery;  22,  23,  Posterior  auricular  artery;  24, 
Superficial  temporal  trunk ;  25,  Subzygomatic  artery ;  26,  Inferior  auricular 
artery ;  27,  Internal  maxillary  artery ;  28,  Inferior  dental  artery ;  29,  Fasciculi 
of  pterygoid  arteries  ;  30,  Tympanic  artery ;  31,  Spheno-spinous  artery  ,  32,  Deep 
posterior  temporal  artery ;  33,  Deep  anterior  temporal  artery  ;  34,  Ophthalmic 
artery;  35,  Supra-orbital  artery;  36,  Lachrymal  artery;  37,  Buccal-artery  ;  38, 
Palatine  artery  ;  39,  Superior  dental  artery  ;  40,  Orbital  branch  of  that  vessel 


THE  COMMON  CAltOTID  ARTERIES  LSj 

origin  of  the  pyramidal  muscle  of  the  nose,  (supermaxillo-nasalis  magnus), 
and  sometimes  below  that  muscle.  It  subsequently  gains  the  upper  lip, 
along  with  the  infra- orbital  branches  of  the  superior  maxillary  nerve, 
by  passing  between  the  supernasalis-labialis  and  the  pyramidal  muscle  of 
the  nose ;  it  then  terminates  in  forming  an  arch  by  inosculation  with  the 
palato-labialis  artery. 

The  branches  it  gives  off  pass  to  the  external  ala  of  the  nose  and  the 
textures  of  the  upper  lip.  Some  are  expended  in  the  muscles  just  named, 
and  in  the  alveolo-labialis. 

2.  Maxillo-muscular  Artery.     (Fig.  286,  21.) 

The  maxillo-muscular  artery  is  a  vessel  that  does  not  appear  to  have  its 
rej)resentativo  in  Man.  It  emerges  from  the  external  carotid,  above  the 
point  whero  it  is  included  between  the  large  branch  of  the  os  hyoides  and 
the  stylo-hyoid  muscle.  Remarkable  for  the  very  obtuse  angle  it  forms  at 
its  origin  with  the  principal  vessel,  it  descends  behind  the  posterior  border 
of  the  inferior  maxilla,  covered  by  the  parotid  gland.  It  then  divides 
into  two  branches  :  a  deep  one,  which  goes  to  the  internal  pterygoid  muscle, 
after  furnishing  some  ramuscules  to  the  neighboiiring  organs ;  and  a 
superficial  one,  which  turns  round  the  posterior  border  of  the  maxilla, 
and  emerging  from  beneath  the  parotid  gland,  above  the  insertion  of 
the  sterno-maxillaris  muscle,  phmges  into  the  masseter,  and  expends  itself 
in  the  body  of  that  muscle  by  several  branches  which  anastomose  with  the 
divisions  of  the  subzygomatic  axiiery. 

3.  Posterior  Auricular  Artery.     (Fig.  286,  22.) 

Third  collateral  branch  of  the  external  carotid,  the  posterior  auricular 
artery  arises  at  a  very  acute  angle  above,  and  a  little  behind,  the  preceding 
vessel.  It  ascends  beneath  the  parotid  gland,  behind  the  base  of  the  concha 
of  the  ear,  crosses  the  cervico-auricular  muscles,  and  reaches  the  extremity 
of  the  cartilage  by  passing  underneath  the  skin  which  covers  its  posterior 
plane. 

In  its  course,  it  emits  several  ascending  auricular  branches,  which  arise 
at  different  elevations  and  cover  the  concha  with  their  divisions.  Among 
these  we  ought  to  distinguish  the  first  (Fig.  286,  23) ;  this  has  its  origin  at 
the  temporal  trunk,  and  soon  divides  into  two  branches  :  one,  profound, 
after  sending  a  very  thin  filament  into  the  middle  ear  by  the  stylo-mastoid 
foramen,  passes  between  the  external  auditory  canal  and  the  mastoid 
process  to  enter  the  subconchal  adipose  tissue  and  the  internal  scuto- 
auricular  muscle ;  the  other,  superficial,  imbedded  in  the  parotid  tissue, 
proceeds  to  the  external  side  of  the  concha,  and  buries  itself  in  the  interior 
of  that  cartilage,  along  with  the  middle  auricular  nerve,  after  abandoning 
some  external  ramuscules. 

From  these  auricular  branches  there  also  escape  a  multitude  of 
parotideal  twigs. 

4.  Superficial  Temporal  Artery  or  Temporal  Trunk.     (Fig.  286,  25.) 

This  is  the  smallest  of  the  two  terminal  branches  of  the  external  carotid. 
After  a  short  ascending  course  between  the  parotid  gland,  the  guttural  pouch, 
and  the  neck  of  the  maxillary  condyle,  behind  which  it  is  situated, 
this  artery  is  divided  into  two  branches  :  the  anterior  auricular  and  the 
subzygomatic. 


586  THE  ARTERIES. 

Anterior  Auricular  Artery  (Fig.  286,  26). — This  vessel  appears  to 
be,  nut  only  by  its  volume,  but  also  by  its  direction,  the  continuation  of  the 
temporal  trunk.  Embraced,  near  its  origin,  by  the  facial  nerve  and  siib- 
zygomatic  branch  of  the  inferior  maxillary  nerve,  it  rises  behind  the 
temporo-maxillary  articulation  and  supercondyloid  process,  beneath  the 
parotid  gland,  to  the  temporal  muscle,  into  which  it  passes  after  emitting 
parotideal  twigs  and  auricular  branches,  one  of  which  penetrates  to  the 
interior  of  the  concha,  while  the  others  are  expended  in  the  anterior 
muscles  of  the  ear  and  the  integuments  covering  these  muscles. 

SuBZYGOMATio  Artery  (Fig.  286,  25.) — More  considerable  than  the 
anterior  auricular,  this  artery  disengages  itself  from  beneath  the  parotid 
gland  by  turning  round  the  posterior  border  of  the  maxilla,  along  with  the 
nervous  anastomosis  which  gives  rise  to  the  subzygomatic  plexus,  and  is  placed 
above  that  anastomosis,  beneath,  and  to  the  outside  of,  the  afore-mentioned 
condyle.  There  it  ends  in  two  branches  of  equal  volume  :  a  superior  or 
superficial,  and  an  inferior  or  deep,  both  of  which  ramify  in  the  substance 
of  the  masseter  muscle,  and  anastomose  with  the  divisions  of  the  maxillo- 
muscular,  or  with  the  masseter  branches  of  the  external  maxillary  arteries. 

The  superior  branch,  or  transverse  artery  of  the  face,  goes  towai'ds  the 
anterior  border  of  the  masseter  muscle  in  a  flexuous  manner,  close  to 
the  zygomatic  ridge.  At  first  lying  on  the  superficies  of  the  masseter, 
it  afterwards  buries  itself  in  that  muscle. 

The  inferior  branch,  or  masseteric  artery,  dips  .  in  among  the  deep 
fasciculi  of  the  masseter  muscle,  to  which  it  is  distributed,  along  with 
the  masseteric  nerve.  Near  its  origin,  it  communicates  with  the  deep 
posterior  temporal  artery  by  a  fine  ramuscule,  which  passes  into  the  sigmoid 
notch.  In  Man  and  some  animals,  this  artery  comes  from  the  internal 
maxillary. 

5.  Internal  maxillary  or  Gutturo-maxillary  Artery.     (Fig.  286,  27.) 

Situated  at  first  immediately  within  the  maxillary  condyle,  below  the 
articulation  of  the  jaw,  this  artery  passes  to  the  inner  side,  towards  the 
entrance  of  the  subsphenoidal  (or  pterygo-palatine)  canal,  by  describing 
two  successive  curvatures :  the  first  backwards,  the  other  forwards.  After 
being  thus  shaped  like  an  S,  it  travels  forward  along  the  subsphenoidal 
canal  to  the  orbital  hiatus,  and  then  reaches  the  maxillary  hiatus  to  enter 
the  palatine  canal,  where  it  is  designated  the  palafo-labial  artery. 

In  order  to  study  its  relations,  the  course  of  this  artery  may  be  divided 
into  three  portions :  a  posterior  or  guttural,  a  middle  or  sphenoidal,  and  an 
anterior  or  infra-orbital.  The  posterior  portion  lies  on  the  internal  face  of 
the  external  pterygoid  muscle,  covered  inwardly  by  the  guttural  pouch,  and 
crossed  outwai-dly  by  the  inferior  maxillary  nerve  and  some  of  its  branches. 
The  middle  division  is  enveloped  by  the  bony  walls  of  the  subsphenoidal 
canal.  The  anterior  portion,  alone  with  the  superior  maxillary  nerve, 
passes  across  the  space  separating  the  orbital  from  the  maxillary  hiatus,  by 
creeping  along  the  palate  bone,  beneath  a  considerable  mass  of  fat. 

Collateral  Branches. — The  arteries  given  off  by  the  internal  maxillary 
on  its  course  are  eleven  principal.  Five  arise  from  the  first  portion  of  the 
vessel :  two  below,  the  inferior  dental  and  the  group  of  pterygoid  arteries ; 
three  above,  the  tympanic,  spheno-spinous,  and  deep  posterior  temporal. 

Two  escape  from  the  superior  portion  of  the  interosseous  or  sphenoidal 
division.    These  are  the  deep  anterior  temporal  and  ophthalmic  arteries.    Four 


THE  COMMON  CAROTID  ARTERIES.  587 

commouce  from  tlie  third  section  of  the  artery  :  two  inferior,  the  buccal  and 
palatine ;  and  two  upper,  the  superior  dental  and  the  nasal. 

1.  Infebior  Dental  Aiitery  (Fig.  286,  28). — This  vessel,  also  named 
the  maxiUo-dental  arterij,  is  detached  at  a  right  angle  from  about  the  middle 
of  the  first  curvature  described  by  the  internal  maxillary.  It  travels 
forward  and  downward  between  the  two  pterygoid  muscles,  afterwards 
between  the  internal  one  and  the  maxillary  bone,  entering  with  the  inferior 
maxillary  nerve  into  the  dental  canal,  through  the  whole  extent  of  which  it 
passes.  Arrived  at  the  mental  foramen,  it  separates  into  two  branches  :  a 
deep  one,  which  continues  the  interosseous  course  of  the  vessel,  to  be 
distributed  to  the  roots  of  the  tusk  or  tush,  and  the  three  adjoining  incisor 
teeth ;  the  other  superficial,  generally  very  slender  and  even  cajjillary, 
issuing  by  the  mental  foramen  with  the  terminal  branches  of  the  maxillary 
nerve,  and  anastomosing  with  the  inferior  coronary  artery. 

Before  penetrating  the  maxilla,  this  artery  furnishes  divisions  to  the 
internal  pterygoid  and  mylo-hyoid  muscles. 

In  the  interior  of  the  maxillo-dental  canal,  it  gives  off  diploic  branches 
as  well  as  twigs,  destined  to  the  roots  of  the  molar  teeth  and  the  alveolar 
membrane. 

2.  Pterygoid  Arteries  (Fig.  286,  29). — It  may  be  said,  in  a 
general  manner,  that  the  two  pterygoid  muscles  borrow  their  arteries  from 
all  the  vessels  passing  near  them,  though  there  are  two,  and  sometimes  three, 
branches  more  especially  intended  for  them.  These  branches,  or,  properly 
speaking,  pterygoid  arteries,  arise  from  the  middle  of  the  second  curvature  of 
the  internal  maxillary,  either  at  an  acute  or  right  angle,  and  enter  the 
pterygoid  muscles,  after  a  short  course  forward  and  downward  on  the 
external  tensor  palati  muscle ;  this  and  its  fellow,  the  internal  muscle,  also 
receiving  some  branches. 

3.  Tympanic  Artery  (Fig.  286,  30). — A  very  thin  and  small,  but  constant 
artery,  gliding  along  the  surface  of  the  guttural  pouch,  accompanying 
the  tympano-lingual  nerve,  and  penetrating  the  tympanic  cavity  by  a  foramen 
situated  at  the  base  of  the  styloid  j)rocess  of  the  temporal  bone  {ihefissura 
Glaseri).  It  throws  off  ramuscules  to  the  wall  of  the  guttural  pouch 
and  the  trigeminal  nerve  ;  these  often  arise  directly  from  the  trunk  of  the 
internal  maxillary  artery,  besides  the  tympanic  branch. 

4.  Spheno-spinous  or  Great  Meningeal  Artery  (Fig.  286,  31). — 
Commencing  at  an  obtuse  angle,  opposite  the  pterygoideal  vessels,  this 
artery  lies  against  the  sphenoid  bone,  near  the  temporal  insertion  of 
the  tensor  palati  muscles,  is  directed  backwards  and  upwards,  enfers  the 
cranium  by  the  anterior  lacerated  foramen,  outside  the  inferior  maxillary 
nerve,  passes  beneath  the  dura  mater,  and  soon  after  engages  itself  in 
a  particular  foramen  in  the  parieto-temporal  canal,  where  it  anastomoses  by 
inosculation  with  the  mastoid  artery. 

Before  penetrating  this  canal,  the  spheno-spinous  artery  gives  off 
a  meningeal  branch,  whose  ramifications,  destined  to  the  dura  mater,  stand 
in  relief  on  that  membrane,  and  creep  along  in  the  small  grooves  channeled 
on  the  inner  surface  of  the  cranium. 

The  volume  of  this  vessel  is  subject  to  the  greatest  variations,  and 
is  always  in  an  inverse  proportion  to  that  of  the  mastoid  artery. 

5.  Deep  Posterior  Temporal  Artery  (Fig.  286,  32). — This  arises  at 
a  right  angle,  immediately  before  the  entrance  of  the  internal  maxillary 
artery  into  the  subsphenoidal  canal.  Then  it  ascends  on  the  temporal  bone, 
in  the  temporal  muscle,  passing  in  front  of  the  tempore  maxillary  articula- 


588  TEE  ARTERIES. 

tion,  which  it  turns  round  to  be  inflected  backwards.  This  vessel  com- 
municates with  the  masseteric  artery  by  a  fine  division,  which  traverses  the 
sigmoid  notch  of  the  maxillary  bone. 

6.  Deep  Anterior  Temporal  Artery  (Fig.  286,  33). — Springing  at  a 
right  angle,  like  the  preceding,  in  the  interior  of  the  subsphenoidal  canal, 
this  artery  escapes  by  the  superior  branch  of  that  conduit,  ascends  against 
the  bony  wall  of  the  temporal  fossa,  along  the  anterior  border  of  the  temporal 
muscle,  in  which  it  is  almost  entirely  expended.  It  gives  some  ramuscules 
to  the  adipose  tissue  of  the  temporal  fossa.  Its  terminal  extremity  arrives 
beneath  the  internal  parieto-auricular  muscle,  ramifies  in  it,  and  in  the  skin 
of  the  forehead. 

7.  Ophthalmic  Artery  (Fig.  286,  34). — This  vessel  has  a  somewhat 
singular  arrangement.  After  being  detached  from  the  internal  maxillary  in 
the  subsphenoidal  canal,  in  front  of  the  deep  anterior  temporal  artery,  with 
which  it  is  sometimes  united,  it  penetrates  by  the  orbital  hiatus  to 
the  bottom  of  the  ocular  sheath ;  it  then  enters  the  cranium  by  the  orbital 
foramen,  after  describing  a  loop  opening  backwards  and  downwards,  which 
l^asses  between  the  muscles  of  the  eye,  beneath  the  superior  rectus,  and 
above  the  optic  nerve  and  the  sheath  formed  round  it  by  the  posterior  rectus 
(or  retractor). 

Entering  the  cranium,  the  ophthalmic  artery  passes  inwards  along  a 
groove  in  the  ethmoidal  fossa,  and  terminates  by  two  branches  :  a  meningeal 
and  nasal. 

Collateral  branches.  — In  its  orbital  track,  the  ophthalmic  artery 
emits  numerous  collateral  branches,  which  arise  from  the  convex  side  of  the 
loop  described  by  this  vessel.  These  are :  the  muscular  arteries  of  the 
eye,  the  ciliary,  central  artery  of  the  retina,  supra-orbital,  and  lachrymal 
arteries. 

In  its  cranial  portion,  it  furnishes  the  cerebral  branches. 

The  muscular  arteries  of  the  eye  have  a  destination  sufficiently  indicated 

by    their   name.     Their  number  and   mode    of  origin    vary.       They   are 

usually  two  principal,  which  arise  directly  from  the  ojihthalmic  artery,  and 

others   of    a    smaller  size   furnished   by  the  lachrymal  and  supra-orbital 

.  branches. 

The  ciliary  arteries,  destined  to  the  constituent  parts  of  the  globe  of  the 
eye,  but  chiefly  to  the  choroid  coat,  the  ciliary  processes,  and  the  iris, 
are  long  thin  branches,  emanating,  for  the  most  part,  from  the  muscular 
arteries. 

We  only  mention  the  centralis  retinse  artery  here ;  as  it  and  the  ciliary 
arteries  will  be  described  when  we  come  to  study  the  visual  apparatus. 

The  supra-orbital  artery  ascends,  with  the  nerve  of  the  same  name,  against 
the  inner  wall  of  the  ocular  sheath,  to  gain  the  supra-orbital  foramen  ; 
passing  through  that  orifice,  it  is  distributed  to  the  frontal  and  supra-orbital 
muscles,  the  orbicularis  of  the  eyelids,  external  temporo-auricularis  muscle, 
as  well  as  to  the  integument  of  the  frontal  region  ( Fig.  286,  85). 

The  lachrymal  artery  creeps  upwards  and  forwards,  between  the  muscles 
of  the  globe  of  the  eye  and  the  superior  wall  of  the  ocular  sheath,  to  terminate 
in  the  lachrymal  gland  and  the  upper  eyelid  (Fig.  286,  36.) 

The  cerehral  branches  of  the  ophthalmic  artery  vary  in  number,  and 
frequently  there  is  only  one,  of  somewhat  considerable  volume.  They  pass 
to  the  anterior  exti'emity  of  the  cerebral  lobe,  and  anastomose  with  the 
divisions  of  the  anterior  cerebral  artery. 

Terminal  branches. — The  meningeal  branch,  after  detaching  ramuscules 


THE  COMMON  CAROTID  ARTERIES.  589 

to  the  dura  mater,  and  particularly  to  the  falx  cerebri,  anastomoses  on  the 
median  line,  below  the  process  of  the  crista  galli,  with  that  of  the 
opposite  side,  and  afterwards  joins  the  anterior  cerebral  artery. 

The  nasal  branch  traverses  the  cribriform  plate  of  the  ethmoid  bone,  and 
divides  into  a  number  of  ramuscules,  which  descend  either  on  the  ethmoidal 
cells,  or  on  the  middle  septum  of  the  nose,  where  their  ramifications  form 
arterial  tiifts  of  a  pleasing  aspect. 

8.  Buccal  Artery  (Fig.  286,  37). — The  buccal  artery  emerges  at  an  acute 
angle  from  the  internal  maxillary,  a  short  distance  in  front  of  the  orbital 
hiatus,  and  descends  obliquely  between  the  maxillary  bone  and  the  superior 
insertion  of  the  internal  pterygoid  muscle,  terminating  in  the  postei'ior 
part  of  the  molar  glands,  and  in  the  alveo-labial  and  maxillo-labial  muscles. 

In  its  coiu'se  it  gives  some  insignificant  ramuscules  to  the  pterygoid 
muscles,  as  well  as  the  masseter,  and  a  long  adipose  branch  to  the  cushion 
in  the  temporal  fossa.  The  latter  sometimes  comes  directly  from  the 
internal  maxillary  artery. 

9.  Staphylin  Artery  (Fig.  286,  38). — A  very  thin  filament,  which 
accompanies  the  posterior  palatine  nerve  in  the  groove  of  the  same  name, 
and  is  distributed  to  the  soft  palate. 

10.  Superior  Dental  Artery  (Fig.  286,  39). — This  vessel,  which  is 
also  named  the  supermaxiUo-dental  artery,  enters  the  superior  dental  canal, 
arrives  near  its  inferior  or  infra-orbital  opening,  and  then  divides  into  two 
thin  branches.  One  of  these  continues  in  the  same  course  in  the  super- 
maxillary  bone,  to  supply  arterial  blood  to  the  alveoli  of  tlie  foremost 
molars,  the  tusk,  and  the  incisor  teeth  ;  the  other  passes  out  of  the  canal 
with  the  terminal  divisions  of  the  superior  maxillary  nerve,  and  com- 
municates on  the  forehead  with  a  ramuscule  from  the  external  maxillary 
artery. 

On  its  way,  the  superior  dental  artery  emits  several  collateral  branches, 
the  majority  of  which  commence  in  the  interior  of  the  dental  canal,  and 
pass  either  to  the  alveoli  of  the  posterior  molars,  the  tissue  of  the  bone,  or 
the  membrane  lining  the  sinuses.  One  of  these  branches — the  orbital,  and 
the  largest — escapes  from  the  jirincipal  artery  before  its  entrance  into  the 
supermaxillary  canal,  creeps  along  the  floor  of  the  orbit  towards  the  nasal 
angle  of  the  eye,  whence  it  descends  on  the  forehead,  after  giving  ofi" 
some  divisions  to  the  caruncle  of  the  eye,  the  lachi*ymal  sac,  and  the  lower 
eyelid. 

11.  Nasal  or  Spheno-palatine  Artery. — Situated,  at  first,  at  the 
bottom  of  the  maxillary  hiatus,  this  artery,  springing  at  a  right  angle  from  the 
parent  trimk,  traverses  the  nasal  foramen,  and  separates  into  two  terminal 
branches — an  external  and  an  internal — in  ramifying  on  the  walls  of  the 
nasal  cavity. 

Terminal  Branch  of  the  Internal  Maxillary  Artery.  Palato- 
Labial  or  Palatine  Artery.  (Fig.  148,  3.)— A  continuation  of  the 
internal  maxillary,  this  vessel  at  first  traverses  the  palatine  canal,  follows 
the  palatine  groove  to  near  the  superior  incisors,  is  then  inflected  inwards 
above  a  small  cartilaginous  process  (Fig.  148,  4),  and  unites  on  the  median 
line  with  the  artery  of  the  opj^osite  side,  forming  an  arch  whose  convexity 
is  forwards,  and  from  which  proceeds  a  single  trunk  that  passes  into  the 
incisive  foramen. 

The  palatine  arteries,  in  their  advance,  furnish  a  series  of  branches 
destined  to  the  anterior  part  of  the  soft  palate,  the  membranes  on  the  roof  of 
the  mouth,  and  the  gums  and  upper  teeth. 


590  THE  ARTERIES. 

The  single  trunk  whicli  results  from  their  anastomoses  is  placed,  im- 
mediately after  its  exit  from  the  incisive  foramen,  directly  beneath  the 
buccal  mucous  membrane,  and  at  once  divides  into  two  principal  branches 
— a  right  aud  left ;  these  are  lodged  in  the  tissue  of  the  uj)per  lip,  and  pass 
back  to  meet  the  coronary  arteries,  with  which  they  anastomose  by  inoscula- 
tion, after  throwing  oif  on  their  track  a  great  number  of  branches  destined 
to  the  muscles  and  integuments  of  the  lip  and  nostrils. 

DIFFERENTIAL  CHAKACTERS  IN  THE  CAROTID  ARTERIES  OF  OTHER  THAN  SOLIPED  ANI5IALS. 

1.  Tlie  Carotid  Arteries  in  Carnivora. 

In  the  Dog,  the  carotids  arise  singly  from  the  brachio-cephalic  trunk,  and  ascend 
beneath  the  transverse  process  of  the  atlas,  along  the  trachea,  following  a  course 
exactly  like  that  pursued  by  these  vessels  in  the  Horse. 

Among  the  collateral  branches  furnished  by  them,  may  be  distinguished  the  thyro- 
laryngeal  artery,  remark; ible  for  its  enormous  calibre,  its  descending  in  front  of  the 
lateral  lobe  of  the  thyroid  gland,  and  its  termination  in  the  median  isthmus  of  that 
gland. 

The  terminal  branches  of  the  carotid  are,  as  in  Solipeds:  1,  The  occipital;  2,  The 
internal  carotid ;  3,  The  external  carotid,  the  continuation  of  the  primitive  vessel. 

Occipital  Artery. — Inconsiderable  in  volume,  this  vessel  arises  in  front  of  the 
anterior  border  of  the  transverse  process  of  the  atlas,  passes  into  the  notch  on  its 
border,  and  divides  into  two  branches — the  occipito-muscular  and  the  cerebrospinal 
arteries. 

In  its  course,  it  gives  off  branches  analogous  to  those  which  emanate  from  the  pre- 
vertebral artery  of  the  Horse.  It  also  gives  a  mastidd  artery,  which  only  sends  one  very 
small  branch  into  the  parieto- temporal  canal,  and  is  destined  almost  exclusively  to  the 
deep  muscles  of  the  neck.  In  addition,  the  occipital  throws  off  a  retrograde  artery,  which 
directly  joins  the  vertebral. 

The  arrangement  of  the  occipital  artery  in  Carnivora  is,  therefore,  almost  identical 
with  what  has  been  described  in  Solipeds. 

Internal  Card  fid  Artery. — This  vessel  reaches  the  posterior  opening  of  the  carotid 
canal,  along  which  it  passes  forward,  then  describes  a  very  curious  flexure  which  leaves 
the  cranium  by  the  carotid  foramen  (see  page  62),  then  re-enters  that  cavity  after 
r.ceiving  a  particular  branch  from  the  external  carotid.  It  afterwards  anast  imoses  on 
the  side  of  the  pituitary  fossa,  with  the  divisions  of  the  spheno-spinous  artery  and  the 
returning  branch.'S  of  the  ophthalmic  artery,  forming  a  kind  of  plexus,  which  appears  to 
be  a  trace  of  the  re'seau  admirable  of  Ruminants  and  Pachyderms,  and  from  which 
proceed  the  cerebral  arteries. 

External  Carotid  Artery. — This  arterial  branch  terminates,  as  in  Solipeds,  by 
the  superficial  temporal  and  the  internal  maxillary  arteries. 

It  gives  otf  on  its  course:  1.  An  artery  representing  the  meningeal  branch  of  the 
prevertebral  of  the  Horse,  and  which  ascends  in  a  flexuous  manner  on  the  side  of  the 
pharynx  to  join  the  carotid  flexure. 

2.  A  laryngeal  artery,  entering  the  larynx  with  the  superior  nerve  of  that  organ, 
after  giving  ramuscules  to  the  maxillary  gland. 

3.  The  lingual  artery,  a  very  large  tortuous  branch,  whose  course  resembles  that  of  the 
same  vessel  in  the  H^rse. 

4.  A  facial  or  external  maxillary  artery,  divided  into  two  branches  above  the  inferior 
insertion  of  the  digastricus.  One  of  these  branches,  analogous  perhaps  to  the  submental 
of  Man,  passes  within  this  insertion,  and  is  prolonged  to  the  chin,  after  furnishing 
ramuscules  to  the  parts  lodged  in  the  intermaxillary  space.  The  other  branch  winds 
round  the  inferior  border  of  the  maxilla,  in  front  of  the  masseter  muscle,  and  is  expended 
on  the  face  by  ascending  and  descending  branches,  among  which  we  can  readily  perceive 
the  two  coronary  arteries,  and  the  two  twigs  which  we  have  noticed  in  Solipeds  as 
terminal  branches  of  the  vessel. 

5.  The  posterior  auricular  artery,  after  detaching  parotideal  and  musculo-cutaneous 
vessels,  is  situated  on  the  middle  of  the  external  face  of  the  concha,  and  is  directed 
towards  the  terminal  extremity  of  the  cartilage,  where  it  separates  into  two  branches, 
which  are  inflected  en  arcade,  and  return,  in  following  the  borders  of  the  concha,  towards 
the  base  of  the  latter,  where  they  anastomose  with  other  branches,  either  from  the  pos- 
terior or  anterior  auricular,  and  which  come  to  meet  them. 


TEE  COMMON  CAROTID  ARTERIES.  591 

Superficial  temporal  artery. — After  a  brief  course  behind  the  temporo-maxillary  articula- 
tiou,  this  vessel  bifurcates :  its  posterior  or  auricular  branch  anastomosing  with  a  division 
of  tlie  posterior  auricular,  but  not  before  it  has  sent  ramuscules  to  the  interior  of  the 
concha,  and  furnished  some  musculo-cutaneous  twigs.  The  other,  the  anterior  or  temporal 
branch,  glides  benc;ith  tlie  aponeurosis  of  the  temporal  muscle,  above  the  upper  margin 
of  the  zygomatic  arch,  and  wimis  upwards  and  inwards  around  the  outline  of  the  orbit, 
to  terminate  on  the  face  by  anastomosing  ramuscules,  either  with  the  infra-orbital  branch 
of  the  superior  dental  artery,  or  with  the  facial.  In  its  subaponeurotic  course,  it  gives 
divisions  to  the  temporal  muscle.  Above  the  orbital  arch,  it  emits  several  superficial 
ascending  and  internal  twigs,  one  of  the  principal  of  which  communicates  by  ramuscules 
with  the  posterior  auricular  artery,  the  auricular  branch  of  the  superficial  temporal,  and 
with  the  homologous  ramuscules  from  the  opposite  side. 

Internal  maxillary  artery. — The  course  pursued  by  this  vessel  is  similar  to  tliat  it 
follows  in  the  Horse.  After  describing  an  S  curvature  between  the  condyle  of  the 
maxilLiry  bone  and  external  pterygoid  muscle,  it  traverses  the  subsphenoidal  canal, 
and  passes  outside  the  internal  pterygoid  towards  the  maxillary  hiatus,  where  it  is  con- 
tinued by  the  superior  dental  artery. 

a.  The  following  are  the  principal  collateral  branches  emitted  by  this  vessel : 

1.  The  inferior  dental  artery. 

2.  The  deep  posterior  temporal  artery,  which  furnishes  a  masseteric  branch  that 
traverses  the  sigmoid  notch  of  the  maxillary  bone  to  enter  the  masseter  muscle. 

3.  A  fine  tympanic  twig. 

4.  The  spheno-spinous  artery,  almost  entirely  destined  to  the  formation  of  the  plexus 
of  the  cerebral  arteries. 

o.  Several  pteryyoid  arteries. 

6.  The  ophthalmic  artery,  which,  before  entering  the  ethmoidal  fossa  by  the  orbital 
foramen,  gives,  independently  of  the  branches  noted  in  Solipeds — except  the  supra-orhital, 
which  is  absent— a  fasciculus  of  particular  branches.  These  penetrate  the  cranium  by  the 
great  sphenoidal  fissure,  accompanying  the  motor  and  sensory  nerves  of  the  eye,  to  join 
the  internal  carotid  and  spheno-spinous  arteries. 

7.  The  deep  anterior  temporal  artery. 

5.  A  staphylin  artery,  more  voluminous  than  that  in  the  Horse. 

9.  The  palatine  artery. 

10.  A  buccal  and  an  alveolar  artery,  whose  principal  divisions  enter  Duvernoy's  gland. 

b.  The  superior  dental  artery,  which  terminates  the  internal  maxillary,  and  furnishes 
an  orbital  and  an  infra-orbital  branch,  as  in  Solipeds.  The  latter,  remarkable  fi'r  its 
volume,  emerges  from  the  supermaxillary  canal  with  the  infra-orbital  nerves,  to  join  the 
divisions  of  the  external  maxillary  artery  on  the  face,  and  in  the  tissue  of  the  upper  lip. 

2.  Carotid  Arteries  in  the  Pig. 

There  is  nothing  particular  to  notice  regarding  the  course  of  these  vessels,  which  we 
know  arise  separately  from  the  brachio-cephalic  trunk. 

Occipital  artery. — In  its  distribution,  it  greatly  resembles  the  same  vessel  in  the  Horse 
and  Dog.  Its  most  important  branches  are  the  following :  1,  A  very  small  retrograde  artery, 
anastomosing  with  the  vertebral ;  2,  A  branph  which  mounts  into  the  muscles  of  the 
neck,  representing  the  mastoid  artery;  3,  Several  occipitiil  twigs,  which  pass,  with  the 
principal  artery,  by  the  anterior  foramen  of  the  atlas.  This  artery  is  expended  in  a 
complete  manner  in  the  muscles  of  the  neck,  and  without  sending  a  cerebro -spinal  branch 
to  the  interior  of  the  spinal  canal. 

Internal  carotid  artery. — After  furnishing  a  large  meningeal  artery,  this  vessel  enters 
the  cranium  by  the  posterior  lacerated  foramen,  and  there  divides  to  form  a  re'seau 
admirable,  analogous  to  that  of  Eunanants,  and  of  which  a  description  will  be  given 
hereafter.  The  cerebral  arteries  arising  from  this  re'seau  differ  but  little  from  those  of 
Solipeds  ;  these  are  the  posterior  cerebral  arteries,  which  give  rise  to  the  basilar  trunk, 
and  originate  the  median  spinal  arterj'. 

External  carotid  artery. — This  artery  is  seen  to  pass  between  the  pterygoid  muscles 
and  the  branch  of  the  maxillary,  in  describing  several  inflexions,  and  arrives  in  the 
maxillary  hiatus,  without  exhibiting  in  its  course  any  sensible  distinction  between  the 
external  carotid,  properly  called,  and  its  continuation,  the  internal  maxillary  artery. 

Among  the  branches  it  supplies,  we  notice  : 

1.  The  lingual  artery,  more  voluminous,  perhaps,  than  in  the  other  animals. 

2.  A  branch  analogou*,  in  its  origin  at  least,  to  the  glosso-facial  artery  of  the  Horse, 
and  which  distributes  its  ramuscules  in  the  intermaxillary  space,  and  particularly  to  the 
salivary  and  lymphatic  gland 


592  THE  ARTERIES. 

3.  The  'posterior  auricular  artery,  noticeable  for  its  great  length  and  considerable 
volume. 

4.  The  transverse  artery  of  the  face  and  the  anterior  auricular  artery,  arising  separately 
beside  eaoh  other,  and  extremely  slender. 

5.  Several  cZeejj  temporal  and  masseteric  arteries. 

6.  Pterygoid  branches. 

7.  An  en.  .rmous  buccal  branch. 

8.  The  ophthalmic  artery,  concurring  to  form  the  re'seau  achnirahle. 

9.  A  small  orbital  branch,  coming  from  the  superior  deutal  artery  in  Solipeds  and 
Carnivora. 

10.  The  nasal,  palatine,  and  superior  dental  arteries. 

3.  Carotid  Arteries  of  Ruminants. 

A.  In  the  Sheep,  which  will  serve  as  a  type  for  this  description,  the  carotid  arteries 
arise  by  a  common  trunk  from  the  right  axillary  artery,  as  in  ISolipeds.  Arriving  in  the 
cephalic  region,  towards  the  upper  part  of  the  neck,  they  furnish  a  thyroid  and  a 
laryngeal  branch,  then  give  oif  a  very  slender  occipital  artery,  and  are  continued  from  this 
point  by  the  external  carotid. 

The  internal  carotid,  properly  called,  is  absent,  and  we  will  see  immediately  how  it  is 
compensated  for. 

Occipital  aitery. — Having  given  some  ramuscules  to  the  anterior  recti  muscles  of  the 
head,  and  a  small  meningeal  branch  which  enters  the  cranium  by  the  posterior  lacerated 
foramen,  this  vessel  passes  into  the  condyloid  foramen,  which  also  affords  a  passage  to 
the  hypoglossal  nerve,  places  itself  beneath  the  dura  mater,  and  is  inflected  backward  to 
open  into  the  anterior  extremity  of  the  collateral  artery  of  the  spine,  at  the  superior 
foramen  of  the  atlas.  The  branch  resulting  from  this  junction  emerges  by  that  foramen, 
to  be  distributed  in  the  muscles  of  the  neck,  where  its  divisions  resemble  those  of  the 
occipito-muscular  and  atloido-muscular  branches  in  the  Horse. 

In  traversing  the  condyloid  foramen,  the  occipital  artery  sends  into  the  parieto- 
temporal canal,  by  a  peciiliar  bony  conduit  (see  page  56),  a  very  small  filament  which 
is  distributed  to  the  dura  mater,  in  anastomosing  with  a  branch  of  the  posterior  auricular. 

It  communicatis,  after  its  entrance  into  the  cranial  cavity,  with  the  re'seau  admirable. 

External  carotid  artery. — Ternjinated,  as  in  the  Horse,  by  the  superficicd  temporal  and 
internal  maxillary  arteries,  this  vessel  sends  off  on  its  course  : 

1.  A  pharyngeal  artery,  whose  origin  is  nearly  confounded  with  that  of  the  occipital 
artery. 

2.  The  lingucd  artery,  ftirnishing  a  collateral  branch  which  exactly  represents  the 
submental  of  Man,  and  is  divided  into  two  branches,  which  resemble  the  sublingual  and 
ranine  arteries. 

3.  A  large  division  for  the  maxillary  gland. 

4.  The  posterior  auricular  artery,  from  which  proceeds:  1,  The  stylo-inastoid  tmg, 
which  penetrates  the  aqueduct  of  Fallopius ;  2,  Concho-muscular  branches ;  3,  A  large 
branch,  resembling  the  mastoid  artery  of  the  Horse.  This  enters  the  temporo-j^arietal 
canal  by  a  small  foramen  between  the  occipital  and  petrous  portion  of  the  temporal 
bone,  and  forms  two  branches :  an  external,  emerging  from  this  canal  by  the  wide 
orifice  in  the  temporal  fossa,  and  expending  itself  in  the  temporal  muscle,  a<'ter  anas- 
tomosing with  the  two  deep  temporal  arteries  ;  and  an  internal,  a  considerable 
meningeal  artery,  destined  principally  to  the  falx  cerebri  and  the  tentorium  cerebelli. 

5.  A  small  maxJllo-muscular  artery,  ramifying  entirely  in  the  internal  pterygoid  and 
the  subcutaneous  muscles. 

Superficial  temporal  artery. — This  vessel  divides,  almost  at  its  origin,  into  three 
branches : 

1.  A  posterior,  supplying  the  anterior  arteries  of  the  car. 

2.  An  anterior,  forming  the  transversal  faciei,  antl  terminating  by  the  coronary  or 
lcd)ial  arteries,  after  giving  some  ramuscules  to  the  masseter  and  the  muscles  of  the 
forehead. 

3.  A  median  artery,  representing  the  middle  temporal  of  Man.  This  vessel  detaches 
some  divisions  to  the  temporal  muscle,  gives  off  the  lachrymal  artery,  as  well  as  a 
palpebral  branch  rising  from  the  tame  point,  and  terminates  near  the  base  of  the  cranium 
by  two  particular  arteries  which  a:e  developed  around  the  base  of  the  horn,  and  form  a 
real  arterial  circle  from  which  inferior  and  superior  divisions  are  given  off.  'ihe  latter 
are  the  mo^t  considerable,  and  glide  on  the  bony,  core  of  the  frontal  appendage,  where 
they  are  distributed  almost  exclusively  to  the  generating  membrane  of  the  horny  tissue, 
only  throwing  son^e  filaments  into  the  sinuses. 


THE  COMMOy  CAROTID  ARTERIES 


593 


Internal  maxillary  artery. — It  Joes  not  traverse  the  subsphenoidal  canal,  as  that 
bony  passa'je  does  not  exist. 

The  following  are  its  principal  branches : 

1.  The  inferior  deiital  artery  whicli  cuiits  some  ptcrygnil  ramnscules. 

2.  The  .<pheno-gpiiiou^  artery,  aiising  from  the  same  jxiint  as  the  preccdinsr,  often  in 
comm  )n  with  it.  giving  also  some  pteryjoid  branches,  and  entering  tiie  cranium  by  the 
oval  foramen  to  aid  in  the  formation  of  the  re'seau  admirable,  in  a  way  to  be  indicated 
hereafter. 

3.  Ihe  deep  posterior  temporal  artery,  which  detaches  a  masseteric  artery. 

4.  The  deep  anterior  temporal  artery. 

5.  The  bw:cal,  principally  destined  to  the  raasseter  muscle. 

6.  The  ophthalniic  artery,  longer  than  in  the  other  animals,  forming  a  loop  before 
traversing  the  orbital  foramen,  and  g.ving  a  supra-orhihd  branch  and  a  fasciculus  of 
muscular  and  ciliary  arteries.     Near   the  point  where  the  originating  trunk  of  this 

Fig.  287. 


THE   RESEAU    ADMIRABLE   OF  THE   SHEEP,   SEEN   DT   PROFILE. 

1,  Carotid  artery;  "2,  Occipital  artery;  3,  Lingual  artery:  4,  Maxillo-mnscular 
artery  :  5,  Posterior  auricular  artery  :  6,  Superilcial  temporal  artery  ;  7,  Anterior 
auricular  artery ;  8,  Middle  temporal  artery ;  9,  Transverse  artery  of  the  face ; 
10,  iDternal  maxillary  artery;  11,  Inferior  dental  artery;  12,  Spheno-spinous 
artery.  13,  Deep  posterior  temporal  artery:  14,  Deep  anterior  temporal  artery; 
15,  Commencement  of  the  originating  arteries  of  the  reseau  admirable ;  16,  Ence- 
phalic reseau  admirable;  17.  Trunk  of  the  encephalic  arteries  arising  from  the 
reseau  admirahle ;  18,  Ophthalmic  artery;  19,  Ophthalmic  reseau  admirable;  20, 
Common  origin  of  the  arteries  of  the  eye ;  21,  Supra-orbital  artery ;  22,  Buccal 
artery ;  23,  Superior  dental  artery ;  24,  Orbital  branch  of  the  latter ;  25, 
Palatine  artery  ;  26,  Nasal  artery 


fasciculus  is  detached,  the  ophthalmic  artery  shows  on  its  course  a  very  curious  arrange- 
ment which  has  not  yet  been  noticed,  we  believe  :  this  is  a  veritable  arterial  plexus  in  a 
ganglionic  form,  in  principle  exactly  disposed  as  that  about  to  be  described  (Fig.  2S7, 19). 

7.  The  originating  arteries  of  the  re'seau  admirable,  usually  consisting  of  two  firincipal 
vessels,  arising  with  the  ophlhalmic.  passing  backward  through  the  suprasphenoidal 
canal,  and  ramifying  in  a  special  manner  to  form  a  mass  of  reticular  twigs,  designated 
the  re'seau  admirable  (Fig.  287,  16). 

This  network  is  a  small  ovoid  mass,  elongated  from  before  to  behind,  placed  beneath 
the  dura  mater,  on  the  side  of  the  sella  turcica,  within  the  superior  maxillarj-  nerve,  and 
composed  of  a  multitude  of  fine  arterial  divisions  which  anastomose  with  each  other 


594 


THE  ARTERIES. 


Fig.  288. 


in  an  extremely  complicated  manner.  Its  inferior  extremity,  passing  into  the  supra- 
sphenoidal  canal,  receives  the  generating  arteries.  The  posterior  extremity,  covered  by  the 
cliniiid  process,  is  in  communication  with  the  spheno-spinous  artery,  which  there  expends 
itself.  Towards  its  middle  part,  and  above,  the  twigs  forming  it  reconstitute  them- 
selves into  a  single  trunk  analogous  to  the  intercranial  portion  of  the  internal  carotid  of 
Solipeds  (Fig.  287,  17),  and  which  traverses  the  dura  mater,  dividing  into  three  branches. 
These  are  the  anterior,  middle,  and  posterior  cerebral  arteries ;  the  latter  anastomoses,  by 
convergence,  with  the  homologous  artery  of  the  opposite  side,  behind  the  pituitary 
gland,  to  form  the  basilar  trunk  and  the  median  spinal  artery,  which  continues  it. 

This  singular  disposition  of  the  arteries  of  the  encephalon  well  deserves  the  name  of 
re'seau  admirable  (admirable  network),  by  which  it  is  known.  If  we  were  desirous  of 
giving  a  summary  idea  of  this  network,  we  might  compare  it  to  a  lymphatic  gland,  whose 
efferent  vessels  would  be  represented  by  the  originating  arteries  with  the  spheno-spinous, 
and  the  etterents  by  the  originating  trunk  of  the  encephalic  arteries. 

8.  Next  comes  the  siqxrior  dental,  whose  orbital  branch  presents  a  considerable 
volume,  and  terminates  on  the  anterior  surface  of  the  head  by  long  superficial  divisions. 
Some  of  these,  the  ascending,  anastomose  with  the  inferior  branches  of  the  arterial 
circle  situated  around  the  base  of  the  horn ;  while  others,  the  descending,  communicate 
with  the  infra-orbital  branch  of  the  same  vessel,  and  witli  the  superior  coronary 
artery. 

9.  The  last  to  be  given  off  are  the  nasal  and  palatine  arteries,  which  terminate  the 

internal  maxillary  :  the  nasal  artery  is  disposed 
as  in  the  Horse ;  the  palatine  goes  entirely  to  the 
palate. 

B.  In  the  Ox,  we  find  all  the  peculiarities 
just  enumerated,  save  with  the  following  differ- 
ences : 

1.  A  little  above  the  origin  of  the  lingual 
artery,  the  external  carotid  gives  rise  to  an 
external  maxillary  artery,  which  turns  round 
the  inferior  border  of  the  maxillary  bone,  in 
company  with  its  satellite  vein,  and  terminates 
on  the  forehead,  as  in  the  Horse,  after  supply- 
ing the  coronary  arteries. 

2.  'Ihe  maxillo-muscular  artery  is  distributed 
to  the  two  masseters — to  the  external  as  well  as 
the  internal. 

3.  The  transverse  artery  of  the  face  does  not 
foim  the  coronary  arteries,  as  these  come  from 
the  external  maxillary;  it  is  altogether  ex- 
pended in  the  masseter  muscle. 

4.  Tlie  anterior  auricular  artery  sends  an 
enormous  branch  into  the  temporo-parietal  canal, 
by  the  orjlice  situated  behind  the  supercoudyloid 
process. 

5.  The  ophthalmic  artery  and  the  generating 
arteries  of  the  re'seau  admirable  proceed  from  a 
common  trunk. 

6.  The  re'seau  itself  shows  some  differences. 
We  do  not  find,  as  in  the  Slice]),  two  lateral 
elongated  lobes,  almost  independent  of  each 
other,  but  a  circular  mass  surrounding  the  sella 
turcica.     Besides,  the  occipital  arteries  concur 

1,  Reseau  admirable;   2,  Trunk   of  the    in  its  formation,  and  pass  into  its  posterior  part 
originating  arteries  of  the  reseau  ad-    (Fig.  288). 

(This  reseau  admirable  is  the  "  rete  mira- 
bile''  of  Galen,  and  would  appear  to  be  formed 
on  the  carotid  and  vertebral  arteries  of  animals, 
which,  in  a  state  of  nature,  feed  from  the 
ground ;  the  object  being  to  furnish  an  equable 
and  prolonged  supply  of  blood  without  the  risk 
of  check  or  hindrance,  and  thus  to  obviate  the 
tendency  to  congestion  of  the  brain  during  the 
dependent  position  of  the  head.  This  minute  subdivision  and  subsequent  reconstitution 
of  an  artery,  with  a  like  intention,  is  also  observed  in  other  creatures  besides  grazing 


THE   RESEAtr   ADMIRABLE   OF   THE   OX; 
POSTERIOR   FACE. 


mirable ;  3,  Spheno-spinous  artery;  4, 
Trunk  of  the  encephalic,  or  internal 
carotid  arteries ;  5,  Branches  of  the 
occipital  passing  to  the  reseau  admir- 
able;  6,  Interspinal  arterial  canal, 
formed  by  the  intervertebral  spinal 
branches. 


TEE  COMMON  CAROTID  ARTERIES. 


595 


animals.  The  vessels  in  the  mm  of  the  sloth  are  so  di.-poseJ  that  the  animal  can  remain 
suspended  by  it  for  long  periods,  and  a  similar  arrangement  is  noted  in  the  legs  of  birds, 
snoh  as  the  swan,  goose,  ite.,  which  stand  for  a  long  time.  Around  the  Horse's  foot  the 
arteries  break  up  into  numerous  divisions,  and  we  know  that  this  animal  can  remain 
iu  a  standing  attitude  for  Uionths,  and  even  years.  1  he  rete  ophthalmicum  of  birds  is 
arranged  like  the  rete  mirabile.  The  same  object  is  sometimes  attained  by  great  tor- 
tuosity, as  we  have  already  seen  in  the  description  of  several  of  the  arteries.  Perhaps 
the  most  marked  example,  l.owever,  is  to  be  found  in  the  carotid  artery  of  the  Seal, 
which  is  nearly  forty  times  longer  than  the  space  it  has  to  traverse.) 

COMPARISON   OF   THE   CAROTID   ARTERIES   OF   MAN   AVITH   THOSE   OF   AXIMALS. 

The  common  carotids  of  Man  have  a  separate  origin,  the  right  arising  from  the 
arteria  innominata.  the  left  from  the  arch  of  tiie  aorta.  At  the  inferior  border  of  the 
thyroid  cartilage,  they  termiuate  by  only  two  branches :  the  external  und  internal 
carotids ;  the  occipital  artery  is  but  a  division  of  the  former. 

Fis.  289. 


ARTERIES  OF   THE   FACE   AND   HEAD   OF   MAN. 

1,  Common  carotid ;  2,  Internal  carotid ;  3,  External  carotid ;  4,  4,  Occipital 
artery  ;  5,  Superior  thyroid  artery  ;  6,  Trapezius ;  7,  Lingual  artery  ;  8,  Sterno- 
mastoid ;  9,  Facial  artery :  10,  Temporal  artery,  dividing  into  anterior  and 
posterior  branches;  11,  Submental  branch;  12,  Transverse  focial  artery;  13, 
Inferior  labial  branch  ;  15,  Inferior  coronary,  and,  17,  Superior  coronary  branch  ; 
19,  Lateral  nasal  branch;  21,  Angular  branch. 


Internal  Carotid  Artery. — Contrary  to  what  is  observed  in  animals,  the  internal 
carotid  is  a  little  larger  than  the  external,  a  difference  which  is  explained  in  Man  by 


5D6  THE  VEINS. 

the  predominance  of  the  cranium  over  the  face.  This  vessel  describes  a  flexuous  course 
until  it  reaches  the  carotid  foramen  la  the  petrous  bone;  it  forms  two  curves  in  the 
cavernous  sinus,  penetrates  the  dura  mater,  and  divides  at  the  fissure  of  Sylvius  into 
four  branches,  which  are,  as  in  Solipeds :  the  posterior  communicating,  anterior  cerebral, 
middle  cerebral,  and  artery  of  the  choroid  plexus.  The  internal  carotid  has  an 
important  collateral  braucli,  the  ophthalmic  artery .  that  arises  from  the  convexity  of 
the  curve  the  carotid  makes  inside  the  anterior  clinoid  process,  at  the  bottom  of  the 
orbit.  If  it  difters  at  its  origin,  yet  this  vessel  has  a  distribution  analogous  to  that 
already  described. 

External  Carotid  Artery. — In  its  origin,  course,  and  termination,  the  external 
comports  itself  as  iu  animals.     It  gives  rise  to  six  branches  : 

1.  The  superior  thyroid,  resembling  in  its  distribution  the  thyro-laryngeal  of 
Solipeds. 

2.  Tlie  lingual  artery,  which  furnishes  a  sublingual,  and  takes  the  name  of  ranine 
at  its  termination. 

3.  The  facial  artery,  -which  gives  off  the  palatiua  ascendens  analogous  to  our 
pharyngeal,  and  the  submental. 

4    The  posterior  auri'-ular  artery. 

5.  Tiie  inferior  pharyngeal  artery. 

6.  The  occipital.  -This  vessi4  represents  the  occipital  of  the  Horse  minus  its  cerebro- 
spinal liranch.  It  gives  off"  a  mastoid  artery,  and  terminates  in  the  muscles  of  the  neck 
and  on  the  posterior  aspect  of  the  cranium.  The  cerebro-spinal  branch  is  replaced  by 
the  termination  of  the  vertebral  artery,  which  forms  on  Ihe  inferior  face  of  the  medulla 
oblongata  the  basilar  trunk,  whose  disposition  is  identical  with  that  already  described. 

The  superficial  temporal  artery,  and  the  internal  maxillary  artery,  constitute  the 
termination  of  ihe  external  carotid. 

The  internal  ma.nllnry  is  directed  towards  the  spheno-palatine  or  nasal  foramen, 
into  which  it  passes  and  terminates  as  the  spheno-spinous  artery.  It  does  not  give  off 
the  ophthalmic  artery,  that  vessel  coming  from  the  internal  carotid;  but  it  furnishes 
all  Ihe  other  branches  we  liave  studied  iu  animals.  There  are,  therefore  :  a  tympanic 
artery  ;  a  meningeal,  middle,  or  spheno-spinous ;  an  anterior  ami  posterior  deep  temporal ; 
an  inferior  dental;  a  bucc(d ;  a  masseteric;  pterygoideans ;  and  a  descending  palatine 
or  paiato-Libial  artery. 


THIRD  SECTION. 

The  Veins. 

CHAPTER    I. 

GENERAL    CONSIDERATIONS. 


Definition. — The  veins  are  tlie  centrijietal  vessels  of  tlie  circulatory 
system.  They  bring  back  to  the  heart  the  blood  which  had  been  carried 
from  that  viscus  to  the  organs.  Some  j^roceed  from  the  lungs,  carrying 
red  blood,  and  converge  tovs^ards  the  left  auricle  of  the  heart :  these  are 
the  pulmonary  veins,  or  veins  of  the  lesser  circulation.  Others  emerge  from 
the  mass  of  all  the  organs,  transport  the  dark  blood,  and  open  into  the  right 
auricle  :  these  are  the  veins  of  tlie  general  circulation. 

There  are,  therefore,  two  venous  systems  commencing  by  a  capillary 
network,  opposite  an  arterial  network.  Sometimes  a  third  system  of  veins 
has  been  described  for  the  intestines ;  indeed,  the  vena  portse  offers  a  certain 
independence  in  the  midst  of  the  veins  of  the  general  circulation,  as  it 
terminates  in  a  capillary  plexus  in  the  interior  of  the  liver,  and  by  this 
plexus  it  communicates  with  the  posterior  vena  cava. 

External  Conformation.- — The  veins,  after  succeeding  the  capillary  net- 
work  which  terminates  the   arteries,  or  the  cells  of  the  erectile  tissues, 


GENERAL  CONSIDERATIONS.  597 

form  a  series  of  convergent  ramifications  wbicli  repeat,  in  a  general  manner, 
but  in  an  inverse  sense,  tlie  arterial  ramifications  whose  course  they  for 
the  most  part  follow.  A  certain  number,  nevertheless,  are  placed  at  some 
distance  from  the  arterial  trunks,  beneath  the  external  tegnmentary 
membrane,  where  they  are  disjjosed  in  a  vast  network  which  constitutes 
the  superficial  veins  of  the  body.  Apart  from  this  peculiarity,  we  have 
nothing  more  to  say  with  regard  to  the  situation,  direction,  relations,  and 
anastomoses  of  the  veins  than  has  been  already  made  known  in  studying 
the  arteries.  It  is  only  to  be  remarked,  that  the  anastomoses  of  the  venous 
system  are  more  numerous,  larger,  and  more  complicated,  than  those 
of  the  arterial  system  ;  that  they  also  communicate  with  more  voluminous 
trunks ;  and  that  they  very  often  join  the  deep  to  the  superficial  veins. 
At  certain  points  (external  genital  organs,  bladder,  rectum),  the  anastomoses 
are  so  numerous  as  to  constitute  veritable  venous  plexuses.  These  are  more 
especially  met  with  in  regions  where  the  circulation  is  exposed  to  be  more 
or  less  hindered,  either  from  the  displacement  of  organs  or  variations  in 
their  volume. 

With  regard  to  form,  we  also  find  a  close  analogy  between  the  veins 
and  arteries.  The  majority  of  the  first,  at  least,  represent — as  do  the  second 
— cylindrical  tubes,  slightly  knotted,  it  is  true,  on  those  parts  of  their  track 
which  correspond  to  their  valves ;  the  only  exceptions  are  found  in  the 
venous  dilatations  of  the  dura  mater — polyhedral  spaces  which  are  designated 
sinuses.  On  the  other  hand,  veins  oifer  the  same  collective  form  as  the 
arteries;  the  general  volume  of  the  venous  ramifications  being  as  much  more 
developed  as  they  are  distant  from  the  heart,  all  the  branches  collected  at 
last  into  an  imaginary  single  canal  would  form  a  hollow  cone  whose  apex 
would  correspond  to  the  auricles. 

It  is  only  in  comparing  the  two  orders  of  vessels  with  reference  to  their 
number  and  capacity,  that  we  can  discover  any  sensible  difference.  The 
veins  are  more  numerous  than  the  arteries,  as  a  great  number  of  the  latter 
are  accompanied  by  two  of  the  former,  and  the  subcutaneous  veins  have  no 
representatives  in  the  arterial  system.  All  the  veins  being,  besides,  much 
more  voluminous  than  the  corresponding  arteries,  it  follows  that  the  total 
capacity  of  the  venous  system  much  surj)asses  that  of  the  arterial  tree,  and 
that  we  may  boldly  consider  the  relation  of  two  to  one  as  being  the  approxi- 
mative expression  of  this  difference. 

When  the  veins  are  compared  with  the  arteries,  it  is  remarked  that  the 
relations  between  the  length  of  the  trunks  and  branches  are  reversed.  In 
the  arteries,  the  trunks  are  large  and  the  branches  short ;  in  the  veins,  on 
the  contrary,  the  branches  are  relatively  much  longer  than  the  trunks. 
This  disposition  favours  the  flow  of  the  blood  in  the  veins,  at  whose 
commencement  we  do  not  find,  as  in  the  arteries,  a  propelling  organ. 

Another  arrangement  to  answer  the  same  end,  in  opposing  the  influence 
that  atmospheric  pressure  might  have  on  the  veins,  is  the  attachment  of 
these  vessels  to  the  walls  of  the  cavities  they  pass  through  ;  this  is  observed, 
for  instance,  at  the  entrance  to  the  thorax. 

This  disposition,  so  favourable  to  the  circulation  of  the  blood,  becomes 
a  constant  source  of  danger  to  the  surgeon,  by  its  permitting  the  intro- 
duction of  air  into  the  circulatory  system  when  a  vein  is  opened. 

Internal  Conformation. — The  interior  of  the  veins  is  remarkable  for 

the  presence  of  valvular  folds,  whose  disposition  resembles,  in  principle,  that 

of  the  sigmoid  valves  of  the  heart.     These  veins  offer :  an  adherent  border 

attached  to  the  walls  of  the  vessel ;   a  free,  semilunar  border ;  a  concave 

41 


598  THE  VEINS. 

face  turned  towards  the  heart  when  the  valves  are  tense  ;  and  a  convex  face 
which,  on  the  contrary,  looks  towards  the  roots  of  the  veins. 

These  valves  are  often  isolated,  and  sometimes  joined  in  twos  or  threes  ; 
according  to  some  authorities,  they  are  even  found  four  or  five  together, 
arranged  in  a  circular  manner.  All  the  veins  are  not  provided  with  them, 
however,  and  where  they  exist  they  may  be  more  or  less  numerous.  They 
are  absent  in  the  pulmonary  system,  and  in  the  trunk  of  the  vena  cava; 
absent  or  quite  rudimentary  throughout  the  extent  of  the  vena  port« ;  rare 
and  slightly  developed  in  the  vena  azygos,  the  veins  of  the  testicle,  uterus, 
and  ovary ;  and  very  numerous,  very  large,  and  very  complete  in  the  veins 
of  the  limbs. 

The  function  of  these  valves  is  to  favour  the  course  of  the  blood,  and 
to  oi)pose  its  reflux  from  the  heart  towards  the  organs.  Applied,  as  they 
are,  to  the  walls  of  the  veins  by  their  concave  face  during  the  regular  and 
normal  circulation,  they  are  disposed  as  a  transverse  valve  to  sustain  the 
column  of  blood  when  any  strain  or  pressure  gives  that  column  a  retrograde 
movement. 

Structure. — The  walls  of  the  veins  are  thin,  semi-transparent,  and 
elastic,  and  collapse  when  the  vessels  are  empty.  Like  the  arteries,  they 
have  three  tunics. 

The  internal  tunic  is  composed  of  an  epithelial  layer  of  elongated  cells, 
lying  on  an  elastic  membrane  made  up  of  longitudinal  fibres.  In  the  small 
veins,  besides  the  epithelium  and  elastic  fibres,  are  striped  layers  with 
elongated  nuclei.  This  tunic  is  the  most  important ;  it  is  persistent,  while 
the  other  two  may  be  absent  in  certain  veins. 

The  middle  tunic  is  much  thinner  than  that  of  arteries,  and  has  fewer 
muscular  and  elastic  fibres,  while  its  tint  is  rather  red  than  yellow. 
The  proportion  of  smooth  fibres,  disposed  in  a  circular  manner  in  the 
midst  of  the  connective  tissue,  varies  with  the  volume  and  situation  of 
the  veins ;  being  more  considerable  in  the  small  than  the  large  vessels, 
and  also  in  those  through  which  the  blood  circulates  with  difficulty. 

The  external,  or  adventitious  tunic,  is  formed  by  connective  tissue  and 
some  longitudinal  fasciculi  of  elastic  and  muscular  fibres. 

In  the  veins  of  the  bones,  and  in  the  sinuses  of  the  dura  mater,  the  two 
latter  tunics  may  be  absent,  and  the  walls  of  the  vessels  only  consist  of 
epithelium. 

The  veins  have  very  numerous  vasa  vasorum,  which  form  a  complete 
net.vork  around  them.  The  vena  portae  alone  is  accompanied  by  nervous 
filaments  of  the  great  sympathetic. 

(As  remarked,  the  superficial  veins  are  generally  unaccompanied  by 
arteries ;  they  usually  pass  between  layers  of  superficial  fascia,  and  at  the 
most  convenient  situations — generally  those  best  protected — pass  through 
the  underlying  fascia  to  terminate  in  the  deep  veins.  These  are  most 
frequently  accompanied  by  arteries,  being  often  inclosed  in  the  same  sheath 
with  them,  particularly  in  the  extremities.  With  a  large  number  of  arteries 
there  are  two  veins,  one  on  each  side,  the  venoi  comites,  though  the  largest 
arteries  have  only  one  venous  trunk.  The  large  and  frequently  repeated 
communications  are  undoubtedly  intended  to  compensate  for  the  thinness  of 
their  parietes,  which  exposes  to  obstruction  and  dilatation ;  this  they  cannot 
overcome,  because  of  the  slowness  with  which  the  blood  passes  through 
them.  The  valves  are  accessory  to  these  inosculations ;  upon  the  cardiac 
face  of  each  valve  the  vein  is  expanded  into  two  sinuses,  which  correspond 
with  the  extent  of  the  valve ;  these  pouches  give  the  distended  vessel  its 


TEE  CARDTAC  OR  COBONART  VEINS.  599 

nodulated  appearance.  Remak  found  longitudinal  muscular  fibres  iu 
the  adventitia  of  the  large  veins  of  the  Ox  and  Sheep,  but  chiefly  iu  the 
hepatic  portion  of  the  posterior  vena  cava  and  the  veins  of  the  liver.) 

Injection  op  the  Veins. — To  render  the  dissection  and  study  of  the  veins  more  easy, 
tl-ey  ought  to  be  filled  with  tallow  or  any  other  solidifiable  matter,  like  the  arteries.  But 
to  attain  this  result  the  same  mode  of  proctdure  cannot  be  employed  ;is  for  them. 
Instead  of  causing  the  injecting  material  to  flow  from  the  trunk  into  the  branches,  it  is 
necessary  to  propel  it  from  the  branches  towards  the  trunk,  because  of  tlie  presence  of 
the  valves ;  this  is  to  be  done  by  successively  fi.'^ing  the  canula  into  several  venous 
branches. 

Four  injections  generally  suffice  to  fill  the  whole  venous  system  in  a  satisfactory 
manner.  The  first  is  made  from  the  alveolar  vein,  beneath  the  masseter  mufcle ;  the 
second  from  a  digital  vein  of  one  or  both  anterior  limbs,  or  from  the  side  of  the  foot, 
after  having  destroyed  by  a  stylet  the  few  valves  which  are  sometimes  found  towards  the 
point  of  union  in  this  vein  ;  or  from  the  side  of  the  heart.  The  third,  from  the  po.sterior 
digital  veins,  in  the  same  way;  the  fourth,  by  an  intestinal  vein.  If  any  important  veins 
are  empty  after  these  four  injections,  a  case  of  frequent  occureuce,  tiiey  can  be  directly 
injected. 


CHAPTEE  II. 
VEINS  OF   THE  LESSER  CIRCULATION,  OR  PULMONARY  VEINSj 

The  pulmonary  veins  comport  themselves  in  the  same  manner  as  the 
corresponding  arteries.-  They  are  lodged  in  the  substance  of  the  lung  (com- 
mencing in  the  capillaries,  upon  the  walls  of  the  intercellular  spaces  and  air- 
cells,  joining  to  form  a  single  trunk  for  each  lobe),  and  collect  in  from  four 
to  eight  trunks,  which  open  into  the  roof  of  the  left  auricle,  after  emerging 
from  the  pulmonary  organ  immediately  above  the  origin  of  the  bronchi. 
As  they  are  destitute  of  valves,  they  readily  allow  the  blood  to  flow  towards 
their  roots.  It  is  they  which  carry  to  the  left  heart  the  fluid  thrown  into 
the  lung  by  the  right  ventricle,  to  be  submitted  to  the  revivifying  influence 
of  the  atmosphere. 


CHAPTER  III. 

VEINS  OF  THE  GENERAL  OR  SYSTEMIC  CIRCULATION. 

These  vessels  bring  to  the  right  auricle  the  blood  which  has  been  dispersed 
in  the  texture  of  organs,  by  the  ramifications  of  the  great  arterial  tree. 

They  open  into  the  auricle  by  forming  three  groups:  the  group  of 
coronary  or  cardiac  veins  ;  the  anterior  vena  cava,  and  the  posterior  vena  cava. 

Article  I. — Cardiac  or  Coronary  Veins. 

There  are  several  small,  and  one  large  or  great  coronary  vein. 

Small  Cardiac  Veins. — These  are  the  almost  insignificant  vessels,  un- 
determined in  number,  which  come  from  the  walls  of  the  right  ventricle  and 
open  directly  into  the  corresponding  auricle  at  the  coronary  groove. 
(Among  these  may  be  included  the  debatable  vense  Thehesii,  a  multitude  of 
minute  venules  said  to  arise  in  the  structure  of  the  heart  and  open  directly 
into  its  cavities.) 

Great  Coronary  Vein  (Figs.  258,  5  ;  259,  o,  _p).— This  vein  is  formed 
by  two  roots :  one  is  lodged  iu  the  right  ventricular  groove,  and  accompanies 


600  THE  VEINS. 

the  cardiac  artery  of  the  same  side;  the  other  follows  at  first  the  left 
ventricular  groove,  ascends  nearly  to  the  pulmonary  artery,  and  is  then 
inflected  backwards  by  placing  itself  in  the  coronary  groove,  along  with  the 
horizontal  branch  of  the  left  cardiac  artery.  Turning  round  the  base  of  the 
posterior  ventricle,  it  joins  the  right  root,  near  the  upper  extremity  of  its 
groove.  The  common  trunk  resulting  from  this  junction,  after  a  short  course, 
opens  into  the  right  auricle,  below  and  within  the  embouchui-e  of  the  posterior 
vena  cava. 

In  their  track,  the  two  branches  of  the  coronary  vein  receive  branches 
which  escape  from  the  auricular  and  ventricular  walls. 

The  hroncTiial  veins,  ramifying  on  the  bronchi  like  the  arteries,  whose 
satellites  they  are,  also  open  into  the  great  coronary  vein,  very  near  its 
embouchure,  after  becoming  a  single  vessel,  which  is  sometimes  thrown 
dii'ectly  into  the  auricular  cavity. 

Article  II. — Anterior  Vena  Cava.     (Figs.  258,  r ;  259,  d ;  293.) 

This  is  a  voluminous  trunk,  which  ought  to  be  considered  as  the  corres- 
ponding vein  of  the  anterior  aorta.  It  extends  from  the  entrance  of  the 
chest  to  the  right  auricle,  into  the  roof  of  which*  it  is  inserted.  It  is  com- 
prised between  the  two  layers  of  the  anterior  mediastinum,  and  lies 
below  the  trachea,  to  the  right  of  the  anterior  aorta. 

Four  large  vessels — the  two  jugular  and  two  axillary  veins — opening  in 
common  in  the  space  comprised  between  the  two  first  ribs,  constitute  the 
roots  of  this  vessel. 

Collateral  Affluents. — The  afiluent  vessels  which  the  anterior  vena 
cava  receives  in  its  course  are :  the  internal  thoracic,  vertebral,  superior 
cervical,  and  dorsal  veins,  and  the  great  vena  azygos. 

Internal  Thoracic  (or  Internal  Mammary)  Vein. — A  satellite  of  the 
artery  of  the  same  name,  this  vein  opens  into  the  anterior  vena  cava,  at  its 
origin  (Fig.  293). 

Vertebral  Vein. — It  accompanies  the  corresponding  artery  in  the  canal 
formed  by  the  foramina  in  the  transverse  processes  of  the  cervical  vertebra, 
and  joins  the  vena  cava  at  the  origin  of  that  artery  (Fig.  293). 

Superior  Cervical  Vein. — Exactly  resembles  the  artery  whose  name 
it  bears. 

Dorsal  Vein. — This  vessel  follows  the  dorso-muscular  artery,  and,  like 
it,  presents  a  subcostal  branch.  On  the  left  side,  this  branch  is  designated 
the  small  vena  azygos,  and  is  often  prolonged  to  the  eleventh  or  twelfth  rib ; 
it  receives  the  intercostal  veins  of  the  spaces  it  crosses. 

It  may  be  remarked  that  the  vertebral,  superior  cervical,  and  dorsal 
veins  of  the  right  side,  are  nearly  always  thrown  separately  into  the  vena 
cava,  while  on  the  left  side  they  constantly  unite  to  form  a  single  trunk 
(Figs.  258,  tt  ;  293). 

Great  Vena  Azygos  (Figs.  258,  x:  259,  e;  293).— This  is  a  long 
single  vein,  which  commences  at  the  first  lumbar  vertebra,  and  extends 
forward  on  the  right  of  the  thoracic  aorta,  beneath  the  bodies  of  the  dorsal 
vertebrae  to  about  the  sixth,  when  it  is  inflected  downward  to  terminate  in 
the  anterior  vena  cava,  near  the  embouchure  of  that  vessel,  or  even  directly 
into  the  right  auricle. 

In  its  course,  the  great  vena  azygos  is  maintained  against  the  bodies 
of  the  dorsal  vertebrae  by  means  of  the  parietal  pleura  ;  it  runs  along- 
fiide  the  outer  border  of  the  thoracic   duct,  which  separates  it  from  the 


THE  ANTERIOR  VENA  CAVA.  601 

aorta.^  The  terminal  extremity  of  its  iuflection  crosses  the  oesophagus  and 
trachea  to  the  right,  and  is  included  between  these  two  tubes  on  the  one 
side,  and  the  right  layer  of  the  mediastinum  on  the  other. 

Its  roots  are  some  branches  emerging  from  the  spinal  and  psoas  muscles, 
and  which  are  not  usually  in  direct  communication  with  the  posterior  vena 
cava,  as  in  Man  and  the  other  animals. 

During  its  progress,  it  receives  the  first  lumbar  and  the  satellite  veins 
of  all  the  aortic  intercostal  arteries,  right  and  left.  But  when  the  small 
vena  azygos  is  prolonged  backwards  beyond  the  posterior  extremity  of  the 
subcostal  artery,  that  vessel,  as  we  have  already  seen,  forms  the  confluent  of 
a  certain  number  of  left  posterior  iutercostals 

JUGULAR   VEINS. 

The  jugular  is  a  satellite  vein  of  the  carotid  artery. 

Origin. — It  commences  behind  the  inferior  maxilla,  below  the  articula- 
tion of  the  jaw,  by  two  large  roots :  the  superficial  temporal  trunk  and  the 
infernal  maxillary  vein,  which  correspond  to  the  two  terminal  branches  of 
the  external  carotid  artery  (Fig.  '290). 

Situation — Direction. — This  vessel  passes  downward  and  backward, 
lodged  at  first  in  the  substance  of  the  parotid  gland,  afterwards  in  the 
muscular  interstice  designated  the  jugular  channel,  and  which  is  comprised 
between  the  adjacent  borders  of  the  levator  humeri  (mastoido-humeralis)  and 
sterno-maxillaris  muscles.  Eeaching  the  inferior  extremity  of  the  neck,  it 
terminates  in  the  following  manner  (Fig.  290)  : 

Termination. — On  arriving  near  the  entrance  to  the  chest,  the  two 
jugulars  unite  in  forming  a  vessel  named  the  confluent  of  the  jugulars.  This 
confluent,  into  the  sides  of  which  open  the  two  axillary  veins,  is  comprised 
between  the  two  first  ribs,  and  situated  below  the  trachea,  in  the  middle  of  the 
lymphatic  glands  at  the  opening  of  the  chest.  Fixed  by  fibrous  bands  to  the 
neighbouring  parts,  and  particularly  to  the  two  first  ribs,  the  walls  of  the 
jugular  confluent  do  not  collapse  when  the  venous  system  is  in  a  state  of 
vacuity  :  an  anatomical  peculiarity  which  it  is  necessary  to  understand,  in 
order  to  explain  the  manner  in  which  air  obtains  an  entrance  into  the  circu- 
latory system  when  the  jugular  or  axillary  veins  are  opened,  as  well  as 
affording  an  indication  how  to  prevent  this  serious  accident. 

Relations. — At  its  upper  extremity,  the  jugular  vein  is  surrounded  by  the 
parotideal  tissue.  For  the  remainder  of  its  extent,  it  is  covered  externally 
by  the  subcutaneous  muscle  of  the  neck,  and  by  the  branches  of  the  cervical 
plexus  which  creep  on  the  external  surface  of  that  muscle.  Inwardly, 
its  relations  vary  as  we  consider  its  situation,  above  or  below :  above,  it 
responds  to  the  subscapulo-hyoideus  muscle,  which  separates  it  from  the 
common  carotid  and  its  satellite  nerves ;  in  its  inferior  moiety,  it  is  in 
direct  relation  with  that  vessel,  which  is  above  it,  as  well  as  with  the  trachea, 
and  even,  though  only  on  the  left  side,  with  the  oesophagus. 

Collateral  Affluent  Vessels. — The  collateral  veins  which  go  to  the 
jugular  from  its  origin  to  its  termination,  are :  1,  Maxillo-muscular  veins; 
2,  Posterior  auricular  vein  ;  3,  Occipital  vein  ;  4,  External  maxillary,  or  glosso- 
facial  vein;  5,  Thyroid  vein;  6,  Cephalic  vein;  7,  Parotideal  and  innominate 
muscular  branches. 

A.  Maxillo-muscular  Veins. — Two  in  number,  corresponding  to  the 

'  Sometimes  the  azy.c;os  is  situated  between  the  aorta  and  the  thoracic  duct.  When 
the  latter  lies  to  the  left  side,  it  is  in  direct  teontact  with  the  posterior  acrta. 


602  THE  VEINS. 

branches  of  tlie  artery  of  the  same  name,  and  entering  the  jugular  close  to 
its  origin,  either  separately,  or  after  forming  a  common  trunk  (Fig.  290), 

B.  Posterior  Auricular  Vein. — A  voluminous  vessel  which  commences 
on  the  concha,  and  descends  on  the  external  face  of  the  parotid  gland,  near 
its  posterior  border,  where  it  is  joined  by  numerous  divisions  from  the 
parotid  lobules.  It  opens  into  the  jugular  vein,  generally  a  little  below,  and 
opposite  to,  the  maxillo -muscular  vessels,  though  it  is  sometimes  lower,  and 
even  beyond  the  occipital  vein  (Fig.  290). 

C.  Occipital  Vein. — The  occipital  vein  corresponds,  in  every  respect,  to 
its  fellow  artery.  It  offers  two  roots :  an  anterior,  which  originates  at  the 
posterior  extremity  of  the  subsphenoidal  confluent ;  and  a  posterior,  com- 
mencing beneath  the  transverse  process,  of  the  atlas,  and  formed  by  three 
principal  branches. 

Among  the  branches  of  the  latter '  root,  one  passes  with  the  retrograde 
artery  through  the  posterior  foramen  of  the  atlas,  and  constitutes,  as 
it  were,  the  origin  of  the  vertebral  vein  ;  the  second  communicates  with  the 
occipito-atloid  sinuses,  by  traversing  the  atlas  near  its  middle ;  the  third, 
satellite  of  the  cerebro-spinal  artery,  comes  also  from  these  sinuses,  and 
receives  the  venules  which  accompany  the  ramifications  of  the  occipito- 
muscular  artery. 

D.  External  Maxillary  or  Glosso-facial  Vein. — A  satellite  of  the 
artery  of  the  same  name,  this  vessel  begins  on  the  forehead  by  two  roots  :  a 
superior  and  inferior,  analogous  in  every  point  to  the  terminal  branches  of 
the  artery.  It  descends  along  the  anterior  border  of  the  masseter  muscle, 
gains  the  maxillary  fissure,  into  which  it  is  inflected,  placing  itself  between 
the  artery  and  Stenon's  duct;  then  proceeds  backwards  and  downwards 
on  the  internal  pterygoid  muscle,  always  accompanied  by  the  glosso-facial 
artery  until  near  the  anterior  extremity  of  the  maxillary  gland,  when 
it  leaves  it  to  follow  the  inferior  border  of  that  gland,  and  enters  the  jugular, 
after  crossing  the  sterno-maxillaris  muscle  outwardly,  and  forming  with  the 
latter  vein  an  angle  which  is  occupied  by  the  inferior  extremity  of  the  parotid 
gland  (Fig.  290). 

Branches  of  origin. — Of  the  two  branches  which,  by  their  union,  constitute 
the  origin  of  the  external  maxillaiy  vein,  the  inferior,  a  satellite  of 
the  nasal  branch  of  the  corresponding  artery,  possesses  no  interest.  The 
superior,  or  angular  vein  of  the  eye,  merits  particular  notice,  as  venesection  is 
sometimes  practised  on  it.  It  arises  near  the  nasal  angle  of  the  eye. 
and  creeps  to  the  external  face  of  the  elevator  muscle  of  the  upper  lip,  below 
the  lachrymal  muscle. 

Collateral  branches. — In  its  progress,  the  external  maxillary  vein 
receives  a  great  number  of  affluents,  the  principal  of  which  are  the  alveolar 
vein,  the  labial  or  coronarij  veins,  the  buccal  vein,  and  the  sublingual  vein. 

a.  Alveolar  t)ein.---This  is  a  considerable  vessel  lodged  beneath  the 
masseter,  and  lying  against  the  great  supermaxillary  bone,  between  the  zygo- 
matic crest  and  the  line  of  the  molar  teeth  (Fig.  291). 

The  disposition  of  this  vessel  is  most  singular ;  its  anterior  ^tremity 
opens  into  the  external  maxillary  vein,  and  its  posterior  extremity ^Sfc^rses 
the  ocular  sheath,  receives  the  ophthalmic  veins,  and  passes,  with  the 
ophthalmic  nerve  of  the  fifth  pair,  into  one  of  the  supra-sphenoidal  canals,  to 
open  into  the  cavernous  sinus  in  the  interior  of  the  cranium.^ 

'  "We  have  also  seen  it  send  into  the  subsphenoidal  canal,  to  tlie  the  inner  side  of 
the  internal  maxillary  artery,  a  slender  branch  that  joined  the  anterior  extremity  of 
the  subsphenoidal  confluent.     But  we  cannot  say  that  tliis  disposition  is  constant. 


THE  ANTERIOR  VENA  CA  VA.  603 

Before  traversing  the  ocular  sh  ath,  aud  towards  tlie  maxillary  hiatus, 
this  vein  receives  the  superior  dental  and  the  confluent  of  the  nasal  veins : 
vessels  which  emerge  from  the  bony  orifices  traversed  hy  the  arteries  of  the 
same  name — that  is,  the  maxillo-dental  canal  and  the  nasal  foramen.  It  also 
receives  the  confluent  of  tlm  palatine  veins,  which  pass  by  the  palatine  groove, 
instead  of  coursing  along  the  palatine  canal  with  the  corresponding  artery. 
In  general,  these  three  branches  do  not  join  the  alveolar  separately,  but 
rather  by  a  common  trunk. 

The  alveolar  vein  does  not  present  a  uniform  volume.  It  increases  from 
before  to  behind  to  the  maxillary  protuberance,  where  it  forms  a  kind 
of  large  reservoir ;  but  in  traversing  the  ocular  sheath  it  suddenly  becomes 
constricted,  and  maintains  a  small  diametur  until  its  entrance  into  the 
cavernous  sinus. 

This  vein  may  be  considered  as  an  affluent  of  the  sinuses  of  the  dura 
mater,  as  well  as  of  the  external  maxillary  vein. 

b.  Labial  or  coronary  veins. — Satellites  of  the  labial  arteries.  The 
stiperior  is  often  rudimentary.  The  inferior,  nlwajs  voluminous,  is 
constituted  by  the  union  of  several  anastomotic  branches  lying  against  the 
external  face  of  the  mucous  membrane  of  the  cheek. 

c.  Buccal  vein. — Among  the  affluents  of  the  external  maxillary  vein, 
ue  cite  this,  because  it  opens  into  the  latter  by  its  anterior  extremity, 
Oijposite  the  inferior  coronary  vein,  with  which  it  sometimes  communicates 
by  a  particular  branch.  But  the  buccal  vein,  properly  speaking,  con- 
stitutes the  root  of  the  internal  maxillary,  and  we  will  describe  it  as  such. 

d.  Sublingual  vein. — A  large  vessel,  formed  of  two  branches,  which  arise 
in  the  substance  of  the  tongue,  and  are  sometimes  thrown  separately  into  the 
internal  maxillary  vein.  This  sublingual  vein  passes  through  the  mylo- 
hyoideas  muscle,  from  within  to  without,  and  joins  the  principal  vessel  at 
the  lymphatic  glands  lodged  in  the  intermaxillary  space. 

E.  Thyroid  Vein. — This  is  a  voluminous  trunk,  resulting  from  the 
union  of  the  venous  divisions  which  accompany  the  laryngeal  and  thyroid 
branches  of  the  thyroid  or  thyro-largyngeal  artery.  It  joins  the  jugular 
beside  the  external  maxillary  vein,  and  most  frequently  above  it. 

F.  Cephalic  ok  Plat  Vein. — A  superficial  vessel,  which  represents 
one  of  the  terminal  branches  of  the  principal  subcutaneous  vein  of 
the  fore-arm.  It  is  lodged  in  the  interstice  of  the  levator  humeri  and 
small  pectoral  muscles,  and  enters  the  inferior  extremity  of  the  jugular 
vein  (Fig.  293). 

G.  Innominate  Veins. — A  certain  number  come  from  the  parotid 
^land,  but  the  principal  arise  in  the  muscles  of  the  neck  and  withers.     One 

of  the  latter  accompanies   the   superior   branch   of  the   cervico-muscular 
artery. 

ROOTS    OF   THE    JUGULAR    VEIN. 

These  are  constituted  by  the  superficial  temporal  and  internal  maxillary 
veins,  which  are  chiefly  fed  by  the  sinuses  of  the  encephalic  dura  mater. 

1.  Superficial  Temporal  Vein. 

Corresjtonding  in  the  most  exact  manner  to  the  temporal  trunk,  this 
vessel  is  lodged  behind  the  posterior  border  of  the  maxilla,  near  the  articula- 
tion of  the  jaw,  beneath  the  parotid  gland,  and  is,  as  it  v.cre,  incrusted  in 
its  tissue. 


G04 


THE  VEINS 


From  the  union  of  these  two  roots,  there  results  : 

1.   'J'he    anterior  auricular    vein,    a    very    large,    often    multiple,   and 
reticulated   branch,    anastomosing    with    the    pturgj^oid   branches   of    the 


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THE  ANTEBIOB  VENA  CAVA.  605 

internal  maxillary  artery.  This  vein  issues  from  the  parieto-temporal 
conduit,  behiud  the  supercondyloid  eminence ;  it  receives  one  or  two 
branches  which  escape  from  this  conduit  by  the  foramina  in  the  temporal 
fossa,  crosses  the  temporal  muscle,  and  is  charged  with  venules  which  arise 
in  the  interior  of  that  muscle,  as  well  as  in  the  textures  of  the  external  ear. 
2.  The  subzygomatic  vein,  a  satellite  of  the  homonymous  artery,  and 
like  it,  divided  into  two  branches :  one  accompanying  the  transverse  artery 
of  the  face,  the  other  the  masseteric  artery.  The  latter  branch  com- 
municates by  its  inferior  extremity  with  the  external  maxillo-muscular  vein ; 
it  joins,  by  its  other  extremity,  an  enormous  branch  which  comes  from  the 
temporal  muscle,  and  which  passes  into  the  corono-condyloid  notch,  after  being 
largely  anastomosed  with  the  deep  temporal  branches  of  the  internal 
maxillary  vein. 

2.  Internal  Maxillary  Vein. 

Remarkable  for  its  enormous  vohnne,  this  vein  creeps  between  the  internal 
masseter  muscle  and  the  maxilla,  in  an  oblique  direction  upwards  and 
backwards.  Arriving  withiu  the  articulation  of  the  jaw,  a  little  below  the 
maxillary  condyle  and  the  external  pterygoid  muscle,  it  joins  the  temporal 
trunk  after  being  slightly  inflected  downwards.  It,  therefore,  runs  its  course 
at  a  certain  distance  from  the  corresponding  artery  (Fig.  290). 

The  interual  maxillary  has  for  its  root  the  buccal  vein,  which  it  succeeds 
near  the  superior  extremity  of  the  alveolo-labialis  muscle. 

Satellite  of  the  artery  and  nerve  of  the  same  name,  this  buccal  vein,  re- 
markable for  its  volume,  is  situated  beneath  the  masseter  muscle,  near  the 
inferior  border  of  the  alveo-labialis  muscle ;  by  its  anterior  extremity  it 
communicates  directly  with  the  internal  maxillary  vein,  nearly  opposite  to 
the  embouchure  of  the  inferior  coronary  vein ;  its  posterior  extremity  is 
continued  directly  with  the  internal  maxillary.  The  collateral  branches 
it  receives  in  its  course  come  from  the  masseter  muscle  and  the  parietes  of 
the  cheek. 

On  its  way  it  receives  a  great  number  of  affluents  ;  these  are  : 

1.  A  large  lingual  vein,  accompanying  the  small  hypoglossal  nerve. 

2.  The  inferior  dental  vein. 

3.  The  trunh  of  the  deep  temporal  veins,  a  large  vessel  situated  in  front 
and  to  the  inside  of  the  temporo-maxillary  articulation,  where  it  com- 
municates with  the  masseteric.  This  vessel  arises  in  the  texture  of  the 
temporal  muscle,  bixt  particularly  in  the  parieto-temporal  confluent,  with 
which  it  joins  by  the  foramina  in  the  temporal  fossa. 

4.  The  pterygoid  veins  (Fig.  291),  numerous  branches,  only  a  portion  of 
which  come  from  the  pterygoid  muscles.  The  others,  springing  from  the 
subsphenoidal  confluent  of  the  sinuses  of  the  dura  mater,  form,  on  the 
superficial  face  of  the  external  pterygoid  muscle,  a  wide-raeshed  network 
which  communicates  posteriorly  with  the  temporal  trunk,  and  anteriorly 
with  the  confluent  of  the  dee})  temporal  veins.  But  as  these  two  vessels  are 
bound  together,  outside  the  temporo-maxillary  articulation,  by  means  of  the 
masseteric  artery,  it  results  that  this  articulation  is  enlaced  on  every  side 
by  one  of  the  richest  venous  plexuses  in  the  whole  economy. 

3.  Sinuses  of  tJie  Dura  Mater. 

We  will  here  describe  not  only  the  sinuses  of  the  encephalic  dura  mater 
which  supply  the  roots  of  the  jugular  vein,  but  also  those  of  the  spinal  dura 


606  ,        THE  VEINS. 

mater,  although  these  empty  themselves  into  other  veins ;  in  order  that  we 
may  be  able  to  consider,  in  their  entirety,  all  the  vessels  of  the  nervous 
centres  which  carry  dark  blood. 

The  Sinuses  of  the  Dura  Matek  in  General. — These  are  vascular 
spaces  comprised  in  the  texture  of  the  external  meninge,  or  situated  between 
that  membrane  and  the  bones  which  form  the  walls  of  the  cerebro-spinal 
sheath,  or  even  excavated  on  the  iuner  surface  of  these  bones.  These  spaces 
diifer  more  particularly  from  the  veins,  by  their  being  generally  of  a  prismatic 
form,  by  being  continually  open,  by  the  absence  of  valves  in  their  interior, 
and  the  presence,  in  some  of  them,  of  himellse  (irabecidce),  or  intersecting 
filaments  (chordce  Willim)  which  stud  their  iuner  surface,  and  make  them 
look  reticulated. 

Their  walls  are  reduced  to  an  epithelial  layer  that  lies  either  on  the  dura 
mater,  or  on  the  osseous  tissue. 

It  is  into  these  sinuses  that  the  veins  of  the  encej)halon  and  the  spinal 
cord  disgorge  themselves. 

The  Sinuses  of  the  Cranial  Dura  Mater  in  Particular. — Four 
principal  will  be  described  :  the  sinus  of  the  falx  cerebri  or  median  sinus, 
the  two  cavernous  or  sphenoidal  sinuses,  and  the  group  of  occipito-atloid 
sinuses. 

1.  Sinus  of  the  Falx  Cerebri,  or  Median  Sinus. — Channeled  in  the 
substance  of  the  falx  cerebri,  and  becoming  wider  as  it  extends  backwards, 
this  sinus  commences  near  the  crista  galli,  and  terminates  on  the  internal 
parietal  protuberance  by  bifurca  ting.  The  two  branches  resulting  from  this 
division  forna  the  origin  of  the  parieto-temporal  coufiuent,  or  ivinepress  of 
Herophilus  (torcular  Herophili). 

2.  Cavernous  or  Supra-sphe  n  oidal  Sinuses. — These  are  two  in  number — 
a  right  and  a  left.  They  occupy,  on  the  internal  face  of  the  sphenoid  bone, 
at  each  side  of  the  sella  turcica,  the  so-called  cavernous  fissures.  Bordered 
outwardly  by  the  superior  maxillary  nerve,  they  receive  at  their  anterior  ex- 
tremity the  insertion  of  the  alveolar  vein.  Posteriorly,  they  join  each  other, 
and  in  doing  so  farm  a  kind  of  arch,  open  in  front,  around  the  pituitary 
gland.  Each  opens  widely  at  the  lacerated  foramen,  into  the  subsi)henoidal 
confluent. 

3.  Occipito-atloid  Sinuses. — By  this  name  is  designated  a  network  of 
larg«  irregular  veins,  situated  beneath  the  external  face  of  the  dura  mater, 
on  the  sides  of  the  occijiital  foramen,  and  on  the  entire  internal  surface 
of  the  atloidean  ring.  Anteriorly,  these  venous  reservoirs  communicate, 
through  the  condyloid  foramen,  with  the  posterior  extremity  of  the  sub- 
spheuoidal  confluent.  Posteriorly  they  are  continuous  with  the  spinal 
sinuses,  of  which  we  may  consider  them  to  be  the  origin. 

4.  RuDiiME>fTARY  SiNUSES  OF  THE  Ckanial  Dura  Mater. — Independently 
of  the  above-described  reservoirs,  tliere  exist,  on  the  inner  wall  of  the 
cranium,  some  rudimentary  venous  sinuses  which  should  be  indicated;  these 
are  :  1,  One  or  two  veins  lodged  in  the  structure  of  the  tentorium,  designated 
the  petrosal  or  transverse  sinuses,  communicating,  below,  with  the  cavernous 
sinuses,  and  entering,  above,  into  the  parieto-temporal  confluent ;  ^  2,  Some 
small,  irregular,  and  reticulated  cavities,  very  variable  in  their  disposition, 
situated  beneath  the  dura  mater,  on  the  sides  of  the  cerebellar  cavity,  atid 
which    generally    empty  themselves    into    the   subsphenoidal    confluent,  by 

'  ATore  frequently,  perliaps,  these  veins  arise  directly  from  the  substance  of  the  brain, 
and  do  not  communicate,  below,  with  the  cavernous  sinuses. 


THE  ANTERIOR  VENA  CAVA. 


607 


traversing  the  posterior  part  of  tbe  lacerated  foramen,  and  also  opening  some- 
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tatives  of  the  lateral  sinuses  in  Man ;    3,    In   some  instances,  an  inferior 


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603  THE  VEINS. 

median  sinus,  channeled  near  the  free  border  of  the  face  of  the  brain,  passes 
behind  into  the  torcular  Herophili. 

The  Spinal  Sinuses  in  Particular. — We  thns  designate  in  Veterinary 
Anatomy,  and  with  good  reason,  two  series  of  venous  reservoirs  which  are 
found  throughout  the  whole  extent  of  the  vertebral  column,  on  the  sides  of 
the  roof  of  the  si:>inal  canal.  Lodged  in  the  lateral  depressions  of  the 
superior  face  of  the  vertebral  bodies,  at  the  side  of  the  common  superior 
vertebral  ligament,  and  covered  by  the  dura  mater,  these  reservoirs, 
continued  from  one  vertebra  to  the  other,  are  like  two  large,  irregular, 
parallel  veins,  which  commence  at  the  atlo-axoid  articulation,  terminate 
on  the  first  coccygeal  vertebrfe,  where  their  presence  is  yet  well  defined, 
and  communicate  with  one  another  during  their  course  by  transversal 
anastomoses. 

Affluent  Veins  that  open  into  the  Sinuses  of  the  Dura  Mater. — 
TJiese  are  the  vessels  which  carry  blood  either  from  the  dura  mater  itself, 
or  from  the  substance  of  the  nervous  centres :  those  of  the  first  category  are 
rare,  but  the  second  are  numerous.  Although  we  are  unwilling  to  make  a 
detailed  study  of  the  latter,  we  must  nevertheless  notice  what  is  most 
remarkable  in  their  disposition. 

a.  On  the  encephalon,  the  veins  form  a  much  richer  and  closer  network 
than  that  of  the  arterial  ramifications ;  from  this  network  proceed  a 
certain  number  of  principal  branches,  which  throw  themselves  into  the 
sinuses  of  the  cranial  dura  mater.  The  veins  of  the  cerebrum,  for  the  most 
part,  gain  the  median  and  transverse  sinuses ;  a  few  only  pass  into  the 
cavernous  sinuses.  Those  of  the  isthmus  and  cerebellum  go  to  the  i^etrosal 
and  occipito-atloid  sinuses. 

With  regard  to  the  internal  veins  of  the  brain — those  which,  by  their 
interlacing,  constitute  the  choroid  plexus — we  see  them  unite  into  a  large 
trunk — the  great  vein  of  the  brain,  or  vena  Galeni,  which  bends  round  the 
superior  extremity  of  the  corpus  callosum,  reaches  the  interlobular  fissure, 
and"  throws  itself  into  the  falciform  or  middle  sinus,  near  its  posterior 
extremity,  after  receiving  the  superficial  veins  from  tlie  inner  face  of  the 
hemispheres. 

h.  The  venules  arising  from  the  spinal  cord  are  also  very  remarkable  for 
the  fine  network  they  form  on  the  surface  of  the  organ.  They  collect  into  a 
common  trunk — the  median  spinal  vein,  which  runs  from  before  to  behind, 
throughout  the  whole  extent  of  the  superior  groove  in  the  spinal  cord ;  thus 
occupying  an  analogous,  though  oj)posite,  jiosition  to  that  of  the  artery  of 
the  same  name.  From  this  vein  escape,  at  intervals,  emergent  branches  which 
open  into  the  spinal  reservoirs. 

Effluent  Canals  of  the  Dura  Mater  Sinuses. — We  have  to  notice, 
under  this  designation,  the  veins  which  transport  the  blood  from  the  sinuses, 
and  we  will  consider  in  succession  those  which  commence  at  the  encephalic 
reservoirs,  as  well  as  those  that  emerge  from  the  interspinal  canals. 

a.  To  be  carried  from  the  encephalic  sinuses,  the  blood  flows  into  two 
kinds  of  double  gulfs,  known  as  the  jparicto-iemporal  and  suhsphenoidal 
confluents. 

The  parieto-teraporal  confluents  are  lodged  in  the  canals  of  the  same  name, 
along  with  the  mastoid  artery.  Each  commences  at  the  base  of  the  internal 
parietal  protuberance,  and  terminates  behind  the  supercondyloid  eminence. 
The  median  and  transverse  sinuses  are  confounded  with  tlie  superior 
extremity  of  these  reservoirs,  and  empty  into  tliem  the  blood  coming  from 
the  encephalic  mass.     This  fluid  is  subsequently  taken  away  by  the  super- 


THE  ANTEBIOB  VENA  CAVA.  609 

ficial  and  deep  temporal  veins,  which  have  their  principal  roots  in  these 
confluents. 

The  suhsphenoidal  confluents  extend  on  the  sides  of  the  body  of  the 
sphenoid  bone  and  the  basilar  process,  from  the  base  of  the  subsphenoidal 
process  to  the  condyloid  fossa,  by  concurring  in  the  obturation  or  closing 
of  the  occipito-spheno-temporal  hiatus.  They  open  at  their  middle  portion 
into  the  corresponding  cavernous  sinus,  by  an  oval  ajierture  which  the  in- 
ternal carotid  artery  traverses  in  penetrating  into  the  cranium.  The  anterior 
extremity  terminates  in  a  cul-de-sac.  Posteriorly,  they  communicate  through 
the  condyloid  foramina  with  the  occipito-atloid  sinuses.  The  vessels  which 
carry  off  the  blood  from  these  confluents  are  the  pterygoid  veins,  and  the 
anterior  root  of  the  occipital  vein.  We  already  know  that  the  posterior 
branch  of  the  latter  vessel  removes  the  blood  directly  into  the  occipito-atloid 
sinuses. 

b.  The  emergent  veins  of  the  spinal  sinuses  present  a  more  simple  dis- 
position. At  each  intervertebral  space  arise  several  branches,  which  more 
particularly  make  their  exit  by  the  intervertebral  foramina  to  join  the 
neighbouring  veins ;  in  the  cervical  region,  the  vertebral  veins  serve  as  a 
receptacle  in  this  way  for  the  venous  branches  emanating  from  the  spinal 
sinuses  ;  in  the  dorsal  region,  it  is  the  spinal  branches  of  the  intercostals ; 
in  the  loins,  the  analogous  branches  of  the  lumbar  veins  ;  and  in  the  sacral 
region,  the  lateral  sacral  vein. 


AXILLARY   VEINS. 

A  general  confluent  of  all  the  veins  of  the  thoracic  limb,  and  of  some 
from  the  trunk,  the  axillary  vein  commences  beneath  the  scapulo-humeral 
articulation,  towards  the  terminal  extremity  of  the  corresponding  arterial 
trunk,  accompanying  the  latter  to  the  entrance  of  the  chest,  and  joining  the 
confluent  of  the  jugulars  to  constitute,  with  these  two  vessels,  the  inferior 
vena  cava  (293,  18). 

In  studying,  from  their  origin  to  their  termination,  the  numerous 
branches  which  concur  in  the  formation  of  this  venous  trunks  we  re- 
cognise : 

1.  That  they  form  in  the  foot  a  very  rich  network,  from  which  proceed 
the  digital  veins,  satellite  vessels  of  the  homonymous  arteries. 

2.  That  to  these  digital  veins,  which  are  united  in  an  arch  above  the 
larf^e  sesamoids,  succeed  three  metacarpal  branches  or  collaterals  of  the 
cannon:  two  superficials,  placed  on  each  side  of  the  flexor  tendons,  and  a 
profound  (or  deep)  vein,  situated  underneath  the  suspensory  ligament,  along 
with  the  interosseous  arteries. 

3.  That  the  metacarpal  veins  also  open  into  each  other,  in  the  superior 
and  posterior  region  of  the  carpus,  to  form,  on  again  separating,  two  groups 
of  antihrachial  veins :  one  group  comprising  the  tdnar  and  the  posterior  or 
internal  radials,  which  accompany  the  arteries  of  the  same  name  ;  the  other, 
constituted  by  a  single  subcutaneous  branch,  the  median  vein,  which  receives 
at  its  superior  extremity  the  anterior  superficial  radial  vein. 

4.  That  at  the  ulnar  articulation,  these  two  groups  of  antihrachial  veins 
join  the  satellite  vessel  of  the  anterior  radial  artery,  and  communicate  by  a 
very  complicated  system  of  anastomoses,  from  which  results  a  principal 
trunk,  the  humeral  vein. 

5.  That  the  humeral  vein,  after  receiving  on  its  course  several  muscular 


610  THE  VEINS. 

brandies  and  the  subcutaneous  thoracic  vein,  unites  near  tLe  shoulder-joint 
with  the  suhscajmlar  trunk,  to  form  the  axillary  vein. 

We  will  study  all  these  branches  in  the  inverse  order  of  their 
enumeration. 

1.  Subscapular  Vein. 

A  V3ry  considerable  vessel,  whose  disposition  resembles  that  of  the 
subscapular  artery,  though  presenting  some  special  peculiarities  whose 
study  does  not  deserve  a  moment's  delay ;  for  example,  it  most  frequently 
receives  the  satellite  vein  of  the  prehumeral  artery. 

2.  Humeral  Vein. 

Placed  behind  and  within  the  humeral  artery,  this  vessel  commences 
above  the  articulation  of  the  elbow,  being  formed  at  this  point  by  the  anasto- 
mosing system  of  veins  from  the  fore-arm,  and  terminates  below  the  shoulder- 
joint  in  opening  into  the  subscapular  vein. 

Independently  of  the  subcutaneous  thoracic  vein,  which  will  be  studied 
in  a  special  manner,  the  humeral  vein  receives  on  its  way  several  collateral 
satellites  of  the  branches  emanating  from  the  humeral  artery.  One  of  these, 
the  ejncondyloid,  is  only  a  continuation  of  the  ulnar  vein. 

Very  often  we  find  a  second  humeral  vein  in  the  deep  region  of  the  arm  ; 
this  is  an  accessory  vessel,  parallel  to  the  preceding,  and  situated  opposite 
it  in  front  of  the  artery. 

3.  Subcutaneous  Thoracic  or  Spur  Vein. 

This  vein,  which  is  important  to  know,  as  bleeding  is  sometimes 
practised  from  it,  commences  on  the  flank  and  belly  by  numerous  super- 
ficial divisions,  which  unite  in  two  principal  roots,  and  afterwards  become  a 
single  trunk,  placed  in  the  substance,  or  on  the  external  surface  of  the 
panniculus  carnosus,  where  it  is  directed  forwards  in  following  the  superior 
border  of  the  large  pectoral  muscle,  accompanied  by  an  arterial  ramuscule 
and  a  thick  nerve.  It  insinuates  itself  beneath  the  olecranian  muscles, 
and  finally  terminates  in  the  humeral  vein  by  opening  into  the  branch  that 
follows  the  deep  muscular  artery. 

4.  Deep  Veins  of  the  Fore-arm. 

A.  Anterior  Eadial  Vein. — This  follows  the  same  track,  and  affects 
the  same  variations,  as  the  corresponding  artery. 

B.  Posterior  Radial  Veins.— The  posterior  radial  artery  is  always 
accompanied,  and,  as  it  were,  enveloped,  by  a  fasciculus  of  three  or  four 
venous  branches,  which  frequently  anastomose  with  each  other,  and  are 
reinforced  by  collateral  branches,  among  which  the  interosseous  vein  must 
be  noted. 

These  radial  branches  commence  above  the  carpus,  by  continuing  the 
metacarpal  veins.  They  concur  to  form  the  humeral  vein,  in  joining  the 
other  antibrachial  veins  at  the  inferior  extremity  of  the  arm. 

C.  Ulnar  Vein. — This  vessel  is  lodged,  with  the  nerve  and  small  artery 
of  the  same  name,  in  the  interstice  of  the  oblique  and  internal  flexors  of  the 


THE  ANTERIOR  VENA  CAVA.  Cll 

metacarpus.     A  number  of  muscular  aud  subcutaneous  branches  enter  tbis 
vein. 

It  has  the  same  origin  as  the  posterior  radial  veins.  Its  superior  or 
terminal  extremity  bonds  forward,  close  to  the  trunk  of  the  epicondyloid 
artery,  and  goes  to  the  inferior  extremity  of  the  humeral  vein.  Frequently 
the  ulnar  vein  is  double  in  the  latter  portion  of  its  track,  and  between  the 
two  branches  lies  the  artery.  It  always  communicates  at  this  point,  by 
one  or  more  branches,  with  the  deep  muscular  vein. 

o.  Superficial  Veins  of  the  Fore-arm. 

Placed  outside  the  fibrous  sheath  formed  by  the  antibrachial  aponeurosis, 
these  veins,  which  are  principally  two  in  number,  are  maintained  against 
the  external  face  of  that  membrane  by  a  thin  fascia  which  separates  them 
from  the  skin. 

A.  Median,  or  Internal  Subcutaneous  Vein  (Fig.  293,  31). — This  is 
also  one  of  the  vessels  selected  for  the  operation  of  phlebotomy.  It  is  the 
continuation  of  the  internal  metacarpal  vein,  ascends  from  the  inner  face 
of  the  carpus  to  the  superior  extremity  of  the  fore-arm,  by  crossing  the 
radius  in  a  very  oblique  manner,  and  terminates  in  two  very  large 
branches,  the  posterior  of  which  is  the  hasilic  vein,  and  the  anterior  the 
cephalic  vein. 

The  hasilic  vein  traverses  the  sterno-aponeurotic  (transverse  pectoral) 
muscle,  to  aid  in  forming  the  humeral  trunk  (Fig.  293,  S-i). 

The  cephalic,  ov  plat  vein,  crosses  the  superticial  band  of  the  biceps  or 
coraco-radial  muscle,  is  lodged  in  the  space  comprised  between  the  levator- 
humeri  and  small  pectoral  muscles,  and  afterwards  opens  into  the  jugular 
vein  (Fig.  293,  35). 

B.  Subcutaneous,  or  Anterior  Eadial  Vein  (Fig.  293,  32). — Less 
considerable  than  the  preceding,  this  vein  arises  at  the  carpal  region,  in  its 
course  occupies  the  anterior  face  of  the  fore-arm,  and  terminates  in  uniting 
its  superior  extremity  either  to  the  subcutaneous  median  or  the  cephalic 
vein ;  the  last  is  most  frequently  the  case. 

6.  Metacarpal  Veins. 

Three  in  number,  as  we  know,  these  veins  are  distinguished  into  in- 
ternal and  external  collateral  of  the  cannon,  and  deep  or  interosseous  collateral. 

A.  Internal  Collateral  of  the  Cannon. — More  voluminous  than  the 
others,  this  vein  passes  from  the  vicinity  of  the  fetlock  along  the  flexor 
tendons,  accompanied  by  the  principal  artery  of  the  cannon  and  the 
external  plantar  nerve,  places  itself  in  the  special  sheath  which  envelops 
the  common  trunk  of  the  interosseous  arteries  to  the  inside  of,  and  behind 
the  carpus,  to  be  continued  in  the  antibrachial  region  by  the  median 
subcutaneous  vein,  after  communicating  with  the  other  metarcarpal  veins 
(Fig.  293,  30). 

B.  External  Collateral  op  the  Cannon. — Situated  opposite  the 
preceding — to  the  external  side  of  the  flexor  tendons,  in  company  with  the 
corresponding  plantar  nerve — the  external  collateral  of  the  cannon  follows 
that  nerve  to  near  the  trapezium,  and  then  separates  into  several  reticulated 
branches  whicli  anastomose  with  the  internal  collateral,  from  which  proceed 
the  ulnar  and  internal  or  posterior  radial  veins. 


G12  TEE  VEINS. 

C.  Interosseous  Vein. — A  tortuous,  irregular,  and  sometimes  multiple 
vessel,  lodged  with  the  plantar  interosseous  arteries  between  the  suspensory- 
ligament  and  the  posterior  face  of  the  principal  metacarpal  bone.  Eeachiug 
the  superior  extremity  of  that  bone,  it  unites  largely  to  the  right  and  lelt 
with  the  external  and  internal  collaterals,  sending  upwards  one  or  two  small 
branches  which  traverse  the  carpal  sheath  along  with  the  collateral  artery 
of  the  cannon,  and  open  into  the  posterior  radial  branches  above  the  knee. 

7.  Digital  Veins. 

These  veins  occupy,  on  the  sides  of  the  digital  region,  the  same  position 
as  the  homonymous  arteries  in  front  of  which  they  are  placed.  They  arise 
from  the  network  formed  on  the  lateral  cartilages  by  the  veins  of  the  foot, 
and  terminate  in  uniting  above  the  fetlock,  between  the  flexor  tendons  of  the 
phalanges  and  the  superior  sesamoid  ligament,  so  as  to  form  an  arch  from 
which  proceed  the  three  metacarpal  veins  (,Fig.  293,  37). 

8.   Veins  of  the  Foot  or  Ungual    Region. 

The  importance  of  the  region  to  which  these  vessels  belong,  requires  that 
they  should  be  described  more  fully  than  the  other  veins,  and  as  has  been 
already  done  with  the  arteries  of  this  part  of  the  body.  We  will,  therefore, 
borrow  the  exact  and  minute  description  given  by  M.  H.  Bouley.i 

This  venous  apparatus  may  be  divided  into  external  and  internal  or 
intra-osseous. 

a.  External  Venous  Apparatus. 

"The  external  venous  apparatus  of  the  digital  region  is  very  remarkable 
for  the  number,  development,  superficial  distribution,  and  reticulated 
disposition  of  the  canals  composing  it.  To  give  an  idea  of  this,  we  cannot 
do  better  than  compare  its  general  form  to  a  net  whose  irregular  meshes 
are  extended  over,  and  moulded  on,  the  two  last  phalanges  which  are  contained 
in  it. 

"  This  intricate  reticulation  of  the  venous  apparatus  of  the  foot  is 
marvellously  displayed  in  specimens  injected  after  maceration,  and  then 
dried. 

"  To  facilitate  its  description,  we  recognise  in  it  three  parts  distinct  by 
their  situation,  though  they  only  form  a  continuous  one.     They  are  : 

"1.  The  solar  plexus. 

"  2.  The  podophyllous  plexus. 

"3.   The  coronary  plextis. 

"  A.  SoLAK  Plexus. — The  veins  of  the  solar  plexus  are  remarkable  for 
the  equality  of  their  calibre  throughout  the  whole  extent  of  the  plantar 
surface,  and  by  the  almost  absolute  absence  of  anastomotic  communications 
with  the  deep  parts. 

"  Sustained  in  a  special  fibrous  web  (plantar  reticulum),  which  replaces 
the  periosteum  at  the  lower  surface  of  the  phalanx,  and  is  a  continuation  of 
the  cerium  of  the  villous  tissue,  these  veins  appear  indeed  to  have  so  little 
communication,  except  with  each  other,  that  it  is  possible  to  detach  the 
•plantar  reticulum  Ivom  the  superior  face  of  the  third  phalanx  without 
disturbing  them. 

'  '  Traite  de  'Organisation  du  Pied  du  Cheval,'  p,  65. 


THE  ANTERIOR  VEX  A  CA  VA,  613 

"  The  general  disposition  of  the  venous  canals  in  the  texture  of  the 
reticulum  supporting  them,  closely  resembles  that  of  the  secondary  ribs  of 
the  limb  (or  laminar  merithal)  of  certain  asymmetrical  leaves.  In  their 
course  they  follow  an  irregularly-broken  line,  intercepting  each  other  by 
joining  at  short  intervals,  so  as  to  form  unequal-sized,  unsymmetric, 
polygonal  spaces. 

"  These  venous  conduits  have  a  double  canal  for  discharging  themselves : 
a  central,  the  least  considerable  and  least  constant ;  the  other  peripheral 
or  circumflex,  corresponding  to  the  artery  of  the  same  name,^  and  whose 
satellite  vein  it  is. 

"  Central  canal. — The  central  canal  is  formed  by  the  simultaneous 
anastomoses  of  a  crowd  of  venous  ramifications  converging  towards  the 
centre  of  the  digit.  It  is  of  a  parabolic  shape,  and  embraces  in  the  concavity 
of  its  curvature  the  point  of  the  pyramidal  body,  whence  it  throws  its  two 
branches  in  a  parallel  manner  on  the  sides  of  that  body,  into  the  bottom  of 
the  lateral  lacunee  as  far  as  the  cartilaginous  bulbs,  where  it  proceeds 
to  the  external  coronary  plexus.  This  disposition  is  not  constant,  however, 
as  specimens  are  frequently  met  with  in  which  this  central  canal  is  replaced 
by  multiple  veins,  which  are  more  considerable  than  those  foi*ming  the 
whole  of  the  plexus,  and  which  serve  them  as  overfalls  towards  the  super- 
ficial coronary  plexus. 

Circumflex  vein,  or  peripheral  venous  canal. — "  This  vein  is  of  large 
calibre,  and  formed  by  divergent  ramifications  from  the  solar  plexus,  as  well 
as  the  descending  veins  of  the  podophyllous  j^lexus  ;  it  margins  the  external 
limb  of  the  villous  tissue  in  following  a  slightly  undulous  line  within  the 
circumflex  artery,  whose  satellite  it  is.  It  is  sometimes  broken  up,  at 
certain  points  of  its  course,  into  several  smaller  canals  which  are  continuous 
with  its  trimks. 

"  In  its  circular  route,  all  the  divergent  solar  and  descending  podo- 
phyllous veins  are  discharged  into  it,  and  it  terminates,  at  the  extremities  of 
the  crescent  formed  by  the  third  phalanx,  in  several  large  branches  which 
pass  beneath  the  podophyllous  tissue  to  the  lateral  cartilage,  where  they 
concur  to  form  the  superficial  coronary  plexias. 

"  B.  Podophyllous  Venous  Plexus  or  Network. — The  veins  of  the 
podophyllous  plexus  exhibit  a  disposition  analogous  to  those  of  the  solar 
plexus  ;  like  them,  they  are  sustained  in  the  meshes  of  a  fibrous  texture  (the 
reticulum  processigerum  of  Bracy  Clark,  the  suhpodophyllous  reticulum  ot 
French  Veterinarians)  spread  on  the  anterior  surface  of  the  bone,  in  the 
same  way  as  the  periosteum  is  on  other  bones,  and  continuous  with  the 
corium  of  the  laminal  tissue.  Communicating  largely  between  each  other 
by  multiple  anastomoses,  like  the  solar  plexus,  they  appear  to  be  completely 
isolated  from  the  deeper  parts,  from  which  it  is  commonly  believed  they 
emanate. 

"  Tortuous  and  split  up  into  branches  in  their  course,  the  podophyllous 
veins  wind  in  a  serpentine  manner  along  the  length  of  the  laminae  they  cover, 
very  close  to  each  other,  and  forming  narrow  elongated  meshes.  Their 
confluence  is  such,  that  at  certain  points  they  appear  bound  together  by  their 
external  walls. 

"  The  calibre  of  these  vessels  is  tolerably  uniform  throughout  the  extent 
of  the  podophyllous  plexus,  except  towards  the  posterior  parts,  where  their 
principal  canals  empty  themselves  into  the  coronary  plexus. 

"  The  podophyllous  veins  are  in  anastomotic  communication,  below,  with 
'  The  inferior  circumflex  artery  of  the  foot, 
42 


614 


THE  VEINS. 


Fio;.  292. 


the  circumflex  vein  of  the  solar  plexus,  whicli  they  concur  to  form,  and  above, 
with  the  coronary  plexus,  which  is  only  a  continuation  of  them. 

"  C.    Coronary    Venous    Plexus, — The  coronary   venous  plexus  (Fig 

292,  2,  4)  is  arranged  like  a 
ramose  garland  around  the  second 
phalanx  to  the  origin  of  the 
third,  and  on  the  surface  of  the 
cartilaginous  apparatus  which 
completes  the  latter. 

"It  is  supported,  like  the 
other  venous  networks  of  the 
digit,  by  a  fibrous  texture  imme- 
diately subjacent  to,  and  con- 
tinuous with,  the  corium  of  the 
coronary  substance,  and  is  juxta- 
posed, as  well  as  adherent,  to 
the  expansion  of  the  extensor 
tendon,  the  lateral  cartilages, 
and  to  the  bulbous  enlargements 
of  the  plantar  cushion. 

"  This  plexus  proceeds  from 
the  intra- osseous,  podophyilous, 
and  solar  networks.  To  facili- 
tate its  description,  we  recognise 
in  it  three  parts:  one  central 
and  anterior,  situated  between 
the  two  cartilaginous  plates,  and 
two  lateral,  corresponding  to 
these  cartilages. 

"  Central  Part  of  the 
Coronary  Plexus. — The  central 
part  of  the  coronary  plexus  (Fig.  292,  2),  immediately  subjacent  to  the 
substance  or  cushion  of  that  name,  constitutes  a  very  close  network  formed 
by  innumerable  venous  radicles,  which  rise  in  a  tortuous  manner  from, 
and  are  continuations  of,  the  podophyilous  plexus,  until  they  reach  a 
large  anastomotic  vein  thrown  across  from  one  cartilaginous  plexus  to 
the  other,  and  into  which  they  open  by  ten  to  twelve  principal  mouths 
(Fig.  292,  3'). 

"  These  veins  of  the  central  part  of  the  coronary  plexus  gradually 
increase  in  calibre,  and  diminish  in  number,  from  the  podophyllus  plexus, 
where  they  take  their  origin,  to  their  superior  and  terminating  canal,  which 
itself  only  appears  to  be  the  result  of  their  successive  anastomoses. 

"  Cartilaginous  Plexus,  or  Lateral  Parts  of  the  Coronary  Plexus. — 
The  cartilaginous  plates  serve  to  support,  by  their  two  faces  and  the 
canaliculi  by  which  they  are  traversed,  a  mass  of  very  close,  anastomosing, 
and  converging  veins,  which,  from  its  situation,  may  be  designated  the 
cartUagtnous  plexus. 

"This  cartilaginous  plexus  is  forme;!  by  two  layers  of  vessels — a 
superficial  and  deep. 

'^Superficial  cartilaginous  layer  or  plexus. — The  superficial  layer  (Fig. 
292,  3,  4),"  extended  over  the  external  surface  of  the  cartilaginous  plates  and 
bulbs,  has  its  origin  by  innumerable  roots  from  the  veins  of  that  part  of  the 
podophyilous  plexus  corresponding  to  the  superficies  it  occupies.     These 


THE   VEINS  OF   THE    FOOT. 


THE  ANTERIOR  VENA  CAVA.  615 

roots,  massed  in  a  very  dense  network,  converge  towards  the  superior 
portions  by  diminishing  in  number  and  augmenting  in  volume,  and  terminate 
in  forming  themselves,  by  the  aid  of  successive  anastomoses,  into  ten 
or  twelve  principal  branches  which  again  unite  into  two  considerable 
vessels  (Fig.  292,  G),  situated  at  the  superior  limit  of  the  plexus.  These 
vessels,  tinally,  by  their  last  fusion  at  the  inferior  extremity  of  the  first 
phalanx,  constitute  the  digital  vein,  the  satellite  of  the  artery  of  the  same 
name  (Fig.  292,  5). 

''  Considered  from  below  upwards,  in  a  foot  previously  prepared  by 
injection,  the  digital  vein,  divided  into  two  branches,  subdivides  itself 
into  secondary  branches  and  ramuscules  which  diverge  and  spread  over  the 
convex  surface  of  the  cartilage  and  coronary  cushion,  resembling  somewhat 
the  disposition  of  trees  trained  on  esj)aliers,  whose  spreading  branches  are 
fixed  to  the  walls  on  which  they  ramify. 

"  The  two  peripheral  branches  of  the  superficial  cartilaginous  plexus 
establish  communications  with  the  opposite  cartilaginous  plexus,  in  con- 
tracting direct  anastomoses  with  the  branches  of  the  plexus  which  aro 
symmetrical  to  them. 

"  The  anterior  anastomosing  canals  are  double  and  superposed. 

"  The  most  inferior  and  superficial  is  constituted  by  the  large  vein  (Fig. 
292,  3')  thrown  slantingly  across  from  one  plexus  to  the  other  in  the  median 
plane,  and  on  the  external  surface  of  the  extensor  tendon ;  this  receives  a 
considerable  multitude  of  venous  ramuscles,  which  emerge  from  the  anterior 
part  of  the  podophyllous  plexus. 

"  This  first  communicafing  vein  joins  the  anterior  branches  of  the  carti- 
laginous plexus. 

"  The  second  communicating  vein,  situated  three-quarters  of  an  inch  above 
the  first,  and  beneath  the  tendon,  is  thrown  transversely  from  one  anterior 
branch  of  the  plexus  to  the  other.  They  open  into  each  other  on  each  sido, 
at  the  same  point  where  the  first  communicating  vein  enters. 

"  Sinuous  in  the  whole  of  its  track,  sometimes  double,  and  sometimes 
formed  of  several  confluent  veins,  as  in  Fig.  292,  this  anastomosing  canal 
serves  as  an  outlet  for  several  deep  veins. 

"  The  anastomosis  between  the  posterior  peripheral  branches  of  the 
cartilaginous  plexus  is  formed  by  an  irregularly  curved  and  long  vein  of 
large  calibre,  sinuous  or  broken  in  its  course,  but  always  considerably 
longer  than  the  distance  from  the  two  cartilaginous  plates  between  which  it 
is  extended. 

"  This  posterior  communicating  vein  acts  as  a  confluent  to  the  canals 
emerging  from  the  cartilaginous  bulbs,  and  to  the  posterior  part  of  the  solar 
plexus,  which  throws  into  it  five  or  six  well-developed  afferent  veins. 

"  Deep  cartilaginous  layer  or  plexus.  — The  deep  layer  of  the  carti- 
laginous plexus  is  formed  : 

"  1.  By  somewhat  large  ascending  branches  from  the  posterior  part  of  the 
podophyllous  and  solar  plexuses. 

"  2.  By  the  deep  internal  venous  apparatus  of  the  third  phalanx. 

"  3.  By  the  deep  veins  arising  from  the  coronary  bone  and  the  liga- 
ments and  tendons  surrounding  it. 

"  The  ascending  branches  of  the  podophyllous  tissue  are  introduced  by 
the  numerous  foramina  which  traverse  the  base  of  the  cartilaginous  plate 
and  the  inferior  fibrous  covering  of  the  plantar  cushion;  they  follow  the  canals 
which  continue  those  foramina  in  the  substance  of  the  cartilage,  and  reach 
its  internal  face,  along  with  the  branches  proceeding  from  the  intra-osseous 


616  TEE  VEINS. 

venous  system  and  those  coming  from  the  tendons  and  ligaments,  forming  a 
fasciculus  of  five  or  six  thick  converging  veins  which  unite  in  two  large 
ascending  branches.  These  anastomose  with  each  other  before  their  de- 
finitive junction  with  the  two  peripheral  branches  resulting  from  the  super- 
ficial cartilaginous  plexus,  with  which  they  concur  in  constituting  the 
digital  vein." 

h.  Internal,  or  Intra-osseous  Venous  Apparatus. 

"  Girard,  the  younger,  and  Eigot  have  denied  that  the  plantar  artery  had, 
in  the  interior  of  the  phalanx,  a  satellite  venous  system.  These  two  able 
anatomists  committed  an  error. 

"  The  disposition  of  the  venous  apparatus  in  the  interior  of  the  phalanx 
is  absolutely  identical  with  that  of  the  arterial. 

"  The  satellite  radicular  venules  of  the  terminal  arteries  converge,  by 
forming  successive  anastomoses,  towards  the  semilunar  sinus,  into  which 
they  enter  by  the  anterior  interosseous  canals,  ascending  and  descending,  and 
by  which  the  emergent  arteries  from  the  semilunar  anastomosis  pass  out- 
wards. There  they  join  into  a  semicircular  canal,  the  satellite  of  that 
anastomosis,  which  is  continued  backwards  by  two  eiferent  veins  that  follow 
the  posterior  canals  of  the  semilunar  sinus,  emerge  by  the  plantar  foramina, 
pass  into  the  fissure  of  the  same  name,  ascend  within  the  basilar  process, 
lie  at  the  internal  face  of  the  cartilaginous  plate,  in  one  of  the  infractuosities 
with  which  it  is  sculptured,  and  concur  in  the  formation  of  the  deep  layer 
of  the  cartilaginous  plexus. 

"  Beside  these  veins  converging  towards  the  cartilaginous  plexus,  there  is 
a  small  number  of  divergent  ones  which  follow  the  track  of  the  arteries,  and 
pass  into  the  podophyllous  plexus  through  the  anterior  porosities  of  the 
phalanx. 

"  The  dissection  of  specimens  injected  by  the  veins  puts  this  arrangement 
of  the  venous  apparatus  in  the  interior  of  the  os  pedis  beyond  a  doubt. 

"  But  is  this  internal  venous  system  limited  to  the  group  of  vessels  which 
are  satellites  of  the  arteries,  or  is  it  not  rather  extended  over  a  vaster 
surface,  and  may  not  all  the  areolae  of  the  spongy  tissue  of  the  bone  be 
considered  as  a  dependency  of  it  ? 

"  This  way  of  viewing  it  would  seem  to  be  supported  by  the  result  of 
certain  injections,  in  which  the  material  introduced  by  the  neighbouring 
veins  has  filled  all  the  internal  spongiolse  of  the  bony  tissue ;  though  this 
was  probably  due  to  an  accident  in  the  operation,  and  it  is  presumable  that 
the  direct  passage  of  the  venous  injection  into  the  areola?  of  the  spongy 
tissue  arose  from  a  rupture  in  the  VASCular  walls.  If  the  tissue  of  the 
phalanx  formed  a  kind  of  diverticulum  for  the  venous  system,  as  the  opinion 
just  given  would  admit,  operations  performed  on  this  part  during  life,  when 
the  texture  of  the  bone  is  deeply  involved,  ought  to  be  followed  by  haB- 
morrhage  from  the  open  orifices  of  these  aerolaa — a  circumstance  which 
does  not  take  place. 

"  It  does  not  appear,  therefore,  that  there  is  in  the  structure  of  the  third 
phalanx  any  departure  from  the  general  plan  on  which  bones  are  constructed, 
and  we  think  that  its  internal  veinous  system  is  limited  to  the  vessels,  very 
numerous  as  they  are,  which  accompany  the  arterial  divisions." 


TEE  POSTERIOR  VENA  CAVA.  617 

ARTICLE  III.— PosTERiOK  Vena  Cava.     (Figs.  258,  v;  259,/;  293.) 

This  vein,  whose  volume  is  uot  equalled  by  that  of  any  other  vessel  in 
the  body,  commences  at  the  entrance  to  the  pelvis  by  two  large  roots,  the 
pclvi-crural  trunks. 

From  this  point  it  is  directed  forward,  beneath  the  bodies  of  the  lumbar 
vertebrae,  soon  reaches  the  superior  border  of  the  liver,  where  it  leaves  the 
lumbar  region  to  lodge  itself  in  the  fissure  excavated  on  the  anterior  face 
of  that  gland  ;  passing  through  this,  it  traverses  the  aponeurotic  centre  of 
the  diaphragm,  and  opens  into  the  postero-external  part  of  the  right  auricle 
of  the  heart. 

In  this  course,  the  posterior  vena  cava  is  naturally  divided  into  three 
portions — a  suhlumbar,  hepatic,  and  thoracic. 

The  suhlumbar  portion,  placed  to  the  right  of  the  abdominal  aorta  and  to 
the  left  of  the  right  kidney  and  suprarenal  capsule,  is  maintained  against 
the  common  inferior  vertebral  ligament  and  the  left  small  psoas  muscle  by 
the  peritoneum  and  the  pancreas.  It  responds,  besides,  to  the  right  renal 
artery,  which  crosses  its  face  perpendicularly,  as  well  as  the  corresponding 
great  splanchnic  nerve  and  the  nervous  divisions  of  the  right  renal  and 
iumbo-aortic  plexuses. 

In  its  hepatic  portion,  the  posterior  vena  cava  is  only  related  to  the  liver 
and  diaphragm,  wiiich  form  a  comj^lete  canal  around  it. 

The  thoracic  portion  is  lodged  between  the  right  lung  and  its  internal 
accessory  lobule,  and  enveloped  by  a  particular  serous  fold— a  dependency 
from  the  right  j^leura,  and  which  has  been  already  described  (page  465)w 

Collateral  afferents. — Those  vessels  which,  as  considerable  as  they  are 
numerous,  open  into  the  posterior  vena  cava,  are,  enumerating  them  from 
before  to  behind : 

1.  The  diaphragmatic  veins. 

2.  The  vena  portce,  a  trunk  into  which  are  collected  the  majority  of  the 
visceral  abdominal  veins,  and  which,  instead  of  opening  directly  into  the 
vena  cava,  is  divided  in  the  liver  like  an  artery,  reconstituting  itself 
into  a  certain  number  of  thick  branches — the  suprahepatic  vessels,  which 
enter  the  vena  cava  on  its  way  through  the  anterior  fissure  of  the  liver. 

3.  Renal  veins. 

4.  Spermatic  veins. 

5.  Lumbar  veins. 

All  these  vessels  will  be  studied,  in  the  order  above  indicated,  before  the 
roots  or  pelvi-crural  trunks  of  the  vena  cava. 

DIAPHRAGMATIC   VEINS, 

These  are  two,  sometimes  three,  enormous  vessels  lodged  in  the  texture  of 
the  aponeurotic  centre,  commencing  by  several  branches  in  the  fleshy  jjortion 
of  the  muscle,  and  entering  the  vena  cava  at  the  moment  when  it  traverses 
the  diaphragm. 

VENA  POET^.     (Figs.  293  ;  294.) 

The  manner  in  which  this  vessel  comports  itself  gives  it  an  altogether 
peculiar  physiognomy,  and  has  caused  it  to  be  considered  as  a  separate 
vascular  system.  After  what  has  been  already  said  concerning  the  structure 
of  the  liver,  it  cannot  be  ignored  that  the  vena  portae  is  distributed  in 
that  gland  exactly  like  an  artery. 


618 


TEE  VE1^S. 

Fig.  293. 


GENERAL   VIEW    OF   THE    VEINS   IN   THE    HORSE. 


THE  POSTEBIOR  VENA  CAVA.  619 

It  begins  in  the  sublumbar  region,  at  the  great  mcsenteiic  artery,  by  tho 
union  of  three  large  roots ;  it  is  then  directed  forwards  and  a  little  to  the 
right,  traversing  the  pancreatic  ring,  below  the  vena  cava,  and  is  afterwards 
lodged  in  the  great  posterior  fissure  of  the  liver,  where  it  ramifies  by  forming 
the  subhepatic  veins,  whose  capillary  divisions  themselves  give  rise  to  the 
sujjrahepatic  vessels. 

Sujprahepaiic  and  subhepatic  veins  (Fig.  219,  VP,  V^). — These  vessels 
having  been  already  studied  in  the  description  of  the  liver,  we  need  not 
again  occupy  ourselves  with  them,  but  refer  t)nly  to  a  peculiarity  incompletely 
noticed  in  that  description,  with  reference  to  the  suprahepatic  veins. 

We  know  that  these  vessels  are  divided  into  two  categories,  according  to 
the  arrangement  of  their  openings.  The  majority  enter  the  vena  cava  in 
forming  a  single  confluent  placed  at  the  anterior  extremity  of  the  fissure  in 
the  liver,  at  the  diaphragmatic  veins  ;  the  others  open  separately  over  the 
whole  extent  of  the  hepatic  portion  of  the  venous  trunk.  In  carefully 
examining  the  confluent  towards  which  all  the  veins  of  the  first  group 
converge,  we  recognise  the  embouchures  of  three  principal  veins,  one  coming 
from  each  of  the  hej^atic  lobes,  and  furnished  with  three  very  thick,  incom- 
plete valves.  With  regard  to  the  vessels  of  the  second  group,  M.  Claude 
Bernard  ^  considers  them  to  come,  for  the  most  part,  directly  from  the  sub- 
hepatic veins,  and  not  from  the  capillary  network  formed  by  the  arborisation 
of  these  veins  in  the  lobules  of  the  liver.  It  is  true  that  injections  readily 
penetrate  from  the  vena  portaa  into  the  vena  cava,  but  they  do  this  quite  as 
much  by  passing  along  the  large  suprahepatic  vessels  as  the  canals  of  which 
we  now  speak ;  and,  besides,  if  the  material  forced  into  the  vena  portae  is 
mixed  with  some  imperfectly-powdered  colouring  matter,  the  injection  will 
arrive  colourless,  or  but  slightly  tinged,  in  the  suprahepatic  vessels  and  the 
vena  cava.     These  facts,  we  see,  do  not  militate  in  favour  of  M.  Bernard's 

*  Lemons  de  Physiolojic  Expertmentale.'    Paris,  1856. 


Anterior  vena  cava;  2,  2,  Posterior  vena  cava;  3,  Right  pelvi-crural  trunk, 
divided  at  tlie  ilio-sacra)  articulation ;  4,  Lett  pelvi-crural  trunk  ;  5,  Femoral 
veiu ;  6,  Obturator  vein ;  7,  Subsacral  vein  ;  8,  Left  testicular  vein ;  9,  Puste- 
rior  abdominal  vein;  10,  Renal  vein;  11,  11,  Ascending  branches  of  the  asternal 
vein;  12,  Vena  azygos,  with  its  intercostal  branches,  and  in  front  the  subdorsal 
venous  branch,  13;  14,  (Esophageal  vein;  15,  Dorsal,  or  dorso-muscular  vein; 
16,  Cervical,  or  cervico-muscular  veiu;  17,  Vertebral  vein;  18,  Right  axillary 
vein,  cut  at  the  anterior  border  of  the  first  rib;  19,  Substernal,  or  internal 
mammary  vein  ;  20,  Left  axillary  artery ;  21,  Termination  of  the  left  cephalic 
vein;  22,  Left  jugular,  23,  Right  jugular;  24,  External  maxillary,  or  glosso- 
facial  vein ;  25,  Coronary  vein ;  26,  Angular  vein  of  the  eye ;  27,  Subzygomatic 
vein ;  28,  Posterior  auricular  vein  ;  29,  Maxillo-muscular  vein ;  30,  Internal 
metacarpal  vein  ;  31,  Median  subcutaneous  vein ;  32,  Radial  subcutaneous  vein ; 
33,  Posterior  radial  vein;  34,  Basilic  vein;  35,  Plat,  or  cephalic  vein;  36, 
Coronary  venous  plexus ,  37,  Digital  vein ;  38,  Internal  metatarsal  vein ;  39, 
Anterior  root  of  the  internal  saphena  vein ;  40,  Posterior  root  of  ditto ;  41, 
Internal  saphena;  42,  Great  coronary  vein;  43,  Small  mesaraic  vein;  44,  Dif- 
ferent branches  of  the  great  mesaraic  vein ;  45,  Trunk  of  the  vena  porta:  in  its 
sublumbar  portion,  lodged  in  the  pancreas ;  46,  The  same  in  the  posterior  fissure 
of  the  liver ;  below  it  is  seen  entering  the  substance  of  the  gland. — M,  Sub- 
scapular hyoideus  muscle  cut  obliquely  in  the  direction  of  the  trachea ;  P,  Cervical 
panniculus  turned  down  to  expose  the  jugular  channel ;  0,  Right  auricle  of  the 
heart ;  A,  Posterior  aorta ;  G,  Section  of  the  right  lung ;  F,  Left  lobe  of  the  liver 
behind  the  section  of  the  diaphragm;  R,  Right  kidney  carried  up  and  forward; 
L,  CEsophagus ;  v,  Bladder;  s,  Rectum;  T,  Thoracic  duct;  t',  Termination  of 
that  duct  in  the  confiuent  of  the  jugulars. 


620 


TEE  VEINS. 


opinion  ;  and  there  is  every  reason  to  believe  that  the  system  of  the  vena  portte 
and  that  of  the  vena  cava  do  not  communicate,  in  the  adult,  otherwise  than 
p;^  294  l^y   *^®    capillary   network  which    is 

intermediate  to  the  subhepatic  and 
suprahepatic  vessels.  If  any  other 
means  of  communication  exist,  they 
must  be  extremely  small. 

Constituent  vessels  of  the  vena  portce. 
— The  three  roots  of  this  vein  are  the 
great  and  small  mesenteries  and  the 
splenic  vein. 

The  collateral  affluents  it  re- 
ceives on  its  course  are  principally 
two  :  the  right  gastro-epiploic  veins  and 
anterior  gastric. 

We  will  make  a  rapid  survey  of 
all  these  vessels. 

1.  Boots  of  the  Vena  Portce. 

A.  Great  Mesenteric  or  An- 
terior Mesaraic  Vein  (Fig.  293, 
44 ;  294,  2,  7). — This  is  an  enormous 
venous  canal  into  which  flows  the 
blood  that  has  passed  through  the 
walls  of  the  small  intestine,  csecum, 
large  colon,  and  the  origin  of  the  small 
colon,  and  whose  divisions  correspond 
exactly  to  the  diflerent  branches  fur- 
nished by  the  great  mesenteric 
artery. 

When  traced  from  its  opening  to 
its  origin,  in  an  inverse  direction  to 
the  course  of  the  blood,  it  is  observed 
to  lie  between  the  two  colic  arteries, 
and  proceed  beyond  the  fold  formed 
by  the  suprasternal  and  diaphragmatic 
curvatures,  beyond  which  it  divides 
into  two  satellite  branches  for  the 
colic  arteries,  which  anastomose  in 
arcade  towards  the  pelvic  curvature, 
like  the  arteries  they  accompany. 

It  is  therefore  by  the  union  of  two 
colic  veins  (Fig.  294,  8,  9)  that  the 
great  mesaraic  vein  is  constituted,  and 
in  whose  formation  numerous  collateral 
affluents  concur ;  among  these  may  be 
noticed  the  two  ccecal  veins  (Fig.  294, 
5,  6),  the  ilio-ccecal  vein  (Fig,  294,  4) 
coming  from  the  origin  of  the  floating 
colon,  and  the  veins  of  the  small  intes- 
tine :  vessels  arranged  so  exactly  like 
the  corresponding  arteries  that  we  may 
of  them. 


THE   VENA   PORT^   AND   ITS  ROOTS;   PARTLY 
THEORETICAL. 

1,  Trunk  of  the  vena  portse ;  2,  Its  origin ; 
3,  Veins  of  the  small  intestine;  4,  llio- 
caecal  vein  ;  5,  External  cajcal  vein  ;  6,  In- 
ternal caecal  vein  ;  7,  Great  mesaraic  veiii ; 
8,  9,  Colic  veins  forming  the  roots  of  that 
vessel ;  10,  Collateral  vein  sometimes  con- 
tinuing the  left  colic,  and  joining  the  great 
mesaraic  vein  near  its  origin;  11,  Com- 
mon confluent  of  the  small  mesaraic  and 
splenic  veins  ;  12,  Small  mesaraic  vein  and 
its  collateral  branches  ;  13,  Splenic  vein  ; 
14,  Left  gastro-epiploic  vein;  15,  Eight 
ditto  ;  16,  Posterior  gastric  vein. — a, 
Stomach ;  b,  Duodenum  ;  c,  Small  intes- 
tine ;  d,  Caecum ;  e,  Large  colon ;  /,  Float- 
ing colon ;  g,  Rectum  ;  h,  Portion  of  the 
great  omentum  ;  i.  Spleen ;  _;",  Mesentery  ; 
k,  Colic  mesentery. 

dispense  with  any  further  description 


THE  FOSTERIOR  VENA  CAVA.  621 

B.  Small  Mesenteric  or  Posteuioii  Mesaraic  Veik  (Figs.  293,  43  • 
294,  12). — This  vessel  commences  above  the  rectum,  near  the  anus  by- 
large  luemorrhoidal  branches  which  communicate  with  the  homonymous 
ramuscles  of  the  internal  pudic.  It  is  directed  forwards,  between  the  two 
layers  of  the  second  mesentery,  along  the  small  mesenteric  artery,  which  it 
passes,  and  extends  to  the  great  mesenteric  artery,  on  the  left  side  of  which 
It  unites  with  the  splenic  vein,  before  opening  into  the  anterior  mesaraic  to 
form  the  vena  portte.  In  its  course  it  receives  all  the  satellite  venous 
branches  of  the  divisions  of  the  artery  of  the  same  name,  and  whose 
arrangement  is  similar  to  that  of  the  arterial  ramifications. 

C.  Splenic  Vein  (Fig.  294,  13).— This  is  an  enormous  canal  which 
follows  the  splenic  artery,  and  comports  itself  exactly  like  it.  It  begins  by 
the  left  gastro- epiploic  vein  (Fig.  294,  14)  anastomosing  in  arcade  with  the 
right  gastro-epiploic,  receiving  on  its  track  gastric,  splenic,  and  epiploic 
branches,  and  joining  the  small  mesaraic  after  passing  above  the  left  ex- 
tremity of  the  pancreas,  and  obtaining  the  posterior  gastric  vein  (Fig.  294,  16). 

2.  Collateral  Affluents  of  the  Vena  Portce. 

A.  Right  Gastro-epiploic  Vein  (Fig.  294,  15). — We  already  know  that 
the  heiJatic  artery,  before  entering  the  liver,  gives  off  pancreatic  branches,  a 
pyloric  branch,  and  a  gastro-epiploic  division,  which  in  turn  detaches  a  small 
duodenal  artery ;  the  vessel  described  as  the  right  gastro-epiploic  vein  cor- 
responds, in  every  respect,  to  all  these  collateral  ramifications  of  the  hepatic 
artery. 

This  vein,  then,  has  its  origin  from  around  the  great  curvature  of  the 
stomach,  but  at  an  undetermined  point,  as  it  forms  an  anastomotic  arch  with 
the  left  gastro-epiploic  vein.  Posteriorly,  it  crosses  the  dilatation  at  the 
origin  of  the  duodenum,  receives  the  pyloric,  duodenal,  and  pancreatic  vtins, 
and  opens  into  the  vena  porta?  after  traversing  tlie  pancreas. 

B.  Anterior  Gastric  Vein.  —  Satellite  of  the  homonymous  artery, 
this  vein  joins  the  vena  portfe  separately,  after  the  entrance  of  that  vessel 
into  the  great  posterior  fissure  of  the  liver,  and  when  very  near  the  terminal 
extremity  of  that  fissure. 

renal  veins. 

Two  in  number,  like  the  arteries  they  accompany,  these  veins  are  dis- 
tinguished by  their  enormous  volume  and  the  tenuity  of  their  walls.  The 
left,  having  to  cross  the  abdominal  aorta  before  entering  the  vena  cava,  is 
longer  than  the  right.  They  receive  the  majority  of  the  veins  from  the 
suprarenal  capsules  (293,  10). 

SPER5IATIC    VEINS. 

These  vessels  correspond  to  the  great  spermatic  arteries  of  the  male,  and 
the  utero-ovarian  arteries  of  the  female. 

Testicular  vein. — The  radicles  which  constitute  this  vein  present,  at  their 
emergence  from  the  superior  border  of  the  testicle,  a  flexiform  and  very 
complicated  arrangement,  enlacing,  turning,  and  inflecting  themselves  in  a 
thousand  ways  around  the  convolutions  of  the  great  spermatic  artery,  and 
ascending  in  this  manner  towards  the  neck  of  the  vaginal  sheath  (abdominal 
ring),  which  they  jiass  through  usually  after  joining  to  form  two  trunks. 
These  rise  towards  the  sublumbar  region,  beneath  the  peritoneum,  in  a  fold 
of  which  they  are  at  first  included ;  they  communicate  with  one  another  in 


622  THE  VEINS. 

tlieir  course  by  anastomosing  branches,  and  are  generally  confounded  into  a 
single  spermatic  vein,  whicb  opens  into  the  vena  cava  near  the  renal  vein 
(Fig.  293,  8). 

Utero-ovarian  vein. — This  vein,  which  is  very  voluminous,  enters  the 
vena  cava  at  the  same  point  as  the  corresponding  vessel  in  the  male,  and 
proceeds,  as  its  name  indicates,  from  the  ovaries  and  uterus  by  flexuous  and 
reticular  branches,  whose  fusion  into  a  single  trunk  only  takes  place  near 
the  vena  cava. 

LUMBAR    VEINS. 

Satellites  of  the  arteries  of  the  same  name,  these  vessels  enter  the  vena 
cava  separately.     The  most  anterior  often  open  into  the  vena  azygos. 

PELVI-CRUKAL   TRUNKS    OR    COMMON    ILIAC    VEINS. 

These  appellations  are  given  to  two  enormous  vessels,  into  which  are  col- 
lected all  the  veins  of  the  abdominal  limb  and  the  posterior  part  of  the 
trunk — very  short  vessels,  which,  by  their  junction,  form  the  posterior  vena 
cava  (Fig.  293,  3,  4).      _     _ 

The  common  iliac  vein  is  lodged  in  the  angle  of  separation  comprised 
between  the  external  and  internal  iliac  arteries,  and  is  a  continuation  of 
the  two  satellite  veins  of  these  arterial  canals.  The  right,  shorter  than  the 
other,  passes  above  the  external  iliac  artery  to  join  the  vena  cava  at  its 
origin.  The  left,  longer,  insinuates  itself  between  the  body  of  the  second 
last  lumbar  vertebra  and  the  terminal  extremity  of  the  posterior  aorta,  to 
open  into  the  other. 

If  we  trace,  as  was  done  with  the  veins  of  the  anterior  extremity,  from 
the  ungueal  region  to  the  pelvis,  all  the  branches  which  concur  in  the 
formation  of  these  two  trunks,  we  will  find,  as  the  common  point  of  de- 
jjarture  for  each,  a  rich  siibungueal  plexus,  from  which  spring  two  digital 
veins.  To  these  succeed  three  metatarsal  veins,  the  common  origin  of  all  the 
vessels  of  the  leg.  These  latter  are  distinguished  as  superficial  and  deep, 
and  are  four  in  number — two  saphena  veins  in  the  first  group,  and  tico  tibial 
veins  in  the  second — continued  by  the  popliteal  vein.  This  vessel  is  itself 
continued  by  the  femoral  and  external  iliac  veins,  which  finally  form  the 
pelvi- crural  trunk  by  opening  into  the  internal  iliac  vein. 

All  these  vessels  will  be  studied  in  an  inverse  order  to  that  in  which  they 
have  been  enumerated,  and  as  follows : 

1.  Internal  iliac  vein. 

2  External  iliac  vein. 

3.  Femoral  vein. 

4.  Popliteal  vein. 

5.  Dee])  veins  of  the  leg. 

6.  Superficial  veins  of  the  leg. 

7.  Metatarsal  veins. 

8.  Veins  of  the  digital  region. 

1.  Internal  Iliac  Vein. 

This  vessel  is  formed  by  the  satellite  veins  of  the  branches  furnished 
by  the  homonymous  artery :  these  are  the  iliaco-femoral,  obturator,  iliaco- 
muscular,  gluteal,  lateral  sacral,  and  internal  pudic,  whose  distribution  does 
not  differ  from  that  of  the  corresponding  arterial  divisions. 


TEE  POSTERIOR  VESA  CAVA.  623 

The  trunk  resulting  from  the  union  of  these  different  branches  is  usually- 
very  short ;  it  may  even  be  altogether  absent,  and  we  then  see  its  con- 
stituent veins  open  into  the  common  iliac  vein  by  forming  two  or  three 
separate  groups  situated  very  close  to  each  other. 

2.  External  Iliac  Vein. 

This  vein  constitutes  the  principal  root  of  the  pclvi-crural  trunk,  which 
is  but  a  continuation  of  it,  the  internal  iliac  being  only,  properly  speaking, 
a  collateral  affluent  of  the  single  canal  represented  by  the  external  and 
common  iliac  veins. 

Situated  behind  the  crural  arterial  trunk,  this  external  iliac  vein  com- 
mences at  the  anterior  border  of  the  pubis,  where  it  is  directly  continued, 
without  any  line  of  demarcation,  by  the  femoral  vein. 

The  only  important  vessel  it  receives  on  its  course  is  the  iliac  circumflex 
vein,  which,  however,  opens  more  frequently  into  the  common  than  the 
external  iliac. 

3.  Femoral  Vein. 

Continuous  by  its  superior  extremity  with  the  external  iliac  vein,  and 
inferiorly  with  the  popliteal,  this  femoral  vein  is  remarkable  for  its  large 
volume,  and  closely  follows  the  artery  of  the  same  name  throughout  its 
extent  (Fig.  293,  5). 

The  collateral  affluents  it  receives  in  its  course  are  distinguished  by 
their  number  aud  considerable  volume.     They  are  : — 

1.  The  satellite  veins  of  the  muscular  arteries. 

2.  The  internal  saphena  vein,  which  will  be  again  referred  to  in  describing 
the  superficial  veins  of  the  leg. 

3.  The  prepubic  vein,  formed  by  i\ie posterior  abdominal  and  the  branches 
of  the  internal  pudic.  The  latter  are  very  numerous  and  large,  and  anas- 
tomose with  each  other,  forming  between  the  thighs,  in  the  texture  of  the 
scrotum  and  sheath,  and  above  the  penis,  a  very  rich  network  which  com- 
municates behind  with  the  cavernous  veins.  This  network  only  sends  a 
small  trunk  into  the  inguinal  ring,  along  the  external  pudic  artery ;  in  its 
middle  part  it  opens  into  an  enormous  branch  which  traverses  the  ring  in 
the  sartorius  muscle,  and  is  lodged  in  the  inferior  groove  of  the  pubis  to 
join  the  femoral  vein. 

One  of  these  external  pudic  veins  represents  the  subcutaneous  abdominal 
vein,  and  communicates  with  the  subcutaneous  thoracic  vessel. 

All  these  branches  in  the  female  show  an  analogous  disposition, 

4.  Popliteal  Vein. 

Satellite  of  the  popliteal  artery,  this  vein  is  formed  by  the  union  of  the 
anterior  and  posterior  tibial  veins. 

Among  the  branches  it  receives  on  its  course,  the  femoro-popl ileal  vein 
may  be  particularly  noted ;  this  accompanies  the  artery  of  the  same  name, 
and  joins  the  external  saphena  before  opening  into  the  popliteal  vein. 

5.  Deej)  Veins  of  the  Leg. 

These  are  two  in  number  :  the  anterior  and  posterior  tibial. 
A.  Anterior    Tibial  Vein  (Fig.  278,  5).— Placed   beside    the    homo- 
nymous artery,  often  double,  always  very  ample,  this  vein  originates  on  the 


624  THE  VEINS. 

anterior  face  of  the  tarsal  articulations  by  means  of  several  anastomosing 
roots,  the  principal  of  which  is  formed  by  the  deep  metatarsal  vein,  that 
passes  through  the  cuboido-cuneo-scaphoid  canal  from  behind  to  before. 
After  crossing  the  fibular  arch  with  the  artery,  it  joins  the  posterior  tibial 
to  constitute  the  popliteal  vein. 

B.  Posterior  Tibial  Vein. — This  commences  near  the  hollow  of  the 
hock,  within  the  calcis,  by  radicular  branches  which  principally  come  from 
the  two  saphena  veins.  It  then  ascends  along  its  satellite  artery,  to  open 
into  the  anterior  vein  beneath  the  j)opliteal  muscle. 

6.  Superficial  Veins  of  the  Leg. 

These  are  the  internal  and  external  saphena. 

A.  Internal  Saphena  Vein. — This  vessel  shows  two  roots — an  anterior 
and  posterior  (Fig.  293,  39,  40). 

The  first  proceeds  from  the  internal  metatarsal  vein,  the  second  from  the 
external.  Both  ascend,  in  converging  towards  each  other,  on  the  internal 
face  of  the  tibia,  uniting  into  a  single  branch  before  reaching  the  thigh. 

This  single  branch,  always  very  voluminous,  glides  upwards  on  the 
sartorius  muscle,  and  terminates  in  a  variable  manner  on  reaching  the  groin : 
sometimes  it  is  insinuated  into  the  interstice  of  the  two  adductors  of  the 
leg,  to  join  the  femoral  vein,  and  at  other  times  it  ascends  to  the  ring  of  the 
short  adductor,  and  opens  into  the  external  j^udic  veins. 

B.  External  Saphena  Vein. — It  rises,  by  a  short  branch,  outside  the 
OS  calcis,  communicates,  even  at  its  origin,  with  the  posterior  root  of  the 
internal  saphena  by  means  of  a  large  reticular  anastomosis  thrown  trans- 
versely in  front  of  the  apex  of  the  calcis  ;  and  with  the  posterior  tibial,  by  a 
large  branch  which  passes  between  the  tibia  and  the  perforans  muscle.  It 
follows  the  external  saphena  nerve  outside  the  gastrocnemii  tendons,  behind 
the  external  gastrocnemius  muscle,  and  enters  the  popliteal  vein,  after 
joining  the  femoro-popliteal  vessel. 

7.  Metatarsal  Veins. 

These  veins  arc  three  in  number,  and  are  distinguished  as  internal, 
external,  and  deep ;  they  proceed  from  the  sesamoid  arch,  which  is  formed 
by  the  anastomosis  of  the  two  digital  veins. 

A.  Internal  Metatarsal  Vein  (Fig.  278,  9). — This  vessel,  the  most 
considerable  of  the  three,  appears  more  particularly  to  continue  the  digital 
vein  of  the  same  side.  For  the  greater  part  of  its  extent  it  is  placed  with 
the  internal  plantar  nerve,  along,  and  a  little  in  advance  of,  the  flexor 
tendons.  Arriving  near  the  tarsus,  it  deviates  slightly  to  reach  the  anterior 
face  of  the  tarsal  articulations,  and  there  communicates,  by  a  very  large 
transverse  branch,  with  the  origin  of  the  anterior  tibial  vein  ;  afterwards  it 
rises  on  the  internal  face  of  the  leg,  where  it  constitutes  the  anterior  root  of 
the  internal  saphena  vein. 

B.  External  Metatarsal  Vein  (Fig.  278,  8). — It  occupies,  outside 
the  flexor  tendons,  a  position  analogous  to  the  preceding.  Towards  the 
superior  extremity  of  the  metatarsus,  it  communicates,  by  a  short  thick 
branch,  with  the  deep  vein.  It  then  continues  its  ascending  course  by 
entering  the  tarsal  sheath  along  with  the  plantar  arteries,  and  is  prolonged 
in  the  hollow  of  the  hock,  along  the  great  femoro-popliteal  nerve,  in  con- 
stituting the  posterior  root  of  the  internal  saphena. 

C.  Deep   Metatarsal  Vein  (Fig.  278,  10).— This  is  placed   beneath 


THE  POSTERIOR  VENA  CAVA.  625 

the  suspensory  ligament,  at  the  inner  side  of  the  principal  interosseous 
plantar  artery.  Near  the  tarsus,  it  receives  a  very  large  branch  from  the 
external  vein,  and  then  traverses  the  cuboido-cuueo-scaphoid  canal,  tu  form 
the  largest  root  of  the  anterior  tibial  vein. 

8.  Veins  of  the  Digital  Megion. 

As  these  resemble,  in  every  respect,  those  belonging  to  the  anterior 
limb,  the  same  description  will  suffice  for  both  (see  page  613). 

DIFFERENTIAL   CHARACTERS   IK   THE   VEINS   OF   OTHER   THAN   SOLIPED   ANIMALS. 

It  does  not  come  within  our  plan  to  give  a  complete  history  of  the  venous  system  of 
these  animals,  because  of  the  small  utihty  of  such  a  study.  To  remain  faithful  to  the 
object  in  view,  we  confine  ourselves  to  tlie  indication  of  tlie  special  characters  of  the 
veins  on  which  bleeding  is  usually  practised,  and  those  which  may  be  interesting  in  a 
surgical  point  of  view,  as  the  digital  veins  of  Ruminants. 

A.  Angular  Vein  of  the  Eye. — This  vessel  is  remarkable  for  its  large  volume  in 
the  Sheep ;  and  as  it  is  well  defined  beneath  the  skin,  in  consequence  of  the  fineness  of 
that  membrane,  it  is  more  frequently  selected  for  phlebotomy  than  in  other  animals. 

B.  Jugular  Vein. — Very  large  m  all  animals,  and  particularly  in  the  Ox,  this  vein 
deserves  tiie  preference  given  to  it  when  it  is  proposed  to  abstract  a  certain  quantity  of 
blood  from  tlie  system. 

In  all  non-soiiped  animals  there  is  found  an  accessory  jugular,  which  sometimes  exists 
in  the  Horse,  but  is  much  less  in  size,  alongside  the  common  carotid  artery.  It  arises 
from  the  occipital  vein,  and,  therefore,  measures  the  whole  length  of  the  neck.  Sometimes 
its  diameter  is  small ;  but  it  is  often  so  large  as  to  receive  a  very  notable  quantity  of 
blood  from  the  principal  jugular,  when  compression  is  applied  to  the  latter  to  favour  the 
flow  of  blood  after  opening  it :  a  circumstance  which  explains  the  difficulty  sometimes 
experienced  in  obtaining  a  voluminous  jet  of  blood. 

C.  Abdominal  Subcutaneous  Vein. — In  the  Bovine  species,  this  vessel  has  an 
enormous  volume,  especially  in  the  milch-cow,  in  contradistinction  to  the  subcutaneous 
thoracic  vein,  which  is  always  very  narrow. 

This  vein  is  prolonged  forward  on  the  wall  of  the  abdomen,  to  nearly  the  xiphoid 
cartilage,  where  it  passes  through  to  join  the  internal  thoracic  vein.'  Behind,  it  is 
formed  by  multiple  branches,  which  anastomose  with  each  other,  or  with  tho^e  of  tue 
opposite  vein,  and  are  in  communication  with  the  proper  external  pudic  veins. 

D.  Internal  Saphena  Vein. — This  is  alway  smaller  than  in  Solipeds,  and  is  rarely 
selected  to  bleed  from. 

E.  External  Saphena  Vein. — This  vessel  is,  on  the  contrary,  more  voluminous  than 
in  the  Horse,  and  at  the  same  time  more  superficial ;  consequently,  it  is  more  favourably 
situated  for  phlebotomy,  as  well  in  Pigs  and  the  Carnivora,  as  in  Ruminants.  It  arises 
from  the  union,  in  the  hollow  of  the  hock,  of  the  two  principal  roots  furnished  by  the 
metatarsal  veins. 

F.  Veins  of  the  Posterior  Foot  in  the  Ox. — As  in  the  Horse,  they  commence  in 
the  subungueal  nehvork  of  the  digital  region,  which  is  double,  like  the  region  itself. 

a.  Three  digital  veins  leave  this  reticulum  :  1,  A  median  or  anterior  one,  arising  by 
two  roots  from  the  anterior  part  of  each  network,  passing  between  the  two  digit.-,  and 
joining  the  anterior  superficial  metatarsal  vein  above  the  fetlock  ;  2,  Two  laterals,  com- 
municating with  one  another,  behind,  by  a  transverse  anastomosis  which  receives  several 
venules  from  the  ungueal  plexus,  and  with  the  anterior  vein  by  an  interdigital  branch, 
united  by  an  arch  in  front  of  the  flexor  tendons,  above  the  sesamoid  groove. 

b.  These  digital  veins  are  continued  by  five  metatarsal  veins :  two  deep  and  one 
superficial  anterior,  and  two  posterior. 

The  two  deep  anterior  veins  are  small  vessels  which  accompany  the  collateral  artery 
of  the  cannon,  which  is  placed  between  them.  They  arise  in  the  interdigital  space  from 
the  anterior  digital  vein,  communicating,  by  the  inferior  metatarsal  foramen,  with  the 
sesamoid  arch,  sending  off  on  their  way  transverse  anastomoses,  and  being  continued 
above  the  tarsus  by  the  two  anterior  tibial  veins,  whose  roots  they  constitute. 

The  anterior  superficial  vein  is  very  voluminous.    It  proceeds  from  the  sesamoid  arch, 


1  The  openings  through  which  these  vessels  pass  in  the  abdominal  parietes,  are 
commonly  named  the  milk  fountains  or  doors. 


626  THE  VEINS. 

receives  near  its  origin  the  median  digital  vein,  rises  in  front  of,  and  a  little  to  the 
outsido  of,  the  tarsus,  communicating  at  this  point  with  the  anterior  tibial  veins;  it 
divides  above  the  tibio-tarsal  articulation  into  two  branches :  a  posterior,  forming  the 
anterior  root  of  the  external  sapiieua  ;  the  other  anterior,  joining  tlie  anterior  tibial  vein 
of  the  external  side. 

The  two  posterior  veins  spring  from  the  sesamoid  arch.  Situated  at  first  between  the 
suspensory  ligament  of  the  fetlock  and  the  posterior  face  of  the  metatarsus,  and  com- 
municating there  by  several  anastomoses,  these  two  veins  are  continued  along  the  tarsus, 
the  one  within,  the  other  without.  Tlie  interned  follows  the  corresponding  plantar  artery, 
and  is  prolonged  in  the  tibial  region  by  the  posterior  tibial  and  internal  saphena  veins. 
The  external  ascends  witbin  the  calcis,  and  is  united  to  a  branch  of  the  anterior  super- 
ficial metatarsal,  to  form  the  exttrual  saphena  vein.  Before  leaving  the  deep  situation 
it  occupies  below  the  suspensory  ligament  of  the  fetlock,  these  two  vessels  concur,  but 
especially  the  internal,  to  furm  a  perforating  branch  which  traverses  the  cuboido-scaphoid 
canal  to  join  the  anterior  tibial  veins. 

G.  Veins  of  the  Anterior  Foot  in  the  Ox. — Four  digital  reins  escape  from  the 
two  subuno'ueal  plexuses:  an  anterior,  jmsterior,  and  two  lateral. 

a.  Tlie  anterior  digital  vein,  which  is  very  slender,  is  lodged  superficially  between  the 
two  digits,  and  comports  itself  at  its  origin  like  the  analogous  vein  of  the  posterior 
limb,  in  rising  by  two  roots.  In  being  prolonged  above  the  fetlock,  it  constitutes  a 
subcutaneous  metacarpal  branch,  whicli  occupies  the  anterior  and  internal  plane  of  the 
cannon,  and  is  united  above  the  knee  to  the  principal  cutaneous  vein  of  the  fore-arm. 

b.  The  posterior  digital  vein,  often  doubled  by  a  small  accessory  branch,  accompanies 
the  common  digital  artery,  and  extends  along  the  collateral  artery  of  the  cannon,  to 
constitute  one  of  the  posterior  radial  vcius. 

c.  The  internal  digital  vein,  after  passing  the  digital  region,  is  lodged  between  the 
cannon  bone  and  the  "internal  border  of  the  suspensory  ligament,  proceeds  outsido  the 
carpal  sheath  with  the  radio-palmar  artery,  and  divides  above  the  knee  into  two 
branches:  an  anterior,  the  origin  of  the  internal  subcutaneous  vein  of  the  fore-arm;  the 
otlier  posterior,  forming  one  of  the  posterior  radial  veins. 

d.  The  external  digital  vein  occupies,  on  the  outer  side  of  tlie  external  digit  and  the 
cannon  bone,  a  position  analogous  to  the  internal  vein.  It  gives  rise  to  several  deep 
metacarpal  veins  which  anastomose,  and  are  mi.ved  with  the  interosseous  palm;ir 
arteries;  the  principal  vein  and  its  accessory  branches  are  joined,  below  the  carpus,  to 
the  internal  vein. 

It  is  to  be  remarked  that  these  four  digital  veins  communicate,  in  the  interdigitnl 
space,  by  anastomoses  resembling  those  of  the  posterior  limb;  and  that  the  last  three, 
or  principal  veins,  anastomose  above  tiie  fetlock  in  forming  a  complicated  and  variably- 
arrano-ed  sesamoid  arch,  on  leaving  which  these  digital  veins  become  metacarpal  vessels. 

COMPARISON   OF   THE   VEINS   IN   MAN   WITH   THOSE   OF   ANIMALS. 

In  Man,  as  in  animals,  the  veins  are  grouped  into  those  of  the  lesser  circulation,  or 
pulmonary  veins,  and  those  of  the  greater  circulation.  The  latter  open  into  the  heart  by 
tiiree  trunks:  the  cardiac  veins,  and  superior  and  inferior  vena  cam. 

The  superior  vena  cava  represents  the  anterior  vena  cava  of  animals,  and  receives  the 
blood  from  the  veins  of  the  head,  thoracic  limbs,  and  a  portion  of  the  chest.  It  extends 
from  the  first  costal  cartilage  to  the  heart,  and  commences  after  the  junction  of  the  two 
braehio-cephalic  trunks  (innominate  veins). 

The  superficial  veins  of  the  thoracic  limb  at  first  form,  on  the  back  of  the  hand,  a 
plexus  of  elongated  meshes  from  which  the  median,  radial,  and  idnar  veins  spring.  Near 
the  bend  of  the  elbow,  the  median  bifurcates  and  gives  rise  to  the  median  cephalic  and 
median  basilic.  Blood  is  abstracted  from  one  or  other  of  these  branches.  At  the  arm, 
all  the  superficial  veins  constitute  but  two  trunks :  the  cephalic  and  basilic  veins.  The 
deep  vessels  join  these  to  form  the  axillary  vein,  which  becomes  the  subclavian  below  the 
clavicle,  then  the  braehio-cephalic  trunk  {vena  innominata)  when  it  receives  the  internal 
jugular 

The  venous  sinuses  of  the  cranial  dura  mater  are  proportionately  more  developed 
than  in  Solipeds,  tliough  they  have  the  same  disposition.  There  is  constantly  present  a 
median  or  inferior  longitudinal  sinus. 

The  jugulars  which  carry  the  blood  from  the  cranium  and  face  to  the  heai-t,  are  four 
in  number.  The  anterior  jngxdar,  the  smallest,  descends  beneath  the  superficial  cervical 
aponeurosis,  in  front  of  tlic  sterno-mastoideus  muscle,  and  enters  the  subclavian  vein. 
The  external  jugxdar  comiwewcei  by  the  union  of  the  facial  and  temporal  vein;  in  its 
disposition  it  resembles  the  jugular  of  the  Horse,  and  would  be  a  complete  representative 


GENERAL  CONSIDERATIONS.  627 

if  deprived  of  the  branches  from  the  cranial  sinuses.  The  infernal  jugular  arises  nt  the 
posterior  foramen  lacerum,  at  a  dilatation  of  the  lateral  sinus  mimed  the  hulbits  veme, 
jugularis,  and  passes  to  the  subclavian  vein.  Lastly,  the  posterior  jugular  (or  vertebral 
vein)  bituatud  beneath  tlie  great  coniplexus,  and  in  relation  with  the  cervical  vertebra;, 
curries  the  blood  from  the  spinal  sinuses  in  this  region,  and  which,  in  Solipeds,  is  received 
by  the  occipital  and  vertebral  veins. 

The  inferior  vena  cava  corresponds  to  the  posterior  vena  cava  of  animals,  and  receives 
the  blood  from  all  the  subdiaphragmatic  veins.  It  originates  from  the  union  of  the 
two  common  iliac  veins,  at  the  third  hunbar  articulation,  and  terminates  in  the  right 
auricle.  In  its  course  it  receives  the  median  sacral,  lumbar,  renal,  suprarenal,  inferior 
phrenic,  and  right  spermatic  veins.  The  latter  forms  on  the  surface  of  the  testicle,  and  at 
the  origin  of  the  cord,  a  rich  network — the  spermatic  plexus ;  on  the  abdominal  portion  of 
the  cord  it  constitutes  the  pampiniform  plexus. 

The  vena  cava  also  receives  the  vena  portx,  which  has  the  same  disposition  as  in 
animals.  It  begins  by  three  branches  :  the  great  and  small  mesaraic  and  splenic  reins. 
For  affluents,  it  has  the  pancreatic  and  duodenal  venides,  and  the  right  gastro-omental 
vein.     It  passes  behind  the  pancreas,  and  not  through  that  gland,  as  in  the  Horse. 

The  veins  of  the  abdominal  limb  are  divided  into  deep  and  superficial.  The  first 
terminate  by  forming  the  femoral  vein,  which,  in  joining  the  vessels  of  the  pelvis, 
constitutes  the  common  iliac  vein.  The  superficial  i^eins  commence  by  a  network  on 
the  dorsum  of  the  foot,  which  gives  origin  to  the  two  saphenas :  external  and  internal. 


FOURTH   SECTION. 
The  Lymphatics. 

CHAPTER  I. 

GENERAL   CONSIDERATIONS. 


Charged  with  the  absorption  and  transport  of  the  chyle  and  lymph,  the 
lymphaiic  or  absorbent  vessels  are  convergent  canals  with  thin  and  transparent 
walls,  which  originate  in  the  texture  of  organs  by  tine  reticulated  radiculae ; 
and  which,  after  traversing  one  or  more  ganglia  (or  glands) — glandiform 
bodies  placed  on  their  course — enter  the  venous  system  by  two  trunks  :  the 
thoracic  duct  and  the  great  lymphatic  vein. 

LYMPHATIC    VESSELS, 

These  canals  resemble  veins  in  so  many  points,  as  to  merit  the  name  of 
white-blood  veins.  Like  these  vessels,  the  lymphatics  are  directed  from  the 
periphery  to  the  centre  of  the  circulatory  apparatus ;  like  them,  they  are 
nodulated  cylindrical  tubes  ;  internally,  and  at  those  points  where  they 
outwardly  appear  to  be  constricted,  they  show  numerous  valves  which  look 
towards  the  heart ;  like  the  veins,  again,  they  separate  into  two  orders  of 
canals :  the  ones  deep-seated,  lodged  in  the  vasculo-nervous  intei'muscular 
sheaths ;  the  others  superficial,  situated  on  the  surface  of  containing  apon- 
euroses ;  like  the  veins,  also,  the  lymj^hatics  terminate  in  two  principal  trunks 
resembling  the  venae  cavse ;  and,  finally,  as  the  veins  have  three  tunics,  so 
have  the  lymphatics,  these  not  difiering  in  any  respect,  except  in  being  very 
much  thinner. 

In  carrying  this  parallel  still  farther,  we  will  find  other  analogies  whose 
existence  was  but  little  suspected  until  recently  :  the  glands — those  organs 
which  are  apparently  glandular,  and  seem  to  be  proper  to  the  lymphatic 
system — are  they  not   represented   in   the   venous   system  by  the   liver — 


628  TEE  LYMPHATICS. 

that  enormous  gland  placed  on  the  track  of  the  abdominal  veins — as  the 
glands  are  on  parts  of  the  lymphatics  ? 

It  may  be  added  that,  if  we  pass  into  the  domain  of  physiology,  it  is  also 
easy  to  observe  characters  which  are  common  to  the  two  anatomical  systems 
under  comparison.  They,  in  fact,  almost  equally  divide  the  absorbent 
function  between  them :  a  function  which  is  accomplished  in  the  radicular 
network  of  each  ;  and  the  dynamical  process  which  gives  impulsion  to  the 
fluids  they  carry,  if  it  is  not  quite  identical  in  both,  is  at  any  rate  very  similar 
in  many  points. 

We  may,  nevertheless,  observe  numerous  differences  between  the  veins  and 
the  lymphatics,  and  chiefly  in  their  form,  number,  capacity,  and  structure. 

The  form  of  the  lymphatic  canals  is,  as  we  have  said,  nodulated  and 
cylindrical ;  but  their  external  nodosities  are  much  less  marked,  and  are  closer 
together  than  in  the  veins,  owing  to  the  larger  number  and  greater  develop- 
ment of  the  valves.  Besides,  as  these  canals  travel  for  considerable  distances, 
and  preserve  thoir  regularly-cylindrical  form  with  undiminished  capacity, 
if  we  mentally  bring  all  the  divisions  of  the  lymphatic  system  to  a  single 
canal,  we  no  longer  obtain  a  hollow  cone  whose  apex  corresponds  with  the 
heart,  although  the  capacity  of  the  lymphatic  vessels  augments  from  the 
trunk  towards  the  branches;  this  conduit  only  represents  a  series  of 
cylinders  joined  end  to  end,  and  successively  decreasing  from  its  origin  to  its 
termination. 

The  number  of  lymphatic  vessels  in  a  certain  region  is  always  much 
greater  than  that  of  the  veins.  But  as  the  lymphatics  are  much  smaller 
than  the  veins,  there  is  not,  as  might  at  first  be  supposed,  a  proportional 
increase  in  their  total  capacity.  Observation,  indeed,  demonstrates  that  the 
relation  between  the  capacity  of  the  lymphatics,  and  the  corresponding  veins 
of  a  region  does  not  exceed  one  to  two. 

The  structure  of  the  lymphatics  differs  from  that  of  veins  in  that  there 
exists,  in  those  of  average  dimensions,  smooth  muscular  fibres  in  the  adven- 
titious tunic.  The  presence  of  muscular  fibres  in  the  external  tunic  of 
these  vessels  is  rendered  necessary  by  the  absence  of  an  impelling  organ  at 
the  origin  of  the  lymphatic  system  :  this  organ  being,  in  reality,  disseminated 
throughout  the  extent  of  the  canals,  and  aids  the  vis  a  tergo  that  causes  the 
lymph  to  circulate  in  their  interior. 

We  terminate  this  short  parallel,  to  d\^'cll  in  detail  on  several  points 
connected  with  the  general  history  of  the  lymphatics,  and  which  merit 
particular  attention ;  we  allude  to  the  origin,  course,  and  termination  of 
these  vessels. 

Obigin. — For  a  long  period  after  the  discovery  of  the  lymphatic  vessels,  a 
state  of  profound  ignorance  existed  as  to  their  origin.  Nevertheless,  the 
importance  of  the  solution  of  the  problem  was  well  appreciated,  as  it  was 
really  the  key  to  the  theory  of  absorption ;  numerous  hypotheses,  therefore, 
sprang  into  existence.  The  anatomists  who  occupied  themselves  with  the 
question  were  hindered  in  their  investigation  by  the  imperfect  means  of 
research  at  their  disposal.  Beyond  the  larger  branches,  the  lymphatics 
escaped  attention,  owing  to  their  transparency  and  tenuity.  Thanks,  how- 
ever, to  the  patient  and  minute  researches  of  Hunter,  Cruikshank,  Mascagni, 
Fohmann,  Panizza,  Cruveilhier,  and  Sappey,  the  lymphatics  were  injected  by 
colouring  matters  or  by  mercury,  and  thus  rendered  visible  to  their  finest 
ramifications. 

It  is  now  known  that  the  lymphatics  arise  from  capillaries,  which  form 
networks  or  terminal  cids-de-sac. 


GENERAL  CONSIDERATIONS.  629 

These  terminal  cids-de-sac  exist  in  the  intestinal  villi ;  and  it  is  no  longer 
maintained  that  the  ends  of  these  small  api)endices  have  an  opening  by 
which  the  lymphatic  receives  the  chyle  that  bathes  the  mucous  membrane  of 
the  intestine. 

The  plexuses  are  composed  of  more  or  less  irregular  meshes,  and  their 
form  and  volume  often  vary  with  the  disposition  of  the  tissues  or  organs  in 
which  they  are  studied.  They  may  be  superficial  or  deep,  and  exist  together 
or  separately.  In  many  membranes  the  two  networks  are  found,  but  then 
the  superficial  is  thinner  than  the  deep.  They  are  mixed  with,  or  placed 
above,  the  blood-vessel  plexuses,  but  never  communicate  Avith  them. 

Do  these  lympliatic  plexuses  exist  in  all  the  tissues, properly  speaking  ?  Here 
is  another  question  of  incontestible  importance,  and  W'hose  solution  is  even 
now  occupying  the  attention  of  anatomists.  Judging  by  analogies,  one  is 
tempted  to  reply  in  the  aflBrmative :  why,  in  fact,  should  the  lymphatics  not 
be  spread  everywhere  throughout  the  organism,  when  the  sanguine  caj)il- 
laries  are  constituent  i)arts  in  the  framework  of  each  tissue  ?  It  is  true  we 
may  ask  if  lymjjhatic  absorption  is  a  necessary  act  in  the  vital  movement ;  and 
although  science  is  far  from  being  satisfied  on  this  point,  we  know  some 
facts  which  at  least  authorize  the  doubt.  On  the  other  hand,  direct  ob- 
servation has  not  revealed  lymj^hatic  plexuses  in  all  organs ;  there  are  even 
tissues  in  which  theii"  existence  has  been  denied :  though  jirematurely,  it  is 
well  to  say,  because  we  may  always  attribute  the  non-success  of  a  lymphatic 
injection  either  to  the  imperfection  of  the  instruments  employed,  the 
insufficiency  of  the  measures  adopted,  or  certain  peculiar  conditions  as  yet 
unknown  attaching  to  the  species  of  animals  selected  for  the  demonstration 
of  the  lymphatic  netw^orks  in  a  certain  region.  As  bearing  out  this  last 
assertion,  we  may  observe  that  M.  Sappey  has  not  yet  been  able  to  inject 
the  pituitary  plexuses  in  Man  or  the  Calf,  and  that  he  loolvs  upon  their 
existence  as  being  at  least  doubtful ;  while  in  the  Horse,  this  lymphatic 
apparatus  is  as  remarkable  for  its  richness,  as  for  the  facility  with  which, 
it  may  be  filled  with  mercury. 

The  following  are  the  most  trustworthy  notions  available  on  this  subject. 

The  lymphatic  vessels  of  the  skin  are  very  numerous,  and  form  tw^o  net- 
works :  one,  with  extremely  fine  meshes,  occupies  the  most  sujierficial 
layer  of  the  dermis  ;  the  other,  placed  beneath  the  deep  face  of  the  integu- 
ment, includes  vessels  more  voluminous  than  the  first,  and  communicates 
with  it  by  multijilied  ramuscules.  These  lymj^hatic  plexuses  are  far  from 
being  equally  developed  in  every  region  :  though  it  is  unanimously  agreed 
that  no  part  is  entirely  destitute  of  them. 

In  the  internal  tegument,  or  mucous  membranes,  an  analogous  disposition 
of  these  vessels  is  met  with.  It  is  more  than  probable  that  they  exist 
throughout  the  whole  extent  of  these  membranes,  though  their  positive 
demonstration  has  yet  to  be  made  in  some  regions.  In  other  regions,  the 
injection  of  these  networks  is,  on  the  contrary,  very  easy,  and  gives  the  most 
magnificent  results ;  we  particularly  mention  the  lingual,  intestinal,  and 
pituitary  mucous  membranes.  The  lymphatics  belonging  to  the  latter 
membrane  assume  so  beautiful  an  aspect  in  the  Horse,  that  we  would  advise 
anatomists  who  desire  to  inject  lymphatics  always  to  choose  that  animal. 
The  operation  is  simple  and  constantly  pei^formed,  and  we  are  astonished 
that  in  the  hands  of  some  individuals  it  should  fail.  Not  only  can  the  two 
networks  of  the  membrane  be  filled,  but  also  the  trunks  arising  from  them, 
and  which  are  directed  towards  the  entrance  of  the  nasal  cavities,  collect  in 
several  thick  branches  around  the  nostril,  and  bend  up  towards  the  free 
43 


630  THE  LYMPHATICS. 

to  reach  the  submaxillary  cavity,  where  they  enter  the  ganglia  situated  to 
the  right  and  left  of  that  space. 

The  majority  of  anatomists  admit  the  presence  of  lymphatic  plexuses  in 
the  splanchnic  or  synovial  serous  membranes.  M.  Sappey,  however,  denies 
this ;  he  considers  the  vessels  that  can  be  so  easily  injected  by  pricking  the 
external  surface  of  a  viscus,  as  belonging  to  its  proper  tissue,  and  not  to  the 
serous  membrane  covering  it.  Those  on  the  inner  face  of  the  walls  of  the 
splanchinc  or  synovial  cavities,  and  which  are  sometimes  filled  with  mercury, 
dg  not,  according  to  him,  come  from  the  serous  tunic,  but  from  the  sub- 
jacent tissues. 

The  lymphatics  do  not  exist  in  vessels,  although  some  modern  anatomists 
have  admitted  them  to  be  present  in  the  inner  layer  of  the  circulatory 
apparatus.  The  lympJiatic  sheaths  discovered  by  His,  Robin,  and  Tomaso, 
around  the  blood-capillaries  of  the  frog,  and  those  of  the  brain  and  spleen 
of  Man.  ought  not  to  be  considered  as  the  lymphatics  of  vessels,  as  they 
merely  surround  the  ultimate  vascular  ramifications,  and  do  not  arise  in  the 
substance  of  their  walls. 

In  the  nervous  tissue  lymphatics  have  not  been  discovered,  though  they 
are  present  in  the  meninges. 

Their  existence  is  doubtful  in  hone  tissue  and  in  the  muscles ;  but  they  are 
abundant  in  the  glands  and  glandiform  organs  of  the  animal  economy, 
forming  the  finest,  richest,  and  most  easily  demonstrated  plexuses. 

It  has  been  stated  above  that  the  lymphatics  commence  by  capillaries 
arranged  in  networks.  Are  these  networJcs  the  real,  or  only  the  apparent,  origin 
of  the  lymphatics  f  This  is  a  question  that  has  been,  and  is  still,  warmly 
discussed.  It  is,  however,  believed  that  the  plexuses  are  fed  by  very  minute 
radicles  lodged  in  the  substance  of  the  tissues. 

But  how  do  these  radicles  originate  ?  In  the  epithelium,  says  Kiiss ;  in 
the  plasmatic  cells  of  the  connective  tissue,  asserts  Virchow  ;  in  the  serous 
membranes,  states  Recklinghausen,  since  he  observed  fatty  matters  pene- 
trate the  lymphatics  by  the  abdominal  face  of  the  diaphragm.  The  opinion 
of  Virchow  is  overthrown  at  present  by  the  reseai-ches  of  Ranvier,  which 
have  modified  the  descrij^tions  given  of  the  connective  tissue.  According  to 
this  authority,  plasmatic  cells  do  not  exist  in  that  tissue ;  what  have  been 
described  as  such  by  Virchow  have  been  only  radiating  spaces  limited  by  the 
fasciculi  of  connective  fibres,  in  which  elements  analogous  to  lymph  globules 
circulate.  It  may  be  added  that  these  fasciculi  are  covered  by  large  flat 
cells,  which  give  these  spaces  the  appearance  of  a  serous  cavity  with  septa  at 
close  intervals.  These  conclusions  of  Ranvier,  then,  should  affirm  the 
hypothesis  of  the  Wurzbourg  professor,  and  tend  to  prove  that  in  the  connec- 
tive tissue  of  the  economy  there  is  an  infinite  number  of  minute  serous  cavities 
into  which  the  lymphatic  vessels  open,  in  which  the  lymph  circulates,  and 
which  are  in  communication,  on  the  other  hand,  with  the  great  splanchnic 
cavities.  It  must  be  mentioned,  however,  that  these  deductions  are  only 
hypothetical,  particularly  at  the  period  of  scientific  evolution  through 
which  we  are  now  passing. 

Course  of  the  Lymphatic  Vessels.— ^The  lymphatics  follow  the  track 
of  the  veins,  and  are  divided,  exactly  like  them,  into  superficial  and  deep 
vessels.  The  latter,  running  parallel  to  each  other,  are  grouped  immediately 
around  the  corresponding  veins,  on  which  they  are  generally  superposed. 
The  fia-st,  although  situated  in  proximity  to  the  superficial  veins,  are  widely 
spread  on  each  side  and  on  the  surface  of  the  suj)erficial  aponeiu'oses,  by 
forming  parallel  fasciculi,  like  the  deep  lymphatics. 


GENERAL  CONSIDERATIONS.  631  • 

The  direction  followed  by  tlie  lymphatics  in  their  course  is  nearly 
always  somewhat  rectilinear  ;  they  never  show  the  flexaosities  which  are  so 
developed  on  the  track  of  certain  arteries,  and  even  some  veins.  Neither  do 
they  communicate  with  one  another  by  transverse  or  arching  anastomoses, 
like  those  so  commonly  met  with  in  the  other  two  orders  of  canals  belonging 
to  the  circulatory  apparatus.  They  frequently,  however,  in  their  parallel 
course,  bifurcate  and  join  the  neighbom'ing  vessels.  (At  certain  situations,  as 
at  some  of  the  articulations,  and  in  other  jjarts,  the  larger  stems  suddenly 
break-up  into  a  close  interlacing  plexus  of  small  vessels  or  capillaries 
(Fig.  295),  which  in  tiieir  disposition,  greatly  resemble  the  rete  mirahile  of 
the  blood-vessels.  This  plexus  is  surrounded  by  condensed  connective 
tissue,  and  is  penetrated  by  blood-vessels,  though  no  communication  takes 
place  between  them  and  these,  the  only  points  at  which  communication  occurs 
being  where  the  great  lymphatic  trunks  empty  themselves  into  the  vena  cava. 
This  rete  would  appear  to  be  the  first  step  towards  the  formation  of  a  lymphatic 
gland.) 

Fi-.  295. 


A   SECTION   OF    A   SIMPLE   RETE    MIRABILE,    VIEWED   FROM   THE   SURFACE. 

a,    a,   Affereut   vessels;    b,    b,    Efferent  vessels   only  partially    visible;    from  the 

popliteal  space. 

But  of  all  the  considerations  relative  to  the  course  of  these  canals,  the 
most  interesting  are  those  which  belong  to  the  glandiform  bodies  2>laced 
along  their  track,  and  whose  abridged  history  we  sliall  give  immediately. 

Termination. — We  have  already  mentioned  the  thoracic  duct  and  the  right 
great  lymphatic  vein  as  being  the  receptacles  of  all  the  absorbent  vessels  of 
the  body,  and  we  have  also  stated  that  these  two  trunks  enter  the  general 
venous  system  ;  this  union  of  the  sanguine  with  the  lymphatic  system  takes 
place  at  the  origin  of  the  anterior  vena  cava,  and  this  vessel  may  be  con- 
sidered as  the  general  confluent  for  all  the  absorbents.  The  researches  of 
Haller,  Cruikshank,  and  Mascagni  first  threw  light  on  this  imjiortant  fact ; 
and  it  is  to  those  of  Fohmaun,  Panizza,  Kossi,  &c.,  that  we  owe  the  dedi- 
cation of  this  discovery. 


632 


TEE  LYMPEATIC8. 


LYMPHATIC     GLANDS. 

The  lymphatic  glands  are  ovoid,  spherical,  or  discoid  bodies  of  medium 
consistency,  grey,  rosy,  or  red-coloured,  and  sometimes  quite  black,  and 
which  at  several  points  intercept  the  course  of  the  lymphatic  vessels. 

Their  number  is  considerable,  and  they  are  rarely  isolated ;  most 
frequently  they  are  collected  in  groups  along  the  blood-vessels.  They  are 
always  larger  in  youth  than  in  old  age. 

All  the  canals  of  the  lymphatic  system  are  provided  with  at  least  one 
gland  on  their  course,  and  some  even  traverse  two  or  three  before  opening  into 
the  thoracic  duct  or  great  lymphatic  vein.  On  reaching  these  glands,  they 
plunge  into  their  structure  in  ramifications,  appearing  on  the  opposite  point 
after  being  reconstituted  into  several  principal  canals,  which  are  generally 
larger  and  less  numerous  than  the  primitive  vessels.  The  latter  take  the 
name  of  afferents  (vasa  infer entia  or  afferentia) ;  the  others  are  named 
efferents  (vasa  efferentia),  because  they  leave  the  gland  to  reach  the  central 
canal. 

Structure. — The  structure  of  the  glands  is  extremely  complicated,  and 
difficult  to  make  out,  in  consequence  of  the  delicateness  of  their  tissue.  The 
following  is  what  is  positively  known  in  reference  to  this  subject. 

The  glands  have  an  envelope  of  connective  tissue  (continuous  with  the 
tunics  of  the  afferent  and  efferent  vessels),  which  surrounds  a  substance  that  is 
readily  perceived  to  be  composed  of  two  layers  of  a  different  aspect :  one 
cortical,  the  other  medullary. 

The  first  appears  to  be  granular,  the  second  somewhat  fibrous.  This 
proper  tissue  is  sustained  by  connective  laminae  (or  septa — continuations  of 
the  capsule)  which  contain  smooth  muscular  fibres.  The  laminae  form  alveoli 
in  the  cortical  layer,  and  a  sort  of  minute  tubes  in  the  central  layer.  These 
alveoli  are  in  their  turn  divided  by  reticular  tissue  into  secondary  spaces, 
which  become  smaller  as  they  lie  near  the  centre;    at  the  periphery,  where 


Fig.  296. 


Fig.  297. 


SECTION  OF   A  LYMPHATIC  GLAND. 
a,  a,  The  fibrous  tissue  that  forms  its  exterior ;  b,  b. 
Superficial  vasa  inferentia ;    c,  c,  Larger  alveoli, 
near  the  surface ;    d,  d,   Smaller   alveoli  of  the 
interior;  e,  e,  Fibrous  walls  of  the  alveoli. 


SIMPLE   LYMPHATIC   GLAND. 

a,  The  capsule  with  sections  of  lym- 
phatics, d,  d,  passing  through  it ; 
b.  Lacunar  and  intercommunicating 
passages,  permeated  by  the  lymph, 
and  forming  the  superficial  lymph 
path  of  Frey ;  c.  Nucleus,  or  me- 
dullary portion,  with  section  of 
blood-vessel  in  the  centre. 


they  are  most  voluminous,  they  are  named  lymphatic  sinuses.     Everywhere 
these  sinuses  are  filled  with  lymph  globules.     The  arrangement  is  identical 


GENERAL  CONSIDERATIONS. 


633 


Fig.  298. 


in  the  medullary  substance  ;  in  the  interior  are  seen  a  gi*eat  number  of 
arterial  capillaries.     The  nerves  are  derived  from  the  sympathetic  system. 

The  atierent  lymphatics,  where  they  enter  the  gland,  communicate  with 
the  alveoli  which  coiTespond  to 
the  cortical  substance  ;  these  al- 
veoli are  connected  by  the/ cords 
of  the  central  layer,  and  the  latter 
are  united,  in  their  turn,  to  the 
alveoli  of  the  opposite  side  of  the 
cortical  substance,  from  which  the 
efferent  ramuscules  spring.  The 
lymph,  therefore,  traverses  every 
part  of  the  gland,  and  during  this 
very  tortuous  course  becomes 
charged  with  solid  particles. 

Certain  glands  have  a  much 
more  simple  structiu'e,  being  en- 
tirely composed  of  lymphatic  capil- 
laries rolled  up  on  themselves  in 
clusters,  and  anastomosing  in  net- 
works. These  capillaries  arise 
from  the  divergent  arborisation  of 
the  afferent  vessels,  and  are  contin- 
uous with  the  convergent  branches 
which,  by  their  union,  form  the 
efferent  lymphatics.  The  organs 
have  received  the  name  of  false 
glands,  though  they  are  leally 
lymphatic  glands.  In  support  of 
this  assertion,  it  may  be  said  that 
"  in  descending  the  animal  series, 
we  see  the  glands  becoming  more 
and  more  simplified,  and  trans- 
formed at  a  great  number  of  points 
into  an  interlacing  of  vessels.  In 
birds,  they  only  occupy  the  base 
of  the  neck  and  the  entrance  to  the 
chest,  forming  in  all  the  other 
regions  simple  plexuses ;  in  rep- 
tiles and  fishes,  the  lymphatic  glands 
disappear  altogether,  and  the  plexuses  that  replace  them  are  themselves  not 
at  all  complicated." — Sappey. 

PREPARATToy  OF  THE  I.YMPHATic  VESSELS. — The  lympliatic  networks  can  only  be 
studied  after  liaving  been  filled  with  mercury  by  means  of  injection;  but  as  this  opeia- 
tion  is  not  usually  practised  by  the  pupils  for  wliom  this  book  is  written,  the  mode  of 
performing  it  will  only  be  traced  in  a  few  words. 

The  apparatus  in  use  consists  of  a  glass  tube  continued  by  a  flexible  one,  which 
carries  at  its  inferior  extremity  an  iron  tap  and  a  fine  canula,  also  of  iron,  or  (better)  gla.-s. 
To  apply  this  apparatus,  the  tube  ought  to  be  suspended  and  then  filled  with  mercury  ; 
the  canula  is  then  seized  by  the  right  hand,  keeping  it  parallel  to  the  membrane  we 
wish  to  inject,  and  burying  it  in  the  most  superficial  layer  of  that  membrane.  Tlie 
extremity  of  the  canula  is  thus  introduced  into  the  midst  of  the  meshes  of  the  lymphatc 
network,  and  necessarily  wounds  some  of  the  capillaries  which  compose  it.  In  opening 
the  tap,  the  mercury  is  allowed  to  flow  into  the  capillaries  by  the  solutions  of  continuity 
they  present,  and  fills  them  in  the  most  perfect  manner.     The  lymphatic  plexuses  being 


PORTION  OF  THE  MEDULLARY  SUBSTANCE  OF  THE 
MESENTERIC  GLAND  OF  AN  OX,  THE  ARTERY 
OF  WHICH  IS  INJECTED  WITH  CHROJIATE  OF 
LEAD  ;    MAGNIFIED    300    DIAMETERS. 

a,  Medullary  substance  with  capillary  network, 
fine  reticulum  of  connective  tissue ,  and  a  few 
lymph  corpuscles ;  h,  h.  Superficial  lymph- 
path,  traversed  by  a  reticulum  of  nucleated 
cells  (c  c),  with  numerous  anastomosing  pro- 
longations. The  lymph  corpuscles  have  for 
the  most  part  been  removed ;  d,  d,  Trabecule 
composed  almost  exclusively  of  unstriped  mus- 
cular tissue ;  g,  A  small  medullary  cord,  or 
bridge,  containing  a  blood-vessel  and  numerous 
lymph  corpuscles. 


(534  TEE  LYMPHATICS. 

always  superposed  on  the  capillary  blood-vessels,  one  is  always  certain  of  injecting  them 
only,  in  taking  the  precaution  to  penetrate  the  membrane  as  superficially  as  possible.  If 
the  point  of  the  canula  enters  too  deeply,  the  mercury  will  pass  into  the  veins,  and  the 
operation  will  be  unsuccessful,  and  must  be  commenced  again. 

To  study  the  branches  and  lymphatic  trunks,  it  will  suffice  to  inflate  them  from 
their  origin  towards  their  termination.  This  procedure,  properly  conducted — and  it  was 
almost  exclusively  the  only  one  adopted  by  the  older  anatomists — gives  the  most  satis- 
factory results,  and  is  even  sufficient  to  demonstrate  the  texture  of  the  glands. 

The  latter  do  not  require  any  particular  precautions  in  their  preparation. 


CHAPTEE  II. 


THE  LYMPHATICS  IN  PARTICULAE. 

We  will    commence   with   the  examination   of   the    thoracic   dud  and  all 
its  affluents,  and  terminate  by  studying  the  great  lymphatic  vein. 

In  this  description  the  glands  and  principal  lymphatic  vessels  will  be 
only  referred  to,  the  disposition  of  the  networks  being  already  noticed 
in  speaking  of  the  diiferent  organs,  and  they  will  be  further  mentioned 
when  speaking  of  the  nervous  system,  the  organs  of  sense,  and  those  of 
generation 

Article  I. — The  Thoracio  Duct.     (Fig.  293,  t  t.) 

Preparation. — Tie  the  jugulars  and  axillary  veins  near  their  termination,  as  well  as 
the  anterior  vena  cava  about  the  middle  of  its  length ;  expose  the  thoracic  duct  by 
removing  the  ribs  on  the  right  side  ;  open  that  canal  near  the  pillars  of  the  diaphragm,, 
and  throw  into  its  interior  two  injections  of  tallow,  one  forward,  the  other  backward 
from  the  incision.  The  first  injection  will  fill  the  canal  and  the  venous  reservoir  which 
is  intersected  between  the  ligatures  applied  to  the  above-named  vessels ;  the  second, 
although  directed  in  opposition  to  the  valves,  overcomes  the  resistance  offered  by  them, 
and  passes  into  Pecquet's  cistern  and  the  principal  branches  which  open  into  that 
confluent.  Or  we  may  select  one  of  these  branches  in  the  abdominal  cavity — for  example, 
one  of  those  wliich  lie  beside  the  colic  arteries  near  their  origin — and  inject  the  entire 
thoracic  duct  from  its  origin  to  its  termination. 

But  this  proceeding  requires  more  practical  ability  than  the  first,  in  order  to  find 
the  vessel  which  is  tc  receive  the  canida;  and  if  the  animal  is  very  fat,  it  is  im- 
possible. 

The  thoracic  duct  is  the  general  confluent  for  all  the  lymphatics  of  the 
body,  vnth  the  exception  of  those  which  come  from  the  right  anterior  limb 
and  the  right  moiety  of  the  head,  neck,  and  thorax. 

Extent. — It  extends  beneath  the  vertebral  column,  from  the  first  lumbar 
vertebra  to  beyond  the  entrance  to  the  thorax. 

Origin. — Its  origin  is  marked  by  a  very  irregular  dilatation  described  as 
the  suhlumhar  reservoir,  or  cistern  of  Pecquet  {receptaculum  or  cyster  nachyli), 
into  which  open  the  principal  affluents  of  the  canal. 

This  reservoir  is  divided,  internally,  by  lamellfe  into  several  incomplete 
compartments,  and  may  be  more  or  less  voluminous  and  circumscribed,  and 
present  very  variable  forms. 

It  is  placed  above  the  abdominal  aorta  and  the  posterior  vena  cava,  at 
the  great  mesenteric  artery,  or  more  frequently  a  little  behind  it.  In  the 
Dog  it  is  of  an  enormous  size,  oval  in  shape,  and  prolonged  between  the 
pillars  of  the  diaphragm  into  the  thoracic  cavity. 

Course. — ^To  this  reservoir  succeeds  a  tube  whose  calibre  is  very  irregular, 
and  appears  singularly  slender  when  compared  with  the  diameter  of  the 


THE  THORACIC  DUCT.  635 

initial  dilatation,  or  that  of  the  affluent  vessels  composing  it.  This  is  the 
thoracic  duct.  We  see  it  enter  between  the  two  pillars  of  the  diaphragm, 
along  with  the  aorta,  deviating  more  or  less  to  the  right  side  of  that  vessel, 
and  follow  it  thus  to  about  the  sixth  dorsal  vertebra,  in  passing  to  the  outside 
of  the  right  intercostal  arteries,  which  it  crosses,  and  beneath  the  great  vena 
azygos,  beside  which  it  lies.  Sometimes,  however,  we  find  it  carried  in  this 
first  part  of  its  course  directly  .above  the  thoracic  aorta,  between  the  double 
series  of  intercostal  arteries,  and  to  the  left  of  the  vena  azygos,  which  is 
then  found  immediately  in  contact  with  the  right  side  of  the  aorta ;  or  it 
may  even  creep  to  the  right  of  that  vein,  concealing  the  greater  part  of  it 
from  sight.  Leaving  the  above-mentioned  dorsal  vertebra,  the  thoracic 
duct  abandons  the  aorta  and  crosses  the  flexure  of  the  vena  azygos  to  the 
left,  to  extend  itself  forward  on  the  left  side  of  the  trachea,  but  often  also 
on  the  right  side.  It  afterwards  places  itself  between  the  two  axillary 
arteries,  crosses  the  interval  comjirised  between  the  prepectoral  glands, 
emerges  from  the  chest,  and  terminates  in  a  manner  to  be  indicated 
hereafter. 

Termination. — The  terminal  extremity  of  the  thoracic  duct  is  always 
provided  with  a  dilatation  analogous  to  that  which  exists  at  its  origin,  though 
much  smaller,  better  circumscribed,  and  less  irregular — a  dilatation  which 
opens  into  the  anterior  vena  cava  sometimes  by  a  single  orifice  furnished 
with  valves,  at  other  times  by  two  very  short  branches,  whose  length  we 
cannot  estimate  at  more  than  the  fifth  part  of  an  inch,  and  which  are  also 
valvular  at  their  entrance.  The  point  where  this  entrance  takes  place  is 
neai'ly  always  at  the  summit  of  the  vena  cava,  and  precisely  at  the  point  of  junc- 
tion of  the  two  jugulars.  The  thoracic  duct  rarely  opens  elsewhere ;  though 
the  fact  that  it  does  so  at  times  is  exemplified  in  a  specimen  in  the  museum 
of  the  Lyons  School,  in  which  the  embouchure  of  the  duct  is  placed 
between  the  termination  of  the  left  jugular  and  that  of  the  corresponding 
axillary  vein. 

Varieties  in  Solipeds. — "  The  thoracic  duct  is  far  from  always  showing 
itself  in  Solipeds  as  I  have  described  it,  but  in  its  com'se  and  insertion 
presents  a  great  number  of  variations  which  we  will  now  pass  in  review. 

"  The  single  canal  is  separated  sometimes,  at  a  part  of  its  length,  into  two 
branches,  which,  after  proceeding  parallel  to  each  other,  soon  unite  to  form 
a  single  vessel.  This  division  usually  takes  place  at  the  base  of  the  heart, 
at  the  place  where  the  lymphatics  of  the  bronchial  and  oesophageal  glands 
enter  ;  it  forms  a  ring  whose  diameter  is  often  not  more  than  four-tenths  of 
an  inch,  or  an  ellipse  whose  larger  axis  is  from  four  to  eight-tenths  of  an  inch. 
We  see  this  produced  once,  twice,  and  even  thrice  on  the  anterior  half  of 
the  canal,  which  becomes  simple  at  its  termination  as  it  was  at  its  origin. 
The  spaces  circumscribed  by  the  bifurcations  constitute  what  have  been 
termed  the  insnlse. 

"  The  canal,  instead  of  remaining  single,  very  often  becomes  double  from 
its  commencement  (Fig.  300).  Then  the  two  canals  are  sensibly  equal, 
or  one  is  larger  than  the  other.  If  they  are  unequal,  it  is  usually  the  right 
which  has  the  advantage,  though  the  conti*ary  sometimes  occurs.  In  any 
ease,  the  two  canals  are  isolated,  one  being  to  the  right,  the  other  to  the  left 
of  the  aorta.  In  advancing  towards  the  entrance  to  the  thorax,  they  remain 
completely  separated,  or  communicate  with  each  other  by  one  or  two,  more 
or  less  voluminous,  transverse  anastomosing  branches.  Eeaching  to  ten, 
eight,  and  sometimes  even  to  two  inches  from  their  opening  into  the  jugular 
gulf,  the  two  canals  approach  each  other,  and  become  confounded  into  a  single 


THE  LYMPHATICS. 

Ficr.  299. 


Fi?.  300. 


Fis.  301. 


DIFFERENT   VARIETIES   OF   THE   THORACIC   DUCT   IN   THE   HORSE. 

A,  Receptaculum  chyli ;  B,  Sublumbar  branches ;  C,  Anterior  mesenteric  branch ;  D,  Posterior 
mesenteric  branch.    In  figure  299  the  duct  is  single,  the  usual  condition,  and  enters  the 


AFFLUENTS  OF  THE  THORACIC  DUCT.  C37 

vessel.  Their  fusion  generally  takes  place  at  the  base  of  the  heart,  and 
I  have  never  seen  them  remain  distinct  throughout  their  whole  extent,  to 
enter  the  vena  cava  separately. 

"Sometimes  (Fig.  301)  there  emanates  from  the  gland,  at  the  entrance 
to  the  thorax,  a  long  canal  which  proceeds  parallel  to  the  first,  and  joins 
it,  after  a  retrograde  course,  near  the  pillars  of  the  diaphragm. 

"  The  thoracic  duct,  double  for  the  greater  part  of  its  extent,  from  the 
time  it  leaves  the  sublumbar  reservoir,  occasionally  ends  by  becomino' 
triple.  In  this  case,  the  largest  of  the  two  canals  is  divided  into  two 
branches ;  then  the  three  canals,  after  pursuing  a  certain  coiU"se,  all  join  at 
the  same  point,  or  tw'o  are  fii-st  united  into  a  single  conduit,  into  which  the 
thiixl  opens  at  a  variable  distance  from  the  confluent  of  the  first."' 

The  affluents  of  the  thoracic  duct. — The  lymphatic  branches  which 
enter  the  thoracic  duct  are  as  remarkable  for  their  number  as  their  volume. 
Some  empty  themselves  into  the  sublumbar  reservoir ;  a  few  vessels  open 
into  the  great  lymphatic  vein  of  thft  thorax,  and  the  others  terminate  in  that 
conduit,  near  its  insertion  into  the  venous  system. 

The  first,  variable  in  their  number,  particularly  the  largest,  are  more 
especially  regarded  as  the  roots  of  the  thoracic  duct. 

Ordinarily  three  are  fountl,  with  a  certain  number  of  small  accessorv 
trupks.  One  of  the  largest  branches  enters  the  posterior  part  of  the  cistern  ; 
very  often  double,  and  even  multiple,  it  arises  from  an  enormous  group  of 
ganglia  placed  in  the  sublumbar  region,  around  the  posterior  extremity  of 
the  abdominal  aorta  and  vena  cava,  and  into  which  are  collected  all  the 
vessels  of  the  posterior  limbs,  the  pelvis,  abdominal  walls,  and  the  pelvi- 
inguinal  viscera.  The  other  two  trunks  reach  the  left  side  of  the  cistern, 
and  result  from  the  union  of  the  lymphatics  w^hich  have  their  source  in  the 
abdominal  digestive  organs;  among  these  lymphatics,  however,  there  are 
some  belonging  to  the  parietes  of  the  stomach  and  the  parenchyma  of  the 
liver  and  spleen,  and  which  approach  the  right  side  of  the  sublumbar  recep- 
tacle, to  open  singly  into  that  cavity. 

The  affluents  the  thoracic  duct  receives  on  its  course,  proceed  fi-om 
the  viscera  contained  in  the  thoracic  cavity,  and  from  the  walls  of  that  cavitv. 

Those  which  terminate  at  the  anterior  extremity  of  the  duct  are  formed 
by  the  lymphatics  of  the  left  anterior  limb,  and  the  left  half  of  the 
thorax,  diaphragm,  neck,  and  head. 

We  will  now  examine  rapidly  all  the  radicular  branches  of  these 
affluents. 


Article  II. — The  Lymphatics  which  form  the  Affluents  of  the 
Thoracic  Duct. 

These  lymphatic  vessels  are  divided  into  five  groups .  1,  These  of  the 
abdomiual  limb,  the  pelvis,  abdominal  parietes,  and  the  pelvi-in<^uinal 
organs ;  2,  Those  of  the  abdominal  digestive  viscera ;  3,  Those  of  the 
organs  contained  in  the  chest ;  4,  Those  of  the  thorax ;  5,  Those  of  the 
head,  neck,  and  anterior  limb. 

•  G  Colin.    '  Traite  cle  Physiologie  Oomparee  des  Aniiuaux  Domestiques,'  vol.  ii 


summit  of  the  anterior  vena  cava  by  two  short  branches.  It  is  double  in  Figure  300 ; 
and  in  Figure  301  it  has  a  long  branch  that  arises  at  the  entrance  to  the  thorax  and 
joins  the  duct,  by  a  i-etrograde  course,  near  the  pillars  of  the  diaphragm. 


638  TEE  LYMPHATICS. 

LYMPHATICS   OP   THE   ABDOMINAL   LIMB,    PELVIS,   ABDOMINAL   PAMETES,    AND 
THE   PELVI-INGUINAL    ORGANS. 

All  these  vessels  converge  towards  an  immense  group  of  ganglia,  named 
the  suhlmnhar  glands.  Besides  these,  there  are  other  groups  on  different 
parts  of  their  track,  constituting  the  deep  inguinal,  superficial  inguinal, 
popliteal,  iliac,  and  precrural  glands.  The  successive  description  of  these 
ganglia,  and  their  afferent  and  efferent  vessels,  will  conveniently  make 
known  the  lymphatic  apparatus,  whose  study  we  have  in  view  in  this 
paragraph. 

1.  Suhlumbar  Glands. 

This  group,  which  occupies,  as  its  name  indicates,  the  suhlumbar  region, 
comprises  :  1,  A  small  single  mass  situated  in  the  sinus  of  the  angle  formed 
between  the  two  internal  iliac  arteries,  and  is  often  formed  by  a  single  large 
ganglion ;  2,  Another  mass  lodged  between  the  two  iliac  arteries,  and  a 
third  placed  without,  and  to  the  front  of,  the  crural  trunk :  these  two  are 
double ;  3,  A  single  agglomeration  of  glandular  lobules  dispersed  around 
the  origin  of  the  small  mesenteric  and  spermatic  arteries :  these  are  isolated 
from  one  another. 

These  different  masses  receive  the  lymphatics  of  the  pelvis,  the  emergent 
branches  of  the  deep  inguinal  ganglia,  those  which  come  from  the  iliac 
ganglia,  some  ramuscules  from  the  rectum  and  large  colon,  and  those  from 
the  spermatic  cord. 

They  are  bound  to  each  other  by  communicating  branches,  and  give  rise 
to  several  series  of  emergent  branches,  which  soon  collect  into  one  or  more 
trunks  that  enter  Pecquet's  reservoir. 

2.  Deep  Inguinal  Glands. 

This  is  a  considerable  mass  of  glandular  lobules  lodged  beneath  the 
aponeurosis  and  the  crural  arches,  in  the  interstice  of  the  adductor  muscles 
of  the  leg,  along  with  the  crural  vessels,  within  which  they  are  placed. 

The  form  of  this  group  is  elongated,  and  its  length  may  be  six  to  eight 
inches,  or  even  more ;  its  superior  extremity  extends  as  high  as  the 
anterior  border  of  the  pubis.  It  is  composed  of  from  fifteen  to  twenty 
lobules,  which  rarely  have  an  uniform  colour,  some  being  grey  and  others 
brown,  or  nearly  black. 

The  afferents  are  formed  by  the  superficial  lymphatics  which  accompany 
the  internal  saphena  vein,  whose  roots  may  be  traced  beyond  the  fetlock, 
and  by  the  deep  satellite  vessels  of  the  crural  artery  and  vein.  The  efferents 
proceed  to  the  suhlumbar  glands,  by  ascending  in  the  abdomen  along  the 
external  iliac  artery  and  vein. 

3.  Superficial  Inguinal  Glands. 

These  are  placed  in  front  of  the  inguinal  ring,  at  the  side  of  the  sheath, 
on  the  track  of  the  subcutaneous  abdominal  artery,  where  they  form  a  small 
elongated  mass  from  two  and  a-half  to  three  inches  in  length,  and  are 
composed  of  a  dozen  principal  lobules. 

Their  afferents,  which  are  very  numerous,  come  from  the  inner  aspect  of 
the  thighs,  the  sheath,  scrotum,  and  the  inferior  abdominal  wall.  The 
efferent  vessels,  much  larger,  but  less  numerous — there  are  only  five  or  six — 
ascend  in  the  inguinal  canal,  accompanying  the  external  pudic  artery  and 


AFFLUENTS  OF  THE  THORACIC  DUCT. 


639 


{^For  Description,  see  p.  640. 


640  THE  LYMPHATICS. 

the  inguinal  nervous  branches.     They  enter  the  deep  inguinal  glands,  after 
traversing  the  crural  ring,  in  company  with  the  prepubic  artery. 

4.  Popliteal  Glands. 

These  glands  represent  a  very  small  mass  composed  of  from  three  to 
five  independent  lobules,  situated  behind  the  great  sciatic  nerve  and  gas- 
trocnemii  muscles,  between  the  long  vastus  and  semitendinous  muscles,  and 
near  the  femoro-popliteal  artery. 

They  receive  some  of  the  lymphatics  which  arise  from  the  environs  of 
the  hock,  and  those  coming  from  the  posterior  and  inferior  part  of  the 
gluteal  region.  Their  efferents  join  the  deep  inguinal  glands,  by  following 
the  muscular  interstices  of  the  thigh. 

5.  Iliac  Glands. 

Slightly  yellow  in  colour,  and  of  a  soft  consistence,  these  glands  are 
five  or  six  in  number,  and  form  a  group  which  is  situated  in  the  triangular 
interval  comprised  between  the  two  branches  of  the  circumflex  iliac  artery. 
They  receive  the  emergent  branches  of  the  anterior  crural  glands,  and  a 
great  number  of  deep  lymphatics  from  the  abdominal  wall.  Their  efierent 
branches,  four  or  five  in  number,  follow  the  circumflex  iliac  artery  to  pass 
to  the  sublumbar  glands. 

6.  Freer ural  Glands. 

Placed  within  the  anterior  border  of  the  fascia  lata,  on  the  track  of  the 
circumflex  iliac  artery,  these  glands  form  a  small  elongated  mass,  composed 
of  a  dozen  lobules  lying  close  to  each  other.  To  this  group  come  afferent 
vessels  from  the  anterior  and  internal  part  of  the  thigh.  It  gives  rise  to 
three  or  four  large  efferent  vessels,  which  ascend  the  internal  face  of  the 
muscle  of  the  fascia  lata,  accompanying  the  circumflex  iliac  artery,  and 
entering  the  abdominal  cavity  near  the  angle  of  the  haunch,  to  join  the  iliac 
glands. 

LYMPHATICS    OF   THE    ABDOMINAL    VISCERA. 

1.  Glands  and  Lymjpliatic  Vessels  of  tJie  Rectum  and  Small  Colon. 

The  glands  in  this  portion  of  the  intestinal  tube  are  :  at  first,  two  or 
three  lobules  placed  at  the  base  of  the  tail  and  on  each  side  of  the  sjihincter 
ani;  in  the  second  place,  a  very  numerous  series  of  small  glandular  bodies 
situated  along  the  small  cui'vature  of  the  viscus;  thirdly,  some  rounded 


A,  Facial  and  nasal  plexus  whose  branches  pass  to  the  subglossal  glands;  B,  0,  Parotid 
lymphatic  gland,  sending  vessels  to  the  pharyngeal  gland ;  D,  E,  Large  trunks  passing 
towards  the  thorax ;  F,  G,  H,  Glands  receiving  the  superficial  lymphatics  of  the  neclv, 
a  portion  of  those  of  the  limbs,  and  those  of  the  pectoral  parietes  ;  i,  Junction  of  the 
jugulars;  J,  Axillary  veins;  K,  Summit  of  anterior  vena  cava;  L,  Thoracic  duct; 
M,  Lymphatics  of  spleen — N,  of  stomach — 0,  of  large  colon — S,  of  small  colon ;  R,  Lac- 
teals  of  small  intestine — all  joining  to  form  the  two  trunks,  p,  Q,  which  open  directly 
into  the  receptaculum  chyli ;  T,  Trunk  which  receives  the  branches  of  the  sublumbar 
glands,  U,  to  which  the  vessels  of  the  internal  iliac  glands,  v,  the  receptacles  of  the 
lymphatics  of  the  abdominal  parietes,  pass  ;  W,  Precrural  glands  receiving  the  lymph- 
atics of  the  posterior  limb,  and  which  arrive  independently  in  the  abdomen ;  X,  Super- 
ficial inguinal  glands  into  which  the  lymphatics  of  the  mamma,  external  generative 
organs,  some  superficial  trunks  of  the  posterior  limb,  etc.,  pass;  Z,  Deep  inguinal 
glands  receiving  the  superficial  lymphatics,  z,  of  the  posterior  limbs. 


AFFLUENTS  OF  TEE  THORACIC  DUCT.  6il 

lobules  comprised  within  the  two  layers  of  the  mesentery,  and  placed  on  the 
track  of  the  arterial  and  venous  divisions. 

Originating  in  the  texture  of  the  mucous  and  muscular  tunics,  the  lymphatic 
radicles  gain  the  glands  of  the  small  cm-vatm-e  of  the  colon,  and  escape  from 
them  as  efferent  branches,  which  pass  in  great  numbers  into  the  mesentery. 
These  efferents,  or  at  least  some  of  them,  traverse  the  lymphatic  glands 
placed  on  the  course  of  the  blood-vessels,  and  collect,  near  the  origin  of  the 
posterior  mesenteric  artery,  into  several  somewhat  voluminous  branckes, 
which  join  the  divisions  of  the  sublumbar  glands,  or  those  of  the  large  colon. 

2.  Glands  and  Lymphatic  Vessels  of  the  Large  Colon. 

There'  is  seen  on  this  enormous  viscus  a  double  chain  of  glands,  lying 
beside  the  colic  arteries,  and  numerous  small  lobules  disseminated  at  a  short 
distance  from  the  principal  glands,  and  on  the  track  of  the  collateral 
branches  furnished  l3y  these  two  vessels, 

Eeceived  at  first,  for  the  most  part,  by  these  lobular  bodies,  the  lym- 
phatics which  have  emanated  from  the  tunics  of  the  viscus  afterwards  join 
the  principal  glands,  from  which  they  emerge  in  forming  several  large 
satellite  branches  for  the  colic  vessels.  Only  two  or  three  in  number  at  the 
pelvic  curvature,  these  branches  are  increased  to  ten  or  twelve  on  arriviug 
near  the  origin  ef  the  colic  arteries.  It  is  from  the  union  of  these  vessels 
with  those  of  the  small  intestine,  that  the  two  large  mesenteric  trunks 
(Fig.  299,  A,  c)  arise,  which,  with  the  branches  emanating  from  the  sub- 
lumbar  glands  (Fig.  299,  b),  form  Pecquet's  reservoir. 

3.  Glands  and  Lymphatic  Vessels  of  the  Ccecum. 

There  exists,  on  the  track  of  each  cfecal  artery,  a  moniliform  series  of 
glands,  farther  apart  from  one  another  than  those  of  the  double  colic  chain, 
to  which  the  vessels  coming  from  the  csecal  membranes  are  directed,  and 
from  which  several  long  satellite  branches  of  the  blood-vessels,  that 
proceed  to  the  same  trunk  as  those  of  the  small  intestine,  depart. 

4.  Glands  and  Lymphatic  Vessels  of  the  Small  Lntestine. 

The  glands  which  receive  the  lymphatic  vessels  from  the  small  intestine 
are  very  large  and  abundant.  About  thirty  in  nmnber,  of  a  grey  colour, 
very  compact,  fusiform,  often  bifurcated  at  their  superior  extremity,  these 
glands  are  placed  in  the  texture  of  the  mesentery,  near  the  origin  of  the 
great  mesenteric  artery,  from  which  those  belonging  to  the  portion  of 
intestine  nearest  the  end  of  the  viscus  are  most  distant.  The  latter  also 
possess,  in  addition,  fifteen  special  small  glandular  lobules,  dispersed  on  the 
track  of  the  ileo-csecal  artery. 

We  have  already  noted  the  richness  of  the  vascular  apparatus  which 
rises  from  the  wall  of  the  small  intestine,  towards  the  mesenteric  glands 
It  must  be  added  that  these  glands  give  rise,  at  their  superior  extremity,  to 
large  emergent  branches,  two  or  three  for  each,  which  soon  coalesce  to  make 
more  voliuninous  branches  that  concur  in  the  formation  of  the  two  intestinal 
roots  of  Pecquet's  reservoir. 

5.  Glands  and  Lymphatic  Vessels  of  the  Stomach. 
There  are  two  classes  of  lymphatic  glands  for  the  stomach     1,  Several 
large  glands  situated  on  the  small  curvature  of  the  organ ;  2,  A  series  ot 


642  THE  LYMPHATICS. 

small  lobules  disseminated  along  the  great  curvature  to  the  attacliment  of  the 
great  omentum. 

The  vessels  which  emerge  from  them  "  gather  on  the  track  of  the  gastric 
arteries  and  veins,  and  ascend  to  the  great  tuberosity,  near  the  trunk  of  the 
coeliac  artery  ;  there  they  anastomose  with  the  lymjihatics  derived  from  the 
spleen  and  liver,  and  unite  into  several  flexuous  branches,  some  of  which 
open  directly  into  the  thoracic  duct,  to  which  the  others  pass,  after  being 
confounded  with  the  anterior  trunk  of  the  intestinal  lymphatics." — Colin. 

6.  Glands  and  LymphattU  Vessels  of  the  Spleen  and  Liver. 

"  The  lymphatic  vessels  of  the  spleen,  rising  some  from  the  interior  of 
the  viscus,  others  from  its  surface,  pass  towards  the  splenic  artery  and  vein ; 
they  traverse  several  groups  of  glands  disposed  on  the  track  of  these  vessels, 
commencing  from  the  middle  of  the  length  of  the  fissure,  ascend,  five  or  six 
in  number,  towards  the  origin  of  the  artery  in  foi.'nung  a  sinuous  mass  whose 
divisions,  anastomosing  with  those  of  the  stomach  and  liver,  open,  on  the 
one  hand,  with  the  latter  in  the  anterior  trunk  of  the  intestinal  lymphatics, 
and,  on  the  other,  into  a  magnificent  plexus  commimicating  directly  with 
the  thoracic  duct. 

'"  Finally,  the  lymphatics  of  the  liver  form  a  very  close  network  on  the 
surface,  and  another  in  the  interior  of  the  parenchyma.  They  collect  towards 
the  posterior  fissure,  and  first  dip  into  a  primary  and  very  small  glandular 
group,  then  into  a  second  group  of  voluminous  round  glands,  which  are 
concealed  between  the  trunk  of  the  vena  portse  and  the  pancreas.  They 
open  in  common  with  the  vessels  of  the  stomach  and  spleen." — Colin. 

GLANDS  AND  LYMPHATIC  VESSELS  OF  THE  ORGANS  CONTAINED  IN  THE 
THORACIC  CAVITY. 

We  find  annexed  to  these  organs  tliree  groups  of  lymphatic  glands  : 
1,  A  series  of  small  granulations  placed  in  tiie  posterior  mediastinum,  on 
the  course  of  the  oesophagus  ;  2,  The  hronckial  glanfs,  situated  in  the  angle 
of  bifurcation  of  the  trachea,  around  the  origin  of  the  bronchi,  which  they 
follow  for  a  short  distance  into  the  pulmonary  parenchyma;  8,  Two  long 
strings  of  lobules  extended  on  the  sides  of  the  inferior  face  of  the  trachea, 
from  the  base  of  the  heart  to  near  the  first  rib. 

The  first  group  receives  the  posterior  lymphatics  of  the  oesophagus,  the 
second  those  of  the  lung,  and  the  third  those  of  the  pericardium,  heart, 
and  a  portion  of  the  trachea  and  cesophagus.  Their  efferents,  unitiug  into 
some  large  trunks,  enter  the  thoracic  duct  at  different  distances. 

GLANDS  AND  LYMPHATIC  VESSELS  OP  THE  THORACIC  WALLS. 

These  glands  form  three  series  :  1,  A  double  chain  of  rounded  grains, 
situated  on  each  side  of  the  dorsal  column,  above  the  intercostal  spaces,  and 
beneath  the  costal  pleura ;  2,  A  frequently  voluminous  mass,  lodged  at  the 
base  of  the  xiphoid  appendix,  behind  the  heart,  and  in  front  of  the  inferior 
part  of  the  diaphragm ;  3,  Some  rudimentary  granulations  lying  beside  the 
internal  thoracic  vessels. 

The  lymphatics  of  the  diaphragm,  after  receiving  those  from  the  convex 
face  of  the  liver  pass  to  the  glands  placed  at  the  base  of  the  muscle,  from 
which  they  escape  in  the  form  of  several  canals  that  accompany  the 
internal  thoracic  vessels,  and  open  into  the  anterior  extremity  of  the  thoracic 


AFFLUENTS  OF  THE  THORACIC  DUCT.  643 

duct  or  tlie  great  lymphatic  vein,  the  majority  of  them  through  the  medium 
of  the  prepectoral  glauds.  These  vessels  receive,  on  their  course,  those 
which  are  brought  from  the  inferior  part  of  the  intercostal  sj)aces  into  the 
suprasternal  granulations. 

The  other  lymphatic  vessels  of  the  costal  wall  ascend  between  the  two 
muscles  which  close  these  spaces,  and  go  to  the  subdorsal  glauds,  which 
afterwards  eject  them,  near  the  origin  of  the  thoracic  duct,  in  the  form  of 
one  or  two  long  vessels  proceeding  in  a  retrograde  manner  on  each  side  of 
the  dorsal  column. 

LYMPHATIC  VESSELS  OF  THE  HEAD,  NECK,  AND  ANTERIOR  LIMB. 

These  vessels  are  all  directed  towards  the  entrance  to  the  chest,  and  are 
gathered  into  a  group  of  glands,  called  the  prepectoral,  which,  with  regard 
to  the  lymphatics  of  the  anterior  part  of  the  body,  play  the  same  part  as 
the  sublumbar  glands  do  to  the  vessels  of  the  posterior  region. 

Before  arriving  at  this  common  point  of  convergence,  they  are  inter- 
cepted on  their  course  by  other  glands,  which  form  four  principal  groups : 
1,  The  guttural  or  pharyngeal  glands ;  2,  The  suhmaxillary  glands ;  3,  The 
p-escapular  glands ;  4,  The  brachial  glands. 

In  studying  these  different  glandular  groups  in  succession,  vnth.  their 
afferent  and  efferent  vessels,  we  will  give  a  sufficient  idea  of  the  entire 
lymphatic  apparatus  iu  the  region  which  remains  for  us  to  examine. 

1.  Prepectoral  Glands.^ 

They  form,  on  each  side  of  the  terminal  extremity  of  the  jugular,  within 
the  inferior  border  of  the  scalenus  muscle,  a  very  large  mass  which  extends 
into  the  chest  by  passing  beneath  the  axillary  vessels,  and  ascends  to  the 
inner  face  of  the  first  rib. 

Into  these  glands  pass  the  lymphatic  vessels  emerging  from  the  pre- 
scapular  and  axillary  glands,  those  which  descend  along  the  trachea  with 
the  common  carotid,  and  which  come  from  the  pharyngeal  glands,  as  well 
as  the  majority  of  those  which  follow  the  internal  thoracic  vessels. 

They  give  rise  to  several  short  and  voluminous  branches  :  those  from 
the  glands  of  the  right  side  form,  by  their  junction,  the  great  lymphatic 
vein ;  and  those  from  the  left  side  join  the  thoracic  duct,  or  are  inserted 
separately  beside  the  latter,  at  the  summit  of  the  anterior  vena  cava. 

2.  Pharyngeal  Glands. 

Very  numerous,  soft,  and  loosely  united  to  one  another,  these  glands  are 
disposed  in  an  elongated  mass  that  occupies  the  lateral  plane  of  the  pharynx, 
below  the  guttural  pouch,  and  which  is  prolonged  backwards  even  beyond 
the  thyroid  body. 

They  receive  all  the  lymphatics  from  the  head :  some  come  directly 
from  the  base  of  the  tongue,  the  soft  palate,  the  pharyngeal  walls,  and  the 
larynx ;  the  others  are  derived  from  the  submaxillary  glands,  and  from  a 
lobule  lodged  in  the  substance  of  the  parotid  gland. 

The  efferent  branches  which  leave  it  are  four  or  five  in  number. 
Always  voluminous,  they  descend  along  the  trachea,  some  separately,  but 
the  majority  are  imited  in  a  fasciculus  which  follows  the  carotid  artery; 

'  These  are  glands,  we  believe,  which  ought  to  be  regarded  as  the  representatives  of 
the  axillary  glands  of  Man. 


644  THE  LYMPHATICS. 

they  are  provided  on  tlieir  course  with  several  elongated  glands,  to  which 
the  lymiihatic  radicles  that  arise  from  the  cervical  portion  of  the  trachea 
and  oisophagus  pass.  On  arriving  near  the  entrance  to  the  chest,  they  are 
lost  in  the  prepectoral  glands.  Some  of  them,  however,  traverse  these 
without  dividing,  and  directly  enter,  on  the  left,  the  thoracic  duct,  and  on 
the  right,  the  great  lymj)hatic  vein.  It  has  been  even  possible  for  us  to 
inject  the  latter  vessel  by  one  of  these  canals  exposed  on  the  right  side. 

3,  Suhmaxillary  or  Suhglossal  Glands. 

They  represent  a  fusiform  mass  situated  at  the  bottom  of  the  inter- 
maxillary space,  in  the  receding  angle  comprised  between  the  digastricus 
on  the  one  side,  and  the  mylo-hyoideus  and  subscapulo-hyoideus  muscles  on 
the  other,  above  and  near  to  the  external  maxillary  artery.  The  lymphatics 
of  the  tongue,  cheeks,  lips,  nostrils,  and  nasal  cavities  join  these  glands. 
Their  efferents  reach  the  pharyngeal  or  guttural  glands. 

4.  Prescapular  Glands. 

By  their  union  they  form  a  species  of  chain,  at  least  twelve  inches  in 
length,  placed  on  the  course  of  the  ascending  branch  of  the  inferior  cervical 
artery,  beneath  the  internal  face  of  the  levator  humeri  muscle,  and  descend- 
ing close  by  the  fixed  insertion  of  the  sterno-maxillaris  muscle. 

The  majority  of  the  lymphatics  of  the  neck,  and  those  of  the  breast  and 
shoulder,  open  into  these  glands.  Their  efferents,  short  and  voluminous, 
enter  the  prepectoral  glands. 

5.  Brachial  Glands. 

Situated  beneath  the  anterior  limb,  within  the  arm,  these  vessels  are 
divided  into  two  groups :  one  placed  near  the  ulnar  articulation,  within  the 
inferior  extremity  of  the  humerus ;  the  other  disposed  in  a  discoid  mass 
behind  the  brachial  vessels,  near  the  common  insertion  of  the  adductor 
muscle  of  the  arm  and  the  great  dorsal  muscle. 

The  first  group  receives  the  vessels  from  the  foot  and  the  fore-arm, 
which  accompany  the  superficial  veins,  or  pass  with  the  deep  arteries  and 
veins  into  the  muscular  interstices.  It  sends  nine  or  ten  flexuous  branches 
to  the  second  group,  into  which  open  directly  the  lymphatics  of  the  arm 
and  shoulder,  and  from  which  emerge  a  certain  number  ot  efferents  that 
pass,  in  company  with  the  axillary  vessels,  to  the  prepectoral  glands. 

Abtiole  III.— Gbeat  Lymphatic  Vein. 

The  second  large  receptive  trunk  of  the  lymphatic  vessels,  this  great 
vein  (the  ductus  hjmphatinis  de.r/er)  leaves  the  prepectoral  glands  of  the  right 
side,  and  therefore  becomes  the  general  confluent  of  the  lymphatics  from 
the  right  anterior  limb,  the  right  axillary  and  superficial  costal  regions, 
as  well  as  the  I'ight  half  of  the  head,  neck,  and  diaphragm. 

This  trunk  is  only  from  three-fourths  of  an  inch  to  two  inches  in  length. 
"  It  usually  opens  at  the  junction  of  the  jugulars,  at  the  side  of  the  canal, 
by  an  orifice  furnished  with  a  double  semilunar  valve.  Sometimes  one  or 
two  of  the  branches  which  concur  to  form  it  describe  circumvolutions  around 
the  corresponding  brachial  trunks  or  some  of  its  divisions,  before  joining 
the  others.     Lastly,  it  is  not  rare  to  see  this  lymphatic  trunk  anastomose 


GREAT  LYMPHATIC  VEIN. 


G45 


with  the  thoracic  duct  by  voluminous  collateral  branches,  then  unite  with 
it  in  such  a  way  as  to  be  inserted  together  by  a  single  orifice  above  the  gulf 
of  the  jugidars." — Colin. 

Fig.  303.  Fig.  304 


THE  GREAT  LYMPHATIC  VEIN  AND  ENTRANCE  OP  THE  THORACIC  DUCT. 
A,  Thoracic  duct ;  B,  Great  lymphatic  vein,  or  right  lymphatic  trunk  ;  c,  D,  Anasto- 
moses established  between  them  near  their  insertion. 


DIFFERENTIAL  CHARACTERS  IN  THE  LTBIPHATIC  SYSTEM  OF  OTHER  THAN  SOLIPED  ANIMALS. 

The  lympliatic  system,  glands  and  vessels,  is  more  developed  in  Ruminants  and  the 
Pig  than  in  the  Carnivora. 

In  this  respect  the  domesticated  animals  may  be  classified  in  the  following  order  : 
Ox,  Slieep,  Horse,  Pig,  Dog,  Cat. 

Ruminants.—"  The  thoracic  duct  of  large  Ruminants,  when  it  has  entered  the  thorax 
by  a  special  opening  in  the  diaphragm,  almost  distinct  from  that  of  the  aortic  arch,  is 
placed  above  and  to  the  right  of  the  aorta,  between  it  and  the  spine.  There,  although 
outside  the  corresponding  intercostal  arteries,  it  is  completely  concealed  by  a  thick  layer 
of  adipose  tissue,  in  which  are  numerous  subdorsal  glands.  Towards  the  fifth  dorsal 
vertebra,  it  receives  a  large  lymphatic  vessel  coming  from  the  enormous  gland  that  exists 
on  the  track  of  the  oesophagus  in  the  posterior  mediastinum;  it  then  crosses  the  direc- 
tion of  the  aorta  and  the  esophagus,  passes  to  the  left,  gains  the  entrance  to  the  thorax, 
and  opens  in  front  of  the  first  rib,  above  the  junction  of  the  left  jugular  with  the  anterior 
vena  cava.' 

"  The  varieties  it  presents  in  the  Ox  are  numerous  and  very  common.  The  rarest 
disposition  is  that  of  a  canal,  single  through- 
out its  entire  length,  such  as  it  has  been 
described,  and  such  as  it  is  usually  found 
to  be  in  small  ruminants  (Fig.  309).  This 
canal  (Fig.  306),  single  at  its  origin  and 
for  the  greater  part  of  its  extent,  often  bifur- 
cates towards  the  base  of  the  heart,  or  at  a 
short  distance  from  its  insertion.  Of  these 
two  branches,  one  passes  to  the  right  of  the 
cesophagus  and  trachea,  the  other  to  the  left 
of  these,  in  following  the  ordinary  direction  ; 
and,  at  the  entrance  to  the  thorax,  they  either 
terminate  separately,  each  in  t!ie  "angle  of 
union  of  the  jugular  and  corresponding  axil- 
lary vein,  or  togethei-  at  the  same  point — the 
gulf  of  the  two  jugular  veins. 

"  It  happens  that  one  of  the  branches  of  the  bifurcated  canal  is  in  its  turn  subdivided 
into  two  smaller  branches,  and  that  the  other  experiences  at  the  same  time  a  similar 


Fisr  30.5. 


ENTRANCE   OF   THE   THORACIC   DUCT   IN 
THE   OX. 


('  Zundel  has  pointed  out  the  curious  fact,  that  in  Ruminants,  the  long,  special, 
lymphatic  gland  situated  between  Ihe  layers  of  the  mediastinum  and  above  the  cesopha- 
gus, sometimes  becomes  so  voluminous  that  its  weight  impedes  rumination,  especially 
when  the  animal  is  lying.  The  bolus  of  food  is  prevented  from  ascending  into  the 
cesophagus,  and  this  may  become  a  frequent  and  periodic  cause  of  indigestion.) 
44 


646  TEE  LYMPHATICS. 

subdivision  :  in  such  a  way  that  the  trunk  of  the  canal,  at  first  single,  becomes  double, 
then  quadruple,  and  consequently  opens  into  the  venous  system  by  four  distinct  orifices! 

Fio;.  306 


Fig.  307. 


VARIETIES  OF   THE   THORACIC  DUCT   IN  THE  OX. 

If  the  branches  of  the  canal,  instead  of  remaining  isolated,  send  off  transverse  anastomoses 

there  results  a  complication  of  which  Solipeds  do  not  offer  an  example  (Fig.  305).  ' 

•  The  thoi-acic  duct  is  oftea  double  throughout  its  extent.    The  two  canals  are  then 


THE  CIRCULATORY  APPARATUS  OF  BIRDS.  647 

detached  separately  from  the  cistern,  one  follows  the  right  side,  the  other  the  left  side  of 
the  aorta,  describing  an  arch  whose  concavity  is  downward  at  the  base  of  the  lieart,  on 
the  lateral  parts  of  the  trachea,  terminating  either  very  near  one  another,  and  on  the  same 
transversal  line,  at  the  junction  of  the  two  jugulars,  or  one  to  the  right,  the  other  to  the  left, 
in  each  of  these  two  veins,  and  not  far  from  their  junction  with  the  axillaries  (Fig.  307.) 
"  When  the  two  canals  arise  from  the  sublumbar  reservoir,  tliey  sometimes  repeatedly 
anastomose  with  each  other  by  sinuous  and  curved  branches,  as  shown  in  figure  308. 

Fi?.  309 


THORACIC  DUCT  OF  SMALL  RF3IINANTS, 

"  Then  all  the  branches  collect  in  the  anterior  mediastinum,  and  constitute  a  single 
canal  which,  near  its  termination,  again  subdivides  into  four  vessels  that  open  separately, 
two  to  the  right  and  two  to  the  left,  in  the  usual  place. 

"  This  variety  is  tlie  most  remarkable  and  complicated  of  all  those  observed  in  the 
domesticated  animals. 

Pig. — "  The  thoracic  duct  of  the  Pig,  usually  single  throughout  its  whole  extent, 
is  sometimes  divided,  at  one  to  one  and  a-half  inches  from  its  insertion,  into  two  branches 
which  soon  reunite  in  an  oval  dilatation  ;  this,  after  receiving  the  vessels  from  the  head, 
neck,  and  limbs,  opens  towards  tlie  extremity  of  the  left  jugular. 

Carnivora. — "  In  the  Dog,  Pecquet's  reservoir  is  enormous ;  in  shape  it  is  ovoid, 
and  is  prolonged  between  the  pdlars  of  the  diaphragm  into  the  thoracic  cavity.  The 
thoracic  duct  of  this  animal  generally  resembles  that  of  the  Pig.  Yet  it  sometimes 
oflers  in  its  course  and  termination  very  numerous  variations :  Rudbecky  has  noticed  a 
bifurcation  above  the  heart,  and  another  bifurcation  wliose  branches  anastomose  with 
each  other  several  times.  Swammerdam  and  Stenon  have  figured  numerous  irregular 
anastomotic  divisions  towards  the  middle  of  a  single  canal,  to  its  point  of  departure.  These 
old  authors  have  indicated  and  represented  double  and  triple  insertions  of  ditferent 
forms.  Lastly,  Bilsius  has  shown  an  arch,  or  rather  a  very  remarkable  ring,  at  the 
entrance  of  the  conduit,  and  at  its  junction  with  the  lymphatic  vessels  of  tiie  neck  and 
anterior  limbs,  and  which  is  more  or  less  analogous  to  that  which  I  have  observed  on 
several  occasions  in  the  Horse,  Pig,  and  Cat."' 


CHAPTEE  III. 

THE  CIRCULATORY  APPARATUS  OF  BIRDS. 

We  will  briefly  examine  the  characteristics  of  the  difierent  portions  of  the  circulatory 
apparatus — the  heart,  blood-vessels,  and  lymphatic  vessels — of  birds. 

Article  I. — The  Heart. 

The  heart,  in  birds,  is  situated  quite  at  the  entrance  to  the  chest,  in  the  median  line, 
and  is  contained  in  a  pericardium  that  adheres  to  the  posterior  diaphragmatic  sept'im 


'  G.  Colin,  op.  cit. 


648  THE  CIRCULATORY  APPARATUS  OF  BIRDS. 

and  the  cervical  reservoir.  In  the  domesticated  species,  it  has  the  form  of  an  acute  cone, 
whose  base  is  surmounted  by  a  less  distinct  auricular  mass  than  in  the  Mammalia. 

Internally  it  has  four  cavities.  The  right  ventricle  is  more  crescent-shaped  tlian  in 
Solipeds,  and  in  a  manner  envelops  the  left  ventricle  in  frunt  and  to  the  right ;  it  does 
not  reach  the  point  of  the  heart.  The  auricular  valve  is  not  tricuspid,  and  offers  a  very 
remarkable  arrangement.  "  Tliis  valve,  iu  fact,  instead  of  being  lormed  as  usual  by 
membranous  curtains  whose  margin  is  retamed  by  cords  fixed  to  the  walls  of  the 
ventricles  is  composed  of  a  wide  muscular  leaf  which  appears  to  be  a  portion  of  the 
inner  wall  of  the  ventricle  detached  from  the  interventricular  septum.  This  septum  is 
convex,  and  the  auriculo-ventricular  orifice  is  situated  in  the  space  comprised  between  it 
and  the  muscular  valve  in  question ;  so  that  when  the  latter  contracts  at  the  systole,  it  is 
applied  against  this  septum  and  closes  the  passage." ' 

There  is  notliing  particular  to  note  with  regard  to  the  left  ventricle,  whose  walls 
are  likewise  thicker  than  those  of  the  right. 

The  auricles  have  a  kind  of  diverticulum  or  sinus,  in  which  tlie  veins  that  open  ioto 
each  of  these  cavities  imite. 

Article  II. — The  Abteeies. 

The  aorta  of  Gallinaceous  birds  ascends  beneath  the  lower  face  of  the  right  lung,  then 
turns  abruptly  backwards  and  a  little  to  the  left.  It  attains  the  median  line  towards 
the  anterior  extremity  of  the  kidneys,  and  in  this  situation  it  reaches  the  sacral  vertebrae, 
where  it  divides  into  three  branches — the  arteries  of  the  pelvic  limbs,  and  the  middle 
sacral  artery. 

Close  to  its  origin,  the  aorta  gives  off  the  brachio-cephalic  (or  innominate)  trunks. 
With  the  Fowl  this  name  is  perfectly  correct,  as  they  both  furnish  vessels  to  the  winge 
and  head.  The  right  passes  upwards  and  forwards,  is  inflected  backwards  at  the  first 
rib,  and  continued  on  the  lower  face  of  the  wing  by  the  humeral  artery.  It  throws  off  a 
thoracic  artery,  whose  volume  is  in  relation  with  that  of  the  pectoral  muscles ;  this  artery 
emits  superficial  branches  that  form  iu  the  skin  of  the  abdomen,  with  other  vessels,  a 
very  rich  plexus  named  by  Barkow  the  rete  mirabile  of  incubation.  It  afterwards  gives  oif 
a  cephalic  trunk,  from  which  arise  the  ascending  cervical,  vertebral,  and  right  carotid 
artery.  The  left  brachio-cephalic  trunk  has  the  same  distribution  as  the  riglit,  a  slight 
difference  only  being  observed  in  its  direction  ;  on  leaving  the  thoracic  cavity  it  describes 
a  small  S  curvature. 

The  carotid  arteries  exhibit  a  somewhat  curious  arrangement.  Each  springs  from 
a  corresponding  brachial  trunk ;  and  placed  at  first  on  the  sides  of  the  neck  they  make 
a  curve,  whose  convexity  is  anterior,  and  gain  the  median  line  by  passing,  the  right 
above  the  oesophagus,  the  left  above  the  trachea.  They  remain  beside  each  other, 
beneath  the  longus  colli,  from  the  second  last  to  the  second  cervical  vertebras,  where 
they  separate  at  an  acute  angle  and  reach  the  border  of  the  jaw,  terminating  there  la 
two  branches — the  internal  and  external  carotid  arteries. 

The  other  collateral  branches  furnished  by  it,  are:  1,  The  intercostal  arteries.  These 
may  arise  from  the  subcosfcil  branches  which  are  parallel  to  the  aorta ;  thus,  in  the  Fotvl, 
there  is  a  common  descending  intercostal  which  proceeds  from  the  vertebral,  and  a  common 
ascending  intercostal  that  leaves  the  aorta  as  it  passes  into  the  abdomen ;  2,  The 
c(eliac  trunk,  which  commences  at  the  middle  of  the  lower  face  of  the  lung,  and  descend- 
ing obliquely  backward,  reaches  the  posterior  aspect  of  the  liver.  It  divides  into  several 
ramuscules,  of  which  there  are  three  principal  vessels:  a  very  fine  one  goes  to  the 
spleen;  a  left  or  middle  one  passes  to  the  gizzard  along  the  proventriculus;  the  third, 
more  voluminous,  is  directed  to  the  right  side,  gives  a  twig  to  the  liver,  and  is  continued 
by  a  long  pancreatico-duodenal  branch  that  joins  the  extremity  of  the  loop  which  the 
intestine  forms  at  its  origin ;  3,  The  anterior  or  superior  mesenteric,  which  arises  at  a  short 
distance  behind  the  cceliac  trunk,  enters  the  mesentery,  and  is  directed  backwards, 
describing  a  curve  whose  convexity  is.antero-inferior,  and  which  emits  twigs  to  the 
intestine ;  4,  The  spermatic  or  ovarian  arteries.  The  inferior  or  posterior  mesenteric 
leaves  the  subsacral  artery,  and,  by  some  ramuscules,  reaches  the  rectum  and  cloaca. 

Shortly  before  its  termination  in  three  branches,  the  aorta  gives  off  an  artery  that 
crosses  the  middle  portion  of  the  kidneys,  leaves  the  abdominal  cavity,  and  becomes  dis- 
tributed to  the  anterior  muscles  of  the  thigh,  after  detaching  the  epigastric  artery.  The 
latter  proceeds  forward,  beneath  the  skin  of  the  abdomen,  and  anastomoses  with  the 
ramifications  of  the  thoracic  artery. 


'  MUne  Edwards — '  I.e^ons  sur  la  Physiologie  et  rAnatomie  Comparee  de  I'Hommo 
et  des  Animaux.'    Vol.  iii. 


TEE  CIRCULATORY  APPARATUS  OF  BIRDS.  C49 

The  arteries  of  the  pelvic  limbs — the  femoral  or  crural,  in  i^assiug  above  the  kidneys, 
furinsh  the  renal  arteries ;  they  then  leave  the  pelvis  by  the  great  ischiatic  notch  im- 
mediately behind  the  coxo-femoral  articulation.  Haced  beneath  the  muscles  on'  the 
posterior  face  of  the  thigh,  in  following  the  branches  of  the  lumbo-sacral  plexus  as  far 
as  the  femoro-tibial  articulation,  they  are  then  continued  by  the  popliteal  vessels.  These 
arteries  throw  off  articular  raniuscules,  the  medullary  artery  of  the  tibia,  and  a  long 
branch  to  the  muscles  on  the  posterior  aspect  of  the  leg  ;  they  are  placed  in  tlie  groove 
resulting  from  the  junction  of  the  tibia  and  fibula,  and  pass  through  the  osseous  inter- 
space to  form  the  anterior  tibial  arteries. 

The  middle  sacral  contiimes  the  aorta  to  the  bottom  of  the  pelvis ;  when  it  arrives 
below  the  last  coccygeal  vertebra,  it  forms  a  kind  of  arch  whose  ramifications  are  dis- 
tributed among  the  muscles  and  quills  of  the  tail. 

Article  III. — The  Veins. 

As  in  Mammals,  the  veins  are  distinguished  as  belonging  to  the  great  and  lesser 
circulation. 

The  veins  of  the  great  circulation  are  collected  into  three  trunks  that  open  into  the 
right  auricle  of  the  heart ;  there  are  two  anterior  venae  cavse  and  one  posterior  vena  cava. 
They  enter  a  particular  compartment,  a  kind  of  sinus,  in  the  auricle. 

The  anterior  vense  cava;  collect  the  blood  from  the  subclavian  arteries  and  those  of 
the  head.  The  jugular  veins,  which  are  their  principal  branches,  are  not  the  satellites 
of  the  carotid  arteries,  as  in  the  larger  domesticated  animals  ;  they  are  superficial  and 
placed  on  the  sides  of  the  trachea ;  while  the  carotids  are  placed  in  the  median  line, 
beneath  the  long  flexor  muscle  of  the  neck.  They  are  not  of  the  same  calibre  in  all 
species,'the  right  jugular  being  more  voluminous  than  the  left ;  there  is  always,  however, 
a  transverse  anastomosis  between  the  two  jugulars,  below  the  base  of  the  cranium. 

The  posterior  or  inferior  vena  cava  commences  at  the  anterior  extremity  of  the 
kidneys,  and  passes  forwards,  traversing  the  right  portion  of  the  liver,  receiving  the 
hepatic  veins,  and  enters  the  right  auricle. 

Among  the  branches  forming  it,  there  may  be  cited  the  femoral  or  crural  veins. 
These  vessels  do  not  accompany  the  corresponding  arteries;  not  entering  the  pelvic 
cavity  by  the  great  ischiatic  notch,  they  pursue  a  course  analogous  to  that  described  for 
these  vessels  in  Solipeds,  in  passing  beneath  the  crural  arch. 

In  birds  furnished  with  a  crest  and  mandibles,  the  skin  of  the  head  is  provided  with 
an  excessively  rich  vascular  plexus. 

Article  IV. — The  Lymphatics. 

Birds  possess  lymphatic  vessels  and  glands.  The  latter  are  few,  and  are  scarcely  met 
with  elsewhere  than  in  the  cervical  region  ;  the  former  are  abundant  in  the  viscera,  and 
unite  in  such  a  manner  as  to  form  iico  thoracic  ducts.  These  ducts  commence  at  the 
celiac  trunk,  and  pass  along  the  lower  face  of  the  lung,  receiving  the  lymphatics  of  that 
organ  and  those  of  the  wings,  and  finally  open  into  the  jugular  veins,  "a  little  in  front  of 
their  union  with  the  axillary  veins.  A  transverse  branch  forms  a  communication 
between  the  two  thoracic  ducts,  towards  theii.-  termination. 


BOOK  VI. 

Apparatus  of  Innervation. 

FIKST  SECTION. 

THE  NERVOUS  SYSTEM  IN  GENERAL. 

The  functions  whose  instruments  we  have  just  described,  suffice  in  them- 
selves to  maintain  nutrition — that  mysterious  molecular  movement  which  is  the 
ultimate  object  of  the  activity  of  organs,  and  the  essence  even  of  life  :  loco- 
niotory  acts  which  permit  the  animal  to  seek  its  food  and  to  introduce  it  into 
its  organism,  lead  to  the  elaboration  and  absorption  of  the  assimilable 
materials  of  the  alimentary  mass  in  the  interior  of  the  digestive  cavity,  the 
circulation  of  the  reparative  fluids  in  the  economy,  and  the  depuration  and 
revivification  of  these  fluids  by  the  action  of  the  lungs  and  the  kidneys :  in 
brief,  could  anything  more  be  required  to  constitute  the  conditions  necessary 
for  the  manifestation  of  the  nutritive  phenomena  ? 

And  yet,  while  the  anatomist  conceives  in  his  mind  a  vertebrate  animal 
exclusively  endowed  with  the  apparatus  destined  to  execute  these  functions ; 
while  he  supposes  the  breath  of  life  and  the  dependent  properties  of  that 
animating  principle  to  be  due  to  these  apparatus,  he  could  not  succeed  in 
creating  an  imaginary  being  capable  of  moving,  digesting,  keeping  in  circula- 
tion the  nutritive  fluids,  reviving  these  fluids  by  respiration  and  urinary  depu- 
ration— in  a  word,  of  executing  all  those  acts  whose  concurrence  is  indispens- 
able to  the  maintenance  of  nutrition,  the  supreme  vital  act.  It  is  because  the 
tissues  of  that  animal,  though  possessing  the  organic  properties  inherent  in 
their  structure,  require  an  excitant  capable  of  bringing  these  properties  into 
play.  Their  inertia  is  due  to  the  absence  of  this  excitant ;  for  all  motion, 
no  matter  what  kind  it  may  be,  demands  for  its  realisation,  not  only  the 
motor  faculty  in  the  organ  which  executes  it,  but  also  an  excitatory  cause. 

But  give  to  this  mutilated  organism,  this  creation  of  our  fancy,  white 
cords,  ramifying  by  extremely  slender  divisions  in  the  depth  of  these 
instruments  of  life,  and  commencing  from  a  central  axis  lodged  in  the 
cranium  and  spinal  canal ;  or,  in  other  words,  add  to  our  incomplete 
animal  an  apparatus  of  innervation,  and,  as  if  by  enchantment,  there  will 
appear  the  first  signs  of  life.  Owing  to  the  peculiar  properties  which  dis- 
tinguish the  tissues  of  this  apparatus,  and  concerning  which  we  will  have 
more  to  say  hereafter,  it  plays  the  part  of  an  exciter  and  regulator  with  regard 
to  the  properties  of  the  other  tissues.  Stimulated  by  the  nervous  system,  these 
properties  no  longer  remain  in  a  latent  state,  but  manifest  themselves  by 
their  usual  results — such  as  contraction  in  the  muscles,  and  exhalation 
and  secretion  in  the  membranes  and  glands ;  then  the  imperfect  being  at 
once  begins  to  digest,  respire,  etc. — in  a  word,  to  live,  and  is  worthy  of 
taking  rank  in  the  animated  world. 


THE  NEBVOUS  SYSTEM  IX  GENERAL.  C51 

But  tlio  effects  of  tliis  radical  transformation  do  not  cease  here.  The 
animal  thus  rendered  apt  to  the  nutritive  movement  acquires,  beyond  this 
vegetative  life,  the  common  appanage  of  all  organised  beings,  all  the  attributes 
of  what  it  has  become  habitual,  after  Bichat,  to  term  animal  life,- — that  is, 
sensibility,  volition,  instinct,  and  intelligence. 

The  perceptive  centre  which  receives  the  excitations  developed  at  the 
periphery  of  organs,  or  in  their  structure ;  the  excitatory  centre  which 
induces  motion  in  all  the  other  tissues ;  the  seat  of  the  instinctive  and 
intellectual  faculties  ;  in  short,  does  not  the  apparatus  of  innervation,  thus 
charged  with  the  grandest  physiological  finality,  present  itself  as  a  most 
attractive  study  ?  We  will  commence  by  giving  a  general  and  succinct  idea 
of  its  conformation,  structure,  properties,  and  functions,  before  undertaking 
the  special  description  of  the  different  parts  composing  it. 


GENERAL    CONFORMATION   OF    THE    NERVOUS    SYSTEM, 

The  apparatus  of  innervation  comprises  a  central  and  a  peripheral 
portion. 

The  first  represents  a  very  elongated  stalk  lodged  in  the  spinal  canal, 
ard  bulging  at  its  anterior  extremity,  which  occupies  the  cranial  cavity. 
TLis  is  named  the  cerebrospinal  axis  or  centre. 

The  second  consists  of  a  double  series  of  ramescent  branches,  which  are 
given  off  laterally  from  the  central  stalk,  to  be  distributed  to  all  parts  of 
the  body  ;  these  branches  are  the  nerves. 

The  Cerebro-spikal  Axis. — The  stalk,  or  axis  properly  so  called, 
lodged  in  the  spinal  canal,  forms  the  spinal  marrow  (or  cord).  .It  is  a  large 
white  cord,  terminating  in  a  point  at  its  posterior  extremity,  and  giving  rise, 
at  each  intervertebral  foramen,  to  one  of  those  nervous  branches  which,  collec- 
tively, represent  the  peripheral  portion  of  the  apparatus  of  innervation. 

The  bulging  extremity  inclosed  in  the  cranium,  is  named  the  enceplialon 
(or  brain).  More  comjilicated  in  its  conformation  than  the  sj^inal  cord,  this 
portion  is  divided,  as  we  will  see,  into  four  parts :  1,  A  white  peduncle,  the 
continuation  of  the  spinal  cord ;  2,  Three  grey-coloured  ovoid  masses,  one 
of  which  is  posterior,  the  other  two  being  anterior,  and  placed  symmetrically 
side  by  side.  This  medullary  prolongation  emits,  right  and  left,  like  the 
cord  itself,  nervous  branches  destined  almost  exclusively  for  the  head. 

The  Nerves. — The  nerves  are  in  the  form  of  fasciculated  cords,  and 
make  their  exit  from  the  orifices  at  the  base  of  the  cranium,  or  tbrough  the 
intervertebral  foramina,  passing  into  all  the  organs  by  ramifying  like 
arteries,  which  they  generally  accompany. 

All  the  nerves  have  their  origin  from  the  medullary  axis,  or  from  its 
encephalic  prolongation,  by  radicles  more  or  less  apparent.  They  are 
divided,  according  to  the  relative  position  of  their  point  of  emergence,  into 
two  great  categories ;  the  superior,  arising  from  the  corresponding  face  of 
the  si)inal  axis  ;  the  others,  inferior,  escaping  from  the  lower  face  :  a  distinc- 
tion which  is  perfectly  appreciable  with  regard  to  the  cord  itself,  but  A\hich 
is  more  difiicult  to  establish  in  the  encephalic  peduncle,  as  it  is  less 
distinct. 

At  their  emergence  from  the  bony  canals  which  give  them  passage, 
the  radicles  of  each  nerve  always  unite  into  a  thick  common  trunk. 

In  the  majority  of  cases,  there  enters  into  the  composition  of  this  trunk 
the  nerves  or  fibres  of  the  two  orders ;  only  a  few  nerves  are  composed  of 
fibres  of  the  one  kind,  and  these  all  belong  to  the  brain. 


652  TEE  NEBVOVS  SYSTEM  IN  GENERAL. 

At  the  origin  of  the  trunk  into  which  the  nerve  roots  are  collected, 
there  is  a  greyish  enlargement  termed  a  ganglion;  but  this  peculiarity 
belongs  exclusively  to  the  superior  fibres. 

After  a  variable  course,  which  is  generally  short,  this  trunk  divides  into 
branches,  the  point  of  departure  for  all  the  nerves  of  the  body.  Among 
these  branches,  those  which  are  expended  in  the  apparatus  of  animal  life  are 
pairs,  and  perfectly  alike  on  both  sides  of  the  body.  Those  of  the  organs 
of  nutrition  are  composed  at  first  of  an  almost  symmetrical  double  chain, 
placed  beneath  the  spinal  column,  and  whose  elements  are  borrowed  from 
nearly  all  the  nervous  trunks  emanating  from  the  cerebro-spinal  axis ;  in 
proceeding  to  their  destination,  their  distribution  is  most  irregularly  com- 
plicated. As  they  offer  on  their  course  a  great  number  of  ganglia  similar  to 
those  we  have  already  mentioned,  they  are  called  ganglionic  nerves  ;  they  are 
also  designated  the  nerves  of  organic  or  vegetative  life,  while  the  others  are 
named  the  nerves  of  animal  life  or  of  relation. 

STRUCTURE    OF    THE   NERVOUS    SYSTEM. 

Two  particular  substances,  one  grey,  the  other  white,  enter  into  the 
or<»anisation  of  the  nervous  apparatus.  These  two  substances  are  formed, 
the  first  by  nerve-tubes  and  united  nerve-cells ;  the  second  by  tubes  alone. 

The  nerve-tubes  are  microscopic  elements,  composed  of  a  proper  wall  and 

contents.     The  wall,  named  the  nervous  sheath  [sheath  of  Schwann),  is  a  thin, 

homogeneous,  elastic  membrane  that  contains  in  its  substance  or  its  inner  face 

some  nuclei  of  cells.     It  is  not  visible  in  quite  fresh  tubes.     The  contents 

comprise,  in  the  centre,  a  solid  core,  the  axis-cylinder 

Fig.  310.  (^oT  primitive  hand  of  Eemak),  which  becomes  very  appa- 

i^  rent  after  the  addition  of  certain  reagents  ;  between  the 

axis-cylinder  and  the  wall  is  found  a  viscid  substance,  the 

nervous  medulla  or  ichite   substance  of  Schicann,  which 

coagulates  very  quickly  under  the  influence  of  cold. 

When  the   medulla  is  solidified,  it  is   seen   to  be 

bordered  by  two  dark  lines,  parallel  to  the  walls  of  the 

^T"  nerve-tubes;   this   aspect   has  caused  the  latter  to  be 

named  "  double-contoured  tubes  (or  nerve-fibres)." 

DIAGRAM    OF   sTRuc-  ^^  ^]^g  ncrvc-tubes  do  not  possess,  at  the  same  time, 

FIBRE   ^^     ^^^"^^  these  three  parts,  for  the  medulla  may  be  absent ;  so  that 

1    Sheath-  2   Medul-  ^^^^^^  ^^'^  distinguished   medullated   and   non-medullated 

'  laiy    substence    of  nerve-Jibres.     The  first,  more  or  less  thick,  are  met  with 

Schwann;  3,  Axis-  in  the  nervous  centres,  and  at  the  origin,  and  in  the 

cylinder,  or  primi-  ini(j(Jle  portion  of  the  nerves ;  the  second  are  found  at 

tive  band.  ^j^^  termination  of  nerves,  and  in  the  great  sympathetic. 

There  are  also  observed  in  the  nerves  of  organic  life,  elongated  elements, 

designated  fibres  of  Bemak,  grey  fibres,  and  nucleated  nervous  fibres.     These 

are  pale,  flattened  fibres,  with  parallel  borders,  and  furnished  with  elliptical 

nuclei.   Some  authorities  consider  these  to  be  bands  of  connective  tissue,  and 

not  nerve  elements. 

The  nerve-cells,  or  corpuscles,  are  voluminous,  and  are  formed  by  a  mass 
of  granular  protoplasm  without  any  enveloping  membrane.  In  the  ganglia 
they  are  covered  by  a  layer  of  fibrous  connective  tissue,  provided  with  nuclei, 
which  appear  to  furnish  them  with  a  very  thick  enveloping  membrane.  The 
nucleus,  with  one  or  two  nucleoli,  is  often  surrounded  by  granulations, 
whose  dark  colour  gives  rise  to  the  supposition  that  they  are  pigment  cells. 


THE  NERVOUS  SYSTEM  IN  GENERAL.  653 

The  nerve-cells  have  prolongations  or  poles,  whose  niimber  varies  from  one 
to  five.  Cells  with  only  one  prolongation  are  named  unipolar ;  those  which 
have  two  are  bipolar ;  and  those  which  have  a  greater  number  are  designa- 
ted multipolar.  These  poles  establish  relations  with  the  nerve-tubes,  and 
constitute  the  origin  of  the  nerves. 

Fio;.  311. 


MULTIPOLAR  OR  STELLATE  GANGLIONIC  NERVE-€ELL,   WITH  ONE   OP   ITS 
PROLONGATIONS — 

a,  Becoming  contmuous  with  the  axis-cylinder  of  a  double-contoured  nerve-fibre,  h. 

Such  are  the  anatomical  elements  that  enter  into  the  structure  of  the 
nervous  system. 

In  the  white  substance  of  the  cerebro-spinal  axis,  only  medullated  nerve- 
tubes  of  every  size  are  found  ;  in  the  grey  substance  are  tubes,  and  a  more 
or  less  considerable  number  of  nerve-cells  are  situated  along  their  course. 

To  these  two  elements  is  added  a  large  quantity  of  blood-vessels,  which 
are  incomparably  more  abundant  in  the  grey  than  in  the  white  substance. 

In  the  nervous  cords,  the  elementary  tubes  are  alone  met  with ;  they  are 
disposed  in  long  bundles,  which  are  collected  into  successively  increasing 
fasciculi.  A  cellulo-vascular  envelope,  the  neurilemma  (or  ijerineurium), 
binds  all  these  fasciculi  into  a  single  cord,  and  forms  a  special  sheath 
around  each  of  them.  Tbe  details  of  their  organisation  will  be  referred  to 
hereafter.- 

It  is  admitted  that  the  ganglionic,  or  nerves  of  organic  life,  possess  a 
greater  quantity  of  slender  tubes  than  the  others.     These  tubes  are  com 
monly  designated  as  the  organic  nerve  fibres.     They  also  contain  fibres  of 
Remak. 

In  the  ganglia,  the  cells  are  joined  to  the  nerve-tubes.  It  has  been  shown, 
by  dissection  and  microscopical  observation,  that  the  corpuscles  composing 
the  ganglia  at  the  origin  of  the  trunks  are  all  attached  to  the  superior 
fibres.     The  other  tubes  have  none. 

In  the  cerebro-spinal  axis,  the  two  substances  are  equally  associated  with 
each  other,  but  in  a  variable  manner,  according  to  the  region.     In  the  cord 


654 


THE  NERVOUS  SYSTEM  IN  GENERAL. 


and  its  prolongation  into  tlie  enceplialon,  tlie  grey  substance  occupies  the 
interior,  while  it  is  spread  over  the  exterior  of  the  encephalic  lobes  and 
envelops  the  white  substance. 


Fig.  312 


Fig.  313. 


MICROSCOPIC   GANGLIOX   FROM   HEART 
OF   FROG. 


BIPOLAR  GANGLIONIC  CELI5  AND  NERVE- 
FIBRES,  FROM  GANGLION  OP  FIFTH  PAIR 
IN   LAMPREY, 


(In  some  instances,  as  in  the  cells  of  various  parts  of  the  spinal  cord, 
the  prolongations  subdivide  and  ramify  in  a  curious  manner,  and  form  a  close 
network  that  penetrates  the  surrounding  nervous  tissue.  In  addition  to 
these,  there  are  other  very  complex  nerve- cells  whose  structure  has  only 


Fiff.    315. 


Fig.  314. 


STELLATE  NERVE-CELL.  FROM  THE 
NUCLE0S  CERVICIS  CORNU  (POS- 
TERIOR VESICULAR  column)  OF 
A  FCETUS  OF  SIX  MONTHS. 
MAGNIFIED   420   DIAMETERS, 


STRUCTURE  OF  GANGLIONIC  NERVE-CELL. 

A,  According  to  Beale ;  B,  According  to 
Arnold. — «,  Straight  fibre ;  6,  Double 
spiral  fibre ;  c,  Capsule  of  connective 
tissue. 


recently  been  clearly  established.  These  have  been  foimd  in  the  sympathetic 
ganglia,  and  each  is  invested  in  a  capsule  of  connective  tissue.  In  shape, 
the  cell  is  pyriform,  and  it  contains  a  nucleus  ;  from  the  narrow  end  spring 
two  fibres,  that  pass  in  opposite  directions  when  they  reach  the  nervous 


TEE  NERVOUS  SYSTEM  IN  GENERAL.  655 

bundle  to  whicli  they  are  distributed.  This  disposition  has  given  rise  to  the 
opinion  that  every  nerve-fibre,  no  matter  how  long  its  course  may  be,  is  a 
loop  that  originates  in,  and  returns  to,  the  same  cell.  One  of  the  fibres  that 
enters  the  cell,  and  looks  like  a  stalk  to  it,  is  usually  straight ;  the  other 
seems  to  arise  from  the  outside  of  the  cell,  is  sometimes  double,  and  circles 
round  the  other  in  a  spiral  manner  two  or  three  times.  Both  fibres  at  first 
resemble  the  cylinder-axis  of  ordinary  nerve-fibres,  and  may  subsequently  be- 
come dark-bordered,  or  remain  pale  fibres.  The  spiral  fibres  bear  large  oblong 
nuclei  in  their  course.  Some  observers  state  that  they  have  traced  the 
straight  fibre  into  the  nucleus,  and  the  spiral  fibre  into  a  plexus  on  the 
exterior  of  the  cell,  but  which  may  be  ultimately  traced  into  the  nucleolus ; 
so  that  the  two  fibres  are  continiious  through  the  nucleus  and  nucleolus). 

PROPERTIES    AND    FUNCTIONS    OF   THE    NERVOUS    SYSTEM. 

It  would  require  a  long  chapter  to  do  justice  to  this  subject,  and  we 
could  not  venture  on  it  here  without  going  beyond  our  domain.  We  will, 
however,  ofier  some  remarks  on  those  notions  connected  with  the  properties 
and  functions  of  the  nervous  system  which  are  strictly  necessary  for  the 
comprehension  of  the  anatomical  facts  to  be  hereafter  dealt  with. 

And  first  as  to  the  properties  of  the  nerves. 

We  will  suppose  the  spinal  canal  to  be  opened  in  the  lumbar  region,  and 
the  cord  laid  bare  in  a  living  animal.  If  we  cut  across  the  inferior  roots  of 
one  of  the  spinal  nerves,  and  if  we  compress  with  a  pair  of  forceps  one  or  more 
of  these  roots,  by  the  end  remaining  attached  to  the  cord,  nothing  results 
to  denote  that  this  irritation  has  had  any  influence  on  the  organism.  But 
if,  instead  of  operating  on  the  central  or  attached  end  of  these  divided  roots, 
we  excite  the  peripheral  end  which  is  continued  by  the  trunk  of  the  nerve, 
contraction  of  the  muscles  of  the  limb  which  receives  the  fibres  coming 
from  the  irritated  roots  is  produced. 

The  muscular  tissue  comports  itself  as  if  the  irritation  were  directly 
applied  to  it ;  so  that  the  nerve  has  served  as  the  medium  of  communication. 
It  has  received  the  excitation,  it  has  been  imp-essioned  by  it,  and  it  has 
conducted  this  to  the  muscles  to  which  the  nerve  is  distributed.  This 
double  reaction  produced  by  the  nervous  tubes  is  their  special  attribute, 
their  essential  property.  With  M.  Vulpian  we  might  designate  it  as  a  whole 
by  the  name  of  veuriJihj  ;  but  it  is  necessary  to  distinguish  the  two  modes  it 
affects  by  naming  the  property  of  being  impressed  by  excitations  as  the 
excitability  of  the  nerve,  and  nervous  conductihility  its  aptitude  to  convey  the 
excitations  which  have  impressed  it. 

The  same  experiment  may  be  repeated  on  the  upper  roots.  It  is  then 
perceived  that  the  pinching,  which  produces  no  effect  at  the  peripheral 
extremity,  causes  pain  when  applied  to  the  central  end.  The  animal 
testifies  immediately,  by  cries  and  movements,  that  it  feels  the  touch  of  the 
forceps.  But,  as  will  be  mentioned  in  a  moment,  the  impression  resulting 
from  this  touch  has  only  been  perceived  by  the  brain  ;  it  has  therefore  been 
conducted  to  the  spinal  cord  by  the  excited  nervous  fibres,  and  then  to  the 
brain  by  the  fibres  of  this  medullary  axis. 

In  putting  to  one  side,  for  the  moment,  the  part  played  by  the  latter  in 
the  phenomenon  now  analysed,  it  will  be  seen  that  the  superior  fibres  of  the 
spinal  nerves  enjoy  the  same  attributes  as  the  inferior ;  neurilily  is  their 
appanage,  and  this  property  is  apjiarent  in  its  two  qualities — excitahility  and 
conductihility.     Only  here  the  latter  property  is  exercised  in  a  centripetal 


656  TEE  NERVOUS  SYSTEM  IN  GENERAL. 

sense  ;  wliile  in  the  first  instance  it  acted  in  a  centrifugal  sense.  But  it  must 
not  be  assumed  that  these  two  conductibilities  are  essentially  distinct.  The 
physiological  diflferences  by  which  they  ajipear  to  be  distinguished  seem  to 
belonw  to  the  difference  in  the  relations  of  the  nerve-fibres  with  the  organs 
to  which  they  are  distributed.  In  one  case,  that  of  the  centrifugal  nerves,  the 
organs  of  reaction — the  muscles — are  placed  at  the  peripheral  extremity  of 
the  nerves ;  in  the  case  of  the  centripetal  nerves,  the  organs  of  reaction — 
the  brain  and  spinal  cord — are  found  at  the  central  extremity  of  the  nervous 
fibres.  This  theory  of  the  unity  of  nervous  conductibility  has,  moreover, 
been  proved  to  be  correct  by  the  researches  of  Philipeaux  and  Vulpian,  who 
have  utilised  the  experiment  of  Gluge  and  Thiernesse  on  the  union  of  the 
central  end  of  the  lingual  (centripetal)  with  the  peripheral  end  of  the 
hypoglossal  nerve  (centrifugal),  to  demonstrate  that  the  fibres  of  the  former 
then  acquire  centrifugal  conductibility. 

It  is  easy  to  demonstrate  that  this  double  property  of  conduction  belongs 
to  all  the  nerve-fibres  springing  from  the  cerebro-spinal  axis,  centripetal 
conductibility  being  peculiar  to  the  superior  fibres,  and  centrifugal  conducti- 
bility to  the  inferior  ones.  It  is  also  demonstrated  that  this  conduction  acts 
in  either  one  sense  or  the  other,  whatever  may  be  the  point  on  the  course  of 
the  nerves  so  stimulated  ;  as  the  nerve-tubes  possess,  throughout  their  whole 
length,  the  property  of  excitability  and  conductibility. 

The  fibres  with  centrifugal  conductibility  constitute  the  motor  nerves ; 
those  whose  conductibility  is  centripetal  are  the  sensitive  nerves.  But  sensi- 
bility does  not  exist  only  in  the  filaments  of  the  superior  roots ;  it  has  also 
been  remarked  in  the  lower  roots,  and  they  owe  it  to  the  filaments  which 
are  given  off  from  the  roots  whose  conductibility  is  centripetal,  and  which 
return  to  the  nervous  centres  by  the  motor  roots.  The  sensitiveness  evinced 
by  these  motor  roots  is  named  recurrent  sensibility. 

The  anatomical  and  physiological  characters  of  the  nerves  persist  as 
long  as  they  communicate  with  the  centres.  If  they  are  divided  at  any  part 
of  their  course,  the  portion  attached  to  the  spinal  axis  still  preserves  its 
properties ;  but  that  situated  beyond  the  section — the  peripheral  end,  as  it 
is  named — degenerates,  and  becomes  incapable  of  conducting  the  sensitive 
impressions,  or  of  transmitting  the  voluntary  motor  excitations. 

Now  as  to  the  spinal  cord. 

Does  the  medullary  axis,  which  has  apparently,  in  great  part,  the 
structure  of  a  nerve,  possess,  like  the  latter,  excitability  and  conductibility, 
those  two  essential  properties  of  the  peripheral  nervous  system  ? 

Excitability  is  entirely  absent  in  the  grey  substance.  On  the  surface  of 
a  section  of  the  cord,  the  slightest,  or  even  the  most  intense  irritation  of  this 
portion  produces  no  reaction.  In  the  white  substance,  this  excitability  can 
only  be  easily  rendered  evident  on  the  surface  of  the  upper  bundles  or 
fasciculi,  where  it  is  exquisite.  With  regard  to  the  always  limited  reactions 
observed  Avhen  the  excitations  are  made  on  the  deej}  part  of  the  fasciculi,  it 
is  difficult  to  say  if  they  result  from  the  excitability  of  the  spinal  cord,  or 
that  of  the  nerve  roots  that  iraverse  the  white  substance. 

Nervous  conductibility  is  certainly  one  of  the  attributes  of  the  spinal 
cord ;  the  transmission  of  excitations  of  the  sensitive  nerves  to  the  brain, 
and  the  voluntary  movements  tliat  result  from  stimulation  of  the  motor 
nerves,  demonstrate  that  the  necessary  medium  between  the  nerves  and 
bi*ain — the  spinal  cord — possesses  conductibility.  But  does  this  portion  of 
the  nervous  system  possess  no  other  property?  Yes;  it  may  act  as  a 
nervous  centre,  and  the  following  experiment  irrefutably  demonstrates  it : 


THE  NERVOUS  SYSTEM  IN  GENERAL.  657 

I  will  suppose  that  an  animal  lias  had  its  spinal  cord  cut  across  in  the 
lumbar  region,  and  I  excite,  by  pinching,  one  of  the  superior  roots  re- 
maining intact  on  the  caudal  portion.  The  stimulus  cannot  be  conducted 
to  the  brain,  as  this  part  is  isolated  from  it ;  and  yet  movements  take  place 
in  the  muscles  of  the  posterior  members.  Does  it  happen  that,  after  section 
of  the  medulla,  the  conductive  property  of  the  nervous  fibres  which  originate 
superiorly  is  interverted  and  changed  into  centrifugal  conductibility  ?  No ; 
for  after  the  transverse  section  of  these  roots,  the  irritation  of  their  central 
end  produces  exactly  the  same  effects.  It  must  be,  therefore,  that  the 
excitation  had  first  reached  the  medulla,  and  was  then  transmitted  by  it  to 
the  muscles  by  means  of  the  centrifugal  current  fibres.  And  this  is  really 
what  occurred  ;  the  section  of  the  whole  of  these  fibres  on  the  trunk  of  the 
cord  hindered  the  manifestation  of  all  movement  in  the  muscles  when  the 
superior  roots  were  touched.  There  is,  as  has  been  said,  reflexion  in  the 
substance  of  the  cord,  on  to  the  inferior  roots,  from  the  irritation  due  to  this 
pinching,  and  the  property  which  permits  the  medullary  axis  to  act  in  this 
manner  is  named  the  reflex  power.  It  may  be  remarked  that,  if  we  suppose 
for  a  moment  the  superior  and  inferior  nervous  roots  to  be  united  in  an 
arch  in  the  substance  of  the  spinal  cord,  this  reflex  property  would  be 
nothing  more  than  the  nervous  conductibility  itself  operating  precisely  in  the 
direction  special  to  each  kind  of  nerves. 

This  union  really  takes  place  ;  only  the  nerve-roots  are  not  in  communi- 
cation, except  through  the  medium  of  the  cells  in  the  grey  substance,  in 
which  the  sensitive  is  changed  into  motor  excitation. 

The  reflex  power  is  extinct  immediately  after  death  occurs  in  Mammals, 
but  it  may  last  for  several  hours,  or  even  for  a  day,  in  a  decapitated  animal 
in  which  asphyxia  has  been  averted  by  pulmonary  insufilation.  The  extent 
of  the  movements  it  determines  is  in  relation  to  the  intensity  of  the  stimuli;s 
which  is  the  primary  cause  of  it ;  merely  localised  when  they  result  from 
a  slight  irritation,  these  movements  may  take  place  in  all  the  muscles  of  the 
body  after  an  energetic  stimulation. 

Let  us  now  inquire  into  the  attributes  of  the  encephalcn. 

Excitability  is  not  remarked  in  all  parts  of  the  brain ;  it  exists  in 
several  points  of  the  medulla  oblongata,  and  in  the  deep  substance  of  the 
cerebellum ;  but  it  cannot  be  rendered  evident  on  the  surface  of  the  latter, 
nor  yet  in  the  cerebral  hemispheres.  The  brain  possesses  conductibility, 
because  the  grey  substance  composing  it  is  the  receiver  of,  and  the  point  of 
departure  for,  all  the  excitations.  In  fine,  the  encephalic  mass  should 
possess  neurility  like  the  nerves,  but  this  general  property  is  more  or  less 
modified.  What  more  particularly  distinguishes  the  encej)halon  is  its  action 
as  a  sensitivo-motor  centre ;  in  it  arrive  the  excitations  from  the  sensitive 
nerves,  and  there  they  are  felt  and  judged.  In  the  brain  arise  the  motor 
excitations  which  result  in  spontaneous  voluntary  movements. 

In  an  animal  paralysed  by  division  of  the  cord  at  the  occipito-atloid 
articulation,  and  in  which  death  has  been  prevented  by  artificial  respiration, 
observation  demonstrates  that  sensibility  and  spontaneous  motricity  are 
preserved  in  the  head,  whose  nerves  are  in  direct  communication  with  the 
encephalon.  Pinch  the  upper  lip,  and  the  patient  testifies  by  the  movements 
of  this  organ  that  it  feels  pain.  Pass  the  finger  towards  the  eye,  and  the 
eyelids  are  twinkled  and  closed :  a  proof  that  the  animal  sees  objects, 
appreciates  the  distance  which  separates  it  from  them,  and  tries  to  remove 
the  eye  from  their  contact.  More  striking  still,  the  animal  feels  hungry, 
and  endeavours  to  satisfy  this  cra\'ing  by  seizing  the  food  within  its  reach,  and 


C58  THE  NERVOUS  SYSTEM  IN  GENERAL. 

masticating  and  swallowing  it.  After  this  demonstration,  it  is  no  longer 
possible  to  doubt  that,  if  an  animal /eeZs,  it  is  by  the  brain,  and  if  it  loills,  it  is 
also  by  the  brain. 

But  sensibility  and  volition  do  not  constitute  the  only  attributes  of  the 
brain  tissue ;  for  it  is  the  seat  of  other  manifestations  not  less  interesting — 
those  of  the  instincts  and  intelligence. 

If  the  encephalon  is  to  be  considered  as  the  immediate  instrument  of  all 
these  phenomena,  it  would  be  impossible — it  is  impossible — to  attribute  the 
cause,  properly  speaking,  to  the  activity  of  its  physical  matter ;  above  this 
hovers  a  mysterious  power  that  can  only  be  demonstrated  by  a  methodical 
analysis  of  the  manifestations  produced  by  that  activity.  But  we  dare  not 
venture  to  touch  upon  the  nature  of  this  power;  the  first  word  would  be 
useless  without  the  last,  and  this  would  carry  us  too  far. 

To  sum  up,  the  nerves  possess  a  single  vital  property — neurility,  which 
is  manifested  by  excitahility  and  by  centripetal  conduct ihility  in  the  nerves 
whose  roots  are  uppermost,  centrifugal  conductibility  in  the  nerves  whose 
roots  are  inferior. 

The  spinal  cord  is  inexcitable  in  its  grey  substance,  but  is  excitable  on 
the  surface  of  its  superior  fasciculi,  though  scarcely  so  in  the  remainder  of  its 
white  substance.  It  serves  as  the  organ  of  transmission  between  the  brain 
and  the  nerve-roots;  and  is,  in  addition,  endowed  with  the  reflex  property  or 
power. 

The  brain  has  for  its  appanage  a  special  activity,  to  which  is  due  sensi- 
bility, volition,  and  the  manifestations  of  instinct  and  intelligence. 

It  remains  to  make  known  the  nature  of  the  influence  the  nervous  system 
exercises  on  the  other  apparatus  through  the  properties  we  know  it  to 
possess.     But  here  again  we  must  limit  ourselves  to  principles. 

Since  Bichat's  time,  it  has  been  agreed  to  divide  into  two  great  classes 
those  functions  whose  operation  maintains  the  life  jjroper  of  the  individual  : 
those  of  animal  life  or  relation,  and  those  of  organic  or  vegetative  life. 

The  first,  which  are  exercised  with  consciousness,  comprise  the  sensorial 
functions  and  voluntary  movements;  the  latter  are  provoked  by  the  spon- 
taneous excitation  originating  in  the  brain,  and  transmitted  to  the  muscles 
by  the  nerve-fibres  whose  conductibility  is  centrifugal ;  the  former  have 
for  their  object  the  appreciation,  by  the  brain,  of  tactile  sensations — of  heat, 
light,  taste,  and  smell,  by  means,  or  through  the  instrumentality,  of  the 
nerve-fibres  possessed  of  centripetal  conductibility,  which  transmits  to  the 
encephalic  mass  the  stimulus  developed  at  their  terminal  extremity  by  these 
diverse  physical  agents. 

The  functions  of  vegetative  life — those  which  are  executed  unconsciously, 
we  may  say,  in  animals,  and  which  are  not  the  result  of  physico-chemical 
forces — are  placed  under  the  influence  of  the  reflex  power  of  the  spinal  cord. 
For  example,  the  stomach  is  empty  and  its  mucous  and  muscular  membranes 
remain  altogether  passive ;  there  being  no  contractions  in  the  first,  nor 
secretion  of  gastric  fluid  in  the  second.  Food  arrives  in  its  interior,  and 
immediately  its  activity  is  develoj)ed ;  the  muscular  tunic  executes  move- 
ments which  cause  the  mixture  of  the  food,  and  propel  it  towards  the  pyloric 
orifice ;  while  the  free  surface  of  the  internal  membrane  pours  out  an 
abundant  solvent  secretion.  This  change  is  due  to  the  stimulus  exercised 
by  the  presence  of  the  alimentary  particles  on  the  extremity  of  the  centri- 
petal nerve-fibres,  and  which  has  been  transmitted  by  them  to  the  medul- 
lary axis,  there  reflected  on  the  centrifugal  fibres,  and  carried  by  these  to  the 
tunics  of  the  stomach,  whose  special  functions  are  thus  brought  into  play. 


THE  CEREBROSPINAL  AXIS.  659 

It  is  worthy  of  remark  that  the  properties  of  the  nervous  system,  which 
act  in  so  important  a  manner  on  the  organs  of  vegetative  life,  have  no 
direct  influence  on  nutrition  itself.  Destruction  of  the  nerves  in  a  certain 
region  will  certainly  derange  the  nutrition  of  its  tissues,  in  consequence  of 
the  paralysis  of  the  vessels,  but  it  is  not  destroyed.  There  is  an  immense 
category  of  organised  beings — vegetables,  for  instance — in  which  nutrition 
is  very  active,  and  in  which  there  is  no  nervous  system.  So  that  the 
property  which  determines  the  essential  phenomena  of  nutrition  is  indepen- 
dent of  nervous  action :  it  is  an  attribute  of  livincj  matter. 


SECOND  SECTION. 

The  Central  Axis  of  the  Nervous  System. 

The  cerebrospinal  axis  is  resolved,  as  we  have  said,  into  two  principal 
sections — the  spinal  cord  and  the  encepTialon.  We  will  study  these  two 
portions  in  succession,  the  spinal  cord  first,  in  order  to  facilitate  our  de- 
scription, although  that  organ  only  holds  the  second  place  in  a  physiological 
jjoint  of  view.  The  protective  parts  of  these  two  a^jparatus  will,  however,  be 
examined  before  we  proceed  further. 


CHAPTER  I. 

THE    ENVELOPING   AND   PROTECTING   PARTS    OF   THE   CEREBRO-SPINAL 

AXIS. 

The  cerebro-spinal  apparatus  is  lodged,  as  we  abeady  know,  in  a  bony  case 
— the  spinal  canal — which  is  prolonged  anteriorly  by  the  cranial  cavity  ;  but 
it  is  protected  more  immediately  by  three  envelopes,  which  have  received  the 
names  of  dura  mater,  arachnoid,  and  pia  mater. 

THE   BONY    CASE   THAT   CONTAINS    THE    CEREBRO-SPINAL    AXIS. 

A  knowledge  of  the  bones  which  enter  into  the  composition  of  this  pro- 
tective case,  cannot  be  acquired  without  also  knowing  the  case  itself;  so 
that  we  dispense  with  its  special  study  here.  We  will  allude,  however,  to 
the  succinct  terms  already  employed  in  describing  the  spinal  canal,  and  in 
the  same  spirit  of  concision  will  also  describe  what  has  hitherto  been 
deferred — the  cranial  cavity. 

1.  The  Spinal  Canal. 
This  canal  communicates,  anteriorly,  with  the  cavity  of  the  cranium. 
Very  wide  at  the  atlas  to  receive  the  odontoid  process,  and  allow  those 
rotatory  movements  of  the  head  which  prevent  the  medulla  being  injured, 
the  spinal  canal  suddenly  contracts  at  the  axis  ;  it  expands  again  at  the  end 
of  the  cervical,  and  the  commencenunt  of  the  dorsal  region,  where  the 
medulla  presents  a  greater  volume,  and  the  movements  of  the  spine  are  very 
extensive.  Towards  the  middle  of  the  back,  the  spinal  canal  offers  its 
smallest  diameter,  but  on  leaving  this  portion,  and  as  far  as  the  lumbo -sacral 


660  THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 

articulation,  it  widens  again ;  after  wliicli  it  rapidly  lessens,  and  altogether 
disappears  towards  the  fourth  or  fifth  coccygeal  vertebra.  The  lumbo- 
sacral dilatation  coincides  with  the  expansion  the  cord  shows  at  this  point, 
and  with  the  enormous  volume  of  the  nerves  lying  beside  it. 

2.  Tlie  Cranial  Cavity.     (Figs.  22,  23,  175.) 

This  is  a  very  irregular  oval  box,  whose  walls  are  formed  by  the  frontal, 
parietal,  occipital,  ethmoidal,  and  temporal  bones. 

It  presents  for  consideration  four  planes  and  two  extremities. 

The  superior  plane  offers  on  the  middle  line,  and  towards  its  superior 
third,  the  parietal  protuberance,  the  two  lateral  crests  of  which  concur 
with  that  eminence  in  dividing  the  cranial  cavity  into  two  compartments : 
one  posterior,  destined  to  contain  the  cerebellum ;  the  other  anterior, 
incomparably  larger,  lodging  the  cerebral  hemispheres,  and  divided  by  the 
single  rudimentary  crest  Avhich  begins  at  the  fixlciform  eminence,  and  joins 
the  crista  galli,  into  two  lateral  sections — one  for  each  hemisphere.  Here- 
after we  will  see  that  the  folds  of  the  dura  mater  are  attached  to  this 
parietal  protuberance,  and  to  the  ridges  detached  from  it,  thus  rendering 
much  more  perfect  the  partitioning  of  the  cranial  cavity. 

On  the  lateral  planes  there  is  also  noticed  the  division  into  a  cerebellar 
and  cerebral  compartment,  due  to  the  lateral  crests  of  the  falciform  j)rocess, 
which  are  prolonged  obliquely  to  near  the  sphenoid  bone :  the  first  section 
is  formed  by  the  occipital  and  the  inner  face  of  the  petrous  bone ;  the 
second  by  the  squamous  portion  of  the  temporal,  the  frontal,  and  the  great 
ala  of  the  sphenoid  bone.  Both  are  concave,  and  marked  by  digital 
impressions,  as  they  also  are  on  the  superior  plane. 

The  inferior  plane,  very  irregular,  offers  from  behind  forward :  1,  On 
the  median  line,  the  basilar  channel,  into  which  the  greater  portion  of  the 
encephalic  isthmus  is  received ;  the  pituitary  fossa,  made  deeper  by  a 
circular  fold  of  the  dura  mater,  and  lodging  the  gland  of  that  name ;  the 
optic  fossa,  where  the  chiasma  of  the  optic  nerves  is  situated ;  2,  On  the 
sides,  the  foramen  lacerum,  partly  closed  by  cartilaginous  substance,  and  by 
the  dura  mater ;  the  cavernous  sinuses  and  maxillary  fissures,  outside  which 
is  remarked  a  deep  and  wide  digital  impression  for  the  reception  of  the 
mastoid  lobule,  or  inferior  lobe  of  the  brain. 

The  posterior  extremit!/  of  the  cranial  cavity  presents  the  occipital 
foramen,  by  means  of  which  this  cavity  communicates  with  the  spinal  canal. 

The  anterior  extremity  offers,  in  the  median  plane,  the  crista  galli 
process,  or  superior  border  of  the  perpendicular  plate  of  the  ethmoid 
bone  ;  on  the  sides,  the  two  ethmoidal  fossas — deep  depressions  containing 
the  olfactory  lobes,  and  at  the  bottom  of  which  is  observed  the  cribriform 
aspect  of  the  transverse  plate  of  that  bone. 

THE    ENVELOPES    OF    THE    CEEEBRO-SPINAL    AXIS. 

The  three  membranes  which  cover  the  cerebro-spinal  axis,  and  separate 
it  from  the  walls  of  the  bony  cavity  inclosing  it,  are  thus  designated. 
Generally  termed  meninges,  and  distinguished  as  external,  middle,  and 
internal  meninge,  these  membranes  are  better  known  as  the  dura  mater, 
arachnoid,  and  pia  mater — names  which  will  be  employed  in  our  description. 

The  dura  mater,  or  external  meninge,  is  a  strong  fibrous  membrane  in 
contact  with  the  walls  of  the  cranium  and  the  spinal  canal. 

The  arachnoid,  or  middle  meninge,  is  a  tunic  of  a  serous  nature,  which 


TEE  CEREBBO-SPINAL  AXIS.  GGl 

resolves  itself  into  two  layers :  an  external,  applied  to  the  inner  face  of  the 
dura  mater ;  and  an  internal,  spread,  through  the  medium  of  the  pia  mater, 
over  the  cerebro-spinal  axis,  from  which  it  is  again  separated  in  a  great 
number  of  points  by  a  particular  fluid,  the  subarachnoid. 

The  pia  mater,  or  internal  meninge,  is  the  proper  envelope  of  the  central 
nervous  stalk ;  it  is  cellulo-vascular,  closely  adherent  to  the  external  surface 
of  the  cord,  united  to  the  visceral  layer  of  the  arachnoid  by  more  or  less 
dense  connective  tissue,  between  the  meshes  of  which  is  deposited  the 
subarachnoid  fluid. 

This  arrangement  of  the  cerebro-spinal  envelopes  permits  the  cerebro- 
spinal axis  to  be  assimilated,  to  a  certain  extent,  to  a  viscus,  and  the  bony 
sheath  containing  them  to  a  splanchnic  cavity,  whose  serous  membrane,  the 
arachiuid,  is  covered  outside  its  parietal  layer  by  a  fibrous  expansion,  the 
dura  mater,  and  within  its  visceral  layer  by  a  cellulo-vascular  tunic,  the 
jna  mater,  or  internal  meninge. 

This  collective  view  of  the  envelojies  belonging  to  the  nervous  centres 
will  now  be  followed  by  a  special  descrij)tion  of  each,  in  which  their  spinal 
and  cranial  portions  will  be  successively  considered,  after  glancing  at  them 
in  a  general  manner. 

1.  The  Dura  Mater. 

This  membrane  is  the  most  external  and  the  strongest  of  the  cerebro- 
spinal envelopes,  and  covers  the  walls  of  the  cerebro-spinal  cavity,  whose 
form  it  exactly  rej)eats.  It  is,  therefore,  a  second  protective  sheath,  which 
is  dilated  at  its  anterior  extremity  into  an  ovoid  cavity  that  lodges  the 
encephalon,  and  terminates  in  a  prolonged  point  in  the  coccygeal  vertebrfe. 

It  ofiers  two  faces :  an  external,  in  contact  with  the  walls  of  the  bony 
case ;  and  an  internal,  adhering  in  the  most  intimate  manner  to  the  external 
layer  of  the  arachnoid. 

In  several  points  of  its  extent  it  is  traversed  by  the  nerves  which  escape 
from  the  cerebro-spinal  axis,  and  by  the  vessels  destined  to  this  portion  of 
the  nervous  system. 

Structure. — The  dura  mater  possesses  the  texture  of  all  white  fibrous 
membranes.  It  is  composed  of  parallel  longitudinal  fasciculi  of  connective 
tissue,  mixed  with  some  fine  elastic  fibres.  Bourgelat  thought  they  formed 
two  distinct  layers — an  external  and  internal ;  but  nowhere  is  it  possible  to 
demonstrate  this.  It  receives  blood-vessels  ;  the  arteries  are  derived,  for  the 
spinal  portion,  from  the  vertebral,  the  intercostals,  lumbar,  and  lateral 
sacrals ;  for  the  cranial  portion,  meningeal  ramuscules,  such  as  the  ethmoidal 
branch  of  the  nasal,  the  spheno-spinous,  and  tympanic,  mastoideal,  and 
cerebro-spinal  arteries.  Nerves  have  been  seen  passing  to  its  cranial  portion  ; 
these  have  been  divided  into  anterior,  middle,  and  posterior.  The  first 
are  furnished  by  the  ethmoidal  filament  of  the  nasal  nerve ;  the  second  from 
the  Gasserian  ganglion ;  and  the  third,  by  the  ophthalmic  branch  of  Willis. 
The  existence  of  lymphatic  vessels  has  not  yet  been  demonstrated. 

Spinal  Dura  Mater  (Theca  Vertebralis). — This  is  a  very  elongated 
sheath,  continuous  at  the  occipital  foramen  with  the  encephalic  dura  mater,  and 
terminated  behind  by  an  attenuated  point  lodged  in  the  narrow  channel  which, 
in  the  middle  coccygeal  vertebrre,  represents  a  trace  of  the  spinal  canal. 
As  it  is  in  shape  exactly  like  the  latter,  its  largest  diameter  is  at  the  atlas, 
and  at  the  brachial  and  lumbo- sacral  enlargements  of  the  spinal  cord.  Its 
capacity  depends  greatly  on  the  volume  of  the  latter,  and  in  some  of  its 
parts  it  can  allow  the  accumulation  of  the  cerebro-spinal  fluid ;  this 
45 


G62  TEE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 

accumulation  is  impossible  for  nearly  the  whole  extent  of  the  cranial 
region. 

The  external  face  of  the  dura  mater  is  very  slightly  adherent,  esijecially 
above,  to  the  walls  of  the  spinal  canal ;  and  it  is  even  separated  from  them, 
at  the  intervertebral  spaces,  by  a  certain  quantity  of  adipose  tissue  which  is 
never  absent,  though  the  animals  be  ever  so  emaciated.  This  face  covers, 
inferiorly,  the  common  superior  ligament,  and  the  veins  we  have  described 
as  spinal  sinuses. 

The  internal  face  gives  attachment,  between  each  pair  of  nerves,  to  the 
festoons  of  the  dentated  membrane,  a  dependency  of  the  pia  mater.  It  is 
rendered  smooth  and  polished  by  the  external  layer  of  the  arachnoid,  to 
which  it  is  so  firmly  united,  that  it  is  needless  to  attempt  their  separation. 
Here  the  external  layer  of  the  arachnoid  is  reduced  to  a  simple  layer  formed 
by  a  row  of  cells  with  flattened  nuclei. 

On  each  side,  the  substance  of  this  meninge  is  completely  traversed  by  a 
double  series  of  orifices  for  the  passage  of  the  spinal  nerves,  around  which 
it  sends  small  special  sheaths  as  far  as  the  intervertebral  foramina. 

Cranial  or  Encephalic  Dura  Mater. — This  membrane  forms  a  sac 
which  is  exactly  moulded  by  its  external  face  to  the  cranial  parietes,  and  by 
its  internal  face  to  the  superficial  surface  of  the  encephalon.  The  latter, 
therefore,  completely  fills  the  cavity  of  the  cranium,  a  circumstance  that 
explains  why  an  accumulation  of  fluid  is  impossible  in  this  region. 

External  surface. — It  adheres  strongly,  by  cellulo-vascular  bands,  to  the 
cranial  walls,  whose  undulations  it  follows ;  this  adhesion  is  not,  however, 
equally  marked  everywhere,  for  on  the  sides  of  the  roof  of  the  cerebral 
compartment  it  is  least  intimate,  and  it  is  closest  on  the  middle  plane  of 
this  roof,  on  the  crista  galli,  around  the  parietal  protuberance,  on  its  crests, 
and  towards  the  lateral  faces  of  the  cerebellar  compartment  at  the  petrous 
bones,  where  the  membrane  is  very  thin. 

This  face  gives  rise  to  a  number  of  prolonged  sheaths,  corresponding  to 
-the  nerves  leaving  the  base  of  the  cranium.  The  principal  are  found  around 
the  ethmoidal  filaments,  the  optic  nerves,  and  the  two  thick  branches 
furnished  by  the  Gasserian  ganglion. 

Internal  surface. — The  internal  surface  of  the  cranial  dura  mater  is 
covered  by  the  parietal  layer  of  the  arachnoid,  which  is  firmly  attached  to 
it  only  in  the  spinal  region.  It  sends  into  the  cranial  cavity  three  pro- 
longations, which  are  distinguished  as  the  falx  cerebri  (falx,  a  sickle), 
.tentorium  cerebelli  {tentorium,  a  tent),  and  i)iQ  pituitary  fold.  These  processes 
■complete  the  partitioning  of  the  cranial  cavity,  isolate  the  various  external 
ibulgings  of  the  encephalic  mass,  and  protect  them  from  the  compression 
they  might  exercise  on  each  other. 

a.  The  falx  cerebri  is  a  vertical  lamina  comprised  between  the  two 
cerebral  hemispheres,  and  owes  its  name  to  its  sickle-like  form. 

Its  antero-superior  border  is  adherent  and  very  convex,  and  corresponds 
to  Abe  crista  galli  process,  as  well  as  to  the  median  ridge  on  the  inner 
face  of  the  frontal  and  parietal  bones.  This  border  is  very  thick,  and 
hollowed  internally  by  a  prismatic  and  triangular  venous  canal,  which  con- 
stitutes the  median  sinus. 

Towards  its  inferior  border,  which  is  free  and  concave,  and  corresponds 
to  the  corpus  callosum,  the  falciform  process  is  extremely  thin,  and  cribbled 
lite  lace-work. 

The  posterior  extremity,  or  base  of  the  falx,  rests  on  the  parietal 
;  protuberance. 


THE  CEREBROSPINAL  AXIS.  663 

The  anterior  extremity  advances  in  a  curve  to  near  the  optic  fossa. 

In  aged  animals,  there  are  sometimes  found  on  the  faces  of  the  falx 
cerebri,  especially  towards  its  posterior  extremity,  small  yellow  granules, 
known  as  the  Pacchionian  (/lands.  They  are  little  nuclei  of  connective 
tissue  that  arise  from  the  subarachnoideal  tissue  ;  meningeal  g7-anulations 
would  be  a  better  designation  for  them  than  that  of  glands. 

6.  The  tentoritim  cerebelli  is  composed  of  two  lateral  laminae,  which  form 
a  transverse  partition  between  the  cerebellum  and  the  posterior  extremities 
of  the  cerebral  lobes. 

Each  lamina,  coursed  internally  by  one  of  the  transverse  sinuses,  offers  : 
an  adherent  convex  border,  attached  to  the  parieto-temporal  crest ;  a  free 
concave  border,  turned  inwards  and  a  little  forwards,  remarkable  for  its 
thickness  and  solidity,  and,  with  the  second  lamina,  circumscribing  an  oval 
opening  through  which  the  encephalic  isthmus  passes  ;  a  superior  extremity, 
attached  to  the  parietal  protuberance ;  an  inferior  extremity,  which 
disappears  above  the  Gasserian  ganglion,  near  the  fold  that  surrounds  the 
pituitary  gland. 

Of  the  two  faces  of  these  laminae,  the  anterior  corresponds  to  the  cerebral 
lobes,  the  posterior  to  the  cerebellum. 

c.  The  sup'osphenoidal,  or  pituitary  fold,  is  a  thick,  slightly  salient,  and 
almost  circular  pad,  channeled  internally  by  the  cavernous  sinus,  and 
circumscribing  the  sella  turcica  by  enveloping  the  pituitary  gland  laterally 
and  posteriorly. 

2.  The  Arachnoid  Membrane. 

The  arachnoid  presents  the  same  disposition  as  all  the  splanchnic  serous 
membranes,  in  being  resolved  into  two  layers — a  parietal  and  a  visceral, 
both  constituting  a  perfectly  closed  sac,  outside  which  the  cerebro-spinal 
axis  is  contained.  The  cavity  of  this  sac  is  traversed  by  the  roots  of  nerves, 
the  vessels  of  the  brain  and  cord,  and  filaments  and  cellular  lamellfe  which 
pass  from  the  pia  mater  to  the  dura  mater ;  around  all  these  its  layers  form 
sheaths  by  becoming  continuous  with  one  another. 

Each  of  these  layers  exhibits  an  adherent  and  a  free  face.  The  adherent 
face  of  the  parietal  layer  is  united,  as  we  have  already  seen,  to  the  dura 
mater.  That  of  the  visceral  layer  covers  the  nervous  axis  in  spreading 
itself  over  the  pia  mater,  but  without  accompanying  it  into  the  anfractuosi- 
ties  of  the  central  mass ;  it  is  beneath  this  face  of  the  visceral  layer  that  the 
cerebro-spinal  (or  subarachnoid)  fluid  is  confined  in  spaces  which  will  be 
studied  hereafter.  By  their  free  face,  which  is  smooth  and  moist,  like  that 
of  all  serous  membranes,  the  arachnoid  layers  are  in  contact  with  each 
other. 

Structure. — The  structure  of  this  membrane  resembles  that  of  all  others 
of  the  same  nature.  The  meshes  of  elastic  fibres  are  most  abundant  in  the 
cranial  portion.  Everywhere  the  parietal  layer  is  only  composed  of  a 
simple  layer  of  epithelium.  The  arachnoid  has  no  proper  vessels  or 
nerves ;  those  which  pass  through  it  only  accompany  each  other. 

Spinal  Arachnoid  Membrank — The  parietal  layer  presents  nothing  of 
interest.  The  visceral  layer  is  separated  from  the  spinal  cord,  throughout 
its  extent,  by  a  somewhat  considerable  space  (the  subarachnoid),  in  which 
the  subarachnoid  fluid  is  collected ;  this  space  is  greatest  posteriorly, 
around  the  terminal  extremity  of  the  cord  and  the  nerves  of  the  cauda 
equina. 

The  adherent  face  of  this  membrane  is  only  connected  with  the  external 


664  ~     TEE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 

surface  of  the  spinal  cord  by  thin  cellular  filaments  detached  from  the  pia 
mater. 

Cranial  oe  Encephalic  Arachnoid. — There  is  nothing  special  to 
note  in  the  parietal  layer. 

If  the  visceral  layer  be  traced  from  the  occipital  foramen,  -nhere  it  is 
continuous  with  the  spinal  arachnoid,  to  the  anterior  extremity  of  the 
cerebral  lobes,  it  is  seen  to  be  prolonged  inferiorly  on  the  lower  face  of  the 
isthmus,  as  far  as  the  pituitary  stalk,  to  which  it  fui-nishes  a  sheath :  the 
pituitary  gland  itself  is  not  covered  by  the  arachnoid,  except  on  a  portion  of 
the  superior  or  deep  face  ;  from  the  isthmus  it  is  carried  forward,  and  extends 
on  each  side  of  the  cerebellum  and  cerebral  lobes.  Superiorly,  this  internal 
layer  sj)reads  over  the  surface  of  the  cerebellum,  and  is  reflected  at  the 
bottom  of  the  fissure  between  that  organ  and  the  cerebral  hemisj^heres, 
over  the  posterior  extremity  of  the  latter,  enveloping  them  separately  by 
descending  into  the  interlobular  fissure  as  far  as  the  corpus  callosum. 
Eeaching  the  anterior  extremity  of  the  cerebrum,  it  gains  the  olfactory 
lobes,  is  principally  prolonged  on  their  supero-posterior  face,  and  doubles 
around  the  ganglion  of  grey  substance  on  their  inferior  face,  to  be  con- 
tinued with  the  parietal  layer. 

In  covering  the  external  surface  of  the  encephalon,  the  cranial  arachnoid 
does  not  adhere  everywhere  to  the  nervous  substance,  but  is  only  slightly 
connected  with  it,  through  the  medium  of  the  pia  mater,  at  such  salient 
portions  as  the  summits  of  the  cerebral  convolutions.  Neither  does  it  dip 
down  to  enter  the  sulci  existing  between  these  parts,  but  i)asses  over  them, 
and  in  this  way  forms  a  large  number  of  subarachnoid  spaces  analogous  to 
that  developed  over  the  whole  extent  of  the  spinal  cord. 

These  spaces,  which  are  filled  by  the  subarachnoid  fluid,  differ  widely  in 
form  and  dimensions.  In  Man,  thi-ee  principal  have  been  described,  and 
these  are  also  found  in  animals ;  Magendie  has  named  them  the  confluents  of 
the  subarachnoid  fluid.  Of  these  three  confluents,  the  anterior  is  situated  in 
advance  of  the  chiasma  of  the  optic  nerves,  between  the  two  cerebral  lobes  ; 
the  inferior,  the  largest,  is  comprised  between  the  pituitary  stalk  and  the 
annular  protuberance  to  the  surface  of  the  peduuculi  of  the  cerebrum  ;  while 
the  third,  or  posterior  confluent,  lies  behind  the  cerebellum,  at  the  calamus 
scriptorius. 

None  of  these  spaces  communicate  with  the  internal  cavities  of  the  en- 
cephalon, and,  consequently,  the  subarachnoid  fluid  cannot  enter  them. 
Magendie  has  nevertheless  described  a  communication  between  the  pos- 
terior confluent  and  the  ventricle  of  the  cerebellum  ;  though  the  opening  he 
described  towards  the  calamus  scriptorius  has  not  been  found  in  the  Horse 
by  M.  Renault,  and  we  believe  we  may  afiii'm,  with  M.  Lavocat,  that  it  does 
not  exist  in  the  other  animals. 

The  Subarachnoid  Fluid. — The  fluid  contained  in  the  subarachnoid 
spaces  is  slightly  yellow  or  colourless,  and  perfectly  limpid  and  transparent. 
Some  authorities  admit  that  it  is  secreted  by  the  visceral  layer  of  the 
arachnoid,  and  others  by  the  pia  mater.  According  to  the  remark  made  by 
Cruveilhier,  the  nervous  centres  are  irmnersed  in  it,  like  a  foetus  in  the 
liquor  amnii;  and  this  remark,  which  is  particularly  applicable  to  the 
spinal  cord,  gives  the  key  to  the  use  of  this  fluid,  which  keeps  the  organ 
away  from  the  walls  of  the  spinal  canal,  deprives  it  of  the  greater  part  of 
its  weight  (Foltz),  and  thus  diminishes  every  kind  of  concussion  to  which 
it  might  be  exposed. 

(This  fluid,  so  necessary  for  the  support  and  protection  of  the  cord  and 


THE  CEREBROSPINAL  AXIS.  G65 

brain,  is  alkaline,  and  contains  but  a  small  quantity  of  albumen  ;  it  varies 
in  quantity  according  to  the  relative  size  of  the  cerebro-sijinal  axis  and  its 
containing  cavity,  or  with  the  amount  of  blood  sent  to  this  region.  By 
aflfording,  under  all  cii'cumstances,  an  equable  pressure  on  the  brain  and 
spinal  cord,  and  the  nerves  emanating  from  these,  its  importance  as  a  hydro- 
static agent  is  greatly  enhanced.) 

3.  Tlie  Pia  Mater. 

The  pia  mater,  the  proper  envelope  of  the  cerebro-spinal  axis,  is  a  thin 
membrane  whose  framework,  essentially  connective,  sustains  on  its  external 
face  a  very  abundant  network  of  blood-vessels  and  nerves. 

Applied  immediately  to  the  surface  of  the  encephalon  and  spinal  cord,  it 
adheres  lirmly  to  that  surface  and  follows  all  its  inequalities,  jjenetrating 
between  the  cerebral  or  cerebellar  convolutions,  and  forming  in  each  inter- 
mediate sulcus  two  layers  that  lie  against  each  other. 

The  external  face  of  the  pia  mater,  bathed  in  part  of  its  extent  by  the 
subarachnoid  fluid,  adheres  to  the  visceral  layer  of  the  arachnoid  by  means 
of  a  more  or  less  dense  and  close  filamentous  connective  tissue.  From  it 
arise  the  cellular  coverings  that  constitute  the  neurilemma  of  the  nerves. 
It  detaches  a  multitude  of  filamentous  or  lamellar  prolongations  to  the 
internal  face  of  the  dura  mater,  which  traverse  the  arachnoid  cavity  in  the 
same  manner  as  the  nerves  and  vessels,  by  being  enveloped,  like  these,  in  a 
sheath  furnished  by  the  arachnoid  membi'ane.  Always  very  short,  these 
prolongations  simulate  the  adhesions  established  between  the  two  layers  of 
that  membrane. 

The  internal  face  is  united  to  the  nervous  substance  by  multitudes  of 
arterial  and  venous  radicles  or  connective  fi.laments,  which  leave  the  pia 
mater  to  plunge  into  this  substance. 

The  vessels  of  the  pia  mater  form  a  very  close  network,  from  which  are 
detached  branches  that  reach  the  medulla  and  encephalon.  They  are  ac- 
companied by  nervous  filaments,  and  surrounded  hj  perivascular  canals,  which 
are  now  believed  to  be  lymphatics.  Certainly,  in  their  interior  a  colour- 
less fluid  circulates,  and  which  contains  globules  very  like  those  of  lymph. 

Spinal  Pia  Mater. — Less  vascular  than  the  cranial  pia  mater,  with 
which  it  is  continuous  towards  the  medulla  oblongata,  this  membrane  is 
remarkable  for  the  arrangement  of  the  prolongations  that  arise  from  its 
two  faces. 

The  internal  prolongations  form  longitudinal  laminae  at  the  fissures  of  the 
cord,  and  enter  these  fissures. 

The  external  prolongations  attach,  as  we  have  said,  the  pia  mater  to  the 
external  meninge.  A  very  large  number  are  filamentous  in  form,  and  are 
dispersed  over  the  superior  and  inferior  surfaces  of  the  cord.  Others  consti- 
tute, on  each  side  of  the  organ,  a  festooned  band  named  the  dentated  ligament 
(ligamentum  dentata,  or  denticulatum).  These  ligaments  exist  throughout  the 
entire  length  of  the  medullary  axis,  between  the  superior  and  inferior  nerve- 
roots  :  theii-  inner  border  is  confounded  for  its  whole  length  with  the  pia 
mater ;  and  their  outer  margin,  cut  into  festoons,  attaches  itself  to  the  dura 
mater  by  the  summit  of  the  angles  separating  these  festoons. 

To  complete  this  description  of  the  spinal  pia  mater,  there  may  be  noticed 
a  posterior  or  coccygeal  prolongation  (Jilum  terminale) :  a  very  narrow  process 
formed  by  this  membrane  at  the  posterior  extremity  of  the  cord,  situated  in 
the  midst  of  the  cauda  equina  nerves,  and  attached  to  the  bottom  of  the 
conical  cul-de-sac  at  the  termination  of  the  dura  mater. 


6G6  THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 

(This  ligament,  or  memhrana  dentata,  serves  to  maiutain  tlie  position  of 
the  spinal  cord  in  its  hydrostatic  bed,  and  to  prevent  the  nerves  proceeding 
from  it  being  dragged  during  flexion  of  the  spine.) 

Cranial,  or  Encephalic  Pia  Mater. — The  vascular  element  pre- 
dominates in  this  portion  of  the  internal  meninge. 

This  membrane  sends  scarcely  any  prolongations  to  the  dura  mater, 
except  at  the  medulla  oblongata,  though  it  projects  remarkably  large  ones 
into  the  cerebral  mass  and  the  sides  of  the  cerebellum.  The  descrijition  of 
the  velum  interpositum,  and  the  cerebral  and  cerebellar  plexus  choroides,  belongs 
to  the  encephalon. 

(The  pia  mater  is  extremely  vascular  on  the  surface  of  the  cerebrum,  and 
forms  remarkable  anastomosing  loops  in  the  intermediate  spaces  of  the 
convolutions,  which  chiefly  supply  the  grey  substance.  It  is  the  nutrient 
membrane  of  the  brain  and  spinal  cord.  Its  nerves  accompany  its  arterial 
branches,  and  are  minute  filaments  from  the  sympathetic.) 

differential  characters  in  the  enveloping  and  protective  parts  of  the  cerebro- 
spinal AXIS  IN  OTHER  THAN   SOLIPED  ANIMALS. 

The  oony  canal  that  protects  the  spinal  cord  and  brain  does  not  present  any  note- 
worthy differences  in  the  domesticated  animals,  and  the  subject  has  been  already 
sufficiently  studied  in  the  osteology  of  the  head  and  vertebral  column. 

With  regard  to  the  meninges,  their  number  and  general  disposition  are  the  same  in 
all  the  species. 

COMPARISON   OF   THE   ENVELOPING  AND   PROTECTIVE   PARTS   OF   THE   CEREBRO-SPINAL 
AXIS  OF  MAN   WITH   THOSE   OF   ANIMALS. 

There  is  nothing  particular  to  be  said  respecting  the  cranial  cavity  and  spinal  canal, 
nor  yet  the  arachnoid  and  pia  mater.  The  dura  mater  ofifers  the  folds  described  in 
Solipeds,  and,  in  addition,  ufalx  cerebellum,  thnt  extends  from  the  tentoriuni  of  the  same 
name  to  near  the  foramen  magnum.  The  meningeal  granulations,  or  Pacchionian  glamls, 
are  nearly  constant  in  aged  Individuals,  and  their  volume  is  sometimes  so  considerable, 
that  by  compression  they  thin  away,  aud  even  perforate,  the  cranium  at  corresponding 
points. 


CHAPTER  IL 

THE   SPINAL   CORD. 


Preparation. — Isolate  the  cranium  and  vertebral  column  from  all  the  6ther  parts  of  the 
body;  open  the  spinal  canal  and  the  cranial  cavity  by  their  superior  surface,  as  in 
figure 3] 6,  bv  raising  with  a  chisel  (or  rogne-pied,  the  farrier's  "toe-knife")  and  hammer, 
the  roof  of  the  skull  and  nnnular  portion  of  all  the  vertebrse.  The  organ  may  then  be 
studied  in  situ  in  its  bony  case,  and  surrounddl  by  its  membranes;  afterwards  extract 
the  whole  cerebro-spinal  axis  inclosed  in  the  dura  mater,  and  open  up  the  latter  along 
the  course  of  the  cord,  so  as  to  completely  expose  that  portion  of  the  nervous  system. 

(The  saw  and  farrier's  pincers,  or  spine  ratchet,  will  be  found  useful  auxiliaries  in  the 
tedious  and  delicate  operation  of  exposing  the  brain  and  cord ;  and  particularly  in  lay- 
ing open  the  cranial  cavity.  An  easy  mode  of  obtaining  access  to  the  spinal  canal  and 
its  contents,  is  to  saw  through  the  laminse  of  the  vertebra;  on  each  side,  at  the  roots  of 
the  transverse  processes,  and  raise  the  arches  with  the  chisel  or  toe-knife.) 

EXTERNAL    CONFORMATION    OF    THE    SPINAL    CORD. 

General  view. — The  spinal  cord  is  that  portion  of  the  nervous  centres  which 
occupies  the  spinal  canal.  It  is  a  thick,  white,  and  irregularly  cylindrical 
cord,  commencing  at  the  occipital  foramen,  where  it  continues  the  medulla 
oblongata,  terminating  in  a  point  at  the  upper  third  of  the  sacral  canal,  or  a 


TEE  SPINAL  CORD 

III 


667 


-B  < 


668  THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 

little  beyond  that,  and  giving  rise  at  each  side,  during  its  course,  to  the 
superior  and  inferior  roots  of  the  spinal  nerves. 

Weight.— ^In  medium- sized  animals  the  weight  of  the  cord  is  represented 
by  the  following  approximate  numbers :  for  the  Horse,  lOJ  ounces :  the  Ass, 
.5|-  ounces ;  Cow,  Tf  ounces ;  Sheep  and  Goat,  If  ounce ;  Pig,  2i  ounces ; 
Dog,  1^  ounces ;  Cat,  4^  drams. 

Figure  and  volume. — The  medullary  cord  is  slightly  depressed  above  and 
below,  throughout  its  whole  length ;  in  whatever  part  we  examine  a 
transverse  section  of  it,  we  will  always  find  the  lateral  diameter  greater  than 
the  vertical,  and  that  this  section  appears  regularly  elliptical. 

Its  volume  is  far  from  being  uniform.  In  following  it  from  before  to 
behind,  we  at  first  remark  that  it  presents  the  same  dimensions  to  the  fifth 
cervical  vertebra,  and  that  between  this  point  and  the  second  dorsal  vertebra 
it  forms  an  oblong  enlargement,  designated  the  brachial  (brachio-rachidian)  bulb 
or  enlargement.  Beyond  this,  it  assumes  its  primitive  volume,  and  becomes 
gradually  smaller  even  than  in  the  cervical  region.  Towards  the  middle  of 
the  loins,  it  again  augments  to  constitute  the  crural  (lumbo-rachidian)  bulb 
or  enlargement,  which  extends  to  the  entrance  of  the  sacral  canal.  After 
this  dilatation  comes  a  conical  prolongation,  whose  point  represents  the 
terminal  extremity  of  the  coud. 

If  we  compare  the  diameter  of  this  medullary  axis  with  that  of  the 
spinal  canal,  we  will  observe,  as  has  been  already  said,  that  the  capacity  of  the 
containing  r^avity  is  generally  related  to  the  volume  of  its  contents,  and  that 
the  former  is,  as  a  rule,  most  capacious  at  the  cervical  and  lumbar  enlarge- 
ments. It  will  even  be  noticed  that  the  dilatation  the  spinal  canal  offers  at 
these  two  points,  is  relatively  more  considerable  than  the  excess  in  volume  of 
the  cord.  This  is  because  the  mobility  of  the  spine,  which  is  justly  very 
great  in  these  two  regions,  requires  this  diiference  to  secure  the  spinal  axis 
from  contusions  during  the  movements  executed  by  the  vertebral  column. 
This  protective  combination  is  also  found  elsewhere :  at  the  atlas,  for 
example,  where  we  know  the  motion  is  considerable;  and  in  the  entire 
extent  of  the  cervical  region,  which  in  this  respect  greatly  exceeds  the 
dorsal  region. 

External  surface  of  the  cord. — Covered  by  the  pia  mater,  this  surface 
presents  an  extremely  simple  disposition.  On  its  superior  and  inferior 
planes,  at  each  side,  we  remark  the  double  series  of  sensitive  and  motor 
roots  of  the  spinal  nerves,  which  are  implanted  in  the  same  longitudinal 
line  to  right  and  left  of  the  median  plane,  and  are  collected  in  fasciculi 
opposite  the  intervertebral  foramina. 

In  the  middle  line,  and  throughout  the  entire  length  of  the  organ,  there 
are  two  deep  and  narrow  fissures :  one  superior  (fissura  longitudinalis 
superior),  the  other  inferior  (fissura  longitudinalis  inferior),  into  which  the 
pia  mater  enters.  Four  other  fissures  have  been  described  at  the  point  of 
emergence  of  the  nerve  roots,  under  the  names  of  superior  and  inferior 
collateral  fissures  (or  sulci);  but  the  two  superior  alone  exist,  and  even 
these  are  often  scarcely  noticeable. 

INTERNAL   CONFORMATION    AND    STRUCTURE    OF    THE    SPINAL    CORD. 

In  making  a  transverse  section  of  any  portion  of  the  cord,  we  may 
convince  ourselves  that  it  has  an  internal  cavity.  This  central  canal  is 
elliptical,  and  lined  by  cylindrical  ciliated  epithelium,  resting  on  a  thin 
connective  membrane,  the  ependymis  of  Virchow.     This  section  also  shows 


THE  SPINAL  COED. 


C69 


the  two  median  fissures  mentioned  in  describing  the  exterior  of  the  cord, 
the  inferior  of  which  is  wider  and  deeper  than  that  of  the  superior,  whose 
situation  is  scarcely  perceptible. 

These  two   fissures  advance  one   before   the   other,  and   do   not  meet 
so    as   to    completely   divide    the 

cord  into  two   lateral  halves,  but  ^* 

remain  separated  by  two  thin 
horizontal  and  superposed  bands 
of  nervous  matter,  that  pass  from 
one  end  to  the  other  of  the  me- 
dullary axis.  The  inferior,  formed 
of  white  substance,  corresponds  to 
the  bottom  of  the  inferior  fissure ; 
while  the  superior,  composed  of 
grey  matter,  meets  the  superior 
fissure. 

These  bands  are  named  the 
ichite  and  fjrey  commissures  of  the 
spinal  cord  (Fig.  318). 

Notwithstanding  the  presence 
of  these  two  commissures  between 
the  lateral  halves  of  the  spinal 
axis,  these  latter  do  not  the  less  con- 
stitute two  symmetrical  systems, 
whose  structure  will  now  be 
studied. 

Each  medullary  cord  repre- 
sents a  semi-cylinder  of  white  sub- 
stance, in  the  centre  of  which  is 
a  mass  of  grey  matter,  that  varies  somewhat  in  quantity  in  different  regions, 
but  the  arrangement  of  which  is  everywhere  the  same.  Thus,  inwardly,  this 
grey  matter  joins  the  grey  commissure  ;  above,  it  sends  off  a  thin  jjrolongation 
which  traverses  the  thickness  of  the  medullary  cord  (sujierior  grey  cornu), 
to  reach  the  bottom  of  the  superior  collateral  fissure ;  below,  it  gives 
rise  to  an  analogous,  thoiTgh  a  thicker  and  a  more  irregular,  prolongation 
(inferior  grey  cornu),  which  is  directed  well  in  front  of  the  inferior  roots, 
but  does  not  reach  the  surface  of  the  cord.  In  consequence  of  this  arrange- 
ment, the  grey  substance  of  the  medulla  forms  altogether  a  kind  of  capital 
H,  whose  horizontal  branch  is  •perforated  in  the  middle  by  the  centra] 
canal. 

This  disposition  of  the  grey  substance  causes  the  white  matter  to  be 
divided,  in  each  lateral  moiety  of  the  spinal  axis,  into  three  cords  or 
secondary  columns ;  the  superior  of  these  is  perfectly  isolated,  and  is  com- 
prised between  the  middle  sujierior  fissure  and  the  origin  of  the  sensitive 
roots  ;  another,  the  inferior,  united  to  that  of  the  opposite  side  by  the  white 
commissure,  is  limited,  inwardly,  by  the  inferior  median  fissure,  and  out- 
wardly by  the  line  of  origin  of  the  motor  nerve-roots ;  while  a  third,  the 
lateral  or  intermediate,  thicker  than  the  others,  is  confounded  superficially 
with  the  inferior,  and  formed  by  all  that  portion  of  the  medulla  situated 
between  the  lines  of  origin  of  the  superior  and  inferior  roots.  Of  these 
three  columns  of  the  medullary  axis,  the  first  is  sensitive ;  the  other  two, 
which  in  reality  are  only  one,  are  motor, 

Steucture. — Independently  of  the  epithelium  mentioned  when  describing 


SECTION  OP  THE  SPINAL  CORD  OF  THE  HORSE 
AT  THE  LUMBAR  REGION;  MAGNIFIED  TWO 
DIAMETERS. 

1,  Superior  median  fissui-e ;  2,  Inferior  median 
fissure ;  3,  3,  Superior  collateral  fissures ; 
4,  4,  Inferior  ditto ;  5,  Grey  commissure ;  6, 
White  commissure ;  7,  7,  Superior  grey  cor- 
nua ;  8,  8,  Inferior  grey  cornua ;  9,  Central 
canal. 


G70 


THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 


the  ependymis,  connective  tissue,  nerve  tubes,  nerve  cells,  and  vessels  enter 
into  the  structure  of  the  medulla. 

The  connective  tissue  of  the  sjiinal  cord  is  very  delicate,  rich  in  nuclei,  and 
belongs  to  the  variety  that  histologists  have  named  ''  reticular  "  or  "  adenoid." 

It  appears  to  arise  from  the  pia  mater,  and  forms  lamellfB  that  i)enetrate 
the  nerve-substance  to  meet  and  anastomose  with  each  other,  and  finally 
become  confounded  with  the  ependymis  around  tbe  central  canal.  This 
tissue,  which  is  also  named  neuroglia,  has  been  compared  to  a  sponge,  in 
whose  sj)aces  ai-e  deposited  the  other  elements  of  the  cord.  This  neuroglia 
exists  in  the  white  and  grey  substances,  but  is  more  abundant  in  the  superior 
than  in  the  inferior  grey  cornua.  It  surrounds  the  upper  extremity  of  the 
former  in  becoming  softer  and  more  trausjiarent,  and  is  here  designated  the 
gelatinous  substance  qf  Rolando  (substantia  gelatinosa).  It  constitutes,  in 
great  part,  the  grey  commissure,  and  can  be  deeply  stained  by  the  corminate 
of  ammonia. 

Fis.  319. 


TKANSVERSE  SECTION  OF  SPINAL  CORD  OF  MAN  THROUGH  THE  MIDDLE  OF  THE 
LUMBAR  REGION,  SHOWING  ON  THE  RIGHT  SIDE  THE  COURSE  OF  THE  NERVE- 
ROOTS,  AND  ON  THE  LEF.T  THE  POSITION  OF  THE  PRINCIPAL  TRACTS  OF  VESICULAR 
MATTER. 

A,  A,  Anterior  01- inferior  columns;  P,  p,  Posterior  or  superior  columns  ;  L,  L,  Lateral 
columns. — a,  Anterior  or  inferior  median  fissure ;  p,  Posterior  or  superior  median 
fissure ;  6,  h,  5,  b.  Anterior  or  inferior  i-oots  of  spinal  nerves ;  c,  c.  Posterior  or 
superior  roots;  d,  £?, 'Tracts  of  vesicular  matter  in  anterior  column;  e,  Tracts  of 
vesicular  matter  in  posterior  column  ;  /,  Central  canal ;  g,  Substantia  gelatiuosa. 

The  tubes  and  cells  form,  with  the  neuroglia,  the  whole  of  the  grey 
substance.  The  cells  have  at  least  five  prolongations,  and  the  tubes  are 
reduced  either  to  the  axis-cylinder  (axis-fibre),  or  to  this  and  a  very  thin 
layer  of  medullary  substance. 

The  cells  are  not  uniformly  distributed  in  the  grey  substance,  but  are 
arranged  in  small  masses  that  constitute  three  longitudinal  columns :  two 


TEE  SPINAL  COED. 


671 


Fiff.  320. 


in  the  inferior,  and  one  in  tlie  superior  grey  coruu.  The  columns  cor- 
resjiond  to  wliat  Stilling  has  named  the  nuclei  of  the  nerves.  A  foui-th 
mass  of  cells,  the  superior  vesicular  column 
of  Clarice,  or  dorsal  nucleus  of  Stilling,  is 
observed  at  the  point  where  the  grey  com- 
missure joins  the  cornua.  The  nerve-tubes 
(or  tubules)  affect  longitudinal,  transversal, 
oblique,  and  vertical  directions. 

They  bring  the  cells  of  one  lateral 
moiety  of  the  medulla  into  communication 
with  :  1,  The  tubes  of  the  white  substance  ; 
2,  Each  other  ;  3,  The  cells  of  the  opposite 
moiety,  by  passing  into  the  commissures ; 
4,  The  tubes  of  the  white  substance  of  the  op- 
posite moiety,  by  foHowing  the  same  course. 

The  neuroglia  and  nerve-tubes  consti- 
tute the  white  substance,  which  is  decom- 
posed, as  we  know,  into  three  cords.  All 
the  tubes  of  this  substance  do  not  ascend 
to  the  brain,  as  was  believed  for  a  long  time  ; 
the  opinion  that  the  tubes  of  the  spinal 
nerves  formed  the  medulla  and  extended  to 
the  brain,  has  been  abandoned  since  Volk- 
mann  measured,  comparatively,  the  section 
of  all  these  nerves  and  that  of  the  nervous 
spinal-axis. 

(Volkmaun  has  established  the  fact,  that 
the  size  of  the  medulla  corresponds  with  the 
number  of  nerve-tubes  given  off  at  any  point. 
He  gives  the  weight  of  four  segments,  each 
2y^  inches  in  length,  from  the  spinal  cord 
of  the  Horse,  and  the  relative  extent  of  the 
grey  matter  in  square  lines ;  these  are  as 
follows 


Area 

Area 

Grains. 

of  Grey- 

of  White 

Ma  Iter. 

Matter. 

rom  below  2nd  Spinal  Nerve,  219 

13 

109 

Sth      „          „      293 

28 

142 

„      19th      „          „       163 

11 

89 

,,         >.      30tli      „          „       2«1 

25 

121) 

LONGlTtTDINAL  SECTION  THROUGH 
CERVICAL  ENLARGEMENT  OF  SPINAL 
CORD    OF    CAT. 


In  the  white  substance  the  tubes  are  lon- 
gitudinal, oblique,  or  transversal ;  the  latter 
arise  from  the  cells  of  the  grey  substance, 
and  represent  the  roots  of  the  nerves  ac,  Interior  white  columns ;  ac',  Por- 
emerging  either  by  the  superior  or  inferior  tion  showing  the  arrangement  of 
collateral  fissure.  the    longitudinal   fibres,    PC,Pos. 

mi       J    1  1.   ,1  ,      '  1  ,  tenor    white    columns:    G,    hvej 

The   tubes  of  the  anterior  cords  pass   to        substance  between  them  (the  vesicles 

being  omitted  to  avoid  obscuring 
the  course  of  the  fibres) ;  A,  Anterior  roots  of  the  nerves  ,  P,  Posterior  roots,  consisting 
of  three  kinds :  the  first,  a,  crossing  the  posterior  columns  horizontally,  and  then  pass- 
ing obliquely  downwards,  across  the  grey  substance,  into  the  anterior  columns ;  the 
second,  6,  traversing  the  posterior  columns  horizontally,  and  then  losing  themselves 
in  the  grey  substance;  the  third,  c,  for  the  most  part  becoming  continuous  with  the 
longitudinal  fibres  of  the  posterior  column ;  all,  or  nearly  all,  ultimately  entering  the 
grey  substance. 


672  THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 

the  cells  of  the  grey  substance,  or  reach  the  encephalon  by  remaining  in  the 
corresponding  moiety  of  the  medulla ;  for  instance,  the  fibres  of  the  right 
half  of  the  medulla  gain  the  brain  without  passing  into  the  left  half. 
Those  of  the  lateral  cords  decussate,  each  cord  sending  to,  and  receiving 
from,  the  other,  tubes  which  cross  in  the  white  commissures.  The  posterior 
cords  contain  fibres  that  extend  directly  to  the  brain :  these  are  sensorial ; 
there  are  also  found  transverse  fibres  that  enter  the  cells  of  the  superior 
grey  cornua,  and  others  that  pass  into  the  cells  of  the  inferior  or  motor 
cornua. 

Such  is,  in  a  few  words,  the  disposition  of  the  nerve-elements  in  the 
medulla.  The  subject  is  a  very  long  and  complicated  one,  which  cannot 
be  dealt  with  in  a  more  detailed  manner  in  a  work  on  descriptive  anatomy. 

Vessels. — The  medulla  receives  arteries  from  the  ramifications  of  the 
pia  mater.  The  grey  is  richer  in  vessels  than  the  white  substance ;  the 
latter  is  penetrated  everywhere  by  a  large  number  of  minute  arteries ;  while 
the  first  is  traversed  by  the  divisions  of  an  artery  that  is  thrown  off  by  the 
median  spinal,  and  ascends  towards  the  bottom  of  the  inferior  fissure.  The 
veins  follow  the  arteries,  and  constitute  two  somewhat  voluminous  vessels 
that  pass  along  the  grey  commissure,  to  the  right  and  left  of  the  central 
canal. 

DIFFERENTIAL  CHARACTERS  IN  THE  SPINAL  CORD  OF  OTHER  THAN  S0L7PED  ANIJIALS. 

In  all  the  species,  the  white  and  grey  substances  affect  the  disposition  above  de- 
scribed; only  some  slight  differences  in  the  reciprocal  volume  of  each  have  been 
remarked.  As  in  the  Horse,  the  spinal  medulla  does  not  extend  beyond  the  sacral 
region;  its  length  has  no  relation  to  that  of  the  coccygeal  region,  as  certain  anatomists 
would,  in  principle,  establish;  in  the  rabbit,  for  example,  the  tail  of  which  is  very 
short,  the  spinal  cord  is  prolonged  into  the  coccygeal  vertebrae. 

COMPARISON  OP  THE  SPINAL  CORD  OP  MAN  WITH  THAT  OF  ANIMAI,S. 

The  spinal  medulla  of  the  adult  Man  does  not  reach  beyond  the  first  lumbar  vertebra, 
though  in  the  fcetus  it  is  in  the  coccyx.  It  is  rounder  than  in  the  Horse,  and  the  grey 
substance  is,  relative  to  the  white,  more  abundant  than  in  the  spmal  cord  of  the  domes- 
ticated animals.  The  posterior  grey  cornua  are  also  larger  and  less  elongated  than  the 
superior  cornua  in  the  Horse ;  and  the  roots  of  the  nerves  are  also  more  voluminous. 


CHAPTEE  III. 
THE  ENCEPHALON. 

Article  I. — The  Encephalon  as  a  Whole. 

The  encephalon  is  that  portion  of  the  nervous  system  which  is  lodged  in 
the  cranial  cavity.  It  succeeds,  without  any  line  of  demarcation,  the  spinal 
cord,  of  which  it  may  be  considered,  with  regard  to  its  figure,  as  a  kind  of 
efflorescence. 

General  form  and  constitution. — In  shape  it  is  an  ovoid  mass,  elongated 
from  before  to  behind,  and  very  slightly  depressed  from  above  to  below. 

When  it  is  viewed  on  its  superior  face  (Fig.  321),  we  first  see,  behind,  a 
white  pedicle,  the  prolongation  of  the  spinal  cord,  and  a  single  lobe  of  a 
grey  colour  designated  the  cerebellum.  In  front  of  this  is  remarked  two 
other  lobes,  separated  from  the  first  by  a  deep  transverse  fissure,  into  which 


THE  ENCEPHALON. 


67S 


the  tentorium  of  tlio  cerebellum  passes.  Isolated  from  one  another  on 
the  middle  line  by  a  shallower  fissure,  these  two  lobes  constitute  the  hrain, 
and  are  usually  named  the  cerebral  hemispheres. 

In  turning  over  the  encephalon  Pio-,  321. 

to  examine  its  inferior  face,  we  see 
that  the  posterior  peduncle  of  the 
organ — a  continuation  of  the  spinal 
cord — is  prolonged  beneath  the  ce- 
rebellum, which  is  joined  to  the 
lateral  parts  of  its  superior  face ; 
this  portion  then  enters  the  cere- 
bral hemispheres  by  their  inferior 
face,  behind  two  thick  white  cords — 
the  optic  nerves,  which  mark  the 
anterior  limit  of  this  prolongation 
(Fig.  322).  This  is  the  isthmus  of 
the  encephalon :  a  name  given  to  it 
because  it  actually  forms  an  inter- 
mediate bond  between  the  three 
enlargements  which  form  the  prin- 
cipal mass  of  the  encephalon. 

The  cranial  jjortion  of  the  cen- 
tral nervous  mass  is,  then,  com- 
posed of  three  apparatus :  the 
isthmus  of  the  encephalon,  a  pro- 
longation of  the  spinal  cord ;  and 
the  cerebellum  and  cerebrum,  bulbous 
lobes  grafted  on  the  superior  face 
and  anterior  extremity  of  this  pe- 
duncle. These  three  divisions  are 
very  well  seen  in  their  entirety 
and  reciprocal  relations  in  Figure 
329.  We  will  study  them  sepa- 
rately and  in  succession. 

Volume  of  the  encephalon. —  Con- 
trary to  what  is  found  in  the  spinal 
cord,  the  dimensions  of  the  en- 
cephalon closely  represent  those 
of  the  cavity  containing  them  :  the 
visceral  layer  of  the  arachnoid  lying  everywhere  immediately  on  the  proper 
envelope  of  the  nervous  mass,  the  pia  mater,  excejit  at  the  subarachnoid 
spaces ;  and,  on  the  other  hand,  the  arachnoid  cavity  can  scarcely  be  said 
to  exist  while  the  dura  mater  is,  as  it  were,  glued  to  the  cranial  walls,  and 
in  reality  constitutes  their  internal  periosteum. 

The  encephalon  has,  therefore,  no  room  to  move  in  its  receptacle,  but  is 
maintained  in  it  in  an  almost  absolutely  immovable  condition,  which 
coincides  exactly  with  that  of  the  sutures  or  cranial  articulations. 

Weight. — The  total  weight  of  the  encephalon,  in  average-sized  animals, 
may  be  inferred  from  the  following  figures  :  Horse,  22  oz.  15  drams ;  Ass,  12 
oz.  11  drams ;  Ox,  16  oz.  15  drams ;  Sheep  and  Goat,  4  oz.  9^  drams;  Pig, 
5  oz.  10  drams ;  Dog,  6  oz,  5^  drams ;  Cat,  1  oz.  1  dram. 

In  comparing  these  figures  with  those  of  the  sjiinal  cord,  it  will  be  seen 
that  the  relative  weight  of  the  medidlary  axis  to  that  of  the  encephalic  mass 


GENERAL  VIEW  OF  THE  BRAIN ;  TIPPER  SURFACE. 

1,  Medulla  oblongata;  2,  Middle  lobe  of  the 
cerebellum  ;  3,  3,  Lateral  lobes  of  ditto  ;  4,  4, 
Cerebral  hemispheres  ;  5,  Inteiiobular  fissure  ; 
6,  6,  Ethmoidal  lobules. 


674  THE  CENTBAL  AXIS  OF  THE  NERVOUS  SYSTEM. 

differs  notably  in  tbe  several  animals,  being  bigbest  in  tbe  Dog.  Tbe 
relations  in  eacb  species,  between  tbe  two  divisions,  are  tbe  following  ;  Dog, 
1 :  5,14  ;  Cat,  1 :  3,75  ;  Sbeep  and  Goat,  1 :  2,60 ;  Ass  1  :  2,40 ;  Pig,  1 : 
2,30 ;  Horse  1  :  2.27 ;  Ox,  1  :  2,18.  We  give  tbese  numbers,  as  it  bas 
always  been  attempted  to  establish  in  tbe  predominance  of  tbe  eucepbalon 
tbe  cause  of  tbe  development  of  intelligence,  and  tbat  tbe  best  measure  of  tbis 
predominance  is  really  tbe  relation  of  tbe  spinal  axis  to  tbe  encepbalic  mass. 
It  bas  also  been  attempted  to  measure  tbis  predominance  of  tbe  encepbalon  by 
comparing  its  weigbt  with  tbat  of  tbe  entire  body  ;  but  it  is  sufficient  to  cast 
one's  eye  over  tbe  tables  drawn  up  witb  tbis  view  in  several  anatomical  and 
pbysiological  works,  to  be  convinced  tbat  tbis  basis  does  not  possess  all  the 
value  desirable. 

Preparation  of  the  encephalon. — To  study  the  encepbalon,  it  is  necessary  to  extract  it 
from  its  bony  receptacle ;  a  result  acliieved  in  two  ways.  The  first  consists  in  opening 
the  roof  of  the  cranium  by  hammer  ami  chisel,  after  removing  from  its  exterior  all  the 
parts  covering  it,  or  which  are  iu  its  vicinity.  The  dura  mater  is  then  excised  with 
scissors,  and  the  encephalon,  which  is  thus  directly  reached,  is  completely  isolated  by 
raising  its  posterior  extremitj',  and  cutting  from  behind  to  before  all  the  nerves  passing 
through  the  foramina  at  the  base  of  the  cranium,  with  the  pituitary  stalk,  as  well  as  the 
extremity  of  the  olfactory  lobes.  This  method  is  very  expeditious,  but  it  sacrifices  the 
pituitary  gland,  which  remains  firmly  incrusted  in  the  sella  turcica :  an  inconvenience 
we  obviate  by  resorting  to  the  second  procedure.  In  this,  the  cranium  is  opened  by  its 
base  or  floor,  after  separating  the  head  from  the  trunk,  cutting  away  the  lower  jaw, 
tongue,  and  os  hyoides,  and  excising  all  the  soft  parts  so  as  to  expose  the  bony  surfaces. 
The  head,  thus  prepared,  is  held  by  an  assistant,  the  roof  of  the  cranium  resting  on  a 
table  or  block.  Armed  with  a  chisel  and  hammer,  the  operator  first  removes  the 
zygomatic  arches  and  styloid  processes  of  the  occipital  bone,  then  the  condyles  of  this 
bone,  the  basilar  processes,  and  the  sphenoid,  palate,  and  ethmoid  bones,  returning  to  the 
lateral  portions  of  the  cranium,  which  are  chiselled  away  in  succession  from  the  occipital  to 
the  ethmoid  bones.  The  encephalon  being  sufficiently  exposed,  is  relieved  from  its  dura 
mater  as  in  the  first  metliod,  and  raised  in  the  left  hand  to  destroy,  by  means  of  scissors 
held  in  the  right  hand,  the  attachments  which  yet  fix  it  to  the  cranial  roof,  and  which 
are  cliiefly  the  veins  that  open  into  the  sinuses  of  the  dura  mater.  In  afterwards  ex- 
cavating the  ethmoidal  fossaj  with  the  point  of  a  scalpel,  the  olfactory  lobes  are  detached, 
and  the  nervous  mass  is  free.  This  procedure  is  more  difficult  than  the  first,  but 
possesses  several  advantages  over  it ;  for  not  only  do  we  preserve  the  pituitary  gland,  but 
have  the  ethmoidal  lobes  more  intact,  and  may  also  have,  if  desired,  the  ganglia  of  the 
cranial  nerves,  with  a  more  or  less  considerable  portion  of  tiie  nerves  themselves. 

After  indicating  the  methods  for  extracting  the  encephalon  from  its  bony  case,  we 
ought  to  say  some  words  as  to  the  course  to  be  pursued  in  order  to  study  it  successfully. 
To  do  this  it  is  advantageous  to  have  two  brains ;  one  of  these  should  be  hardened  by 
steeping  it  for  some  weeks  in  alcohol  (or  methylated  spirit),  or  in  water  to  which  has 
been  added  a  tenth  part  of  nitric  acid.  This  hardening  contracts  the  nervous  substance, 
and  causes  the  cavities  and  reliefs  to  appear  more  manifest.  (It  is  a  good  plan  to  place 
the  brain,  base  uppermost,  in  a  suitable  vessel,  and  if  a  piece  of  cloth  be  spread  beneath 
it,  its  removal  therefrom  will  be  greatly  facilitated.) 

"We  commence  by  examining  rapidly  the  whole  apparatus,  and  pass  immediately  to 
the  study  of  the  isthmus,  of  which  it  is  necessary  to  have  at  first  a  well-defined  idea. 
We  therefore  take  a  hardened  specimen,  and  isolate  this  portion  of  tlie  encephalon  in 
the  manner  represented  in  figure  323  ;  to  do  this,  it  suffices  to  cut  through  the  peduncles 
of  the  cerebellum,  and  excise  the  cerebral  hemispheres  upwards  and  backwards ;  the 
remains  of  these  and  the  cerebellum  should  be  preserved  for  an  analysis  of  their 
structure.  The  isthmus  thus  isolated  is  fitted  for  an  examination  of  its  external  confor- 
mation and  its  internal  cavities :  the  ventricle  of  the  optic  layers  and  the  aqueduct  of 
Sylvius,  into  which  we  may  penetrate  by  a  superior  longitudinal  incision. 

After  the  isthmus,  the  cerebellum  is  to  be  studied  :  in  its  external  conformation,  on  an 
Intact  specimen  ;  and  in  its  internal  conformation  and  structure  on  the  incised  piece. 

We  terminate  with  the  cerebrum,  whose  superficies  is  soon  examined,  and  whose 
interior  should  be  studied  in  the  following  manner  : — It  is  necessary  to  begin  by  demon- 
strating the  existence  of  ventricles  in  the  olfactory  lobes,  and  their  communication 
with  all  the  other  internal  cavities  of  tlie  brain,  which  can  easily  be  done  by  the  in- 
flation of  one  of  these  organs  by  means  of  a  straw  (or  dissecting-case  tube)  which 


TEE  ISTHMUS.  675 

raises  the  pitnitarv  gland,  the  cerebral  lobes,  and  the  cerebellum.  Then  we  pass  to  the 
corpus  callosimi,  which  is  exposed,  as  in  figure  330,  by  a  horizontal  section  of  the  hemi- 
spheres across  the  centrum  ovale.  The  corpus  callosum  of  each  side  is  afterwards 
excised  on  the  median  line  to  reach  the  interior  of  the  lateral  ventricles,  and  this  great 
commissure  of  the  brain  ought,  after  studjing  tlie  septum  lucidum,  tube  cut  across iu  the 
middle  and  turned  over,  as  in  tigure  331,  so  as  to  show  the  cerebral  trigonal  ,  fornix).  The 
foramen  of  Monro  is  next  examinetl,  then  the  corpus  striatum,  hippocampi,  trenia  semi- 
circularis,  choroid  plexus,  and  velum  interpositum.  which  are  expi  sed  by  the  ablation  of 
the  hippocampi  and  ti-ii<onal.  Lastly,  we  return  to  the  f('r.(men  of  Monro  to  study  its 
communication  with  the  ventricle  of  the  optic  layers ;  it  will  be  well,  also,  to  again  ex- 
amine the  latter,  as  well  as  the  aqueduct  of  Sylvius  and  the  vt-ntricie  of  the  cerebellum, 
which  we  arrive  at  in  dividing  the  organ  tlirough  the  middle  and  separating  the  halves. 

Two  longitudinal  and  vertical  sections,  one  median  (Fig.  327),  the  other  at  the  side 
(Fig.  329  .  will  not  be  without  utility  in  the  study  of  these  particulars.  They  may  be 
made  by  means  of  a  saw,  the  braiu  remaining  inclostd  in  the  cranial  cavity. 

(A  long-useful  implement  for  removing  the  bony  casing  of  the  brain  without  risk  of 
injuring  it,  is  a  chisel  whose  thin  cutting  edge  is  jligiitly  concave,  the  corners  being 
smooth  and  rounded,  and  projecting  beyond  the  cutting  edge.) 

Aeticle  II. — The  IsxHiius. 

We  will  study  in  succession  the  external  and  internal  conformation  of 
this  organ,  and  its  structure. 

EXTERNAL  COXFOEMATIOX  OF  THE  ISTHMUS. 

The  isthnus  is  a  prismatic  prolongation  of  the  spinal  cord  supporting  the 
cerebellum,  and  terminating  in  the  cerebral  hemispheres ;  it  increases  in 
size  from  behind  to  before,  and  may  be  considered  as  having  four  faces  and 
two  extremities. 

The  inferior  face  (Fig.  322).  on  which  we  can  distinctly,  and  without  any 
preparation,  perceive  the  natiu-al  limits  of  the  isthmus,  is  crossed  nearly  in 
its  middle  by  a  thick  fasciculus  of  arciform  fibres,  which  constitute  the 
annular  protuberance  (protuherantia  annularis),  pons  Varolii,  or  mesocephalon 
(or  nodus  encephaJi  i.  All  the  portion  lying  behind  this  fasciculus  belongs 
to  the  rachidian  bulb  (bulbus  rachidicus  or  medulla  oblongata).  That  in  front 
forms  the  cerebral  peduncles  {crura  cerebri). 

The  superior  face  (Fig.  323),  covered  by  the  cerebellum  and  the 
posterior  extremity  of  the  cerebral  lobes,  is  more  mammillated  than  the  pre- 
ceding. Passing  from  behind  to  before,  on  the  superior  face  of  the  medulla 
oblongata,  there  is  remarked  the  section  of  the  peduncles  of  the  cerebellum,  the 
ralve  of  Vieutsens,  the  corpora  quadrigemina,  and  the  ojitic  layers  (thalami  optici). 

The  Icderal  faces  (Fig.  324 ),  concealed  in  their  anterior  part  by  the 
hemispheres  of  the  brain,  exhibit  the  profile  of  the  medulla  oblongata,  pons 
Varolii,  peduncles  of  the  cerebellum  (crura  cerebelli),  cerebral  peduncles 
{crura  cerebri),  corpora  quadrigemina,  and  thalami  optici. 

The  posterior  extremity  of  the  isthmus  belongs  to  the  medulla  oblongata,  and 
continues  the  spinal  cord,  from  which  it  is  only  distingtiished  artificially. 

The  anterior  extremity  is  enveloped,  below  and  on  each  side,  by  the 
oblique  fasciculi  which  form  the  two  optic  nerves,  and  beneath  which  are 
insinuated  the  fibres  of  the  isthmus  before  they  pass  into  that  pai't  of  the 
cerebral  hemispheres  which  bears  the  name  of  corpora  striata. 

After  this  enumeration  of  all  the  organs  whose  aggregation  constitutes 
the  isthmus  of  the  encephalon,  we  will  examine  them  in  detail,  and  in  the 
following  order :  1,  Medulla  oblongata  ;  2,  Pons  Varolii ;  3,  Crura  cerebri ; 
4,  Crura  cerebelli;  5,  Valve  of  Vieussens ;  6,  Corpora  quadrigemina; 
7,  Thalami   opAici.     After  these,  we  will  describe  the  pineal  and  pituitary 


676 


THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 


Fis-.  322. 


glands :  small  appended  lobes  placed  one  on  tlie  superior,  the  other  on  the 
inferior  face  of  the  isthmus.' 

Medulla  Oblongata.     (Figs.  323, 
324,  829.) 

The  medulla  oblongata  constitutes 
the  posterior  portion  of  the  encephalic 
isthmus ;  it  succeeds  the  spinal  cord, 
and  extends  forward  as  far  as  the  pons 
Varolii.  It  is  a  thick  peduncle  of  a 
white  colour,  wider  before  than  behind, 
flattened  above  and  below,  and  having 
four  faces — an  inferior,  superior,  and 
two  lateral. 

Inferior  face  (Fig.  322).— This 
face  rests  in  the  channel  of  the  basilar 
process.  Convex  from  side  to  side, 
and  limited  anteriorly  by  a  transverse 
fissure  which  separates  it  from  the 
pons  Varolii,  posteriorly  it  does  not 
oifer  anything  to  distinguish  it  from 
the  medullary  axis. 

On  the  middle  line  there  is  a  well- 
marked  fissure,  a  continuation  of  tlie 
inferior  fissure  of  the  cord,  which  lies 
between  two  very  elongated  promi- 
nences that  are  sometimes  but  little 
apjjarent,  and  from  their  form  are 
named  the  pyramids  of  the  bulb  (corpora 
pyramidalia)  (Figs.  322,  19;  338,  6). 
The  base  of  these  j)yraniids  touches 
the  pons  Varolii,  and  their  apex  is 
insensibly  lost,  posteriorly,  on  reach- 
ing the  spinal  cord. 

Outwardly  is  an  almost  plane  sur- 
face, bordered  anteriorly  by  a  trans- 
verse band  which  lies  immediately 
behind  the  pons  Varolii ;  sometimes 
it  is  covered  for  the  greater  part  of  its 
extent  by  a  very  thin  expansion  of 
arciform  fibres,  between  the  anterior 
border  of  which  and  the  transverse 


GENERAL   VIEW   OF   THE   BRAIN  ;   LOWER 
SURFACE. 

1,  Olfactory  lobe ;  2,  Cavity  of  the  olfactory 
lobe ;  3,  External  root  of  olfactory  lobe ; 
4,  5,  Cerebral  hemispheres  ;  6,  Cerebellum  ; 
7,  Optic  chiasma,  or  commissure ;  8,  Pitui- 
tary gland;  9,  Optic  nerves;  10,  Tuber 
cinereum ;  11,  Crus  cerebri;  12,  Third 
cranial  nerve  ;  13,  Fourth  nerve  ;  14,  Pons 
Varolii;  15,  Fifth  nei've ;  16,  Sixth  nerve; 
17,  Seventh  and  eighth  nerves ;  18,  Me- 
dulla oblongata,  the  number  being  placed 
on  the  olivary  body  ;  19,  Anterior  pyramid  ; 
20,  Roots  of  ninth,  tenth,  and  eleventh 
nerves  ;  21,  Twelfth  nerve. 


'  There  is  far  from  being  any  agreement  as  to  the  number  of  parts  which  ought  to 
compose  the  encephalic  isthmus,  some  authorities  making  more,  some  less.  The  limits 
of  this  small  apparatus  will,  nevertheless,  be  found  perfectly  circumscribed  if  it  be  ex- 
amined in  the  lower  animals,  and  particularly  iu  the  Horse.  An  antero-posterior  section 
of  the  encephalon  made  to  one  side  of  the  median  plane  appears  to  us  all  that  is  needed 
to  definitely  settle  the  point.  This  section,  seen  in  figure  829,  shows  in  the  plainest 
manner  that  the  encephalic  prolongation  of  the  spinal  axis  extends  to  the  corpora 
striata,  and  that  it  comprises  the  medulla  oblongata,  pons  Varolii,  cerebral  and  cerebellar 
peduncles  (or  crura),  the  corpora  quadrigemina,  and  the  thalami  optici.  All  these,  then, 
belong  to  one  and  the  same  system  — tlie  medullary  peduncle,  which  serves  as  a  bond 
of  union  between  the  three  principal  masses  of  the  encephalon,  and  which  we  have 
designated  the  isthmus.  It  may  be  added  that  this  manner  of  considering  the  encephalic 
istiimus  perfectly  agrees  with  the  teachings  of  physiology. 


TEE  ISTHMUS.  G77 

band,  and  particularly  in  pieces  that  have  been  hardened  by  alcohol  or 
acidulated  water,  is  seen  a  slight  oblong  prominence  which  corresi^onds  to 
what  in  Man  is  designated  the  olive  ^  {corpus  olivare) ;  it  is  isolated  from 
the  pyramid  by  a  longitudinal  groove,  whence  emerge,  in  front,  the  roots 
of  the  sixth  cranial  jjair,  behind,  those  of  the  twelfth ;  outwardly,  it  is 
limited  and  separated  from  the  restiform  body  by  the  origin  of  the  majority 
of  the  roots  belonging  to  the  glosso-pharyngeal  and  pneumogastric  nerves. 

Superior  face. — Covered  by  the  cerebellum,  it  is  channeled  in  its  middle 
by  an  excavation  (Fig.  323,  5),  which  constitutes  the  floor  of  the  fourth 
ventricle.  This  cavity  is  prolonged  forward  above  the  pons  Varolii,  between 
the  cerebellar  peduncles,  and  from  its  forming  behind  an  angle  resembling 
the  point  of  a  pen,  it  has  been  named  the  calamus  scriptorius. 

Two  thick  cords,  prolongations  of  the  superior  fasciculi  of  the  medulla 
spinalis,  border  the  calamus  scriptorius  on  each  side ;  these  are  designated 
the  corpora  restiformia.  Lying  together  at  their  posterior  extremities,  they 
separate  anteriorly,  so  as  to  represent  the  branches  of  a  V  (Fig.  323,  1). 

Lateral  faces. — Much  narrower  than  the  other  two,  and  showing  two 
thick  borders,  these  faces  give  the  profile  of  the  corpora  restiformia  (Fig. 
324,  2),  corpora  pyramidalia  (4),  and  the  fasciculus  between  these  two. 

2.  The  Pons  Varolii.     (Figs.  822,  14 ;  324,  5.) 

The  pons  Varolii,  also  named  the  tuher  annulare  or  mesoceplialon,  is  that 
part  of  the  brain  which  stands  out  prominently  across  the  isthmus,  between 
the  medulla  oblongata  and  the  crura  cerebri,  and  which  is  lodged  in  the 
anterior  depression  of  the  basilar  process. 

It  is  a  semicircular  band  of  white  transverse  fibres  thrown  aci'oss,  like  a 
bridge,  from  one  side  to  the  other  of  the  cerebellum.  In  every  sense  it  is 
convex,  wider  in  its  middle  than  in  its  lateral  portions,  and  crossed  from 
behind  to  before  by  a  shallow  median  groove  for  the  basilar  artery.  On  its 
free  surface,  whose  principal  features  we  have  just  described,  it  offers  for 
consideration  two  borders  and  two  extremities. 

The  posterior  harder,  slightly  convex,  is  separated  from  the  medulla 
oblongata  by  a  faint  groove. 

The  anterior  border,  also  convex,  but  indented  in  its  middle,  largely  over- 
hangs the  crura  cerebri,  which  are  limited  on  this  side  by  a  well-marked 
fissure. 

The  extremities  are  bent  upwards  to  enter  the  substance  of  the  cerebellum, 
in  the  form  of  two  thick  cords,  which  constitute  the  middle  crura  cerebelli 
(Fig.  324,  6).     They  exhibit  the  apparent  origin  of  the  trifacial  nerves. 

The  pons  Varolii  does  not  exist  in  birds. 

3.  The  PeduncuU  or  Crura  Cerebri.     (Figs.  322,  11 ;  324,  7.) 

These  are  two  very  large  white  fasciculi,  visible  at  the  inferior  surface 
and  sides  of  the  isthmus,  covered  sui^eriorly  by  the  corpora  quadrigemina 
and  thalami  optici,  and  continuous,  above  the  pons  Varolii,  with  the  fibres  of 
the  medulla  oblongata ;  while  theii*  anterior  extremities  enter  the  cerebral 
hemispheres. 

These  peduncles  (or  crui-a)  are  separated  from  each  other  by  a  middle 

'  This  prominence  corresponds  to  the  corpus  olivare  of  Man  only  in  its  position,  for 
it  has  not  its  structure. 
46 


678 


THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 


Fi^.  323. 


fissure — the  interpeduncular,  which  bifurcates  in  front  to  circumscribe  the 
mammillary  or  pisiform  tubercle  (corpus  albicans,  bulbi  fornicis)  (Fig.  327, 
18) :  a  small,  single,  and  rounded  elevation  of  a  white  colour,  like  the 
peduncles,  covered  by  the  pituitary  gland,  whose  root  is  represented  by  the 
tuber  cinereum,  and  is  situated  in  front  of  this  body. 

Behind,  the  crura  cerebri  are  limited  by  the  anterior  border  of  the  pons 
Varolii.  In  front,  they  are  circumscribed  by  the  optic  nerves,  which  pass 
obliquely  around  their  anterior  extremity  and  join  on  the  middle  line  before 
the  tuber  cinereum,  to  form  a  commissure  called  the  chiasma  of  the  optic 
nerves  (Fig.  322,  7).    On  the  sides,  their  tissue  is  confounded  with  that  of  the 

corpora  quadrigemina  and  thalami 
optici,  which  are  superposed  on  the 
cerebral  peduncles.  It  may  be 
remarked  that  the  part  of  their 
lateral  face  situated  below  the 
tubercula  testes,  forms  a  well- 
defined  triangular  space,  designated 
the  band  of  Reil,  lateral  triangular 
fasciculus,  and  lateral  oblique  fasci- 
culus of  the  isthmus. 

4.  The  Crura  Cerehelli. 

The  cerebellum  is  attached  to 
the  upper  face  of  the  isthmus  by 
two  short  and  thick  lateral  funiculi 
of  white  substance,  between  which 
is  comprised  the  posterior  ventricle ; 
these  constitute  the  cerebellar  crura. 

Three  distinct  fasciculi  enter 
into  the  composition  of  each  of 
these  cords  :  an  anterior,  a  posterior, 
and  a  middle. 

The  latter,  or  middle  cerebellar 
peduncle  (crus  cerebelli  ad pontem'), 
is  the  largest  of  the  three.  It  is 
formed  by  the  prolongation  of  the 
extremities  of  the  pons  Varolii 
(Figs.  323,  2  ;  324,  6). 

The  posterior  cerebellar  peduncle 
(crus  ad  medidlam  oblongatum),  the 
mqst  slender,  is  formed  by  the 
restiform  body,  one  portion  of  which 
is  reflected  below  the  posterior  root 
of  the  auditory  nerve  to  reach  the 
substance  of  the  cerebellum.  It 
is  closely  united  to  the  preceding, 
from  which  it  is  with  difficulty  dis- 
tinguished (Fig.  323,  3). 

The  anterior  cerebellar  peduncle 
(processus  e  cerebello  ad  testes)  is  a 
fasciculus  very  distinct  from  the 
to  the  middle  peduncle,  which  it 


SUPERIOU    VIEW    OF    THE    ENCEPHALIC    ISTHMUS 

1, 1,  Corpora  restiformica  ;  2,  Section  of  the  middle 
cerebellar  peduncles  ;  3,  Section  of  the  posterior 
cerebellar   peduncle ;    4,    Anterior    cerebellar 
peduncle ;  5,  Floor  of  the  posterior  ventricle 
6,  Valve  of  Vieussens  ;  7,  7,  Tubercula  testes 
8,  8,  Tubercula  nates;  9,  9,  Thalami  optici 
10,  Corpus  geniculatum  internum;  11,  Corpus 
geniculatum  externum  ;  12,  Corpus  striatum 
13,  Taenia  semicircularis ;    14,  Pineal  gland 
15,  Its  peduncle ;  16,  Common  anterior  open- 
ing;  17,  17,  Anterior  pillars  of  the  trigonal 
13,   Trifacial    nerve;    19,    Facial    nerve;    20, 
Auditory  nerve  ;  21,  Glosso-pharyngeal  nerve 
22,  Pneumogastric  nerve ;  23,  Spinal  nerve. 

other  two,  related  by  its  inner  border 


TBE  ISTHMUS.  679 

obliquely  crosses,  loses  itself  in  the  eerebelhxm  by  its  supero-posterior 
extremity,  arriving  bebind  the  testes,  and  passing  beneath  these  small  orfrans 
by  its  antero-inferior  extremity,  along  with  the  band  of  Eeil  or  supero-lateral 
fasciculus  of  the  cerebral  peduncles. 

In  studying  the  structure  of  the  cerebellum,  we  will  see  how  these 
peduncles  comport  themselves  in  its  interior. 

5.   Valve  of  Vieussens.    (Fig.  323,  6.) 

This  designation  is  given  to  a  very  thin,  white  lamella  which  unites,  on 
each  side,  the  two  anterior  cerebellar  peduncles.  In  shape  it  is  nearly  a 
parallelogram.  Its  superior  face  is  covered  by  the  cerebellum ;  the  inferior 
concurs  in  forming  the  floor  of  the  cerebellar  (fourth)  ventricle.  The  two 
lateral  borders  are  joined  to  the  peduncles  this  valve  unites ;  the  anterior  is 
attached  behind  the  testes;  while  the  pobterior  adheres  to  the  anterior 
vermiform  eminence  (linguetta  laminosa)  of  the  cerebellum. 

Gall  has  considered  this  lamella  as  a  commissure  of  the  anterior  cere- 
bellar peduncles,  and  we  thiuk  rightly ;  for  we  see  it  formed  almost 
exclusively  of  transverse  fibres  which  run  from  one  of  these  peduncles  to 
the  other.  These  fibres  are  most  apparent  in  front,  where  the  membrane  is 
much  thicker ;  behind,  they  are  mixed  with  some  longitudinal  fasciculi. 

6.  Corpora  Quadrigemina  or  Bigemina.     (Fig.  323,  7,  8.) 

These  are  four  round  eminences,  placed  in  pairs,  which  surmount  the 
cerebral  peduncles  behind.  The  two  posterior,  the  smallest,  are  also  named 
the  tiihercula  testes,  and  the  anterior  pair  the  tubercula  nates. 

The  posterior  corpora  quadrigemina,  or  tubercula  testes,  are  related,  in  front, 
with  the  anterior  eminences  :  behind,  with  the  anterior  cerebellar  peduncles 
and  the  valve  of  Vieussens,  from  which  they  are  separated  by  a  transverse 
groove,  from  the  bottom  of  which  arise  the  pathetici  nerves.  An  oblique 
band  unites  them,  outwardly,  to  that  portion  of  the  optic  layer  designated 
the  corpus  geniculatum  internum. 

The  anterior  corpora  quadrigemina,  or  tubercula  nates,  are  distinguished 
from  the  preceding  not  only  by  their  larger  volume,  but  by  their  colour, 
which  is  grey,  that  of  the  testes  being  white.  They  are  also  rounder,  nearer 
each  other,  and  covered  by  the  cerebral  hemispheres ;  while  the  posterior 
rather  lie  beneath  the  cerebellum.  A  curved  groove  isolates  them,  in  front, 
from  the  thalami  optici. 

7.  TJialami  Optici.     (Fig.  323,  9.) 

This  name  is  given  to  that  part  of  the  upper  face  of  the  isthmus  which 
is  situated  in  front  of  the  corpora  quadrigemina.  These  thalami  are 
therefore  placed  above  the  anterior  part  of  the  cerebral  pedimcles. 

Larger  altogether  than  the  corpora  quadrigemina,  and  more  so  before 
than  behind,  each  exbibits  a  grey,  slightly  convex,  and  very  irregularly 
quadrilateral  surface,  covered  by  the  velum  interpositum,  which  separates  it 
from  the  cornu  Ammonis  (pes  Mppocarapi),  and  from  the  posterior  pillars  of 
the  cerebral  trigonal  (fornix). 

Inicardly,  they  incline  towards  each  other  in  forming  on  the  median 
line  a  somewhat  deep  fissure,  in  which  runs,  from  before  to  behind,  two 
white  longitudinal  bands  that  will  be  noticed  hereafter  as  the  anterior 
peduncles  of  the  pineal  gland.     This  fissure  enters,  behind,  into  the  common 


680 


THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 


posterior  opening  (foramen  commune  posterius) ;  in  front,  into  the  common 
anterior  opening  (foramen  commune  anterius)  :  orifices  wliicli  will  be  described 
with  the  interior  of  the  isthmus. 

Outwardly,  the  thalamus  optici  shows  two  prominences  called  the  corpora 
genicuiata,  from  which  arise  the  second  pair  of  nerves  ;  placed  one  before 
the  other,  the  posterior  nearer  the  middle  line  than  the  anterior,  these  two 
projections  are  distinguished  as  external  and  internal.  The  corpus  genicu- 
latum  externum  is  always  more  voluminous,  better  defined,  and  situated  on  a 

Fio;.  324. 


LATERAL   VIEW   OF   THE   ISTHMUS. 

1,  Medulla  oblongata;  2,  Corpus  restiforme ;  3,  Lateral  fasciculi  of  the  medulla 
oblongata;  4,  Inferior  fasciculus,  or  corpus  pyramidale ;  5,  Pons  Varolii;  6, 
Middle  peduncle  of  the  cerebellum ;  7,  Cerebral  peduncle  ;  8,  Testis  ;  9,  Natis ; 
10,  Corpus  geniculatum  internum  ;  11,  Corpus  geniculatum  externum  ;  12,  Optic 
nerve  ;  13,  Fourth  nerve  resting  on  the  band  of  Reil ;  14,  Sensitive  root  of  the 
trigeminal  nerve ;  15,  Its  motor  root ;  16,  Facial  nerve ;   17,  Auditory  nerve. 

more  elevated  plane  than  the  internal  corpus  geniculatum,  which  is  united  to 
the  posterior  corpora  quadrigemina  by  an  oblique  band  (Figs.  323,  10  ; 
324,  11). 

Behind,  the  thalami  oiDtici  appear  to  be  notched  to  receive  the  nates, 
which  they  slightly  inclose.  * 

In  front,  they  are  separated  from  the  corpus  striatum  by  a  groove,  at  the 
bottom  of  which  is  a  narrow  strip  named  the  semicircular  band  (taenia  semi- 
circularis). 

Pineal  Gland  or  Conarium.    (Fig.  323,14.) 

This  name  has  been  given  to  a  small  tubercle  of  a  reddish-brown  colour, 
in  the  form  of  a  pine-cone,  enveloped  by  a  duplicature  of  pia  mater  from 
the  velum  interpositum,  with  its  apex  upwards,  and  its  base  resting  on  the 
common  posterior  opening,  which  it  closes,  and  around  which  it  is  attached 
by  a  circular  lamella. 

From  this  lamella  is  detached,  in  front,  two  fibrous  cords — the  anterior 


THE  ISTHMUS.  6S1 

■peduncles  of  the  conariiim  (or  habenee).  These  (Fig.  323,  15)  are  two 
narrow  white  bauds,  which  commeuce  at  the  base  of  the  pineal  gland,  and 
are  directed  forward  parallel  to  each  other,  in  the  bottom  of  the  fissure  of 
the  thalami  optici,  to  which  they  firmly  adhere.  On  arriving  at  the  anterior 
common  opening,  they  become  attached  to  the  anterior  pillars  of  the  cerebral 
trigonal  (or  crura  of  the  fornix).  Sometimes  they  are  very  narrow  and 
sei)arated  by  an  interval ;  but  more  freqiiently  they  are  relatively  wide, 
and  immediately  in  contact  on  the  median  line. 

The  conarium  is  far  from  always  oftering  the  same  volume  ;  it  has 
been  exhibited  in  its  usual  dimensions  in  Figure  323,  and  in  Figure  327 
it  is  shown  as  incomparably  larger. 

The  structure  of  the  pineal  gland  appears  to  be  very  simple,  and  only 
comprises  one  substance  of  a  brownish-grey  colour,  apparently  amorphous, 
and  sometimes  studded  with  calcareous  granulations  (acervulus),  but  with- 
out any  internal  cavities. 

This  organ  and  that  whose  description  follows,  do  not  belong,  proi)erly 
speaking,  to  the  system  of  the  encephalic  isthmus ;  but  are  rather,  as  we 
have  already  said,  appended  glands,  which  merit  to  be  described  apart,  the 
same  as  the  three  immense  cerebellar  and  cerebral  ganglia.  If  we  have 
studied  them  in  this  place,  it  was  only  for  the  sake  of  simplification. 


9.  Pituitary  Gland.     (Figs.  322,  8 ;  327,  19.) 

The  pituitary  gland,  also  named  the  liypopliysis  cerebri  and  suprasplie- 
noidal  appendage,  is  a  small  disc-shaj)ed  tubercle,  fixed  to  the  anterior 
extremity  of  the  interpeduncular  fissure  by  the  pituitary  stem  (infundihulum) 
and  the  tuher  cinereum. 

a.  The  tuber  cinereum  is  a  little  eminence  of  a  grey  colour,  situated  in 
the  middle  line,  between  the  corpus  albicans  and  the  chiasma  of  the 
optic  nerves,  at  the  anterior  limit  of  the  encephalic  isthmus.  This  emi- 
nence is  hollow,  and  its  cavity  is  nothing  more  than  a  diverticulum  of  the 
middle  ventricle. 

h.  The  infundibulum  is  only  a  short  conical  prolongation,  whose  base  is 
attached  to  the  tuber  cinereum,  and  its  apex  to  the  superior  face  of  the 
pituitary  gland.  The  cavity  of  the  tuber  cinereum  is  continued  into  the 
infundibulum,  and  terminates  in  a  cul-de-sac  towards  its  summit.  This 
prolongation,  also  formed  of  grey  substance,  is  distinguished  by  its  great 
fragility ;  so  that  it  requires  some  care  to  preserve  it  intact  when  opening 
the  cranium  at  its  base. 

c.  The  pituitary  gland  is  lodged  in  the  sella  turcica,  where  it  is  en- 
veloped by  the  suprasphenoidal  duplicatui-e  of  dura  mater ;  it  is  a  small, 
nearly  circular  body,  flattened  above  and  below,  and  more  or  less  thick, 
according  to  the  subjects. 

Its  inferior  face  rests  on  the  sphenoid  bone  through  the  medium  of  the 
dura  mater,  to  which  it  is  strongly  adherent ;  the  superior  covers  the  corj^us 
albicans,  with  a  portion  of  the  cerebral  peduncles,  and  in  front  receives 
the  insertion  of  the  pituitary  stem.  Its  circumference  responds  to  the  supra- 
sphenoidal duj^licature,  whose  interior  forms  the  cavernous  sinus. 

There  is  no  cavity  in  the  pituitary  gland.  The  matter  composing  it 
appears  to  be  almost  amorphous ;  it  is  yellow  in  the  anterior  half  of  the 
organ,  and  brown  in  its  posterior  portion. 


682 


THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 


INTERNAL    CONFORMATION    OF    THE    ISTHMUS.      (Fig.  327.) 

The  encephalic  isthmus  is  hollowed  at  the  thalami  optici  by  a  central 
cavity,  named  the  middle  (or  third)  ventricle,  which  is  extended  backwards 
beneath  the  corjjora  quadrigemina  by  a  canal — the  aqueduct  of  Sylvius ; 
this  opens,  below  the  valve  of  Vienssens,  into  the  posterior  (or  fourth)  ven- 
tricle— another  cavity  comprised  between  the  cerebellum  and  medulla 
oblongata.     These  three  diverticuli  will  be  studied  in  succession. 


1.  Middle  Ventricle,  or  Ventricle  of  the  Thalami  OpHci.     (Fig.  327,  13.) 

The  middle  ventricle  is  an  irregular  cavity,  elongated  from  behind  to 
before,  depressed  on  each  side,  and  oifering  for  study  two  loalls,  a  floor,  a 
roof,  and  two  extremities. 

The  two  icalls  are  smooth,  nearly  plane,  or  very  slightly  concave  from 
•above  to  below. 

The  floor  is  extremely  narrow,  and  only  forms  a  channel  whose  bottom 
corresponds  to  the  interpeduncular  fissure,  which  is  nearer  in  front  than 
behind,  and  to  the  corpus  albicans  and  tuber  cinereum.  The  cavity  of 
the  latter  (Fig.  327,  20),  prolonged  into  the  pituitary  stem,  communicates 
with  the  middle  ventricle,  and  assists  in  its  formation. 

The  roof,  as  narrow  as  the  floor,  and,  like  it,  nothing  but  a  channel,  is 
constituted  by  the  two  thalami  optici  which  are  joined  to  one  another  above 

the  ventricle,  forming  a  thick 
'^'    "  grey    commissure   (Fig.    327, 

16).  It  is  terminated  at  its 
extremities  by  the  two  orifices 
already  noted  as  the  posterior 
and  anterior  common  foramina. 
The  posterior  common  foramen 
(Fig.  327,  15)  commences  be- 
hind the  grey  commissure,  and 
terminates  at  the  base  of  the 
pineal  gland  by  an  irregu- 
larly expanded  cul-de-sac.  It 
is  limited  behind  by  the  pos- 
terior ivhite  commissure,  a  thin 
fasciculus  of  transverse  fibres 
placed  in  advance  of  the  cor- 
pora quadrigemina,  above  the 
entrance  to  the  aqueduct  of 
Sylvius,  (or  iter  a  tertio  ad 
quartum  ventriculum),  and  whose 
extremities  are  lost  in  the  sub- 
stance of  the  thalami  optici 
(Fig.  325,  9).  The  cmterior 
common  foi-amen,  also  desig- 
nated the  foramen  of  Monro 
(and  iter  ad  infundibulum) 
(Fig.  327,  14),  is  the  medium 
of  communication  between  the  middle  and  lateral  ventricles,  and  aifords 
a  passage  to  the  vascular  cord  which  unites  the  two  choroid  plexuses.     It  is 


TRANSVERSE   SECTION   OF   THE   ENCEPHALON    AT 
THE    POSTERIOR    COMMON    FORAMEN. 

1,  White  substance  of  the  hemisphere,  or  centrum 
ovale  of  Vieussens;  2,  2,  Grey  substance  forming 
the  external  layer  of  the  convolutions;  3,  Section 
of  the  corpus  callosum ;  4,  4,  Interior  of  the 
latei-al  ventricles  ;  5,  Section  of  the  great  vena 
Galeni ;  6,  6,  Cerebral  peduncles  ;  7,  7,  Section  of 
the  isthmus ;  8,  Posterior  common  foramen  ;  9, 
Posterior  white  commissure  ;  10,  Entrance  to  the 
aqupduct  of  Sylvius. 


THE  ISTHMUS.  683 

pierced  in  front  of  the  gi'ey  commissure,  beneatli  tho  summit  of  the  fornix, 
whose  two  pillars  concur  to  circumscribe  it,  and  between  which  is  seen  the 
anterior  ichite  eomniissure.  This  is  a  small  band  of  white  transverse  fibres, 
analogous  to  that  which  constitutes  the  posterior  commissure,  but  stronger, 
and  passing  in  front  of  the  anterior  pillars  of  the  fornix,  its  extremities 
entering  and  becoming  lost  in  the  corpus  striatum  on  each  side. 

The  posterior  extremity  of  the  middle  ventricle,  narrower  than  the 
anterior,  and  placed  on  a  more  elevated  plane,  is  continuous  with  the 
aqueduct  of  Sylvius,  wdiose  entrance  (Fig.  325,  10_)  is  beneath  the  pos- 
terior commissure,  towards  the  common  foramen. 

The  anterior  extremity,  more  dilated  than  the  posterior,  is  situated 
immediately  above  the  optic  chiasma,  and  is  only  separated  from  the  bottom 
of  the  great  interlobular  fissure  of  the  brain  by  a  small  and  very  thin  grey 
lamina  attached  to  that  chiasma,  and  for  this  reason  named  by  writers  the 
grey  root  of  the  optic  nerves.  This  lamina  (lamina  cinerea)  is  readily  seen 
when  the  optic  commissure  is  turned  down  on  the  pituitary  gland ;  it  is 
sufiicient  to  traverse  this  to  enter  the  middle  ventricle. 

The  ependymis,  which  lines  the  central  canal  of  the  medulla  spinalis, 
also  covers  the  walls  of  this  cavity  ;  through  the  aqueduct  of  Sylvius,  it  is 
prolonged  into  the  posterior  (or  fourth)  ventricle  ;  by  the  anterior  common 
foramen  into  the  lateral  ventricles,  and  thence  into  the  spaces  in  the  middle 
of  the  olfactory  lobes. 

2.  Aqueduct  of  Sylvius.    (Fig.  327,  6.) 

This  is  a  longitudinal  median  canal  passing  beneath  the  corpora  quad- 
rigemina,  and  above  the  peduncles  of  the  brain. 

Its  anterior  extremity  communicates  with  the  middle  ventricle,  and  the 
posterior  opens  below  the  valve  of  Vieussens  into  the'  cerebellar  (or  foui-th) 
ventricle. 

3.   The  Posterior  or  Cerebellar  Ventricle.    (Fig.  327,  5.) 

This  ventricle^  (or  sinus  rhomhoidalis),  situated  beneath  the  cerebellum, 
between  its  peduncles,  and  above  the  medulla  oblongata  and  pons  Varolii, 
is  a  cavity  elongated  from  before  to  behind,  and  almost  entirely  occupied 
by  the  vermiform  processes. 

Its  superior  icall  is  formed  by  these  two  processes,  the  valve  of  Vieussens, 
and  that  of  Renault.  The  inferior,  or  floor  of  the  cavity,  is  represented  by 
the  excavation  on  the  superior  face  of  the  medulla  oblongata,  and  which  is 
prolonged  in  front,  above  the  pons  Varolii,  to  near  the  testes. 

The  anterior  extremity  communicates  with  the  aqueduct  of  Sylvius. 
The  posterior  occupies  the  summit  of  the  calamus  scriptorius. 

STRUCTURE    OF    THE    ISTHMUS. 

The  encephalic  isthmus  being  only  a  prolongation  of  the  spinal  cord, 
ought  to  resemble  it  in  its  structure ;  and  this  is,  in  fact,  what  is  observed, 
particularly  in  its  posterior  part,  the  common  features  of  their  organisation 
disappearing  as  we  approach  its  anterior  extremity. 

After  what  has  been  said  as  to  the  external  conformation  of  the  medulla 
oblongata,  we  know  that  this  organ  presents,  on  each  of  its  lateral  halves, 
traces  of  a  division  into  three  principal  fasciculi  :    a  superior,  formed  by 

'  As  the  cerebellum  concurs  in  the  formation  of  this  cavity  it  would  perhaps  be 
better  to  defer  its  study  until  that  organ  has  been  described. 


684 


THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 


Fig:.  326. 


the  corpus  restiforme ;  an  inferior,  represented  by  tlie  corpus  pyramidale ; 
and  tlie  third,  or  intermediate  of  the  other  two.  These  three  fasciculi  are 
only  the  continuation  of  those  we  have  recognised  in  the  cord  itself,  and 
whose  properties  they  share — the  first  being  sensitive,  and  the  others  motor. 

The  superior  fasciculus,  or 
corpus  restiforme,  lying,  at  its 
posterior  extremity,  beside  its 
fellow  of  the  oj)posite  side,  is 
separated  from  it  for  the  greater 
part  of  its  extent  by  the  excava- 
tion that  constitutes  the  floor  of 
the  fourth  ventricle.  It  rests  on 
the  external  part  of  the  lateral 
fasciculus.  At  the  extremity  of 
the  pons  Varolii  is  given  oflf  a 
small  branch  that  forms  the  pos- 
terior cerebellar  jDcduncle ;  it 
then  continues  its  com'se  on  the 
side  of  the  posterior  ventricle, 
soon  joins  the  anterior  cerebellar 
peduncle,  which  is  above  it,  and 
DISSECTION  OF  THE  MEDULLA  OBLONGATA,  SHOWING  with  it  passcs  Dencath  the  cor- 
THE  CONNECTION  OP  ITS  SEVERAL  FASCICULI,  OR  pora  quadrigomiua. 
STRANDS.  The  inferior  fasciculus,  the 

A,  Corpus  striatum ;  B,  Thalamus  opticus ;  C,  D,  Cor-  thinnest  of  the  three,  comprises, 
pora  quadrigemina;  E,  Commissure  connecting  as  has  been  said,  all  that  portion 
them  with  the   cerebellum:    F,  Corpora  restilor-       .    ,,        in         ,  .  i  ,-j    . 

mia ;  p,  p,  Pons  Varolii ;  st,  st,  Sensory  tract ;  of  the  bulb  which  constitutes 
mt,  mt,  Motor  tract ;  g,  Olivary  tract ;  p,  Pyrami-  the  pyramid.  But  when  this 
dal  tract ;  og.  Olivary  ganglion  ;  op,  Optic  nerve  ;  eminence  is  null,  or  but  slightly 
3?«,  Root  of  third  pair  (motor) ;  5s,  Sensory  root  „iarked,  we  ought  to  recognise 
of  the  htth  pair.  ^^^  ^.^^.^^  ^j^.^j^  separate  it  from 

the  lateral  fasciculus  by  the  line  of  insertion  of  the  roots  of  the  great 
hypoglossal  nerve,  supposed  to  be  prolonged  to  the  pons  Varolii,  near  the 
point  of  emergence  of  the  external  motores  oculorum  nerve.  Its  fibres 
partly  intercross  with  those  of  the  opposite  fasciculus,  in  the  bottom  of 
the  middle  fissure.  They  all  pass  above  or  across  the  transverse  fasciculi 
of  the  pons,  to  constitute  the  inferior  plane  of  fibres  of  the  cerebral 
peduncles. 

The  lateral  or  intermediate  fasciculus  of  the  bulb,  comprised  between  the 
line  of  insertion  of  the  hypoglossal  nerve-roots,  and  those  of  the  motor  roots 
proper  to  the  glosso-pharyngeal,  pneumogastric,  and  spinal  nerves,  difibrs 
but  little  from  the  inferior  cord.  By  a  portion  of  its  upper  face  it  forms 
the  floor  of  the  fourth  ventricle.  After  leaving  the  pons  Varolii,  like  the 
pyramidal  fasciculus,  it  goes  to  assist  in  the  formation  of  the  cerebral 
peduncles,  and  particularly  of  their  triangular  oblique  fasciculus. 

In  examining,  collectively,  at  these  peduncles,  the  medullary  fasciculi 
prolonged  into  the  isthmus,  we  observe  nearly  the  same  order  of  superposition 
as  in  the  bulb ;  but  it  is  no  longer  possible  to  distinguish  them  clearly  from 
each  other,  they  being  confounded  with  those  of  the  opposite  side.  Their 
fibres  can  be  seen  prolonged  in  a  mass  beneath  the  corpora  quadrigemina, 
across  the  proper  substance  of  the  thalami  optici,  and  passing  into  the 
corpora  striata,  to  disappear  on  each  side,  like  a  fine  expanding  sheath,  in  the 
middle  of  the  cerebral  hemispheres. 


TEE  ISTSmjS.  G85 

To  tills  important  system  of  icliite  longitudinal  Jjhres — a  prolongation  of 
those  of  the  sjnnal  cord — is  found  annexed  as  complementary  elements  in  the 
organisation  of  the  encephalic  isthmus,  several  systems  of  transverse  fibres — 
also  white — and  masses  of  grey  substance.  The  following  is  a  summary 
exiiosition  of  the  arrangement  of  these  new  elements.  In  proceeding  from 
behind  to  before,  we  notice,  among  the  ichite  transverse  fibres : 

1.  The  expansion  of  arciform  fibres  which  sometimes  covers  the  inferior 
face  of  the  bulb  (Fig.  338,  j) :  their  superior  extremity  is  lost  in  the 
corpus  restiforme ;  the  inferior  is  buried  in  the  intermediate  fissure  of  the 
pyramid  and  the  lateral  fasciculus. 

2.  The  proper  fibres  of  the  pons  Varolii :  they  constitute  a  very  thick 
semicii'cular  fasciculus  whose  extremities  form  the  middle  cerebellar 
peduncles  and  enter  the  cerebellum ;  this  fasciculus  enveloj^s,  inferiorly 
and  laterally,  the  longitudinal  fibres  of  the  isthmus ;  it  is  crossed  by  several 
superposed  planes  of  transverse  fibres. 

3.  The  transverse  fibres  of  the  valve  of  Yieussens  and  those  of  the  white 
commissures,  which  have  been  already  noticed. 

The  grey  substance  of  the  isthmiis,  which  now  remains  to  be  mentioned,  is 
far  from  being  so  abundant  as  the  white  substance,  and,  as  in  the  spinal 
cord,  it  is  principally  deeply  buried  in  the  texture  of  the  organ.  In  the 
medulla  oblongata  none  is  found  on  the  track  of  the  superior  and  inferior 
fasciculi  of  fibres ;  but  the  lateral  fasciculi  are  intermingled  with  it, 
and  there  is  a  layer  on  the  floor  of  the  foui-th  ventricle.  It  is  also  found 
in  the  cerebral  peduncles,  and  particularly  in  the  prolongation  of  the  lateral 
fasciculi  of  the  bulb. 

Each  of  the  corpora  quadrigemina  is  composed  of  a  small  mass  of  this 
grey  substance,  and  is  covered  by  a  thin  pellicle  of  white  matter  which  is 
scarcely  perceptible  in  the  anterior  eminences.  The  optic  thalamus  is  a 
similar  mass,  though  more  voluminous,  darker  coloured,  and  without  a  layer 
of  white  substance  on  its  superficial  face. 

Lastly,  nerve  cells  also  exist  between  the  various  layers  of  transverse 
fibres  of  the  pons  Varolii,  and  between  the  tubes  which  constitute  the  valve 
of  Vieussens. 

DIFFERENTIAL  CHAEACTEBS  IN  THE  ISTHMUS  OF  OTHER  THAN  SOLIPED  ANIMALS. 

Apart  from  its  volume,  the  isthmus  does  not  present  any  sensible  differences  in 
Euminants  and  the  Pig.  In  the  Ox.  it  is  remarked  that :  1,  The  inferior  j^yramids  of  the 
medulla  oblongata  are  more  prominent,  and  the  transverse  cords  parallel  to  the  pons 
Varolii  more  voluminous  than  in  Solipeds ;  2,  The  crura  cerebri  are  short ;  3,  The  optic 
nerves  are  larger  than  in  Solipeds ;  4,  There  is  a  largely  developed  pituitary  gland, 
excavated  by  a  wide  cavity,  and  flattened  from  above  to  below ;  5,  Lastly,  the  testes  are 
more  conical  and  less  distinct  from  the  nates  than  in  the  animals  already  studied. 

In  the  Carnivora,  the  fourth  ventricle  is  very  large  and  deep,  and  bordered  by 
salient  and  detached  corpora  restiformia.  Its  floor  is  marked  by  some  white  transverse 
strife.  The  pons  Varolii  is  large  ;  the  cords  ^or  columns')  of  the  medulla  oblongata,  parallel 
to  its  posterior  border,  are  as  developed  as  in  the  Horse,  without  taking  into  consideration 
the  difference  in  size  of  the  two  species.  The  pyramids  are  volumiuous,  and  the  olivary 
bodies  well  defined.    The  testes  are  larger  than  the  nates. 

COMPARISON   OP  THE   ISTHMTS   OF   MAN   WITH   THAT   OP   AXDIALS. 

In  human  anatomy,  the  medulla  oblongata  and  encephalic  isthmus  are  described 
separately. 

The  first  shows  on  its  lower  face  a  well-marked  groove,  a  continuation  of  that  of  the 
spinal  medulla;  it  terminates  anteriorly  in  a  deep  fossa  named  the  foramen  cxcum  of 
Vicq-d'Azyr.     The  pyramids  are  well  marked.    The  olivary  bodies  are  much  more 


686  THE  CENTBAL  AXIS  OF  THE  NEBVOUS  SYSTEM. 

prominent  than  in  animals,  and  are  also  distinguished  by  the  presence  of  a  grey 
nucleus  in  their  interior.  'I'he  medulla  oblongata  of  Man  has  not  the  transverse  band, 
behind  the  pons  Varolii,  whicli  we  described  in  the  Horse  (Fig.  333). 

With  regard  to  the  isthmus  proper,  it  contains  the  parts  in  front  of  the  medulla 
oblongatii  already  studied  in  the  domesticated  animals.  The  pons  Varolii  is  very  large  ; 
the  crura  cerebri  are  separated  from  each  other  by  a  groove,  at  the  bottom  of  which  are 
several  small  openings.  The  fourth  ventricle  is  deep,  is  bordered  by  well-developed 
corpora  restiformia,  and  inclosed  posteriorly  and  laterally  by  the  valves  of  Turin  (velum 
meduUare  posterius).  On  its  floor  are  remarked  transverse  striae  (linex.  transversa)  named 
the  barbs  of  the  calamus  scriptorius,  which  are  also  found  in  the  Dog.  The  testes  are 
smaller  than  the  nates ;  but  the  diiference  in  their  volume  is  less  considerable  than  exists 
between  Solipeds  and  Euminants.     Their  structure  is  already  known. 

Article  III. — The  Cerebellum. 

The  cerebellum,  or  posterior  enlargement  of  the  encephalon,  is  the 
single  mass  supported  by  the  isthmus,  separated  from  the  cerebrum  by  the 
transverse  partition  constituting  the  tentorium  cerebelli,  and  lodged  in  the 
posterior  compartment  of  the  cranial  cavity,  which  almost  exactly  gives  the 
measure  of  its  volume. 

1.  External  Conformation  of  the  Cerebellum. 

The  cerebellum,  isolated  by  dividing  its  lateral  peduncles  from  the 
medullary  prolongation  on  which  it  is  fixed,  presents  the  form  of  an  almost 
globular  mass,  slightly  elliptical,  elongated  transversely :  while  its  external 
surface  is  furrowed  by  a  great  number  of  sulci,  the  two  principal  of  which 
(sulci  horizonfalis)  pass  in  a  circular  manner  on  each  side  of  the  middle  line 
around  the  organ,  dividing  it  into  three  lobes — a  middle  and  two  lateral. 

The  three  lobes  of  the  cerebellum  are  not  always  readily  distinguished 
from  each  other,  in  consequence  of  the  shallowness  and  irregularity  of  the 
two  sulci  separating  them.  We  will,  nevertheless,  study  them  in 
succession,  and  afterwards  examine,  in  a  general  manner,  the  furrows  on  their 
superficies. 

Middle  lobe  (Fig.  321,  2). — This  has  been  compared  to  a  silk-worm 
rolled  in  a  circular  manner  around  the  middle  portion  of  the  cerebellum, 
and  whose  two  extremities  are  joined,  without  being  confounded,  below  the 
inferior  face  of  the  organ. 

This  vermicular  disposition  is  not  well  defined  in  the  middle  and 
superior  portion  of  the  cerebellum,  where  this  lobe  is  always  more  or  less 
subdivided  into  large  multiple  and  irregular  lobules ;  but  it  is  better 
observed  before  and  behind,  in  those  points  which  correspond  to  the  two 
extremities  of  the  animal  selected  as  a  term  of  comparison.  There  may 
be  remarked  two  longitudinal  eminences  transversely  annulated  on  their 
surface,  and  curved  beneath  the  cerebellum  in  such  a  way  as  to  come  in 
contact  with  each  other.  These  eminences  constitute  the  anterior  and 
posterior  vermiform  processes.  Their  extremities  are  lodged  in  the  fourth 
ventricle,  whose  roof  they  concur  in  forming. 

On  the  anterior  vermiform  process  the  posterior  border  of  the  valve  of 
Vieussens  is  inserted. 

The  posterior  vermicular  process  also  receives  the  insertion  of  a  valve 
already  mentioned,  and  which  must  be  again  briefly  referred  to.  This  valve, 
described  for  the  first  time  by  M.  Eenault,'  forms  a  lamina  of  a  certain 
thickness  stretched  above  the  calamus  scriptorius.  It  has  exactly  the 
triangular  form  of  this  space,  and  presents  a  superior  face  covered  by  the 

Q  The  late  eminent  veterinary  teacher  and  director  of  the  Alfort  School.) 


THE  CEREBELLUM. 


687 


posterior  vermiform  process  ;  an  inferior  face,  stucldeJ  in  some  points  with 
small  vascular  loops  ;  a  base  tixccl  to  the  vermis,  near  the  free  extremity  of  that 
prominence,  and  to  its  lateral  parts  ;  two  lateral  borders,  attached  to  the 
corpora  restiformia  on  each  side  of  the  calamus  scriptorius ;  and  a  summit 
corresponding  to  the  receding  angle  of  the  excavation.  This  lamina  is, 
doubtless,  nothing  more  than  a  septum  formed  by  the  external  pia  mater, 
and  on  which  is  extended  the  internal  membrane  that  covers  the  walls  of 
the  cerebellar  ventricle.  Otherwise,  it  is  in  direct  continuity,  tou  ards  its  base, 
with  an  evident  dependency  of  the  pia  mater — the  plexus  choroides} 


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laferaZ  lohes  (Fig.  321,  3,  3).— These  are  shaped  like  two  irregular 
segments  of  a  sphere.    Their  surface,  fissured  and  lobulated  in  every  direction, 
presents  nothing  interesting  externally,  superiorly,  or  posteriorly.     It  is  by 
'  This  septum  is  represented  in  the  rudimentary  state  in  Man,  by  the  vaiulx  Tarini. 


688  TEE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEBI. 

their  inferior  part  that  tlie  peduncles  enter  the  substance  of  the  cerebellum  ; 
and  behind  this  point,  beneath  their  lateral  parts,  the  cerebellar  plexus  choroides 
is  applied. 

The  cerebellar  choroid  plexuses. — This  name  is  given  to  two  small  reddish 
granular  masses,  formed  of  vascular  loops,  elongated  from  before  to  behind, 
depressed  above  and  below,  and  comprised  at  their  internal  borders  between 
the  corpora  restiformia  and  the  inferior  face  of  the  lateral  lobes  of  the 
cerebellum,  to  which  they  are  strongly  adherent  by  their  superior  face. 
These  two  plexuses  are  joined  together  by  means  of  Eenault's  valve,  which 
is  united  to  them  towards  its  base. 

Sulci  and  lobules  of  the  cerebellum. — On  examining,  in  a  general 
manner,  all  the  sulci  which  intersect  the  external  surface  of  the  cerebellum, 
we  see  that  they  penetrate  to  very  uneo[ual  depths  in  the  substance  of  the 
organ,  and  that  they  divide  it  into  successively  decreasing  segments,  of 
which  Figs.  324  and  327  may  furnish  a  sufiicient  idea. 

There  is  at  first  a  certain  number  of  princij^al  lobules,  which  are  divided 
into  secondary  lobules  ;  and  these,  again,  are  in  their  turn  separated  into  short 
lamellae,  representing  the  extreme  limits  of  cerebellar  lobulation. 

2.  Internal  Conformation  and  Structure  of  the  Cerebellum. 

The  cerebellum  concurs,  by  its  inferior  plane  and  the  internal  face  of 
its  peduncles,  to  form  the  cavity  already  described  as  the  posterior  or  cere- 
bellar ventricle ;  but  in  the  mass  of  the  organ  itself  there  is  no  trace  of 
excavation  or  other  peculiarity.  This  is  demonstrated  in  the  most  evident 
manner  by  sections  of  its  substance  made  either  in  an  antero-posterior 
or  in  a  transverse  direction.  We  only  see  in  these  traces  of  the  sulci  which 
divide  the  organ  into  lobules ;  and  they  also  afford  evidence  as  to  the 
structure  of  the  cerebellum,  showing  that,  like  all  the  other  parts  of  the 
cerebro-spinal  axis,  it  is  formed  of  white  and  grey  substance. 

The  latter,  spread  over  the  entire  surface  of  the  organ,  constitutes  the 
cortical  layer  of  the  different  segments  of  which  it  is  composed.  It  is  even 
jirolonged  into  the  convolutions  which  increase  the  surface-extent  of  the 
cerebellum ;  in  each  lobule  it  may  be  decomj)osed  into  superposed  layers, 
parallel  to  the  lamina  of  white  substance  that  forms  the  nucleus  of  the 
lobule ;  between  these  layers  of  grey  substance  is  a  very  thin  mass  of  white 
matter. 

The  lohite  substance,  enveloped  on  every  side  by  the  grey,  forms  two 
thick  nuclei  occupying  the  centre  of  the  lateral  lobes,  and  which  are  united 
and  confounded  on  the  median  line  in  the  texture  of  the  middle  lobe. 

These  two  nuclei,  in  continuity  on  each  side  with  the  cerebellar 
peduncles,  are  only  their  prolongations  or  inter  cerebellar  portions.  They 
send  into  the  middle  of  each  principal  lobule  a  long  and  thick  branch,  which 
gives  off  smaller  divisions  that  ramify  in  the  secondary  lobules,  and  from 
which  escape  a  new  series  of  ramuscules  that  enter  the  smallest  segments ; 
this  gives  to  the  cerebellum  a  beautiful  arboreal  aspect,  justly  designated 
by  the  older  anatomists  the  arbor  vitce.  (See  Figs.  324,  327,  329,  for 
representations  of  the  arbor  vitce  cerebelli.) 

In  the  interior  of  these  nuclei,  a  little  in  front,  there  sometimes  exists  a 
small,  slightly-grey  spot ;  this  is  the  trace  of  the  corpus  rhomboideum  (or 
dentatum  of  Man). 

The  nuclei  of  the  white  substance  of  the  cerebellum  are  constituted,  like 
the  matter  of  the  medulla,  by  nerve-tubes  which  are  continuous  on  one  side 


TEE  CEBEBBUM. 


689 


with  the  crura  cerebelli,  and  on  the  other  terminate  in  the  cells  of  the  grey- 
substance. 

In  the  grey  spot  that  forms  the  corpus  rhomboideum,  is  a  great  number  of 
large  nerve-cells. 

With  regard  to  structure,  the  grey  matter  of  the  cere-  pjo-  303 

bellimi  may  be  decomposed  into  two  layers ;  the  super- 
ficial is  very  rich  in  blood-vessels,  has  a  greyish  tint,  and 
is  composed  of  large  nerve-cells  and  smaller  rounded  ele- 
ments ;  the  deep  layer  is  of  a  yellow  colour,  and  also 
contains  nerve-cells  and  round  elements,  though  the  latter 
are  smaller  than  in  the  other  layer,  and  have  been  sometimes 
mistaken  for  simple  nuclei. 

DTFFEEEXTIAL   CHARACTERS   OF  THE   CEREBELLTJ3I   IN   OTHER   THAN 
SOLIPED    AXIJIALS. 

The  external  and  internal  conformation  of  the  cerebellum  offers 
the  closest  analogies  in  the  domesticated  niammifers.  In  all,  its 
volume,  compared  witli  that  of  the  otiier  encepiialic  lobes,  is  not 
invariable.  Thus,  while  the  relation  between  tlie  weight  of  the  cere- 
bellum and  that  of  the  brain  of  the  Horse  is  as  1  to  7  ;  with  the  Ox 
it  is  as  1  to  9;  with  the  Dog  1  to  8;  with  the  Cat  1  to  6;  and  witii 
the  Sheep  1  to  3.    These  are  the  only  ditierences  to  be  noted 

COMPAKISOX   OF   THE   CEREBELLUM   OF   MAN   WITH   THAT   OF  ANIBIALS. 

In  Man,  the  encephalic  mass  being  enormous,  the  cerebellimi 
is  absolutely  more  considerable  in  volume  than  in  the  larger  domesti- 
cated animals ;  though,  in  proportion  to  the  cerebral  hemispheres,  it 
is  smaller  than  in  the  Ox,  its  relation  to  the  latter  lobes  being  as 
1  to.  8. 

It  is  wider  than  it  is  long,  and  projects  much  beyond  the  medulla 
oblongata.  It  has  three  lobes;  but  these  are  only  visible  on  its 
lower  aspect ;  on  the  opposite  face,  the  median  lobe  is  depressed  and 
concealed  beneatii  the  lateral  lobes,  which  are  so  large  tliat  they 
have  been  named  the  cerebellar  hemispheres.  The  inferior  vermis 
forms  a  free  projection  in  which  is  the  fourth  ventricle;  this  is 
termed  the  uvula  of  the  cerebellum.  The  uvula  is  connected  at  each 
side  with  the  valves  of  Turin:  laminae  of  nerve-substance  lodged  for 
the  most  part  in  tlie  fourth  ventricle,  and  hidden  by  the  lower  face 
of  the  cerebellar  hemispheres.  The  latter  constitute,  on  the  sides  of 
the  medulla  oblongata,  two  prominences  situated  one  below  tlie  other, 
above  the  crura  cerebelli;  the  fii'st  is  designated  the  amygdala  or 
tcijisil,  the  second  the  pneumogastric  lobule  (or  flocculus). 


aii 


THE 
SUB- 


Akticle  IV. — The  Cerebrum. 


SECTION      OF 
CORTICAL 
STANCE    OF    THE 
CEREBELLOI. 

a,  Medullary  sub- 
stance, showing 
its  fibres ;  6,  Sub- 
stantia ferrugi- 
nea,  composed  of 
fibres  and  cell- 
nuclei  ;  c,  Grey 
surface,  granu- 
lar at  the  sur- 
face, and  contain- 
ing large  mul- 
tipolar branch- 
ing cells  near 
the  substantia 
ferrucrinea. 


The  cerebrum,  the  principal  portion  of  the  encephalon, 
comprises  the  two  anterior  lobes  or  hemispheres  of  that 
apparatus :  enlargements  which  are  elongated  in  the  direc- 
tion of  the  great  diameter  of  the  head  and  cranial  cavity, 
lie  beside  each  other  on  the  middle  line,  and  are  united 
at  their  central  part  by  a  transverse  commissure,  and  by 
the  encephalic  isthmus,  whose  anterior  extremity  penetrates,  inferiorly, 
into  their  substance.  (See  Fig.  329  for  a  good  idea  of  this  penetra- 
tion.) 

These  two  lobes  together  represent  an  ovoid  mass,  having  its  thick 
extremity  adjacent  to  the  cerebellum ;  it  is  depressed  from  above  to  below, 
deeply  divided  above,  in  front,  and  behind  by  a  median  antero-posterior 


690 


THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 


fissure,  and  receiving  in  the  middle  of  its  inferior  face  the  insertion  of  the 
cerebral  peduncles. 

This  mass,  seven  to  nine  times  more  voluminous  than  the  cerebellum, 
fills  the  anterior  compartment  of  the  cranial  cavity,  and  thus  occu2)ies  the 
greater  portion  of  that  space. 

It  exliibits  for  study  its  external  conformation,  its  internal  conformation, 
and  its  structure. 

Fio-.  329. 


ANTERO-POSTERIOR   AND   VERTICAL   SECTION   OF   THE   ENCEPHALON   TO   ONE   SIDE 
OF    THE    MEDIAN    LINE. 

1,  1,  Isthmus  of  the  encephalon ;  2,  Medulla  oblongata;  3,  Pons  Varolii;  4,  Cerebral 
peduncle  ;  5,  6,  Corpora  bigemiua ;  7,  Optic  thalamus ;  8,  Pituitary  gland ;  9, 
Pituitary  stem  ;  10,  Optic  nerve  ;  11,  Cerebellum  ;  12,  12,  Cerebral  hemisphere  ; 
13,  Ventricle  of  the  hemisphere  ;  14,  Corpus  striatum  •  15,  Cornu  Ammonis  ;  16, 
Olfiictory  lobe;  17,  Ventricle  of  the  olfactory  lobe. 


EXTERNAL    CONFORMATION    OF    THE    CEREBETJM. 

Instead  of  examining  the  organ  in  mass,  with  regard  to  its  external  con- 
formation, we  will  first  consider  the  great  interlobular  (or  longitudinal) fissure 
which  divides  it  lengthways ;  and  afterwards  study  its  two  lateral  halves, 
or  cerebral  hemispheres,  which  in  reality  constitute  two  symmetrical  organs. 

1.   The  Longitudinal  Fissure. 

This  fissure  exists  throughout  the  vertical  and  antero-posterior  circum- 
ference of  the  cerebrum,  but  does  not  everywhere  ofier  the  same  disposition. 
On  the  superior  aspect  of  the  organ  it  is  very  deep,  and  when  the  two 
hemispheres  are  sejiarated  to  discover  its  extent,  we  see  that  it  reaches  to 
the  upper  face  of  the  great  commissure — the  corpus  callosum.  Behind,  it 
curves  between  the  posterior  lobes  of  the  hemispheres,  but  without  corres- 
ponding directly  with  the  posterior  thick  rounded  margin  of  the  corpus 
callosum,  above  which  there  is  a  feeble  adhesion  established  between  the 
two  halves  of  the  cerebrum,  forming  a  kind  of  bridge.  But  in  front  it  passes 
to  the  anterior  margin  of  this  commissure,  and  is  prolonged  in  the  interval 
of  the  anterior  lobes  of  the  hemispheres  to  reach  the  inferior  face  of  the 
organ. 

Examined  inferiorly,  the  interlobular  fissure  is  well  defined  in  front, 


TRE  CEREBRUM.  G91 

where  it  attains  the  anterior  border  of  the  corpus  callosxim ;  but  behind,  on 
leaving  the  chiasma  of  the  optic  nerves,  and  which  marks  the  anterior  limit 
of  the  isthmus,  this  fissure  appears  suddenly  to  stop.  This  is  because  it 
becomes  considerably  enlarged,  and  is  changed  into  a  vast  notch  which 
admits  the  anterior  extremity  of  the  isthmus :  or  rather,  it  bifurcates  to  pass 
on  each  side  between  the  hemisphere  and  the  anterior  extremity  of  the 
medullary  prolongation,  at  first  crossing  the  optic  nerve,  then  turning  round 
the  cerebral  peduncles  and  corpora  bigemina,  above  which  its  branches 
unite,  and  are  confounded  with  the  undivided  part  of  the  fissui'e,  which 
separates  the  posterior  lobes  of  the  hemispheres. 

There  exists,  then,  around  the  point  of  immergence  of  the  isthmus  in  the 
cerebrum  a  well-marked  line  of  demarcation,  which  constitutes,  above  and 
laterally,  a  very  deep  fissure  in  which  is  imbedded  the  vascular  expansion 
known  as  the  velum  interpositum  ;  this  aperture  is  designated  the  fissure  of 
Bichdt,  or  <ji-eat  (transverse)  cerebral  fissure. 

The  interlobular  fissure  receives  the  longitudinal  septum  of  the  dura 
mater — or  falx  cerebri.  It  also  lodges  arteries  and  veins,  among  which  it 
is  necessary  to  distinguish  tlie  great  vena  Galeni,  which  ascends  from  the 
bottom  of  the  fissure,  after  passing  round  the  posterior  border  of  the  corpus 
callosum. 

2.   TJie  Cerebral  Hemisjjheres. 

Each  hemisphere  or  lateral  moiety  of  the  cerebrum,  represents  an  ovoid 
segment,  in  which  we  may  consider  four  faces  and  two  extremities. 

The  superior  face  is  convex,  and  is  covered  by  the  roof  of  the  cranium, 
which  is  formed  by  the  frontal  and  j^arietal  bones. 

The  external,  eq.ually  convex  and  insensibly  confounded  with  the 
adjacent  faces,  responds  to  the  lateral  walls  of  this  cavity  :  that  is,  with  the 
squamous  portion  of  the  temporal  bone,  the  parietal  and  frontal  bones,  and 
the  ala  of  the  sphenoid. 

The  inferior,  ii-regularly  mammillated,  rests  on  the  sphenoid  bone.  Tlie 
internal  is  plane,  and  for  the  greater  part  of  its  extent  is  related  to  the  other 
hemisphere  through  the  medium  of  the  falx  cerebri ;  it  is  in  its  central  and 
inferior  portion  that  the  union  of  the  two  halves  of  the  cerebrum  takes  place, 
by  means  of  the  great  cerebral  commissure  and  the  anterior  extremity  of  the 
isthmus. 

The  posterior  extremity  of  the  hemisphere  corresponds  to  the  cerebellum, 
which  slightly  depresses  it,  and  from  which  it  is  separated  by  the  transverse 
septum  of  the  dura  mater  (tentorium). 

The  anterior  extremity  or  lobe  is  lodged  in  the  fossa  formed  on  each  side 
of  the  crista  galli  by  the  frontal  and  sphenoid  bones. 

The  anatomical  peculiarities  to  be  found  in  these  different  regions  of  the 
external  surface  of  tlie  hemisphere  are :  1,  On  the  inferior  face,  and  from 
before  to  behind,  a  detached  appendage  constituting  the  olfactory  or  ethmoidal 
lobule,  a  transverse  groove  named  the  fissure  of  Sylvius,  and  an  elongated 
eminence  called  the  mastoid  lobule ;  2,  Everywhere  else,  the  cerebral  convolu- 
tions— depressed  elevations  curved  about  in  a  thousand  ways,  and  separated 
by  sulci  of  varying  depth. 

We  will  study  these  peculiarities  in  an  inverse  order  to  that  of  their 
enumeration. 

1.  Cerebral  Convolutions  (Figs.  321,  322,  327). — The  cerebral  convo- 
lutions are  constituted  by  the  folding  of  the  external  surface  of  the  brain, 
apparently  with  the  intention  of  considerably  augmenting  the  extent  of  that 


692  THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTE3L 

surface.  These  folds,  wliicli  are  very  deep,  are  extremely  irregular  ;  on  the 
surface  of  the  hemispheres  their  disposition  somewhat  resembles  the 
convolutions  of  the  intestines,  a  circumstance  to  which  they  owe  their 
designation.  In  Solipeds  their  number  is  considerable,  and  not  inferior  iu 
this  respect  to  those  on  the  human  brain. 

Notwithstanding  their  great  irregularity,  the  cerebral  convolutions  offer 
a  somewhat  constant  arrangement ;  so  that  it  is  possible  to  describe  them 
one  by  one.  This  has  been  done  in  human  anatomy  ;  but  it  would  be  need- 
less to  repeat  the  task  in  the  case  of  the  domesticated  animals. 

2.  Mastoid  or  Sphenoid  Lobule  (Fig.  285,  l). — This  is  a  large  pyriform 
eminence,  corresponding  to  what  has  been  described  in  Man  as  the  inferior 
(or  middle)  lobe  of  the  hemisphere,  and  occupies  the  posterior  part  of  the 
inferior  face  of  the  hemisphere.  This  eminence  is  curved  upon  itself,  and 
shows  its  convexity  outwards.  Its  internal  border,  which  corresponds  to 
the  cerebral  peduncle,  concurs  in  the  formation  of  the  great  transverse 
fissure.  Its  large  extremity  is  turned  forward,  and  margined  by  the  fissure . 
of  Sylvius.  The  posterior  extremity  insensibly  disappears  on  the  inner 
side  of  the  posterior  lobe  of  the  hemisphere. 

This  eminence  ought  to  be  considered  as  a  large  projecting  convolution. 
It  is  excavated  internally  by  a  cfecal  cavity,  which  constitutes  the  bottom 
of  the  posterior  or  reflected  portion  of  the  lateral  ventricles. 

3.  Fissure  of  Sylvius. — Thus  is  designated  a  transverse  depression 
situated  in  front  of  the  optic  nerve  and  mastoid  lobule,  in  which  is  lodged 
the  middle  cerebral  artery. 

4.  Olfactory  or  Ethmoid  Lobule  (Figs.  321,  6;  322,  1;  327,  26; 
329,  16). — The  appendage  to  which  this  name  is  given  is  detached  from 
the  inferior  face  of  the  hemisphere,  where  it  arises  by  two  white-coloured 
roots ;  the  external  of  these  is  continuous  with  a  long  convolution  that 
borders  the  outside  of  the  mastoid  lobule,  while  the  infernal,  the  shortest, 
orio'inates  on  the  inner  face  of  the  hemisphere,  in  advance  of  the  optic 
chiasma.  Between  these  roots  appears  a  prominent  surface  of  a  triangular 
form,  constituting  the  extra-ventricular  nucleus  of  the  corpus  striaium  (substantia 
perforata).  The  appendage  thus  formed  jiasses  forward,  terminating 
in  an  oval  enlargement  (hulbus  olfactorius)  extending  much  beyond  the 
anterior  extremity  of  the  brain,  to  be  lodged  in  the  ethmoid  fossa. 

The  olfactory  lobe  possesses  an  internal  cavity,  a  diverticulum  of  the 
lateral  ventricle  (Fig.  322,  2).  Both  lobes  being  regarded  as  the  first  pair 
of  cranial  nerves,  we  will  return  to  their  description  when  studying  the 
encephalic  nerves. 

internal  conformation  of  the  brain. 

In  separatingt  he  cerebral  hemispheres  by  their  upper  face,  we  discover 
the  great  commissure  known  as  the  corpus  callosum :  the  first  object  that 
presents  itself  for  study  in  the  internal  conformation  of  the  brain. 

If  we  afterwards  remove,  by  a  horizontal  section,  and  with  a  sharp 
instrument,  all  that  portion  of  the  hemispheres  which  covers  this  commissure, 
and  also  if  the  latter  be  excised  to  a  certain  extent  to  the  right  and  left  of  the 
median  line,  we  will  penetrate  two  symmetrically  disposed  cavities  in 
the  centre  of  each  hemisphere.  These  cavities  are  the  lateral  or  cerebral 
ventricles. 

They  are  separated  on  the  middle  plane  by  a  thin  partition — the  septum 
lucidum,  which  is  attached  to  the  corpus  callosum  by  its  upper  border,  and 
fixed  by  its  inferior  border  into  the  fornix,  a  kind  of  median  arch  beneath 


THE  CEREBRUM. 


693 


Fig.  330 


wliich  is  the  foramen  of  Monro,  or  orifice  communicating  with  the  two  ven- 
tricles. On  the  floor  of  these  cavities  is  observed  two  large  eminences,  the 
co7-j)HS  striatum  and  the  hipjiocampus  ;  with  a  vascular  and  ajiparently  granu- 
lated cord  forming  the  cerebral  choroid  plexus,  a  dependency  of  the  velum  inttr- 
positum. 

It  now  remains  to  enter  into  some  detail  with  regard  to  the  anatomical 
characteristics  of  all  these  pai'ts. 

1.   Tlie  Corpus  Callomm.     (Figs.  327,  330.) 

The  corpus  callosum  is  a  kind  of  arch  thrown  over  the  two  lateral  ven- 
tricles, while  at  the  same  time  it  is  a  commissure  uniting  the  two  hemispheres. 
It  belongs  exclusively  to  mammalia. 

Composed  entirely  of  white  substance,  it  affects  a  quadrilateral  form, 
being  elongated  in  an  antero-posterior  direction,  and  thus  presents  for  study 
two  faces,  two  borders,  and  two  extremities. 

The  superior  face,  free  in  the  middle,  and  corresponding  to  the  bottom 
of  the  interlobular  fissure,  is  covered  right  and  left  by  the  substance  of  the 
hemispheres.  It  is  traversed  from  before  to  behind  by  two  white,  and 
generally  very  delicate,  cords,  the  tractus  longitiidinalis  (the  chordoe 
longitudinalis  of  Lancisii)  of  the  corpus  callosum,  which  lie  together  on  the 
middle  line.  The  inferior  face  is 
divided  by  the  insertion  of  the  sep- 
tum lucidum  into  two  lateral  por- 
tions, each  of  which  forms  the  roof 
of  one  of  the  cerebral  ventricles. 

The  two  lateral  borders  of  the 
corpus  callosimi  disappear  in  the 
central  substance  of  the  hemis- 
pheres, where  it  is  almost  impos- 
sible to  distinguish  their  limits. 

The  posterior  extremity  appears 
at  the  bottom  of  the  interlobular 
fissure,  after  the  destruction  of  the 
adhesion  usually  established  above 
it  between  the  two  hemispheres,  in 
the  form  of  a  thick,  rounded  en- 
largement (splenium)  folded  in 
genu,  below,  and  confounded  with 
the  middle  part  of  the  fornix.  It 
is  prolonged,  laterally,  above  the 
ventricular  cavities,  by  forming  two 
angles  {linece  transversce)  which  are 
soon  lost  in  the  white  central  sub- 
stance of  the  cerebrum. 

The  anterior  extremitij  comports 
itself  in  a  similar  manner  between 
the  anterior  lobes  of  the  hemi 
spheres. 

2.   Tlie  Lateral  or  Cerebral  Ventricles.     (Figs.  325,  331.) 

The  lateral  ventricles  are  two  large  elongated'  cavities  excavated  in  the 
hemispheres,  lying  against  each  other  in  their  anterior  moiety,  and  divergent 
in  their  posterior  part,  which  is  very  much  curved  backwards,  outwards,  and 
downwards,  to  open  into  the  substance  of  the  mastoid  lobule. 
47 


THE  CORPUS  CALLOSUM,  AFTER  REMOVAL  OP 
THE  UPPER  PORTION  OF  THE  CEREBRAL 
HEMISPHERES. 

1,  Centrum  ovale  of  Vieussens ;  2,  2,  Chordae 
longitudinales ;  4,  4,  Cornua,  or  angles  of  the 
posterior  extremity ;  5,  5,  Ditto  of  auierior 
e.xtremity. 


09 1  THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 

This  disposition  permits  the  clivisiou  of  the  cerebral  ventricles  into  two 
regions :  an  anterior,  and  a  posterior  or  reflected. 

The  anterior  region  is  separated  in  the  median  plane  from  the  opposite 
ventricle,  by  the  septum  lucidum  and  the  summit  of  the  fornix,  beneath 
which  is  the  foramen  of  Monro  establishing  a  communication  between  the 
middle  and  the  two  lateral  ventricles,  and  between  these  latter.  Above,  it 
offers  a  smooth  wall  formed  by  the  corpus  callosum.  Below,  on  its  floor, 
there  is  first  remarked,  in  front,  the  corpus  striatum ;  behind,  the  internal 
portion  of  the  hippocampus  ;  in  the  middle,  au  oblique  groove  running  from 
behind  to  before,  and  without  inwards,  at  the  bottom  of  which  floats  the 
choroid  plexus.  The  anterior  extremity  of  this  region,  occupied  by  the 
base  of  the  corpus  striatum,  is  continued  by  a  narrow  opening  into  the 
interior  of  the  olfactory  lobe.  The  posterior  is  prolonged,  without  any  line 
of  demarcation,  by  the  reflected  portion  of  the  ventricular  cavity. 

The  latter  region  occupies  the  most  declivitous  portion  of  the  posterior 
lobe  of  the  hemisphere,  and  presents  a  strongly  curved  canal  whose  con- 
cavity looks  forward ;  this  canal  terminates  in  a  cul-de-sac  in  the  substance 
of  the  mastoid  lobule.  On  the  floor  of  this  canal  is  delineated  the  posterior 
portion  of  the  hippocampus  and  the  choroid  plexus. 

A  very  fine  membrane — the  ventricular  arachnoid — plays  the  part  of  a 
serous  membrane  and  covers  the  walls  of  these  cavities,  being  spread  every- 
where over  a  layer  of  white  substance,  prolonged  into  the  ethmoidal  diverti- 
culum, and  continuous,  through  the  foramen  of  Monro,  with  that  of  the  middle 
ventricle.  This  membrane  secretes  a  limpid  and  transparent  liquid,  analogous 
to  the  cerebro-spinal  fluid,  though  in  health  it  is  always  in  small  quantity. 

3.  The  Septum  Lucidum.  (Fig.  327,  24.) 
This  appellation  is  given  to  a  thin  median  lamella,  standing  vertically 
between  the  two  lateral  ventricles,  elongated  from  before  to  behind,  widened 
considerably  at  its  anterior  extremity,  terminating  in  a  point  at  its  posterior 
extremity,  and  inserted  above  into  the  corpus  callosum,  below  into  the  back 
of  the  fornix. 

On  the  faces  of  this  lamella,  which  is  formed  of  white  substance,  is 
spread  the  proper  membrane  of  the  lateral  ventricles.  In  the  human  species, 
a  narrow  ventricular  cavity  has  been  described  as  found  in  its  substance ; 
but  this  does  not  appear  to  exist  in  our  domesticated  animals. 

4.  The  Fornix  {or  Trigoniim).     (Fig.  313,  3. ) 

Also  named  the  vaidt  of  three  or  four  arches,  the  fornix  (arcJi)  is  a  single 
and  median  body  in  the  interior  of  the  brain,  concurring  to  separate  the  two 
ventricles,  and  serving  to  support  the  septum  lucidum.  It  is  depressed  from 
below  to  above,  and  is  of  a  triangular  form ;  its  apex,  looking  downward,  stands 
in  the  median  plane  above  the  foramen  of  Monro  and  the  thalami  optici, 
though  sej)arated  from  the  latter  by  the  velum  interpositum  and  the  hippo- 
campi, and  receives  on  its  upper  face  the  insertion  of  the  septum  lucidum. 
Behind,  towards  its  base,  and  on  the  median  plane,  the  fornix  is  confounded 
with  the  corpus  callosum,  which  it  supports ;  it  is  prolonged  on  each  side 
by  a  lamina  extending  to  the  surface  of  the  hippocampus,  forming  the 
cortical  layer  of  this  deep  convolution  of  the  brain,  and  with  its  congener 
constituting  the  posterior  pillars  {posterior  crura,  or  corpora  fimhriata)  of  the 
fornix. 

In  front,  at  its  apex,  the  fornix  is  also  attached  to  the  corpus  callosum, 


THE  CEREBRUM.  C95 

and  divides  into  two  cords  or  anterior  pillars  (crura)  (Fig.  323,  17),  wliicli 
pass  in  front  of  the  anterior  cerebral  commissure,  are  inflected  downwards 
and  backwards,  in  traversing  the  optic  thalamus,  on  the  sides  of  the  middle 
ventricle,  and,  finally,  have  their  extremities  confounded  with  the  mammillary 
process  (corpus  albicans). 

These  two  crura  limit,  in  front,  the  foramen  commune  anterius  or  foramen 
of  Monro,  over  which  the  apes  of  the  fornix  is  thrown  across  like  an  arch. 

The  fornix  is  white  throughout  its  whole  extent,  with  a  greyish  tint 
towards  its  summit. 

5.  The  Hippocampi.     (Fig.  331,  4.) 

The  hippocampus  or  cor^iu  Ammonis  (from  its  resemblance  to  a  ram's 
horn,  the  crest  of  Jupiter  Ammon),  is  an  elongated  projection,  a  veritable 
internal  convolution  of  the  brain  (is,  in  fact,  the  internal  surface  of  the 
gyrus  fornicatus  or  convolution  lying  upon  the  corpus  callosum,  and  which 
terminates  at  the  fissm'e  of  Sylvius)  ;  it  occupies  the  floor  of  the  anterior 
region  of  the  lateral  ventricle,  and  is  prolonged  throughout  its  reflected  por- 
tion, whose  curvature  it  exactly  follows.  Considered  together,  the  two 
hippocampi  somewhat  closely  resemble  the  uterine  cornua  of  the  Cow. 

By  their  internal  extremity,  they  are  in  contact  with  each  other  beneath 
the  middle  portion  of  the  fornix,  and  above  the  optic  thalamus,  which  is  sepa- 
rated from  them  by  the  velum  interpositum  (Fig.  327,  9).  Their  external 
extremity  occupies,  in  the  mastoid  lobule,  the  cul-de-sac  of  the  reflected 
portion  of  the  lateral  ventricle. 

The  central  mass  of  this  projection  is  formed  by  a  nucleus  of  grey  sub- 
stance, covered  superficially  by  a  cortical  layer  of  white — a  prolongation  of 
the  posterior  crura  of  the  fornix. 

Towards  the  concave  border  of  the  hippocampus,  this  white  lamina 
offers  a  kind  of  wide  hem,  beneath  which  the  choroid  plexus  passes ;  this 
hem  constitutes  a  small  curved  band,  like  the  cornu  Ammonis,  wider  at  its 
middle  part  than  at  its  extremities,  and  is  named  the  corpus  fimbriaium,  or 
tcenia  hippocampus. 

6.  The  Corpora  Striata.     (Fig.  331,  7.) 

The  coi'pus  striatum  is  another  projection  on  the  floor  of  the  cerebral 
ventricle,  occuj^ying  the  anterior  region  of  that  cavity. 

This  eminence  is  pyriform  in  shape,  and  obliquely  elongated  from  behind 
to  before,  and  without  to  within.  Its  surface  is  smooth,  and  regularly  convex. 
Its  base,  or  anterior  extremity,  corresponds  to  the  anterior  caecum  of  the 
ventricle.  The  summit,  or  posterior  extremity,  disappears  at  the  commence- 
ment of  the  reflected  portion  of  the  ventricular  cavity.  Outwardly,  the 
corpus  striatum  is  limited  by  a  groove  that  forms  the  angle  of  union  between 
the  floor  and  roof  of  the  ventricle.  Inwardly,  it  is  separated  from  the  optic 
thalamus  and  cornu  Ammonis  by  another  sulcus,  in  which  the  choroid 
plexus  floats,  and  which  is  oblique  inwards  and  forwards,  and  shows  at  the 
bottom  the  tcenia  semicircularis  (Fig.  323,  13).  This  is  a  flattened  white 
cord,  which  disappears  inwardly  towards  the  foramen  of  Monro,  and  bends 
outwards  along  the  optic  nerve  to  within  about  3-8ths  of  an  inch  from  the 
chiasma ;  in  this  way  forming  a  sort  of  cii'cular  band  around  the  anterior 
extremity  of  the  isthmus,  beneath  which  all  the  fibres  of  the  latter  pass  to 
reach  the  cerebral  hemispheres. 

The  corpus  striatum  owes  its  name  to  its  structure,  being  composed  of  a 


696 


THE  CENTRAL  AXIS  OF  THE  NERVOUS  SYSTEM. 


Fis:.  331. 


thick  nucleus  of  grey  substance  that  crosses  the  longitudinal  fibres  of  the 
encephalic  isthmus  in  passing  into  the  hemispheres;  these  fibres  apjicar  in 
several  points  of  this  nucleus  as  very  distinct  white  streaks. 

This  deep  nucleus,  which  is  in- 
termediate to  the  superior  extremity 
of  the  isthmus  and  the  principal 
mass  of  the  hemisphere,  comprises 
the  entire  thickness  of  the  floor  of 
the  lateral  ventricle,  and  projects 
outwards,  beneath  the  inferior  face 
of  the  hemisphere,  between  the  two 
roots  of  the  olfactory  lobe,  where 
it  constitutes  the  extra-ventricular 
nucleus  of  the  corpus  striatum :  so 
named  in  contradistinction  to  the 
oblong  eminence  in  the  interior 
of  the  ventricle,  which  is  often  de- 
signated the  intra-ventricular  nucleus 
of  the  corpus  striatum. 

7.     TJie    Velum    Interpositum    and 
Choroid  Plexus.     (Fig.  331,  G.) 

ANTERIOR  PORTION  OF  THE  LATERAL  vENTRi-  Thc  vclum   interposttum^  (vclum 

CLEs  OP  THE  DOG,  EXPOSED  BY  REM  OVAL  OF  vascidosum,  tela  choroidca)  is  a  vas- 

THE  ROOF.  cular  expansion  dependent  from  the 

1,   Corpus   callosum;   2,   Anterior   part  of  the  pja    mater,    which    penetrates    the 

corpus  callosum,  turned  forward  after  destruc-  ^^^:^.^^  \^„  ^\^q  transverse  fissure,  and 

tion  of  the  septum  lucidum,  to  show  the  fornix,  .      .         7        -i.     ^£  ^    j. „    4.u„    ii,„ 

3,  3;  4,  4,  Hippocampi;  5,  5,  Taenia  semi^   insinuates _ itself  between  the  tha- 

circularis ;  6,  6,  Choroid  plexus ;  7,  7,  Corpora    lamus    opticus  and  the  convolution 
striata.  of  the  cornu  Ammonis.    The  velum, 

on  arriving  beneath  the  tasnia  hip- 
pocampus, terminates  in  the  choroid  plexus :  a  red,  granular-looking  cord, 
which  is  suspended  by  its  antero-external  border,  and  projects  into  the 
interior  of  the  lateral  ventricle. 

The  choroid  plexuses  of  the  train  extend  from  the  anterior  extremity  of 
the  corpus  striatum  to  the  bottom  of  the  ca',cum  in  the  mastoid  eminence 
or  lobule.  In  the  anterior  region  of  the  ventricle,  they  occupy  the  oblique 
sulcus  which  traverses  that  part,  to  the  inner  side  of  the  corpus  striatum. 
In  the  posterior  region,  they  float  in  front  of  the  cornu  Ammonis.  Their 
anterior  or  internal  extremity,  more  voluminous  than  the  external,  always 
forms  a  small  appendage  which  remains  quite  free.  They  are  united  to 
each  other,  near  this  extremity,  by  an  intermediate  cord,  which  traverses 
the  foramen  of  Monro  in  passing  beneath  the  fornix. 

Like  the  velum  interpositum,  the  choroid  plexuses  are  formed  by  a  net- 
work of  arteries  and  veins.  They  are  often  incrusted  in  calcareous  matter, 
and  may  be  the  seat  of  more  or  less  voluminous  cysts. 

The  veins  proceeding  from  this  vascular  apparatus  are  very  voluminous, 
and  by  their  union  form  the  great  vena  Galeni,  which  bends  round  the 
sjilenium  of  the  corpus  callosum  to  reach  the  interlobular  fissure,  and  pro- 
ceeds to  the  sinus  of  the  falx  cerebri. 


THE  CEBEBBUM. 


697 


Fis:.  332. 


STRUCTURE    OF    THE    CEREBRUM. 

The  structure  of  the  brain  is  certainly  one  of  the  most  interesting  points 
in  the  study  of  the  nervous  centres;  for  on  a  perfect  knowledge  of  it 
depends  the  solution  of  the  most  difficult  problems  in  the  physiology  of  the 
nervous  system.  Numerous  attempts  have  been  made  to  elucidate  its 
intimate  organisation  ;  but  we  must  here  omit  the  multitude  of  secondary 
details  revealed  by  these  researches,  and  limit  ourselves  to  the  essential 
and  fundamental  facts. 

The  two  substances  enter  into  the  texture  of  the  cerebral  hemispheres, 
and  both  are  exactly  disposed  as  in  the  cerebellum. 

The  grey  substance  extends  over  the  entire  external  surface  of  the  brain, 
and  dips  into  the  sulci ;  thereby  augmenting  the  extent  of  that  surface,  and 
forming  the  cortical  layer  of  the  cerebral  convolutions.  This  layer,  it  is 
necessary  to  remark,  though  perfectly  similar  to  that  of  the  cerebellar 
lobules,  is  not  homogeneous  throughout  its  tliickness,  but  may  be  decom- 
posed into  several  secondary  stratified  layers,  between  which  are  extremely 
thin  lamellfe  of  white  substance ;  one  of  these  lamellae  nearly  everywhere 
forms  the  most  supei-ficial  pellicle  of  the  convolutions. 

According  to  Kolliker,  there  are  six  layers  in  the  cortical  substance  of 
the  brain,  and  these  are  disposed  as  follows :  1,  A  superficial  white  layer ; 
2,  Grey  layer;  3,  First  Avhite  streak;  4,  Yellowish-red  layer,  external 
portion ;  5,  Second  white  streak  ;  6,  Yellowish-red  layer — internal  portion. 
In  all  these  layers  are  nerve-cells,  but  in  proportion  as 
they  are  pale,  these  cells  are  few  and  small ;  the  cells 
themselves  contain  colouring  matter  in  the  reddish- 
yellow  layers.  Everywhere  they  are  furnished  with 
from  one  to  five  fine  prolongations,  which  bring  them  into 
communication  with  the  very  fijie  nerve-tubes  of  the 
cerebral  hemispheres.  (Lockhart  Clarke  gives  seven 
layers  for  this  cortical  substance.) 

In  the  middle  of  each  hemisphere,  the  white  substaiice 
constitutes  a  considerable  nucleus,  which,  from  its  form, 
is  named  the  centrum  ovale  of  Vieussens  (Figs.  325,  1 ; 
330,  1),  and  which  is  imited  to  that  of  the  opposite  side 
by  the  great  cerebral  commissure,  or  corpus  callosum, 
sending  a  prolongation  into  each  convolution ;  thus  ex- 
hibiting the  exact  disposition  of  the  lateral  white  masses 
of  the  cerebellum,  with  which  the  nuclei  of  the  hemi- 
spheres have  also  another  point  of  resemblance,  in  tliat 
they  are  attached  to  the  cerebral  peduncles,  as  the  first  are 
to  the  cerebellar.  But  the  latter  peculiarity  is  less  evident   cortical    substance 

OF    THE     CEREBRAL 
HEMISPHERES. 

Medullary  sub- 
stance ;  6,  Reddish- 
grey  layer ;  c,  Clear 
white  streak,  com- 
posed of  horizontal 
fibres ;  d,  Grey  layer ; 
<?,  External  white 
layer. 


than  the  others — which  are  at  once  obvious  in  horizontal 
and  transverse  sections  of  the  brain — and  can  only  be 
clearly  demonstrated  by  the  manipulations  necessary  to 
unravel  the  intimate  texture  of  the  white  substance. 

In  studying  this  texture  in  brains  hardened  by  nitric 
acid,  washed  in  pure  water,  and  exposed  to  dry  air  for 
a  day  or  two,  we  perceive  that  the  white  cerebral  sub- 
stance is  entirely  composed  of  fine  fibrous  lamellae, 
diverging  in  every  direction,  corresponding  by  their  con- 
centric extremity  to  the  centre  of  the  hemisphere,  and  abutting,  by  their 


698  THE  CENTS AL  AXIS  OF  THE  NERVOUS  SYSTEM. 

pei'iplieral  extremity,  on  the  inner  face  of  the  grey  covering  of  the  con- 
volutions. 

The  fibres  of  the  white  substance  of  the  hemispheres  are  connected  with 
those  of  the  encephalic  isthmiis,  through  the  latter  being  prolonged  into  the 
texture  of  the  corpus  striatum,  where  they  apj)ear  either  in  the  form  of  striae, 
or  as  an  elongated  nucleus,  known  as  the  double  semicircular  centre  of  Vieus- 
sens  ;  they  then  pass  to  the  outside  of  the  ventricular  cavity,  and  plunge  into 
the  centrum  ovale  of  the  hemisphere,  where  they  are  manifestly  continued  by  a 
portion  of  the  fibres  constituting  it.  It  has  been  said  that  these  fibres,  instead 
of  thus  disappearing  in  the  hemisphere,  ascend  at  first  to  the  right  and  left 
on  the  external  side  of  the  lateral  ventricle,  and  are  afterwards  inflected  in- 
wards above  that  cavity,  to  join  on  the  median  line  ;  and  in  this  way  form  the 
corpus  callosum.  I  have  searched  for  this  arrangement  in  our  domesticated 
animals,  and  particularly  in  the  Dog,  whose  brain  is  well  adapted  for  study- 
ing the  corpus  callosum,  but  without  success.  It  has  always  appeared  to 
me  that  the  extremities  of  the  transverse  fibres  which  form  this  great  com- 
missure are  lost  in  the  white  substance  of  the  hemispheres,  some  passing 
above,  the  others  below ;  and  I  believe  I  have  also  seen  some  of  the  pedun- 
cular fibres  radiating  in  the  centrum  ovale  becoming  insinuated  between  the 
extremities  of  the  fasciculi  of  the  corpus  callosum,  to  gain  the  sujierior  part 
of  the  hemisphere,  without  being  continuous  in  any  way  with  these  fasciculi. 

Some  of  the  nerve-tubes  certainly  terminate  in  the  corpus  callosum; 
but  in  this  there  is  nothing  extraordinary,  as  in  that  layer  there  are  nuclei 
and  some  nerve-cells. 

DIFFERENTIAL   CHARACTERS   OF   THE   CEREBRUM   IN   OTHER   THAN   SOLIPED    ANI3IALS. 

The  brain,  in  tiie  animals  now  referred  to,  offers  some  differences  in  volume,  as  might 
be  inferred  from  what  has  been  said  regarding  its  relations  with  the  cerebellum.  lu  all, 
its  development  posteriorly  is  not  so  considerable  that  it  covers  the  latter,  which  always 
remains  exposed. 

Its  general  form  varies  a  little.  In  the  Ox,  the  hemispheres  are  proportionately 
larger  posteriorly  than  in  the  Horse,  but  contract  suddenly  at  the  fissure  of  Sylvius, 
preserving  their  reduced  dimensions  in  the  anterior  lobes  ;  the  latter  are  therefore  more 
conical  than  in  Solipeds.  The  cerebrum  of  the  Dog  is  regularly  ovoid,  except  at  Ihe 
extremity  of  the  anterior  lobes  ;  there  the  hemispheres  become  much  flattened  from  one 
side  to  the  other,  and  form  a  kind  of  spur  that  enters  the  ethmoidal  fossse. 

The  cerebral  convolutions  are  a  little  larger  in  the  Ox  than  in  the  Horse,  but  they  are 
also  less  numerous ;  they  are  still  fewer  in  the  Pig.  and  yet  less  in  the  Carnivora ;  we 
will  see  hereafter  that  they  are  absent  in  Birds.  Tlie  particular  features  of  the  lower 
face  of  the  hemispheres  are  the  same  in  all  the  species;  except  that  the  olfartory  lobes 
are  more  detached  than  in  Solipeds  ;  they  are  remarkably  developed  in  the  Dug. 

The  ventricles  are  the  same  in  all ;  the  floor  is  always  fomied  by  the  corpus  striatum, 
hippocampus,  and  thalami  optici,  the  roof  by  tlie  corpus  callosum.  In  the  Ox.  the  band 
of  the  hippocampus  is  remarkable  for  its  width ;  in  the  Dog,  the  corpus  striatum,  pro- 
portionately voluminous,  is  of  a  deep  grey  colour  on  its  surface. 

COMPARISON   OF   THE    CEREBRUM   OF   MAN   WITH   THAT   OF   ANIMALS. 

The  cerebrum  of  Man  (Fig.  333)  is  distinguished  by  its  regularly  ovoid  shape,  and 
its  great  development,  particulary  behind,  where  it  covers  the  cerebellum — a  feature 
never  observed  in  animals. 

Viewed  superiorly,  a  cerebral  hemisphere  is  clearly  divided  into  three  lobes:  an 
(interior  or  frontal;  a  middle  or  sphenoidal,  corresponding  to  the  mastoid  lobule  of  the 
Horse ;  and  ?l  posterior  or  occipital,  covering  the  cerebellum.  The  two  first  are  separated 
by  a  narrow,  deep,  and  sinuous  ^ssure  vf  Sylvius. ■ 

The  convolutions  are  larger,  and  separated  by  deeper  fuirows,  than  those  of  the 
Horse,  but  they  are  not  more  numerous.  The  olfactory  lobes  arise,  as  in  animals,  from 
two  orders  of  roots,  but  they  are  small  and  entirely  hidden  beneath  the  inferior  face  of 
the  frontal  lobes. 


THE  CEREBRUM. 


699 


The  corptts  callosum  is  very  developed,  and,  above  the  ventricle,  forms,  from  before  to 
behind,  a  salient  auj^ular  prolongation  named  the  frontal  cornu  and  occipital  prolonga- 
tion, or  forceps  major. 

There  is  notliing  to  note  concerning  ihe  fornix  and  septum  lucidum,  except  that  thero 
is  a  veutricle  in  tho  latter  which  communicates  with  the  middle  ventricle  by  a  small 
aperture,  the  vulva. 

The  lateral  ventricles  offer  remarkable  differences.  They  are  not  prolonged  into  the 
olfactory  lobes,  but  po.-sess  a  diverticulum  tlmt  enters  the  occipital  lobe,  below  tho 
forceps  major.  Tiiis  space  is  more  or  less  developed,  and  terminates  in  a  point ;  it  is 
named  the  ancyroid  or  digital  cavity,  and  shows  on  its  floor  a  small  convolution  which 

Fiff.  333. 


THE   BASE   OF   THE   HtTlIAN    BRAIN. 

1,  Longitudinal  fissure ;  2,  Anterior  lobes  of  cerebrum ;  3,  Olfactory  bulb ;  4, 
Lamina  cinerea ;  5,  Fissure  of  Sylvius ;  6,  Locus  perforatus  anticus ;  7,  Optic 
commissure;  8,  Tuber  cinereum ;  9,  Third  nerve;  10,  Corpus  albicantium ;  11, 
Fourth  nerve  ;  12,  Locus  perforatus  posticus  ;  13,  Fifth  nerve  ;  14,  Crus  cerebri ; 
15,  Sixth  nerve;  16,  Pons  Yarolii ;  17,  Portio  dura  of  seventh  nerve;  18,  Middle 
lobe  of  cei-ebrum  ;  19,  Portio  raolliss  of  seventh  nerve;  20,  Anterior  pyramid; 
21,  Glosso-pharyngeal  nerve;  22,  OHvary  body;  23,  Pneumogastric  nerve;  24, 
Lateral  tract ;  25,  Spmal  accessory  nerve ;  26,  Digastric  lobe ;  27,  Hypo- 
glossal nerve ;  28,  Cerebellum ;  29,  Amygdala ;  30,  Slender  lobe ;  32,  Posterior 
inferior  lobe. 


has  been  designated  the  ergot  of  Morand  (pes  Mppocampi').  The  diverticulum  and  con- 
volution do  not  exist  in  animals.  The  cornu  Ammonis  is  slightly  bosselated  on  its 
surface ;  it  is  limited,  inwardly,  by  a  baud,  and  below  this  by  a  grey  denticulated 
lamina,  the  gyrtis  fomicatus. 

The  other  portions  of  the  human  brain  resemble  those  of  animals ;  so  that  it  is 
needless  to  allude  to  them. 


700  THE  NERVES. 

THIRD  SECTION. 

The  Nerves. 

The  nerves  represent  the  peripheral  portions  of  the  nervous  system,  and 
are  cords  ramifying  in  every  part  of  the  body,  having  their  origin  in  the 
medullary  axis  or  its  encephalic  prolongation.  Before  commencing  their 
special  study,  it  is  necessary  to  possess  a  summary  notion  of  the  principal 
distinctions  of  which  they  are  susceptible,  with  regard  to  their  origin, 
distribution  and  termination. 

Structure. — The  nerves  are  formed  by  an  aggregation  of  the  nerve-tubes 
already  described.  These  are  grouped  in  primary  fasciculi,  which  are 
rectilinear  or  slightly  undulating,  and  enveloped  in  a  sheath  of  delicate  con- 
nective tissue — ^the  perineurium.  These  primary  fasciculi  are  again  assem- 
bled in  bundles  to  compose  secondary  fasciculi,  which  are  maintained  by  a 
layer  of  fibrous  connective  tissue  thicker  than  the  perineurium.  Finally, 
these  secondary  bundles  by  their  union  constitute  the  nerve,  around  which 
the  connective  tissue  becomes  condensed,  and  found  the  neurilemma. 

Vessels  traverse  the  connective  tissue  separating  the  fasciculi  from  each 
other ;  they  anastomose  in  a  network  whose  elongated  meshes  are  parallel 
with  the  nerve-tubes,  and  they  are  also  surrounded  by  the  nervi  nervorum. 

Ou  the  track  of  ceiiain  nerves  is  observed  a  greyish  enlargement,  or 
ganglion.  This  is  composed  of  a  mass  of  nerve-cells,  which  are  generally 
bipolar,  and  are  situated  on  the  course  of  the  tubes.  It  is  not  quite  known 
whether  some  of  these  tubes  are  not  merely  placed  alongside  the  ganglion. 

Division. — Nerves  are  divided,  with  reference  to  their  destination, 
into  two  principal  groups:  1,  The  cerebrospinal  or  nerves  of  animal  life; 
2,  The  ganglionic  or  nerves  of  organic  life. 

Cerebro-spinal  Nerves. — These  emanate  directly  from  the  cerebro- 
spinal axis,  and  are  divided  into  two  secondary  groups:  1,  The  cranial 
or  encephalic  nerves,  which  originate  in  the  encephalon,  and  make  their  exit  by 
the  foramina  at  the  base  of  the  cranium,  to  be  distributed  almost  exclusively 
in  the  head ;  2,  The  spinal  or  rachidian  nerves,  arising  in  the  spinal  cord, 
and  passing  to  the  muscular  or  tegumentary  parts  of  the  trunk  and  limbs, 
through  the  intervertebral  foramina. 

After  what  has  been  said  in  regard  to  the  apparatus  of  innervation,  we 
know  that  the  fibres  composing  these  cords  are  distinguished,  by  their  point 
of  origin  and  their  properties,  into  fibres  of  superior  origin  or  of  centripetal 
conductibilify,  and  fibres  of  inferior  origin  or  of  centrifugal  conductibility.  The 
first  have  a  ganglion  on  their  course. 

The  cerjbro-spinal  nerves  are  exclusively  formed  of  the  first  description 
of  fibres,  and  are  named  sensitive  nerves,  as  they  conduct  the  stimulus  which 
brings  into  play  the  sensibility  of  the  brain.  They  are  distinguished 
as  nerves  of  general  sensibility  and  nerves  of  special  sensatioyis  (or  sense).  The 
first  are  destined  to  convey  all  stimuli  except  those  determined  by  light, 
sounds,  or  odoriferous  particles ;  the  second  exclusively  conduct  the  latter. 

The  nerves  which  are  composed  only  of  fibres  of  the  second  kind  are 
called  motor  nerves,  because  it  is  they  which  carry  to  the  muscles  the 
spontaneous  stimulus  to  motion  originated  by  the  will. 

Those  which  are  composed  at  once  of  motor  fibres  and  fibres  of 
general  sensibility  constitute  the  mixed  nerves;  these  form  the  largest 
category. 


THE  NERVES.  701 

Ganglionic  Nerves. — These  nerves,  collectively  rcprcFenfng  the  great 
sympathetic  system,  form  below  and  on  the  sides  of  the  spine,  two  long  cords, 
rendered  moniliforni  by  the  presence  of  ganglionic  enlargements,  and  in 
the  constitution  of  which  nearly  all  the  cerebro-spinal  nerves  concur ;  their 
ramifications,  frequently  ganglionic  also,  are  destined  to  the  viscera  of  tho 
neck,  the  thorax,  and  the  abdomen. 

In  these  nerves  of  organic  life  are  found  the  two  kinds  of  nerve-tubes,  or 
fibres  of  centripetal  and  centrifugal  conductibility. 

But  these  tubes  appear  to  have  only  very  indirect  relations  with  the 
brain,  for  the  will  has  no  influence  over  the  oi'gans  which  receive  their 
nervous  fibres  from  the  great  sympathetic  ;  and,  besides  this,  in  health,  tho 
excitations  developed  in  these  organs  are  all  reflected  by  the  spinal  cord, 
and  do  not  provoke  in  any  way  the  special  activity  of  the  encephalon — they 
are  not  felt. 

As  the  nerves  of  the  great  sympathetic  system  are  principally  formed  of 
fine  tubes,  we  ought  perhaps  to  seek  in  this  anatomical  condition  the  cause 
of  the  special  properties  of  these  nerves ;  what  tends  to  make  this  appear 
likely  is  the  fact,  that  the  cerebro-spinal  nerves  contain  some  of  these 
tubes  in  their  elements,  and  that  they  share,  with  the  ganglionic  ramuscules, 
the  faculty  of  bringing  into  play  the  reflex  power  of  the  spinal  cord.  But 
this  is  only  a  probability,  and  is  unsupported  by  any  direct  proof. 

However  this  may  be,  it  must  be  remarked  that  the  special  anatomical 
and  physiological  characteristics  of  the  sympathetic  nerves  should  not  cause 
them  to  be  considered  as  a  system  independent  of  the  first,  or  cerebro-spinal 
nerves.  The  fibres  composing  both  have,  in  fact,  a  common  origin  in  the 
medullary  axis,  or  rather  those  of  the  ganglionic  nerves  emanate  from  the 
nerves  of  animal  life.  In  the  considerations  which  follow,  we  will  therefore 
omit  this  distinction  of  the  nerves  into  two  groups. 

Origin  of  the  Nerves. — We  ought  to  distinguish  in  these  cords  their 
real  or  deep  origin,  and  their  superficial  or  apparent  origin.  The  latter  is 
represented  by  the  point  of  emergence  of  the  roots  of  the  nerves,  which  are 
ordinarily  spread  in  a  fan  shape,  then  united,  generally  after  a  very  brief 
course,  into  a  single  trunk,  which  offers  at  its  commencement  a  ganglionic 
enlargement,  if  fibres  of  general  sensibility  enter  into  its  constitution. 
Their  real  origin  is  the  point  of  departure  of  these  roots  in  the  depth  of 
the  cerebro-spinal  axis.  This  is  not  well  known,  perhaps,  of  any  nerve,  even 
of  those  whose  radicles  are  easily  followed  into  the  substance  of  the  nervous 
centres. 

Distribution  of  Nerves. — The  nervous  trunks,  formed  by  the  radicles 
of  which  we  have  just  spoken,  issue  in  pairs  from  the  foramina  at  the  base 
of  the  cranium  or  in  the  walls  of  the  spine,  to  be  distributed  to  all  parts  of 
the  body  by  dividing  into  successively  decreasing  branches.  Those  among 
these  branches  which  ramify  in  the  organs  of  animal  life,  generally  follow 
the  track  of  the  deep  vessels  or  the  subcutaneous  veins,  and  are  always 
found  most  superficial.  Their  ramescence  is  effected  in  a  very  simple 
manner,  by  the  successive  emission  of  the  fasciculi  composing  the  principal 
trunks,  until  they  are  completely  expended.  These  branches  pursue  their 
course  nearly  always  in  a  direct  line ;  only  some,  as  the  ramifications  of  the 
two  principal  •  nerves  of  the  tongue,  describe  very  marked  flexuosities,  with 
the  same  protective  intention  as  the  arteries  of  that  organ.  Anastomoses 
sometimes  join  these  branches  to  one  another ;  and  anastomoses,  often 
enough  complicated,  unite  many  nerves  together,  and  form  what  are  called 
plexuses.     But  in  these  anastomoses,  no  matter  how  comj)licated  they  may 


702 


THE  NERVES. 


be,  there  is  never  any  fusion  of  tlie  nervous  ramuscules,  but  simple  aggrega- 
tion of  tbeir  fibres,  which  always  preserve  their  independence,  characters, 
and  si^ecial  properties.  These  anastomoses,  then,  differ  essentially  from 
those  of  arteries,  and  never  permit  two  trunks  to  mutually  supplement  each 
other  when  the  course  of  one  is  interrupted. 

The  nerves  destined  to  the  organs  of  vegetative  life,  and  which  arise 
from  the  two  subspinal  chains  in  whose  formation  nearly  every  pair  cf 
nerves  concurs,  comport  themselves  in  their  distribution  in  a  slightly 
different  manner.  They  are  enlaced  around  arteries,  forming  on  these 
vessels  very  complicated  plexiform  networks,  and  yet  the  fibres  composing 
them  are  as  absolutely  independent  as  in  the  anastomoses  above  described. 

Termination  of  the  Nerves. — This  jDoint  should  be  examined  separately 
in  the  case  of  the  motor  and  the  sensitive  nerves :  that  is,  in  the  muscles 
and  the  integumentary  membranes.  The  distinction,  however,  is  not  quite  so 
absolute  as  this,  for  the  muscles  always  receive  some  sensitive  tubes  with 
their  motor  filaments. 

In  entering  the  muscles  the  motor  nerves  divide  their  branches,  still 
appearing  as  double-contoured  tubes.  It  was  at  one  time  believed  that  these 
fibres  formed  loops  (Valentin)  in  the  interior  of  the  muscle,  and  returned 
to  their  starting  point.  This  opinion  has  become  obsolete  since  the 
ultimate  termination  of  the  nerves  has  been  studied  by  Eouget,  Krause, 

Fig.  334. 


MUSCULAR   FIBRES,   WITH   TERMINATION  OF   MOTOR   NERVE;   FROM   THE 
GASTROCNEMIUS   OF   THE   RANA   ESCULENTA. 

a,  Terminal  pencil  of  a  dark -bordered  nerve-fibre ;  b,  Intramuscular  naked  axis- 
cylinder;  c.  Nucleus  of  the  neurilemma;  d,  Clarate  extremities  of  the  nerve;  e. 
Spaces  of  the  muscle-nuclei  ;  /,  Terminal  knob  of  nerve,  with  centi'al  fibres  and 
vesicular  dilatations  of  the  nerve 


Kuhne.  KoUiker,  Engelmann,  Conheim  (Beale),  and  others.  What  is  known 
of  this  subject  is  as  follows  : — The  voluminous,  double-contoured  nerve- tubes 
which,  more  or  less,  cross  the  direction  of  the  muscular  fibres,  soon  divide 
and  form  pale  tubes  on  whose  track  are  disseminated  the  nuclei.  These 
tubes  contain  an  axis-cylinder  and  a  medullary  layer.  They  pass  on  to  a 
muscular  fibre  in  the  following  manner :  the  nucleated  sheath  of  the  nerve- 
tube  spreads,  and  is  confounded  Avith  the  sarcolemma  ;  the  medulla  suddenly 
stops,  and  the  axis-cylinder  expands  to  form  a  minute  granular  mass  named 
the  terminal  motor-p^ate.  Is  this  plate  situated  without  or  within  the 
sarcolemma  ?     This  question  is  difierently  answered  by  histologists ;    but, 


THE  CRANIAL  OR  ENCEPHALIC  NERVES.  703 

however  this  may  bo,  tliis  plate,  wliicli  was  discovered  by  Eouget,  at  first  in 
reptiles,  then  iu  birds  aud  mammals,  lias  been  studied  by  several  micro- 
graphs, who  are  agreed  as  to  its  existence.  There  can,  therefore,  be  no 
doubt  that  it  is  the  ultimate  termination  of  the  motor-nerves. 

The  mode  of  termination  of  the  sensitive  nerves  varies  as  they  are 
sensorial  or  general  sensibility  nerves.  It  appears  to  be  demonstrated  that  the 
tubes  of  the  sensorial  nerves  have  at  their  extremity  an  elongated  cell, 
analogous  to  that  from  which  they  started.  An  idea  has  been  given  of 
this  arrangement  in  describing  the  olfactive  portion  of  the  pituitary  mucous 
membrane. 

The  other  sensitive  nerves  have  been  supposed  to  terminate  by  peripheral 
loops,  and  again  by  free  extremities  passing  into  land  of  cell  elements.  It 
is  certain  that  these  two  modes  exist  simultaneously  ;  recurrent  sensibility, 
which  Claude  Bernai'd  demonstrated  in  some  cranial  nerves,  proves 
that  certain  nerves  terminate  by  loops.  Our  own  experiments  have 
shown  :  1 ,  That  this  recurrent  sensibility  is  a  general  phenomenon  belonging 
•to  the  sensitive  nerves  of  the  limbs,  and  even  to  all  the  sensitive  ramifications 
of  the  spinal  nerves ;  2,  That  the  recurrent  anastomotic  loops  are  formed  at 
diflierent  parts  along  the  course  of  the  nerves,  either  beneath  the  integument 
or  in  its  texture.  It  is,  then,  proved  that  the  peripheral  looi)s  constitute  a 
mode  of  termination  of  the  sensitive  nerves.  But  this  is  not  the  only  mode 
of  termination  observed.  In  the  papillae  of  the  skin,  in  certain  regions — 
hand,  foot,  lij)s,  tongue,  glands,  clitoris — the  corpuscles  of  Meissner,  or  tactile 
corpuscles,  are  foimd  ;  these  are  composed  of  condensed  connective  tissue, 
and  are  conical,  like  a  pine-cone,  the  summit  towards  the  periphery.  By  their 
base  enters  one  or  more  nerve-tubes,  that  ascend  toward  the  apex  in 
a  spiral  manner.  In  the  conjunctiva,  lips,  etc.,  are  also  found  rounded  bodies 
analogous  in  their  structure  to  the  tact  corpuscles,  and  which  are  named  the 
corpuscles  of  Krause.  Lastly,  on  the  course  of  the  collateral  nerves  of  the 
fingers  and  in  the  mesentery  of  the  Cat,  are  the  Pacinian  corpuscles :  small 
globular  or  ovoid  bodies  formed  of  several  concentric  layers  of  connective 
tissue,  and  with  a  central  canal  into  which  penetrates  and  terminates,  by  one 
or  more  enlargements,  a  filament  from  the  nerve-trunk  (reduced  to  the  axis- 
cylinder  only).' 


CHAPTEE  I. 

THE  CRANIAL  OR  ENCEPHALIC  NERVES. 

The  cranial  nerves  leave  the  encephalon  in  pairs,  regularly  disposed  to 
the  right  and  left,  and  designated  by  the  numerical  epithets  of  first,  second, 
etc.,  coimting  from  before  backwards. 

Willis,  taking  for  a  basis  the  number  of  cranial  openings  through  which 
the  nerves  passed,  divided  them  into  nine  pairs,  with  which  he  described 
the  first  spinal  pair,  making  it  the  tenth  in  the  series  of  encephalic  nerves. 
This  division  being  faulty  in  some  respects,  it  was  sought  to  perfect  it. 
Haller  commenced  by  removing  the  first  sj^inal  or  suboccipital  pair  of 
nerves  to  their  proper  region  ;  then  followed  Soemmering  and  Vicq-d'Azyr, 

'  Arloing  and  Tripier.  'Reclierches  sur  la  iSensibihte  cles  Teguments  et  des  Nerfa 
de  la  Main.'    (Archives  de  Pbysiologie,  1869.) 


704  THE  nerves: 

who  doubled  the  seventh  pair  of  Willis,  and  reduced  his  eighth  into  three 
distinct  pairs,  according  to  considerations  derived  from  the  destination  and 
uses  of  these  nerves.  The  number  of  pairs  of  cranial  nerves,  their  order  of 
succession,  and  their  nomenclature  was  then  established  in  the  following 
manner  : 

1st   pair  or  olfactory  nerves       .      .      .  corre.sponding  to  the     1st  pair  of  Willis. 

2nd  pair  or  optic  nerves 2ud  pair  — 

3rd  pair  or  common  motores  oculorum  nerves       .  .      .     3rd  pair  — 

4th  i^air  or  pathetici  nerves 4th  pair  — 

5th  pair  or  trigeminal  nerves 5th  pair  — 

6th  pair  or  abducentes  nerves 6th  pair  — 

7th  pair  or  facial  nerves "1  _  ,        .  

8th  pair  or  auditory  nerves j-/iupair 

9th  pair  or  glosso-pharyugeal  nerves j 

10th  pair  or  pneumogastric  nerves         \  8th  pair  — 

11th  pair  or  accessory  or  spinal  nervts ) 

12th  pair  or  great  hypo-glossal  nerves 9th  pair  — 

In   the   following   table,  these  nerves  are  classed   according   to   their 
properties ; 

1.  Nerves  of  spe-     (  1^!!."„*?5_  °''^'' °''     i'A  P^^'' 


optic  nerves 2nd 

auditory  nerves 8th 

2.  Mixed  nerves       j  trigeminal  nerves 5th 

with  double         <  glosso-pharyngeal  nerves 9tli 

roots     .        .        I  pneumogastric  nerves 10th 

(  common  motores  oculorum  nerves       .      .      .  3rd 

pathetici  nerves 4th 

abducentes  nerves 6th 


cial  sense 


3.  Motor  nerves 


with  single        <   f^^^  serves .'     .      7th 

^'^'-'''^     •        •       '   accessory  or  spinal  nerves 11th     — 

great  hypo-glossal  nerves l.th     — 

(Sir  Charles  Bell  considered  the  fourth,  seventh,  and  eighth  nerves  as 
forming  a  separate  system,  and  to  be  allied  in  the  functions  of  exj^ression 
and  respiration.  In  consonance  with  this  view,  he  termed  them  respiratory 
nerves,  and  named  that  portion  of  the  medulla  oblongata  from  which  they 
arise  the  resphatory  tract.) 

One  of  the  characteristics  of  the  cranial  nerves  being  their  diversity,  it 
is  scarcely  possible  to  study  them  as  a  whole,  and  it  is  only  in  their  origin 
that  they  resemble  each  other  in  some  points.  We  therefore  confine 
ourselves  to  those  general  considerations  which  alone  touch  this  part  of 
their  description. 

Do  the  cranial  nerves  proceed  from  the  three  principal  apparatus  com- 
posing the  encephalon,  or  are  they  furnished  by  two,  or  even  one  of  these  ? 
This  is  the  question  that  should  first  be  discussed.  If  it  is  evident  to 
everyone  that  the  isthmus  gives  rise  to  the  majority  of  the  encephalic 
nerves,  and  that  the  cerebellum  has  nothing  whatever  to  do  with  their 
emission,  it  is  not  agreed  among  anatomists  as  to  the  part  the  brain-proper 
takes  in  this  emission.  Two  pairs  of  cranial  nerves  are  indeed  considered 
by  several  authors  as  emanating  from  the  latter  organ,  while  others  regard 
them  as  derived  from  the  isthmus.  According  to  the  first,  only  ten  en- 
cephalic pairs  of  nerves  belong  to  this  prolongation  of  the  spinal  cord,  the 
other  two — the  olfactory  and  optic  nerves — proceed  from  the  brain;  while 
the  second  aver  that  all  the  cranial  nerves  without  exception  arise  from  the 
medulla  oblongata.     Let  us  endeavour  to  discover  the  truth. 

It  is  certain  that  this  difference  of  opinion  on  a  point  apparently  easy  of 


THE  CRANIAL  OB  ENCEPHALIC  NERVES.  705 

solution,  has  its  source  iu  a  misunderstanding,  and  is  really  not  founded  on 
facts,  whic'li  are  the  same  for  everyone,  their  appreciation  only  varying. 
Nothing  is  more  easy  to  prove.  Look,  in  the  first  instance,  at  the  optic 
nerve.  This,  according  to  some,  proceeds  from  the  corpora  quadrigemina 
and  thalami  optici ;  it  therefore  arises  from  the  brain.  No  doubt,  if  these 
two  parts  of  the  encephalon  be  considered  as  a  portion  of  the  hemispheres  ; 
but  this  is  far  from  proved,  and  in  an  anatomical  and  jihysiological  point 
of  view  it  is  not  so.  As  the  corpora  quadrigemina  and  tlialami  optici  form 
part  of  the  isthmus,  it  is  natural  to  look  upon  it  as  the  source  from  which 
the  second  pair  of  nerves  arise.  With  regard  to  the  first  pair,  their  fibres 
are  also  connected  with  those  of  the  isthmus,  across  the  corjDus  striatum,  as 
will  be  proved  hereafter.  But  vi'e  are  far  from  denying  their  connections 
■with  the  hemispheres  (see  the  description  of  the  first  pair),  and  which  are 
very  intimate ;  though  this  proves  nothing  against  our  opinion.  Therefore 
it  is,  that,  in  recognising  in  the  disposition  of  the  roots  of  the  olfactory 
nerve  conditions  altogether  special,  we  admit  that  the  isthmus  of  the 
encephalon  is  the  common  point  of  departure  for  all  the  cranial  nerves — an 
important  and  capital  fact,  and  which  constitutes,  for  the  great  category  of 
encephalic  nerves,  a  true  family  character. 

Among  the  other  points  relative  to  the  origin  of  these  pairs  of  nerves, 
are  the  following :  All  the  encephalic  nerves  appear  to  be  connected  at 
their  origin  with  the  fasciculi  of  the  isthmus,  Avhose  properties  they  share. 
All  are  equally  connected  with  a  centre  of  grey  substance  placed  in  the 
texture  of  the  isthmus,  and  named  by  Stilling  the  nucleus  of  the  nerves. 
The  majority  originate  by  converging  filaments,  the  anterior  of  which  come 
from  the  brain,  and  the  posterior  from  the  side  of  the  spinal  cord. 

Preparation  of  the  cranial  nerves. — Four  preparations  are  necessary  to  study  the 
cranial  nerves : 

1.  An  encephalon  extracted  after  opening  the  craninm  by  its  h\\?e.  and  hardened 
by  prolonged  immersion  in  alcohol  or  very  diluted  acetic  acid.  TJiis  piece  permits  the 
origin  of  tlje  nerves  to  be  studied  (Fig.  322). 

2.  The  superiioial  nerves  of  the  head;  these  are  the  auricular  nerves,  and  the 
divisions  of  the  subzygomatic  plexus,  with  the  suborbital  and  mental  Ijranches,  as  well 
OS  the  superficial  ramusculcs  of  the  three  nerves  of  the  ophthalmic  branch  of  ti^e  fifth 
pair  (Fig.  110). 

.3.  A  piece  disposed  as  in  fi\i\\re  336,  for  the  study  of  the  maxillary  nerves.  To  prepare 
it,  the  greater  part  of  the  masbcter  muscle  .should  be  removed  in  di,«secting  the  masseteric 
nerve;  the  globe  of  the  eye  must  be  extirpated,  the  orbital  and  zygomatic  proces.-es 
excised,  the  two  maxillary  sinuses  opened,  and  the  branch  of  the  inferior  maxillary  bone 
chisellel  off  as  in  the  figure.  Lastly,  the  anastomosis  of  the  lacial  with  the  sub- 
zygomatic nerve  is  dissected  by  cutting  away  the  parotid  gland. 

4.  I'he  deep  nerves,  including  those  of  the  globe  of  the  eye  ;  this  preparation  sliould 
be  made  by  following  exactly  the  instructions  given  for  dissecting  the  arteries  of  the 
head.     Figure  335  will  serve  as  a  guide  for  detaiL. 

Tlie  pneumogastric  and  spinal  nerves,  which  are  not  included  in  these  consideration.*, 
should  be  prepared  and  studied  at  tlie  same  time  as  the  great  sympatlieti>.',  When 
treating  of  the  latter,  we  will  refer  to  them. 

1.  First  Pair,  or  Olfactory  Nerves.    (Figs.  327,  329.) 

The  first  cranial  pair  is  constituted  by  the  olfactory  lobes,  whose 
anterior  extremities  give  off  a  great  number  of  nervous  filaments,  which  pass 
through  the  cribriform  foramina  to  ramify  in  that  part  of  the  pituitary 
membrane  lining  the  bottom  of  the  nasal  fossce. 

Each  olfactory  lobe  is  connected  with  the  encephalon  by  two  roots,  an 
external  and  an  internal,  both   composed  of  white  substance  (Fig.  322), 


706  THE  NEEVES. 

The  external  commences  by  a  grey-coloured  convolution  wliicli  borders, 
externally,  the  mastoid  lobule  or  inferior  lobe  of  the  hemisphere.  The 
internal,  followed  from  before  backwards,  turns  round  in  the  interlobular 
fissure,  in  front  of  the  chiasma  of  the  optic  nerves,  to  mix  with  the  cere- 
bral convolutions.  These  two  roots  circumscribe  a  triangular  space  oc- 
cupied by  the  extra-ventricular  nucleus  of  the  corpus  striatum,  which  they 
embrace.  In  brains  which  have  been  macerated  for  a  long  time  in  alcohol, 
it  is  easy  to  see  that  the  fibres  of  these  roots  are  continuous,  in  great  part, 
with  those  of  the  corpus  striatum,  and  commence  with  the  fasciculi  of  the 
isthmus,  which  radiate  and  spread  across  the  grey  matter  of  that  body. 

After  the  union  of  its  two  roots,  the  olfactory  lobe  is  constituted  by  a 
wide  white  band  that  passes  forward  on  the  inferior  face  of  the  hemisphere, 
and  soon  terminates  in  a  very  elongated  oval  dihatation  lodged  in  the 
ethmoidal  fossa.  This  bulb  is  formed  by  grey  substance  on  its  inferior 
face  and  white  substance  on  the  superior.  It  is  said  to  be  a  flattened 
ganglion  applied  to  a  band  of  white  substance,  which  at  first  represents  in 
itself  the  olfactory  lobe. 

We  have  already  seen  that  this  lobe  is  hollow  internally,  and  that  it 
communicates  with  the  lateral  ventricles  of  the  brain.  This  peculiarity, 
added  to  the  special  features  of  its  external  physiognomy,  might,  it  appears 
to  us,  give  rise  to  doubts  as  to  the  real  nature  of  the  lobes  in  question. 
It  is  evident  that  these  are  not  nerves,  but  rather  dependencies  of  the  en- 
cephalon ;  and  it  is  only  conformable  to  custom  that  we  describe  them  here 
as  the  first  pair  of  encephalic  nerves. 

The  real  olfactory  nerves  are  the  filaments  which  arise  from  the  inferior 
face  of  the  ethmoidal  bulb  or  ganglion,  and  which  traverse  the  cribriform 
lamella  to  gain  the  mucous  membrane  of  the  nose.  Their  number  cor- 
responds with  the  ethmoidal  foramina.  At  first  very  soft,  delicate,  and 
easily  torn,  they  are  enveloped  on  their  passage  through  these  apertures 
by  a  very  strong  neurilemma,  which  gives  them  great  solidity.  Some,  in 
ramifying,  descend  on  the  septum  nasi ;  others — and  these  are  the  most 
numerous — ^divide  on  the  ethmoidal  cells,  where  they  form  fine  and  more  or 
less  plexuous  pencils,  mixed  up  with  the  no  less  interesting  divisions  of  the 
ethmoidal  branch  of  the  ojjhthalmic  artery.  Their  terminal  extremities 
do  not  descend  below  the  ujjper  third  of  the  nasal  fossje,  but  remain  con- 
fined to  the  bottom  of  these  cavities. 

These  are  the  special  nerves  of  smell.  They  receive  the  impression  of 
odours  and  transmit  them  to  the  encephalon  ;  and  this  function,  which  has 
been  accorded  and  refused  them  time  after  time,  has  only  been  decided 
within  the  last  thirty  years. 

2.  Second  Pair,  or  Optic  Nerves.     (Fig.  329.) 

The  nerves  of  vision  present  for  consideration  in  their  interesting  study, 
their  or'ujin,  course,  termination,  and  properties. 

There  has  been  much  dispute,  and  there  will  probably  be  much  more, 
with  regard  to  the  _  origin  of  the  second  pair.  But  without  confining  our- 
selves to  an  appreciation  of  the  opinions  which  have  pervaded  science  on  this 
matter,  we  will  describe  what  we  have  observed  in  the  domesticated  animals. 

When  the  encephalic  isthmus  is  isolated  from  the  brain  (Fig.  324,  12) 
and  examined  laterally,  we  recognise  on  its  anterior  limit  the  white  band 
that  constitutes  the  optic  nerve.  Studied  at  its  origin,  this  band  is  con- 
tinued, in  the  most  evident  manner,  with  the  external  side  of  the  thalamus 


THE  CHAXIAL  OB  ENCEPHALIC  NERVES.  707 

opticus,  wlicrc  it  forms  the  two  enlargements  known  as  the  corpora  gcniculata. 
This  thalamus  ought,  therefore,  to  be  regarded  as  the  point  of  departure  of 
the  nerve  that  bears  its  name.  But  as  the  external  corpus  geniculatum  is 
in  contact  with  the  natis,  and  as  the  internal  is  united  to  the  testis  by  a 
band  of  white  fibres,  it  is  almost  certain,  according  to  several  authorities,  that 
the  corpora  quadrigemina  concur  in  furnishing  the  constituent  fibres  of 
the  optic  nerves. 

At  first  wide  and  thin,  the  optic  band  (trachis  optims)  is  rolled  round 
the  cerebral  peduncle  from  above  to  below  and  behind  to  before,  and 
gradually  narrows.  Arrived  at  the  inferior  surface  of  the  encephalon,  it 
is  changed  into  a  funicular  cord,  which  unites  with  that  of  the  opposite 
side  to  form  the  commissure  or  chiasma  of  the  optic  nerves  ;  this  is  only  a 
temporary  fusion,  as  beyond  it  the  two  nerves  reappear,  and  pass  into  the 
optic  foramen,  to  reach  the  interior  of  the  ocular  sheath  and  the  bottom 
of  the  globe  of  the  eye. 

We  will  enter  into  some  details  on  the  relations  of  the  optic  nerves 
in  the  different  points  of  the  course  .ve  have  indicated. 

In  their  flat  portion,  or  origin,  they  are  comprised  between  the  cerebral 
peduncles  and  the  hemispheres.  From  the  point  where  they  become  free, 
at  the  inferior  face  of  the  encephalon,  to  the  chiasma,  they  are  covered  by 
tlie  pia  mater,  and  adhere  by  their  deep  face  to  the  superior  extremity  of 
the  peduncles. 

The  chiasma  is  lodged  in  the  optic  fossa,  and  receives  on  its  deep  face 
the  insertion  of  the  small  grey  lamina  which  bounds  the  third  ventricle  in 
front ;  for  which  reason  this  is  generally  described  as  the  grey  root  of  the 
optic  nerves.  But  of  all  the  proper  connections  of  the  chiasma,  the  most 
important  are  certainly  those  which  each  nerve  maintains  with  its  congener 
at  their  junction.  What  becomes  of  the  fibres  of  each  nerve  in  this  anas- 
tomosis ?  Do  they  cross  one  another  to  reach  the  opposite  eye ;  or  do  they 
merely  lie  together,  and  afterwards  separate,  in  order  to  go  to  the  eye  on 
their  own  side  ?  Anatomy  demonstrates  that  the  fibres  of  the  chiasma  do 
not  exclusively  affect  either  of  these  arrangements ;  for  in  studying  them 
in  a  specimen  that  has  been  macerated  for  some  days,  it  is  found  that  the 
majority  cross  each  other  in  a  very  evident  manner,  but  that  a  part  regain 
the  nerve  corresponding  to  the  side  from  which  they  came.  It  is  there- 
fore seen  that  the  nerves  of  the  second  pair  are  composed  of  one  kind  of 
fibres  on  this  side  of  the  chiasma,  while  beyond  it  they  show  two  sorts — 
the  fibres  from  the  right  and  left  sides.  The  majority,  we  have  said,  cross 
each  other ;  and  the  proof  of  this  is  afforded  in  certain  facts  observed  in 
pathological  anatomy,  which  are  of  sufficient  intez-est  to  be  mentioned 
here.  In  the  cases  so  frequently  occurring  i'n  the  Horse,  where  an  eye  is 
lost  from  the  ravages  of  specific  ophthalmia  (fluxion  periodique),  the 
consecutive  atrophy  of  the  optic  nerve  nearly  always  stops  at  the  chiasma. 
though  it  sometimes  happens  that  it  gets  beyond  this ;  and  it  is  observed 
that  it  is  usually  the  nerve  opposite  to  the  diseased  eye  which  suflers  the 
most.  Otherwise,  the  arrangement  just  described  is  only  a  degree  less 
advanced  than  that  remarked  in  certain  species — in  the  osseous  fishes  for 
instance — in  which  the  optic  nerves  entirely  cross  each  other  without  con- 
founding or  mixing  their  fibres. 

Beyond  their  commissure,  the  nerves  of  the  second  pair  are  in  relation 
with  the  walls  of  the  optic  foramina,  then  with  the  posterior  rectus  muscle 
(retractor  oculi),  which  envelops  each  nerve  as  in  a  sheath.  In  the  orbits 
they  are  also  related  to  some  other  nerves  and  vessels. 


708 


THE  NERVES. 


Witli  regard  to  its  ermination,  tlie  optic  nerve  enters  tlie  globe  of  the 
eye  by  piercing  tbe  sclerotic  and  choroid  coats,  towards  the  most  de- 
clivitous part  of  its  posterior  surface,  and  in  the  form  of  a  membrane  which 
is  described  in  the  apparatus  of  vision  as  the  retina.  Before  traversing  the 
bottom  of  the  eye,  this  nerve  always  becomes  markedly  constricted. 

The  study  of  the  structure  of  the  optic  nerve  reveals  some  peculiar 
facts  wdaich  it  is  well  to  know,  though  they  are  more  curious  than  in- 
teresting. The  upper  part  is  entirely  destitute  of  envelope,  while  the 
inferior — that  in  front  of  the  chiasma — has  a  double  neurilemma.  The 
external  layer  of  this  is  only  a  dependency  of  the  dura  mater :  a  kind  of 
fibrous  sheath  attached  at  one  end  to  the  margin  of  the  optic  foramen,  and 
at  the  other  to  the  sclerotica.  The  internal,  which  is  analogous  to  the 
neurilemma  of  the  other  nerves,  emanates  from  the  pia  mater,  and  presents 
a  multitude  of  septa  (forming  the  lamina  cribrosa),  which  keep  the  fibres  of 
this  nerve  apart  from  each  other.  To  make  this  organisation  manifest,  the 
latter  should  be  steeped  in  an  alkaline  solution  for  some  days,  and  then  washed 
in  a  stream  of  water  to  remove  the  softened  nervous  matter ;  the  nerve  is 
to  be  afterwards  tied  at  one  ot  its  extremities,  inflated,  tied  at  the  ojiposite  end, 
and  dried.     By  means  of  some  sections  all  the  canals  that  lodge  the  fasciculi 

of  nervous  tubules,  and  which 
'^"       *  are    formed    by    the     internal 

neurilemma,  are  then  shown. 

Concerning  the  properties  of 
the  optic  nerve,  we  will  say 
nothing ;  though  they  are  analo- 
gous to  those  of  the  other  nerves 
of  special  sense ;  it  is  destined 
to  transmit  to  the  encephalon 
the  impressions  furnished  by 
the  sense  of  sight,  and  mechani- 
cal irritation  of  it  does  not  cause 
pain. 


3.  Third  Pair,  or  Common  Oculo- 
motor Nerves.    (Figs.  326,  335.) 

The  nerves  of  the  third  pair 
emanate  from  the  cerebral  pe- 
duncles, near  the  interpedun- 
cular fissure,  and  at  an  almost 
equal  distance  between  the 
corpus  albicans  and  the  pons 
Varolii.  Their  roots,  seven  or 
eight  in  each,  penetrate  the 
texture  of  these  peduncles,  pass 
backwards,  and  may  be  traced 
to  their  nucleus,  which  Stilliug 
has  placed  above  the  anterior 
border  of  the  pons  Varolii,  and 
which  is  united  to  that  of  the 
median  line. 

flattened  trunk,  which  is  at  first 
inflected  forward  to  enter,  along 


NERVES   OP  THE   ETE. 

1,  Ophthalmic  branch  of  the  fifth  pair;  2,  Palpebro- 
nasal branch  ;  3,  Lachrymal  nerve  ;  3',  Temporal 
branch  of  that  nerve ,  4,  Frontal  nerve ,  5,  Ex- 
ternal oculo-motor  nerve,  6,  Trochlear  nerve, 
8,  y,  10,  11,  Branches  of  the  common  oculo-moter 
nerve ;  12,  Superior  maxillary  nerve ;  13,  Its 
orbital  branches. 

opposite  side  by  fibres  intercrossing  on  the 

From  the  union  of  these  roots  results  a 

cai-ried  outward,  and  is  almost  immediately 


THE  CRAXIAL  OR  EXCEPHALIC  NERVES. 


709 


\vitli  the  sixth  pair  and  the  oplithahuic  branch  of  the  trigeminal  nerve,  into  the 
smallest  of  the  great  snprasphenoidal  foramina.  The  common  oculo-motor 
nerve  afterwards  arrives,  by  the  orbital  hiatus,  at  the  bottom  of  the  ocular 
sheath,  where  it  separates  into  several  branches  destined  to  the  following 
muscles  of  the  eye  :  the  elevator  of  the  upper  eyelid,  superior  rectus, 
internal  rectus,  inferior  rectus,  posterior  rectus — except  its  internal  fasciculus 
— and  the  small  oblique.  The  branch  to  the  latter  is  remarkable  for  its  great 
length  ;  it  reaches  its  destination  in  passing  to  the  outside  of^  and  then  below 
the  inferior  rectus.  The  motor  roots  of  the  ojihthalmic  ganglion  furnished 
by  til  is  nerve,  are  given  off  from  the  same  point  as  the  branch  for  the  small 
oblique  muscle. 

The  nerves  of  the  third  pair  are  purely  motor,  as  is  shown  by  their 
connections  with  the  inferior  plane  of  the  cerebral  peduncles,  and  their 
exclusive  distribution  to  contractile  organs.  They  incite  all  the  muscles 
lodged  in  the  ocular  sheath,  except  the  external  rectus,  the  great  oblique, 
and  posterior  rectus. 

(It  also  sends  a  motor  filament  to  the  lenticular  ganglion,  supplies  the 
circular  muscular  fibres  of  the  iris  and  ciliary  muscle,  and  presides  over 
contraction  of  the  pupil.) 

4.  Fourth  Pair,  or  Pafhetici.     (Pig.  335,  6.) 

The  pathetic  or  internal  rculo-motor  (or  trochlearisj  nerve  is  the  smallest 
of  all  the  cranial  nerves.  Its  description  is  extremely  simple.  It  arises 
from  the  band  of  Reil,  immediately  behind  the  corpora  quadrigemina,  by 
two  short  roots,  which  it  has  been  impossible  for  me  to  follow  very  deeply 
in  the  substance  of  the  isthmus. 

It  is  directed  outwards,  downwards,  and  forwards,  to  disengage  itself 
from  the  deep  position  it  at  first  occupies,  and  lies  beside  the  superior 
branch  of  the  trigemini,  accompanying  it  to  the  suprasjihenoidal  foramina, 
the  smallest  of  which  it  enters.  This  opening  is  exclusively  intended  for 
it,  and  carries  it  to  the  bottom  of  the  ocular  sheath,  when  it  gains  the  deep 
face  of  the  great  oblique  muscle,  in  wliich  it  ramifies,  supplying  that  organ 
with  the  stimulant  pi'inciiile  of  muscular  contractility. 

The  physiological  study  of  this  nerve  gives  rise  to  some  very  interesting 
remarks,  whicli  we  will  sum  up  here  in  a  few  words.  The  two  oblique 
muscles  of  the  eye  pivot  the  ocular  globe  in  the  orbit,  without  causing  the 
slightest  deviation  either  upwards,  downwards,  or  otherwise,  of  the  pupillary 
opening.  But  this  rotatory  movement  is  altogether  involuntary,  and  is  only 
accomplished  in  certain  determinate  conditions.  "  Gueriu,  Szokalski, 
Hueck,  and  Helie  have  remarked,  that  when  the  head  is  alternately  inclined 
to  the  right  or  left,  while  the  vision  is  fixed  on  any  object,  the  ocidar  globes 
describe  around  their  antero-posterior  axis  an  inverse  rotatory  movement 
that  has  the  effect  of  preserving  a  constant  relationship  betw^een  the  object 
from  which  the  luminous  rays  proceed  and  the  two  retinae.  In  this 
rotatory  motion  the  great  oblique  muscle  of  one  side  has  for  its  congener 
the  small  oblique  of  the  other  side :  thus,  when  the  head  is  inclined  on  the 
right  shoulder,  the  right  eye  revolves  inwards  and  downwards  on  its  axis, 
under  the  influence  of  the  superior  oblique  muscle,  while  the  left  eye  turns 
on  itself  outwards  and  downwards,  through  the  action  of  the  inferior 
oblique ;  when  the  head  is  inclined  on  the  left  shoulder,  an  inverse  move- 
ment takes  place  in  the  two  eyes.  This  simultaneous  rotation  of  the  ocular 
globes  around  their  antero-posterior  diameter,  when  the  head  is  inclined  to 

48 


710  THE  NERVES. 

one  side  or  the  other,  is  necessary  for  the  unity  of  perception  of  visual 
objects ;  if  one  of  the  two  eyes  remained  fixed  while  the  other  turned  on  its 
axis,  we  would  perceive  two  images,  a  superior  corresponding  to  the  healthy 
eye,  and  an  inferior  to  the  diseased  one.  These  two  images  are  visible 
when  the  head  is  vertical,  and  particularly  when  it  is  inclined  to  the  affected 
side ,  they  are  confounded  into  a  single  one  when  the  head  is  carried  to 
the  healthy  side."  ■• 

The  involuntary  action  of  the  ohlique  muscles  of  the  eye  in  this  rotatory 
movement  strongly  attracts  atttention  to  the  nerves  which  these  muscles 
receive,  and  stimulates  a  desire  to  learn  the  particular  conditions  which 
permit  them  to  act  as  excito-motors  independently  of  the  will ;  although  they 
as  well  as  the  muscles  to  which  they  are  destined,  belong  to  those  of  animal 
life.  In  the  present  state  of  science,  nothing  positive  can  be  affirmed  on  so 
delicate  a  subject.  There  are,  nevertheless,  two  interesting  remarks  to 
make  the  pathetic  nerve  is  exclusively  destined  to  the  superior  oblique 
muscle,  and  the  long  branch  sent  by  the  common  oculo-motor  nerve  to  the 
inferior  oblique  does  not  give  any  filament  to  the  neighbouring  parts.  This 
branch  is,  therefore,  also  the  exclusive  nerve  of  the  inferior  oblique,  and  may 
bo  considered  as  a  second  pathetic. 

rSir  Charles  Bell  designated  the  fourth  nerve  the  "  respiratory  nerve  of 
the  eye,"  and  asserted  that  it  was  large  in  all  animals  callable  of  much 
expression.") 

5.  Fifth  Pair,  or  Trigemimi.     (Figs.  110,  322,  335,  336,  337,  338,  342.) 

The  nerve  we  are  about  to  describe  has  also  been  named  by  Chaussier 
the  trifacial  nerve.  It  is  distinguished  among  all  the  cranial  nerves  by  its 
enormous  volume,  the  multiplicity  of  its  branches,  the  variety  of  its  uses, 
and  its  connections  with  the  great  sympathetic  system.  It  therefore 
require  8  to  be  described  as  completely  as  possible  ;  and  in  this  description 
we  will  include  the  study  of  the  cephalic  ganglia  of  the  great  sympathetic 
system,  which  ought  to  be  regarded  as  annexes  of  the  fifth  pair. 

Origin. — The  trigeminus  belongs  to  the  category  of  mixed  nerves,  as  it 
possesses  two  roots — one  sensitive,  the  other  motor. 

Sensitive  Boot  (Figs.  337,  338,  i). — This  is  the  largest  root.  It  emanates 
from  the  outside  of  the  p(ms  Varolii,  near  the  middle  cerebellar  peduncle, 
and  is  directed  forward  and  downward  to  gain  the  anterior  portion  of  the 
foramen  lacerum,  where  it  terminates  in  a  very  great  semilunar  enlargement 
constituting  the  Gasserian  gawjlion.  Flattened  from  above  to  below,  and 
wider  in  front  than  behind,  this  root  on  the  outer  side  is  about  6-lOths  of 
an  inch  in  length,  but  the  inner  side  is  double  that  measurement  because  of 
the  oblique  position  of  the  ganglion  which  continues  it. 

If  it  be  traced  into  the  substance  of  the  pons,  it  will  be  found  that  the 
fibres  of  the  latter  separate  for  its  passage  from  the  deep  plane  it  at  first 
occupies.  The  following  is  the  manner  in  which  it  comports  itself  in  this 
plane  : — This  root  is  separated  into  two  orders  of  fibres,  posterior  and 
anterior.  The  first  pass  beneath  the  arciform  fasciculi  of  the  pons  Varolii, 
to  be  contini;ed  with  the  restiform  body,  and  consequently  with  the  pos- 
terior columns  of  the  spinal  cord  ;  the  second  separate  from  each  other,  and 
scon  become  confounded  with  the  cells  amassed  in  the  interior  of  the 
isthmus,  at  the  anterior  cerebellar  peduncles,  and  above  the  intermediate 
1  fasciculus  of  the  medulla  oblongata.    The  fibres  of  the  trigeminus,  or  the  cells 

'  SapiKy.    '  A natomie  Descriptive.' 


TEE  CRANIAL  OR  ENCEPHALIC  NERVES.  711 

wliicli  receive  these  fibres,  are  in  corimunication  with  several  cranial  nerves, 
particularly  the  pneumogastric,  glosso-pharyngeal,  facial,  and  auditory. 

Semilunar  or  Gasserian  gamjUon. — This  ganglion,  which  receives  the 
sensitive  root  of  the  trigeminus,  is  crescent  shaped,  its  concavity  being 
turned  backwards  and  inwards.  It  may  be  said  to  be  imbedded  in  the 
fibro-cartilaginous  substance  which  in  part  closes  the  occipito-spheno- 
temporal  hiatus,  and  divides  it  into  several  particular  foramina.  Its 
superior  face  is  covered  by  the  dura  mater,  and  sends  a  number  of  filaments 
to  that  membrane. 

The  Gasserian  ganglion  is  not  continued  by  a  single  trunk,  but  imme- 
diately gives  rise  to  two  thick  branches,  one  of  which  leaves  the  cranium 
by  the  foramen  ovale — an  opening  formed  by  the  above-named  hiatus; 
while  the  otber  is  lodged  in  the  external  fissure  in  the  intercranial  face  of 
the  sphenoid  bone,  and  passing  along  it  as  far  as  the  entrance  to  the  supra- 
sphenoidal  foramina,  bifurcates. 

Hence  it  results  that  the  trigeminus  is  divided,  even  at  its  origin,  into 
three  branches :  two  superior — the  ophthalmic  branch  of  Willis,  and  the 
superior  maxillary  nerve,  commencing  by  the  same  trunk ;  and  an  inferior, 
which  constitutes  the  inferior  maxillary  nerve. 

Motor  or  small  root  (Figs.  337,  338). — This  is  a  flattened  band  which 
emerges  from  the  pons  Varolii,  at  the  inner  side  of  the  principal  root.  Its 
fibres  may  be  easily  followed  to  the  interior  of  the  pons  Varolii,  and  in  their 
dii'ection  they  comport  themselves  like  those  of  the  large  root,  by  becoming 
confounded  with  the  substance  of  the  anterolateral  fasciculus  of  the 
medulla  oblongata.  Leaving  the  pons,  this  root  passes  forwards  on  the 
inferior  face  of  the  Gasserian  ganglion,  which  it  crosses  in  a  diagonal 
manner  outwards,  and  beyond  which  it  intimately  unites  with  the  fibres 
of  the  inferior  maxillary  nerve.  The  superior  maxillary  nerve  and  the 
ophthalmic  branch  do  not  I'eceive  any  fibres  from  it.  In  the  fifth  pair,  then, 
it  is  only  the  inferior  maxillary  nerves  which  are  at  the  same  time  sensitive 
and  motor,  and  are  real  mixed  nerves. 

A.  Ophthalmic  Branch  (Fig.  335,  1). — This  is  the  smallest  of  the 
three  divisions  furnished  by  the  Gasserian  ganglion,  and  proceeds  by  a 
trunk  common  to  it  and  the  maxillary  nerve,  which  will  be  described  here- 
after. This  branch  enters  the  smallest  of  the  large  suprasphenoidal 
foramina,  along  with  the  common  and  external  oculo-motor  nerves,  and 
in  the  interior  of  this  bony  canal  divides  into  three  ramuscules,  which  reach 
the  bottom  of  the  ocular  sheath  by  the  orbital  hiatus. 

These  ramuscules  are : 

1.  The  frontal  or  supra-orbital  (supratrochlear)  nerve. 

2.  The  lachrymal  nerve. 

3.  The  nasal  or  palpebro-nasal  nerve. 

1.  Fkontal  Nerve  (Fig.  335,  4). — This  is  a  fiat,  voluminous  branch 
placed  on  the  inner  wall  of  the  ocular  sheath,  and  proceeding  nearly  parallel 
with  the  great  oblique  muscle  of  the  eye  to  the  supra-orbital  foramen,  into 
which  it  passes  along  with  the  artery  of  the  same  name.  Undivided  before 
its  entrance  into  this  orifice,  immediately  after  its  exit  from  it,  it  separates 
into  several  ramuscules,  which  meet  the  anterior  auricular  nerve,  and  are 
expended  in  the  skin  of  the  forehead  and  upper  eyelid. 

2.  Lachrymal  Nerve  (Fig.  335,  3). — This  is  composed  of  several 
filaments,  which  ascend  between  the  ocular  sheath  and  the  elevator  muscles 
of  the  eyelid  and  superior  rectus,  to  enter  the  lachrymal  gland.     One  of 


712  THE  NERVES. 

tliese  (Fig.  335,  3')  traverses  the  ocular  slieatli  behind  the  orbital  process, 
and  places  itself,  from  before  to  behind,  on  the  external  surface  of  the  zygo- 
matic process,  where  it  divides  into  a  number  of  ramuscules,  some  of  which 
mix  with  those  of  the  anterior  auricular  nerve  to  form  the  plexus  of  that 
name,  while  the  others  pass  directly  into  the  anterior  muscles  and  integu- 
ments of  the  ear. 

Palpebro-nasal  Nerve  (Fig.  335,  2). — This  describes  a  curve,  like 
the  ophthahnic  artery,  and  passes  with  that  vessel  into  the  cranium  by  the 
orbital  foramen.  After  coursing  through  the  ethmoidal  fissure  that  lodges 
the  artery,  it  traverses  the  cribriform  plate,  and  divides  into  two  filaments — an 
internal  and  external,  which  ramify  in  the  pituitary  membrane  on  both  sides 
of  the  nasal  fossa.  Before  entering  the  orbital  foramen,  this  nerve  gives 
oif  a  long  branch  {infratrochlear)  that  glides  over  the  floor  of  the  orbit  to 
reach  the  nasal  angle  of  the  eye,  where  it  is  distributed  to  the  lachrymal 
apparatus  lodged  there,  as  well  as  to  the  lower  eyelid ;  it  also  detaches  a 
long  filament  to  the  membrana  nictitans  and  the  sensitive  roots  of  the 
ophthalmic  ganglion,  which  will  be  noticed  hereafter. 

B.  SuPERiou  Maxillary  Nerve  (Fig.  336,  15). — This?  nerve  is  the 
real  continuation  of  the  superior  trunk  given  off  by  the  Gasserian  ganglion, 
where  we  will  begin  to  follow  it  to  its  termination,  examining  briefly 
the  ophthalmic  branch  already  described  as  a  collateral  division  of  this 
trunk. 

Remarkable  for  its  volume,  and  its  prismatic  and  funicular  shape,  the 
superior  maxillary  nerve  proceeds  from  the  inner  and  upper  section  of  the 
semilunar  ganglion,  and  at  first  occupies  the  fissure  on  the  internal  face 
of  the  sphenoid  bone,  without  the  cavernous  sinus,  and  is  covered  at  this 
point  by  the  dura  mater.  After  sending  the  ophthalmic  branch  into  the 
smallest  of  the  great  suprasphenoidal  conduits — the  great  sphenoidal  fissure, 
it  enters  the  most  spacious  of  these  oj^euings — the /oramen  rofMndmn,  arrives 
in  the  orbital  hiatus  beneath  the  sheath  of  the  eye,  and,  with  the  internal 
maxillary  artery,  passes  along  the  space  filled  with  fixt  which  separates  that 
hiatus  from  the  origin  of  the  supramaxillo-dental  (infra-orbital)  canal, 
which  it  follows  to  its  external  orifice  on  the  face.  There  it  terminates 
in  a  number  of  branches  named  the  infra-orbital  ramuscules  (or  pes  anserinus, 
from  their  resemblance  to  the  claws  of  a  goose's  foot). 

In  its  course,  this  nerve  gives  off  a  large  number  of  collateral  divisions, 
among  which  may  be  more  particularly  distinguished : 

1.  An  orbital  branch. 

2.  The  gt-^eat  or  anterior  palatine  nerve. 

3.  The  staj)hylin  ov  posterior 'palatine  nerve. 

4.  The  nasal  or  spheno-palatine  nerve. 

5.  The  dental  nerves. 

In  addition  to  which  are  described  : 

6.  The  infra-orbital,  or  terminal  branches  of  the  superior  maxillary 
nerve. 

1.  Orbital  Branch  (Fig.  335,  13). — This  ramuscule  arises  in  the  inte- 
rior of  the  suprasphenoidal  canal,  and  enters  the  ocular  sheath  with 
the  divisions  of  the  ophthalmic  branch.  It  almost  immediately  breaks  up 
into  two  or  three  very  slender  filaments,  which  ascend  to  the  temporal  angle 
of  the  eye,  passing  between  the  fibrous  lining  of  the  orbit  and  the  outer 
surface  of  the  motor  muscles  of  the  eye,  and  are  distributed  to  the  eyelids 
and  neighbouring  integuments. 

2,  Great   or  Anterior   Palatine   Nerve    (Fig.    148,  3). — It    arises 


THE  CRANIAL  OE  ENCEPHALIC  NERVES.  713 

from  the  superior  maxillary  nerve  at  the  orbital  hiatus,  from  a  trunk  common 
to  it  and  the  nasal  and  staphylin  branches ;  it  passes  into  the  palatine  canal 
with  the  palato-labial  artery,  which  it  follows  to  the  foramen  incisivum, 
where  it  stops. 

During  its  course  in  the  palatine  canal,  this  nerve  throws  off  two  or  three 
small  filaments,  which  escape  by  particular  foramina  to  the  anterior  part  of 
the  soft  palate — median  palatine  nerve.  Frequently  they  arise  from  a  common 
trunk  before  the  great  palatine  nerve  enters  its  canal,  and  pass  to  their 
destination  by  particular  openings.  For  the  remainder  of  its  extent  on  the 
roof  of  the  palate,  this  nerve  forms,  around  the  artery  it  accompanies,  a 
plexiform  network  similar  to  that  of  the  ganglionic  nerves  ;  the  filaments 
escaping  laterally  from  it  are  sent  to  the  soft  parts  of  the  palate,  as  well  as 
to  the  gimis. 

3.  Staphtlin  or  Posterior  Palatine  Nerve  (Fig.  148,  8). — The 
filaments  composing  this  nerve  are  very  easily  separated,  and  frequently 
anastomose  with  those  of  the  preceding  nerve.  They  accompany  the 
palatine  artery  in  the  caual  of  that  name,  bend  in  front  of  the  pterygoid 
i:)rocess  to  penetrate  the  soft  palate  between  the  glandular  layer  and  the 
tunica  albuginea.  They  then  become  inflected  backwards,  and  ramify 
either  in  the  mucous  and  glandular  tissues  of  the  velum  pendulum,  or  the 
palato-phaxyngeal  and  circumflexus-palati  muscles.  This  destination, 
tlierefore,  indicates  in  this  nerve  the  presence  of  motor  fibres  ;  we  will  see 
hereafter  whence  they  come. 

4.  Nasal  or  Spheno-palatine  Nerve. — Springing  from  the  same 
trunk  as  the  two  preceding  nerves,  thicker  than  the  staphylin,  and  nearly  of 
the  same  volume  as  the  anterior  palatine,  the  nasal  nerve  passes  with  its 
artery  into  the  nasal  or  spheno-palatine  foramen,  to  penetrate  the  cavity 
of  the  nose,  where  it  separates  into  two  branches — external  and  internal, 
which  are  distributed  to  the  j^ituitary  membrane. 

5.  Dental  Branches. — These  are  destined  to  the  roots  of  the  upper 
teeth,  and  proceed  from  the  superior  maxillary  nerve  during  its  inter- 
maxillary course ;  some  even  arise  before  the  entrance  of  that  nerve  into  the 
bony  conduit,  which  it  passes  through  to  reach  tlie  face.  These  latter, 
analogous  to  the  posterior'  dental  nerve  of  Man,  enter  the  canal  with  the 
parent  branch,  and  throw  thcr  divisions  into  the  roots  of  the  last  molar 
tooth,  and  sometimes  also  into  the  second  last.  One  portion  of  them 
plunges  directly  into  the  maxillary  protuberance,  to  be  expended  in  the 
mucous  membrane  lining  that  protuberance,  after  furnishing  softe  fila- 
ments to  the  periosteum. 

Among  the  dental  branches  given  off  from  the  maxillary  nerve  during 
its  interosseous  course,  some  pass  to  the  molars,  and  others  to  the  canine  and 
incisor  teeth.  The  first,  or  middle  dental  nerves,  separate  in  groups  from 
the  maxillary  trunk  on  its  passage  above  the  roots  of  the  grinding-teeth ; 
they  penetrate  these  roots  after  a  brief  forward  course,  and  give  some  thin 
filaments  to  the  membrane  lining  the  maxillary  sinuses. 

The  second  are  only  at  first  a  single  branch — the  anterior  dental  nerve, 
which  rises  from  the  maxillary  trunk  shortly  before  it  leaves  its  bony  canal. 
After  a  somewhat  long  track  in  the  substance  of  the  maxillary  bones,  this 
branch  becomes  expended  in  furnishing  the  ramuscules  for  the  canine 
tooth  and  the  incisors  ;  it  is  always  accompanied  by  a  very  slender  arterial 
twig. 

6.  Infra-orbital  or  Terminal  Branches  of  the  Superior  Maxil- 
lary Nerve. — These  ramuscules  spread  on  the  side  of  the  face  in  a  magni- 


714 


THE  NERVES. 


ficent  expansion,  which  may  be  looked  upon  as  one  of  the  richest  nervous 
apparatus  in  the  animal  economy.  Covered  at  its  emergence  from  the  infra- 
orbital foramen  by  the  supermaxillo-labialis  muscle,  this  fasciculus  descends 
beneath  the  supernasalis-labialis  and  pyramidal  muscle  of  the  nose  (super- 
maxillo-nasalis  magnus)  towards  the  nostrils  and  upper  lip,  which  receive 
the  terminal  extremities  of  its  constituent  branches  in  the  substance  of  their 
muscular  and  tegumentary  tissues  ;  these  branches  are  slightly  divergent  and 
flexuous,  and  for  the  most  part  anastomose  with  a  large  motor  trunk  furnished 
by  the  facial  nerve  (Figs.  336,  15')- 

C.  Inferior  Maxillary  Nerve  (Figs.  336, 11 ;  110, 12). — At  its  exit  from 

Fis:.  336. 


GENERAL    VIEW    OF    THE    SUPERIOR    AND    INFERIOR    MAXILLARY    NERVES. 

The  eye  has  been  excised,  after  sawing  through  and  removing  the  orbital  and 
zygomatic  processes.  The  maxillary  sinuses  have  been  exposed  by  means  of  a 
gouge  or  chisel,  the  masseter  muscle  removed,  and  the  inferior  maxilla  opened  to 
show  the  nerve  in  its  interosseous  course. 

1,  Facial  nerve ;  2,  Origin  of  the  posterior  auricular  nerve  ;  3,  Filament  distributed 
to^he  stylo-hyoid  muscle  ;  4,  Digastric  branch  ;  5,  Trunk  of  the  anterior  auricular 
nCTve ;  6,  Origin  of  the  cervical  filament ;  7,  Plexus  formed  by  the  union  of  the 
facial  and  superficial  temporal  nerve ;  7',  Branch  of  that  plexus  united  to  the 
infra-orbital  nerves,  15';  11,  Inferior  maxillary  nerve;  8,  Superficial  temporal 
nerve;  9,  Masseteric  nerve ;  10,  Gustatory  nerve;  12,  12,  Dental  branches;  13, 
Mylo-hyoid  nerve;  14,  Buccal  nerve;  15,  Superior  maxillary  nerve;  16,  Spheno- 
palatine ganglion;  17,  Staphylin  (or  palatine)  nerve;  18,  Common  carotid 
artery;  19,  Trunk  of  the  occipital;  20,  Trunk  of  the  internal  carotid;  21, 
Jlxternal  carotid ;  22,  Trunk  of  the  posterior  auricular  artery  embraced  by  a 
loop  of  the  facial ;  2)i,  Trunk  of  the  superficial  temporal ;  24,  Internal  maxillary 
artery  ;  25,  Trunk  of  the  deep  anterior  temporal  artery ;  26,  Orbital  branch  of 
the  superior  dental ;  27,  Buccal  artery  ;  28,  Inferior  dental  artery. 


the  cranium,  this  branch  is  situated  immediately  within  the  tempoi'o- 
maxillary  articulation,  and  from  thence  is  directed  forward  and  downward, 
passing  at  first  between  the  two  pterygoid  muscles,  then  between  the  inner 
and  deejD  face  of  the  maxilla,  arriving  at  the  maxillo-dental  foramen,  through 
which  it  passes  and  runs  along  the  whole  course  of  the  canal,  escaping  at 
last  by  the  mental  foramen  to  form  an   expansion  of  terminal  branches 


THE  CBAMAL  OR  ESCEPHALIC  NERVES.  715 

similar  to  those  of  the  superior  maxillary  nerve,  and  named  the  mental 
nerves. 

For  the  first  third  of  its  extent,  the  inferior  maxillary  nerve  is  a  flattened 
band  ;  but  beyond  this  it  becomes  thicker,  and  acquires  a  funicular  shape. 

At  its  origin  it  gives  rise  to  four  branches : 

1.  The  masseteric  nerve. 

2.  The  buccal  nerce. 

3.  The  nerve  of  the  internal  pterygoid  muscle. 

4.  The  superficial  temporal  or  suhzygomatic  nerve. 

After  its  emergence  from  between  the  two  pterygoid  muscles,  it  furnishes : 

5.  The  gustatory  nerve. 

6.  The  mylo-hyoid  nerve. 

In  its  intermaxillary  course,  it  detaches  : 

7.  The  dental  branches. 

Also  a  triple  series  of  collateral  nerves  which  we  will  study  before 
describing  the  terminal  branches ;  these  are  : 

8.  The  mental  nerves. 

The  trunk  of  the  inferior  division  of  the  fifth  pair  represents  a  mixed 
nerve,  because  it  is  formed  of  sensitive  and  motor  fibres.  Is  it  the  same  for 
each  of  the  branches  just  enumerated  ;  that  is,  do  they  all  contain  fibres  of 
the  two  orders  ?  This  is  a  question  on  which  the  dissection  of  the  two 
roots  has  taught  us  very  little,  for  their  fibres  soon  become  confounded  so 
intimately  that  it  has  always  been  found  impossible  to  follow  them  separately 
into  each  nerve.  But  the  study  of  the  distribution  of  these  branches,  corrobo- 
rated by  physiological  experiments,  has  greatly  enlightened  us  in  this 
inquiry.  We  see  among  them  nerves  destined  to  the  muscles,  and  others 
to  glandular  or  integumental  structures ;  the  first  are  therefore  chiefly 
composed  of  motor  fibres,  like  all  other  muscular  nerves ;  and  the  second 
exclusively  contain  sensitive  fibres,  or  at  least  are  deprived  of  voluntary 
motor  fibres.  In  describing  each  branch  in  particular  we  will  notice 
their  special  properties. 

1.  Masseteric  Nerve  (Figs.  336, 9 ;  342, 2). — It  is  detached  from  the  prin- 
cipal trunk,  in  front,  though  close  to,  the  base  of  the  cranium,  bends  roimd 
the  anterior  face  of  the  temporo-maxillary  articulation,  and  passes  through 
the  sigmoid  notch  of  the  inferior  maxilla  to  descend  into  the  texture  of  the 
masseter  muscle  and  there  ramify. 

At  its  origin,  this  nerve  furnishes  two  filaments  which  often  proceed 
from  one  very  short  trunk,  and  ascend  into  and  expend  themselves  in  the 
temporal  muscle  ;  this  trunk  is  then  the  deep  posterior  temporal  nerve. 

Before  crossing  the  corono-condyloid  notch,  it  detaches  to  this  same 
temporal  muscle  a  small  branch  which  represents  the  deep  middle  temporal 
nerve. 

The  destination  of  all  these  branches  sufficiently  proves  that  they  are 
motor. 

2.  BnccAL  Nerve  (Figs,  336,  14 ;  342,  4).— This  nerve,  which  is  twice  the 
size  of  the  preceding,  arises  from  the  same  point,  though  slightly  below  it.  It 
is  directed  forwards,  traverses  the  external  pterygoid  muscle,  and  reaches  the 
posterior  extremity  of  the  superior  great  molar  gland;  leaving  which,  it  is 
placed  beneath  the  buccal  mucous  membrane,  and  descends  to  the  conmiissure 
of  the  lips,  along  the  inferior  molar  gland  and  the  inferior  border  of  the 
alveolo-labialis  muscle. 


716  THE  NEBVES. 

It  gives  some  very  fine  filaments  to  the  external  pterygoid,  in  its  passage 
across  that  muscle.  Beyond  this,  it  furnishes  a  very  slender  ramuscule  to 
the  orbital  portion  of  the  temj)oral  muscle — the  analogue  of  the  anterior  deep 
temporal  of  Man. 

Oq  the  superior  molar  gland,  it  emits  a  fasciculus  of  branches  to  this 
organ  and  the  alveolo-labialis  muscle.  In  its  submucous  track  it  throws 
off,  at  certain  distances,  ramuscules  of  various  sizes  which  go  to  the 
inferior  molar  gland  and  the  buccal  membrane ;  while  its  terminal  filaments 
are  expended  in  the  lining  membrane  and  glands  of  the  lips,  near  the 
commissure. 

The  majority  of  the  filaments  given  off  by  this  nerve  to  the  external 
pterygoid  aud  temporal  muscles  are  doubtless  motor,  but  the  other  ramus- 
cules are  sensitive;  even  those  distributed  to  the  alveolo-labialis  muscle 
are  no  exception,  for  its  submasseteric  portion  is  supplied  by  the  facial,  as 
well  as  the  superficial  or  anterior  part. 

3.  Internal  Pterygoid  Neeve. — It  forms,  with  the  preceding  nerves, 
a  single  fasciculus,  which  leaves  the  anterior  part  of  the  inferior  maxillary 
nerve.  After  crossing,  outwardly,  the  internal  maxillary  artery,  it  descends 
between  the  nervous  trunk  from  which  it  emanated,  and  the  external  layer 
of  the  tensor  palati  muscle,  to  go  to  the  inner  side  of,  and  become  expended 
in,  the  internal  pterygoid  muscle. 

This  nerve  is  the  smallest  branch  of  the  inferior  maxillary  trunk,  after 
the  mylo-hyoid,  and  excites  the  contraction  of  the  muscle  receiving  it. 

4.  Superficial  Temporal  or  Subztgomatic  Nerve  (Figs.  336,  8  ;  342,  3). 
— This  arises  from  the  inferior  maxillary  nerve,  at  the  opposite  side  of  the 
fasciculus  formed  by  the  three  preceding  branches,  or  posteriorly.  Placed  at 
first  at  the  inner  side  of  the  temporo-maxillary  articulation,  and  between  it 
and  the  guttural  pouch,  it  is  afterwards  directed  downwards  and  outwards, 
passes  between  the  parotid  gland  aud  the  posterior  border  of  the  inferior 
maxilla,  and  below  the  condyle ;  it  then  bends  round  the  neck  of  that  bony 
eminence  to  arrive  beneath,  and  to  the  outside  of,  the  precited  articulation, 
where  it  terminates  by  anastomosing  with  the  facial  nerve. 

In  its  course  it  sends  off  numerous  fine  filaments  to  the  guttural  pouch, 
the  parotid  gland,  and  the  integuments  of  the  temporal  region.  Among 
the  latter,  it  is  necessary  to  notice  more  particularly  those  which  accompany 
the  superficial  temporal  artery. 

The  superficial  temporal  nerve  appears  to  be  exclusively  sensitive. 
Section  of  it,  before  it  anastomoses  with  the  facial  nerve,  does  not  really 
prevent  contraction  of  the  muscles  which  receive  the  divisions  of  the  plexus 
formed  by  this  anastomosis. 

5.  Gustatory  Nerve ^  (Figs.  Ill,  17;  336.  10;  342,5).— The  gustatory 
nerve,  the  principal  branch  of  the  inferior  maxillary  trunk,  which  it  almost 
equals  in  volume,  is  detached  at  an  acute  angle  from  the  anterior  border  of  that 
nerve  shortly  after  its  exit  from  the  pterygoid  muscles.  To  accomplish  its 
course,  which  it  effects  in  describing  a  slight  curve  whose  concavity  is  antero- 
posterior, it  is  directed  forwards  and  downwards,  passing  between  the 
internal  pterygoid  muscle  and  the  branch  of  the  inferior  maxillary  bone, 
and  gaining  the  base  of  the  tongue,  where  it  is  situated  beneath  the 
buccal  mucous  membrane.  It  afterwards  descends  more  deeply,  between 
the  mylo-hyoid  and  hyo-glossus  longus  muscles,  turns  round  the  inferior 

•  (Professor  Cliauveau  designates  th's  the  lingual,  or  small  hypoglossal  nerve.  To 
prevent  confusion  I  have,  in  preference,  retained  the  usual  designation  given  to  it  in  thia 
countrj\) 


THE  CRANIAL  OR  ENCEPHALIC  NERVES.  717 

border  of  the  latter — -includiug  also  Wharton's  duct,  to  enter  the  inter- 
stice sejjarating  the  geuio-glossus  from  the  hyo-glossus  longus  and  brcvis 
mnscles.  From  this  jioiut  it  continues  to  near  the  free  extremity  of  the 
tongue,  proceeding  iu  a  very  flexuous  manner,  and  giving  ofl",  on  its  course, 
divisions  equally  tortuous  and  which  traverse  the  organ,  but  without 
detaching  any  ramuscules  to  the  lingual  muscles ;  these  divisions  terminate 
in  the  middle  and  anterior  jiortions  of  the  lingual  mucous  membrane. 

Before  penetrating  the  mass  of  the  tongue,  tliis  nerve  fiu*nishes  :  1,  At, 
and  in  front  of,  the  posterior  pilLirs  of  tliat  organ,  some  small  ramuscules 
which  are  sometimes  plexiform,  and  are  distributed  to  the  mucous 
membrane  at  the  base  of  the  tongue ;  2,  Lower,  and  behind,  one  or  two 
thiin  filaments  which  are  carried  to  Wharton's  duct,  and  ascend  with  it 
to  the  maxillary  gland ;  3,  A  sitbUngual  branch,  whose  divisions  enter  the 
gland  t)f  that  name,  as  well  as  the  mucous  membrane  covering  the  sides  of 
the  tongue. 

The  gustatory  nerve  receives,  near  its  origin,  the  tympano-lingual  filament 
or  chorda  tympani — a  branch  of  the  facial  nerve  soon  to  be  described.  Its 
terminal  divisions  mix  and  anastomose  with  those  of  the  great  hypoglossal 
nerve,  in  the  deep  muscular  interstice  which  lodges  both. 

Physiology  teaches  us  that  the  gustatory  nerve  gives  to  the  anterior 
two-thii'ds  of  the  lingual  mucous  membrane  ordinary  sensation,  and,  in 
addition,  that  special  sensibility  (or  gustatory  power)  by  virtue  of  which 
that  membrane  enjoys  the  property  of  appreciating  savours.  This  is  its 
exclusive  function.  With  regard  to  the  tympanic  filament  from  the  facial 
nerve,  and  which  is  joined  to  the  gustatory,  M.  Bernard  is  of  opinion  that  it 
participates  iu  the  exercise  of  this  sense  of  taste.  Its  radiating  fibres  extend 
to  the  submucous  muscular  layer  of  which  we  have  spoken,  and  on  which 
the  lingual  papillae  rest,  and  endow  it  with  the  property  of  acting  on  these 
papilljB  by  adapting  them,  we  may  say,  to  the  sapid  substances  brought  into 
contact  with  them.  Lussana  goes  further  than  this,  and,  basing  his  state- 
ment on  observations  made  on  Man  and  on  experiments,  asserts  that  the 
nerve  of  the  tympanum  jDasses  to  the  mucous  membrane,  and  endows  it  with 
the  sense  of  taste.  Vulpian.  however,  does  not  agree  to  either  of  these 
opinions,  because,  according  to  his  experience,  this  nerve  does  not  go  to  the 
tongue,  but  stops  at  the  submaxillary  ganglion. 

6.  Mylo-htoid  Nerve  (Fig.  336,  13). — The  designation  of  this  nerve 
indicates  its  destination  and  uses.  It  goes  to  the  muscle  bearing  its  name, 
and  excites  its  contractility ;  it  arises  opposite  to  the  preceding,  and,  like 
it.  descends  between  the  internal  pterygoid  muscle  and  the  inferior  max- 
illary bone,  adhering  somewhat  closely  to  the  lattei*.  But  arriving  at  the 
posterior  border  of  the  mylo-hyoideus,  it  passes  to  the  outside  of  it,  and 
meeting  with  the  sublingual  artery,  ramifies  on  the  external  face  of  that 
muscle. 

7.  Dental  Branches  (Fig.  336,  12). — These  are  of  two  orders:  some 
passing  to  the  molar,  the  others  to  the  canine  and  incisor  teeth.  Their 
description  does  not  merit  any  special  indication. 

8.  Mental  Nerves,  or  Terminal  Branches  of  the  Inferior  Maxillabt 
Nerve. — Perfectly  analogous  to  the  infra-orbital  ramuscules,  these  nerves 
form  a  fasciculus  by  diverging  and  flexuous  branches,  which  leave  the 
mental  foramen  to  be  distributed  to  the  textures  of  the  lower  lip,  after 
receiving  a  branch  from  the  facial  nerve  (Fig.  336,  11'). 

D.  The  Sympathetic  Ganglia  annexed  to  the  Fifth  Pair. — These 
ganglia,  joined  by  filaments  of  communication  to  the  anterior  extremity 


718  THE  NERVES. 

of  the  great  sympathetic  nerve,  in  reality  belong  to  the  special  system 
formed  by  that  nervous  chain,  as  they  possess  the  formation  and  properties 
of  the  other  ganglia  composing  it.  It  is  therefore  necessary  that  we  should 
have  a  motive  sufficiently  powerful  to  induce  us  to  move  them  from  their 
natural  category,  and  mix  up  their  description  with  a  nerve  so  different  to 
them  in  its  nature  and  functions.  This  motive  we  find  in  the  intimate 
relations  of  contiguity  and  continuity  which  these  ganglia  manifest  towards 
the  branches  of  the  trigemini  ;  in  the  fact  that  we  sometimes  find  them  united 
to  these  branches,  and  deeply  mixed  up  with  their  fibres  ;  and  also  because, 
in  certain  cases,  they  seem  to  disappear  entirely,  and  then  their  filaments 
of  emission  or  reception  are  directly  received  or  emitted  by  the  fifth  pair. 

The  study  we  are  about  to  undertake  of  each  of  the  ganglia  will  fully 
justify  what  we  have  advanced.  We  will  precede  it  by  a  few  words  of 
introduction  as  to  the  general  facts  relating  to  these  small  organs. 

The  number  of  sympathetic  ganglia  annexed  to  the  fifth  pair  is  suscep- 
tible of  variation,  not  only  in  different  species,  but  also  with  individuals 
of  the  same  species. 

In  the  domesticated  mammifers,  we  somewhat  constantly,  though  not  in- 
variably, find  three  principal,  placed  on  the  course  of  the  branches  ema- 
nating from  the  Gasserian  ganglion.  These  are  :  1,  The  ophthalmic  ganglion, 
belonging  to  the  nerve  of  the  same  name  ;  2,  The  spheno-palatine  ganglion, 
annexed  to  the  superior  maxillary  branch  ;  3,  The  otic  ganglion,  which  lies 
beside  the  inferior  maxillary  nerve.  Anatomists  describe  other  two,  the 
submaxillary  ganglion  and  the  naso-palatine  (or  Gloquet's)  ganglion ;  but 
their  presence  is  not  always  constant  in  Solipeds,  and  their  existence  in  the 
other  domesticated  animals  is  at  least  problematical. 

These  small  bodies  possess  those  common  characters  which  have  been 
so  clearly  indicated  by  Longet,  and  to  which  we  will  briefly  refer.  All 
are  in  communication  with  the  superior  cervical  ganglion  by  one  or  more 
generally  very  slender  filaments,  and  all  receive  one  or  more  ramuscules 
from  a  sensitive  and  a  motor  nerve  :  these  ramuscules — the  afferent  hranchfs 
of  the  ganglia — are  considered  as  their  roots.  All,  finally,  emit  from  their 
periphery  a  more  or  less  considerable  number  of  emergent  branches  or  ramifi- 
cations whicli  share  the  proj^erties,  more  or  less  modified,  of  the  two  orders 
of  roots.  The  description  of  each  ganglion  therefore  includes,  indepen- 
dently of  its  form,  situation,  etc.,  an  indication  of  all  these  ramuscules: 
ramuscules  of  communication  with  the  superior  cervical  ganglion ;  afferent 
ramuscules  or  roots ;  and  emergent  ramuscules.  This  rule  can  be  applied  to 
all  the  ganglia,  and  renders  their  study  perfectly  methodical. 

1.  Ophthalmic  (Ciliary  or  Lenticular)  Ganglion. — This  ganglion 
is  readily  discovered,  as  it  is  always  in  contact  with  the  common  oculo- 
motor nerve,  and  united  to  it  near  the  point  where  the  branch  passing  to 
the  inferior  oblique  muscle  arises.  It  rarely  exceeds  the  volume  of  a  grain 
of  millet,  and  is  sometimes  so  minute  that  it  would  altogether  escape  ob- 
servation, did  we  not  know  exactly  where  to  look  for  it. 

Its  motor  root  is  generally  formed  of  two  very  short  ramuscules  coming 
from  the  third  pair.  Its  sensitive  root,  much  longer,  proceeds  from  the 
palpebro-nasal  nerve  ;  it  is  usually  through  the  medium  of  this  root  that 
the  ophthalmic  ganglion  communicates  with  the  superior  cervical  ganglion, 
by  means  of  a  thin  filament  it  receives  from  the  cavernous  plexus. 

The  emergent  filaments  leave  the  anterior  part  of  the  ganglion,  and 
arrange  themselves  in  a  flexuous  manner  around  the  optic  nerve  to  reach 
the  sclerotica,  bearing  the  name  of  ciliary  nerves.     Some  emanate  directly 


THE  CRANIAL  OR  ENCEPHALIC  NERVES.  719 

from  the  palpebro-nasal  nerve,  especially  when  the  ganglion  is  rudimentary, 
Their  number  is  uncertain,  though  it  is  usually  from  5  to  8. 

Reaching  the  sclerotica  at  the  bottom  of  the  eye,  they  traverse  that 
membrane,  and  pass  between  its  inner  surface  and  choroid  coat  to  the 
ciliary  circle  (or  ligament),  where  each  divides  into  two  or  three  ra- 
muscules  that  anastomose  with  those  of  the  adjacent  ciliary  nerves,  and  in 
this  manner  form  a  circular  plexus.  From  the  concavity  of  this  nervous 
circle  arises  a  series  of  plexuous  divisions,  which  are  spread  over  the  iris, 
whose  contractile  property  is  submitted  to  their  influence. 

2.  Spheno-palatine,  or  Meckel's  Ganglion.  —  The  largest  of  the 
cephalic  ganglia,  nothing  is  more  variable  than  the  disposition  of  this  small 
body.  The  following  appears  to  be  the  most  constant :  in  raising  the 
superior  maxillary  nerve  in  its  course  across  the  space  separating  the 
orbital  from  the  maxillary  hiatus,  Ave  discover,  lying  on  the  upper  border 
of  the  splieno-palatine  nerve,  a  long,  grey-coloured  enlargement;  this 
constitutes  the  ganglion  we  are  about  to  describe. 

It  is  elongated  and  slender,  ii-regularly  fusiform,  constricted  at  different 
points  of  its  extent  and  dilated  in  others  ;  it  is  not  attached  to  the  spheno- 
palatine nerve  by  simple  cellular  adhesions  or  by  some  branches  thrown 
from  one  cord  to  the  other,  but  is  intimately  united  to  it  by  means  of  a 
most  complicated  intercrossing  of  fibres,  in  such  a  way  that  the  spheno- 
palatine ganglion  really  forms  jJart  of  the  nerve  of  that  name. 

Afferent  branches. — It  receives,  posteriorly,  the  Vidian  nerve,  a  com- 
posite ramuscule  which  constitutes  its  motor  root,  and  connects  it  with  the 
superior  cervical  ganglion.  This  nerve  will  be  described  with  the  facial, 
as  that  trunk  furnishes  its  principal  portion.  Its  sensitive  roots  naturally 
come  from  the  spheno-palatine  nerve ;  they  are  as  remarkable  for  their 
number  as  theii"  volume,  and  also  enter  the  posterior  part  of  the  ganglion. 

Emergent  branches.— Four  series  of  these  are  recognisi  d: 

1.  A  very  numerous  series  which  is  detached  at  a  right  angle  from  the 
superior  border  of  the  ganglion,  and  proceeds  towards  the  ocular  sheath. 
The  majority  appear  to  be  lost  in  that  fibrous  membrane,  but  we  have 
seen  some  pass  through  it,  creep  on  the  lower  and  inner  wall  of  the  orbit, 
and  arrive  at  the  margin  of  the  orbital  foramen.  There  they  were  manifestly 
united  to  the  other  filaments  coming  from  the  palpebro-nasal  nerve,  and 
formed  a  small  plexus  whose  divisions  seemed  destined  to  the  oj)hthalmic 
vessels,  and  even  to  some  of  the  muscles  of  the  eye,  more  especially  the 
obliqiie  ones.  Among  these  divisions  we  have  observed  some  which  went 
to  join  the. nerve  of  the  membrana  nictitaus. 

2.  A  second  series  proceeding  from  the  opposite  border,  and  establishing 
a  union  between  the  ganglion  and  the  spheno-palatine  nerve,  or  passing  to  the 
palatine  nerves  in  a  more  or  less  complicated  plexiform  manner,  to  reinforce 
them. 

3.  A  group  arising  from  the  anterior  extremity  and  immediately  passing 
to  the  spheno-palatine  nerve. 

4.  A  last  fasciculus  detached  from  the  posterior  extremity  to  enter  the 
two  great  suprasphenoidal  canals. 

Such  is  the  most  usual  arrangement  of  the  spheno-palatine  ganglion. 
We  have  found  it  divided  into  three  small  masses  connected  with  each 
other  by  numerous  filaments  of  a  deep  grey  colour,  and  free  from  all  ad- 
herences  with  the  spheno-palatine  nerve.  The  small  posterior  mass  in  this 
case  received  the  Vidian  nerve  and  the  sensitive  roots  from  the  fifth  jiair. 
The  distribution  of  the  emergent  branches  was  unaltered. 


720  THE  NERVES. 

Among  the  anatomo-physiological  facts  pertaining  to  tlie  study  of  this 
ganglion,  we  may  remark  that  the  staphylin,  or  posterior  palatine,  nerve 
derives  from  it  the  motor  property  which  permits  it  to  excite  the  con- 
traction of  the  muscles  in  the  soft  palate. 

3.  Otic  (or  Arnold's)  Ganglion. — It  appears  to  us  that  the  presence 
of  this  ganglion  is  not  constant,  for  we  have  sometimes  found  it  replaced 
by  a  small  plexus  provided  with  some  almost  microscopic  ganglionic 
granulations. 

When  it  does  exist,  it  presents  itself  as  a  small  fusiform  enlargement 
placed  within  the  origin  of  the  inferior  maxillary  nerve,  beneath  the  inser- 
tion of  the  Eustachian  tube.  To  discover  it,  we  have  only  to  look  for  the 
commencement  of  the  buccal  nerve,  to  which  it  is  joined  by  some  filaments 
which  are  so  short  and  thick,  that  we  might  imagine  it  to  be  fixed  on  that 
trunk. 

Its  sensitive  roots  are  represented  by  the  preceding  filaments.  The  small 
superficial  petrous  nerve,  coming  from  the  facial,  constitutes  its  motor  root. 
From  the  sympathetic  ramuscule  accompanying  the  internal  maxillary 
artery,  it  receives  its  filament  of  communication  with  the  superior  cervical 
ganglion. 

Among  its  emergent  ramuscides  must  be  cited  a  superior  filament,  which 
enters  the  petrous  portion  of  the  temporal  bone  to  disappear  in  the  internal 
muscle  of  the  malleus  (tensor  tympani),  and  two  inferior  filaments  of  a 
more  considerable  volume  which  separate  in  numerous  ramuscules  destined 
to  the  pterygoid  muscles,  the  Eustachian  tube,  and  the  tensor  palati 
muscle. 

Physiological  Kesume  of  the  Fifth  Pair. — The  trigemini  convey 
sensation  to  the  skin  covering  the  head,  into  the  eyelids,  the  soft  and  hard 
palate,  the  nasal  fosste  and  sinuses,  the  nostrils,  the  greater  portion  of  the 
tongue,  and  into  the  salivary  glands  and  cheeks,  and  the  upper  and  lower  lips. 
The  enormous  tuft  formed  by  the  terminal  branches  of  the  superior 
maxillary  nerve,  endow  the  upper  lip  with  the  attributes  of  an  organ  of  very 
exquisite  tact. 

The  gustatory  branch  is,  for  the  anterior  two-thirds  of  the  tongue,  the 
essential  instrument  of  the  sense  of  taste. 

By  its  motor  root,  the  inferior  maxillary  nerve  provokes  the  contraction 
of  the  muscles  that  bring  the  jaws  into  apposition — all  those  comjiosing  the 
masseteric  region,  except  the  digastricus.  This  root  is  often  designated,  in 
consequence  of  its  function,  the  masticatory  nerve. 

The  fifth  pair  also  influences,  as  is  demonstrated  by  vivisections  and  the 
observation  of  pathological  facts,  the  secretion  of  the  mucous  membranes 
and  glands  receiving  its  filaments:  undoubtedly  by  a  reflex  action  which 
proceeds  from  the  isthmus,  and  perhaps  from  the  Gasserian  ganglion. 

Finally,  it  is  admitted  that  the  nutrition  of  the  tissues  in  which  the 
trigeminus  ramifies  depends  upon  that  nerve.  But  here  there  is  an  exagge- 
ration ;  for  if  nutrition  be  modified  in  these  tissues,  consequent  on  the 
section  of  the  fifth  pair,  this  efl'ect  is  certainly  due  to  paralysis  of  the 
capillaries,  whose  contractility  is  probably  excited  by  the  organic  motor 
fibres  mixed  with  the  sensitive  filaments  of  the  fifth  pair. 

The  ramuscules  sent  by  the  symjjathetic  chain  to  the  Gasserian  ganglion, 
are  perhaps  not  foreign  to  the  part  the  fifth  pair  seems  to  play  in  the 
secretory  and  nutritive  functions. 


TEE  CBANIAL  OR  ENCEPHALIC  NERVES.  721 

6.  Sivth  Pair  (Ahducentcs),  or  External  Ocuh-motor  Nerves.     (Fig.  335,  5.) 

The  external  ocuh-motor  origiuates  from  the  medulla  oblongata,  imme- 
diately behind  the  jions  Varolii,  by  from  five  to  eight  converging  roots, 
which  appear  to  issue  from  between  the  inferior  corpus  pyramidale  and  the 
lateral  fasciculus  of  the  medulla  (Figs.  337,  338,  h). 

It  is  directed  immediately  forward,  leaves  the  pons  Varolii  in  lying  close 
to  the  inner  side  of  the  superior  maxillary  nerve,  and  traverses  the  sphe- 
noidal canal,  which  already  lodges  the  ophthalmic  branch  of  the  fifth  pair 
and  the  common  oculo-motor  nerve,  to  pierce  the  bottom  of  the  orbit.  It  is 
entii'ely  expended  in  the  external  rectus  (or  abductor)  muscle  of  the  eye, 
after  giving  o±f  a  small  ramuscule  to  the  external  portion  of  the  posterior 
rectus. 

7.  Seventh  Pair,  or  Facial  Nerves.     (Figs.  110,  336,  337,  338.) 

The  facial  {'portio  dura)  is  a  nerve  exclusively  motor  at  its  orgin,  but 
which  becomes  mixed,  during  its  course,  by  the  addition  of  several  sensitive 
branches. 

Origin. — It  emanates  from  the  medulla  oblongata,  immediately  behind 
the  pons  Varolii,  and  appears  to  originate  at  the  external  extremity  of  the 
transverse  band  that  margins  the  posterior  border  of  that  protuberance. 
But  if  we  attempt  to  trace  its  origin  in  the  substance  of  the  medulla 
oblongata,  we  see  the  single  fasciculus  it  constitutes,  at  its  point  of 
emergence,  descend  into  the  groove  of  separation  between  the  pons  Varolii 
and  the  above-mentioned  band  ;  it  then  traverses  nearly  the  whole  thickness 
of  the  medulla,  passing  between  the  lateral  cord  or  column,  and  that  portion 
of  the  restiform  body  which  is  continuous  with  the  large  root  of  the  fifth 
pair.  Arrived  near  the  bottom  of  the  fourth  ventricle,  the  facial  nerve 
separates  into  several  roots — some  » 

anterior,  others  posterior — which  Fig.  337. 

are  soon  lost  in  the  cells  forming  ^<^h^f<rfctnitu. 

the  corresponding  nucleus.  Among 
these  fibres  are  some  which  remain 
isolated  from  the  preceding,  and, 
passing  the  median  line,  enter  the 
facial  nucleus  of  the  opjiosite  side  ^'^"^ 
(Fig.  337). 

Course. — Scarcely      has      the 
facial     nerve    left     the     medulla 
oblongata,    before^  it    is   clirected    ^^^^^^  ^^^^^  -...^.ovgu  the  sujimit  of  the 
outwards,  to  pass  into  the  internal       medulla   oblongata,  showing  the   deep 
auditory  meatus,  along  with   the       origixs  of  the  fifth  and  sixth  nerves, 
auditory  nerve,  which  lies  in  con-       ^^'d  portio  dura  of  the  seventh. 
tact  with  it  behind.     It  afterwards 

enters  the  aqueduct  of  Fallopius,  courses  along  it,  and  follows  its  inflexions, 
which  results  in  its  forming  a  bend  forward  at  a  sliort  distance  from  the 
internal  opening  of  the  canal,  and  a  curve  whose  concavity  is  anterior,  on 
its  passage  behind  the  cavity  of  the  tympanum.  On  leaving  the  aqueductus 
Fallopii  by  the  stylo-mastoid  foramen,  it  is  hidden  beneath  the  deep  face 
of  the  parotid  gland,  and  continues  to  be  inflected  forward,  passing  between 
that  gland  and  the  guttural  pouch,  and  reaches  the  posterior  border  of  the 
inferior  maxilla,  where  it  issues  from  beneath  the  anterior  margin  of  the 
parotid  to   become  superficial,  and   place  itself  on  the  masseter  muscle. 


722  THE  NERVES. 

immediately  beneath  tlie  temporo-maxillary  articulation.  There  it  ter- 
minates in  two  or  three  branches,  which  anastomose  with  those  of  the  super- 
ficial temporal  nerve  from  the  fifth  pair,  thus  forming  the  suhzygomatic 
plexus  (pes  anserinus,  Fig.  110). 

Distribution. a.  In  its  interosseous  course,  the  facial  nerve  successively 

furnishes  : 

1.  The  great  superficial  petrous  nerve  (nervus  petrosus  superficialis  major). 

2.  The  small  superficial  petrous  nerve  (nervus  petrosus  superficialis  minor). 

3.  The  filament  of  the  stapedius  muscle  (tympanic  branch). 

4.  The  chorda  tympani. 

It  communicates,  besides,  with  the  pneumogastric  nerve,  by  means  of  a 
voluminous  filament  described  as  : 

5.  The  anastomotic  branch  of  the  pneumogastric. 

b.  The  branches  it  emits  on  its  course  beneath  the  parotid  gland  arise 
either  from  its  superior  or  inferior  border  ;  they  are  : 

6.  Tlie  occipito-styloid  nerve. 

7.  The  stylo-hyoid  nerve. 

8.  The  digastric  nerve. 

9.  The  cirvical  ramuscule. 

10.  Filaments  to  the  guttural  pouch  and  parotid  gland. 

The  superior  branches  comprise  : 

11.  The  posterior  auricular  nerve. 

12.  The  middle  auricular  nerve. 

13.  The  anterior  auricular  nerve. 

c.  To  this  collection  of  collateral  ramuscules  are  added  the  terminal 
branches,  formed  by  their  anastomoses  with  the  superficial  temporal  nerve  : 

14.  Tlie  subzygomatic  plexus. 

A.  Collateral  Branches. —1.  Great  Superficial  Petrous  Nerve. — 
This  is  a  very  remarkable  ramuscule,  which  is  detached  from  the  bend  of 
the  facial  nerve  to  proceed  to  Meckel's  ganglion.  The  importance  of  the 
peculiarities  attaching  to  the  study  of  this  nerve  requires  us  to  call  special 
attention  to  its  origin,  course,  and  termination ;  though  the  details  into 
which  we  are  about  to  enter  may  be  omitted  by  the  student. 

Origin.  —  Ganglion  geniculare. — The  manner  in  which  the  great  super- 
ficial petrous  nerve  comports  itself  at  its  origin  is  yet  an  obscure  and 
controverted  fact,  on  which  however  light  is  beginning  to  be  thrown.  The 
following  is  the  most  general  opinion  :  This  nerve  arises  from  a  small  grey 
enlargement,  the  genicular  ganglion  (or  intumescentia  gangliformls),  placed 
on  the  course  of  the  facial  nerve,  at  the  summit  of  the  angle  which  that 
nervous  trunk  describes  after  its  entrance  into  the  aqueduct  of  Fallopius  ;  and 
the  presence  of  this  small  ganglion  on  the  seventh  pair  should  assimilate  the 
facial  to  a  mixed  nerve,  whose  sensitive  root  would  be  represented  by  the 
portio  intermedia  of  Wrisberg — a  thin  filament  comprised  between  the  seventh 
and  eighth  pair,  and  which  emanates  directly  from  the  medulla  oblongata  to 
pass  into  the  posterior  part  of  the  ganglion  geniculare. 

We  have  constantly  found  this  ganglion  in  the  domesticated  animals. 
There  exists,  in  fact,  on  this  angle  or  elbow  of  the  facial  nerve,  a  very  slight, 
grey,  conical  prominence,  composed  of  ganglionic  corpuscles  which  a  micro- 
scopical examination  readily  reveals,  and  giving  origin  on  its  apex  to  the 
great  superficial  petrous  nerve.     This  prominence,  which,  we  repeat,  is  very 


THE  CRANIAL  OR  ENCEPHALIC  NERVES.  723 

small,  forms  part  of  tlie  facial  nerve,  on  which  it  only  presents  a  kind  of 
intumescence.  We  have  never  seen  the  sharp  and  precise  limitation  of  its 
base  that  is  figured  in  the  majority  of  iconogi-aphies  of  human  anatomy. 

On  the  other  hand,  when,  on  portions  steeped  for  several  weeks  in  water 
acidulated  by  nitric  acid,  we  have  studied  the  constitution  of  the  great 
petrous  nerve,  even  at  its  origin,  we  have  found  it  formed  of  two  fasciculi 
very  easily  separated — one  internal,  the  other  external :  the  latter  alone  is 
continuous  with  the  geniculated  ganglion  ;  the  other  traverses  the  facial 
nerve  from  before  to  behind,  then  it  is  suddenly  inflected  inwards  to  ascend  to 
the  origin  of  the  nerve,  and  mix  with  its  fibres  ;  but  this  fasciculus  very  often 
maintains  its  independence  to  tlie  medulla  oblongata,  into  which  its  fibres 
penetrate  separately  ;  they  then  appear  as  a  small  particular  trunk  beside 
that  of  the  principal  nerve,  and  comprised  between  it  and  the  auditory. 
The  great  petrous  nerve  does  not,  therefore,  proceed  exclusively  from  the 
ganglion  geniculare,  as  considerable  portions  of  its  fibres,  entirely  destitute 
of  ganglionic  corpuscles,  emerge  directly  from  the  facial  nerve.  With 
regard  to  the  external  fasciculus,  the  separation  of  its  fibres  by  the  action  of 
the  acid  shows  very  plainly  that  the  grey  substance  of  the  ganglion  is  found 
almost  exclusively  on  their  track ;  and  if  we  trace  these  fibres,  like  those  of 
the  preceding  fasciculus,  into  the  substance  of  the  facial  nerve,  we  will  find 
that,  instead  of  proceeding  towards  its  origin,  they  appear  to  be  directed 
to  its  termination :  a  remarkable  circumstance,  which  we  believe  may  bo 
explained  by  admitting  that  they  come  from  tbe  anastomosing  branch  of  the 
pneumogastric  nerve,  of  which  we  will  speak  hereafter. 

From  this  arrangement,  it  results  that  the  great  petrous  nerve  arises 
from  the  facial  by  two  real,  though  intimately  connected,  roots  :  the  internal 
is  evidently  motor ;  the  internal  possesses  the  ganglionic  corpuscles  of  a 
sensitive  root ;  and  the  trunk  they  both  form  may  be  regarded  as  a  mixed 
nerve. 

As  will  be  observed,  our  view  of  the  ganglion  geniculare  differs  from 
the  general  opinion  with  regard  to  it,  inasmuch  as  we  make  it  belong 
exclusively  to  the  great  petrous  nerve,  and  not  to  the  whole  of  the  facial 
fasciculi.  On  the  other  hand,  the  portio  intermedia  of  Wrisbenj  is  not,  in  our 
opinion,  the  sensitive  root  of  the  facial,  whose  fibres  we  only  look  tipon  as 
motor ;  it  is  not  even  that  of  the  great  superficial  petrous  nerve,  of  which  it 
might  at  rtie  most  be  considered  as  only  an  accessory  filament.  In  the  Horse, 
this  ramuscnle  is  extremely  attenuated,  and  can  scarcely,  if  at  all,  be  dis- 
tinguished at  its  origin  from  the  filaments  of  the  lateral  root  of  the  auditory 
nerve ;  it  is  seen  to  enter  the  aqueduct  of  Fallopius,  and  divide  on  the  bend 
(or  gangliform  enlargement)  of  the  facial  nerve  into  several  gradually 
diminishing  filaments,  which  are  confounded  with  the  proper  fibres  of  this 
nerve,  or  the  ganglion  geniculare. 

What  a  difference  there  is  between  this  arrangement  and  that  of  the 
veritable  sensitive  roots  opposite  the  ganglia  placed  on  their  track  !  Why 
hesitate  to  admit  that  this  nerve  of  Wrisherg  is  on  y  an  anastomosing  twig 
passing  from  the  auditory  nerve  to  the  facial  ?  Is  it  because  of  the  radical 
difference  in  the  properties  of  the  two  nerves  ?  Nature,  in  bringing  them  so 
closely  together,  does  not  appear  to  have  taken  into  account  this  difference ; 
and  the  reason  for  this  anastomosis  might  be  explained  by  the  connections 
the  seventh  pair  maintains  with  the  active  portions  of  the  auditory  apparatus. 

Is  it  not  the  facial  nerve  that  animates  the  stapedius  muscle,  and,  in  an 
indirect  manner,  that  of  the  malleus  ?  Are  all  the  muscles  of  the  external  ear 
not  under  its  influence  ?    In  the  present  state  of  science  it  would  be  difiicult 


724  TEE  NERVES, 

to  discover  tlio  functional  relationship  that  may  exist  between  the  con- 
nectious  of  the  ear  with  the  facial,  and  those  of  the  latter  nerve  with  the 
auditory :  but  the  mind  perceives  this  relationship,  and  that  ought  to  suffice. 

The  opinion  which  regards  the  nerve  of  Wrisberg  as  the  sensitive  root 
of  the  facial  has,  we  believe,  been  more  particulary  accredited  by  the  appa- 
rent impossibility  of  otherwise  accounting  for  the  sensibility  this  nerve 
possesses,  even  at  its  exit  from  the  stylo-mastoid  foramen — that  is,  before 
contracting  any  anastomosis  with  the  fifth  pair ;  but  this  sensibility  belongs 
exclusively  to  the  fibres  of  the  communicating  branch  sent  by  the  pneumo- 
gastric  nerve,  and  not  to  the  fasciculi  of  the  facial,  as  is  proved  by  stimu- 
lating the  latter  outside  the  aqueduct  of  Fallopius,  after  destroying  the 
pneumogastric  at  its  origin.  If  it  is  sought  to  regard  the  intermediate 
nerve  absolutely  as  a  branch  distinct  from  the  original  filaments  of  the 
auditory,  and  if  it  be  determined  to  make  it  a  sensitive  nerve,  then  it  must 
at  least  be  admitted  that  it  does  not  carry  its  sensibility  beyond  the  stylo- 
mastoid foramen,  and  that  all  its  filaments  disaj^jiear  in  the  ramuscules 
furnished  by  the  facial  in  its  interosseous  course.  Otherwise,  it  is  known 
that  M.  Longet  considers  this  nerve  as  forming  the  small  superficial  petrous 
branch  and  the  nervous  filament  of  the  stapedius  muscle :  but  he  makes  it  a 
motor  branch  destined  to  supply  the  muscles  of  the  middle  ear.  His  idea  is 
very  ingenious,  and  would  assuredly  be  feasible  if  it  were  possible  to  follow 
the  intermediate  nerve  from  its  origin  to  the  lateral  column  of  the  medulla 
oblongata  ;  but,  unfortunately,  this  is  not  the  case,  as  the  small  ramuscule 
only  appears  to  be  an  offshoot  of  the  fibres  proper  to  the  auditory  nerve. 

To  sum  up,  the  great  superficial  petrous  nerve  jDroceeds  from  the  facial 
by  two  roots :  one  motor,  the  other  sensitive,  assimilable,  to  a  certain  point, 
to  the  roots  of  the  spinal  nerves.  The  first  is  furnished  by  the  filaments  of 
the  seventli  pair ;  while  the  second  probably  comes  from  the  pneumogastric 
nerve,  and  has  annexed  to  it  on  its  course  the  ganglion  geniculare.  The  nerve 
of  Wrisberg  perhaps  concurs  in,  the  formation  of  this  ganglion,  but  it  is 
certainly  not  its  principal  source. 

Course  and  Terynination. — The  great  petrous  nerve,  after  being  detached 
from  the  facial,  and  forming  with  it  an  obtuse  angle  oldening  outwards, 
enters  the  hiatus  (or  aqueduct)  of  Fallopius — a  small  jjassage  running  from 
behind  forward,  in  the  substance  of  the  petrous  bone,  above  the  fenestra, 
rotunda,  and  cochlea.  Arriving  at  the  interior  of  the  cavernous  sinus, 
which  it  travei'ses,  immersed  in  the  blood  that  sinus  contains,  it  receives  a 
branch  from  the  ganglionic  plexus  there,  is  lodged  in  the  Videan  fissure,  then 
in  the  Videan  canal,  and  in  this  manner  gains  the  orbital  hiatus,  where  it 
separates  into  several  branches — most  frequently  two — which  join  the 
posterior  part  of  Meckel's  ganglion.  It  constitutes  the  motor  root  and 
sympathetic  filament  of  that  ganglion. 

2.  Small  Superficial  Petrous  Nerve. — A  very  thin  filament  detached 
from  the  facial  to  the  outside  of  the  preceding,  and  likewise  traversing  the 
petrous  bone  from  behind  to  before  to  enter  the  otic  ganglion,  whose  motor 
root  it  is. 

3.  Filament  of  the  Stapedius  Muscle  (Tympanic). —  The  facial 
nerve,  in  its  passage  above  and  in  front  of  the  stapedius  muscle,  closely 
adheres  to  it,  and  gives  it  one,  perhaps  several,  extremely  short  filaments. 

4.  Chorda  Tympani  (Fig.  342,  6). — This  filament,  also  named  the 
tympano-lingaal  nerve,  arises  at  a  very  obtuse  angle  from  the  facial,  near  the 
external  orifice  of  the  aqueductus  Fallopii,  It  penetrates  the  cavity  of  the 
tympanum    by   a   particular   oj)ening,   courses    from    its   posterior   to  its 


TEE  CBANIAL  OR  ENCEPHALIC  NERVES.  725 

anterior  wall  in  describing  a  curve  downwards,  and  passes  among  the 
chain  of  auditory  bones,  between  the  handle  of  the  malleus  and  long  branch 
of  the  incus.  Escaping  from  the  middle  ear  by  a  canal  (Jissura  Glaseri)  on  the 
limits  of  the  mastoid  and  petrous  portions  of  the  temporal  bone,  it  proceeds 
forwards  and  downwards,  and  finally  joins  the  gustatory  nerve  aftet  a  short 
course  beneath  the  external  pterygoid  muscle,  outside  the  guttural  pouch. 

5.  Anastomosing  Branch  of  the  Pneumogasteio  Neeve. — [See  the 
description  of  the  tenth  pair.) 

6.  Occipito-Sttloid  Neuve.     (Fig.  336,  3.) 

7.  Stylo-hyoid  Nerve. 

8.  Digastric  Nerve  (Fig.  336,  4).  —  These  three  spring  from  a 
common  fasciculus  at  the  stylo-mastoid  foramen,  and  ramify  in  their 
respective  muscles,  after  a  certain  course  beneath  the  pai'otid  gland. 

9.  Cervical  Branch  (Figs.  336,  6).— This  nerve  has  its  origin  almost 
in  the  middle  of  the  subj)arotideal  portion  of  tlie  facial,  near  a  particular  loop 
thrown  by  that  nerve  around  the  posterior  auricular  artery,  and  often  from 
this  loop  itself. 

It  afterwards  traverses  the  parotid  gland  from  within  to  without,  and 
above  to  below,  to  descend  at  first  on  its  external  face,  beneath  the  parotido- 
auricularis  muscle,  then  into  the  jugular  channel,  where  it  is  lodged  below  the 
deep  face,  or  in  the  substance  of  the  subcutaneous  muscle  of  the  neck,  which 
receives  its  terminal  divisions  near  the  anterior  appendix  of  the  sternum. 

In  its  course  this  nerve  communicates  with  the  inferior  branches  of  the 
second,  third,  fourth,  fifth,  and  sixth  cervical  pairs  by  branches  from  them ; 
it  sends  numerous  collateral  filaments  into  the  texture  of  the  subcutaneous 
muscle. 

10.  Filaments  of  the  Guttural  Pouch  and  Parotid  Gland. — 
Eemarkable  for  their  number  and  tenuity,  these  filaments  do  not  otherwise 
deserve  particular  mention. 

11.  Posterior  Auricular  Nerve  (Fig.  336,  2). — It  commences  at 
the  stylo-mastoid  foramen,  is  directed  upwards  beneath  the  parotid  gland, 
accompanying  the  jiosterior  auricular  artery,  and  is  distributed  to  the 
posterior  muscles  of  the  external  ear.  It  sometimes  offers  at  its  origin  a 
loop  analogous  to  that  embracing  the  posterior  auricular  artery. 

12.  Middle  Auricular  Nerve. — Most  frequently  this  arise  from  the 
same  point  as  the  preceding  nerve — it  might  be  said  in  common  with  it — 
ascends  towards  the  base  of  the  concha  in  traversing  the  j)arotid  gland,  and 
pierces  the  cartilage  to  supply  the  interconchal  integument  and  the  con- 
tractile fibres  which  cover  its  adherent  face  in  some  parts. 

13.  Anterior  Auricular  Nerve  (Fig.  336,  5). — This  is  the  largest 
of  the  three  auricular  nerves.  After  being  detached  from  the  facial  nerve, 
opposite  the  cervical  branch,  and  after  ascending  across  the  parotideal 
tissue,  it  gains  the  external  face  of  the  zygomatic  process,  where  it  meets 
the  superficial  divisions  of  the  lachrymal  nerve ;  it  continues  forward 
beneath  the  external  parieto-auricular  muscle,  reaches  the  base  of  the  orbital 
process  at  the  supra-orbital  foramen,  there  crossing  the  terminal  branches  of 
the  nerve  of  that  name ;  it  then  descends  vertically  within  the  orbit  to  below 
the  nasal  angle  of  the  eye.  where  it  mixes  with  the  superficial  divisions  of 
the  palpebro -nasal  nerve,  and  finally  terminates  on  the  face  in  the  lachrymal 
and  supernaso-labialis  muscles. 

In    its    progress,  it    gives   off  numerous   ramuscules   to   the   anterior 
muscles  of  the  ear,  the  fronto-supra-orbital,  and  the  orbicularis  of  the  eye- 
lids, whose  contractibility  it  excites. 
49 


726  TEE  NERVES. 

This  nerve  is  remarkable  for  the  relations  it  maintains  with  the  terminal 
ramnscules  of  the  three  branches  of  the  ophthalmic  nerve,  or  fifth  pair. 
Although  there  do  not  exist  any  real  anastomoses  between  it  and  these 
various  branches,  it  is  customary  to  designate  the  reticular  mass  they  form 
in  front  of  the  ear  and  on  the  side  of  the  face,  as  the  anterior  auricular  plexus. 

Terminal  Branches  of  the  Facial  Nerve  or  Subztgomatic  Plexus 
(Fig.  110,  11.  12). — The  facial  nerve,  as  we  have  seen,  terminates  in  several 
branches,  usually  two,  on  arriving  beneath  the  temporo-maxillary  articula- 
tion, where  they  join  the  superficial  temporal  nerve.  After  becoming  sensory- 
motor,  they  are  continued  on  the  external  face  of  the  masseter,  covered  by 
the  subcutaneous  muscle  of  the  head,  to  which  they  give  some  ramuscules, 
and  are  united  to  each  other  by  anastomosing  branches  of  variable  disposi- 
tion, which  we  need  not  stay  to  examine.  It  is  always  observed  with  regard 
to  this  arrangement,  that  the  branches  of  the  subzygomatic  plexus,  on 
arriving  near  the  anterior  border  of  the  masseter,  are  divided  into  a  series  of 
divergent  ramuscules  which  pass  to  the  surface  of  the  vascular  or  glandular 
canals  situated  in  front  of  the  masseter,  to  enter  the  tissues  of  the  lips, 
cheeks,  and  nostrils. 

Among  these  ramuscules,  the  superior  is  remarkable  for  its  great  volume  ; 
it  passes  beneath  the  zygomato-labialis  muscle,  lies  close  to  the  inferior 
border  of  the  supermaxillo-nasalis  magnus,  beside  the  superior  coronary 
artery,  and  afterwards  runs  below  the  supernaso-labialis  muscle,  where  it  joins 
the  terminal  ramuscules  of  the  superior  maxillary  nerve,  with  which  it  is 
distributed  to  the  textures  of  the  upper  lip  and  alseof  the  nose  (Fig.  336,  7'). 

A  second  ramuscule — the  inferior,  smaller  than  the  preceding— follows 
the  inner  aspect  of  the  maxillo-labialis  muscle,  to  mix  by  its  anterior  extremity 
with  the  terminal  fasciculus  of  the  inferior  maxillary  nerve,  and  ramify, 
with  the  proper  filaments  of  that  fasciculus,  in  the  tissue  of  the  lower  lip. 

Between  these  two  principal  branches  is  a  series  of  smaller  ramifications 
destined  to  the  alveolo-labialis  muscle.  Among  these  are  some  which 
become  inflected  on  the  inner  face  of  the  masseter,  and  reach  the  deep 
portion  of  the  buccinator,  where  they  anastomose  with  the  filaments  of  the 
buccal  nerve.  Other  ramuscules,  situated  below  the  principal  inferior 
branch,  are  expended  in  the  subcutaneous  muscle  of  the  face ;  one  of  them, 
after  bending  round  the  lower  border  of  the  inferior  maxilla,  reaches  the 
intermaxillary  space. 

Functions  of  the  Facial  Nerve. — This  nerve  excites  the  contractility 
of  the  muscles  of  the  middle  ear,  external  ear,  the  cheeks,  lips,  nostrils, 
orbicularis  of  the  eyelids,  and  the  cervico-facial  subcutaneous  muscle.  By 
its  great  superficial  petrous  filament,  it  influences  the  movements  of  the 
muscles  of  the  soft  palate,  and  it  is  admitted,  as  already  noticed  when  speak- 
ing of  the  gustatory  nerve,  that  its  tympano-lingual  ramuscule  acts  as  an 
excitant  to  the  submucous  muscular  layer  of  the  tongue.  The  facial  nerve, 
also,  without  doubt,  exercises  its  influence  on  the  parotid  gland ;  thus  its 
action  in  this  respect  is  not  well  determined ;  perliaps  it  is  limited  to  pro- 
ducing the  contractions  of  the  excretory  canaliculi  which  escape  from  the 
lobes  of  the  gland. 

It  is  to  be  remarked  that  the  facial  nerve  has  no  influence  over  the 
masseter  muscle  ;  notwithstanding  their  intimate  relations,  it  does  not  detach 
the  smallest  filament  to  it. 

It  is  necessary  to  say,  that  its  anastomoses  with  the  various  branches  of 
the  trigeminus  and  pneumogastric  nerves,  while  endowing  its  distributive 
ramuscules  with  great  sensibility,  in  no  respect  modify  its  mode  of  action 


THE  CRANIAL  OR  ENCEFHALIC  NERVES.  727 

or  its  properties,  because,  notwithstanding  these  anastomoses,  its  proper 
fibres  preserve  their  complete  independence. 

8.  Eighth  Pair,  or  Auditory  Nerves.    (Figs.  324,  338.) 

This  is  the  nerve  of  hearing,  and  affects  a  very  simple  disposition,  whicli 
we  will  sum  up  in  a  few  words. 

Origin. — The  auditory  nerve  (portio  mollis)  proceeds  from  the  medulla 
oblougata  by  two  roots,  an  anterior  or  lateral,  and  a  posterior.  The  latter 
(Fig.  323,  20)  commences  on  the  floor  of  the  fourth  ventricle  by  some 
convergent  striae  (linece  transversce,  strice  medullar es),  as  is  admitted  in  the 
majority  of  treatises  on  human  anatomy,  thougli  we  have  never  been  able  to 
discover  these  striae  in  the  domesticated  animals ;  it  is  afterwards  directed 
outwards  in  winding  round  the  posterior  cerebellar  peduncle,  and  unites  with 
tlie  anterior  root  on  the  side  of  the  medulla  oblongata.  'I'he  latter  root 
(Fig.  338,  g),  consists  of  a  single  fasciculus  joined  with  that  of  the  facial, 
and  escapes  from  between  the  fibres  of  the  corpus  restiforme.  Tlie  nucleus 
of  the  auditory  nerve  has  been  discovered  by  Schrceder  Yan  der  Kolk,  a 
little  below  that  of  the  facial  nerve. 

Course  and  Termination.—These  two  roots  immediately  unite  into  a 
single  scft  cord  situated  behind  that  of  the  seventh  pair,  witli  which  it  is 
directed  outwards  to  reach  the  internal  auditory  hiatus  (or  meatus.)  There 
it  divides  into  two  branches — an  anterior  and  posterior,  whose  fasciculi 
traverse  the  foramina  at  the  bottom  of  that  liiatus :  the  former  to  gain  the 
axis  of  the  cochlea  (the  cochlear  branch),  and  the  latter  the  semicircular 
canals  (vestibular  branch.)  The  description  of  these  two  branches  will  be 
deferred  till  we  come  to  the  sense  of  hearing. 

9.  Ninth  Pair,  or  Glosso-Pharyngeal  Nerves.     (Figs.  338,  3  ;  342,  10.) 

The  glosso-pharyngeal  is  a  mixed  nerve,  which  carries  general  sensation, 
■with  gustative  sensibility,  into  the  posterior  third  of  the  tongue,  and  excites 
(  outraction  of  the  pharyngeal  muscles. 

Origin. — This  nerve  originates  on  the  side  of  the  medulla  oblongata, 
behind  the  eighth  pair,  by  eight  or  ten  fine  roots,  some  of  which  are 
implanted  in  the  corpus  restiforme,  wdiile  the  others,  the  smallest  number, 
escape,  like  the  filaments  of  the  facial  nerve,  from  the  interstice  between 
that  body  and  the  lateral  column  of  the  medulla  oblongata.^  These  roots 
soon  unite  in  a  single  cord,  which  issues  from  the  cranium  by  a  particular 
orifice  in  the  posterior  foramen  lacerum,  and  at  this  point  exhibits  a  grey 
oval-shaped  enlargement— the  ganglion  pelrosum  ov  ganglion  of  Andersch,  in 
which  it  is  somewhat  difficult  to  distinguish  the  motor  filaments  of  the 
nerve  from  those  w-hich  arise  between  the  lateral  and  superior  columns  of  the 
medulla  oblongata  (Fig.  338,  2). 

Course  and  Termination. — Scarcely  has  the  glosso-pharyngeal  nerve 
escaped  from  the  cranium,  before  it  descends,  in  describing  a  curve  whose 
concavity  looks  forward,  behind  the  large  branch  of  the  os  hyoides,  included 
at  first  between  a  fold  of  the  guttural  pouch,  then  between  the  latter  and 

'  This  disposition,  which  is  rearlily  exposed  in  the  Horse,  appears  to  ns  sufficient  to 
remove  all  the  doubts  existing  in  the  minds  of  a  larjje  number  of  anatomists,  as  to  the 
nature  of  the  glosso-pharyngeal  nerve.  It  evidently  possesses  at  its  origin,  as  motor 
filaments,  those  arising;  from  the  same  part  as  the  facial  nerve,  and  as  sensitive  filaments 
thise  from  tlie  corpus  restiforme.  Besides,  we  may  object  to  the  opinion  which  would 
also  attriliute  the  motor  property  of  the  glosso-pharyngeal  nerve  to  the  anastomosing 
bianche.-  passing  betwf-en  it  and  tlie  seventh  pair,  on  "the  ground  that  thf  se  anastomosea 
are  far  from  being  constant,  and  that  in  tome  species  they  are  always  totally  absent. 


728  THE  NERVES. 

the  internal  pterygoid  muscle.  Lying  beside  the  external  maxillary 
artery  in  the  latter  part  of  its  course,  it  passes  with  it  along  the  posterior 
border  'of  the  large  branch  of  the  hyoid  bone,  and  gains  the  base  of  the 
tongue  with  the  lingual  artery,  by  coursing  beneath  the  hyo-glossus  brevis 
muscle.  The  papillaa  on  the  posterior  portion  of  the  lingual  mucus  mem- 
brane receive  the  terminal  ramuscules  of  this  nerve.  {See  the  Sense  of  Taste.) 
Collateral  Branches. — On  its  course  it  furnishes  : 

1.  Jacohsoris  nerve  (tympanic  branch),  a  very  thin  filament  springing  from 
Andersch's  ganglion,  proceeding  upwards,  and  entering  a  particular  foramen 
in  the  tuberous  portion  of  the  temporal  bone,  to  be  distributed  more 
especially  to  the  tympanum,  sending  also  to  the  superficial  petrous  nerves 
two  branches  which  are  designated  the  deep  great  and  small  petrous  nerves. 

2.  Filaments  of  communication  with  the  superior  cervical  ganglion,  two 
or  three  in  number,  though  sometimes  replaced  by  a  single  ramuscule. 

3.  A  branch  to  the  carotid  plexus,  which  passes  back  on  the  guttural 
pouch  to  reach  the  terminal  extremity  of  the  common  carotid,  whence  its 
filaments  are  sent,  with  those  of  the  sympathetic  nerve,  either  to  the  external 
carotid,  occipital,  or  even  to  the  common  carotid  artery  itself.  This  branch 
communicates,  by  several  anastomoses,  with  the  numerous  sympathetic 
branches  which  pass  from  the  superior  cervical  ganglion  to  the  surface  of 
the  guttural  pouch,  and  which  are  either  expended  in  that  membrane,  or 
join  the  posterior  border  of  the  great  hypoglossal  nerve. 

4.  A  pharyngeal  branch  (Fig.  342,  11),  which  is  generally  detached  close 
to  the  pharyngeal  artery,  and  forms,  along  with  the  pharyngeal  filaments  of 
the  pneumogastric  nerve,  a  remarkably  intricate  plexus  (pharyngecd)  on  the 
upper  wall  of  the  pharynx,  below  the  guttural  pouch.  This  plexus  receives 
a  filament  from  the  hypoglossal  nerve. 

10.  Tenth  Pair,  Vagus,  or  Pneumogastric  Nerves.     (Figs.  338,  342,  362.) 

The  pneumogastric  nerve  is  as  remarkable  for  its  extent,  as  for  the 
multiplicity  of  physiological  uses  imposed  upon  it. 

It  is  prolonged  to  beyond  the  stomach,  after  distributing  to  that  viscus, 
the  oesophagus,  pharynx,  lung,  bronchi,  trachea,  and  larynx  a  large  number 
of  filaments  on  which  depend  the  movements,  secretory  functions,  and 
purely  sensory  phenomena  of  which  all  these  organs  are  the  seat. 

Origin. — The  pneumogastric  is  a  mixed  nerve,  and  consequently  arises 
from  two  kinds  of  roots ;  these  we  will  successively  describe  before  passing 
to  its  distribution,  though  it  must  be  remarked  that  this  subject  has  not  yet 
been  fully  determined. 

Sensitive  roots. — These  arise  from  a  nucleus  of  grey  substance  situated 
near  the  floor  of  the  fourth  ventricle,  a  little  behind  the  glosso-pharyngeal 
nucleus,  and  in  which  the  fibres  of  the  antero-lateral  columns  of  the  medulla 
oblongata,  or  respiratory  track  of  Bell,  seem  to  be  lost.  In  leaving  the 
medulla,  they  form  from  four  to  ten  bundles,  which  describe  a  slight  curve 
whose  convexity  is  upwards ;  the  highest  median  fibres  correspond  to  the 
groove  that  limits,  superiorly,  the  respiratory  tract,  the  posterior  and  ante- 
rior fibres  bending  down  to  the  pyramids — the  second  more  than  the  first. 

These  roots  proceed  transversely  outwards,  mixed  with  connective  tissue 
and  some  fine  muscular  ramifications,  and  leave  the  cranium  by  one  of  the 
openings  (jugular  foramen)  in  the  posterior  foramen  lacerum,  uniting  in 
their  passage  through  that  aperture  in  a  somewhat  voluminous  ganglion, 
called  in  Man  the  jugular  ganglion. 


THE  CRANIAL  OR  ENCEPHALIC  NERVES.  729 

Motor  roots. — Several  anatomists  and  physiologists  consider  these  as  a 
portion  of  the  accessory  nerve  of  Willis,  and  give  them  the  name  of  internal 
or  bulbous  root  of  the  spinal  nerve.  They  are  situated  a  little  behind  the  pre- 
ceding, and  emanate  from  the  respiratory  tract ;  consequently  they  are  not 
so  elevated  as  the  whole  of  the  sensitive  fibres.  They  are  separated  from 
the  sensitive  roots  by  a  comparatively  large  vein,  and  are  distinguished  from 
them  by  their  anastomotic  tendency.  Becoming  longer  as  they  are  more 
posterior,  and  frequently  anastomosing  with  each  other,  the  filaments 
forming  these  motor  roots  converge,  and  gain  the  posterior  foramen  lacerum  ; 
this  they  pass  through  by  one  or  two  special  openings  to  join  the  jugular 
ganglion,  beneath  and  behind  which  we  find  them  applied.  A  certain 
number  of  the  most  posterior  of  these  filaments  lie  beside  the  medullary 
root  of  the  spinal  nerve ;  but  they  are  soon  detached  to  pass  with  the 
others  to  the  jugular  ganglion. 

Jitgular  or  Ehrenritters  ganglion. —  Elongated  from  before  to  behind, 
and  flattened  on  both  sides,  the  jugular  ganglion  is  embedded  in  the 
cartilaginous  substance  that  fills  the  foramen  lacerum.  When  it  has  been 
macerated  for  some  time  in  dilute  nitric  acid,  it  may  be  resolved  into  two 
portions  :  one  corresponding  to  the  sensitive,  the  other  to  the  motor  roots. 
Some  white  nervous  filaments  appear  to  pass  to  its  surface  without  becoming 
confounded  with  it.  It  is  in  relation,  in  front,  with  the  ganglion  of  An- 
dersch  ;  behind,  it  crosses  somewhat  obliquely  the  medullary  root  of  the 
spinal  nerve. 

The  jugular  ganglion  is  also  in  relation  with  the  spinal,  glosso -pharyn- 
geal, and  facial  nerve.  It  communicates  with  the"  external  root  of  the  spinal 
nerve  by  the  few  radicular  filaments  indicated  above.  With  the  glosso- 
pharyngeal it  is  connected  by:  1,  An  afterent  filament  coming  from  the 
highest  roots  of  the  ninth  pair,  and  which  meets  it  at  its  antero-internal 
angle ;  2,  By  an  efferent  branch  it  sends  to  the  ganglion  of  Andersch. 
Lastly,  it  is  imited  to  the  facial  by  a  branch  we  have  named  the  anasto- 
mosing branch  extending  from  tJie  pneumogastric  to  the  facial  nerve. 

This  anastomotic  branch,  on  leaving  the  jugular  ganglion,  is  somewhat 
considerable  in  volume,  and  it  has  appeared  to  us  that,  at  times,  among  its 
radicles  there  were  some  in  direct  continuity  with  the  sensitive  roots  of  the 
pneumogastric  nerve.  This  branch  is  directed  forward,  above  the  ganglion 
of  Andersch,  crosses  Jacobson's  branch,  traverses  the  tuberous  portion  of 
the  temporal  bone,  and  arrives  in  the  aqueduct  of  Fallopius ;  here  it  meets 
the  facial  nerve,  at  the  point  where  the  latter  gives  off  the  chorda  tympani. 
A  small  number  of  its  fibres  then  lie  beside  the  nerve  of  the  seventh  pair 
in  ascending  towards  the  origin  of  that  nerve,  where,  in  our  opinion,  they 
constitute  a  large  portion  of  the  great  petrous  nerve — that  which  has  at 
its  origin  the  geniculated  ganglion.  Other  fibres  descend,  on  the  contrary, 
in  following  the  proper  fibres  of  the  facial  nerve,  and  are  lost  among  these ; 
but  the  largest  number  cross  that  nerve  and  continue  their  course  in  the 
substance  of  the  temporal  muscle,  to  be  chiefly  distributed  to  the  membrane 
lining  the  internal  auditory  canal. 

Course  and  Relations. — Beyond  the  jugular  ganglion,  the  trunk  of  the 
pneumogastric  remains  intimately  allied  with  the  spinal  accessory  for  about 
8-lOths  of  an  inch ;  at  this  point  we  have  been  unable  to  find  the  gan- 
gliform  plexus  described  in  Man,  though,  according  to  M,  Bernard,  it  exists  in 
the  Rabbit.  The  two  nerves  then  separate  to  allow  the  great  hypoglossal  nerve 
to  pass  between  them  ;  after  which  the  pneumogastric  nerve  descends  alone 
behind  the  guttural  pouch,  in  proximity  to  the  superior  cervical  ganglion. 


730 


THE  NERVES. 


Near  the  origin  of  the  occipital  artery  it  crosses  to  the  inner  side  of 
that  vessel,  and  beyond  this  is  joined  in  the  most  intimate  manner  to  the 
cervical  portion  of  the  sympathetic  chain ;  the  single  cord  resulting  from 
this  fusion  follows  the  common  carotid  artery,  above  which  it  is  situated, 
to  near  the  entrance  of  the  thorax.  The  two  nerves  then  resume  their 
reciprocal  independence,  the  pneumogastric  penetrating  the  thorax  a  little 

Ficr.  338. 


ORIGIN  OF  THE  NKRVES  SPRINGING  FROM  THE  MEDULLA  OBLONGATA,  AND  PAR- 
TICULARLY THAT  OF  THE  PNEUMOGASTRIC,  SPINAL,  HYPOGLOSSAL,  AND  GLOSSO- 
PHARYNGEAL. 

a,  Medulla  oblongata ;  &,  Pyramids ;  c.  Enlargement  simulating  the  olivary  body ; 
d,  Lateral  posteriov  fissure ;  e,  Fissure  limiting  superiorly  the  respiratory  tract 
of  Ch.  Bell ;  /,  Corpus  restiforme  ;  g,  Auditory  nerve ;  h,  External  oculo-motor  ; 
i,  Trigeminus;  j,  Arciform  fibres  of  the  medulla  oblongata. — 1,  Pneumogastric; 
2,  Spinal,  inner  root;  3,  Glosso-pharyngeal ;  4,  Spinal,  medullary  column;  5, 
Inferior,  or  anterior,  root  of  the  great  hypoglossal ;  5',  Its  ganglionic  root ;  6, 
Facial ;  7,  Jugular  ganglion  ;  8,  Anastomosis  of  the  pneumogastric  with  the 
facial ;  9,  Eamuscule  from  the  external  branch  of  the  spinal  passing  to  the  pneu- 
mogastric.— From  Toussaint's  Thesis  on  the  '  Anatomic  Compare'e  du  Nerf 
Pneumogastrique.'     Lyons,  1869. 

below  the  sympathetic,  in  passing  among  the  lymphatic  glands  existing 
between  the  two  first  ribs. 

In  this  course,  the  two  pneumogastrics  affect  nearly  the  same  relations; 
though  there  is  something  special  connected  with  the  left,  which  corres- 
ponds with  the  oesophagus  towards  the  lower  part  of  the  neck. 

Within  the  chest,   however,   these   two   nerves   comport   themselves  a 


THE  CRANIAL  OR  ENCEPHALIC  NERVES. 

Fig.  339. 


731 


PNEUMOGASTRIC    NERVE,    WITH    ITS    BRANCHES    IN    THE    UPPER    PART    OF   THE    NECK. 

a,  ffisophagus ;  6,  Trachea ;  c,  Common  carotid ;  d,  Internal  maxillary  artery ;  e, 
Glosso-facial  artery  ;  1,  1,  Pneumogastric  nerve ;  2,  Spinal  accessory ;  3,  Glosso- 


732 


Fig.  340. 


.   TEE  NERVES. 

little  diflferently.  The  right  passes  round  the  axil- 
lary artery  very  obliquely,  upwards,  outwards,  and 
backwards  beneath  the  mediastinal  pleura,  to  follow 
the  external  face  of  the  trachea  to  above  the  origin 
of  the  bronchi,  where  this  nerve  terminates.  The 
left  also  passes  below  the  brachial  trunk  ;  but 
instead  of  turning  round  the  trachea,  it  merely 
lies  beside  that  tube,  and  reaches  the  root  of  the 
lung,  after  crossing,  outwardly,  the  origin  of  the 
two  aortse. 

When  these  nerves  arrive  above  the  bifurca- 
tion of  the  trachea,  they  terminate  by  forming 
the  bronchial  plexus  and  oesophageal  nerves — -the 
latter  being  prolonged  to  the  stomach  and  the 
solar  plexus. 

Beneath  the  jugular  ganglion,  but  in  the  upper 
part  of  the  neck,  the  pneumogastric  receives  fila- 
ments from  the  spinal  accessory,  ganglion  of 
Andersch,  sympathetic,  hypoglossal,  and  the  two 
first  cervical.  These  different  nerves  cross  each 
other  in  a  very  complex  manner  on  the  surface 
of  the  guttural  pouch,  the  pharynx,  and  divisions 
of  the  carotids,  and  form  the  guttural,  pharyngeal, 
and  carotid  plexuses. 

Distribution. — The  branches  furnished  by  the 
pneumogastric  on  its  course  are  : 

1.  Communicating  filaments   with   the 
cervical  ganglion. 

2.  Pharyngeal  branch. 

3.  Superior  laryngeal  nerve. 

4.  Communicating  filaments  with  the  inferior 
cervical  ganglion. 

5.  Inferior  laryngeal  nerve. 

We  will  pass  in  review  these  collateral  divisions 
before  studying  the  terminal  branches,  which  are : 

1 .  Those  forming  the  honchial  plexus. 

2.  Those  constituting  the  oesophageal  nerves. 

ORIGIN  AND  DISTRIBUTION  OP  ^5  3>  4,  Medulla  oblongata  ;  1,  Corpus  pyramidale  of  one 
THE  EIGHTH  PAIR  OF  ^ide ;  2,  Pons  Varolii ;  3,  Corpus  olivare ;  4,  Corpus 
NERVES  IN  MAN.  restiforme ;    5,   Facial    nerve ;    6,   Origin    of    glosso- 

pharyngeal nerve  ;  7,  Ganglion  of  Andersch  ;  8,  Trunk 
of  the  nerve;  9,  Spinal  accessory  ;  10,  Ganglion  of  pneumogastric ;  11,  Its  plexiform 
ganglion;  12,  Its  trunk ;  13,  Its  pharyngeal  branch,  forming  the  pharyngeal  plexus, 
14,  assisted  by  a  branch  from  the  glosso-pharyngeal,  8,  and  one  from  the  superior 
laryngeal,  15 ;  16,  Cardiac  branches;  17,  Recurrent  laryngeal  branch;  18,  Anterior 
pulmonary  branches ;  19,  Posterior  pulmonary  branches ;  20,  (Esophageal  plexus ; 
21,  Gastric  branches;  22,  Origin  of  the  spinal  accessory  nerve;  23,  Its  branches  dis- 
tributed to  the  sterno-masillaris  and  mastoido-humeralis ;  24,  Its  branches  to  the 
trapezius  muscle. 

pharyngeal  nerve ;  4,  Great  hypoglossal  nerve  ;  5,  Supei-ior  cervical  ganglion  of  the 
eympathetic  ;  6,  Pharyngeal  nerve ;  7,  Superior  laryngeal ;  8,  External  laryngeal ; 
9,  Inferior  laryngeal;  10,  Cord  of  the  pneumogastric  and  sympathetic;  11,  First 
cervical  nerve,  with  the  loop  it  sends  to  the  hypoglossus. — From  Toussaint's  work. 


superior 


THE  CRANIAL  OR  ENCEPHALIC  NERVES.  733 

Collateral  Branches  op  the  Pneumogastric  Nerve. — 1.  Filaments 
OB  THE  Inferior  Cervical  Ganglion. — Always  very  slender,  these  some- 
times come  from  the  pharyngeal  ramuscule. 

2.  Pharyngeal  Nerve  (Figs.  339,  6 ;  342,  15).— Originating  from  the 
pneumogastric  nerve  at  the  middle  part  of  the  superior  cervical  ganglion, 
the  pharyngeal  passes  forwards  and  downwards  on  the  side  of  the  guttural 
pouch,  and  gains  the  upper  face  of  the  pharynx,  where  it  terminates  in 
forming  a  plexus  with  the  pharyngeal  branch  of  the  ninth  pair.  This  is  a 
sensory-motor  branch.  It  gives  off  a  large  division  that  passes  backwards 
to  the  surface  of  the  middle  and  posterior  constrictor  muscles,  to  which  it 
gives  branches,  and,  throwing  off  a  filament  to  the  external  laryngeal  nerve, 
reaches  the  commencement  of  the  oesophagus ;  it  descends  on  the  outside 
of  that  canal  by  becoming  distributed  in  its  muscular  tunic.  This  division, 
■which  we  have  named  the  oesophageal  branch  of  the  pharyngeal  nerve,  may 
be  traced  on  the  oesophagus  to  the  lower  part  of  the  neck,  and  in  some 
subjects  even  into  the  thoracic  cavity. 

3.  Superior  Laryngeal  Nerve  (Fig.  339,  7). — More  voluminous 
than  the  preceding,  and  arising  a  little  lower,  this  nerve  follows  an 
analogous  course  to  reach  the  side  of  the  larynx,  where  it  enters  the 
aperture  below  the  appendix  of  the  superior  border  of  the  thyroid  cartilage, 
to  be  almost  entirely  expended  in  the  laryngeal  mucous  membrane,  to 
which  it  communicates  a  very  exquisite  degree  of  sensibility. 

At  the  inner  face  of  the  thyroid  cartilage,  it  presents  several  branches 
that  are  directed  forward,  upward,  and  backward.  The  first  pass  to  the 
mucous  membrane  at  the  base  of  the  tongue  and  the  two  faces  of  the  epi- 
glottis. The  second  are  distributed  in  the  lateral  walls  of  the  pharynx. 
Of  the  third,  some  are  destined  to  the  mucous  membrane  of  the  arytenoid 
cartilages  and  that  of  the  oesophagus ;  while  others  descend  on  the  thyro- 
arytenoid and  lateral  crico-arytenoid  muscles,  to  unite  with  the  branches 
coming  from  the  recurrent,  and  form  an  anastomosis  analogous  to  the 
anastomosis  of  Galien  (Fig.  341,  5). 

Before  penetrating  the  larynx,  and  even  very  near  its  commencement, 
it  furnishes  a  motor  filament  to  the  crico-pharyngeal  and  crico-thyroid 
muscles ;  this  filament  either  arises  directly  from  the  pneumogastric  nerve, 
or,  as  is  most  frequently  the  case,  fi'om  the  pharyngeal  ramuscule ;  this  is 
the  external  laryngeal  nerve  of  anthropotomists  (Fig.  339,  8).  It  receives 
accessory  branches  from  the  superior  cervical  ganglion,  the  oesophageal 
branch,  and  the  pharyngeal  nerve,  and'  is  then  distributed  to  the  muscular 
tunic  of  the  oesophagus.  It  is  to  the  union  of  this  branch  with  the  oesopha- 
geal branch  of  the  pharyngeal  nerve,  that  we  have  given  the  name  of  superior 
oesophageal  nerves} 

4.  Communicating  Filaments  with  the  Inferior  Cervical  Ganglion. 
— These  do  not  always  directly  enter  this  ganglion,  for  when  the  middle 
cervical  ganglion  exists  they  pass  to  it.  They  are  not  similarly  disposed 
on  both  sides.  The  filaments  of  the  right  pneumogastric,  two  or  three  in 
number,  are  extremely  short,  though  voluminous.  The  left  pneumogastric 
usually  only  furnishes  a  single,  long,  thin  ramuscule,  which  is  detached  in 
the  region  of  the  neck  near  the  point  where  the  pneumogastric  commences 
to  separate  from  the  cervical  branch  of  the  sympathetic,  and  reaches  the 
inferior  cervical  ganglion  by  remaining  alongside  the  principal  nerve. 

'  Toussaint  has  seen  this  branch  leave  the  oesophagus  to  lie  beside  the  recurrent; 
but  its  filaments  always  return  to  that  canal  as  ascending  twigs. 


734 


TEE  NERVES. 


5.  Inferior  Laryngeal  Nerve  (Fig.  362,  27,  28). — Also  named  the 
recurrent,  or  tracheal  recurrent,  because  of  its  disposition.  It  begins  in  the 
thoracic  cavity  and  ascends  along  the  trachea  to  the  larjmx,  all  of  whose 
intrinsic  muscles  it  animates,  with  the  excei^ticn  of  the  crico-thyroid. 

The  two  recurrent  nerves 
Fig.  341.  are    not  quite   symmetrical 

at  their  origin.  Tliat  of  the 
right  side  is  detached  from 
the  pneumogastric  below  the 
axillary  artery,  nearly  at  the 
dorso-cervical  arterial  trunk. 
It  is  immediately  reflected 
forward  in  embracing  the 
origin  of  that  trunk,  which 
it  crosses  inwards  to  be 
placed  against  the  trachea, 
in  the  middle  of  the  prin- 
cipal cardiac  nerves,  with 
some  of  which  it  contracts 
intimate  adherences. 

On  the  left  side,  it  is 
only  when  the  pneumogas- 
tric nerve  arrives  near  the 
root  of  the  lung  that  it 
gives  off  its  recurrent.  To 
be  reflected  forward,  the 
latter  turns  from  left  to 
right  behind  the  arch  of 
the  aorta,  and  arrives  be- 
neath the  inferior  face  of 
the  ti'achea,  among  the 
cardiac  nerves,  with  which 
it    communicates    like    tlie 

DISTRIBUTION   OF   THE  NERVES  IN  THE  LARYNX   OF   THE     Tight. 

HORSE.  The   inferior    laryngeal 

a,  Base    of    the    tongue ;    6,    Epiglottis ;     c,    Arytenoid  nerves     are      in      this     way 

muscles ;  d,  Section  of  the  thyroid  cartilage   to  show  mixed    at    a   greater    or  less 

thepartsit  covers;  e,  Cricoid  cartilagejr/,  Trachea;  ^jg^^^^^^       ^^^^     ^y^^-^     ^^.^. 

^r,  (Esophagus ;    h,  Ihyro-arytenoid    muscle;  «,   Lateral  .  ,      , 

crico-arytenoid    muscle ;    j,    Posterior    crico-arytenoid  mencement.  With  those  sym- 

muscle;  k,  Arytenoid  muscle. — 1,  Superior   laryngeal  pathetic    nervoUS     branches 

nerve  ;  2,  Inferior  laryngeal ;  3,  Branches  of  the  supe-  which  Collectively  Constitute 

rior  laryngeal  passing  to  the  epiglottis  and  tongue  ;  4,  ^^^   tracheal  plexus.      They 

Branches   ot    the    superior    laryngeal    passing    to   the  ■■ .  ^             j     1, 

oesophagus ;  5,  Very  fine  multiple  anastomoses  between  ^^^    ^oon    disengaged,   now- 

the  two  laryngeals ;  6,  Tracheal   branches ;  7,  Branch  ever,    and    leave    the    chest, 

to  the  posterior  crico-arytenoid  muscle ;  a  portion  is  but    always     in    proceeding 

distributed,    through    the    muscles,    to    the  subjacent  alancr    the    inferior    face    of 

mucous  membrane ;  10,  Branch  passing  to  the  arytenoid  ,-,       P      i           .i                      j-    „ 

muscle;    11,    (Esophageal    branch    of  the    pharyngeal  the  trachea,   then   ascending 

nerve ;    it  sometimes  comes  from  the  external    laryn-  on    its  Sides,    bcloW  tue   ca- 

geal. — From  Toussaint's  work.  rotid    arteries,    which   they 

gradually  approach,  and 
finally  attain  the  larynx  in  penetrating  beneath  the  crico-pharyngeal 
muscle. 

According  to  Goubaux,  the  left  recurrent  must  be  situated  more  super- 


THE  CRANIAL  OR  ENCEPHALIC  NERVES.  735 

ficially  than  tte  right  in  the  lower  part  of  the  neck,  and  for  this  reason 
should  be  more  exposed  to  compression.  He  thus  explains  why,  in  chronic 
"  roaring  "  the  alterations  observed  are  nearly  always  in  the  left  muscles 
of  the  larynx. 

The  terminal  divisions  of  the  recurrents  are  distributed  to  the  posterior 
and  lateral  crico-arytenoid,  and  the  arytenoid  and  thyro-arytenoid  muscles, 
as  well  as  to  the  subglottic  mucous  membrane. 

In  their  long  course,  they  emit  collateral  ramuscules  that  also  ascend, 
and  are  distributed  to  the  mucous  membrane  and  muscular  layer  of  the 
trachea,  as  well  as  to  that  of  the  oesophagus. 

The  recurrent  oesophageal  ramuscules  are  all  sensitive,  and  form  five 
groups :  the  first  and  second  arise,  on  the  left  side,  close  to  the  arch  of  the 
aorta,  ascend  on  the  sides  of  the  trachea,  and  pass  to  the  portion  of  the 
oesophagus  lying  between  that  canal  and  the  thoracic  section  of  the  longus 
colli  muscle.  The  third,  more  considerable,  springs  from  a  branch  that  is 
given  off  at  the  brachial  trunks ;  it  is  markedly  recurrent,  and  forms  on 
the  side  of  the  trachea,  with  the  second,  a  small  plexus,  and  then  lies 
closely  alongside  the  oesophagus,  which  it  accompanies  for  a  distance  of 
eight  inches  from  the  first  rib.  The  branch  constituting  the  fourth  group 
is  the  longest  of  all ;  it  is  detached  about  two  or  two  and  a-half  inches  in 
front  of  the  first  rib,  and  after  emitting  several  long  tracheal  filaments,  it 
ascends  on  the  side  of  the  trachea  close  to  the  border  of  the  oesophagus, 
where  it  generally  disappears  at  about  six  or  eight  inches  from  the  pharynx. 
The  fifth  group  is  composed  of  a  branch  detached  from  the  recurrent,  about 
the  point  where  the  preceding  terminates ;  it  goes  entii'ely  to  the  origin 
of  the  canal. 


TERMINAL  BRANCHES  OF  THE  PNEUMOGASTRIC  NERVES. 

1.  Bronchial  Plexus  (Fig.  362,  29). — The  bronchial  plexus  is  formed 
oy  several  branches  from  the  pneumogastric,  on  the  arrival  of  that  nerve 
above  the  roots  of  the  lungs,  and  which  interlace  in  a  network  and  ramify 
around  the  bronchial  divisions  following  these  into  the  texture  of  the 
pulmonary  organ.  It  is  these  branches  which  give  to  the  mucous  membrane 
its  great  sensibility,  and  which  provoke  those  evident  conti-actions  of  which 
it  is  the  seat. 

2.  (Esophageal  Branches  (Fig.  362,  30,  81).  —  After  emitting  the 
ramuscules  of  th'e  bronchial  plfe'xus,  each  pneumogastric  is  continued  along 
the  oesophagus  by  two  branches— a  superior  and  inferior — making  four 
branches  for  the  two  nerves.  The  two  superior  lie  together,  and  are 
confounded  in  a  single  cord,  either  immediately,  or  after  a  certain  course; 
the  two  inferior  comport  themselves  in  the  same  manner  with  one  another ; 
making  a  double  anastomosis,  from  which  arise  the  two  nerves  we  arc 
about  to  describe,  and  which  are  designated  the  oesophageal  nerves,  because 
of  their  situation.  The  right  nerve  forms  a  large  portion  of  the  superior 
cord  ;  the  left,  especially,  gives  ramuscules  to  the  inferior. 

Placed  between  the  layers  of  the  posterior  mediastinum,  these  two 
nerves  follow  the  oesophagus  for  a  certain  distance,  one  above,  the  other 
below,  giving  off  some  ramuscules  to  that  muscular  canal,  detaching  one  or 
two  communicating  branches,  and  traversing  the  opening  in  the  right 
pillar  of  the  diaphragm  to  penetrate  the  abdominal  cavity. 

The  inferior  terminates  in  the  parietes  of  the  stomach,  by  forming 
on  the  small  curvature,  to    the    right  of  the    cardia,  a  very  rich   plexus 


736  TEE  NEBVES. 

which  throws  the  majority  of  its  ramuscules  into  the  right  sac  of  that 
viscus. 

The  superior  passes  to  the  left  of  the  oesophageal  insertion,  along  with  the 
gastro-pulmonary  artery,  and  is  lost  in  the  solar  plexus,  after  giving  oif 
numerous  divisions  on  the  left  sac  of  the  stomach,  mixing  with  the 
sympathetic  ramuscules  that  encircle  the  gastric  artery,  and  anastomosing 
around  the  cardia  with  those  of  the  inferior  cord.  It  is  very  difficult  to 
follow  the  filaments  of  this  cord  from  the  pneumogastrics  after  their  arrival 
at  the  solar  plexus ;  we  nevertheless  observe  some  of  them  passing  to  the 
liver,  others  accompanying  the  sympathetic  branches  that  come  from  the 
solar  to  the  posterior  mesenteric  plexus  in  following  the  small  mesaraic 
vein ;  no  doubt  the  others  find  their  way  among  the  filaments  of  the 
trisplanchnic  nerve,  which  proceed  with  the  anterior  mesenteric  artery. 

FoNCTioNS  OF  THE  Pneumogastkic. — Formed  by  the  two  orders  of  fibres, 
the  pneumogastric  is  a  sensory-motor  nerve,  and  the  seat  of  reflux  currents 
which  make  it  play  a  very  important  part  in  several  acts  of  vegetative  life, 
and  bring  it  into  relationship  with  the  great  sympathetic  nerve,  with  which 
we  have  seen  that  the  tenth  pair  maintains  anastomotic  connexions  in  several 
points  of  its  course. 

It  is  the  pneumogastric  nerve  that  .gives  to  the  mucous  membrane  of  the 
larynx  the  exquisite  sensibility  it  enjoys. 

It  stimulates  the  motor  muscles  of  that  organ  into  movement. 

To  it  is  also  due  the  sensibility  of  the  broncho-pulmonary  mucous 
membrane. 

It  excites  the  contractions  of  the  muscular  fibres  in  the  broncho-tracheal 
passages — contractions  which  are  involuntary,  and  under  the  influence  of  the 
reflex  power. 

It  also  provokes  the  movements  of  the  oesophagus  and  stomach,  which 
are  also  involuntary  and  due  to  reflex  currents. 

Perhaps  it  acts  in  an  analogous  manner — by  reflex  action— in  the 
secretion  of  the  gastric  fluid  and  the  functions  of  the  liver ;  but  these  are 
points  which  science  has  not  yet  decided  upon. 

It  appears  proved  that  it  does  not  exercise  any  direct  influence  on  the 
essential  phenomena  of  respiration. 

It  also  appears  proved  that  it  acts  on  the  heart  in  a  very  energetic 
manner,  though  this  has  been  imperfectly  determined.  We  only  know  that 
after  its  section  in  the  region  of  the  neck,  the  movements  of  the  heart 
become  very  precipitate,  and  that  we  may  diminish  the  force  of  these 
movements,  or  even  completely  arrest  them,  by  galvanising  the  peripheral 
end  of  the  nerve. 

11.  Eleventh  Pair,  Spinal  Nerves,  or  Accessory  Nerves  oj  the  Pneumogastrics. 

(Fig.  338,2,4.) 

The  spinal  accessory  is  an  exclusively  motor  nerve,  which,  at  its  exit 
from  the  cranium,  is  so  intimately  connected  with  the  pneumogastric,  that 
wc  might  perhaps  follow  the  example  of  Miiller,  and  describe  the  two  as 
forming  one  and  the  same  pau\ 

Origin. — This  nerve  exhibits  a  singular  disposition,  in  that  it  arises  from 
the  whole  extent  of  the  cervical  spinal  cord,  and  ascends  in  the  spinal  canal 
to  near  the  pneumogastric,  with  which  it  leaves  the  cranium  by  the  pos- 
terior foramen  lacerum.  It  is  also  described  as  an  encephalic  nerve,  in 
consequence  of  the  latter  peculiarity ;  but  from  its  origin  it  is  rather  a 


TEE  CRANIAL  OR  ENCEPHALIC  NERVES.  737^ 

spinal  nerve,  a  fact  which  is  sufficiently  indicated  by  the  name  generally 
given  to  it. 

In  the  interior  of  the  spinal  canal,  it  is  a  long  cord  measuring  from 
27  to  31  inches  in  middle-sized  animals.  It  commences,  by  a  very  hue 
l^oint,  at  the  cervical  or  brachio-rachidian  bulb  of  the  spinal  cord,  follows 
that  organ  in  an  ascending  course,  lying  close  to  its  lateral  column,  and 
passing  betneen  the  roots  of  the  two  orders  of  cervical  nerves  until  it  arrives 
at  the  medulla  oblongata,  where  it  is  inflected  outwards  at  the  foramen 
lacerum  posterius,  into  which  it  passes  to  leave  the  cranium. 

In  this  ascending  track,  it  gradually  increases  in  volume,  as  it  at 
intervals  receives  additional  filaments  from  the  lateral  column  of  tbe  spinal 
cord,  like  the  radicular  extremity  of  the  nerve  itself.  Before  making  its 
escape  from  the  cranium,  it  receives,  besides,  some  of  the  posterior  or  motor 
roots  of  the  pneumogastric  nerve.  In  the  foramen  lacerum,  it  becomes 
applied  against  the  ganglion  (jugular)  of  that  nerve,  in  the  manner  of  motor 
fibres  of  mixed  nerves,  and  gives  it  some  of  its  proper  filaments. 

The  long  cord  here  described  as  the  root  of  the  sjiiual  accessory,  is 
considered  by  some  authorities  as  only  a  portion  of  this  nerve,  to  which 
they  give  the  name  of  external  or  medullary  root  cf  the  spinal  accessory. 
They  designate  as  tbe  internal  or  bulbous  root  of  that  nerve,  the  anastomosing 
filaments  already  described  as  the  motor  roots  of  the  pneumogastric. 
According  to  them,  this  internal  root  only  lies  beside  the  pneumogastric  for  a 
very  short  distance,  ultimately  leaving  it  and  forming  the  superior  laryngeal 
and  pharyngeal  nerves,  which  seem  to  arise  from  the  vagus  rather  than 
the  accessory  of  Willis. 

Distribution. — Beyond  the  ganglion  of  the  pneumogastric,  the  spinal 
accessory  remains  beside  the  trunk  of  the  pneumogastric  for  scarcely  an 
inch ;  it  then  separates  from  it  at  an  acute  angle  whose  sinus  is  occupied 
by  the  great  hypoglossal  r.erve,  is  directed  backwards,  passing  beneath  the 
superior  extremity  of  the  maxillary  gland  and  levator  humeri,  gains  the 
supero-posterior  border  of  that  muscle,  and  follows  it  to  the  front  of  the 
shoulder.  Here  it  slightly  ascends,  crosses  that  region  below  the  inner 
face  of  the  cervical  trapezius,  and  is  distributed  to  the  dorsal  trajjezius. 

On  its  passage  it  emits  :  1.  One  or  two  thick  filaments  to  the  superior 
cervical  ganglion,  proceeding  from  the  spinal  by  a  small  plexiform  network 
where  the  nerve  separates  from  the  pneumogastric ;  2,  Near  the  maxillary 
gland,  a  thick  branch  to  the  sterno-maxiljaris  muscle ;  3,  Slightly  beyond 
this,  another  branch  destined  to  the  anterior  portion  of  the  levator  humeri  ; 
4,  A  series  of  ramuscules  to  the  cervical  trapezius. 

In  its  course,  the  spinal  accessory  traverses  the  anterior  part  of  the 
superficial  cervical  plexus,  and  receives  additional  ramuscules  from  the 
first,  second,  thii'd,  foui'th,  fifth,  and  sometimes  even  from  the  sixth  cer- 
vical nerves. 

Reduced  to  its  medullary  root,  as  has  been  described,  the  spinal 
accessory  animates  the  muscles  to  which  it  is  distributed,  and  through  them 
has  a  share  in  expiration.  By  the  contraction  of  these  muscles,  the  ribs 
may  be  maintained  raised  for  a  certain  period,  and  cause  the  aii-  to  be  slowly 
expelled  ;  also  allowing  the  sounds  or  voice  produced  by  its  passage  through 
the  larynx  to  be  modulated.  Crowing  is  no  longer  possible  in  birds  when 
the  medullary  root  of  the  spinal  accessory  has  been  divided,  as  has  been 
demonstrated  by  Bernard. 


738  THE  NERVES. 

12.   Twelfth  Pair,  or  Great  Hypoglossal  Nerves. 
(Figs.  111,22;  338,  5;  342.) 

The  great,  or  simply  the  hypoglossal  nerve,  is  exclusively  motor,  and 
animates  the  muscles  of  the  tongue. 

Fisr.  342. 


DEEP  NERVES  OF  THE  HEAD. 

1,  Superior  maxillary  nerve  at  its  exit  from  the  foramen  lacerum;  2,  Trunk  of  the 
masseteric  ;  3,  Trunk  of  the  subzygomatic ;  4,  Buccal ;  5,  Lingual  or  gustatory  ; 
6,  Chorda  tympani ;  7,  Inferior  maxillary,  cut  near  whei-e  it  enters  the  maxillo- 
deatal  canal ;  8,  Trunk  of  the  mylo-hyoideus ;  9,  Pterygoid  ;  10,  Glosso-pharyngeal ; 
11,  Its  pharyngeal  branch;  12,  Its  lingual  branch;  13,  Pneumogastric ;  14, 
Superior  laryngeal  branch  of  that  nerve  ;  15,  Its  pharyngeal  branch  ;  16,  Spinal 
accessory  of  Willis  ;  17,  Great  hypoglossal ;  18,  Origin  of  the  cervical  cord  of  the 
great  sympathetic;  19,  The  same  after  its  union  with  the  pneumogastric. — A, 
Common  carotid  artery  ;  B,  Accessory  thyroid  artery  ;  C,  Thyro-laryngeal  artery  ; 
D,  Origin  of  the  internal  carotid  artery — the  vessel  is  concealed  by  the  guttural 
pouch;  ^,  Occipital  artery;  i^.  External  carotid  artery;  (?,  Internal  maxillary 
artery  ;  H,  Pharyngeal  artery  (drawn  too  large)  ;  /,  External  maxillary  artery  ; 
/,  Lingual  artery;  K,  Origin  of  the  maxillo-muscular  artery;  L,  Posterior 
auricular  artery  ;  M,  Trunk  or  origin  of  the  superficial  temporal  artery ;  0, 
Inferior  dental  artery;  P,  Posterior  deep  temporal  artery;  Q,  Anterior  deep 
temporal  artery  ;  i?.  Maxillary  gland  ;  ^',  Wharton's  duct ;  1\  Sublingual  gland. 
The  letter  N  placed  at  the  upper  end  of  the  large  coj-nu  of  the  hyoid  bone  has 
no  siguificatiou. 

Origin  — It  originates  at  the  lower  face  of  the  mr-dulla  oblongata,  from 


THE  CRANIAL  OB  ENCEPHALIC  NERVES.  739 

the  prolongation  of  the  line  of  insertion  of  the  inferior  spinal  roots,  by  a 
dozen  converging  filaments.  These  traverse  the  dura  mater  in  two  or 
three  bundles,  which  enter  the  condyloid  foramen  of  the  occipital  bone, 
where  they  unite  to  form  a  single  cord.  The  hypoglossal  has  also  a 
ganglionic  root  which  Toussaint  constantly  found  in  the  Ass,  Mule,  Ox, 
and  Dog,  and  which  had  been  previously  seen  by  Meyer  and  Vulpian. 
The  ganglion  of  the  hypoglossal  in  the  Horse  is  fusiform,  and  the  size  of 
a  small  lentil  (Fig.  338,  o').     It  is  sometimes  absent. 

Distribution. — The  hypoglossal  nerve  thus  constituted,  immediately  after 
its  departure  from  the  condyloid  foramen,  commimicates  with  the  first 
cervical  pair  by  means  of  a  transverse  ramuscule  ;  it  then  passes  between 
the  spinal  accessory  and  pneumogastric  nerves,  descends  on  the  external 
face  of  the  guttural  pouch,  where  it  is  connected  with  the  superior  cervical 
ganglion  of  the  sympathetic  by  numerous  filaments,  which  in  great  part  form 
the  plexiform  network  called  the  "  guttural  plexus."  The  nerve  afterwards 
crosses  to  the  outside  of  the  external  carotid  artery,  in  proceeding  forward 
and  downward  on  the  side  of  the  pharynx  and  larynx,  receiving  at  that 
point  a  slender  ramuscule  from  the  first  cervical ;  it  then  passes  within  the 
inferior  extremity  of  the  stylo-hyoid  muscle  and  the  glosso-facial  artery, 
which  it  crosses  very  obliquely,  is  prolonged  between  the  mylo-hyoid  and 
hyo-glossus  brevis  muscles,  sends  numerous  small  filaments  to  the  latter  and 
a  ramuscule  to  the  genio-hyoideus,  and  finally  termiuates  in  a  series  of 
branches  analogous  to  those  of  the  gustatory  nerve,  and  which  mix  with 
them. 

These  branches  are  therefore  reflected  upwards,  bending  round  the 
posterior  border  of  the  hyo-glossus  brevis,  and  pass  into  the  interstice  between 
that  muscle  and  the  genio-glossus.  They  are  distributed  to  all  the  muscles 
of  the  tongue. 

The  hypoglossals,  being  motor  nerves,  cause  the  contraction  of  the 
muscles  of  the  tongue  during  the  movements  proper  to  mastication  and  the 
production  of  the  voice.  Though  they  most  frequently  act  together,  yet 
they  may  do  so  separately,  as  in  the  unilateral  movements  of  the  tongue. 

DIFFERENTIAL   CHARACTERS   IN   THE   CKANIAL   NERVES   OF   OTHER   THAN   SOLIPED 

ANIMALS. 

In  the  domesticated  mammals,  the  cranial  nerves  offer  the  greatest  analogies  ;  their 
origin  U  the  same  in  all,  and  it  is  only  in  their  distribution  that  we  find  some  variety, 
due  to  the  difference  in  the  form  of  the  head.  Consequently,  in  this  comparative  analysis 
we  sliall  not  discover  any  fundamental  diSerential  characters. 

Ruminants. — There  is  no  difference  to  note  in  the  four  first  pairs. 

Trigeminal  nerve. — Divided  into  three  branches  as  in  Solipeds.  It  has  been  stated 
that  in  Rimiinants  the  ophthidmic  branches  are  distributed  to  the  majority  of  the  muscles 
of  the  eye ;  in  the  Sheep  we  have  only  seen  the  palpehro-nasal  nerve  offering  this  relation- 
ship to  the  motor  organs  of  that  part.  The  anterior  palatine  nerve  is  relatively 
voluminous. 

Facial  nerve  — Towards  the  middle  of  its  subparotideal  course,  this  gives  off  a  large 
anterior  auricular  nerve  :  when  it  arrives  at  the  middle  of  the  posterior  border  of  the 
masstter  muscle,  it  divides  into  two  branches.  The  inferior  branch  passes  obliquely  down- 
wards and  forwards,  towards  the  mental  foramen,  where  it  terminates  as  in  the  Horse  ; 
it  furnishes  an  anastomotic  branch  to  the  superior.  The  latter  cro.<scs  the  middle 
portion  of  the  masseter,  and  becomes  mixed  with  the  suborbital  ramu.-cules  of  the  fifth  pair ; 
about  the  middle  of  its  course  it  receives  a  filament  from  the  superficial  temporal  nerve. 
We  need  not  allude  to  tlie  auditory  and  qlosso-pharynqeal  nerves,  except  to  say  that  the 
latter  communicates  with  the  pneumogastric  soon  after  its  exit  from  the  foramen  lacerum. 

Pneumogastric  nerve. — This  offers  iiumeious  differences  in  its  nots  and  distribution. 

In  the  Ox  and  Sheep,  the  sensitive  roots  arise  from  an  irreguluvly  elliptical  suiface 
comprising  the  whole  of  the  respiratory  tract.     They  are  from  fifteen  to  twenty  in 


740 


THE  NERVES. 
Ficr.  343 


NERVES  OF  THE  GUTTURAL  REGION  IN  THE  OX. 

a,  (Esophagus ;  b,  Trachea;  c',  Common  carotid  artery;  d,  Glosso-facial  artery;   1, 
Pneumogastric  nerve  j  2,  Spinal  accessory  ;  3,  Glosso-pharyngeal ;  4,  Great  sym- 


THE  CRANIAL  OR  EK CEPHALIC  NERVES.  741 

mnnber,  and  often  join  each  other;  they  may  divided  into  three  principal  fasciculi  rising 
at  bliglit  distances. 

The  motor  roots  are  a  little  larger  tl  an  in  the  Horse  ;  before  joining  the  sensitive  roofs 
they  are  confounded  in  a  small  yaiiglioii  that  pertains  to  them. 

Tho  juriular  ganglion  is  voluminous,  but  apart  from  this  it  presents  the  same  features 
as  in  the  Horse,  receiving  all  the  proper  roots  of  the  pneumogastric  and  internal  root  of 
tlie  spinal  accessory,  and  even  those  wliicli  are  united  in  their  own  ganglion.  The 
portion  of  the  ganglion  that  is  more  especially  formtd  by  the  roots  of  the  spinal  accessory 
is  rather  an  intrication  of  nerve-fibres  than  a  real  ganglion ;  it  is  impossible  by  the  moot 
nrinute  disseetiun  to  separate  it  from  the  rest  of  the  ganglion. 

The  jugular  ganglion  also  receives  a  division  of  the  glosso-pharyngeal,  and  it  gives 
one  to  this  nerve  and  the  external  branch  of  the  spinal  accessory. 

The  pneumogastric  nerve,  in  the  guttural  portion,  is  much  larger  than  in  the  Horse. 
This  peculiarity  is  noticeable  throughout  its  whole  extent,  and  is  iadicated  at  its 
roots. 

The  ganglionic  plexus  is  absent  in  the  Ox.  The  course  and  relations  of  the  nerve  in 
this  portion  are  analogous  to  those  observed  in  Solipeds. 

The  pharyngeal  nerve  is  voluminous,  and  the  branch  it  sends  to  the  oesophagus  is  the 
largest  rif  its  divisions  :  this  branch  passes  backwards  to  the  surface  of  the  constrictors 
of  the  pharynx,  joins  the  external  laryngeal,  gives  a  large  branch  to  the  thyro-pharyngeus, 
anil  is  insinuated  on  the  sides  of  the  oesophagus,  between  it  and  the  thyroid  gland ;  thcie 
it  divides  into  two  portions,  one  of  which  descends  on  the  sides  of  the  oesophagus  where 
it  forms  a  very  rich  plexus  with  the  branches  from  the  inferior  laryngeal,  while  the  other 
is  lost  immediately  in  the  recurrent  nerve  at  the  thyroid  gland. 

The  external  laryngeal  arises  at  a  short  distance  above  the  superior  laryngeal,  where 
it  receives  a  large  branch  from  the  glosso-pharyngeal  and  another  from  the  sympathetic, 
and  immediately  passes  alongside  the  oesophageal  branch  of  the  pharyngeal  nerve. 
With  a  little  attention,  we  may  dissect  a  fasciculus  coming  from  the  external  laryngeal 
and  passing  to  the  crico-thyroid  muscle,  and  the  thyroid  gland  and  its  vessels,  after  receiv- 
ing a  branch  from  the  superior  laryngeal.  In  the  Sheep,  the  external  laryngeal  sometimes 
gives  a  branch  to  the  oesophagus,  and  which  anastomoses  with  the  inferior  laryngeal,  or 
descends  on  the  side  of  the  tube,  conjointly  with  the  oesopl.ageal  branch  of  the 
pharyngeal. 

The  superior  laryngeal  rises  below  the  preceding ;  it  is  very  voluminous,  and  com- 
municates with  the  sympathetic,  either  directly  or  through  the  medium  of  the  guttural 
plexus,  and  with  the  pharyngeal  nerves  and  external  laryngeal.  Beneath  the  thyroid 
cartilage,  a  large  division  anastomoses  with  the  inferior  laryngeal,  and  is  finally  lo'jt  in 
that  nerve  below  the  larynx  It  is  easily  seen  that  this  branch  gives,  in  the  cervical 
region,  a  great  number  of  filaments  to  the  oesor  harus  and  trachea. 

With  the  exception  of  some  insignificant  puruliarities,  the  pneumogastric  com poits 
itself  in  the  cervical  and  thoracic  regions  as  in  the  Horse. 

The  recurrente  aiise  as  in  Solipeds,  but  their  lelaiions  are  somewhat  ditferent  in  the 
cervical  region.  They  are  placed  in  the  channel  formed  by  the  trachea  and  ce.-ophagus, 
and  are  separated  from  the  carotid  artery  and  the  cord  common  to  the  sympathetic  and 
pneumogastiic  by  the  very  great  width  of  the  oesophagus.  Their  distribution  to  the 
muscles  of  tiie  larynx  takes  place  as  in  the  Hoise;  ihe  only  noteworthy  feature  is  the 
anastomosis  of  the  nerve,  end  to  end,  with  the  superior  laryngeal.  In  the  whole  of  its 
cervical  portion,  the  branches  to  the  oesophagus  are  more  numerous  and  voluminous  than 
in  Solipeds,  although  they  all  have  the  same  physiologit-al  office,  except  those  that  arc 
derived  from  the  branch  of  tlie  superior  laryngeal,  which  are  motor. 

The  ditferences  remarked  in  tne  nerve  in  the  abdominal  cavity,  are  in  relation  to 
the  volume  and  form  of  the  stomach  and  its  compartments. 

The  following  is  what  we  have  observed  in  the  Sheep : 

After  receiving  a  large  filament  from  the  superior  cord,  the  inferior  oesophageal  nerve 
divides  into  three  principal  branches :  one  passes  to  the  left,  furnishing  nerves  to  the 
anterior  face  and  greater  curvature  of  the  reticulum  and  the  upper  border  of  the  rumen  ; 
a  median,  which  is  distributed  to  the  anterior  face  of  the  psalterium.  reaches  the  snb.-tanco 
of  the  mesentery,  follows  the  abomasum,  to  which  it  sends  some  filaments,  and  finally 
anastomoses  with  the  retrograde  nerves  coming  from  a  rich  plexus  that  exists  on  the 
posterior  face  of  the  liver  and  gall-bladder  ;  it  forms,  conjointly  with  the  divisions  of  tlie 


pathetic  and  cervical  ganglion  ;  5,  Pharyngeal  nerve  ;  6,  External  laryngeal ;  7,  Superior 
laryngeal ;  8,  Inferior  laryngeal ;  9,  9,  (Esophageal  branches  of  the  pharyngeal  and  ex- 
ternal laryngeal. 

50 


742  THE  NERVES. 

solar  plexus  and  superior  ceso])hageal  nerve,  a  ricli  plexus,  from  -which  arise  branches  to 
the  liver,  abomasiun,  and  duodenum. 

The  superior  oesophageal  nerve  is  chiefly  distributed  to  the  rumen.  Before  reaching 
the  stomach,  it  gives  several  divisions  to  the  plexus  already  mentioned — and  which 
might  be  named  the  "  hepatic  plexus."  receives  a  large  branch  from  the  solar  plexus, 
and  sends  to  it  a  smaller  one.  It  afterwards  divides  into  two  principal  branchee,  the 
largest  of  which  passes  along  the  superior  fissure  of  the  rumen,  along  with  the  vessels  of 
that  oro-an.  According  to  Lavocat,  this  branch  forms  a  large  plexus  there,  which  has  in 
its  centre  a  ganglionic  enlargement,  whence  emanate  the  ramuscules  that  go  to  tlie  whole 
of  the  upper  fac'e,  sides,  and  lower  surface  of  the  rumen.  In  the  Siieep  we  have  not  found 
a  ganglion,  but  this  does  not  prevent  this  branch  from  being  distributed  to  all  the  parts 
indicated  bv  Lavocat. 

The  other  branch  is  very  large,  and  situated  in  the  omentum  until  it  arrives  at  its 
convex  border,  when  it  leaves  it  to  be  distributed  to  the  left  side  of  the  abomasum ; 
while  the  analogous  nerve  from  the  inferior  oesophageal  passes  more  especially  to  the 
right  face. 

Spinal  accessory. — Tlie  origin  of  this  nerve  oifers  slight  differences,  which  we  have 
indicated  in  speaking  of  the  motor  roots  of  the  pneumogastric.  With  regard  to  its  dis- 
tribution in  the  Ox,  it  offers  the  following  features :  At  the  inferior  extremity  of  the 
transverse  process  of  the  atlas  it  divides  into  two  branches,  a  superior  and  inferior.  The 
first  is  a  little  larger  than  the  spinal  accessory  of  the  Horse,  and  comports  itself  as  in 
that  animal.  The  inferior  branch  is  directed  downward  and  backward,  traverses  the 
muscle  we  have  named  the  sterno-suboccipital,  beneath  a  tendon  that  runs  across  the 
muscular  fibres,  and  arrives  between  that  muscle  and  the  sterno-maxillaris.  At  this 
point  it  separates  into  a  certain  number  of  ramuscules,  the  first  three  or  four  of  which 
are  slightly  recurrent,  and  enter  the  upper  part  of  the  sterno-maxillaris  ;  the  others  are 
large  and  directed  towards  tlie  sternum,  to  be  distributed  to  the  latter  muscle,  or  to  it  and 
the  sterno-suboccipitalis. 

These  branches  of  the  spinal  accessory  represent  the  branch  which,  in  the  Horse,  passes 
exclusively  to  the  sterno-maxillaris.  In  reflecting  on  the  distribution  they  off"er  in  the 
Ox.  we  are  brought  to  the  conclusion  tliat  the  internal  band,  which  has  been  described  as 
belonging  to  the  first,  forms,  with  the  sterno-suboccipitalis,  one  and  the  same  muscle — 
tlie  analogue  of  the  sterno-maxillaris  or  steino-mastoideus  of  Solipeds.  These  two 
muscular  "fasciculi  are,  otherwise,  closely  attached  to  each  other,  if  not  confounded  near 
their  origin  at  the  anterior  prolongation  of  the  sternum. 

Lastly,  the  great  hypoglossal  nerve,  before  crossing  the  pneumogastric,  communicates 
with  the' first  cervical  by  a  considerable  branch;  lower,  it  gives  off  along  ramuscule 
that  descends  on  the  carotid  artery. 

Pig. — We  need  not  refer  to  the  olfactory,  optic,  or  motor  nerve  of  the  eije,  neither  to 
the  glosso-pharyngeal,  as  what  has  been  said  about  them  in  Solipeds  holds  good  in  this 
animal. 

Trigeminal  nerve.— This  also  divides  into  three  principal  branches.  The  palpebro- 
nasal ramuscule  of  the  ophthalmic  branch  anastomoses  with  a  motor  nerve  of  the  eye  on 
the  deep  face  of  the  external  rectus  muscle.  The  superior  maxillary  nerve  leaves  the 
cranium  by  the  great  sphenoidal  slit,  and  immediately  enters  the  superior  dental  foramen  ; 
its  orbital  course  is  therefore  very  short. 

Its  spheno-palatine  branch  passes  at  once  below  the  alveolar  tuberosity,  where  it 

.  divides  into  several  ramuscules :  one,  entering  the  palatine  fissure,  forms  the  posterior 

palatine  nerve  ;  the  others  pass  into  the  palatine  arch  at  various  distances,  to  constitute 

the  middle  palatine  nerves  ;  some  of  them  even  enter  the  palatine  canal  with  the  anterior 

'palatine  or  palato-labial  nerve. 

Facial— Beneath,  the  parotid  gland,  this  divides  into  several  branches,  of  which  there 
are  three  principal.  One  is  directed  upwards,  and  passes  in  front  of  the  ear ;  this  is  the 
smallest.  The  second  proceeds  forward,  crosses  the  masseter  near  the  zygomatic  process, 
unites  with  the  inferior  branch,  and  is  expended  among  the  suborbital  ramuscules  of  the 
superior  maxillary.  The  third  passes  downward  and  forward,  under  the  parotid  gland, 
arrives  in  the  intermaxillary  space,  is  inflected  in  front  of  the  masseter  to  become  super- 
ficial, and  terminates  with  the  middle  branch.  Towards  the  maxQlo-labialis  muscle, 
this  inferior  branch  gives  off  a  ramuscule  to  the  lower  lip. 

Pneumogastric. — This  joins  the  great  sympathetic  near  the  upper  third  of  the  neck, 
and  at  its  point  of  union  offers  a  greyish  enlargement  resembling  the  gangliform  plexus 
of  Man.  Until  the  origin  of  the  oesophageal  nerves,  the  pneumogastric  of  the  Pig 
resembles  that  of  the  Horse.  The  latter  is  voluminous,  and  does  not  divide  into  two 
branches  immediately  beyond  the  bronchial  plexus,  but  at  some  distance  from  it. 
:  Numerous  anastomoses  exist  between  the  two  oesophageal  nerves— superior  and  inferior. 


THE  CB  AXIAL  OR  EX  CEPHALIC  NERVES.  743 

At  their  termination  they  differ  much  from  each  other  in  volume;  the  inferior  is  very 
siuall,  and  terminates  on  the  anterior  face  of  the  stomach ;  the  superior,  much  larger, 
partly  remains  at  the  stomach,  and  partly  crosses  the  small  curvature  of  that  viscus  to 
enter  the  solar  plexus. 

Spinal  accessory. — Tliis  nerve  commences  and  terminates  as  in  Solipeds.  After  being 
inflected  backward  on  the  anterior  border  of  the  mastoido-humeralis,  it  divides  into  two 
ramusculea — a  deep  and  superficial.  The  first  is  confounded  with  a  cervical  nerve,  near 
tlie  intervertebral  foramen  through  which  the  latter  passes;  the  second  goes  to  the 
trapezius  muscle,  in  which  it  is  expended. 

Near  the  base  of  the  tongue,  the  hypoglossal  gives  off  a  filament  that  psisses  to  the 
genio-hyuideus  muscle. 

Caexivoba. — In  these  animals,  the  majority  of  the  cranial  nerves  do  not  offer  any 
important  differences.  We  will,  theiefore,  say  nothing  concerning  the  first  two  pairs, 
the  mu^ores  oculorum,  spinal  accessory,  and  glosso-pharyngeal,  except  that  the  motor 
nerves  of  the  eye  are  mixed  with  the  filament  of  the  ophthalmic  branch  among  the 
muscles  of  the  orbit. 

Trigeminal  nerve. — When  the  branch  constituting  the  superficial  temporal  nerve 
reaches  the  posterior  border  of  the  maxilla,  it  divides  into  several  ramuscules;  one 
portion  lies  beside  the  middle  branch  of  the  facial,  the  otlier  accompanies  the  anterior 
auricular  nerve  by  becoming  intimately  united  to  it.  We  have  also  found,  in  the  Dog,  a 
branch  that  is  detached  from  the  inferior  maxillary,  almost  immediately  after  its  exit 
from  the  cranium  ;  it  descends  into  the  intermaxillary  space,  in  company  with  the  facial 
artery ;  at  the  posterior  border  of  the  mylo-hyoideus  muscle  it  separates  into  two 
ramuscules :  one  is  applied  to  that  muscle,  and  follows  it  to  near  the  symphysis  of  the 
jaw  ;  the  other  is  inflected  outwards  and  upwards,  in  front  of  the  masseter  muscle,  and 
joins  the  inferior  branch  of  the  facial.  Owing  to  this  arrangement,  each  of  the  branches 
of  tiie  facial  is  provided  with  a  sensitive  ramuscule  from  the  fifth  pair. 

Facial. — At  its  exit  from  the  external  auditory  hiatus,  it  divides  into  four  branches, 
three  of  wliich  appear  to  form  its  terminution.  The  first,  the  smallest,  is  directed  down- 
wards across  tlie  parotid  gland,  and  constitutes  the  cervical  ramuscule.  The  other  three 
are  distinguished  as  superior,  middle,  and  inferior. 

The  superior  branch,  the  largest,  ascends  towards  the  forehead,  and  describes  a  curve 
whose  convexity  is  upwards,  turns  round  the  orbit,  and  terminates  near  its  nasal  angle. 
In  its  course  it  furnishes :  1,  An  anterior  auricuhir  ramuscule ;  2,  Above  the  insertion  of 
the  masseter.  several  muscular  filaments ;  3.  It  is  crossed,  above  the  eye,  by  the  super- 
ciliary filaments  of  the  ophthalmic  nerve.  The  middle  branch  accompanies  Stenon's  duct 
to  the  surface  of  the  cheek ;  reaching  the  anterior  border  of  the  masseter,  it  anastomoses  in 
a  very  flexuous  manner  witli  the  ramuscule  of  the  iuferior  branch,  and  terminates  in  the 
upper  lip  and  the  end  of  the  nose.  The  inferior  branch  passes  towards  the  maxillary 
fissure ;  there  it  receives  the  sensitive  ramuscule  sent  to  it  by  the  fifth  pair,  gives  off 
filaments  to  the  middle  branch,  and  is  then  continued  into  the  lower  lip. 

Pneumogasfric. — The  sen.ntire  rooU  closely  resemble,  in  their  disposition,  those  in  the 
Ox.  The  motor  roots  are  separated  into  two  series  of  filaments ;  the  anterior  unite  in  a 
small  ganglion,  then  pass  into  the  jugular  ganglion ;  the  posterior  lie  beside  the  medul- 
lary root  of  the  spinal  accessory,  but  leave  it  to  become  united  with  the  jugular  ganglion. 

Beloic  the  foramen  lacerum.  the  pneumogasfric  nerve  gives  off  the  pharyngeal  nerve 
before  forming  the  analogue  of  the  plexiform  ganglion  of  Man.  This  plexus  is  better 
defined  than  in  him.  and  is  a  real  fusiform  elongated  ganglion,  at  the  grey  basis  of  which 
some  white  filaments  are  seen.  It  is  situated  a  little  farther  from  the  cranium  tlian  the 
superior  cervical  ganglion.  The  ganglion  itself  furnishes  the  superior  laryngeal  nerve, 
which  gives  off.  as  in  Man.  the  external  laryngeal  nerve. 

There  is  nothing  to  indicate  in  the  pharyngeal  nerve,  its  disposition  being  absolutely 
the  same  as  in  the  Ox. 

In  the  Dog  the  superior  laryngeal  has  a  curious  disposition,  which  has  not  yet.  to 
our  knowledge,  been  described.  Reaching  the  inner  face  of  the  thyroid  cartilage,  it  gives 
off,  as  in  the  other  animals,  filaments  to  the  glottis,  epiglottis,  base  of  the  tongue,  and 
oesophagus ;  but  the  ramuscule  of  Galien,  which  nearly  equals  the  superior  laryngeal  iu 
voliune.  does  not  anastomose  with  the  inferior  laryngeal ;  it  gives  a  large  branch  to  the 
crico-arytenoid  muscle  in  passing  to  its  surface,  and  then  leaves  the  larynx  to  the  inside 
of  the  recurrent,  descending  on  the  trachea  as  far  as  the  entrance  to  the  chest.  In  that 
cavity,  the  descending  branch  of  the  superior  laryngeal  forms  two  divisions  that  com- 
municate with  the  ramuscules  of  vnrious  other  nerves  passing  into  this  regiun.  On  the 
right  side,  the  largest  division  receives  a  voluminous  branch  from  the  inferior  cervical 
ganglion;  then  the  two  divisions  unite,  and  join  the  pncumogastric  after  it  lias  turned 
round  the  brachial  trunk,  a  little  behind  the  point  of  emergence  of  ih^  infeiior  lar\  ngeal. 


744  THE  NERVES. 

On  the  left  side  the  same  arrangement  is  found ;  the  anastomoses  are  larger  and  more 
numerous  than  on  the  right  side ;  the  branch  follows,  in  an  inverse  direction,  the  course 
pursued  by  the  recurrent  nerve,  to  join  the  pneumogastric  at  the  part  where  the  recurrent 
originates  from  the  latter. 

In  this  course,  the  branch  gives  large  ramuscules  to  the  oesophagus  and  trachea ; 
those  distributed  to  the  former  either  pass  along  the  muscular  tunic  and  return  again  to 
the  nerve,  or  continue  along  the  surface  of  that  tube.  In  all  cases,  there  is  found  on  the 
sides  of  the  oesophagus  a  rich  plexus  formed  by  these  filaments,  as  well  as  by  those 
coming  from  the  pharyngeal  nerve. 

This  branch  also  ofi'ers  other  peculiarities.  Thus,  it  is  very  often  found  alongside  the 
laryngeal  nerve  for  some  distance,  and  sometimes  at  sevt^ral  points.  When  this  happens 
in  the  upper  part,  at  the  larynx,  as  occurs  in  many  cases,  it  appears  to  have  an  anasto- 
mosis as  m  the  Ox ;  but  it  is  always  easy  to  sepnrate  the  two  nerves,  even  in  fresh 
specimens,  and  this  separation  is  greatly  facilitated  if  the  piece  has  been  steeped  in 
water  acidulated  by  nitric  acid. 

lu  the  cervical  ■portion,  the  pneumogastric  nerve  is  closely  united  to  the  sympathetic, 
the  separation  of  tlie  nerves  being  no  longer  possible  as  in  the  Horse  and  Ox. 

We  have  already  described  a  portion  of  the  inferior  laryngeal  nerve,  in  speakinij  of 
the  tracheo-cesophageal  branch  of  the  superior  laryngeal.  Comparison  with  other 
animals  requires  that  we  should  transfer  the  latter  to  the  recurrent.  In  the  Dog,  the 
inferior  laryngeal  rises  by  two  distinct  branches,  a  short  distance  from  each  other,  on  the 
right  and  left  sides  ;  these  may,  or  may  not,  lie  together  for  some  distance,  but  they  never 
become  fused.  The  external  part  of  the  nerve  receives  at  intervals  filaments  proceeding 
from  the  superior  laryngeal  branch,  and  it  rarely  gives  very  fine  twigs  to  the  trachea 
and  oesophagus.  The  communications  with  the  cardiac  and  tracheal  nerves  are  also 
chiefly  made  by  the  tracheo-cesophageal  branch. 

The  bronchial  nerves  are  large  and  numerous. 

The  oesophageal  plexus,  which  is  furnished  by  the  nerves  of  the  same  name,  is  larger 
and  finer  than  in  the  Horse. 

There  is  nothing  to  note  particularly  in  the  termination  of  the  nerves  in  the 
stomach. 

'I'he  hypoglossal  gives  a  long  branch  that  passes  to  the  sides  of  the  larynx,  and  enters 
the  muscles  on  the  anterior  face  of  the  trachea. 


COMPARISON   OF  THE   CRANIAL   NERVES   OF   MAN   WITH   THOSE   OF   ANIMALS. 

The  few  modifications  offeretl  by  the  cranial  nerves  of  Man,  when  compared  with 
tliose  of  animals,  are  dictated  by  the  disposition  of  the  parts  and  organs  to  which  they 
are  distributed. 

We  have  spoken  of  the  olfactory  lobes  when  studying  the  brain,  so  that  we  need  not 
again  refer  to  them.     The  three  succeeding  nerves  ofler  nothing  worthy  of  mention. 

Trigeminal  nerve. — Tiiis  has  the  same  origin  and  divisions  as  in  animals. 

The  frontal  nerve  of  the  ophthalmic  portion  divides  into  two  brandies ;  these  are 
inflected  upwards  on  the  margin  of  the  orbit,  and  distributed  to  the  skin  of  the  forehead. 
These  two  branches,  well  developed  in  the  Dog,  are  distinguished  as  internal  and 
external.  The  latter  anastomoses  with  a  branch  of  the  facial.  The  nasal  nerve,  after 
spreading  over  the  surface  of  the  turbinated  bones  and  the  meatus,  gives  off  a  ramuscule 
that  becomes  subcutaneous  in  passing  between  the  infeiior  border  of  the  nasal  bone 
and  cartilage  of  the  nostril ;  this  is  the  naso-lobular  nerve. 

The  superior  maxillary  nerve  leaves  the  cranium  by  the  foramen  rotundum,  reaches 
the  suborbital  furrow,  and  spreads  over  the  face  by  suborbital  bianches.  Like  that  of 
animals,  it  gives  rise  to  an  orbital  ramuscule,  and  posterior  and  anterior  dental  branches. 
Ditferences  appear  in  the  other  branches  which  are  furnished,  in  animals,  by  the 
superior  maxillary  nerve :  in  Man  these  branches  leave  Meckel's  ganglion.  The  fila- 
ments leaving  this  ganglion  are:  1,  The  pharyngeal  nerve  of  Bock  which  is  distributed  in 
the  upper  portion  of  the  mucous  membrane  of  the  pharynx,  in  that  of  the  Eustachian 
tube  and  the  posterior  orifice  of  the  nasal  cavities;  2,  The  palatine  nerves — great  or 
anterior — sent  to  the  raucous  membrane  of  the  anterior  portion  of  the  palate;  middle 
jja/a^He,  distributed  to  that  of  the  soft  palate,  and  posterior  palatine,  that  goes  to  the  two 
faces  of  the  soft  palate  and  its  muscles ;  3,  The  nasal  or  spheno-palotine  nerve. 

The  inferior  maxillary  nerve  closely  resembles  that  of  animals,  the  only  differences 
con.sisting  in:  ].  The  deep  middle  temporal  nerve  rising  direct  from  the  maxillary; 
2,  The  lingual  nerve  is  detached  near  the  base  of  the  cranium ;  3,  The  superficial 
temporal  nerve  furnishes,  independently  of  the  filaments  uniting  it  to  the  facial,  an 


THE  CRANIAL  OR  ENCEPHALIC  NERVES. 


745 


auriculo-tcmporal  branch  that  ascends  in  front  of  the  ear,  and  terminates  in  the  skin  of 
the  temporal  region. 

In  Man,  there  is  annexed  to  the  fifth  pair  the  submaxillary  ganglion,  which  receives 
a  sensitive  bianch  from  the  lingual,  a  motor  tilament  from  tlie  chorda  tympaui,  and 
sympathetic  filaments  ;  it  gives  olf  several  emergent  filaments,  nearly  all  of  which  pass 
into  the  maxillary  gland.     There  is  nothing  to  say  of  the  internal  motores  oculormn. 

Facial.- In  its  collateral  branches,  the  facial  nerve  of  Man  is  absolutely  the  same  as 
in  animals.      It   has,   however,   a   branch  not  described   in   them — the  ramuscule  of 


NERVES  OF   THE   FACE   AND   SCALP. 

1,  Attrahens  aurem  muscle;  2,  Anterior  belly  of  occipito-frontalis ;  3,  Auriculo- 
temporal nerve ;  4,  Temporal  branches  of  facial ;  5,  Attolens  aurem  muscle ;  6, 
Supra-trochlear  (5th) ;  7,  Posterior  belly  of  occipito-frontalis  ;  8,  Supra-orbital ; 
9,  Retrahens  aurem  muscle;  10.  Temporal  branch  of  temporo-orbital ;  11,  Small 
occipital ;  12,  Malar  branches  of  facial ;  13,  Posterior  auricular  (7th)  ;  14,  Malar 
branch  of  temporo-malar  (5);  15,  Great  occipital;  16,  Infra-orbital  branches  of 
facial;  17,  Facial;  18,  Nasal;  19,  Cervico-facial  division  of  7th;  20,  Infra- 
orbital; 21,  Branches  of  digastric  and  stylo-hyoid  ;  22,  Temporo-facial  division  of 
7th ;  23,  Great  auricular ;  24,  Buccal  branches  of  facial ;  25,  Trapezius  muscle ; 
26,  Buccinator  (5th) ;  27,  Splenius  capitis  ;  28,  Masseter  ;  29,  Sterno-mastoideus ; 
30,  Supermaxillary  branches  of  facial  nerve;  31,  Superficial  cervical;  32, 
Mental ;  33,  Platysma  muscle  ;  34,  Submaxillary  branches  of  facial  nerve. 


Hirschfeldf  which  reaches  the  base  of  the  tongue,  where  it  is  distributed  by  mixing 
with  the  glosso-pharyngeal.  The  termination  much  resembles  that  of  the  Dog.  Two 
principal  branches  have  been  named  the  temporo-facial  and  the  cervico-facial.  The 
first  receives  the  superficial  temporal  nerve,  and  describes  an  arch  from  which  are 
detiched  the  temporal,  frontal,  palpebral,  suborbital,  and  buccal  ramuscules,  which 
form  the  subparotideal  plexus.  The  second,  lodged  in  the  parotid,  passes  towards  the 
angle  of  the  jaw,  where  it  anastomoses  with  the  cervical  plexus ;  it  furnishes  the  inferior 
bucc.ll,  mental,  and  cervical  branches. 

Glosso-pharyngeal. — This  nerve  commences  and  terminates  as  in  Solipeds,  and  has  the 
same  relations.    It  furnishes  the  branches  of  the  digastric  and  stylo-hyoid  muscles,  the 


746 


THE  NERVES. 


DISTRIBUTION   OP   THE   EIGHTH    PAIR  OF   NERVES  ON   LEFT   SIDE. 

1,  Gasserian  ganglion  of  5th  nerve ;  2,  Internal  carotid  artery ;  3,  Pharyngeal 
branch  of  pueuinogastric ;  4,  Glosso-pharyngeal  nerve ;  5,  Lingual  nerve ;  6, 
Spinal  accessory ;  7,  Middle  constrictor  of  pharynx ;  8,  Jugular  (internal)  vein, 
cut;  9,  Superior  laryngeal  nerve;  10,  Ganglion  of  trunk  of  pneumogastric ;  11, 
Hypoglossal  nerve  on  hyoglossus ;  12,  Ditto  communicating  with  8th  and  1st 
cervical  nerve;  13,  External  laryngeal  nerve;  14,  Second  cervical  looping  with 
the  first,  15,  Pharyngeal  plexus  or  inferior  constrictor;  16,  Superior  cervical 
ganglion  of  sympathetic ;  17,  Superior  cardiac  nerve  of  pneumogastric ;  18, 
Third  cervical  nerve;  19,  Thyroid  body;  20,  Fourth  cervical  nerve;  21,  21, 
Left  recurrent  laryngeal  nerve ;  22,  Spinal  accessory  communicating  with 
cervical  nerves ;  23,  Trachea ;  24,  Middle  cervical  ganglion  of  sympathetic ;  25, 
Middle  cardiac  nerve  of  pneumogastric ;  26,  Phrenic  nerve  (cut) ;  27,  Left 
carotid  artery ;  28,  Brachial  plexus ;  29,  Phrenic  nerve  (cut) ;  30,  Inferior 
cervical  ganglion  of  sympathetic  ;  31,  Pulmonary  plexus  of  pneumogastric ;  32, 
Thoracic  aorta  33,  (Esophageal  plexus;  34,  Vena  azygos  stiperior;  35,  Vena 
azygos  minor  .  36,  Gangliated  cord  of  sympathetic. 


TEE  SFINAL  NERVES.  'j^'j 

filament  of  the  sfyh-ghssus  mmcle,  and,  finally,  the  tonsilitic  ramuscules  that  form,  around 
the  amygdala,  tlie  (onsilar  phxus. 

Pneumogaslric. — Formed  by  the  union  of  the  sensitive  roots,  the  pneumogastric  leaves 
the  cranial  cavity  by  the  posterior  foramen  lacerum ;  in  the  interior  of  that  foramen  it 
shows  the  jugular  ganglion ;  a  little  lower,  it  has  a  second  fusiform  enlargement,  the 
ijanijl  if  arm  plexus,  which  is  found  in  the  Dog.  Here  it  receives  the  internal  branch  of 
the  spinal  accessory,  or  otherwise  its  motor  roots.  Beyond  this  gangliform  enlargement, 
the  pneumogastric  is  placed  a  little  within  the  sympathetic,  descends  along  the  neck, 
enters  the  chest,  and  terminates  on  the  stomach  and  in  the  solar  plexus.  The  relations 
of  the  two  pneumogastrics  in  the  thoracic  cavity  are  th^  same  as  in  animals.  In 
terminating  in  the  semilunar  ganglion,  the  two  pneumogastrics  unite  and  form  an  arch 
named  the  memorable  loop  of  Wrisberg. 

The  various  anastomoses  of  the  pneumogastric  in  IMan  offer  nothing  particular. 

The  ]>haryngeal  branches  leave  the  gangliform  plexus,  and  are  constituted  by  the 
filaments  carried  to  the  pueumoyastric  by  the  internal  root  of  the  spinal  accessory.  They 
are  two,  three,  or  four  in  number,  and  form  the  pharyngeal  plexus. 

The  superior  laryngeal  nerve  also  arises  from  the  gangliform  plexus,  and  offers,  as  in 
Euminants,  a  Galien  branch  that  anastomoses,  end  to  end,  with  a  brancii  of  the  infeiior 
laryngeal.  The  external  laryngeulii  furnished  by  this  nerve;  it  is  distributed  to  the 
inferior  constrictor  muscle  of  the  pliarynx,  the  crico-thyroid  muscle,  and  the  mucous 
membrane  of  the  subglottic  jjortiou  of  the  larynx  and  the  ventricle  of  the  glottis. 

The  recurrent  nerves  atiect  a  distribution  analogous  to  that  already  made  known. 

The  pneumogastric  also  gives  cardiac,  pulmonary,  and  cesopliageal  branches.  The 
cardiac  lie  beside  those  coming  from  the  sympathetic  and  recurrents,  and  enter  the 
ganglion  of  Wrisberg,  situated  at  the  base  of  the  heart.  The  oesophageal  branches  are 
remarkable  for  their  numl:)er  and  complexity,  and  form  a  veritable  oesophageal  plexus. 
The  gastric  branches  are  also  very  numerous. 

Spinal  accessory. — It  presents  bulbous  roots  which  are  well  known,  and  medullary  roots 
which  usually  extend  to  the  fifth  cervical,  and  sometimes  to  the  first  dorsal.  After  its  exit 
from  the  posterior  foramen  lacerum,  it  divides  into  two  branches — an  internal  and  external. 
The  internal  branch,  formed  by  the  bulbous  roots,  enters  the  gangliform  plexus  of  the 
pneumogastric.     The  external  branch  comports  itself  as  in  animals. 

Theliypoglossal  resembles  that  of  Carnivora,  and,  like  it,  possesses  a  branch  for  the 
hyo-thyroideus  and  genio-hyoideus. 


CHAPTER  II. 

SPINAL   NERVES. 

TVe  designate  as  spinal,  vertebral,  or  rachidian  nerves,  those  wliicli  emanate 
from  the  spinal  cord,  and  leave  the  vertebral  canal  by  the  intervertebral 
foramina  to  proceed  to  the  various  organs. 

They  are  estimated  at  42  or  43  pairs,  and  are  apportioned  as  follows  in 
the  five  regions  of  the  spine  :  cervical,  8  pairs  ;  dorsal,  17  pairs  ;  lumbar,  6 
pairs  :  sacral,  o  paii-s  ;  and  coccygeal,  6  to  7  pairs. 

They  differ  from  the  encephalic  nerves  in  closely  resembling  each  other 
in  the  fundamental  points  of  their  constitution.  All  proceed  from  the  lateral 
aspects  of  the  spinal  cord  by  two  orders  of  roots :  one  motor,  the  other 
sensitive  CFig.  317).  In  all,  these  two  roots  imite  in  a  very  short  trunk 
in  passing  through  the  intervertebral  foramen  ;  and  this  trunk  divides  almost 
immediately  into  two  terminal  branches  :  a  superior,  destined  to  the  spinal 
muscles  and  the  integmnents  covering  them  ;  the  other,  inferior,  passes  to 
the  lateral  and  lower  parts  of  the  trunk  or  to  the  members.  All  send,  from 
their  inferior  branch,  one  or  more  ramuscules  to  form  the  great  sympathetic* 

The  roots  of  the  spinal  nerves  offer  everywhere  the  same  disposition ; 
each  nerve  is  formed  by  two  fasciculi  of  converging  filaments,  superior  and 
inferior,  which  are  naturally  more  numerous  and  large  when  they  belong  to 


748 


THE  NERVES. 


Fi^   346 


voluminous  trunks,  as  may  be  remarked  in  those  proceeding  from  the  two 
enlargements  (or  bulbs)  of  the  spinal  cord.  The  common  axis  of  these  two 
fasciculi  affects  a  transverse  direction  in  nearly  all  the  spinal  j)airs ;  but 
that  of  the  posterior  nerves  inclines  more  backwards  as  they  reach  the 
terminal  extremity  of  the  cord. 

The  filaments  of  the  superior  fasciculi,  or  sensitive  roots,  are  larger  than 
the  others,  and  emerge  from  the  collateral  sulcus  of  the  spinal  cord.  They 
may  be  followed  to  the  cells  of  the  superior  grey  cornua. 

The  filaments  of  the  inferior  fasciculi,  or  7notor  roots,  arise  o2:)2iosite 
to  the  preceding,  on  the  lower  face  of  the  cord,  at  a  short  distance  from  the 
middle  line,  and  on  the  limits  of  the  inferior  and  lateral  columns.  They  nsay 
also  be  traced  to  the  interior  of  the  cord,  as  far  as  the  inferior  grey  cornua. 

These  filaments  do  not  miite  to  form  their  common  trimk  until  after 
they  have  passed  through  the  dura  mater ;  this  is  an  extremely  short  trunk 
that  occupies  the  corresponding  intervertebral  foramen,  and  presents  on  its 
upper  face  a  ganglionic  enlargement,  which  is  exclusively  placed  on  the 
course  of  its  sensitive  fibres ;  the  motor  filaments  being  simply  laid 
beside  them,  an<l  do  not  mix  with  them  until  beyond 
the  ganglion.  Immediately  after  this  union,  a  small 
filament  is  given  off  that  enters  the  spinal  canal  to 
be  distributed  to  the  sinuses  and  the  vertebrae. 

After  leaving  the  meningeal  sheath,  the  radicular 
fasciculi  of  the  nerves  fiu'nished  by  the  ternnniil  ex- 
tremity of  the  spinal  cord,  run  a  somewhat  long 
course  in  the  sacral  canal,  before  finally  uniting  and 
passing  into  the  tissues  ;  the  common  fascicules  they 
collectively  form  at  the  posterior  extremity  of  the 
spinal  canal  is  named  the  cauda  equina. 

The  distributive  branches  of  the  spinal  nerves 
cannot  be  considered  in  a  general  manner,  because  of 
their  diversity.  We  will  study  them  successively  in 
each  region  of  the  spine. 

Akticle  I. — Cervical  Nerves  (8  Pairs). 

Superior  Branches. — The  first  passes  through 
the  superior  foramen  of  the  atlas,  in  company  with 
the  cerebro-spinal  artery.  It  arrives  in  the  inter- 
stice between  the  small  oblique  muscle  of  the  head 
and  the  posterior  straight  muscles,  and  divides  imme- 
ferior  root ;  c,  Ganglion  diately  into  several  divergent  branches  which  are 
on   thf.  superior  root;    distributed  to  the   three  above-named   muscles,   the 

d   e,  Junction  of  the  interior  extremity  of  the  great  complexus,  and  the 

nbres  from  the  interior  .  -^  .     '^  ,  ^        rn ' 

and  superior  roots  with  cervico-  and  temporo-auncular  muscles.     ihe  ramus- 

those  coining  from  the  cule  sent  to  the  latter  ascends  within  the  concha,  and 

ganglion .    d,   Superior  breaks  up  into  several  filaments  that  supply  the  skin 

trunk  of  spinal  nerve  ;  ^f  ^^^  external  ear. 

c,  Its  inferior  trunk.  ^m  7    •  t   i  i       ^        •  i 

Ihe  second  immediately  lurnishes  some  ramus- 
cules  to  the  great  oblique  muscle,  beneath  which  it  is  placed,  as  well  as  to 
frlie  small  oblique.  It  is  afterwards  directed  backwards,  comporting  itself 
like  the  succeeding  ones. 

These  diminish  in  volume  from  the  third  to  the  eighth.  All  pass 
through    the    intertransversales-coUi     muscles,   and   divide    into    several 


GANOLION  OF  A  SI'INAL 
NERVE  FROM  THE  LUM- 
BAR REGION  OF  A 
PUPPV. 

Superior   root ;    b.    In- 


•  THE  CERVICAL  NERVES.  749 

branclies,  wliich  are  distributed  to  the  muscles  and  integuments  of  the 
superior  cervical  region.  Among  these,  the  superficial,  which  are  almost 
rudimentary  in  the  two  hist  pairs,  reach  the  inner  face  of  the  splenius.  The 
others,  deep  and  more  voluminous,  cross  the  semispinalis  colli,  and,  dividing, 
ascend  between  the  great  cumjilexus  and  cervical  ligament,  to  near  the 
superior  border  of  that  large  elastic  lamina.  They  generally  intercommimi- 
cate  by  several  filaments,  and  in  this  way  fonn  a  network  on  the  inner  face 
of  the  great  complexus,  which  Girard  named  the  deep  cervical  plexus. 

Infeuior  Branches. — These  branches  augment  in  size  from  the  first  to 
the  last,  and  sej^arate  into  two  perfectly  distinct  groups.  The  divisions  of 
the  first  six  cover  the  lateral  and  anterior  parts  of  the  neck,  as  well  as  the 
muscles  of  the  breast.  Usually  anastomosing  with  each  other  by  long 
communicating  branches,  they  in  this  way  form  a  vast  nervous  network 
traversed  by  two  important  nerves — the  spinal  accessory  and  cervical 
filament  of  the  facial  ;  this  is  the  superficial  cervical  plexus.  The  other  two 
are  united  with  the  preceding  by  a  filament  passing  between  the  sixth  and 
seventh,  soon  becoming  conf(junded  with  each  other,  as  well  as  with  the 
two  first  branches  of  the  dorsal  region  ;  they  constitute,  in  common  with  the 
latter,  the  hracliio.l  plexus. 

Without  saying  any  more  as  to  the  disposition  of  this  double  plexus,  we 
will  pass  to  the  j^articular  description  of  each  cervical  pair  of  nerves. 

First. — Deeply  situated  beneath  the  transverse  process  of  the  atlas,  this 
nerve  leaves  the  anterior  foramen  of  that  vertebra,  and  accompanies  the 
occipital  artery  and  vein  to  place  itself  immediately  between  the  anterior 
small  rectus  capitis  and  rectus  lateralis  muscles.  It  then  crosses  the  anterior 
great  rectus  capitis  and  the  spinal  accessory  nerve,  which  it  separates  ;  and 
arrives,  after  describing  a  slight  curve  forward,  near  the  thyroid  gland, 
finally  entering  the  subscapulo-hyoideus  by  several  terminal  divisions. 

Near  its  origin,  this  inferior  branch  of  the  fii-st  cervical  nerve  furnishes 
collateral  ramuscules  to  the  three  recti  muscles.  Lower,  it  is  in  communica- 
tion with  the  superior  cervical  ganglion  and  the  spinal  accessory  nerve  by 
several  filaments.  At  the  carotid  artery,  it  sends  forwards,  to  the  side  of 
the  larynx,  a  very  fine  branch  that  quickly  divides  into  two  ramuscules,  one 
of  which  joins  the  great  hypoglossal  nerve,  and  the  other  goes  to  the  thyro- 
hyoid muscle.  It  then  throws  ofi",  from  its  convex  side,  several  small  descend- 
ing nerves,  all  of  which  are  destined  to  the  subscapulo-hyoid^  steruo-hyoid, 
and  thyroid  muscles. 

One  of  these  filaments,  joined  by  a  ramuscule  from  the  second  pair,  is 
distinguished  for  its  great  length  ;  it  may  be  followed  to  near  the  sternum, 
where  it  is  expended  in  the  fleshy  mass  common  to  the  four  muscles  that 
extend  from  that  bone  to  the  larynx  and  os  hyoides.  Its  constant  disposition 
should  obtain  for  it  the  name  oi  precervical  nerve. 

Second. — This  descends  beneath  the  great  oblique  muscle  (obliquus 
posticus),  crossing  the  direction  of  the  rectus  anticus  major,  and  ramifying 
therein  by  numerous  branches.  We  specially  indicate  •  1,  Those  furnished 
to  the  latter  muscle,  and  which  are  the  shortest  and  deepest ;  2,  The  atloid 
loop,  a  long,  thick  superficial  branch,  which  enters  the  anterior  portion  of 
the  levator  humeri,  and  is  directed  forward  and  upward  on  the  parotid 
gland,  bending  round  the  transverse  process  of  the  atlas :  this  ramuscule 
gives  ofi"  filaments  to  the  parotido-auricularis,  as  well  as  to  the  subcutaneous 
muscle  of  the  face,  and  terminates  in  two  branches  of  unequal  volume,  the 
largest  of  which  ascends  on  the  outer  side  of  the  concha,  and  the  other, 
situated  behiad,  reaches  the  cervico-auricular  muscles ;  3,  Another  superficial 


750  THE  NERVES.  • 

braucli,  whicli  passes  over  the  jugular,  near  the  junction  of  the  glosso-facial, 
and  divides  into  two  ramuscules ;  these  proceed  forward  with  the  glosso- 
facial  vein  to  the  intermaxillary  space,  where  they  are  distributed  to  the 
skin  and  subcutaneous  muscle  ;  4,  Anastomosing  filaments,  which  unite  it 
to  the  two  branches  of  the  spinal  nerve ;  5,  Accessory  ramuscules  to  the 
cervical  filament  of  the  facial  nerve  ;  6,  Two  communicating  branches 
which  pass  beneath  the  rectus  anticus  major :  one  going  to  the  first,  the  other 
to  the  third  pair  of  nerves ;  7,  A  deep  branch  going  to  join  the  precervical 
filament  of  the  first  2>air,  and  directly  throwing  off  some  fine  divisions  to  the 
subscapulo-hyoid  muscle ;  8,  A  last  branch  that  arises  at  the  intervertebral 
foramen,  and  passes  at  first,  with  the  vertebral  artery,  into  the  trachelian 
(posterior)  foramen  of  the  second  vertebra,  and  afterwards  those  of  the 
succeeding  vertebrae,  to  enter  the  inferior  cervical  ganglion  of  the  great 
sympathetic  nerve,  receiving  on  its  course  filaments  from  the  3rd,  4th,  5th, 
6th,  and  7th  pairs. 

Third,  fourth,  fifth,  and  sixth. — Each  of  these  crosses  the  intertrans- 
versales  colli  by  a  different  interstice  to  that  through  which  the  corresponding 
superior  branch  passes.  They  gain  the  inner  face  of  the  levator  humeri, 
where  they  divide  into  deep  and  sui^erficial  ramifications. 

The  first  are  distributed  to  the  deep  muscles  of  the  sides  and  anterior 
part  of  the  neck  and  shoulders.  Among  them  ought  to  be  distinguished 
those  which  form  a  communication  between  the  four  pairs,  and  the  third 
with  the  second.  Very  long  and  thin,  these  filaments  lie  on  the  side  of  the 
large  muscular  column  formed  in  front  of  the  cervical  stalk  by  the  rectus 
anticus,  longus  colli,  and  scalenus  muscles,  where  they  form  sometimes  arches, 
and  at  other  times  anastomoses  by  convergence.  Those  of  the  fifth  and  sixth 
pairs,  uniting  at  the  anterior  border  of  the  scalenus  with  a  branch  of  the 
brachial  plexus,  constitute  the  diaphragmatic  nerve,  which  will  be  noticed 
hereafter. 

The  superficial  ramuscules  gain  the  external  surface  of  the  levator 
humeri  by  traversing  its  substance,  or  passing  between  its  two  portions. 
Much  more  numerous  and  larger  than  the  preceding,  they  are  distributed, 
in  front,  to  the  subcutaneous  muscle  of  the  neck,  behind,  to  the  trapezius,  or 
below,  to  the  levator  humeri  and  superficial  pectoral.  Those  jiassing  to  the  last 
two  muscles  are  very  long  and  voluminous  ;  they  represent  the  acromial  and 
clavicular  branches  of  the  cervical  plexus  of  Man.  It  may  be  remarked  that 
the  posterior  filaments  generally  communicate  with  the  spinal  accessory, 
while  the  anterior  ones,  in  meeting  the  cervical  branch  of  the  facial  nerve 
on  the  jugular,  often  give  it  some  anastomosing  fibres. 

Seventh. — An  enormous  branch  comes  from  the  interstice  between  the 
two  portions  of  the  scalenus,  to  pass  entirely  into  the  brachial  j^lexus.  It 
usually  receives  an  anastomosing  twig  from  the  diaphragmatic  filament 
fui'nished  by  the  sixth  pair. 

Eighth. — This  is  thicker  than  the  preceding,  and  comports  itself  like  it. 
It  directly  furnishes  its  anastomotic  branch  to  the  inferior  cervical  ganglion. 

Aeticle  II. — Dorsal  Nerves  (17  Pairs). 

These  nerves,  nimibering  seventeen  pairs,  comport  themselves  in  an 
extremely  simple  and  almost  identical  manner ;  so  that  their  description  is 
not  nearly  so  complicated  as  that  of  the  nerves  of  the  cervical  region. 

Superior  Branches. — They  present  two  principal  ramuscules  destined 
to  the  spinal  muscles,  and  to  the  skin  of  the  dorso-lumbar  region.     One 


THE  LUMBAR  NERVES.  751 

ascends  towards  the  summit  of  the  spinous  processes  of  the  doi"sal 
vertebrte,  by  passing  between  the  semispinalis  and  longissimus  dorsi; 
the  other  is  directed  outwards,  in  traversing  the  substance  of  the  latter  muscle. 

Inferior  Branches. — These  are  more  considerable  in  size  than  the 
preceding,  and  descend  into  the  intercostal  spaces,  between  the  pleura  and 
the  internal  intercostal  muscles,  or  even  in  the  texture  of  these.  With  the 
exception  of  the  lirst,  whose  arrangement  is  ditferent,  they  all  pass  at  first 
over  the  head  of  the  posterior  rib  to  reach  the  convex  border  of  the  anterior 
one,  and  follow  it  to  the  extremity  of  the  intercostal  space. 

There  they  terminate  in  the  following  manner :  those  of  the  sternal 
ribs  traverse  the  pectoral  muscles,  giving  filaments  to  these,  and  are 
expended  in  the  skin  of  the  subthoracic  region.  Those  of  the  asternal 
ribs  enter  the  abdominal  muscles,  passing  between  the  transversalis  and 
rectus  abdominis  ;  they  also  give  cutaneous  filaments  to  the  skin  of  the  belly. 

Near  their  origin,  the  inferior  branches  communicate  with  the  great 
symjiathetic,  for  the  most  part,  by  several  filaments. 

In  their  course  they  furnish  numerous  fine  ramuscules  to  the  intercostal 
muscles,  and,  in  addition,  give  off,  about  the  middle  of  their  length,  a  very 
thick  division — the  perfuratimj  intercostal  branch,  which  traverses  the  costal 
muscles  and  descends  beneath  the  panniculus  carnosus,  ramifying  partly  in 
that  muscle  and  jjartly  in  the  skin.  The  most  anterior  perforating  branches 
generally  anastomose  with  the  subcutaneous  thoracic  branch  of  the  brachial 
plexus. 

With  regard  to  the  first  dorsal  pair,  its  ■  inferior  branch  enters  the  latter 
plexus  ;  but  it  nevertheless  furnishes  an  intercostal  branch,  always  extremely 
slender,  which  passes  over  the  external  intercostal  muscle  to  be  expended 
in  its  substance  before  arriving  at  the  sternum.  The  second  pair  also  concurs 
in  the  formation  of  the  brachial  plexus,  though  only  by  a  small  branch. 

Article  III. — Lumbar  Nerves  (6  Pairs). 

Superior  Branches. — Destined  to  the  sjiinal  muscles  and  the  integu- 
ments of  the  loins  and  croup,  these  are  larger  than  the  corresjwnding 
branches  of  the  dorsal  region,  and  present  an  analogous  disposition ;  they 
give  superior  ramuscules  to  the  muscles  of  the  spine,  and  very  long  external 
divisions  which  pass  through  these  muscles  to  be  distributed  to  the  skin  of 
the  croup. 

Inferior  Branches. — The  frst,  comprised  in  the  interval  separating  the 
last  rib  from  the  first  lumbar  transverse  process,  between  the  quadratus 
lumborum  and  the  psoas  magnus,  passes  downwards  and  backwards  until  it  gets 
between  the  transverse  and  internal  oblique  muscles  of  the  abdomen,  to  which 
it  gives  filaments,  and  is  finally  distributed  in  the  great  rectus  muscle. 

Above  the  superior  border  of  the  internal  oblique  muscle,  it  furnishes  a 
perforating  branch  to  the  skin  of  the  flank  and  the  posterior  jjart  of  the 
panniculus  carnosus. 

The  second,  disposed  in  the  same  manner  as  the  preceding,  follows  an 
analogous  course,  and  breaks  up  into  several  divisions  which  are  lost  in 
the  small  oblique  muscle.  From  one  of  these  sometimes  emanates  a  slender 
filament,  which  joins  one  of  the  inguinal  nerves  of  the  third  pair.  We 
must  not  overlook,  in  the  enumeration  of  the  branches  emitted  by  this 
second  pair  of  lumbar  nerves,  the  two  perforating  branches  which  descend 
in  front,  and  on  the  inside,  of  the  thigh,  to  be  distributed  to  the  skin  of  the 
flank  and  the  internal  crural  region. 


752  THE  NERVES. 

The  tJiird,^  also  passes  outwards,  above  the  psoas  muscles,  whicli  receivs 
from  it  several  divisions,  and  ramifies  in  the  muscles  of  the  flank.  It  has 
also  perforating  nerves,  destined  to  the  inguinal  region,  and  these  comport 
themselves  in  a  sufficiently  interesting  manner  to  merit  particular  mention. 
They  are  usually  tbree  in  number :  an  internal  and  two  external  inguinal 
nerves.  The  three  pass  at  first  beneath  the  peritoneum,  and  are  directed 
backwards,  downwards,  and  outwards,  towards  the  inguinal  canal,  which 
they  enter,  one  to  the  inside,  the  other  to  the  outside  of  the  spermatic 
cord.  They  give  off  some  filaments  to  the  cremaster  and  abdominal 
muscles,  and  at  last  ramify  in  the  envelopes  of  the  testicle,  the  sheath, 
and  the  skin  of  the  inguinal  region.  The  two  external  nerves  are  often 
confounded  in  a  single  trunk  on  their  arrival  at  the  cremaster  muscle.  The 
disposition  they  aifect  at  their  origin  is  extremely  variable ;  sometimes  they 
have  each  a  distinct  commencement,  and  separately  traverse  either  the  small 
or  large  psoas  muscle,  or  the  space  between  these  ;  and,  at  other  times,  the 
internal  and  one  of  the  external  inguinal  nerves  proceed  from  a  common 
trunk  at  the  intervertebral  foramen,  the  second  external  nerve  then  arising 
alone  towards  the  external  border  of  the  great  psoas  muscle.  Most  frequently, 
the  internal  nerve  receives  a  branch  from  the  fourth  pair,  and  it-  is  even 
sometimes  entirely  formed  by  that  branch.  This  variation  in  arrangement 
is  not,  however,  the  exclusive  appanage  of  the  inguinal  nerves ;  we  have 
seen  the  third  j^air  only  supply  these  three  nerves  and  the  filaments  of  the 
psoas  muscles,  without  being  prolonged  into  the  muscles  of  the  flank. 

The/oM}-//j-  pierces  the  small  psoas  muscle,  and  enters  the  space  separating 
it  from  its  congener — the  great  2)soas.  After  passing  between  the  peritoneum 
and  the  Inmbo-iliac  aponeurosis,  it  arrives  below  the  angle  of  the  haunch, 
and  makes  its  exit  from  the  abdomen ;  it  then  descends  within,  and  in  front 
of,  the  fascia  lata  muscle,  and  accompanying  the  divisions  of  the  circumflex 
iliac  artery,  it  is  prolonged  to  the  stifle,  where  it  is  expended  in  the  skin. 
At  its  origin,  it  abandons :  1,  A  thick,  short  branch  to  the  great  psoas 
muscle  ;  2,  A  large  anastomosing  branch  which  concurs  in  the  formation  oi 
the  lumbo-sacral  plexus ;  3,  A  filament  that  joins  the  internal  inguinal 
nerve  furnished  by  the  third  pair.  We  have  already  mentioned  that  this 
nerve  sometimes  emanates  entirely  from  the  fourth  pair. 

The  fifth  and  sixth,  much  more  voluminous  than  the  preceding,  unite, 
and,  with  the  three  first  sacral  pairs,  form  the  nervous  jjlexus  of  the 
abdominal  limb. 

All  the  inferior  lumbar  branches  communicate  with  the  great  sympathetic 
by  several  filaments,  which  pass  across  the  fasciculi  of  the  small  psoas  muscle ; 
and  all  communicate  with  each  other :  the  two  last  by  fusion  of  their  fibres, 
and  the  first  five  by  means  of  more  or  less  voluminous  anastomotic  branches 
which  are  far  from  being  constant. 


Article  IV.— Saoral  Nerves  (5  Pairs). 

We  describe,  as  sacral  nerves,  not  only  the  four  double  cords  which 
escape  by  the  lateral  foramina  of  the  os  sacrum,  but  also  the  nerve  that 
passes  through  the  intervertebral  foramen  between  that  bone  and  the  last 
lumbar  vertebra. 

Superior  Branches. — These  are  small  ramuscules  that  pass  through  the 

*  Representing  the  abdomino-cienital  and  femoro-genital  branches  of  Man. 

*  The  femoro-cutaneous  hranch  of  the  lumbar  plexus  of  Man. 


TEE  COMPOSITE  NERVES.  753 

supersacral  foramen,  reach  the  muscles  lodged  on  the  sides  of  the  sacral 
spine,  and  terminate  in  the  skin  of  the  croup. 

Inferior  Branches. — Thick  nervous  trunks,  which  diminish  in  volume 
from  the  first  to  the  fifth,  and  leave  tlie  sacral  canal  to  pass  downwards  and 
backwards  on  the  sides  of  the  pelvic  cavity. 

The  Jirsf,  second,  and  tJiird  are  directed  towards  the  great  ischiatic  openintr, 
and  are  united  into  a  wide  nervous  band  that  constitutes  the  pelvic  portion 
of  the  lumbo-sacral  plexus,  to  be  described  at  another  time. 

The  fourth  and  fifth  course  along  the  side  of  the  pelvic  cavity,  in  the 
texture  of  the  sacro-sciatic  ligament,  or  even  within  it ;  united  at  theii- 
base  by  an  anastomosing  filament,  they  do  not  usually  communicate  in  a 
direct  manner  with  the  fasciculus  formed  by  the  three  first  pairs. 

The  fourth  constitutes  the  internal  pudic  nerve,  which  pusses  between  the 
two  roots  of  the  corpora  cavernosa  in  bending  round  the  ischial  arch,  where 
it  lies  nearly  alongside  its  fellow  of  the  opposite  side.  This  nerve  after- 
wards descends  on  the  dorsal  border  of  the  penis  in  the  midst  of  the  magni- 
ficent venous  plexus  of  that  organ,  describing  flexuosities  which  allow  it  to 
\idapt  itself  to  the  elongation  of  the  penis.  Arriving  at  the  extremity  of  the 
organ,  it  terminates  in  numerous  divisions  in  the  proper  erectile  tissue  of 
this  part,  or  in  the  mucous  membrane  covering  it.  On  its  course  it  emits 
very  long  flexuous  branches,  whose  ultimate  ramifications  enter  the  corpora 
cavernosa,  or  go  to  the  urethral  canal ;  before  leaving  the  pelvis,  it  gives  oif,  be- 
hind, two  thin  ramuscules  destined  to  the  muscles  and  skin  of  the  perineo-anal 
region.  These  ramuscules,  like  the  principal  trunk,  receive  anastomotic  fila- 
ments from  one  of  the  ischio-muscular  branches  of  the  lumbo-sacral  plexus. 

The  fifth  is  the  anal  or  hcemorrhoidal  nerve.  It  passes  backward,  above 
the  preceding,  and  is  distributed  to  the  sphincter  muscle  and  the  surround 
ing  integuments.  Before  quitting  the  pelvis,  it  gives  a  ramuscule  to  the 
levator  ani. 

The  five  inferior  sacral  branches  emit,  near  their  origin,  a  more  or  less 
slender  filament  that  proceeds  to  the  pelvic  or  hypogastric  plexus.  The 
anastomotic  divisions,  through  which  they  communicate  with  the  sympathetic 
chain,  are  generally  thick,  short,  and  multiple. 

Article  V. — CoccYGKAii  Nerves  (6  to  7  Pairs). 

In  the  coccygeal  region  are  found  two  pairs  of  nerves,  one  jilaced 
beneath  the  depressor  muscle  of  the  tail,  the  other  below  the  lateral 
sacro- coccygeal  muscle.  These  two  nerves  extend  to  the  extremity  of  the 
tail,  throwing  off  on  their  track  some  muscular  and  cutaneous  filaments. 
They  are  formed  by  the  superior  and  inferior  branches  of  the  coccygeal 
nerves,  which  gradually  amalgamate  to  form  the  two  trunks. 

These  coccygeal  branches  are  six  or  seven  in  number,  and  very  distinct ; 
they  diminish  in  volume  from  the  first  to  the  last.  The  first  only  gives  a 
slender  filament  for  the  formation  of  each  coccygeal  trunk  ;  it  is  chiefly 
expended  in  the  integuments  and  muscles  at  the  base  of  the  tail. 

Article  VI. — Composite  Nerves  formed  by  the  Inferior  Branches   of 

THE  Spinal  Nerves. 

We  already  know  that  these  nerves  represent  three  groups  :  1,  The 
diaphragmatic  nerve ;  2,  The  brachial  plexus ;  3,  The  lumbosacral  plexus. 
They  will  be  studied  in  this  order. 


754  TEE  NEEVES. 

DIAPHRAGMATIC    (oR    PHRENIc)  NERVE. 

The  diaphragmatic  nerve  (the  internal  respiratory  nerve  of  Bell)  is  formed 
by  two  principal  branches,  and  a  small  accessory  ramuscule  whose  presence 
is  not  constant.  The  latter  comes  from  the  fifth  cervical  pair ;  the  two 
others  proceed,  one  from  the  next  pair,  the  other  from  the  brachial  plexus. 
The  branch  from  the  sixth  pair  pierces  the  infei'ior  scalenus  muscle  from 
within  to  without,  gives  off  a  filament  to  the  brachial  plexus,  and  descends 
obliquely  backwards  to  the  surface  of  the  muscle  it  passes  through,  to  unite, 
at  the  entrance  to  the  chest,  with  the  branch  of  that  plexus.  This  latter 
branch,  generally  shorter  and  thicker,  comes  exclusively  from  the  seventh 
cervical  pair. 

The  trunk  of  the  diaphragmatic  nerve,  formed  in  this  manner,  after 
receiving  the  branch  of  the  fifth  pair — when  it  exists,  passes  within  the 
axillary  artery,  along  with  the  pneumogastric  nerve,  and  often  at  this  point, 
though  not  always,  obtains  a  filament  from  the  great  sympathetic.  It  then 
gains  the  side  of  the  base  of  the  heart,  passing  beneath  the  pleura,  and 
finally  attains  the  phrenic  centre,  after  a  course  of  at  least  eight  inches 
between  the  two  laminae  of  the  posterior  mediastinum — the  left  nerve  being 
in  the  j)roper  mediastinum,  while  that  of  the  right  side  lies  in  the  serous 
septum  intended  for  the  posterior  vena  cava. 

Even  before  its  arrival  at  the  aponeurotic  centre,  this  nerve  divides  into 
several  branches,  whose  ramifications  pass  to  the  sides  of  the  pillars  of  the 
muscle. 

BRACHIAL   PLEXUS. 

This  plexus  comprises  an  enormous  fasciculus  of  nerves,  situated  between 
the  thoracic  parietes  and  the  inner  face  of  the  anterior  member,  formed  by 
the  inferior  branches  of  the  sixth,  seventh  and  eighth  cervical,  and  the  two 
first  dorsal  pairs,  and  principally  destined  to  the  muscles  and  integuments 
of  that  limb. 

Mode  of  constitution. — The  sixth  cervical  pair  only  assists  in  the  forma- 
tion of  this  plexus  by  the  slender  filament  from  its  diaphragmatic  branch ; 
but  the  next  two  are  entirely  devoted  to  it,  as  well  as  the  first  dorsal,  with 
the  exception  of  a  very  thin  ramuscule,  which  constitutes  the  first  intercostal 
nerve.  The  root  furnished  by  the  second  dorsal  pair  only  represents  a  very 
small  part  of  its  inferior  branch,  the  other  portion  forming  a  somewhat 
voluminous  intercostal  nerve. 

The  various  branches  converge  towards  each  other,  and  gain  the  interstice 
between  the  two  portions  of  the  scalenus  muscle  (if  we  consider  it  as  one), 
where  they  unite,  and  become  confounded  into  a  single  fasciculus  by  sending 
filaments  and  ramuscules  to  each  other ,  this  fasciculus  soon  sejiarates  into 
a  certain  number  of  divisions,  whose  disposition  will  be  referred  to  presently. 
It  will  be  remarked  that  the  intercrossing  of  the  branches  composing  the 
brachial  plexus  does  not  occur  in  a  confused  and  irregular  fashion,  and 
if  the  reticulation  of  the  ramuscules  passing  from  one  to  another  does  not 
take  place  in  a  constant  manner,  it  is,  at  any  rate,  far  from  being  inextricable. 
It  is  easy  to  follow  the  filaments  from  any  pair  of  nerves  for  a  certain 
distance  in  the  divisions  given  oif  by  the  brachial  plexus,  especially  after 
maceration  in  dilute  nitric  acid.  This  originating  fasciculus  of  the  brachial 
plexus  is  very  wide  and  short.  It  is  at  first  comprised  between  the  superior 
portion  of  the  scalenus  (or  superior  scalenus)  and  the  longus  colli.  In 
passing  between  the  two  portions  of  that  muscle,  it  bends  round  the  first  rib 


THE  BRACHIAL  FLEXUS.  755 

by  its  posterior  border,  and  corresponds  inwardly  to  the  vertebral  artery  and 
vein,  as  well  as  to  the  nervous  vertebral  filament  proceeding  to  the  sympathetic, 
and  accompanying  these  vessels. 

Mode  of  distribution. — Immediately  after  leaving  the  interspace  in  the 
scalenus,  the  brachial  plexus  arrives  beneath  the  shoulder,  near  the  scapulo- 
humeral angle.  There  it  divides  into  a  certain  number  of  branches,  amongst 
which  it  is  impossible  to  distinguish  the  terminal  divisions  and  collateral 
ramuscules.  VVithout  noticing  this  distinction,  however,  we  will  describe 
them  in  succession,  commencing  with  those  that  pass  to  the  trunk,  and  after- 
wards those  which  are  destined  for  the  limb.  The  latter  will  be  examined 
in  the  following  order :  first,  the  shortest,  or  those  which  proceed  to  the 
upper  parts  of  the  member,  and  next,  the  longest  branches,  or  those  passing 
to  the  foot. 

All  these  divisions  are  named  and  classified  in  the  following  enumera- 
tion : 

1.  Diaphragmatic  branches. 

2.  Angidaris  and  rhomboideal  branch. 

3.  Serratus  magnus  or  superior  thoracic  branch. 

4.  Pectoral  or  inferior  thoracic  branches. 
6.  Subcutaneous  thoracic  branch. 

6.  Latissimus  dorsi  or  great  dorsal  branch. 

7.  Axillary  nerve. 

8.  Adductor  brachii  or  teres  major  branches. 

9.  Subscapidar  branches. 

10.  Super sca'pidar  nerve. 

11.  Anterior  brachial  or  musculo-cutaneous  nerve. 

12.  Radial  nerve. 

13.  Ulnar  or  cubito-cidaneous  nerve. 

14.  Median  or  ctibito-plantar  nerve. 

Preparation  of  the  Brachial  Plexcs. — The  animal  is  placed  in  the  first  position,  and 
slightly  inclined  to  one  side  by  allowing  one  of  the  anterior  limbs  to  hang  un- 
restrained. The  pectoral  muscles  are  then  excised  close  to  their  insertion  in  the  unfixed 
limb,  and  turned  upwards,  maintaining  them  in  this  position  by  the  chain  tentacula 
which  are  detached  superiorly  to  a  band  that  unites  the  extremities  of  the  two 
suspensory  diagonal  bars.  Care  should  be  taken  to  separate  the  pectoralis  magnus  from 
the  panniculis,  in  allowing  the  latter  to  fall  on  the  table  along  with  the  limb.  By  tear- 
ing through  the  considerable  mass  of  cellidar  tissue  surrounding  the  nerves  of  the 
brachial  plexus,  these  soon  appear,  and  may  be  isolated  with  the  greatest  facility.  It  is 
advisable  in  this  dissection  to  preserve  the  arteries ;  and  it  is  alto  of  importance  to  h  ave 
the  perforating  intercostal  branches  intact,  in  order  to  observe  the  anas^moses  of  these 
with  the  subcutaneous  thoracic  division. 

Ill  this  operation,  tlie  anterior  limb  is  very  much  separated  from  the  trunk,  and  the 
relations  of  the  nerves  are  necessarily  more  or  less  changed ;  but  it  exhibits  the  whole  of 
the  plexus  in  the  most  perfect  manner. 

To  trace  the  divisions  of  the  principal  nerves  from  this  plexus,  a  limb  entirely 
removed  from  the  body  is  made  use  of,  and,  if  possible,  with  the  arteries  injected.  The 
nerves  are  then  found  in  their  natural  relations,  and  can  be  more  readily  dissected. 
Figures  347,  348  will  guide  the  student  in  looking  for  these  nervous  divisions. 

1.  Diaphragmatic  Branches. 
See  the  description  of  the  diaphragmatic  nerve  above. 

2.  The  Angidaris  and  Bhomboideal  Branch.     (Fig.  347,  7.) 

Entirely  furnished  by  the  sixth  cervical  pair,  this  branch  is  directed 
upwards  to  the  surface  of  the  angularis  (anterior  portion  of  the  serratus 


756  THE  NERVES. 

magnus).  It  soon  divides  into  several  filaments,  which  arc  wholly  exj^ended 
in  the  substance  of  that  muscle,  the  serratus  magnus,  and  the  rhomboideus. 
The  filament  supplying  the  latter  is  slender  and  very  long,  and,  to  reach  its 
destination,  passes  through  the  angularis. 


3.  Serratus  Magnus,  or  Superior  Thoracic  Branch.     (Fig.  347,  8.) 

This  very  remarkable  branch  proceeds  by  two  principal  portions  from 
the  fasciculus  common  to  all  the  divisions  of  the  brachial  plexus :  one 
emanating  from  the  sixth  cervical  pair ;  the  other  from  the  seventh,  and 
always  traversing  the  last  fasciculus  of  the  scalenus  before  joining  the  first. 
The  single  branch  resulting  from  the  union  of  these  two  roots  is  thin  and 
very  wide.  It  passes  back  to  the  surface  of  the  serratus  magnus,  crossing 
the  direction  of  its  fibres,  and  is  expended  in  its  substance,  sending  regularly- 
arranged  ramifications  upwards  and  downwards. 

This  is  the  respiratory  nerve  of  Bell. 

4.  Pectoral  or  Inferior  Thoracic  Branches. 

Five  principal  are  distinguished : 

1.  One  emanating  from  the  sixth  and  seventh  cervical  pairs,  particularly 
the  former,  and  passing  to  the  intei-nal  face  of  the  sterno-prescapularis  (or 
pectoralis),  to  ramify  exclusively  among  its  fibres,  after  dividing  into  two 
branches :  an  anterior,  short  and  thick,  and  a  jjosterior,  long  and  slender 
(Fig.  347,  10). 

2.  A  second  branch,  arising  from  the  anterior  brachial  and  cubito-plantar, 
or  median  nerves,  by  two  roots,  which  join  in  forming  an  arch  beneath  the 
maxillary  artery. 

It  passes  between  the  two  portions  of  the  deep  pectoral  muscle,  and 
terminates  in  the  superficial  one,  after  furnishing  some  ramuseules  to  the 
pectoralis  magnus  by  means  of  a  long  thin  filament  which  is  carried  back 
to  the  external  surface  of  that  muscle  (Fig.  347,  11). 

3.  The  other  three,  destined  to  the  pectoralis  magnus,  generally  come 
from  the  trunk  that  constitutes  the  subcutaneous  thoracic  branch.  Com- 
prised between  the  serratus  magnus,  and  pectoralis  magnus,  they  are 
directed  downward  and  backward,  and  enter  the  latter  muscle.  One  of  them, 
longer  and  thicker  than  the  other,  follows  the  course  of  the  spur  vein. 

ji 

5  Subcutaneous  Thoracic  Branch.     (Fig.  347,  9.) 

This  is  a  very  remarkable  nerve,  arising  from  the  brachial  plexus  by  a 
trunk  common  to  it  and  the  ulnar  nerve.  Placed  at  first  to  the  inside  of  that 
nerve,  it  soon  leaves  it  to  pass  backward  to  the  internal  face  of  the  caput 
magnum  and  the  panniculus  carnosus.  In  its  long  course,  it  acts  as  a 
satellite  to  the  spur  vein,  above  which  it  is  situated.  It  may  be  followed 
to  the  flank,  where  its  terminal  divisions  are  lost  in  the  substance  of  the 
subcutaneous  muscle.  Those  it  gives  oif  are  also  destined  to  that  muscle  ; 
they  anastomose  with  the  majority  of  the  perforating  intercostal  nerves, 
forming  an  elaborate  network  on  the  inner  face  of  the  panniculus. 

One  of  its  branches,  along  with  a  voluminous  perforating  nerve, 
bends  round  the  inferior  border  of  the  latissimus  dorsi,  and  passes  forward 
to  enter  the  scapulo-humeral  portion  of  the  subcutaneous  muscle. 


THE  BRACHIAL  PLEXUS. 

Fiff.  347. 


757 


NERVES   OF    THE    BRACHIAL    PLEXUS. 


of  that  branch. — A,  Humeral  artery  :  B,  Posterior  radial  artery. 
51 


1,  Diaphragmatic  branch  of 
the  sixth  cervical  pair, 
furnishing  a  branch  to 
the  brachial  plexus ;  2, 
Seventh  cervical  pair ;  3, 
Eighth  cervical  pair ;  4, 
First  dorsal  pair ;  5, 
Second  dorsal  pair;  6, 
Great  dorsal  branch ;  7, 
Angularis  and  rhomboid- 
eal  branch ;  8,  Superior 
thoracic  branch  ;  9,  Sub- 
cutaneous thoracic  branch, 
giving  rise,  near  its  origin, 
to  the  three  inferior  tho- 
racic branches ;  12,  Nerve 
of  the  adductor  of  the 
arm  ;  1 3,  Axillary  nerve  ; 

14,  Subscapular    nerves ; 

15,  Superscapular  nerve; 

16,  Radial  nerve;  17, 
Anterior  brachial  nerve ; 
18,  Ulnar  nerve;  19,  Its 
internal  cutaneous  branch ; 
20,  Median  nerve;  21, 
Its  antibrachial  musculo- 
cutaneous branch ;  22,  22, 
22,  Superficial  ramuscules 


758  TEE  NERVES. 

6.  Great  Dorsal  Branch.     (Fig.  347,  6.) 

Formed  of  fibres,  the  larger  portion  of  which  come  from  the  eighth 
cervical  pair,  this  branch  proceeds  backwards  and  upwards  to  the  internal 
face  of  the  latissimus  dorsi,  and  is  soon  expended  in  that  muscle.  It  is  long 
and  thick. 

7.  Axillary  or  Circuwjiex  Nerve.    (Fig.  347,  13.) 

Somewhat  considerable  in  volume,  this  nerve  is  furnished  directly  by  the 
eighth  cervical  pair.  It  passes  backward  and  downward  on  the  internal 
face  of  the  subscapularis  muscle,  to  the  interstice  between  it  and  the  adductor 
of  the  arm,  where  it  crosses  the  subscapular  artery.  It  proceeds  behind 
the  scapulo-humeral  articulation,  along  with  the  circumflex  artery,  enters 
betwedh  the  short  abductor  of  the  arm  and  the  caput  magnum  and  medium, 
and  arriving  beneath  the  abductor  brachii,  it  divides  into  several  diverging 
branches,  destined  to  the  two  abductors,  the  levator  humeri,  and  even  to  the 
integuments  covering  the  anterior  region  of  the  arm. 

Before  entering  the  space  that  lodges  the  subscapular  artery,  it  sends 
filaments  to  the  teres  internus. 

8.  Nerve  of  the  Adductor  of  the  Armor  Teres  Major.    (Fig.  347,  12.) 
This  arises  from  the  eighth   cervical  pair,  like  the   preceding,  by  the 
same  trunk,  and  passes    backward,  at   first  on   the  subscapularis  muscle, 
then  the  adductor,  in  the  substance  of  which  it  disappears  by  numerous 
filaments. 

9.  Subscapular  Branches.    (Fig.  347,  14.) 

These  branches  are  two  in  number,  and  are  generally  derived  from  the 
trunk  of  the  seventh  pair.  After  a  short  course  backwards,  they  divide 
into  several  ramuscules  which  pass  among  the  fibres  of  the  subscapularis 
muscle. 

10.  Superscapular  Nerve.    (Fig,  347,  15). 

Very  short  and  thick,  this  nerve  is  formed  by  the  sixth  and  seventh 
cervical  pairs.  After  a  brief  course  backwards,  between  the  angularis  on 
the  one  side,  and  the  pectoralis  prescapularis  and  superspinatus  on  the 
other,  it  gains  the  space  between  the  latter  muscle  and  the  subscapularis, 
and  enters  it  a  little  above  the  super-  or  prescapular  artery.  It  is  then 
carried  to  the  external  face  of  the  scapula,  after  bending  round  the  anterior 
border  of  that  bone,  passes  across  the  acromion  spine,  and  ascends  to  the 
subspinous  fossa,  to  expend  itself  in  the  muscle  occupying  this  space.  On  its 
passage  beneath  the  superspinatus,  it  gives  ofi"  several  ramuscules  to  that 
muscle. 

11.   Anterior  Brachial  or  Musculo-cutaneoiis  Nerve.     (Fig.  347,  17.) 

This  nerve  proceeds  from  the  seventh  and  eighth  cervical  pairs,  descends 
to  the  internal  face  of  the  scapulo-humeral  articulation,  and  meets  the 
axillary  artery,  which  it  crosses  outwardly,  at  an  acute  angle.  It  then 
joins  the  median  nerve  by  a  large  short  branch,  that  passes  beneath  the 
artery  and  forms  a  loop  around  it ;  descending  in  front  of  the  median 
nerve,  to  the  bifurcation  of  the  coraco-humeralis,  it  insinuates  itself  between 
the  two  branches  of  that  muscle,  and  breaking  up  into  several  ascending 


THE  BRACHIAL  PLEXUS. 


759 


and  descending  ramuscules, 
enters  the  substance  of  the 
coraco-radialis.  It  also  fur- 
nishes filaments  to  the  coraco- 
humeralis,  before  its  passage 
between  the  two  branches  of 
that  muscle.  Besides  this,  it 
concurs,  by  a  small  branch,  in 
the  formation  of  one  of  the 
anterior  thoracic  nerves. 


12.  Badial  Nerve.    (Figs.  347, 
16  ;  348,  3.) 

This  is  certainly  the  largest 
nerve  furnished  by  the  brachial 
plexus.  It  arises  chiefly  from 
the  first  dorsal  pair,  and  is 
directed  backwards  and  down- 
wards, on  the  inner  face  of  the 
subscapularis  and  adductor  mus- 
cle of  the  arm,  whose  direction 
it  crosses.  In  this  portion  of  its 
course,  it  proceeds  parallel  to 
the  humeral  artery,  from  which 
it  is  separated  by  the  ulnar 
nerve.  Arriving  at  the  deep 
humeral  artery,  which  it  leaves 
on  the  outside,  it  passes  behind 
the  humerus  with  the  divisions 
of  that  artery,  and  enters  be- 
tween the  large  extensor  and 
short  flexor  of  the  fore-arm. 
After  creeping  along  the  pos- 
terior border  of  the  latter 
muscle,  it  gains  the  anterior 
face  of  the  ulnar  and  radial  ar- 
ticulations, where  it  is  covered 
by  the  two  principal  extensors 
of  the  metacarpus  and  the  pha- 
langes, and  meeting  the  radial 
artery,  accompanies  it  on  to  the 
oblique  extensor  of  the  meta- 
carpus. There  it  terminates  by 
two  branches  whicli  enter  the 
texture  of  that  muscle. 

1,  Subscapular  nerve ;  2,  Axil- 
lary nerve  ;  3,  Radial  nerve  ;  4, 
Superficial  ramuscule  of  the 
musculo-cutaneous  nerve ;  5, 
Ulnar  nerve ;  6,  Its  terminal 
cutaneous  branch. — A,  Anterior 
radial  artery. 


Ficr.  348. 


EXTERXAL   NERVES  OF  THE   ANTERIOR   LIMB. 


760  THE  NERVES 

In  its  course,  it  successively  gives  off: 

1.  Before  leaving  the  internal  face  of  the  limb,  to  pass  beneath  the  mass 
of  extensor  muscles  of  the  fore-arm,  a  very  thick  fasciculus,  composed  of 
several  branches — descending  and  ascending.  The  latter  bend  round  the 
terminal  tendon  common  to  the  latissimus  dorsi  and  teres  intern  us,  to 
become  lost  in  the  body  of  the  great  extensor ;  the  others  reach  either  the 
long  and  middle  extensors,  or  the  inferior  portion  of  the  principal  muscle — 
the  large  extensor. 

2.  Behind  the  arm,  filaments  to  the  short  and  small  extensors  of  the 
fore-arm,  and  several  cutaneous  ramuscules,  disengaged  from  beneath  the 
short  extensor,  that  descend  beneath  the  skin  on  the  anterior  face  of  that 

part. 

3.  In  the  antibrachial  region,  branches  to  the  anterior  extensor  and 
external  flexor  of  the  metacarpus,  and  the  two  extensors  of  the  digit. 

In  brief,  we  see  that  the  radial  nerve  animates  the  whole  mass  of  the 
extensor  muscles  of  the  fore-arm  and  foot,  besides  a  flexor  of  the  latter,  and 
that  it  endows  the  integument  of  the  anterior  antibrachial  region  with 
sensibility. 

13.  Ulnar,  or  Cubito-cutaneous  Nerve.     (Figs.  347,  18  ;  348,  5.) 

Chiefly  formed  by  fibres  from  the  dorsal  pairs,  this  nerve,  less  consider- 
able in  volume  than  the  preceding,  proceeds  backward  and  downward,  and 
places  itself  behind  the  humeral  artery,  which  it  accompanies  to  below  the 
origin  of  the  deep  humeral.  After  crossing  the  latter  vessel,  it  passes 
between  the  long  and  middle  extensors  of  the  fore-arm,  and  gains  the  inner 
side  of  the  elbow,  running  over  the  epicondyle,  below  the  ulnar  band  of 
the  oblique  flexor  of  the  metacarj)us.  It  follows  the  posterior  border  of  that 
muscle  to  near  the  supercarpal  or  pisiform  bone,  where  it  terminates  by 
two  branches.  In  the  latter  part  of  its  course,  it  lies  beneath  the  anti- 
brachial aponeurosis,  accompanied  by  a  division  of  the  epicondyloid 
artery. 

One  of  the  two  branches,  the  cutaneous  (Fig.  348,  6),  crosses  the  space 
between  the  terminal  tendons  of  the  external  and  oblique  flexor  muscles  of 
the  metacarpus,  as  well  as  the  antibrachial  aponeurosis,  to  spread  itself  in 
several  ascending  horizontal  and  descending  filaments,  beneath  the  skin  of  the 
fore-arm,  the  anterior  face  of  the  knee,  and  the  external  side  of  the  cannon. 
Tlie  other  branch,  with  a  ramuscule  from  the  median  nerve,  constitutes  the 
external  'plantar  nerve. 

In  its  com'se,  the  ulnar  nerve  gives  off  two  fasciculi  of  collateral  branches. 
The  first  (Fig.  347,  19)  is  detached  from  the  principal  trunk  a  little  above 
the  epicondyloid  artery,  and  passes  backward  and  downward  between  the 
long  extensor  of  the  fore-arm  and  the  pectoralis  transversus,  supplying  some 
filaments  to  the  latter,  and  traverses  it  to  become  subcutaneous,  and  to  be 
distributed  to  the  skin  of  the  fore-arm,  beneath  the  elbow.  The  second 
arises  at  the  epicondyle,  and  is  destined  to  all  the  muscles  of  the  posterior 
antibrachial  region,  except  the  external  and  internal  flexors  of  the 
metacarpus. 

14.  Median,  or  Cuhito-plantar  Nerve.    (Fig.  347,  20.) 

This  nerve  is  composed  of  fibres  coming  from  the  dorsal  and  eighth 
cervical  pairs.  It  is  detached  from  the  posterior  part  of  the  trunk  of  the 
plexus  to  proceed  to  the  axillary  artery,  where  it  forms  an  anastomosis  with 


THE  BRA  CHIAL  PLEXUS.  761 

the  anterior  brachial  nerve,  through  the  loop  already  noticed  when  describing 
that  nerve  as  being  formed  by  filaments  passing  from  one  cord  to  the  other. 

Leaving  this  point,  it  is  placed  in  front  of  the  humeral  artery,  and 
accompanies  it  to  its  terminal  bifurcation  ;  then  it  continues  to  descend  on 
the  inner  face  of  the  limb,  along  with  the  principal  branch  of  that  artery — 
the  posterior  radial — until  it  reaches  the  idnar  articulation,  where  it  responds 
to  the  internal  ligament  of  that  joint,  and  where  it  crosses,  at  a  very 
acute  angle,  the  direction  of  its  satellite  vessel  to  become  posterior.  This 
position  it  inverts  below  the  articulation,  when  it  assumes,  and  preserves  for 
the  greatest  part  of  its  extent,  its  antibrachial  course,  remaining  always  a 
little  more  superficial  than  the  artery.  Above  the  lower  thu-d  of  the  fore- 
arm, it  bifurcates  to  form  the  plantar  nerves. 

In  its  course,  this  nerve  successively  furnishes  : 

1.  Before  its  arrival  on  the  axillary  artery,  one  of  the  originating 
branches  of  the  thoracic  nerve  destined  to  the  superficial  pectoral  muscle. 

2.  At  the  middle  of  the  humerus,  a  long  branch,  represented  in  Man  by 
that  portion  of  the  musculo-cutaneous  nerve  which  proceeds  to  the  anterior 
brachial  muscle  and  the  skin  of  the  fore-arm.  This  branch  enters  beneath 
the  coraco-radialis  or  biceps,  and  forms  two  divisions;  one  of  which  is 
expended  in  the  short  flexor  of  the  fore- arm ;  while  the  other  passes 
between  that  muscle  and  its  congener,  the  long  flexor,  to  become  superficial 
and  gain  the  internal  aspect  of  the  limb,  when  it  breaks  up  into  two 
principal  filaments,  which  pass  to  the  external  face  of  the  antibrachial 
aponeurosis,  and  accompany  with  their  divisions  the  two  subcutaneous 
veins  of  the  fore-arm  to  below  the  carpal  region  (Fig.  347,  21,  22). 

3.  In  the  antibrachial  region,  and  at  various  elevations,  but  particularly 
below  the  ulnar  articulation,  ramifications  to  the  internal  flexor  of  the 
metacarpus  and  the  two  flexors  of  the  phalanges. 

Plantar  Nerves. — These  nerves,  two  in  number,  are  distinguished  as 
internal  and  external. 

The  internal  plantar  nerve,  one  of  the  terminal  branches  of  the  median 
nerve,  lies  beside  the  collateral  artery  of  the  cannon,  and  follows  that  vessel 
along  the  perforans  tendon  to  near  the  fetlock,  where  it  ends  in  several 
digital  branches.  In  its  track  it  furnishes  a  number  of  cutaneous  metacarpal 
ramuscules,  and  an  anastomosing  branch,  which,  after  being  detached  from  the 
principal  trunk,  about  the  middle  of  the  cannon,  bends  obliquely  behind  the 
flexor  tendons  to  join  the  external  plantar  nerve.  This  is  formed  by  the 
union  of  two  branches:  one  coming  from  the  ulnar  nerve,  the  other  from 
the  median,  and  joining  the  first  at  the  upper  border  of  the  pisiform  bone, 
after  passing  beneath  the  inferior  extremity  of  the  oblique  flexor  of  the 
metacarpus.  This  nerve,  which  accompanies  the  external  collateral  vein  of 
the  cannon  for  its  entire  length,  descends  with  it,  and  with  an  arteriole  that 
concurs  in  forming  the  subcarpal  arch,  outside  the  flexor  tendons,  in  a 
special  fibrous  channel  of  the  carpal  sheath.  Near  the  superior  extremity  of 
the  cannon,  within  the  head  of  the  external  metacarpal  bone,  it  sends  on 
the  posterior  face  of  the  suspensory  ligament  of  the  fetlock  a  deep  plantar 
branch,  chiefly  destined  to  the  fleshy  portion  of  the  interosseous  muscles. 
It  is  the  analogue  of  the  deep  palmar  branch  of  the  ulnar  nerve  in  Man, 
Continuing  its  descending  course  along  the  perforans  tendon,  it  throws  off 
some  superficial  metacarpal  ramuscules,  receives  the  accessory  branch 
supplied  by  the  internal  nerve,  and  terminates,  like  the  latter,  in  a  number 
of  digital  branches  on  arriving  at  the  fetlock ;  these  it  now  remains  for  us 
to  examine. 


762 


TEE  NERVES. 


The  digital  branches,  or  collaterals  of  the  digit,  and  the  terminal  branches 
of  the  plantar  nerves,  are  three  in  number  on  each  side,  and  accompany  the 
digital  artery  and  vein,  which,  at  some  points,  they  cover  with  their  divisions. 

Fig.  349. 


NERVES  OF   THE   DIGIT. 

P,  Plantar  nerve;  b,  Median  branch;  c,  Anterior  branch;  d,  Digital  artery  If 
Inconstant  division  given  ofF  to  the  cartilaginous  bulbs;  i,  i,  Branch  to 'the' 
plantar  cushion ;  K,  Transverse  coronary  branch ;  M,  Podophyllous  branch ;  o 
^replantar  branch  ;  q,  Descending  ramuscule  to  the  fissure  of  the  patilobes  •  R 
Ramuscules  accompanying  the  digital  artery  in  the  plantar  fissure;  v,  Vein 
whose  presence  is  not  constant,  and  which  sometimes  accompanies  the  plantar 
nerve  throughout  its  phalangeal  course. 


THE  BRACHIAL  PLEXUS.  7d3 

They  separate  from  one  another  nearly  at  tlie  insertion  of  the  suspensory 
ligament  into  the  sesamoid  bones.  One  of  them  descends  in  front  of  the 
vein  ;  another  passes  between  the  two  vessels  ;  while  the  third  follows  the 
artery  behind.  They  may,  therefore,  be  distinguished,  according  to  their 
position,  into  anterior,  middle,  and  posterior  (Fig.  349,  m,  o,  r). 

The  anterior  branch  distributes  its  collateral  divisions  to  the  skin  on  the 
anterior  face  of  the  digit,  and  its  terminal  ramuscules  in  the  coronary 
cushion. 

The  middle  branch  frequently  anastomoses  with  the  other  two,  par- 
ticularly with  the  anterior,  and  to  such  a  degree  as  to  be  scarcely  dis- 
tinguished from  it ;  it  enters  the  coronary  cushion  and  the  podophyllous 
tissue. 

The  posterior  branch,  much  more  considerable  than  the  preceding,  and  a 
veritable  continuation  of  the  plantar  nerve,  is  at  first  superposed  on  the 
digital  artery,  then  it  is  placed  immediately  behind  that  vessel.  It  descends 
with  it  to  near  the  basilar  process  of  tlie  third  phalanx,  follows  the  pre- 
j)lantar  uugueal  artery  into  the  lateral  fissure  of  that  phalanx,  and,  like  that 
vessel,  expends  itself  in  the  midst  of  the  podophyllous  tissue,  as  well  as  in  the 
osseous  structure.  This  branch  gives  ofi"  numerous  ramuscules  on  its  course. 
Of  these  there  may  be  more  particularly  noticed :  1,  Some  posterior 
divisions,  distributed  behind  the  flexor  tendons,  especially  at  the  fetlock; 
2,  A  satellite  branch  to  the  artery  of  the  plantar  cushion  ;  3,  A  filament 
arising  below  the  lateral  cartilage,  passing  forward,  in  proximity  to  the 
anterior  branch  of  the  arterial  coronary  circle,  and  becoming  lost  in  tlie 
meshes  of  the  deep  venous  network  of  the  cartilage  ;  4,  A  small  podo- 
pliyllous  division,  whose  point  of  origin  is  placed  at  the  same  height  as  the 
preceding  filament,  but  opposite  it,  aud  which  descends  on  the  retrossal 
process,  where  it  traverses  the  cartilaginous  tissue  to  pass  to  the  podo- 
phyllous reticulation,  after  distributing  posterior  ramuscules  to  the  plantar 
cushion  ;  5,  Several  extremely  fine  filaments  enlaced  around  the  plantar 
ungueal  artery,  and  with  it  penetrating  to  the  interior  of  the  os  pedis ;  some 
of  these  filaments  ascend  to  the  nerve  of  the  opposite  side.^ 

DIFFERENTIAL   CHARACTERS   IN  THE   BRACHIAL   PLEXUS   OF  OTHER   THAN   SOLIPED  ANIMALS. 

lu  the  domesticated  mammals,  the  nerves  of  the  brachial  plexus  do  not  offer  any  very 
imiiortant  differences  in  the  upper  part  of  the  limb;  these  only  become  apparent  in  its 
last  section. 

EuMiNANTs. — The  branches  of  the  plexus,  the  same  in  number  as  in  the  Horse,  are 
relatively  more  voluminous  than  in  tijat  animal.  In  the  Ox  they  are  often  fiesuous  in 
their  upper  part.  In  tlie  Shee]),  we  have  found  that  the  diaphragviatic  nerve  is  formed 
by  a  single  filament,  detached  from  the  branch  the  sixth  cervical  nerve  gives  to  the 
brachial  plexus.  There  are  no  differences  to  signalise  in  the  branch  of  the  angular  is  and 
rhomboideus,  in  the  branches  of  the  pectoral  muscles,  the  subcutaneous  thoracic  branch, 
or  the  anterior  brachial  or  musculo-cutaneous  nerve. 


'  It  is  because  we  conform  to  established  usages,  and  are  unwilling  to  force  analogies, 
that  we  preserve  the  designations  of  "plantar  nerves,"'  and  "digital  brandies,"  as  well 
as  the  above  manner  of  describing  them.  Comparative  anatomy  desires  other  names  and 
a  different  description  ;  for  it  demonstrates  that  the  external  plantar  nerve  corresponds 
to  the  interosseous  of  the  first  space  in  pentadactylous  animals :  the  internal  plantar  to 
the  interosseous"  of  the  third  space,  aud  the  branch  extending  from  the  internal  to  the 
external  plantar,  to  the  interosseous  of  the  second  space,  and  which  only  virtually  exists 
in  the  Horse,  in  consequence  of  the  fusion  of  the  second  and  third  metacarpal  bone,  and 
which  is  prolonged  to  the  phalanges.  It  also  shows  that  the  digital  branches  are  the 
exact  representatives  of  the  collaterals  of  the  digits  whioh  result, "in  the  pentadactylous 
siiecies,  from  a  bifurcation  of  tach  interosseous  uerve. 


764 


THE  NERVES. 


The  nerve  of  the  serratus  magnus  does  not  show  the  branch  which,  in  the  Horse, 
arises  from  the  sixth  nerve  and  passes  through  the  scalenus ;  but  on  the  surface  of  the 
serratus  magnus  it  receives  a  filament  from  the  branch  of  the  angularis.  The  latter  is 
detached  from  the  sixth.  ^       ,,,.-,    . 

The  branch  of  the  great  dorsal  muscle  and  the  axillary  nerve  are  confounded  at  their 
origin   and  also  adliere  to  one  of  the  two  branches  of  the  subscapularis  nerve.     The 


Fis.  350. 


NERVES  OF   THE   DIGITAL   REGION   OF   RUMINANTS;    POSTERIOR  FACE.' 

M,  Internal  plantar  nerve,  a  continuation  of  the  median  ;  C,  Internal  plantar  nerve, 
a  continuation  of  the  ulnar ;  1,  Branch  of  the  plantar,  furnishing,  2,  the  internal 
collateral  nerve  of  the  internal  digit ;  3,  Branch  giving  off  the  intern.-vl  collaterals 
of  the  digits;  1',  Branch  of  the  internal  plantar  that  joins  the  external  plantar; 
4,  External  collateral  of  the  external  digit. 

second  branch  of  the  latter  is  free  throughout,  and  distributed  in  the  muscle  of  the  same 
name,  along  with  some  filaments  furnished  by  the  superscapularis. 

The  radial  nerve,  when  it  reaches  the  teres  major,  divides  into  three  branches :  one  is 


THE  BRACHIAL  PLEXUS,  7G5 

buried  in  the  long  extensor  of  the  fore-arm;  the  other  traverses  the  middle  extensor; 
and  the  third  is  Inflected  on  the  tendon  of  the  great  dorsal  muscle,  and  passes  between 
the  middle  and  large  extensor  of  the  fore-arm.  When  the  radial  nerve  turns  outwardu 
aroimd  the  arm,  and  is  placed  between  the  anterior  brachial  and  the  mass  of  the 
olecranian  muscles,  it  furnishes :  1,  Muscular  branches  that  pass  immediately  beneath 
the  extensors  of  the  metacarpus  and  phalanges  ;  2,  A  sensitive  branch  tliat  leaves  1his 
muscular  interstice  to  become  subcutaneous.  This  cutaneous  branch  of  the  radial  gains 
the  inner  face  of  the  fore-arm,  and  divides  in  two  branches  that  descend  parallel  to  the 
median  subcutaneous  vein.  One  of  these  is  lost  around  the  carpus ;  the  other  is  placed 
a  little  in  front  of  the  metacarpus,  and  reaches  the  metacarpo-phalangeal  articulation, 
■where  it  tenuinates  by  two  principal  filaments  that  constitute  the  dorsal  coUateraJs  of  the 
digits;  there  is  a  third  which  crosses  the  interdigital  to  anastomose  with  the  palmar 
collaterals. 

The  ulnar  and  median  nerve  of  Ruminants  lie  beside  each  other,  as  far  as  the  middle 
of  the  arm.  This  double  cord  is  situated  at  the  surface  of  the  humeral  artery  ;  at  the 
carpus  the  two  nerves  ofl'er  the  same  distribution  as  in  the  Horse,  but  beyond  this  there 
are  some  differences. 

The  ulnar  does  not  receive  a  branch  from  the  median  at  the  carpus,  and  it  forms  the 
external  plantar  nerve  or  interosseous  palmar  of  the  first  space,  placed  at  the  external 
border  of  the  flexor  tendous.  This  nerve  is  reinforced  by  a  filament  detached  from  the 
external  plantar,  that  joins  it  a  little  above  the  fetlock-joint ;  it  gives  ramiiscules  to  the 
ergot,  and  is  then  continued  by  the  external  collateral  nerve  of  the  outer  digit,  into  the 
horny  claw. 

The  median  is  continued  by  the  internal  plantar,  or  interosseous  palmar  of  the  third 
space.  Towards  tlie  inferior  third  of  the  metacarpus,  it  divides  into  three  branches :  ihe 
third  passes  to  the  external  plantar  ;  the  second  proceeds  to  the  interdigital  space,  where 
it  bifurcates  to  form  the  internal  collateral  palmar  nerves  of  the  external  digit,  and  external 
collateral  of  the  internal  digit ;  the  third  gives  some  filaments  to  the  ergot,  and  passes 
along  the  digital  region,  where  it  constitutes  the  internal  collateral  of  the  internal  digit. 

Pig. — Three  fasciculi  are  detached  from  the  brachial  pleXus ;  the  posterior  is  the 
most  voluminous,  and  furnishes  the  radial,  median,  and  cubital. 

The  branches  of  the  plexus  that  pass  to  the  trvnik  and  the  first  rays  of  the  anterior 
limb  much  resemble  those  of  Euminants;  the  branch  of  the  serratus  magnus  is  remarkable 
for  its  length  and  size. 

The  median  nerve  is  disposed  like  that  of  Solipeds  and  Euminants.  as  far  as  the  carpus ; 
from  this  point  it  passes  beneath  the  flexor  tendons  of  the  phalanges,  gives  filaments  to 
the  interosseous  palmar  muscles,  and  at  the  two  rudimentary  digits  divides  into  four 
branches :  the  two  upper  are  the  smallest,  and  form  the  collaterals  of  thi-  rudimentary 
digits ;  the  inferior  two  are  the  longest,  and  reach  the  principal  interdigital  space, 
forming  the  collaterals  of  the  two  great  digits. 

The  rdnar  gives  off,  towards  the  middle  of  the  arm,  a  branch  that  passes  to  f he  ulna ; 
at  the  ulna  it  furnishes  several  muscular  branches.  The  nerve  then  bends  round  to  the 
outside  of  the  fore-arm,  and  on  arriving  above  the  pisiform  bone,  bifurcates :  one  branch 
^oes  idong  the  outer  border  of  the  flexor  tendons,  and  is  continued  by  the  collateral  of  the 
external  digit ;  the  other  is  placed  on  the  anterior  face  of  the  metacarjius,  and  also 
bifurcates  to  give  the  external  digits  their  dorsal  collateral  nerves. 

Caknivora. — The  i'our  last  cervical  and  first  dorsal  compose  the  brachial  plexus  in  the 
Carnivora ;  the  fifth  cervical  gives  an  insignificant  filament.  When  the  plexus  is  un- 
ravelled, its  principal  branches  are  observed  to  send  fibres  to  each  other. 

The  number  of  the  distributive  branches  is  the  same  as  in  Solipeds,  and  the  dis- 
position of  the  superior  branches  is  so  analogous  as  to  call  for  no  remark ;  so  we  will 
only  describe  the  anterior  brachial,  radial,  median  and  cubital  nerve. 

The  anterior  hrachiid,  or  musculo-cutaneous,  is  constituted  by  a  filament  from  the  sixth 
cervical  and  the  more  voluminous  branches  coming  from  the  seventh.  Placed  in  front  of 
the  axillary  artery,  this  cord  arrives  at  the  scapulo-humeral  articulation,  where  it 
bifurcates ;  one  of  the  branches  passes  forward  to  the  biceps  ;  the  other  remains  alongside 
the  anterior  border  of  the  humeral  artery,  and  terminates  by  a  slightly  recurrent  branch 
that  is  buried  in  the  anterior  brachial  muscle,  and  by  a  very  fine  fi'araent  that  becomes 
subcutaneous  at  the  elbow,  and  descends  on  the  inner  border  of  the  fore-arm  to  be  lost 
in  the  vicinity  of  the  carpus.  The  anterior  brachial  is,  therefore,  in  these  animals,  a 
musculo-cutaneous  nerve.  The  branch  unitinsr  it  to  the  median  nerve  is  situated  a  little 
below  the  middle  of  the  humerus,  instead  of  being  beneath  the  axillary  artery,  as  in 
Solipeds. 

The  radial  nerve,  in  the  Dog,  is  exclusively  formed  by  the  eighth  cervical ;  it  receives 
filaments  from  the  median,  ulnar,  and  axillary  nerve,  and  gives  branches  to  these  three. 


766 


THE  NERVES. 


When  it  reaches  the  interstice  of  the  triceps  and  anterior  brachial,  it  crosses  the  limb 
alxjve  the  outer  face  of  the  elbow,  and  divides  into  two  series  of  terminal  branches. 

The    muscular  branch   enters   beneath 


Ficr.  351. 


the  muscles  on  the  anterior  face  of  the  fore- 
arm. The  cutaneous  bifurcates  imme- 
diately :  the  smallest  branch,  passing  in- 
wards, extends  beyond  tlie  bend  of  the 
elbow,  lies  at  the  inner  border  of  the  median 
subcutaneous  vein,  and  is  distributed  to  the 
lower  moiety  of  the  fore-arm,  the  thumb, 
and  internal  border  of  the  index  digit.  The 
largest  )ies  at  the  outer  side  of  the  median 
subcutaneous  vein ;  it  sends  a  recurrent 
ramuscule  to  the  bend  of  the  elbow,  and,  at 
the  elbow,  detaches  three  filaments  to  the 
first,  second,  and  third  dorsal  intermeta- 
carpal spaces ;  these  filaments  bifurcate  at 
the  dorsum  of  the  digits  1o  constitute  the  col- 
lateral dorsal  ncrces.  The  first  metacarpal 
nerve  anastomoses,  by  a  fine  transverse 
branch,  with  the  ulnar  ramuscule  that 
constitutes  the  external  dorsal  collateral  of 
the  small  digit. 

To  resume  :  the  radial  of  the  Dog  gives 
branches  to  the  dorsal  face  of  all  the  digits, 
except  the  external  border  of  the  first  digit, 
or  auricular!  s. 

In  the  Cdf,  there  are  some  differences. 
The  internal  branch  of  the  radial  sometimes 
lies  with  the  external  branch  ;  it  is  placed 
at  the  inner  border  of  the  metacarpus,  gives 
otl'  a  filament  to  the  dorsal  face  of  the  tliumb, 
and  afterwards  forms  the  internal  dors'il 
collateral  nerve  of  the  index.  The  external 
branch  leaves  the  anterior  face  of  the  carpus, 
and  is  situated  at  the  origin  of  the  third 
interosseous  space,  where  it  divides  in'o 
three  metacarpal  branches ;  the  external  of 
these  is  very  fine,  and  directed  obliquelv 
outwards,  anastomosing  with  the  dorsal 
branch  of  the  ulnar,  between  the  first  and 
second  digits. 

The  median  of  the  Dog  is  united  to  the 
ulnar  as  far  as  the  lower  fourth  of  the  arm ; 
branches;  Bl,  Branch  of  the  superficial  it  is  situated  behind  the  humeral  artery, 
nervous  arch ;  n2.  Branch  disappearing  on  and  the  filament  it  receives  from  the  mus- 
a  vessel ;  Bo,  b4,  Branches  uniting  with  culo-cutaneou3  joins  it  at  a  short  distance 
the  corresponding  ramuscules  of  the  ulnar ;  from  the  elbow-joint.  Placed  beside  the 
b5,  Branch  forming  the  internal  collateral  radial  artery,  the  median  is,  towards  the 
of  the  index ;  b6,  Paidimentary  branch  lower  third'  of  the  fore-arm,  immediately 
passing  to  the  thumb ;  C,  Collateral  given  below  the  posterior  border  of  the  great  pal- 
ofl'  by°the  median;  cl,  c2,  c3,  c4,  Colla-  mar  tendon;  it  afterwards  passes  through 
terals  furnished  by  the  median  and  ulnar,  the  carpal  sheath,  giving  a  branch  that 
— a,  Palmar  branch  of  the  ulnar ;  b,  Super-  constitutes  the  internal  palmar  collaterals 
ficial  branch  giving  off  a  filament  to  the  of  the  thumh.  and  external  of  the  index;  it 
hypothenar,  and  a  second  that  forms  the  tinally  forms  three  branches,  the  first  of 
superficial  nervous  arch;  61,  Deep  branch  which  anastomoses  with  the  idnar,  at  the 
passing  to  the  muscles  of  the  skin;  m,  Not  surface  of  the  palmar  arch,  and  is  lost  on 
anastomosing  with  the  median;  ml,  m2,  an  artery;  the  other  two,  receiving  a  fila- 
Anastomosing  with  the  corresponding  branch  ment  from  the  ulnar  at  the  origin  of  the 
of  the  median ;  the  innermost  passes  to  the  digits,  bifurcate  to  form  the  internal  palmar 
muscles  of  the  thumb  ;  c,  c,  c,  Collaterals  collateral  of  the  anmdaris,  and  collaterals  of 
furnished  by  the  ulnar  the  medius  and  index.     The  second  gives, 

in  addition,  a  slender  branch,  that  is  lost 
in  the  internal  and  middle  lobe  of  the  largo  cushion  of  the  paw.     In  fine,  the  median  of 


NERVES  OF   THE   PALMAR   FACE  ;    DOG. 

Trunk  of   the    median    dividing    into  six 


THE  BRACHIAL  PLEXUS. 


767 


the  Dog  furnishes  branches  to  all  the  digits,  except  the  auricularis  and  external  border 
of  tlie  annularis. 

In  the  Cat,  the  median  traverses  the  bony  canal  at  tlie  lower  extremity  of  the 
humerus,  and  separates  below  the  carpal  arch  into  three  branches.  The  internal 
branch  is  destined  to  the  rudimentary  thumb,  and  the  internal  palmar  border  of 
the  index.  The  middle  brancli  descends  in  the  third  interosseous  space,  furnishes  a 
filament  to  the  large  cushion  of  the  paw, 


and  divides  to  form  the  external  palmar 
collaterals  of  the  index  and  internal  of  the 
medius.  Finally,  the  external  branch  is 
placed  in  the  second  intermetacarpal  space, 
and  gives  the  following  pahuar  coUaierals : 
the  external  of  the  medius  and  internal  of 
the  annularis. 

The  ulnar  nerve  of  the  Bog.  below  the 
elbow,  lies  beside  the  ulnar  artery  to  the 
lower  third  of  that  vessel ;  there  it  forms 
two  branches — a  dorsal  and  palmar.  The 
dorsal  branch  becomes  subcutaneous,  passes 
along  the  external  border  of  the  fore-arm, 
metacarpus,  and  small  digit,  and  con- 
stitutes the  external  dorsal  collateral  nerve 
of  the  latter. 

The  palmar  branch  leaves  the  carpal 
sheath,  gives  off,  at  the  trapezoides,  a  ramus- 
cule  that  passes  to  the  surface  of  the  palmar 
muscles  to  form  the  external  collateral  pal- 
mar of  the  auricularis,  and  then,  at  the 
surface  of  the  deep  palmar  arch,  divides  into 
eight  terminal  ramuscules.  The  smallest 
of  the^e  is  expended  in  the  ru'limentary 
muscles  of  tlie  thumb,  the  small  digit,  and 
interosseous  muscles;  the  largest,  three  in 
number,  lie  on  the  interosseous  arteries,  and 
bifurcate  at  the  digits  to  form  the  palmar 
collaterals ;  the  two  internal  ramuscules  are 
previously  confounded  with  the  correspond- 
ing branches  of  the  median.  From  this 
arrangement,  it  results  that  the  ulnar  nerve 
supplies  the  palmar  surface  of  all  the  digits, 
except  the  internal  border  of  the  index. 

The  idnar  of  the  Cat  also  divides  into 
a  dorsal  and  a  palmar  branch,  but  the  <lis- 
tribution  of  these  is  not  the  same  as  in  the 
Dog. 

The  dorsal  brancli  bifurcates  at  the  car- 
pus :  one  of  the  filaments  forms  tln'  external 
dorsal  collateral  of  the  small  digit ;  the 
other  reaches  the  first  interosseous  s]  ace, 
receives  a  branch  from  the  radial,  and  after- 
wards gives  off  the  internal  dorsal  collateral 
of  the  small  digit,  and  external  of  the 
auricularis. 

The  palmar  branch  does  not  extend  to 


Ficr.  352. 


NERVES   OF    THE    PALMAR    FACE  ;    CAT. 

A,  Trunk  of  the  median  dividing  into  two 
branches ;  B,  Internal  branch,  giving  a 
rudimentary  filament  to  the  thumb ;  Bl, 
External  branch,  receiving  a  filament,  /, 
from  the  ulnar ;  c,  C,  C,  C,  Collaterals  fur- 
nished by  the  median. — a,  Palmar  branch 
of  the  ulnar  dividing  into  three  branches ; 
b,  Internal  branch,  detaching  the  filament, 
/,  to  the  median ;  61,  External  branch ;  62, 
Deep  branch ;  c,  c,  c,  Collaterals  furnished 
bv  the  ulnar. 


all  the  digits  as  in  the  Dog.  Passing  within 
the  pisiform  bone,  it  divides  into  several  filaments  :  some  of  these  are  distributed  to  the 
muscles  of  the  small  digit  and  thumb;  another  follows  the  external  border  of  the  small 
digit,  and  constitutes  its  external  palmar  collateral;  one  of  the  longest  is  lodged  in  ihe 
first  intermetacarpal  space,  giving  a  filament  to  the  large  cushion  of  the  paw,  ami 
the  internal  palmar  collaterals  of  the  small  digit  and  external  of  the  annularis. 


COMrARISON   OF  THE   BRACHIAL   PLEXUS   OF   MAN   WITH   THAT   OP   ANIMALS. 

The  brachial  plexus  of  Man,  like  that  of  the  Dog,  is  constituted  by  the  anterior 
branches  of  the  four  last  cervical,  and  the  last  dorsal  nerves.    The  few  variations  observed 


768 


TEE  NERVE. 


are  very  slight,  and  are  to  be  ascribed  to  the  difference  in  form  of  the  regions  to  which 
the  nerves  are  distributed. 

The  shoulder  of  Man  being  short,  and  the  other  rays  of  the  limb  long  and  -well 
detached,  the  branches  of  the  brachial  plexus  can  be  divided  into  collateral  and  terminal, 

The  collateral  branches  are*  1,  The  subclavian  branch,  \i\\\c\\  is  not  found  in  our 
animals,  they  having  no  subclavian  muscle ;  2,  The  nerve  of  the  angularis ;  3,  Nerve  of 
the  rhomboideus ;  4,  Superseapular  nerve  ;  5,  The  serratus  magnus  ( -poderior  thoracic) 
nerve  ;  6,  Subscapular,  which  is  divided  at  its  origin  into  two  branches  as  in  the  SJjeep 
and  Carnivora ;  7,  The  nerves  of  the  great  and  small  pectorals  (^anterior  thoracic) ;  8,  The 


Fi?.  353. 


THE   NERVES   OF   THE   AXILLA   OP   MAN. 

1,  Scalenus  medius ;  2,  Scalenus  anticus ;  3,  Cord  formed  by  5th  and  6th  cervical 
nerves  ;  4,  Seventh  cervical  nerve  ;  5,  Superseapular  nerve  ;  6,  Subclavian  artery, 
cut ,  7,  Insertion  of  subclavius ;  8,  Cord  formed  by  8th  cervical  and  1st  dorsal 
nerves  j  9,  Pectoralis  major,  reilected ;  10,  Internal  anterior  thoracic  nerve ;  12, 
Origin  of  subclavius;  13,  Pectoralis  minor,  reflected;  14,  Internal  cutaneous 
nerve;  15,  Axillary  artery,  cut;  16,  Postei-ior  thoracic  nei-ve,  17,  Musculo- 
cutaneous nerve ;  18,  Origin  of  pectoralis  minor ;  19,  Median  nerve ;  20,  Nerve 
of  Wrisberg;  21,  Coraco-bi-achialis ;  22,  Intercosto-humeral  nerve;  23,  Ulnar 
nerve ;  24,  Subscapularis ;  25,  Brachial  artery ;  26,  Lateral  cutaneous  branch  of 
3rd  intercostal  nerve ;  27,  Middle  subscapular  nerve ;  28,  Short  subscapular 
nerve;  29,  Pectoralis  major,  cut;  31,  Basilic  vein;  32,  Serratus  magnus;  33, 
Latissimus  dorsi. 


nrcessory  nerve  of  the  internal  cutaneous,  represented  in  quadrupeds  by  the  subcutaneous 
thoracic;  9,  The  nevve  oi  the  great  dorsal ;  10,  The  nerve  of  the  teres  major. 
The  terminal  branches  go  to  the  arm,  fore-arm,  and  hand.     They  are  : 
1.  The  internal  cutaneous,  which  in  the  Horse  is  furnished  by  the  ulnar  nerve.     It 
becomes  subcutaneous  at  the  upper  third  of  the  arm,  and  a  little  above  the  elbow  bifur- 
cates ;  the  anterior  is  spread  on  the  fiont  face  of  the  arm  to  the  wrist ;  the  posterior 


TEE  BRACHIAL  PLEXUS. 


769 


passes  backwards,  and  is  oxpondcd  in  the  skin  of 
the  back,  and  inner  part  of  the  fore-arm. 

2.  The  musculo-cutaneous  or  perforans  casserii, 
■whose  disposition  is  analogous  to  that  of  Carnivora. 

3.  The  axillary  nerve,  regarding  which  there  is 
nothing  to  say. 

4.  The  radial  nerve  (mnsculo-si)iral)  passes  as  in 
animals,  lies  in  the  twisted  furrow  of  the  humerus, 
gives  off  an  internal  and  external  cutaneous  branch, 
and  reaches  the  antero-external  part  of  the  arm,  in 
the  space  between  the  anterior  brachial  and  long 
supinator,  where  it  terminates  by  two  branches. 
The  anterior  of  these  reaches  the  back  of  the  hand, 
and  gives  off  three  ramuscules  there,  which  are  dis- 
tributed as  follows :  the  first  forms  the  external 
dorsal  collateral  of  the  thumb ;  the  second  bifur- 
cates, and  constitutes  the  internal  dorsal  coUateial 
of  the  thumb  and  external  collateral  of  the  index; 
lastly,  the  third  supplies  the  internal  collateral  uf 
the  index  and  external  of  the  medius.  This  branch 
always  aua&tomoses  with  the  dorsal  branch  of  the 
ulnar.  The  posterior  branch,  motor,  is  expended  in 
the  muscles  on  the  posterior  and  external  aspect  of 
the  fore-arm. 

5.  The  median  nerve  commences  by  two  branches : 
one  arises  in  common  with  the  musculo-cutaneous 
or  anterior  brachial,  and  corresjionds  to  the  anasto- 
mosis found  around  the  axillary  artery  of  the  Horse  ; 
the  other  is  detached  from  the  trunk  common  to  the 
ulnar  and  internal  cutaneous.  The  median  runs 
along  the  biceps,  passes  in  front  of  the  elbow,  and 
lies  beneath  the  annular  ligament  of  the  carpus, 
where  it  terminates  in  furnishing  :  1,  A  filament  to 
the  short  abductor  of  the  thmnb;  2,  Palmar  ramus- 
cules to  the  thumb,  index,  and  medius,  and  external 
border  of  the  annularis.  Tliis  disposition  of  the 
medius.  therefore,  much  resembles  that  of  the  Cat. 

6.  The  tdnar  nerve  passes  along  the  inner  border 
of  the  arm  and  fore-arm,  and  divides,  a  little  above 
tlie  inferior  extremity  of  the  olecranon,  into  two 
terminal  branches— a  dorsal  and  palmar.  The  first 
is  directed  on  the  back  of  the  hand,  and  separates 
into  three  metacarpal  branches,  which,  in  their  course, 
furnisli  the  dorsal  collaterals  of  the  auriciilaris  and 
annularis,  and  internal  collateral  of  the  medius  ;  the 
other  parts  of  the  hand  are  supplied  by  the  radial. 
The  second,  or  palmar  branch,  is  superficial,  and 
detaches  the  palmar  collaterals  of  the  little  finger 
and  internal  collateral  of  the  annularis,  as  well  as 
a  deep  ramuscule  that  lies  across  the  interosseous 
muscles,  and  is  a  motor  nerve.  To  resume,  we  see 
that  this  distribution  of  the  terminal  branches  of 
the  brachial  plexus  of  IMan  much  resembles  that 
described  in  Carnivora,  and  especially  in  the  Cat. 


Fig.  354. 


NERVKS  OF  THE  FRONT  OF  FORE- 
ARM AND  HAND  OF  MAN. 

.,  Supinator  longus,  cut ;  2,  Ulnar 
nerve ;  3,  Brachialis  anticus ;  4, 
Biceps  ;  5,  Musculo-spiral  nerve  , 
6,  Median  nerve ;  7,  Posterior 
interosseous    nerve ,    8,    Pronator 

-^ _  teres  and  flexor  carpi  radialis,  cut ; 

9,  Extensor  carpi  radialis  longior, 
cut;  10,  Brachial  artery;  11,  Supinator  brevis  ;  12,  Flexor  sublimis  digitorum,  cut; 
13,  13,  Radial  nerve;  14,  14,  Flexor  carpi  ulnaris -,  15,  Extensor  carpi  radialis  brevior  , 
16,  Ulnar  artery;  17,  Radial  origin  of  flexor  sublimis  digitorum,  cut;  18,  Flexor  pro- 
fundus digitorum;  19,  Tendon  of  pronator  teres;  20,  20,  Dorsal  branch  of  ulnar 
nerve  ;  21,  21,  Radial  artery  ;  22,  22,  Deep  branch  of  ulnar  nerve ;  23,  Flexor  longus 
poUicis;  24,  Abductor  minimi  digiti ;  25,  Anterior  interosseous  nerve;  26,  Digital 
branches  of  ulnar  nerve ;  27,  Tendon  of  supinator  longus ;  28,  One  of  the  lumbricalos 
muscles;  29,  Pronator  quadratus ;  31,  Tendon  of  flexor  carpi  radialis;  33,  Digital 
branches  of  median  nerve  ;  35,  Adductor  pollicis. 


770  TEE  NERVES. 

LUMBO-SACRAL    PLEXUS. 

The  last  two  lumbar  pairs,  and  the  three  first  sacral,  in  becoming  fused 
together,  form  the  lumbosacral  plexus,  which  corresponds  in  every  respect, 
by  its  constitution,  as  well  as  by  its  mode  of  distribution,  to  the  plexus  of 
the  thoracic  limb. 

It  is  usual,  in  human  anatomy,  to  describe  a  lumbar  and  a'sacral  plexus, 
each  formed  by  the  inferior  branches  of  all  the  spinal  pairs,  whose  names 
they  bear.  In  our  opinion,  this  proceeding  has  two  inconveniences :  at  first, 
it  separates  into  two  fiisciculi  the  nerves  of  the  abdominal  member,  and, 
besides,  in  including  in  the  description  of  these  nerves  the  first  lumbar  pair 
and  the  last  sacral,  elements  are  introduced  in  this  description  which  are 
altogether  foreign  to  it.  It  may  be  remarked,  that  the  four  first  lumbar 
pairs,  when  they  anastomose  with  each  other,  only  do  so  by  very  slender 
filaments ;  that  they  only  send  some  subcutaneous  filaments  to  the  posterior 
limb ;  that  the  two  last  sacral  branches,  principally  destined  to  the  genito- 
urinary organs  and  the  posterior  extremity  of  the  digestive  tube,  are 
ordinarily  without  any  direct  communication  with  the  others ;  that  the  two 
last  lumbar  pairs  and  the  three  first  sacral  are  alone  fused  in  the  same  manner 
us  the  brachial  plexus,  and  comport  themselves  lihe  that  plexus  in  the  distribution 
of  their  branches. 

It  is  with  some  reason,  then,  that  we  have  described,  in  a  special  manner, 
the  inferior  branches  of  the  four  lumbar  pairs  and  the  two  last  sacral, 
reserving  the  fasciculus  formed  by  the  five  intermediate  pairs  for  a  special 
description,  under  the  name  of  the  lumbosacral  plexus. 

Mode  of  constitution. — In  glancing  at  this  plexus,  we  may  perceive  that 
it  is  divided  into  two  portions — an  anterior  and  posterior,  each  having  a 
thick  trunk  in  the  centre. 

The  first  of  these  trunks  is  formed  by  the  two  above-named  lumbar  pairs, 
which  join  each  other  after  a  short  course,  and  after  receiving  an  accessory 
branch  from  the  fourth  pair.  The  second,  wider  and  thinner  than  the 
preceding,  comprises  the  fibres  of  the  three  sacral  pairs  which  escape  from 
beneath  the  subsacral  vessels,  and  unite  in  a  single  fasciculus.  These  two 
trunks  are  connected  with  each  other  by  one  or  two  branches  proceeding 
from  the  first  sacral  pair  to  the  obturator  nerve — one  of  the  distributive 
branches  of  the  first. 

Belations. — The  anterior  portion  of  the  lumbo-sacral  plexus  is  concealed 
beneath  the  small  psoas  muscle,  and  separated  by  the  internal  iliac  artery 
from  the  posterior  portion.  The  latter,  placed  above  and  on  the  side  of  the 
pelvis,  at  the  great  sciatic  opening,  corresponds,  inwardly,  to  the  subsacral 
vessels ;  outwardly,  and  in  front,  to  the  gluteal  vessels. 

Mode  of  distribution. — The  anterior  portion  of  the  plexus  at  first  gives  off 
several  small  branches  to  the  psoas  muscle,  and  particularly  to  the  iliacus  : 
these  branches  were  designated  by  Girard  the  iliaco-muscular  nerves;  it 
then  terminates  in  two  large  branches — tfee  crural  and  obturator  nerves.  The 
posterior  portion  is  continued  by  two  important  trunks,  the  great  and  small 
femoro-popliteal  nerves.  At  the  base  of  the  latter,  it  emits  the  anterior  and 
posterior  glntsal  nerves.  These  branches  and  their  ramifications  will  be 
successively  studied. 

Preparation  of  the  lumbosacral  plexus. — After  removinp;  tlio  skin  and  abrlomipal 
visce  a.  the  liind  quarters  are  isolated  by  sawing  tlirongh  the  vertebral  column  behind 
the  last  rib  ;  then,  by  means  of  a  section  almost  in  tne  middle  of  the  pelvis,  one  of  the 
limbs  is  cut  off,  and  tl.e  pieces,  disposed  as  in  figure  355,  should  be  maintained  in  thj 


TEE  LUMBOSACRAL  PLEXUS. 

Fig.  355. 


771 


LUMBO-SACRAL  PLEXUS   AND   INTERNAL   NERVES  OF   THE   POSTERIOR  LIMB. 

1,  1,  Lumbo-sacral  plexus  ;  2,  Anterior  femoral  nerve  ;  3,  Internal  saphena  nerve  ;  4, 
Obturatornerve  ;  5,  Originating  fasciculus  of  the  great  and  small  femoro-popliteal 
nerves ;   6,   Superficial    ramuscules    of  the    posterior  gluteal   nerves ;    7,   Great 
femoro-popliteal    nerve;    8,   Internal    pudic   nerve;    9,   Hemorrhoidal,    or   anal 
nerve;  10,  Internal  plantar  nerve;  11,  12,  Its  digital  ramifications. 
XoTE. — Tn  the  above  figure  is  seen  the  posterior  part  of  the  plexus  formed  by  the  nervous  branches  -which 
pass  through  the  three  first  subsacr:il  furaniina.     That  which  escapes  from  the  forimen  between  the  sacrum 
an'1  last  lumbar  vertebra,  only  gives  a  fine  branch  to  this  part  of  the  plexus,  and  sends  the  greater  portion  of 
its  fibres,  in  two  cords,  to  the  anterior  part.     This  arrangement  is  not  rare,  and  is  generally  seen,  we  believr, 
when  there  aie  only  five  lumbar  vertebra :  as  is  remarkfd  in  the  Ass  and  Mule,  and  sometimes  in  the  Horse. 
It  will,  therefore,  be  understood  that  the  nerve  described  by  us  as  the  finst  sacral  becomes  the  last  lumbar. 


772  THE  NERVES. 

first  position :  that  is,  with  the  croup  resting  on  the  dissecting  table  near  one  of  the  bars, 
and  the  limb  suspended  vertically,  the  foot  upwards,  by  a  cord  attached  to  the  ring  of 
the  bar. 

Afterwards,  the  preparation  is  executed  in  two  stages.  In  the  first,  after  tl;e  excision 
of  the  pelvic  organs  and  the  small  psoas  muscle,  the  whole  of  the  plexus  and  its  forma- 
tive branches  are  dissected,  taking  figure  355  as  a  guide.  In  the  second,  the  posterior 
part  of  the  plexus,  with  the  nerves  it  gives  off,  are  exposed  on  the  external  side,  by 
excising  the  greater  portion  of  the  principal  gluteal  muscle  and  the  anterior  portion  of 
the  long  vastus  (abductor  magnus,  or  triceps  abductor  femoris).  as  in  figure  356. 

To  follow  the  various  divisions  of  the  nerves  emanating  from  the  plexus,  to  their 
terminations,  it  is  well  to  use  the  other  limb,  which,  not  being  fixed,  can  be  laid  on  a 
table,  and  in  this  way  is  more  convenient  than  the  first  for  this  part  of  the  operation. 

1.  Hiaco-muscular  Nerves. 

These  nerves  are  of  little  importance.  The  principal  one  accompanies 
the  iliaco-muscular  artery  across  the  substance  of  the  iliacus  muscle. 

2.  Crural  or  Anterior  Femoral  Nerve.     (Fig.  355,  2.) 

This  is  the  largest  of  the  branches  arising  from  the  anterior  portion  of 
the  plexus.  It  descends  between  the  psoas  magnus  and  parvus,  to  the 
common  conical  extremity  of  the  latter  muscle  and  the  iliacus,  where  it  is 
covered  by  the  long  adductor  of  the  leg ;  there  it  terminates  in  a  wide  tuft  of 
branches,  destined  to  the  mass  of  the  triceps  extensor  cruris. 

Below  the  adductor,  it  successively  emits  two  long  branches,  which 
deserve  a  particular  description. 

The  first  represents  the  nervous  fasciculus  which,  in  Man,  comprises  the 
crural  miisculo-cutaneous  brandies.  We  have  named  it  the  accessory  branch  of 
the  internal  saphena.  It  reaches  the  interstice  between  the  two  adductors,  in 
crossing  the  crural  vessels  very  obliquely  forward.^  Leaving  this  space,  it 
becomes  subcutaneous  in  forming  numerous  divisions  which  surround  the 
saphena  artery  and  vein. 

The  second,  or  internal  saphena  nerve,  passes  at  fii'st  between  the  long 
adductor  of  the  leg  and  the  vastus  internus,  and  parallel  to  the  first,  which 
is  situated  more  inwardly  and  posteriorly.  Near  the  inferior  extremity  of 
the  interstice  separating  the  two  adductors  of  the  leg,  it  escapes  and  becomes 
subcutaneous,  dividing  into  a  number  of  filaments  which  meet  those  of  the 
accessory  nerve. 

These  two  branches  communicate  by  deep  or  superficial  anastomosing 
loops.  Before  leaving  the  space  between  the  adductors,  they  give  some 
slender  filaments  to  these  two  muscles,  particularly  to  the  anterior.  Near 
their  origin,  they  even  distribute  some  to  the  iliacus.  ^  Becoming  sub- 
cutaneous, their  ramuscles  cover  the  inner  face  of  the  thigh  and  leg ;  the 
longest  of  these  accompany  the  saphena  vein  to  the  anterior  aspect  of  the 

hock. 

It  sometimes,  indeed  most  frequently,  happens  that  the  internal  saphena 
nerve  and  its  accessory  form  only  a  single  branch,  whose  muscular  or 
cutaneous  divisions  otherwise  comport  themselves  exactly  like  the  above. 
This  is  exemplified  in  the  dissection  represented  in  figure  355. 

3.  Obturator  Nerve.     (Fig.  355,  4.) 

Situated  underneath  the  peritoneum,  to  the  inner  side  of  the  iliac  vessels 
which  it  accompanies  to  the  origin  of  the  obturator  artery,  this  nerve  follows 
the  latter  to  the  upper  face  of  the  pubis,  and  passes  with  it  beneath  the 
internal  obturator  muscle,  to  traverse  the  foramen  ovale.     In  this  way  it 


THE  LUMBOSACRAL  FLEX  IS. 


773 


arrives  outside  the  i)elvis,  where  it  nevertheless  remains  deeply  concealed  by 
the  muscular  masses  on  the  internal  aspect  of  the  thigh.  Its  terminal  rami- 
fications are  expended  in  the  obturator  externus,  the  adductors  of  the  thigh, 
the  pectineus,  and  the  short  adductor  of  the  leg.  T.e  branch  destined  to 
the  latter  muscle  is  the  longest ;  it  leaves  the  space  between  the  pectineus 
and  the  small  adductor  of  the  thigh,  and  descends  backwards  on  the  internal 
face  of  the  muscle  to  which  it  is  distributed. 

4.  Small  Sciatic  or  Anterior  and  Posterior  Gluteal  Nerves. 

The  small  sciatic  of  the  Horse  is  composed  of  several  cords  that  issue 
from  the  pelvis  by  the  upper  part  of  the  great  ischiatic  notch,  and  which  have 

Fig.  356. 


POSTERIOR   PORTION   OF   THE   LUMBO-SACRAL   PLEXUS. 

1,  Conjoining  fasciculi  of  the  three  first  sacral  nerves;  2,  3,  4,  5,  Anterior  gluteal 
nerves  ;  6,  6',  8,  Posterior  gluteal  nerves  ;  7,  9,  Branches  which  traverse  the 
great  sciatic  ligament,  and  communicate  between  the  posterior  gluteal  branches 
and  the  divisions  of  the  internal  pudic  nerve;  10,  11,  12,  13,  Great  sciatic  nerve 
and  its  crural  branches ;  14,  Small  femoro-popliteal  nerve ;  15  Its  cutaneous  or 
peroneal-cutaneous  branch. 

been   for  a   long  time   described   as   the   anterior   and   posterior   gluteal 
nerves. 

The  anterior  gluteal  or  ilio  muscular  nerves  (Fig.  356,  2,  3,  4,  5)  are  four 
or  five  in  number,  and  arise  either  separately  or  in  groups  from  the  posterior 
portion  of  the  lumbo-sacral  plexus.  They  appear  to  be  more  particularly 
furnished  by  the  two  first  sacral  branches.  All  leave  the  pelvic  cavity  by 
the  great  sciatic  opening,  along  with  the  anterior  gluteal  vessels.  The 
52 


774  TEE  NERVES. 

principal  branches  are  lost  in  the  middle  gluteal  muscle.  One  of  them 
(Fig.  356,  4,)  crosses  the  neck  of  the  ilium  above  the  small  (or  internal) 
gluteal  muscle,  and  passes  outwards  to  be  distributed  to  the  muscle  of  the 
tascia  lata  (tensor  vaginas  femoris).  The  last,  which  is  the  most  slender, 
descends  to  the  external  surface  of  the  gluteus  internus,  and  is  distributed  in 
its  substance  (Fig.  356,  5). 

The  posterior  gluteal,  or  iscliio-muscular  nerves  (Fig.  356,  6,  6',  8),  are 
usually  two  in  number — a  superior  and  inferior. 

The  first  escapes  through  the  gi'eat  sacro-ischiatic  notch,  along  with  the 
femoro-poplifceal  nerves,  and  is  situated  on  the  external  surface  of  the  ischiatic 
ligament.  It  passes  backward,  between  this  ligament  and  the  gluteus 
medius,  to  beneath  the  anterior  or  croupal  portion  of  the  triceps  extensor 
cruris,  in  which  it  is  distributed  by  several  filaments.  Besides  these,  it 
gives :  1,  In  passing  beneath  the  gluteus  medius,  a  slender,  but  constant 
filament  to  the  posterior  portion  of  that  muscle ;  2,  Another,  and  more 
considerable  branch,  which  bends  round  the  posterior  border  of  that 
muscle,  to  be  directed  forward  and  outward  to  the  gluteus  externus. 

The  second  nerve,  situated  beneath  the  preceding,  appears  to  be  detached 
from  the  posterior  border  of  the  great  sciatic.  It  is  placed  at  the  external 
surface  of  the  sciatic  ligament,  is  directed  backwards  in  passing  below  the 
croupal  portion  of  the  triceps  cruris,  traverses  that  muscle  above  the  ischial 
tuberosity,  descending  underneath  the  sacral  portion  of  the  semitendinosus, 
soon  to  leave  its  deep  track  and  become  superficial.  It  escapes  from  between 
the  latter  muscle  and  the  triceps  cruris,  and  is  lost  beneath  the  skin  covering 
the  posterior  part  of  the  thigh.  Its  deep  portion  gives  off  collateral 
branches  which  reinforce  the  divisions  of  the  internal  pudic  nerve,  as  well 
as  filaments  to  the  long  branch  of  the  semitendinosus  muscle. 

5.  Great  Sciatic  or  Great  Femoro-joopliteal  Nerve.     (Figs.  135, 13  ;  357, 1,  2.) 

This  enormous  nervous  trunk  issues  by  the  great  sciatic  opening  in  the 
form  of  a  wide  band,  which  is  applied  to  the  external  face  of  the  ischiatic 
ligament.  Comprised  at  first  between  that  ligament  and  the  gluteus  medius, 
it  is  directed  backwards  in  passing  over  the  fixed  insertion  of  the  gluteus 
internus,  and  arrives  behind  the  gemini  and  quadratus  femoris  muscles.  On 
leaving  this  point,  it  is  inflected  to  descend  behind  the  thigh,  where  it  is 
lodged  in  the  muscular  sheath  formed  for  it  by  the  triceps  cruris,  the  semi- 
tendinosus and  membrauosus,  and  the  great  adductor  of  the  thigh.  Arriving 
towards  the  superior  extremity  of  the  leg,  it  enters  between  the  two  bellies 
of  the  gastrocnemii  muscles,  passes  along  the  posterior  aspect  of  the 
perforatus  muscle,  and  descends  in  the  channel  of  the  hock,  beneath  the  tibial 
aponeurosis,  following  the  internal  border  of  the  fibrous  band  that  rein- 
forces the  tendon  of  the  hock.  It  finally  terminates  at  the  calcis  by  two 
branches ;  the  external  and  internal  plantar  nerves. 

From  the  point  at  which  the  great  sciatic  enters  between  the  bellies  of 
the  gastrocnemii  muscles,  and  as  far  as  the  furrow  of  the  calcis,  this  nerve 
corresponds  to  the  branch  named  in  Man  the  internal  popliteal — a  branch 
that  is  continued  by  the  posterior  tibial,  which  terminates  in  the  plantar 
filaments. 

In  its  long  course,  this  nerve  successively  emits :  1,  The  external 
popliteal  nerve  ;  2,  A  branch  to  the  muscles  of  the  deep  pelvi-crural  region  ; 
3,  Another  to  the  posterior  crural  muscles;  4,  The  external  saphenous 
nerve;  5,  A  voluminous  fasciculus  to  the  muscles  of  the  posterior   tibial 


TEE  LUMBOSACRAL  PLEXUS.  775 

region.  All  these  branclies  will  be  studied,  more  especially  the  external 
popliteal ;  which  is  so  disposed  in  Solipeds,  that  Veterinary  authorities  have 
described  it  as  a  special  trunk,  by  the  name  of  the  small  femoro-popliteal, 
and  even  as  the  small  sciatic  nerve.  We  will  afterwards  pass  to  the  ter- 
minal branches. 

collateral  bkanches. 

1.  External  Sciatic-popliteal,  or  Small  Femoro-popliteal  Nerve. — 
This  nerve  separates  from  the  great  sciatic  at  the  gemini  muscles  of  the 
pelvis.  It  is  then  directed  forward  and  downward,  proceeds  between  the 
triceps  cruris  and  the  gastrocnemius  muscles,  and  arrives  outside  the  superior 
extremity  of  the  leg,  behind  the  lateral  ligament  of  the  femoro-tibial 
articulation,  where  it  terminates  by  two  branches :  the  musculo-cutaneous,  and 
the  anterior  tibial  nerve. 

In  the  long  course  it  follows  from  its  origin  to  its  bifurcation,  the  external 
sciatic  popliteal  nerve  only  furnishes  a  single  collateral  branch :  this  is  the 
cutaneous  nerve  which  is  detached  fi'om  the  parent  trunk  above  the  gastro- 
cnemius, and  which  traverses  the  inferior  extremity  of  the  triceps  cruris,  to 
terminate  by  divergent  ramuscles  destined  to  the  skin  of  the  leg.  It  might 
be  named  the  peroneal-cutaneoiis  branch.  Before  becoming  superficial,  this 
cutaneous  nerve  gives  off  a  small  descending  filament  which  goes  to  reinforce 
the  external  saphenous  nerve,  after  creeping  over  the  aponeurotic  layer  of 
the  external  gastrocnemius.  This  branch,  which  might  be  designated  the 
accessory  of  the  external  saphenous,  sometimes  proceeds  directly  from  the 
popliteal,  as  may  be  remarked  in  Fig.  857. 

Terminal  Branches. — These  two  branches  influence  the  contractility  of 
the  muscles  belonging  to  the  anterior  tibial  region,  and  endow  the  skin  on 
the  anterior  face  of  the  foot  with  sensation. 

The  musculo-cutaneous  nerve  is  situated  beneath  the  tibial  aponeurosis ;  it 
fii'st  sends  a  bundle  of  ramuscules  to  the  lateral  extensor  of  the  phalanges, 
and  continues  to  descend  between  that  muscle  and  its  congener,  the  anterior 
extensor,  to  the  middle  of  the  tibia.  It  then  traverses  the  fibrous  envelope 
of  the  tibial  muscle,  becomes  subcutaneous,  and  gains  the  anterior  face  of 
the  metatarsus,  where  it  is  lost  in  the  skin.  Some  of  its  terminal  filaments 
may  be  followed  to  the  fetlock,  and  even  beyond  it  (Fig.  357,  6). 

The  anterior  tibial  nerve  passes  in  front  of  the  preceding,  to  one  side  of 
the  superior  extremity  of  the  leg,  and  then  plunges  beneath  the  anterior  ex- 
tensor of  the  phalanges,  giving  to  that  muscle  and  the  flexor  of  the  metatarsus 
short,  but  thick,  ramuscules.  It  descends  to  the  front  of  the  tarsus,  always 
covered  by  the  anterior  extensor  of  the  phalanges,  and  placed  at  the  external 
side  of  the  anterior  tibial  vessels.  When  it  arrives  below  the  tibia,  it  lies 
immediately  alongside  the  pedal  artery,  and  follows  it,  in  its  metatarsal 
portion,  to  near  the  fetlock.  It  then  separates  from  its  satellite  vessel,  and 
passes  on  the  side  of  the  digit,  where  it  ends  by  the  emission  of  cutaneous 
filaments  (Fig.  357,  5). 

Among  the  ramuscules  this  nerve  abandons  in  its  course,  are  cited  those 
which  carry  nei-vous  influence  to  the  pedal  muscle. 

2.  Branches  to  the  Muscles  op  the  Deep  Pelvi-crural  Eegion. — 
It  is  known  that  this  region  comprises  the  obturator  internus,  gemini,  and 
quadratus  femoris  muscles.  The  nervous  branch  sent  to  them  is  long  and 
attenuated  ;  it  is  detached  from  the  sciatic  trunk  at  the  middle  of  the  super- 
cotyloid  ridge,  and  descends  with  that  trunk  behind  the  coxo-femoral 
articidation,  to  distribute  its  terminal  divisions  to  the  above-named  muscles. 


776 


THE  NEBVES. 


357. 


The  longest  and  thickest  of  these  goes  to  the  quaclratus  femoris.  That 
passing  to  the  obturator  internus  re-enters  the  pelvic-cavity  by  the  small 
ischiatic  notch,  and  ascends  to  the  vicinity  of  the  ilio-sacral  articulation. 

3.  Branch  to  the  Ischio-tibial 
OR  Posterior  Crural  Muscles. — 
This  branch  is  thick  and  short ;  it 
arises  from  the  bend  formed  by  the 
great  femoro-poiditeal  nerve  at  the 
gemini  muscles,  and  soon  divides  into 
several  ramifications  which  are  dis- 
tributed to  the  short  portion  of  the 
triceps  cruris,  the  middle  and  inferior 
parts  of  the  semitendinosus,  and  into 
the  semimembi'anosus.  Some  of  the 
filaments  destined  to  the  latter  muscle 
pass  between  it  and  the  great  adductor 
of  the  thigh,  in  which  they  partly 
terminate  (Fig.  356,  12). 

4.  External  Saphenous  Nerve. 
—  This  branch  commences  at  from  2 
to  6  inches  from  the  point  where  the 
great  sciatic  nerve  dips  between  the 
gastrocuemii  muscles.  It  is  placed 
on  the  external  gastrocnemius,  and 
descends  underneath  the  special  apo- 
neurotic layer  covering  that  muscle, 
to  the  origin  of  the  tendon  of  the 
hock.  It  then  receives  its  accessoyi/ 
nerve — the  reinforcing  filament  which 
comes  from  the  cutaneous  branch  of 
the  small  femoro-popliteal  nerve,  and 
is  prolonged  beneath  the  tibial  apo- 
neurosis into  the  channel  of  the  hock, 
accompanying  the  external  saphenous 
vein,  and  following  the  external 
border  of  the  fibrous  band  that  goes 
to  strengthen  the  tendo-Achillis.  In 
this  way,  it  occupies  the  same  situa- 
tion outside  the  hock  that  the  great 
sciatic  does  on  the  inner  side.  It 
afterwards    passes    over     the    tarsal 

1,  2,  Great  sciatic  nerve ;  3,  External  saphena  region,  and  is  expended  on  the  outside 
nerve;  4,  External  popliteal  nerve ;  5,  An-  ^^  ^^^  metatarsus  in  several  filaments, 
terior  tibial  nerve :   b,  Muscuio-cutaneous  i  •   i      t  i    i.      ai  „   „„4.  „ 

nei^e;  7,Originof  theperoneal-cutaneous  SOme  of  which  descend  to  tl.e_  outer 
branch  ;  8,  Accessory  branch  of  the  external  aspect  of  the  digit  (FigS.  3o6,  13; 
saphenous  nerve  ;  9,  External  plantar  nerve    357^  3). 

with  its  divisions,  which  cover  the  digital  ~     ;p^gcjcuLI     TO    THE    POSTERIOR 

artery  and  vein.  TiBIAL   MuSCLES.— This  fasciculus   is 

composed  of  numerous  branches,  which  are  detached  together  from  the 
sciatic  nerve  on  its  passage  between  the  gastrocuemii  muscles,  in  the  form 
of  a  thick  short  trunk.  The  muscles  of  the  superficial  layer— the  gastro- 
enemii,  perforatus.  and  the  thin  fleshy  band,  improperly  designated  the  small 
plantaris  by  Veterinarians — receive  ramuscules  which  are  remarkable  lor  their 


EXTERNAL   NERVES   OP   THE   POSTERIOR 
LIMB. 


THE  LVMBO-SACEAL  F LEXUS.  777 

large  number  and  tbeir  shortness.  Those  of  the  deep  layer  are  supplied  by 
filaments  from  a  single  long  and  thick  branch,  which  descends  between  the 
perforatus  and  the  internal  gastrocnemius.  It  may  be  remarked,  that  the 
filament  going  to  the  so-called  small  plantar  muscle,  passes  underneath  the 
external  gastrocnemius,  outside  the  perforatus,  and  that,  by  its  position,  it 
exactly  represents  the  soleus  ramuscule  of  Man.  We  are.  therefore,  with 
Vicq-d'Azyr,  Cuvier,  and  others,  justified  in  naming  this  little  muscle  the 
solearis' (soleus),  instead  of  continuing  to  designate  it  the  small  plantaris, 
which  appellation  is  given  to  another  muscular  element. 

6.  In  its  course  along  the  tendo-Achillis,  the  sciatic  nerve  emits  some 
slender  cutaneous  filaments,  which  we  do  not  consider  worthy  of  further 
notice. 

TERMINAL    BRANCHES. 

Plantar  Nerves  (Fig.  355,  10,  12). — These  two  nerves  enter  the 
tarsal  sheath,  behind  the  perforaus  tendon,  along  with  the  plantar  arteries. 
Towards  the  superior  extremity  of  the  cannon,  they  definitively  separate 
from  each  other ;  the  external  is  carried  outwards  between  the  precited 
tendon  and  the  rudimentary  metatarsal  bone  ;  the  internal  is  placed  with 
that  tendon,  and  follows  the  posterior  border  of  the  inner  metatarsal  bone. 
Both  afterwards  descend  on  the  fetlock,  where  they  comport  themselves 
like  the  analogous  nerves  of  the  anterior  limb. 

DIFFERENTIAL   CHARACTERS   IN   THE   LIIMBO-SACRAL   PLEXVS   OF   OTHER  THAN   SOLIPED 

ANIMALS. 

As  was  the  case  ■with  the  brachial  plexus,  so  with  this ;  the  differences  observed 
being  trifling  in  the  upper  part  of  the  limb,  but  more  nuuK  rous  and  important  in  the 
region  of  the  foot,  the  complt- xity  of  arrangement  varying  with  the  species. 

Ruminants. — The  lumbo-sacral  plexus  of  these  animals  is  constituted  by  two  lumbar 
and  three  sacral  nerves,  iis  in  Solipeds;  but  the  third  sacral  only  gives  a  very  fine 
filament,  which  reaches  the  second  in  passing  downward  and  forward. 

At  the  femoro-tibial  articulation,  the  branches  of  the  plexus  are  similar  to  those  iu 
the  Horse.  Below  that  articulation,  the  following  disposition  Las  been  observed  in 
the  Sheep. 

The  muKCtdo-cutaneous  branch  of  the  popliteal  is  long  and  thiclr.  It  descends  on  the 
anterior  face  of  the  metatarsus,  and  at  the  metatarso-phalangeal  aiticulation  bifurcates, 
the  branches  forming  the  di)rsal  collaterals  of  the  digits.  The  anterior  tibial  nerve 
pr<  sents  two  branches  parallel  to  the  tibial  vessels ;  one  passes  along  the  metatarsal 
region,  and  when  it  arrives  at  the  bottom  of  the  groove  between  tl  e  condyles  of  the 
metatarsus,  it  divides  into  two  branches  that  constitute  the  d(  ep  collaterals  of  the 
di.;its;  these  collaterals  furnish  filaments  to  the  posterior  face  of  the  digital  region. 

The  great  sciatic  resembles  that  of  Solipeds.  Its  terminal  branches,  or  plantar 
nerves,  differ  from  those  of  the  Horse  in  the  absence  of  the  tian»verse  anastomosis  that 
unites  the  two  cords  in  the  region  of  the  tendons. 

Pig. — The  lumbo-sacral  plexus  of  this  animal  is  composed  of  two  lumbar  and  three 
sacral  nerves  reckoning,  of  course,  as  a  sacral  nerve,  the  trunk  that  escapes  fmm 
between  the  last  lumbar  vertebra  and  the  sacrum.  The  plexus  may  be  divided  into 
two  portions,  the  first  furnishing  a  femoral  and  an  obturator  nerve.  The  internal 
siiphenous  branch  of  the  femoral  nerve  is  long  and  voluminous;  at  its  origin  it  is  as 
Inige  as  the  branch  passing  to  the  anterior  muscles  of  the  thigh,  and  it  descends  on  the 
inner  face  of  the  metatarsus,  forming  the  dorsal  collateral  of  the  internal  digit. 

The  great  sciatic  is  voluminous  and  round.  Tlie  branches  it  gives  to  the  muscles 
of  the  pelvis  and  femur  are  disposed  nearly  as  in  Solipeds  and  Euminants;  but 
differences  are  observed  in  the  external  popjliteal  and  the  terminal  branches. 

The  mnsculo  cufaneoics  nerve  reaches  the  metatarsal  region,  where  it  separates  into 
three  branches,  which  form  the  dors  tl  collaterals  of  the  dibits. 

The  anterior  tibial  nerve  descends  between  the  two  prim-ipal  metatarsals,  a.nd  at  the 
root  of  the  middle  digits  divides  to  anastomose  with  the  plantar  nerves.  Of  th  se  ti.e 
external   is  small,  and  gives  collaterals   to  the  two  external  digits;  the   internal,  the 


778  THE  NERVES. 

largest,  descends  between  the  two  principal  digits,  where  it  bifurcates ;  above,  it  gives  a 
branch  to  the  internal  digit. 

Carnivora. — In  these  animals,  the  lumbo-sacral  plexus  is  formed  by  the  last  four 
lumbar  and  the  first  two  sacral. 

The  crural  and  obturator  nerves,  which  arise  from  the  fourth,  fifth,  and  sixth  lumbar 
nerves,  offer  nothing  particular  in  their  disposition. 

The  internal  saphenous  branch  is  as  long  as  in  the  Pig ;  it  passes  to  tlie  internal  face 
of  the  tarsus,  lies  alongside  the  fourth  metatarsal  bone,  and  forms  the  internal  dorsal 
collateral  of  the  fourth  toe. 

The  great  sciatic  may  be  described  as  having,  as  in  Man,  two  terminal  branches 
which  separate  a  little  above  the  posterior  face  of  the  femoro-tibial  articulation.  The 
external  popliteal  nerve  passes  to  the  surface  of  the  external  gastrocnemius,  enters 
between  the  common  long  flexor  of  the  toes  and  the  long  lateral  peroneal  muscle, 
where  it  bifurcates.  The  musculo-cutaneous  branch  descends  beneath  the  latter  muscle 
to  the  lower  third  of  the  leg,  when  it  becomes  superficial,  and,  accompanied  by  a  vein, 
is  lodged  in  the  interspace  between  that  muscle  and  the  anterior  tibial ;  it  passes  in 
front  of  the  tarsus,  and  reaches  the  upper  part  of  the  metatarsus,  where  it  divides  into 
three  divisions.  It  must  be  mentioned  that  at  the  tibiotarsal  articulation  is  thrown  off 
a  very  fine  cord,  which  is  directed  outwards,  and  forms  the  external  dorsal  collateral 
of  the  first  toe.  Each  of  its  tliree  terminal  branches  ccui'ses  along  an  intermetatarsal 
space,  and  at  the  metatarso-phalangeal  articulations  separates  into  two  filaments, 
whence  results  the  following  distribution :  the  external  branch  forms  the  internal 
dorsal  collaterals  of  the  first  toe  and  external  of  the  second ;  the  middle  constitutes 
the  internal  dorsal  collaterals  of  the  second  toe  and  external  of  the  third ;  lastly,  the 
internal  furnishes  the  internal  dorsal  collaterals  of  the  third  toe  and  external  of  the 
fourth.  The  anterior  tibial  nerve  accompanies  the  artery  of  that  name,  descends  along 
the  external  face  of  the  tibia,  and  terminates  in  two  branches  at  the  tarsus.  Of  these, 
one  is  distributed  to  the  tarsal  articulations  and  the  pedal  muscle  ;  the  other,  internal, 
enters  the  intermetatarsal  space,  and  at  the  corresponding  metatarso-phalangeal  joints 
anastomoses  with  the  internal  branch  of  the  musculo-cutaneous  nerve,  and  is  lost  in  tlie 
same  parts.  The  internal  popliteus  forms  the  second  terminal  branch  of  the  great  sciatic 
nerve,  and  in  the  Dog  and  Cat  represents  that  portion  of  the  latter  whicli,  in  the  Horse, 
is  situated  behind  the  femoi-o-tibial  articulation.  It  is  continued  by  the  posterior  tibial 
nerve,  which  terminates  by  the  two  plantar  nerves.  During  its  course,  the  external 
popliteal  furnishes  articular  and  muscular  filaments,  as  well  as  cutaneous  twigs 
subsequently;  among  the  latter  may  be  mentioned  the  external  saphenous,  which  arises 
by  two  branches,  and  is  expended  behind  the  malleolus,  at  the  outer  side  of  the  tarsus. 
The  plantar  nerves  are  external  and  internal ;  the  latter  lies  at  the  inner  border  of  the 
tendon  of  the  superficial  flexor  muscles  of  the  phalanges,  and  when  it  joins  the  middle 
of  the  metatarsus,  it  detaches  a  fine  filament  that  forms  the  internal  plantar  collateral 
of  the  fourth  toe;  it  then  passes  obliquely  towards  the  first  toe,  at  the  deep  face  of  the 
above-named  tendon,  and  successively  gives  off  three  filaments — one  for  each  inter- 
metatarsal space.  These  filaments  anastomose  with  the  terminal  branches  of  the 
external  plantar,  at  the  metatarso-phalangeal  articulations;  the  first  two  filaments 
supply  the  large  cushion  of  the  paw. 

The  external  plantar  nerve  passes  between  the  two  flexor  tendons  of  the  toes,  where 
it  gives  a  filament  that  constitutes  the  external  plantar  collateral  of  the  first  toe.  It  is 
afterwards  placed  outside  the  deep  flexor,  then  enters  beneath  the  short  flexor  and 
divides  into  several  branches,  muscular  and  digital.  Each  of  the  latter,  three  in 
number,  passes  into  a  corresponding  interosseous  space  and  bifurcates  at  the  metatarso- 
phalangeal articulations,  receiving  filaments  from  the  internal  plantar,  and  forming  the 
following  plantar  collatirals  :  the  internal  of  the  first  toe,  internal  and  external  of  the 
second,  internal  and  external  of  the  third,  and  external  of  the  fourth  digit. 

COMPARISON   OF   THK   LUMBO-SACRAL    PLEXUS   OF   MAN   WITH   THAT  OP   ANIMALS. 

It  is  usual,  in  human  anatomy,  to  describe  a  lumbar  and  a  sacral  plexus. 

The  lumbar  plexus  is  constituted  by  the  anastomoses  of  the  anterior  branches  of  the 
five  lumbar  nerves;'  these  are  united  by  fine  filaments,  which  are  not  intricately 
associated.  The  divisions  of  this  plexus  are  distinguished  as  collateral  and  terminal 
branches.    The  first,  destined  to  the  upper  part  of  the  limb  and  the  skin  covering  the 


('  Wilson  says  the  four  upper  lumbar  nerves  and  the  last  dorsal ;  Heath  gives  the 

same  constitution.) 


THE  LUMBO-SACIiAL  PLEXUS. 


779 


external  genital  organs,  are  represented  in  Solipeds  by  the  ramifications  of  the  lumbar 
nerves,  which  have  been  separately  described.  The  terminal  branches  are  the 
obturator  crural,  and  anterior  femoral  (or  anterior  crural).  There  is  nothing  to  be  said 
respecting  the  obturator  nerve  ; 

it  le.ives  the  pelvis  by  the  obtui  a-  Fi^.  35.9. 

tor  foramen,  as  in  all  the  animals 
mentioned.  The  crural  has 
been  described  as  having  four 
terminal  branches :  the  internal 
and  external  musculo-cutaneous, 
the  nerve  of  the  triceps  crureus 
(muscular  hranch),  and  the  in- 
ternal saphenoiis.  The  two  mus- 
culo-cutaneous branches  have 
their  analogue  in  the  Horse,  in 
the  filament  we  have  named  the 
accessory  branch  of  the  internal 
saphenous.  The  nerve  of  the 
triceps  is  expended  in  the  an- 
terior rectus,  and  the  vastus 
iuternus  and  externus.  The 
saphenous  descends  between  the 
muscles  of  the  inner  aspect  of 
the  thigh,  beneath  the  aponeu- 
rosis, and  becomes  superficial  at 
a  short  distance  from  the  cou- 
dyle  of  the  femur,  giving  a 
patellar  branch  that  divides  in 
tlie  skin  of  tire  knee,  and  a 
tibial  branch  that  is  expended 
on  the  inner  face  of  the  tarsal 
artienlatiotis  and  the  foot. 

The  sacral  plexus  comprises 
the  first  three  sacral  nerves,  t  > 
which  is  added  a  lumbo-sacral 
branch  furnished  by  the  lumbar 
nerves,  and  a  fine  filament  that 
ascends  from  the  fourth  sacral. 

Ten  collaterals  ami  a  ter- 
minal branch  arise  from  this 
plexus. 

The  collateral  branches  are 
divided  into  intrapelvic  and 
extrapelvic:  they  are  five  in 
each  group.  The  first  are  des- 
tined to  the  muscles  of  the  inner 
aspect  of  the  pelvis,  and  to  tliose 
of  the  perineum  and  t  e  skin 
of  this  region.  The  second  are 
distributed  to  the  muscles  on 
the  outer  aspect  of  the  pelvis, 
and  the  skin  on  the  posterior  face  of  the  thi',^h.     They  are  : 

1.  Visceral  branches  that  descend  on  the  sides  of  the  rectum  and  are  lost  in  the 
hypogastric  plexus ;  2,  Nerve  of  the  elevator  of  the  anus  ;  3,  Hemorrhoidal  or  anal  nerve  ; 
4,  Nerve  of  the  internal  obturator  that  appears  to  arise,  in  the  Horse,  from  the  sciatic 
trunk ;  5,  Internal  pudic,  which  has  been  described  with  the  sacral  nerves.  In  Man  this 
nerve  leaves  the  pelvis  by  the  great  sciatic  notch  (or  foramen],  and  returns  to  it  by  the 
lesser ;  within  the  ischiatic  tuberosity  it  divides  into  two  blanches :  an  inferior  or 
perineal,  and  a  superior  or  dorsalis  penis  nerve.  The  latter  is  placed  on  the  dorsum 
of  the  penis,  and  reaches  the  mucous  membrane  of  the  glans  and  prepuce ;  the  former 
does  not  go  beyond  the  muscles  and  integuments  of  the  perineum.  6,  The  superior 
gluteal  nerve  ;  7,  Nerve  of  the  pyramidalis ,  8,  Nerve  of  the  superior  gemellus ;  9,  Nerve  of 
the  inferior  gemellus  and  quadratus  cruralis  ,  10,  The  small  sciatic,  or  inferior  gluteal  nerve, 
the  inferior  or  femoral  branch  of  which  is  very  long,  descending,  as  it  does,  to  the  middle 
of  the  posterior  face  of  the  thigli,  beneath  the  crural  aponeurosis,  to  the  popliteal  space, 
where  it  becomes  superficial,  and  terminates  in  the  skin  of  the  upper  portion  of  the  leg. 


LUMBAR   PLEXUS  OF   MAN. 

1,  Right  gangliated  cord  of  sympathetic;  2,  Abdominal 
aorta ;  3,  3,  Last  dorsal  nerves ;  4,  Psoas  parvus  ;  5, 
Quadratus  lumborum ;  6,  Psoas  magnus ;  7,  7,  Ilio- 
hypogastric nerves ;  8,  lliacus  internus ;  9,  9,  Ilio- 
inguinal nerve;  10,  Lumbo-sacral  nerve;  11,  Genito- 
crural  nerve;  12,  Gluteal  nerve;  13,  Iliac  branch  of 
ilio-hypogastric  nerve  ;  14,  Sacral  plexus  ;  15,  15,  15, 
External  cutaneous  nerves ;  17,  Transversalis  abdomi- 
nis; 19,  Obliquus  internus;  21,  Obliquus  externus; 
23,  23,  Anterior  crural  nerves ;  25,  25,  Obturator 
nerves  ;  27,  27,  Crural  branch  of  genito-crural  nerve  ; 
29,  Genital  branch  of  genito-crural  nerve;  31,  External 
iliac  artery  ;  33,  External  abdominal  ring. 


780. 


THE  NERVES. 


Fie;.  3''.9. 


Fi2.  360. 


NERVES   AT  THE   POSTERIOR   ASPECT   OF 
HUMAN    LEG. 

1,  Popliteal  artery;  2,  Great  sciatic  nerve; 
3,  Adductor  magnus  ;  4,  Biceps;  5,  Superior 
internal  articular  artery  ;  6,  External  pop- 
liteal nerve ;  7,  Gastrocnemius,  cut  ;  8, 
Anterior  tibial  artery  ;  9,  Tendon  of  semi- 
membranosus ;  10,  Peroneus  longus;  11, 
Sural  arteries  and  nerves ;  12,  Peroneal 
artery ;  13,  Internal  popliteal  nerve  ;  14, 
Tibialis  posticus ;  15,  Portion  of  soleus  ; 
16,  Peroneus  brevis ;  17,  Popliteus ;  18, 
Flexor  longus  poUicis  ;  19,  Posterior  tibial 
nerve ;  20,  Calcanean  branch  of  posterior 
tibial  nerve;  21,  Posterior  tibial  artery; 
22,  Tendo-Achillis  ;  23,  Flexor  longus  digit- 
orum;  25,  Tendon  of  tibialis  posticus;  27, 
Plantar  nerves  ;  29,  Plantar  arteries. 


NERVES  AT  THE  FRONT  ASPECT  OF  HUMAN  LEG. 

1,  External  popliteal  nerve ;  2,  Anterior 
tibial  arterv  ;  3,  Musculo-cutaneous  nerve  ; 
4,  Anterior  tibial  nerve  ;  5,  Peroneus 
longus ;  6,  Tibialis  anticus ;  7,  Extensor 
longus  digitorum  ;  8,  Anterior  annular 
ligament ;  9,  Peroneus  brevis  ;  10,  Tendon 
of  extensor  proprius  pollicis;  11,  Extensor 
proprius  pollicis  ;  1 2.  Dorsal  artery  of  foot ; 
13,  Point  at  which  the  musculo-cutaneous 
nerve  pierces  the  fascia  and  bifurcates  ;  14, 
Tendon  of  tibialis  anticus;  15,  Internal 
branch  of  musculo-cutaneous  nerve;  16, 
Cutaneous  branch  of  anterior  tibial  nerve; 
17,  External  branch  of  musculo-cutaneous 
nerve ;  19,  Deep  branch  of  anterior  tibial 
nerve;  21,  External  saphenous  nerve;  23, 
Extensor  brevis  disritorum. 


THE  GREAT  SYMPATHETIC  NERVOUS  SYSTEM.  7S1 

The  terminal  hranch  of  the  sacral  plexus  forms  the  great  sciatic  nerve,  whose 
distribution  is  ihe  same  as  that  of  Carnivora.  The  collateral  ramuscules  of  the  o-reat 
sciatic  are  the  bnuich  of  the  long  portion  of  the  biceps;  the  semi tendinosus'^ and 
semimembrano.sus  brancli ;  the  branch  to  the  great  adductor;  and,  lastly,  that  to  the 
short  portion  of  the  biceps.     It  terminates  by  the  external  and  internal  popliteal. 

The  musculo-cufaneous  and  anterior  tibial,  continuiitions  of  thf^  external  poplitens 
comport  themselves  almost  the  same  as  in  the  Dog.  Thiy  form  dorsal  collaterals  to  the 
third,  fourth,  and  fifth  toes,  as  well  as  to  the  second. 

The  internal  popliteal  presents  an  external  saphenous  n-rve  that  passes  along  the 
external  border  of  the  foot,  and  has,  in  addition,  a  branch  that  ascends  on  the  dorsum 
of  that  org  in.  The  external  saphenous  furnishes  the  dorsal  coUatHrals  to  the  first  toe, 
and  the  external  collateral  to  the  second.  The  posterior  tibial  nerve  continues  the 
internal  sciatic  in  the  leg;  it  terminates  in  the  plantar  nerves.  The  internal  plantar 
furnishes  the  collateral  nerves  to  the  fifth,  fourth,  and  third  toes,  and  the  internal 
collateral  of  the  second  toe.  The  external  divides  into  three  branches :  the  two 
superficial  branches  form  the  collaterals  of  the  first  toe,  and  the  external  collateral  of  the 
second;  the  deep  branch  passes  inwards,  behind  the  interosseous  muscles,  and  is 
expended  in  those  of  the  fourth  space,  after  giving  filaments  to  the  oblique  abductor  of 
the  large  toe,  transverse  abductor,  last  two  lumbricales,  to  the  interosseous,  aud  very 
fine  filaments  to  the  articulations  of  the  tarsus  with  the  metatarsus. 

It  will  tlierefore  be  seen  that,  in  Man,  the  branches  of  the  deep  trunk  of  the 
external  plantar  join  those  of  the  internal  plantar,  to  form  the  collateral  nerves. 


CHAPTER  III. 

THE    GREAT    SYMPATHETIC   NERVOUS   SYSTEM. 

Pbepabation  op  the  Great  Sympathetic. — The  same  subject  ought  to  suffice  for  the 
preparation  of  this,  as  well  as  the  pneumngastric  and  spinal  nerves.  After  placing  the 
animal  in  the  first  position,  the  inte.stiu'  s  are  removed,  one  of  the  posterior  limbs  cut 
Oil',  and  the  greater  portion  of  the  os  innominatum  cleared  away  by  sawing  through  the 
symphysis  pubis  and  the  neck  of  the  ilium ;  the  dissection  of  all"  the  abdomino-pelvic 
portion  of  the  system,  and  that  of  the  terminal  branches  of  the  pneumogastric  nerve,  is 
then  proceeded  with.  The  anterior  limb  of  the  same  side  should  be  afterwards 
detached,  the  scapula  having  been  previously  sawn  across  its  middle  part,  and  the 
thorax  thrown  open  by  the  ablation  of  the  entire  costal  wall,  in  sawing  throu'jrh  the 
sternal  cartilages  below,  and  the  ribs  above,  at  their  superior  extremity  All  the 
thoracic  portion  of  the  ganglionic  nervous  apparatus,  and  the  pneumogastric  nerves 
may  then  be  prepared.  Nothing  more  remains  to  be  accomplished  except  the  dissection 
of  the  sympathetic  and  tlie  vagus  nerve  in  the  cervico-cephalic  region,  with  that  of  the 
spinal  nerve;  this  operation  is  not  attended  with  any  difficulty,  and  should  be  preceded 
by  the  extirpation  of  a  branch  of  the  inferior  maxilla.  It  is  useful  to  inject  the  arteries 
previously  ;  as  then  the  filaments  of  the  sympathetic  that  lie  alongside  the  vessels 
ot  the  diiieient  organs  in  the  abdominal  cavity  can  be  more  easily  followed. 

The  great  sympathetic,  also  named  the  trispJancTini^  system  (<nr\avxyov 
— an  intestine  or  viscus),  because  of  its  position  and  destination,  is  the  nervous 
apparatus  of  the  organs  of  vegetative  life. 

As  has  been  already  shown  in  the  general  consideration  of  the  nerves 
and  the  whole  nervous  system,  this  apparatus  has  for  its  base  two  long  cords 
extending  from  the  head  to  the  tail,  underneath  the  vertebral  column,  and  to 
the  right  and  left  of  the  median  line.  Towards  the  last  sacral  vertebra,  a 
portion  of  these  two  cords  converge  towards  each  other,  and  lie  beside  the 
ine<lian  coccygeal  artery.  Some  anatomists  think  that  the  great  sympa- 
thetic does  not  stop  at  this  point,  but  is  prolonged  beneath  the  coccygeal 
vertebrae,  where  it  enters  a  ganglion  that  has  been  described  of  late  years 
as  tlie  "  coccygeal  gland,"  and  whose  nature  has  been  very  much  contested. 

Each  cord  presents  on  itg  course  numerous  ganglia,  to  whose  presence  it 


782 


TEE  NERVES. 


Fig.  361. 


owes  its  chain-like  aspect ;  they  are  usually  elliptical  in  shape,  though  they 
may  also  be  round  or  semilunar ;  in  all  cases  they  are  studded  with  prolonga- 
tions at  their  borders.  Beneath  each  of  the  regions  of  the  spine  they  are  equal 
in  number  to  the  vertebrae,  with  the  exception  of  the  cervical  region,  in 
which  are  only  two — one  at  the  top,  the  other  at  the  bottom,  of  the  neck. 

To  this  chain  arrive  afferent  branches,  by  the  union  of  which  it  is  con- 
stituted ;  these  branches  are  furnished  by  the  nerves  of  the  medulla  oblongata 
and  the  inferior  spinal  branches,  except  those  of  the  coccygeal  region.  The 
afferent  branches  join  the  sympathetic  at  each  ganglion ;  but  as  there  are 
only  two  ganglia  in  the  region  of  the  neck,  the  afferent  filaments  of  the 
cervical  nerves  are  grouped  in  such  a  manner  as  to  reach  the  superior  and 
inferior  ganglion. 

Those  nerves  which  are  given  off  from  the  ganglia  to  be  distributed  to 
the  viscera,  are  named  the  efferent  or  emergent  branches.  They  are  interlaced 
around  the  arteries  to  reach  their  destination,  forming  pfewses  on  the  surface 
of  these  vessels. 

This  general  idea  of  the  disposition  of  the  great  sympathetic  is  sufficient 
to  show  that  its  double  ganglionic  chain  does  not  represent  two  particular 
nerves  arising  at  one  determinate  point,  and  ending  at 
another.  Properly  speaking,  they  have  neither  origin 
nor  termination ;  they  are  always  giving  off  branches 
which  are  as  frequently  replaced  by  others :  in  this  way 
they  might  be  compared,  in  this  respect,  to  the  median 
spinal  artery,  which  offers  somewhat  the  same  mode  of 
constitution — with  its  afferents  sui)i)lied  by  the  spinal 
branches  from  the  intervertebral  foramina,  and  its  efferents 
destined  to  the  substance  of  the  spinal  medulla. 

Structure. — The  ganglia  of  the  great  sympathetic 
differ  but  little  in  their  structure  from  the  spinal  ganglia, 
whose  constitution  has  been  already  made  known.  They 
have  an  envelope  of  connective  tissue,  which  sends  very 
fine  septa  into  their  interior.  In  the  spaces  are  cells 
a  little  smaller  and  paler  than  those  of  the  spinal  gan- 
glia ;  they  are  round,  or  furnished  with  poles  that  bring 
them  into  communication  with  the  afferent  and  efferent 
SYMPATHETIC  GAN-  nervc-tubcs ;  there  are  also,  in  the  ganglia,  tubes  which 
GLioN      FROM      A   only  pass  through  it,  and  merely  lie  beside  the  cells. 

The  afferent  branches  of  the  ganglia  have  the  white  tint 
of  the  cerebro- spinal  nerves,  and  are  named  the  grey 
nerves.  They  owe  their  colour  to  the  fibres  of  Hemak, 
which  they  contain  in  large  quantity.  With  these 
nucleated  fibres  are  associated  fine  nerve-fibres,  and 
double-contoured  fibres  which  pi-oceed  from  the  com- 
mtmicating  rami,  or  afferent  filaments  supplied  by  the 
spinal  nerves ;  these  fibres  often  leave  the  ganglia  to 
c,  c,  The   ganglion   pass  directly  to  organs. 

In  describing  the  sympathetic  chain,  it  is  divided  into 
five  sections :  a  cephalic,  cervical,  dorsal,  lumbar,  and 
sacral. 

1.  Cephalic  Portion  of  the  Sympathetic. 

This  is  composed  of  the  spheno-palatine,  ophthalmic, 
and   otic   ganglia,   all  of  which   communicate   with   the   superior  cervical 


PUPPY. 

,  a,  Trunk  of  the 
sympathetic  nerve ; 
b.  Communicating 
branches  from  a 
spinal  nerve ;  these 
divide  into  two  fas- 
ciculi which  pass 
upwards  and  down- 
wards in  the  trunk : 


composed  of  gan- 
glion cells ;  d,  Small 
branch,  probably- 
destined  to  accom- 
pany an  artery ;  e, 
Visceral  branch. 


THE  GREAT  SYMPATHETIC  NERVOUS  SYSTEM.  783 

ganglion.     Their  description  has  been  given  with  that  of  the  fifth  encephalic 
pail"  of  nerves. 

2.  Cervical  Portion  of  the  SympatJietic.  » 

The  cervical  section  of  the  ganglionic  chain  is  formed  by  two  large 
ganglia  placed  one  at  the  top,  the  other  at  the  bottom,  of  the  neck,  and  united 
to  each  other  by  an  intermediate  cord. 

A.  Superior  Cervical  or  Guttural  Ganglion  (Fig.  362,  1).  - — This 
ganglion  is  a  very  elongated  fusiform  body,  lying  beside  the  internal  carotid 
artery,  comprised  with  it  in  a  particular  fold  of  the  membrane  forming  the 
guttural  pouch,  and  therefore  situated  in  front  of  the  transverse  process  of 
the  atlas,  in  proximity  to  the  glosso-pharyngeal,  pneumogastric,  spinal,  and 
hypoglossal  nerves,  as  well  as  the  inferior  branch  of  the  first  cervical  pair. 
All  these  nerves  communicate  with  the  ganglion  by  slender  filaments,  and 
in  this  way  form  aroxmd  it  a  veritable  plexus,  which  has  been  designated  the 
guttural  plexus  by  Veterinary  Anatomists. 

Afferent  Branches. — These  are  communicating  filaments  belonging  to 
the  nerves  already  enumerated.  They  do  not  possess  sufficient  importance 
to  merit  particular  mention.  We  may  notice  the  existence  of  the  filaments 
supplied  by  the  inferior  branches  of  the  first  four  cervical  nerves. 

Emergent  Branches. — -These  are :  1,  Branches  accompanying  the 
internal  carotid  artery  into  the  cranium ;  2,  A  thick  fasciculus  which 
reaches  the  origin  of  the  three  terminal  divisions  of  the  common  carotid ; 
3,  Small  filaments  to  the  membrane  of  the  guttural  pouch  and  the  wall  of 
the  pharynx. 

The  following  are  the  principal  anatomical  characters  of  these  three 
orders  of  branches : 

a.  The  satellite  hranches  of  the  internal  carotid  artery  arise  at  Jhe  superior 
extremity  of  the  ganglion.  They  may  vary  in  number.  We  have  generally 
found  two  of  unequal  volume — a  posterior,  and  an  anterior,  which  is  the 
smallest.  They  interlace  around  the  internal  carotid  in  anastomosing  with 
each  other,  and  with  that  vessel  enter  the  cavernous  sinus,  where  they  form, 
by  their  divisions,  a  little  plexiform  apparatus  named  the  cavernous  plexus, 
the  diverse  branches  of  which  connect  it  with  several  of  the  encephalic 
nerves.  Among  these  branches  are  remarked :  1,  Some  filaments  joined  to 
analogous  filaments  from  the  opposite  side,  on  the  transverse  anastomosis 
which  unites  the  two  internal  carotids  in  the  cavernous  sinus ;  2,  A  branch 
lying  beside  the  great  petrosal  nerve,  and  concurring  in  the  formation  of  the 
Vidian  nerve,  which  enters  the  spheno-palatine  ganglion ;  3,  A  ramuscule 
going  to  the  ophthalmic  ganglion,  in  company  with  fibres  from  the 
ophthalmic  branch  of  the  fifth  pair ;  4,  Several  filaments  passing  to  the 
Gasserian  ganglion ;  5,  Branches  which  mix  with  the  fibres  of  the  three 
motor  nerves  of  the  eye. 

h.  The  inferior  carotid  fasciculus,  destined  to  the  terminal  extremity  of 
the  common  carotid,  escapes  from  the  inferior  part  of  the  guttural  ganglion. 
Frequently  at  its  origin  it  is  only  a  thick  cord,  but  ordinarily  it  is  composed, 
from  its  commencement,  of  several  branches  bound  to  one  another  by  com- 
municating filaments.  Eeaching  their  destination,  these  branches  meet 
ramuscules  emanating  from  the  glosso-pharyngeal  and  pneumogastric  nerves, 
and  anastomose  with  them  to  form,  around  the  origin  of  the  three  terminal 
branches  of  the  common  carotid,  the  so-called  carotid  plexus,  whose  rami- 
fications almost  exclusively  follow  the  external  carotid,  and  the  greater  part 
of  which  are  distributed  to  the  glands  and  the  salivary  lobules.     In  Man,  the 


3  ^ 
3  ^ 

S  'o 

3  "S 


THE  GREAT  SYMPATHETIC  NERVOUS  SYSTEM.  785 

division  which  follows  the  spheno-spinal  artery  passes  to  the  otic  ganglion  ; 
the  same  takes  jjlaee,  no  doubt,  in  animals. 

c.  The  guttural  ov  pharyngeal  Jilaments,  arising  from  the  anterior  border 
of  the  ganglion  and  the  interior  carotidean  fasciculus,  are  generally  very 
delicate.  Those  which  reach  the  superior  wall  of  the  pharynx  concur,  with 
the  glosso-pharyngeal  and  the  pneumogastric,  to  form  the  pharyngeal  plexus. 

B.  Inter:\ikdiate  Cord  of  the  Two  Cervical  Ganglia. — This  cord 
leaves  the  inferior  extremity  of  the  superior  cervical  ganglion,  lies  close 
beside  the  pneumogastric  nerve,  which  always  surpasses  it  in  volume,  and 
descends  to  the  entrance  of  the  thorax,  where  it  separates  from  the  vaons 
nerve,  and  joins  the  inferior  cervical  ganglion.  It  neither  receives  or  gives 
off  any  branch  in  its  course. 

C.  Inferior  Cervical  Ganglion  (Fig.  362,  2). —  Generally  thicker 
than  the  superior,  this  ganglion  is  placed  within  the  costal  insertion  of  the 
inferior  scalenus.  The  right,  always  a  little  more  anterior  than  the  other, 
is  applied  immediately  against  the  side  of  the  trachea.  That  of  the  left  side 
is  separated  from  it  by  the  oesophagus.  Both  are  related,  externally  to  the 
vertebral  artery. 

The  inferior  cervical  ganglion  is  very  liable  to  vary,  and,  become 
irregular  in  form.  It  is  sometimes  lenticular,  at  others  more  or  less 
elongated,  always  stellate,  and  not  unfrequently  double.  In  the  latter  case, 
which  is  perhaps  more  frequent  in  the  left  than  the  right,  its  two  portions 
are  distinguished  into  anterior  and  posterior :  the  last  forms  the  inferior 
cervical  ganglion,  properly  called  (Fig.  362,  2)  :  the  former  is  much  smaller, 
and  is  bound  to  the  other  by  a  wide  and  short  greyish  band,  constituting 
what  has  been  designated  in  Man  the  middle  cervical  ganglion  (Fig.  362,  3), 

In  front,  the  ganglion  which  we  are  describing  receives  the  cord  inter- 
mediate to  the  two  ganglionic  enlargements  in  the  region  of  the  neck,  either 
directly,  or  through  the  medium  of  the  middle  cervical  ganglion,  when  that 
is  present.  It  is  continued  backwards  with  the  dorsal  portion  of  the 
sympathetic  chain. 

Afferent  Branches. — These  are  two,  proceeding  from  the  cervical  pairs. 

One  is  a  thick  nerve,  satellite  to  the  cervical  vertebral  artery,  and  lodged 
with  it  in  the  foramina  of  the  cervical  vertebraB ;  it  is  formed  by  filaments 
emanating  from  the  second,  third,  fourth,  fifth,  sixth,  and  seventh  pairs  of 


to  2,  Cervical  poi-tion  of  the  sympathetic  chain ;  1,  Superior  cervical  ganglion,  in 
the  middle  of  the  guttural  plexus;  2,  Inferior  cervical  ganglion;  3,  Middle 
cervical  ganglion  ;  4,  Intermediate  cervical  cord,  intimately  united  at  its  middle 
portion  with  the  pneumogastric  nerve;  5,  Cardiac  nerves;  %,  Dorsal  portion  of  the 
sympathetic  chain;  7,  Great  splanchnic  nerve;  8,  Lesser  splanchnic  nerve;  9, 
Semilunar  ganglion,  centre  of  the  solar  plexus ;  10,  Portion  of  the  hepatic  artery 
encircled  by  its  plexus;,  11,  The  splenic  artery,  ditto ;  12,  The  gastric  artery, 
ditto  ,  13,  The  anterior  mesenteric  artery,  ditto  ;  14,  Kidney,  elevated,  receiving 
the  renal  plexus ;  15,  The  suprarenal  capsule  with  its  plexus ;  16,  Lumbo-aortic 
plexus ;  17,  LuinJmr  portion  of  the  sympathetic  chain  ;  18,  Posterior  mesenteric 
plexus;  19,  Branches  from  it  passing  to  the  anterior  mesenteric  plexus;  20, 
Spermatic  plexus;  21,  Branches  going  to  the  pelvic  plexus;  22,  Sacral jjortion  of 
the  sympathetic  chain;  23,  Pelvic  plexus;  24,  Afferent  branches  furnished  to  the 
sympathetic  by  the  spinal  pairs ;  24',  The  cord  which  receives  six  of  the  cervical 
ramuscules ;  25,  Pneumogastric  nerve ;  26,  Superior  laryngeal  ;  the  pharyngeal 
branch  is  seen  to  be  detached  from  the  pneumogastric  a  little  below  ;  27,  Inferior 
laryngeal  nerve  of  the  right  side ;  28,  That  of  the  left  side  at  the  point  where 
it  bends  round  the  arch  of  the  aorta ;  29,  Nerves  of  the  bronchial  plexus ;  30, 
Superior  oesophageal  branch;  31,  Inferior  ditto;  32,  Spinal  nerve;  33,  Hypo- 
glossal nerve ;  34,  Glosfo-pharyngeal  nerve,  represented  too  thick. 


786  TEE  NERVES. 

cervical  nerves,  and  thus  carries  in  a  mass,  to  tlie  great  sympathetic,  the 
contingent  of  afferent  nerve-fibres  of  the  majority  of  these  nerves 
(Fig.  362,  24'). 

The  other  branch  is  an  isolated  one,  proceeding  from  the  eighth  cervical 
pair. 

Besides  these  afferents,  there  ought  to  be  noticed  the  filaments  sent  by 
the  pneumogastric  nerve,  and  which  join  the  middle  cervical  ganglion,  when 
it  is  present.     See  the  description  of  the  pneumogastric  nerve. 

Emergent  Branches.  —  These  are  detached  from  the  posterior  and 
inferior  part  of  the  ganglion,  and  for  the  most  part  proceed  to  the  heart. 
Some  extremely  fine  filaments  go  to  the  anterior  mediastinum,  or  pass  on  to 
the  collateral  arteries  of  the  brachial  trunk. 

The  cardiac  nerves  (Fig.  362,  5)  cross  the  base  of  the  pericardium, 
alongside  the  common  aorta,  and  are  then  distributed  to  the  tissue  of  the 
auricles  and  ventricles.  Some  follow  the  divisions  of  the  pulmonary  artery, 
and  concur  in  the  formation  of  the  bronchial  plexus. 

To  arrive  at  the  heart,  these  nerves  accompany  the  axillary  arteries  and 
the  trachea,  giving  rise,  on  the  inferior  face  of  the  latter,  to  a  very  large 
fasciculus,  named,  in  Veterinary  anatomy,  the  tracheal  plexus  ;  this  is  single, 
and  is  traversed  from  behind  to  before  by  the  two  recurrent  nerves,  which  give 
or  receive  from  it  numerous  filaments. 

The  cardiac  nerves  in  the  Horse  are  five  in  number ;  two  proceed  from 
the  left,  and  three  from  the  right  cervical  ganglion.  Of  the  first  two,  one  is 
formed  by  easily-separated  filaments,  and  is  applied  to  the  left  brachial 
trunk  of  the  anterior  aorta,  which  it  follows  to  its  commencement.  There 
it  divides  into  several  ramuscules ;  some  of  these  pass  into  the  furrow 
between  the  right  auricle  and  the  origin  of  the  pulmonai-y  artery ;  the 
others  pass  between  the  latter  and  the  common  carotid,  to  reach  the  root  of 
the  lung.  This  nerve  furnishes  very  fine  filaments  to  the  anterior  border  of 
the  heart.  The  second  left  cardiac  nerve  commences  by  two  branches  that 
leave  the  middle  and  inferior  cervical  ganglia  ;  from  their  union  results 
a  long  cord  that  is  directed  downward,  backward,  and  to  the  right,  crossing 
the  lower  face  of  the  trachea ;  arrived  at  the  right  side  of  the  posterior  aorta, 
beneath  the  recurrent  nerve,  it  is  distributed  to  the  heart  and  lungs. 

The  cardiac  nerves  arising  on  the  right  side  are  thus  dis])osed.  The 
largest  emerges  from  the  middle  cervical  ganglion,  and  lies  alongside  the 
pneumogastric,  bending  with  it  beneath  the  axillary  artery,  and  becoming 
detached  a  little  beyond  that  vessel ;  here  it  receives  ramuscules  from  the 
left  recurrent  and  enters  the  base  of  the  heart,  after  giving  off  some  filaments 
that  pass  to  the  bronchial  plexus.  The  second,  much  smaller,  is  also 
detached  from  the  middle  ganglion,  receives  some  branches  from  the  right 
recurrent,  and  is  applied  to  the  surface  of  the  anterior  aorta  as  far  as  the 
upper  face  of  the  auricles.  Lastly,  the  third,  as  large  as  the  preceding, 
proceeds  from  the  right  recurrent,  the  inferior  cervical  ganglion,  and  the 
pneumogastric ;  it  is  imbedded  in  the  heart,  to  the  right  of  the  aorta. 

3.  Dorsal  Portion  of  the  Sympathetic  CJiain. 

The  cord  represented  by  this  portion  of  the  sympathetic  chain  leaves  the 
inferior  cervical  ganglion,  and  extends  from  before  to  behind,  towards  the 
diaphragm,  passing  beneath  the  superior  extremities  of  the  ribs — or  rather, 
below  the  vertebro-costal  articulations,  against  which  it  is  maintained  by  the 
pleura — and  crossing  the  intercostal  arteries.  It  is  continued  in  the  abdominal 


THE  GREAT  SYMPATHETIC  AERVOUS  SYSTEM.  787 

cavity  by  the  lumbar  portion,  after  passing  through  the  arch  of  the  superior 
border  of  the  diaphragm,  along  with  the  psoas  parvus. 

Along  its  course,  this  cord  exhibits,  at  each  intercostal  space,  a  small 
fusiform  ganglionic  enlargement — seventeen  in  all.  The  two  or  three  first 
are  most  frequently  absent ;  but  then  the  anterior  extremity  of  the  nerve 
has  for  some  extent  the  appearance  of  a  ribbon-shaped  ganglion,  which  seems 
to  be  due  to  the  elongation,  posteriorly,  of  the  inferior  grey  mass  of  the 
cervical  portion. 

Afferent  Branches. — Furnished  by  the  inferior  branches  of  the  dorsal 
nerves,  these  ramuscules  number  from  one  to  three  for  each  ganglion.  To 
proceed  from  the  intervertebral  foramina  to  the  sympathetic,  they  traverse  the 
superior  extremity  of  the  intercostal  space,  passing  sometimes  behind,  some- 
times before,  the  arteries  of  that  name. 

Emergknt  Branches. — ^A  very  few  delicate  branches  pass  to  the  pleurae ; 
those  which  demand  notice  are  the  great  and  lesser  splanchnic  nerves. 

a.  Great  splanchnic  nerves  (Fig.  362,  7).  —  This  commences  to  be 
detached  from  the  dorsal  chain  towards  the  sixth  or  seventh  ganglion,  is 
directed  backwards  by  the  external  side  of  that  chain,  receives  an  accessory 
branch  from  each  of  the  enlargements  it  passes  by,  except  the  last  two  or 
three,  and  enters  the  abdominal  cavity  through  the  arch  of  the  psoas  parvus, 
where  it  usually  looks  like  a  small  ganglionic  mass ;  after  which,  it  is 
inflected  inwards,  and  terminates  on  the  side  of  the  aorta,  between  the  coeliac 
and  mesenteric  trunks,  by  a  second  and  enormously  developed  mass — the  solar 
ganglion.  The  two  solar,  or  semilunar  ganglia,  as  they  have  also  been 
designated,  and  which  are  the  largest  in  the  body,  are  elongated  from  before 
to  behind,  and  flattened  from  above  to  below.  They  communicate  with  one 
another  by  means  of  a  wide  and  thick  greyish  cord,  which  encircles, 
posteriorly,  the  trunk  of  the  great  mesenteric  artery,  and  by  a  multitude  of 
filaments  which  pass  from  the  left  to  the  right,  in  front  of  that  vessel.  From 
this  arrangement  results  a  single  plexus  situated  at  the  inferior  face  of  the 
aorta,  between  the  origin  of  the  two  precited  arterial  trunks. 

This  plexus,  named  the  solar,  receives  some  branches  from  the  superior 
oesophageal  cord  of  the  pneumogastric  nerve.  It  subdivides  on  its  periphery 
into  several  secondary  plexuses,  which  leave,  as  from  a  centre,  the  principal 
network,  and  whose  ramifications,  very  large  and  numerous,  proceed  to  the 
neighbouring  organs  in  accompanying  the  arterial  divisions,  around  which 
we  see  them  interlacing  and  anastomosing  in  a  very  comijlicated  manner. 
It  is  for  this  reason  that  there  have  been  described  separately  :  1,  A  gastric 
2ilexus,  going  to  the  stomach,  on  whose  parietes  its  branches  anastomose 
with  those  of  the  pneumogastrics  ;  2,  A  hepatic  plexus,  destined  to  the 
liver,  duodenum,  pylorus,  and  pancreas ;  3,  A  splenic  plexus,  one  part  of 
w-hich  passes  to  the  spleen,  the  other  to  the  stomach;  4,  An  anterior 
mesenteric  plexus,  the  most  considerable  of  all,  is  distributed  to  the  same 
organs  as  the  artery  of  that  name ;  5,  A  renal  and  a  suprarenal  plexus  :  the 
latter  two  doubled,  and  scarcely  distinct  from  each  other,  their  terminal 
divisions  arriving  at  the  kidneys  and  suprarenal  capsules.  The  termination 
of  the  filaments  of  these  plexuses  has  been  already  described  in  the  Splancli- 
nology. 

It  is  necessary  to  add  to  this  rich  nervous  apparatus,  the  lumho-aortic 
plexus,  formed  by  the  large  and  numerous  branches  which  spring  from  the 
solar  plexus  behind  the  great  mesenteric  artery,  creep  along  the  sides  and 
the  inferior  face  of  the  aorta,  frequently  anastomose  with  each  other,  and 
reunite  at  the  posterior  mesenteric  plexus. 


788  THE  NERVES. 

b.  Lesser  splanchnic  nerve  (Fig.  362,  8^.  — Tliis  brauch  is  composed  of 
two  or  three  tilaments  that  emanate  from  the  last  subdorsal  ganglia,  and 
which,  instead  of  joining  the  great  splanchnic  nerve  like  the  others,  with 
which  they  connuuuicate  by  one  or  two  fine  divisions,  collect  in  a  short  thin 
cord,  whose  ramifications  pass  directly  into  the  solar  plexus,  or  are  con- 
founded with  the  nerves  of  the  kidney  and  the  suprarenal  capsule. 

4.  Lumbar  Portion  of  the  Sympathetic. 

This  is  a  cord  similar  to  that  of  the  dorsal  portion,  and  provided  with 
fusiform  ganglionic  enlargements  equal  in  number  to  the  pairs  of  lumbar 
nerves.  This  cord  is  applied  against  the  psoas  parvus,  near  the  common 
inferior  vertebral  ligament,  and  is  covered  on  the  left  by  the  aorta,  on  the 
right  by  the  posterior  vena  cava.  It  is  directly  continued  by  the  sacral 
portion  of  the  sympathetic  chain  at  the  lumbo-sacral  articulation. 

Afferent  Branches. — Furnished  by  the  inferior  branches  of  the  lum- 
bar nerves,  these  ramuscules  comport  themselves  exactly  like  those  of  the 
dorsal  region. 

Emergent  Branches. — These  are  short  filaments,  analogous  to  those 
which,  by  their  union,  constitute  the  splanchnic  nerves.  Their  number  is 
not  constant,  and  is  generally  less  than  that  of  the  ganglia.  Two  or  three 
join  the  lumbo-aortic  plexus ;  the  others  gain  the  origin  of  tiie  small 
mesenteric  artery,  anastomose  around  it  with  the  posterior  extremities  of 
the  branches  of  that  plexus,  and  thus  form  another  single  nervous  network 
designated  i\\e  posterior  mesenteric  plexus  (Fig.  362,  18). 

This  plexus,  in  whose  centre  is  a  more  or  less  voluminous  ganglion, 
sends  to  the  various  branches  of  the  small  mesenteric  arteiy  ramifications 
destined  for  the  walls  of  the  small  colon  and  the  rectum. 

It  supplies  besides  :  1.  Two  or  three  large  branches  which  follow  the 
posterior  mesenteric  vein,  and  join  the  anterior  mesenteric  plexus,  after 
giving  off  some  divisions  to  the  tissue  of  the   colic  mesentery  (Fig.  362, 

2.  Satellite  branches  to  the  two  spermatic  arteries,  constituting  the 
plexus  of  that  name  (Fig,  362,  20). 

3.  Two  or  threo  long  divisions  (Fig.  362,  21)  which  enter  on  each  side 
of  the  pelvis  by  passing  beneath  the  external  face  of  the  peritoneum,  and 
reach  the  lateral  plane  of  the  rectum,  where  they  meet  the  filaments 
emanating  directly  from  the  inferior  sacral  nerves.  From  the  anastomoses 
of  these  divisions  results  a  rich  nervous  network,  called  in  Man  the  hypo- 
gastric plexus,  and  whicli  we  have  designated  the  pelvic  plexus ;  this  net- 
work is  destined  to  all  the  organs  contained  in  the  pelvic  cavity  (Fig.  362, 
23). 

5.  Sacral  Portion  of  the  Sympathetic. 

A  continuation  of  the  lumbar  cord,  this  portion  of  the  sympathetic  chain  is 
situated  beneath  the  sacrum,  to  the  inner  side  of  the  inferior  sacral  nerves. 
It  oifers  four  very  elongated  ganglia,  which  communicate  v/ith  these  nerves 
by  one  or  more  filaments,  and  which  give  rise  to  several  very  fine  ramus- 
cules that  are  lost  in  the  cellular  tissue  on  the  inferior  face  of  the  sacrum. 

Its  posterior  exti*emity,  which  terminates  behind  the  great  sympathetic, 
does  not  always  comport  itself  in  the  same  manner.  We  sometimes  see  it 
become  attenuated  to  a  very  delicate  ramuscule,  which  passes  on  to  the 
median  coccygeal  artery,  and  anastomoses  with  that  of  the  opposite  side. 


THE  GREAT  SYMPATHETIC  NERVOUS  SYSTEM.  789 

But  sometimes,  also,  this  ramuscule  cannot  be  distinguished,  and  the  sub- 
sacral  cord  seems  to  be  abruptly  terminated  by  the  filament  of  com- 
munication from  the  last  sacral  pair. 

FuNCTiONS.^ — -The  functions  of  the  sympathetic  are  yet  but  little  known, 
notwithstanding  the  labours  of  many  physiologists,  at  whose  head  must  be 
placed  Claude  Bernard.  In  a  physiological  condition,  this  nerve  possesses 
an  extremely  obscure  sensibility,  but  which  may  become  very  acute  in 
pathological  cases.  It  conveys  to  organs  the  unconscious  motor  exci- 
tations originating  in  the  spinal  cord ;  and  through  the  filaments  it 
furnishes  to  the  vessels  —  the  vaso-motor  nerves — it  holds  under  its  control 
the  circulatory  phenomena,  especially  in  the  capillary  plexuses,  causing 
these  canals  to  dilate  or  contract,  and  thus  diminish  or  accelerate  the  flow 
of  blood  in  them.  By  this  action  on  the  blood-vessels,  it  may  have  a 
secondary  influence  on  the  nutrition  of  the  organs  to  which  these  vessels 
ai'e  distributed. 

DIFFEKENTIAL   CHARACTEKS   IN   THE   GREAT   SYJIPATHETIC   OF   OTHER   THAN 
SOLIPED    ANIMALS. 

In  all  the  doruesticnted  mammals,  the  general  disposition  of  the  great  sympathetic  is 
very  similar ;  so  that  there  are  but  few  and  sliglit  differences  to  note. 

In  the  Ox,  the  cervical  filament  does  not  arise  from  the  lower  extremity  of  the 
superior  ganglion,  but  from  its  middle  portion  ;  it  is  divisible  into  two  or  three  filaments 
for  a  certain  distance,  after  which  it  lies  beside  the  pneumogastric.  The  mmuscule 
that  leaves  Ihe  lower  end  of  the  cervical  ganglion  is  very  large,  and  reaches  the  division 
of  the  common  carotid,  that  which  accompanies  the  internal  carotid  artery  is  also  of  a 
considerable  size.     ^Ruminants  have  13  thoracic  and  6  lumbar  ganglia.; 

In  the  Bog.  the  cervical  symijathetic  cord  is  closely  united  with  the  pneumogastric, 
and  it  is  not  possible  to  separate  them  from  each  other,  as  can  be  done  in  Solipeds  ami 
Ruminants.     (In  the  Carnivora  there  are  13  thoracic  and  7  lumbar  ganglia.) 

The  Pifi  has  a  superior  cervical  ganglion,  which  is  fusiform  and  very  long  ;  at  its 
lower  extremity  it  gives  off  several  filaments,  one  of  which  lies  beside  the  pneumogastric 
in  the  cervical  region,  but  separates  from  it  to  join  the  middle  cervical  ganglion ,  the 
others  pass  to  the  tenth  nerve,  and  are  confounded  with  it  at  the  ganglionic  enlargement 
it  sliows  behind  the  pharynx.  At  the  entrance  to  the  chest,  a  branch  separates  from 
the  pneumogastric,  passes  along  with  the  axillary  arteries,  and  finally  enters  the  heart. 
This  branch  is  perhaps  formed  by  the  filaments  cf  the  sympatiietic  that  joined  the 
pneunjogastric  at  the  upper  part  of  the  neck.  iThe  inferior  cervical  ganglion!  according 
to  Leyh,  is  completely  isolated  from  the  thoracic  ganglion.  The  Vig  has  14  thoracic 
and  7  lumbar  ganglia. 

COMPAEISOV   OF   THE   GREAT   SYMPATHETIC    OF   MAN   WITH   THAT   OF   ANIiMALS. 

It  is  divided  and  disposed  as  in  animals.  The  rerv'cal  portion  is  composed  of  a 
superior  fusiform  ganglion,  from  which  emerge  many  branches  which  have  been  studied 
with  the  greatest  care.  There  are  described  ;  1,  Superior  or  intercranial  branches ;  2, 
External  or  anastomosing  branches  with  the  first  four  spinal  nerves;  3,  Internal  or 
viscei-al  branches,  which  mix  with  the  pharyngeal  and  laryngeal  filaments  of  the 
pneumogastric ;  4,  Anterior  or  external  carotideal  branches,  which  pass  to  the  common 
carotid  and  the  middle  of  a  small  ganglion,  the  intercarotid ;  5,  Posterior,  muscular,  or 
osseous  branches.  All  these  are  present  in  the  Horse.  A  cervical  filament  and  tw.> 
inferior  ganglia — middle  and  inferior — complete  this  region,  of  which  there  is  nothing 
more  to  be  said. 

The  thoraric  portion  is  absolutely  identical  in  its  disposition  with  that  of  animals  ;  it 
gives  rise  to  a  great  splanchnic  nerve,  and  terminates  in  the  semilunar  ganglia. 

There  arc  no  differences  to  note  in  the  lumbar  and  sacral  portions,  which  we  have 
described  as  the  pelvic. 

53 


790  TEE  NERVES. 


CHAPTER  IV. 


THE   NERVOUS   SYSTEM    IN    BIRDS. 

Peotective  Parts  op  the  Cerebro-spinal  Axis. — The  protective  parts  of  the 
nervous  centres  are  the  same  in  all  vertebrate  animals ;  consequently,  there  is  nothing 
to  remark  regarding  those  of  Birds.  The  envelopes  or  meninges  are  three  in  number, 
and  disposed  as  in  mammals. 

"  The  falx  cerebri  is  found  in  birds ;  in  tlie  TurJcey  it  lias  the  form  of  the  segment  of 
a  circle,  and  extends  from  the  middle  of  the  interval  of  tne  openings  for  the  olfactory 
nerves  to  the  tentorium  cerebelli.  The  falx  cerebelli  is  absent ,  the  tentorium  is  small 
and  sustained  by  a  bony  plate,  and  there  are,  in  addition,  two  |  articular  folds,  one  on 
■  each  side,  that  separate  the  hemispheres  from  the  tubercula  quadrigemina." — Cuvier. 
Owino-  to  the  absence  of  the  falx  cerebelli,  the  meninges  of  birds  are  closer  together 
than  Ihose  of  Solipeds  or  Man.  According  to  Leydig,  the  falx  cerebri  is  partially 
ossified  in  birds. 

Spinal  Cord. — In  Birds,  the  spinal  cord  is  perforated  by  a  CL-ntral  canal,  and  also 
offers,  as  in  mammals,  two  enlargements- a  cervico-dorsal  and  lumbar.  It  is  prolonged 
into  the  coccygeal  vertebrse,  and  thus  furnishes  annther  proof  against  the  nssertion  of 
certain  naturalists,  who  desire  to  establish  a  relation  between  the  length  of  the  spinal 
cord  posteriorly,  and  the  development  of  the  coccygeal  region.  The  two  fasciculi  of  tiie 
medullary  axis  are  separated  from  one  another  at  the  lumbar  enlargement,  and  after- 
wards join  in  the  sacral  region.  Between  them  is  an  elliptical  space,  the  rhomboidal 
sinus,  which  is  filled  by  transparent  gelatinous  connective  substance — a  kind  of  efflor- 
escence of  the  ependymis  of  the  central  canal. 

Encephalon. — In  a  medium-sized  Fowl,  the  encephalon  weighs  about  2J  drams,  and 
comprises  the  three  portions  present  in  the  mammalia. 

The  medulla  oblmgata  is  not  divided  into  two  sections  by  the  pons  Varolii,  which  is 
absent  in  birds;  the  crura  cerebelli  are  immediately  connected  with  the  corpora 
restiformia.  The  lower  face  of  the  isthmus  is  very  convex  posteriorly ,  in  front,  the 
tubercula  bigemiiia  are  united  to  each  other  by  a  comparatively  large  transverse  cord, 
formed  by  the  optic  nerves  intercrossing  in  the  median  line.  The  superior  face  is 
depressed  above  the  cerebellum,  so  as  to  consftute  a  fourth  ventricle,  also  shaped  like 
the  point  of  a  pen ;  in  front  of  this  ventri'de  aie  the  tubercula  bigemina.  These  are 
two  voluminous  tubercules  separated  from  each  other  above,  where  they  embrace  the 
cerebellum,  and  salient  on  the  sides  of  the  lower  face.  They  are  hollow  internally,  and 
communicate  with  the  aqueduct  of  Sylvius,  the  tlialami  optici  are  little  developed. 

The  cerebellum  is  almost  reduced  to  the  median  lobe,  the  lateral  lobes,  situated 
behind  and  below  it,  being  very  small  and  conical.  By  its  anterior  extremity,  this 
-cerebral  gmglion  passes  between  the  corpora  bigemini,  and  touches  the  cerebral  liemi- 
-spheres.  The  cerebellum  is  annulated  transversely  to  its  surface,  and  between  the 
principal  furrows  are  secondary  ones,  as  in  mammals.  The  white  substance  forms,  in  its 
(interior,  an  arborisation  in  relation,  by  the  number  of  its  branches,  with  the  simplicity 
.  observed  on  the  surface  of  the  organ.  In  the  centre  of  the  cerebellum  of  birds  is  a 
■small  cavity  communicating  with  tlie  fourth  ventricles. 

The  cerebrum,  divided  into  two  hemispheres  by  a  shallow  sulcus,  has  the  shape  of 
?the  .heart  on  a  playing  card,  more  particularly  when  viewed  on  its  lower  face.  The 
convcilutions  are  absent  on  the  upper  and  lateral  faces  of  the  organ,  and  on  the  inferior 
is  a  vestige  of  the  fissure  of  Sylvius,  which  is  directed  obliquely  forward  and  outward. 
The  olfactory  lobes  are  little  developed,  and  are  placed  together  in  the  median  line. 

The  two  ventricles  are  confounded,  there  being  no  corpus  callosum  nor  septum 
iuoidum.  There  is  no  reflected  portion  in  tlie  ventricle ;  consequently  the  hi|>pocampi 
and  mastoid  lobules  are  absent ;  the  corpora  striata  are,  on  the  contrary,  large  and 
-occupy  nearly  the  whole  floor  of  the  ventricles. 

Cranial  Nerves. — These  are  twelve  pairs,  as  in  mammals;  and  their  origin  is 
analogous,  if  not  identical;  the  only  trifling  diflferences  pertaining  to  the  pons  Varolii 
and  the  convexity  of  the  lower  face  of  the  isthmus. 

Olfactory  nerve. — We  have  mentioned  above  how  this  is  formed  at  the  anterior 
paction  of  the  cerebral  hemispheres. 

Optic  merve. — It  appears  to  be  detached  from  the  tubercula  bigemini,  and,  after  a 
■very  short  course,  to  intercross  with  that  of  the  opposite  side.  In  certain  birds,  especially 
in  the  diuitnal  rapacious  kinds,  the  optic  nerves  are  conslituted  by  fasciculi  of  undulating 
nervy-tiihee. 


TEE  NERVOUS  SYSTEM  IN  BIBDS.  791 

Common  motores  oculorum. — Pathetici. — External  motores  oculorum. — There  is  nothing 
particular  to  be  cited  respecting  tliese. 

Trigeminal  nerce. — Tliis  nerve  divides  into  three  principal  branches,  as  in  tlie 
(lonaesticated  animals.  The  ophthalmic  branch  has  a  nasal  ranauscule  that  becomes 
supertiuial,  and  exttuds  to  the  extremity  of  the  beak;  as  well  as  a  third  filament  that 
is  lost  around  the  inferior  orifice  of  the  nasal  cavities 

The  ,«M/«'r/or  maxillary  issues  from  the  cranium  by  the  opening  through  which  the 
lower  maxillary  nerve  passes,  creeps  below  the  orbit,  traverses  the  maxillary  bone,  and 
terminates  on  the  sides  of  the  beak  by  filaments  that  resemble  the  infra-orbital 
ramuscules  of  the  Horse. 

The  inferior  maxillary  furnishes  two  branches  :  one  passes  through  the  dental  canal 
and  arrives  at  the  extremity  of  the  lower  mandible ;  the  other  is  spread  in  the  sub- 
corneus  integuments  of  the  same. 

Facial  rierve. — This  is  small  in  birds.  "It  is  distributed  to  tlie  muscles  of  the  jaws 
and  the  small  muscles  which  erect  the  feathers  of  the  crest.'" — Cuvier. 

Glosso-pharyngeal  nerve. — This  calls  for  no  remark. 

Pneumogastric  nerve. — There  are  few  diflerences  observed  in  this ;  it  is  as  extensive 
as  in  mammals,  and  its  anastomoses  and  relations  are  nearly  the  same.  It  is  not  en- 
tirely formed  at  its  exit  from  the  cranium,  and  always  offers  two  or  three  constituent 
filaments  that  join  it,  and  are  confounded  at  some  distance  from  the  point  of  emergence. 
The  recurrents  furnish  ramuscules  to  the  crop. 

Spinal  accessory  verve. — This  likewise  has  a  medullary  root  that  appears  at  the 
third  cervical  vertebra  ;  it  runs  along  with  the  vagus  nerve  to  become  superficial. 

Hypoglossal  nerve. — The  same  origin  as  in  quadrupeds.  Where  it  crosses  the  pneu- 
mogastric, it  detaches  a  long  filament  that  passes  along  with  the  jugular  vein  towards 
the  chest.  On  the  sides  of  the  larynx  it  bifurcates  ,•  one  branch  proceeds  forward 
beneath  the  tongue,  the  other  follows  in  the  same  direction,  but  on  the  upper  surface  of 
that  organ. 

Spinal  Nerves. — We  need  only  notice  the  nerves  of  the  wing  and  pelvic  limb,  the 
others  being  disposed  in  a  similar  manner  to  those  above  described. 

Brachial  plexus. — Three  princiiJal  branches — the  last  cervical  and  first  two  dorsal — 
form  this  plexus  in  Pulmipeds;  in  the  Gallinacem  there  are  four  —  the  last  three 
cervical  and  first  dorsal.  These  branches  anastomose  beneath  the  deep  face  of  the 
scapulo-liumeial  articulation.  When  fully  constituted,  the  plexus  gives  oft'  some  col- 
lateral ramuscules,  and  terminates  by  two  fasciculi  of  branches.  The  first  collateral 
goes  to  the  deep  pectoral  muscle  :  another  is  distributed  to  the  muscles  surrounding  the 
head  of  the  humerus,  as  well  as  to  the  articular  capsule.  The  fasciculi  of  terminal 
branches  may  be  distinguished,  after  their  situation,  as  anterior  and  posterior.  The 
latter  represents  the  internal  cutaneous  and  radial  nerve ;  it  gives  off  muscular  and 
cutaneous  lamuscules  that  extend  to  the  digits  at  the  extremity  of  the  wing.  The 
anterior" fasciculus  is  larger,  and  is  also  extended  to  the  whole  of  the  limb,  being  ex- 
pended in  motor  and  sensitive  filaments;  near  its  oiigin  it  furnishes  ramuscules  to  the 
superficial  pectoral  muscle.  This  fasciculus  represents  the  median,  ulnar,  and  anterior 
brachial,  or  musculo-cutaneous  of  mammals. 

Lumbosacral  plexus. — Two  lumbar  and  foiir  sacral  nerves  constitute  this  plexus. 
In  the  Fold  it  is  distinctly  divisible  into  two  poitions,  an  anterior  and  posterior, 
considerably  wide  apart. 

The  anterior  portion  is  composed  of  the  lumbar  branc'ies  and  a  portion  of  the  first 
sacral ;  their  fusion  takes  place  on  the  salient  bony  ridge  that  separates  the  lumbar 
from  the  sacral  regions.  It  gives  origin  to  four  or  five  brandies,  among  which  are 
clearly  discernible :  1,  A  filament  to  the  fascia  lata  muscle ;  2,  A  crural  or  femoral  nerve  ,■ 
3,  An  internal  saphenous  nerve  that  descends  to  the  leg;  4,  An  obturator  nerve.  The 
latter  is  very  slender,  and  directed  downwards  and  backwards,  passing  into  the  muscle 
that  closes  the  obturator  foramen. 

The  posterior  portion  comprises  a  portion  of  the  first  sacral,  and  the  whole  of  the 
three  succeeding  nerves.  These  are  directed  outwards,  towards  the  sciatic  notch,  where 
they  unite;  during  their  course  in  the  interior  of  the  pelvis,  they  are  surrounded  by  the 
tissue  of  the  kidney.  The  distribution  of  this  portion  of  the  plexus  resembles  that  of 
the  Horse.  Thus,  in  leaving  the  sciatic  notch,  it  gives  oif  the  anterior  and  posterior 
gluteal  nerves,  then  two  long  branches  that  lie  together  as  far  as  the  gemelli ;  these 
branches  are  :  1,  The  great  sciatic,  with  a  ramuscule  for  the  gemelli  and  the  posterior 
tibial  muscles ;  2,  The  external  popliteal,  which,  outside  the  superior  extremity  of  the 
leg,  divides  into  the  musculo-cutaneous  and  anterior  tibial  nevre 


BOOK  VII. 

Apparatus  of  Sense. 

Among  the  nerves  described  in  the  preceding  book,  those  which  have  been 
designated  sensory  nerves  have  for  their  principal,  or  even  exclusive  function, 
the  carrying  to  the  brain  the  excitations  derived  from  the  surrounding 
physical  world.  These  nerves  are,  therefore,  the  essential  instruments  of 
sensation,  and  the  organs  to  which  they  are  distributed  constitute  the 
APPARATUS  OF  THE  SENSES.  Thcse  are  admirably  disposed  for  the  re- 
ception of  the  cerebral  excitations,  and  are  five  in  number :  the  apparatus 
of  touch,  taste,  smell,  vision,  and  hearing.  The  principal  charateristics  of  these 
will  be  briefly  enumerated 


CHAPTEE  I. 


APPARATUS    OF   TOUCH. 


The  sense  of  touch  is  destined  for  the  appreciation  of  tactile  sensations, 
and,  incidentally,  those  resulting  from  variations  of  temperature.  The 
apparatus  composing  it  is  formed  by  the  peripheric  radicles  of  the  nerves 
of  general  sensibility  distributed  in  the  skin :  the  resisting  membrane 
closely  investing  the  whole  of  the  body,  and  continuous,  at  the  margin 
of  the  natural  openings,  with  the  mucous  or  internal  membrane. 

The  entire  skin,  therefore,  represents  the  organ  of  toucli ;  but,  as  in  Man, 
this  membrane  has  certain  privileged  regions  which  are  more  active  than 
others  in  the  exercise  of  this  faculty  :  these  are  the  four  extremities  and  the 
lips. 

The  structure  of  the  skin,  though  pertaining  to  general  anatomy,  shall  be 
studied  here  somewhat  in  detail,  and  then  the  arrangement  of  its  appendages 
— the  hair  and  horny  productions — will  be  examined. 

Article  I. — The  Skin  Proper. 

The  skin,  properly  speaking,  is  composed  of  two  layers :  the  derma  and 
epidermis. 

The  Derma. — The  derma  or  chorion  (corium  cutis),  forms  nearly  the 
entire  thickness  of  the  membrane.  Its  inner  face  adheres  more  or  less 
closely  to  the  subjacent  pai'ts,  through  the  medium  of  a  cellulo-adipose 
expansion.  Its  external  face,  covered  by  the  epidermis,  which  it  secretes  (or 
forms),  is  perforated  by  openings  through  which  the  hairs  pass,  or  through 
which  the  secretion  of  the  sudoriparous  and  sebaceous  glands  is  thrown  out 
upon  the  surface  of  the  skin ;  this  external  face  also  shows  a  multitude  of 
little  elevations  termed  papillce,  in  which  the  majority  of  the  nerves  terminate 


THE  INTEGUMENTARY  APPENDAGES. 


793 


The  derma  is  not  of  the  same  thickness  everywhere,  being  much  tliinner 
where  it  is  protected  from  external  injury,  as  on  the  under-surface  of  the 
belly,  the  iuuer  side  of  the  legs,  thighs,  etc.;  it  is  also  thin  around  the 
margin  of  the  natural  openings,  to  permit  the  transition  between  the  two 
membranes,  and  endow  these  apertures  with  their  necessary  dilatability. 


Fisr.  363. 


SECTION   OF   HORSt'S   SKIN  ;   FROM   WING   OF   THE   NOSTRIL. 

E,  Epidermis;  d,  Derma;  1,  Horny  layer  of  the  epidermis;  2,  Rete  mucosum  ;  3, 
Papillary  laver  of  the  derma ;  4,  Excretory  duct  of  a  sudoriparous  gland ;  5, 
Glomerule  of  a  sudoriparous  gland ;  6,  Hair  follicle  ;  7,  Sebaceous  gland ;  8, 
Internal  sheath  of  the  hair  follicle  9,  Bulb  of  the  hair  •  10,  Mass  of  adipose 
tissue. 


Fig.  364. 


Stkucture. — The  derma  is  composed  of  fasciculi  of  conjunctival  tissue 
interwoven  and  matted  in  a  solid  manner,  and  in  the  meshes  of  which  are  some 
smooth  muscular  fibres,  which,  by  their  contraction,  produce  the  condition  of 
the  skin  known  as  the  cutis  anserina  (goose-skin).  Somewhat  loosely  woven  in 
its  deepest  part  to  form  the  reticular  layer  (or  coritim),  the  derma  contains 
the  roots  of  the  pilous  follicles,  the  sudoriparous  (or  siceat)  glands,  and  small 
masses  of  adipose  tissue  ;  superficially,  its  structure  is  very  condensed,  to 
constitute  the  papillary  layer,  whose  uppermost 
limit  forms  an  amorphous  border. 

The  papillce  are  of  two  kinds — vascular 
and  nervous,  and  are  regularly  arranged  in 
parallel  series :  they  are  most  numerous  in 
those  parts  of  the  skin  specially  destined  for 
the  exercise  of  touch,  as  at  the  lips,  in  the 
keratogenous  membrane  (of  the  foot),  and 
other  parts  where  sensibility  is  very  acute — 
such  as  the  scrotum,  sheath,  and  integuments 
of  the  penis.  The  papillary  prolongations  of 
the  derma  are  conical  or  fungiform,  and  pedi- 
culated :  their  dimensions  are  very  variable ; 
measuring  from  yl^th  to  g^-eth  of   an  inch  in  length,  and   from  -^th  to 


CAPILLARY    LOOPS    IN    THE    CUTA 
NEOUS  PAPILLA   OF   THE   LIPS. 


794 


TEE  APPARATUS  OF  THE  SENSES. 


■gi^jth  of  an  inch  in  width  at  their  base.  The  nervous  papillae  are  the 
organs  of  touch,  and  contain  either  the  corpuscula  tactus  (or  axile  bodies)  of 
Meissner  or  of  Kraiise. 


Fig.  365. 


TACTILE   PAPILLAE   FROM   THE   SKIN,   SHOWING  THE 

tactile  corpuscles,  OR  "  axile  bodies." 
A,  In  the  natural  state ;  B,  Treated  with  acetic  acid. 


The  Sebaceous  Glands 
lie  beside  the  hair  follicles, 
each  hair  being  flanked  by 
two  glands.  These  small 
organs  are  composed  of  a 
very  granular  epithelium,  and 
are  usually  oval  in  shape. 
(They  are  imbedded  in  the 
substance  of  the  derma,  and 
present  every  degree  of  com- 
plexity, from  the  simplest 
follicle  to  the  compoxmd 
lobulated  gland.  In  some 
situations,  their  excretory 
ducts  open  independently  on 
the  surface  of  the  epidermis. 
Those  associated  with"  the 
hairs  are  raceiform  and  lobu- 
lated, consisting  of  glandular 
vesicles,  which  open  by  short 
pedunculated  tubuli  into  a 
common  excretory  duct,  and 
the  latter,  after  a  short  course, 
into  the  hair  follicle.  In  some 
parts  the  ducts  are  short  and  straight ;  in  others,  where  the  skin  is  thick,  they 
are  spiral.  They  are  lined  by  an  inversion  of  the  epidermis,  which  forms  a 
thick  and  funnel-shaped  cone  at  its  commencement,  but  soon  becomes  soft 
and  uniform.  Sebaceous  glands  are  met  with  in  all  parts  of  the  body,  but 
are  most  abundant  in  those  parts  which  are  naturally  exposed  to  the  influence 

of  friction,  or  require  to  be  supple.  Miiller 
found  in  the  Pig  a  special  cutaneous  gland, 
somewhat  resembling  the  sebaceous  glands. 
It  is  situated  on  the  inner  and  posterior  aspect 
of  the  knee,  and  is  from  fths  to  2  inches  in 
length,  and  from  ^  to  ^  inch  in  width.  In  the 
Sheep,  there  is  found  in  the  skin  between  the 
claws,  a  particular  inversion  of  the  integument 
that  forms  a  small  elongated  pouch,  curving 
upwards  and  terminating  in  a  cul-de-sac.  This 
is  the  interungulate  gland,  sinus,  or  hijlex  canal 
(sinus  cutaneus  ungularum) ;  it  secretes  a  viscid 
matter  from  glands  which,  according  to  Erco- 
lani,  are  analogous  to  the  sebaceous  glands. 
The  pouch  is  lined  with  very  fine  hairs.) 

The  Sudoriparous  Glands  are  deeper  situ- 
ated than  the  last  (passing  even  into  the 
subcutaneous  areolar  tissue,  where  they  are 
surrounded  by  adipose  cells).  They  consist 
of  a  convoluted  tube  (or  several  tubuli  pro- 
duced by  dichotomous  subdivision)  imbedded  in  the  reticular  layer  of  the 


Fis.  366. 


INTERUNGULATE  GLAND  OF  SHEEP. 

a,  inner  aspect  of  first  phalanx ;  6, 
Hoof,  or  claw ;  c,  Interungulate 
gland ;  d,  Orifice  of  its  duct. 


THE  INTEGUMENTARY  APPENDAGES. 


795 


derma  (or  corium),  and  forming  an  elliptical  glomerule,  generally  lying 
obliquely  to  the  surface  of  the  skin  in  the  Horse.  The  excretory  canal  is 
detached  from  this  glomerule,  and  passes 
through  the  derma  and  epidermis  in  a  spiral 
manner. 

The  hlood-vessels  form  a  very  rich  network 
in  the  papillary  layer  of  the  derma,  and  also 
surround  the  sebaceous  and  sudoriparous 
glands.  The  lymphatics  are  disposed  like  the 
capillaries. 

The  nerves  are  arranged  in  two  layers  : 
one  loosely  distributed  in  the  corium  ,  the 
other  is  very  close,  and  is  lodged  in  the  papil- 
lary layer  of  the  derma,  which  is  traversed 
by  recurrent  fibres  giving  ofi"  tubes  that  pass 
into  the  nervous  corpuscles  of  the  papillae. 

Fior.  367. 


VERTICAL    SECTION    OP     THE    SKIN    TREATED     WITH    A 

SOLUTION  OF  CAUSTIC  SODA,  showing  the  branches  of 
cutaneous  nerves,  a,  b,  inosculating  to  form  a  termmal 
plexus,  of  which  the  ultimate  ramifications  pass  into 
the  papillae,  c,  c,  a 

Epidekmis. — The  epidermis  is  a  thin  pel- 
licle, covering  the  superficial  face  of  the 
derma ;  it  is  destitute  of  nerves  and  blood- 
vessels, and  is  formed  of  cells  which  are 
being  continually  deposited  on  the  corium  ; 
these  cells  become  flattened  in  layers  as  they 
are  pushed  up  from  the  latter,  and  are  des- 
troyed by  friction  on  the  surface  of  the  skin. 
The  deep  face  of  the  epidermis  is  moulded 
on  the  upper  surface  of  the  derma;  con- 
sequently, it  lodges  the  papillae,  and  dips  into 
the  follicles  and  excretory  ducts  of  the  glands 


SUDORIPAROUS   GLAND,  MAGNIFIE1> 
40    DIAMETERS. 

a,  a,  Contorted  tubes  composing  the 
gland,  and  uniting  m  two  ex- 
cretory ducts,  6,  6,  which  joia 
into  one  spiral  canal  that  per- 
forates the  epidermis  at  c,  and 
opens  on  its  surface  at  d;  the 
gland  IS  imbedded  in  fat  vesi- 
cles, e,  e. 


of  the  skin  ;  its  external  face  is  not  a  very 
exact  repetition  of  the  surface  of  the  derma,  and  is  covered  with  hair.  The 
epidermis  tends  to  equalise,  and  to  fill  up,  the  depressions  existing  between: 
the  papillaB. 


796 


THE  APP ABATIS  OF  THE  SENSES. 


Fi2.  369. 


Structure. — The  epidermis  comprises  two  layers,  whicli  are  not  very 
distinct  from  each  other  in  the  Horse.  The  deep  layer,  or  refe  mucosum.  is 
composed  of  soft,  nucleated,  pigmentary  cells,  which  are  round  on  the  surface 
of  the  derma,  and  polyhedric  elsewhere.  The  superficial,  or  Iwrny  layer,  is 
constituted  by  hard,  horny,  flattened  cells,  which  still  contain  some  pigment- 
granules,  and  are  insensibly  confounded  with  those  of  the  rete  mucosum. 

(The  theory  of  growth  of  the  epidermis  is  believed  to  be  as  follows  : — a 
layer  of  plastic  lymph  is  thrown  out  on  the  surface  of  the  derma,  and  is 
converted  into  granules,  which  are  termed  cell-germs,  or  cytoblasts.  These 
imbibe  serum  from  the  lymph  and  adjacent  tissues,  so  that  the  outermost 
covering  of  the  cytoblast  is  gradually  distended  ;  the  latter  becomes  a  cell, 
and  its  solid  portion,  which  always  remains  adherent  to  some  point  of  the 
inner  surface  of  the  cell  membrane,  forms  the  nucleus  of  the  cell.  Within 
this  nucleus  one  or  more  nuclei  are  developed ;  these  are  named  nucleoli. 
The  process  of  imbibition  continuing,  the  cell  becomes  more  or  less  spherical ; 
so  that,  after  a  certain  time,  the  papillary  layer  of  the  derma  is  covered  by  a 
thin  stratum  of  spherical  cells  pressed  closely  together,  and  corresponding 
with  every  irregularity  of  the  papillae.  New  cells  being  continually  produced 
before  the  formation  of  the  others  has  been  quite  completed,  these  are  removed 
in  layers  further  and  further  from  the  surface  of  the  derma,  and  becoming 
subjected  to  the  influence  of  physical  laws,  their  fluid  contents  evaporate : 
they  collapse,  flatten,  and  gradually  assume  an  elliptical  shape ;  then  they 
are  a  mass  of  completely  flat  cells,  with  an  included 
nucleolated  nucleus,  and  finally  become  a  thin  mem- 
branous scale,  in  which  the  nucleus  is  scarcely  appa- 
rent). 

In  Solipeds  and  other  animals,  the  epidermis  is 
generally  dark-coloured,  from  the  presence  of  pig- 
ment corpuscles,  the  number  of  which  increases  with 
their  depth  in  the  membrane.  This  coloration  is 
intended  to  prevent  the  rubefacient  effects  of  the 
heat  of  the  sun's  rays,  by  augmenting  the  absorb- 
ing and  dispersing  power  of  the  cutaneous  surface. 
In  the  majority  of  cases,  this  coloration  is  absent  in 
the  Sheep,  whose  skin  is  protected  by  a  thick  fleece ; 
and  also  in  the  Pig,  whose  habits  in  the  wild,  as  in 
a  domesticated  condition,  keep  it  out  of  the  direct 

OBLIQUK   SECTION   OF   EPI-     ^CtlOU  01  the  SUU. 

DERMIS,    SHOWING  THE  (lu  somc  rcgious  of  the  body  of  all  animals,  the 

PEOGREssivE  DEVELOP-   gldn  foTius  foMs,  as  at  the  junction  of  the  fore-limb 

NENT  ceL!^'    ''*''''''''  "^'^^  *^^  ^^"^V'  *^^  ^'^^k'  "*^^"^  between  the  thighs. 

„    ,  .         '  ,,      In  the  Cow,  it  forms  the  large  pendulous  layer  at 

a,  JNuclei  restincr  upon  the    ,i       .i         .  i  i  ,    i  ,1      <,  i       i         <>         i 

surface  of  the  derma  f  ■   ''^^  throat  and  breast,  known  as  the  "  dewlap  ;     and 

these  nuclei  are  gradu-   in  the  Goat  and  Pig,  it  not  unfrequently  constitutes 

ally  developed  into  cells   teat-like  prolongations    depending  from  the   throat, 

e,  and  d,  and  the    which  nearly  always  contain  a  small  cartilaginous 

nucleus  and  some  muscular  fasciculi.     The  thickness 

of  the  epidermis  is  sometimes  greatly  increased  by 

wear  and  friction,  as  we  frequently  see  in  the  skin 

covering  the  knees  of  Sheep,  etc.) 

(The  functions  of  the  skin  are,  as  we  have  seen,  tactile  and  secretory ;  in 

addition,  it  is  eminently  protective.     Its  secretory  action  is  always  more  or 

less  active,  but  the  production  of  perspiration  is  greatest  when  the  body  is 


at 

cells  are  flattened  into 
lamellae,  forming  the 
outer  surface  of  the  epi- 
dermis, e. 


THE  INTEG  UMENTA  R  Y  APPEND  A  GES.  797 

at  a  higli  temperature,  as  during  active  exertion ;  at  other  times  the  perspira- 
tion is  insensible.  In  this  respect,  the  skin  has  intimate  sympathetic  relations 
with  other  organs  which  have  somewhat  analogous  functions,  such  as  the 
lungs,  kidneys,  intestines,  etc,  and  when  its  function  is  disordered  or 
checked,  it  induces  alterations  in  the  secretions  of  one  or  all  of  these  organs. 
The  skin  is  also  the  seat  of  a  constant  and  important  respiratory  action,  as 
it  absorbs  oxygen  and  throws  off  carbonic  acid,  and  any  interruption  to  this 
process  is  injurious.) 

AiiTiCLE  II. — Appendages  of  the  Skin. 

The  appendages  of  the  skin  are  hairs  and  horny  productions,  dependents 
of  the  epidermic  layer. 

HAIRS. 

The  hairs  are  the  filaments  which,  collectively,  form  the  external  covering 
of  the  skins  of  anim-als. 

In  the  Horse,  the  bristly  appendages  known  as  horse-hair  should  be 
distinguished  from  the  hair  proper;  the  latter  are  fine  and  short,  particularly 
in  the  regions  where  the  skin  is  thin,  imbricated  on  each  other,  and  spread 
over  the  entire  surface  of  the  body  in  a  continuous  layer  which  is  designated 
the  coat ;  the  former  are  long  and  flowing,  occujjy  the  summit  of  the  head, 
where  they  constitute  the  forelock,  the  upper  border  of  the  neck,  where  they 
form  the  mane,  and  cover  the  caudal  appendage  with  a  splendid  tuft,  the 
tail.  Some  of  these  also  form  special  organs  on  the  free  margin  of  the 
eyelids,  and  are  termed  eyelashes;  while  others  inserted  about  the  lips  and 
below  the  eyes,  are  named  tentacula.  (The  eyelashes  are  chiefly  implanted 
in  the  upper  lid.  The  hairs  of  the  tail  are  the  longest  and  strongest  in  the 
body.  These  particular  hairs  also  grow  on  the  posterior  aspect  of  the 
limbs,  generally  from  about  the  knees  and  hocks  to  the  Ijoofs ;  at  the 
sesamoid  bones  they  constitute  a  long  tuft,  the  fetlocJc,  which  surrounds 
the  horny  growth  named  the  "  ergot."  These  "  foot-locks  "  are  peculiar  to 
the  Horse,  and  vary  in  length  and  coarseness  with  the  breed  of  the  animal.) 

When  the  hair  is  fine,  long,  and  wavy,  it  forms  wool ;  and  when  straight 
and  rigid,  as  in  the  Pig,  it  is  known  as  bristles. 

In  the  Ass  and  Mule,  the  forelock  and  mane  are  rudimentary  or  absent, 
and  tlie  hair  of  the  tail  is  limited  to  a  small  tuft  at  the  extremity  of  the 
organ  in  the  former  animal,  while  in  the  latter  it  is  much  less  abundant  than 
in  the  Horse. 

In  the  0.i;  these  hairs  are  not  present,  except  at  the  extremity  of  the 
tail,  as  with  the  Ass. 

There  are  scarcely  any  other  animals  which  have  other  Lairs  than  those 
composing  the  coat. 

(The  ordinary  hair  of  the  coat  is  soft  and  elastic,  inclined  in  particular 
directions,  and  varies  in  length  not  only  according  to  the  regions  of  the 
body  on  which  it  grows,  but  also  according  to  the  season  or  climate.  In 
the  Horse,  the  direction  of  the  hair  of  the  coat  gives  rise  to  curiously-formed 
waves,  lines,  and  circles,  the  most  constant  of  which  is  on  the  forehead. 

In  the  Coic,  the  hair  is  frizzly  on  the  forehead ;  on  tlie  posterior  part  of 
the  thighs  it  has  a  particular  direction,  while  on  the  outer  side  it  passes 
downwards,  and  from  the  posterior  part  of  the  mamnife  it  ascends  as  high  as 
the  vulva ;  this  characteristic  disposition  forms  what  the  French  have 
termed  ecussons,  by  which  some  have  pretended  to  recognise  the  lactiferous 
qualities  of  the  animal. 


798  THE  APPARATUS  OF  TEE  SENSES. 

In  the  Sheep,  real  hair,  not  wool,  is  found  on  the  lower  part  of  the  face, 
and  the  extremities  of  the  limbs. 

In  the  Goat,  the  hairs  of  the  beard  are  very  long,  and  compose  a  dis- 
tinctive tuft ;  this  animal  has  also  a  fine  crisp  duvet  or  down  beneath  the 
ordinary  hair. 

In  the  Pig,  the  bristles  are  very  strong  in  the  region  of  the  back :  in  old 
animals  they  are  usually  bi-  or  trifurcated  at  their  free  extremity ;  there 
also  exists  a  fine  soft  hair  on  this  animal.     It  has  no  tentacular  hairs. 

In  the  Dog,  the  length,  fineness,  and  consistency  of  the  hair  depends  on 
the  breed. 

In  the  Cat,  the  hair,  in  some  breeds,  as  in  the  Angora,  is  remarkable  for 
its  length  and  softness.  This  creature  has  the  tentacula  enormously 
developed  as  a  moustache. 

In  none  of  these  animals  is  there  a  "  foot-lock.") 

Structure. — The  hairs  are  implanted  in  the  texture  of  the  derma,  and 
sometimes  even  in  the  subjacent  tissues,  their  base  being  enclosed  in  a 
follicle,  at  the  bottom  of  which  their  elements  are  developed.  It  is  therefore 
necessary  to  study :  1,  The  structure  of  the  hair ;  2,  That  of  the  hair- 
follicle. 

1.  The  hair  presents  a  free  portion,  the  shaft,  and  another  concealed  in 
the  follicle,  the  root ;  the  latter  widens  at  its  base — the  bulb  of  the  hair — to 
embrace  the  -papilla  or  hair-germ. 

Three  superposed  layers  compose  a  hair.  The  epidermis  is  a  thin 
lamella  of  horny  flattened  cells,  imbricated  like  tiles  on  a  roof.  Its  elements 
are  marked  on  the  surface  of  the  hair  by  shaded  lines  anastomosing  to  form 
a  network  ;  they  enlarge,  and  become  more  apparent  under  the  influence  of  an 
alkali.  The  epidermis  belongs  to  the  shaft  and  a  portion  of  the  root ;  near  the 
bulb  it  is  replaced  by  soft  nucleated  cells,  which  are  implanted  vertically. 

The  cortfbal  substance  forms  the  largest  part  of  the  thickness  of  the  hair. 
It  is  striped  longitudinally,  and  provided  with  pigment  granules,  whose 
number  varies  with  the  colour  of  the  coat.  In  white  hairs  these  granulations 
are  absent,  but  there  are  found  in  them,  as  well  as  in  coloured  hairs,  small 
spaces  containing  air,  and  which  exhibit  a  dark  colour  under  the  microscope. 
Treated  by  potass  or  sulphuric  acid,  the  cortical  substance  is  reduced  to 
elongated  spindles,  which  again  may  be  decomposed  into  epithelial  lamellae — 
narrow,  and  with  nuclei.  On  arriving  at  the  root,  the  cells  change  their 
character,  becoming  polyhedric,  filled  with  fluid,  and  exhibiting  a  perfectly 
distinct  nucleus  and  more  or  less  pigment.  The  medullary  substance  occupies 
a  narrow  irregular  cavity  in  the  centre  of  the  hair,  extending  from  the  bulb 
or  termination  of  the  root,  to  the  point.  It  has  for  its  base  rectangular, 
rarely  circular,  cells,  which,  according  to  Kolliker,  contain  fat  granulations 
and  air  globules. 

2.  The  hair-follicle  is  a  narrow  cavity,  slightly  contracted  at  its  orifice 
and  dilated  at  the  bottom,  where  the  hair  papilla  is  placed.  It  is  a  simple 
involution  of  the  skin,  as  its  structure  demonstrates.  It  presents,  externally, 
a  loose  conjunctival  layer,  analogous  to  the  reticular  layer  of  the  derma ; 
next,  an  internal  dermic  layer,  dense  and  close  like  the  papillary  layer  of 
the  skin  ;  an  amorphous  limiting  membrane ;  an  epidermic  zone,  the  external 
sheath  of  the  hair,  formed  by  cells,  similar  to  those  of  the  rete  mucosum  ;  and 
a  second  epidermic  zone,  the  internal  sheath  of  the  hair,  which  repeats  the 
horny  layer  of  the  epidermis,  and  is  confounded  with  the  termination  of  the 
epidermis  of  the  hair  towards  the  lower  third  of  the  follicle. 

The  papilla   or  Imir-germ,  is   a   small,  conical,  vascular,  and  nervous 


THE  INTEGUMENTARY  APPENDAGES.  799 

prolongation  rising  up  into  the  hair-bulb.  It  furnishes  the  hair  with 
nutrition  and  the  elements  of  growth.  The  walls  of  the  follicles  of  the 
large  hairs,  or  tentacula,  which  garnish  the  lips  of  the  Horse,  or  bristle  from 
those  of  the  Cat,  are  provided  with  nervous  ramifications  which  endow  these 
appendages  with  a  high  degree  of  sensibility,  and  enable  them  to  play  an 
important  part  in  the  exercise  of  touch. 

Two  sebaceous  glands,  and  a  smooth  muscular  fasciculus,  are  annexed  to  the 
pilous  follicle.  The  sebaceous  glands,  which  have  been  already  described, 
open  into  the  sheath  of  the  hair  by  a  small  excretory  canal,  which  traverses 
the  fibrinous  walls  of  the  follicle.  The  muscular  fasciculus  is  situated  on 
the  side  to  which  the  hair  and  its  follicle  are  inclined  ;  it  arises  from  the 
superficial  face  of  the  derma,  and  terminates  at  the  bottom  of  the  follicle, 
which  it  erects  by  contracting.  When  the  fasciculi  contract  over  a  wide 
surface,  the  extent  of  the  skin  is  diminished,  and  the  hairs  are  erected  and 
partially  ejected  from  their  follicles  (producing  the  cutis  anserina). 

(The  formation  of  a  hair  is  identical  with  the  formation  of  the  epidermis 
by  the  papillary  layer  of  the  derma.  ,Tlie  capillary  plexus  of  the  follicle 
throws  out  plastic  lymph  which  is  converted  into  granules,  then  into  cells 
which  become  elongated  into  fibres.  The  cells  that  are  to  form  the  surface 
of  the  hair,  are  converted  into  flat  scales  that  inclose  the  fibrous  structure  of 
the  interior.  As  these  are  successively  produced,  they  overlap  those  pre- 
viously formed,  and  give  rise  to  the  waving  lines  seen  on  the  circumference 
of  the  hair ;  this  overlapping  also  causes  the  roughness  experienced  in 
drawing  a  hair  between  the  fingers  from  its  point  to  the  bulb.  The  latter 
is  the  newly-formed  part  of  the  hair,  its  expanded  form  being  due  to  the 
greater  bulk  of  the  fresh-cells. 

The  colour  of  the  hair  is  very  varied  in  animals,  ranging  from  black  to 
white,  red  and  brown,  with  all  the  intervening  shades.  The  tint  also 
changes  at  different  periods  of  life,  being  sometimes  altogether  altered 
between  the  juvenile  and  adult  periods ;  dark-coloured  Horses  becoming 
light-coloured  as  age  advances.  Besides,  it  is  never  uniform  in  the  same 
animal  ;  black  Horses  not  unfrequently  having  white  patches  and  diverse  tints, 
with  other  dissimilarities.  The  disease  termed  "  melanosis  "  is  very  common 
in  old  white  Horses  which  were  previously  grey,  and  is  supposed  to  be  due 
to  the  localization  of  the  black  pigment  at  certain  limited  points.  The  hair 
grows  according  to  the  climate,  seasons,  food,  etc.,  and  varies  with  the  species 
and  breed.  The  coat  in  every  animal  is  shed  at  certain  times,  and  is  replaced 
by  new  hairs. 

The  hair  preserves  the  skin  from  unhealthy  external  influences — wet 
and  cold  for  example.  It  is  a  bad  conductor  of  heat,  and  therefore  keeps 
the  body  warm.  The  tentacula  are  very  useful  as  tactile  organs :  while  the 
mane,  forelock,  and  tail  keep  away  insects,  and  the  long  hairs  of  the  fetlock 
and  pastern  protect  these  parts  from  the  injurious  efiects  of  cold  and  wet, 
and  the  action  of  foreign  bodies.) 

HORNY   PRODUCTIONS. 

(Preparation. — The  hoof  and  its  contents  may  be  examined  by  sections  made  in  different 
directions.  The  hoof  can  be  removed  by  prolonged  maceration,  or  by  roasting  on  a  fire, 
■when  it  may  be  cut  and  torn  off  by  means  of  the  farrier's  knife  and  pincers.) 

The  horny  tissues  form  several  groups  the  first  comprises  the  Jiorns  of 
Ruminants ;  the  second,  the  so-called  chesnids  of  Solipeds ;  the  third,  the 
protective  layer  enveloping  the  digital  extremities,  and  constituting  the  claws 
of  Carnivora,  the  Pig,  Ox,  Sheep,  and  Goat,  and  the  hoofs  of  the  Horse,  Ass, 


800 


TEE  APPARATUS  OF  THE  SENSES. 


Fig.  370. 


and  Mule.  These  latter  productions,  ranking  as  they  do  among  the  most 
important  organs  of  the  locomotory  apparatus  of  Solipeds,  will  first  receive 
notice. 

1.  The  Hoof  of  Solipeds, 

The  hoof  of  Solipeds  is  an  extremely  important  study,  because  of  the 
numerous  diseases  which  aifect  this  region.  Consequently,  it  has  been  the 
subject  of  several  voluminous  works,  to  which  the  student  must  be  referred 
for  a  more  complete  description  of  its  organisation  ;^  as  we  cannot  do  more 
here  than  give  some  essentially  descriptive  details,  necessary  to  fill  up  the 
outline  that  we  have  traced  out. 

We  will  at  first  glance  at  the  parts  contained  in  the  hoof,  returning 
afterwards  to  a  description  of  the  horny  case  itself. 

a.  The  Parts  Contained  in  the 
Hoof 

Proceeding  from  within  to 
without,  we  find,  in  the  interior 
of  the  horny  box :  1,  The 
third  phalanx,  navicular  bone, 
and  lower  part  of  the  second 
phalanx,  forming  the  articula- 
tion of  the  foot  ;  2,  The  four 
ligaments  that  bind  this  articu- 
lation; 3,  The  tendon  of  the 
common  extensor  of  the  pha- 
langes which  covers  the  articu- 
lation in  front,  and  that  of  the 
perforans  which  supports  it 
behind,  in  becoming  inserted 
into  the  pedal  bone,  after  gliding 
over  the  posterior  surface  of 
the  navicular  bone ;  4,  The 
complementary  apparatus  of  the 
third  phalanx ;  5,  The  matrix 
of  'the  hoof,  or  keratogenous 
LONGITUDINAL  MEDIAN  SECTION  OF  THE  FOOT.  ^^embrane-a  continuation  of 
1,  Anterior  extensor  of  the  phalanges,  or  extensor    ^j^g   derma  covering  the   digital 


pedis ;  2,  Lateral  extensor,  or  extensor  sufFraginis ; 

3,  Capsule  of  metacarpo-phalangeal   articulation;    ,    -    , ,    ,  j,  ,    -     -, 

4,  Large  metacarpal  bone ;  5,  Superficial  flexor  of  be  added  the  vessels  and  nerveS. 
the  phalanges,  or  perforatus ;  6,  Deep  flexor,  or  The  description  of  the  boncs 
perforans;  >,  Sheath;  8,  Bursa;  9.  Sesamoid  ]jj^g  been  given  at  pages  84,  85, 
bone;  10,  Ergot  and  fatty  cushion  of  fetlock;  11,  ^^^  . 
Crucial  ligament;  12,  Short  sesamoid  ligament; 
13,  First  phalanx ;  14,  Bursa ;  15,  Second  pha- 
lanx ;  IG.  Navicular  bone ;  17,  Plantar  cushion ; 
18,  Third  phalanx  ;  19,  Plantar  surface  of  hoof; 
20,  Sensitive  or  keratogenous  membrane  of  third 
phalanx. 


region.     To    these    parts   must 


Of  the  articulation  and  its 
ligaments,  at  pages  157,  158  ; 

Of  the  tendon  of  the  an- 
terior extensor  of  the  phalanges, 
at  page  263  ; 


Of  the  perforans  tendon,  at  page  286  ; 
Of  the  arteries,  at  pages  553,  554.  555; 

'  See  particularly,  among  the  most  recent  and  complete  French  works,  the  'Traite'de 
rOrganisation  du  Pied  du  Cheval.'  bv  M.  H.  Bouley.  (See  also  tlie  still  more  recent 
work  by  Leisering,  '  Der  Fiitz  des  Pferdes.'  Dresden,  1870.  Also  a  long  series  of  papers 
by  me  on  this  subject  in  the  'Veterinarian'  for  1871-2.) 


THE  INTEGUMENTARY  APPENDAGES. 


801 


Ficr.  371. 


Of  the  veins,  at  pages  612  to  616  ; 

Of  the  nerves,  at  pages  762,  763. 

It  remains  to  notice  the  complementary  apparatus  of  the  third  phalanx, 
and  the  heratogenous  memhrane. 

A.  Complementary  Apparatus  of  the  Pedal  Bone. — In  the  indication 
we  gave  of  this  apparatus  at  page  85,  we  said  that  it  was  composed  of  two 
Literal  pieces — the  fihro-cartilages,  vimte,di  behind  and  below  hy  the  plantar 
cushion :  a  fibrous,  elastic  mass,  on  which  the  navicular  bone  rests,  through 
the  medium  of  the  perforans  tendon.  We  will  take  this  distinction  as  the 
basis  of  our  study, 

1.  Fibro-cartilages  of  the  Pedal  Bone. — Each  of  these  pieces  re- 
presents a  plate  flattened  on  both  sides,  having  the  form  of  an  oblique-angled 
parallelogram,  and  prolonged  behind  the  third  phalanx.  The  external 
face  is  convex,  and  j^ierced  with  openings  for  the  passage  of  veins ;  it 
slightly  overhangs  that  of  the  pedal  bone.  The  internal  face  is  concave, 
channeled  by  vascular  furrows,  and  covers,  in  front,  the  pedal  articulation, 
and  the  synovial  cul-de-sac  which  projects  between  the  two  lateral  ligaments 
of  that  joint ;  below  and  behind,  it  is  united  to  the  plantar  cushion,  either 
through  continuity  of  tissue,  as  at  the  in- 
ferior border,  or  by  fibrous  bands  passing 
from  one  to  the  other.  The  upper  border, 
sometimes  convex,  sometimes  rectilinear,  is 
thin  and  bevelled  like  a  shell ;  it  is  separated 
from  the  j)osterior  margin  by  an  obtuse 
angle,  in  front  of  which  this  border  is  often 
broken  by  a  deep  notch  that  gives  passage 
to  the  vessels  and  nerves  of  tlie  digital  por- 
tion. The  inferior  border  is  attached,  in 
front,  to  the  basilar  and  retrossal  processes 
behind  the  latter,  it  is  reflected  inwards  to 
become  continuous  with  the  tissue  on  the 
lower  face  of  the  plantar  cushion.  The 
posterior  border  is  oblique  from  before  to 
behind,  and  above  to  below,  and  joins  the 
preceding  two.  The  anterior  border  is 
oblique  in  the  same  direction,  and  is  imited 
so  intimately  with  the  anterior  lateral  liga- 
ment of  the  pedal  articulation,  that  it  cannot 
be  separated  from  it  excejit  by  an  artifice 
of  dissection.  It  sends  to  tliis  ligament,  and 
to  the  tendon  of  the  anterior  extensor  of 
the  phalanges,  a  fibrous  expansion  that  be- 
comes fused  with  that  of  the  opposite  side. 

The    fibro-cartilages    comprise   in   their 
structure  a  mixture  of  fibrous  and  cartilagi- 
nous tissue,  though  the  mixture  of  these  is  far  from  being  perfectly  homo- 
geneous, or  everywhere  in  the  same  proportions. 

The  cartilages  of  the  fore-feet  are  thicker  and  more  extensive  than  those 
of  the  hind  ones, 

(The  lateral  fibro-cartilages  are  peculiar  to  Solipeds.) 

2,  Plantar  Cushion, — The  plantar  cushion  is  a  kind  of  wedge,  situated 
in  the  space  between  the  two  cartilaginous  plates  of  the  third  phalanx,  and 
between  the  perforans  tendon  and  the  lower  part  of  the  horny  box.     Its  shape 


horizontal  section  of  the 

horse's  foot. 
Front,  or  toe  of  the  hoof;  2,  Thick- 
ness of  the  Tv-all ;  3,  Laminse ;  4, 
Insertion  of  the  extensor  pedis ;  5, 
Os  pedis ;  6,  Navicular  bone ;  7, 
Wings  of  the  os  pedis;  8,  Lateral 
cartilage;  9,  Flexor  pedis  tendon; 
10,  Plantar  cushion;  11,  Inflexion 
of  the  wall,  or  "bar;"  12,  Hornv 
fros.  '  . 


802 


TEE  APPARATUS  OF  TEE  SENSES. 


Fisr.  372. 


allows  it  to  be  considered  as  having  an  antero-superior  and  an  infero-posterior 
face,  a  base,  summit,  and  two  lateral  borders. 

The  antero-superior  face  is  moulded  on  the  aponeurotic  expansion  of  the 
perforans  tendon,  and  is  "  covered  by  a  cellulo-fibrous  membrane,  the  proper 
tunic  of  the  plantar  cushion,  which  is  continuous,  on  its  inner  face,  with  the 
fibrous  septa  by  which  this  organ  is  traversed,  and  adheres  by  its  external 
or  anterior  face  to  the  reinforcing  sheath  interposed  between  it  and  the 
perforans  tendon." — Bouletj.  This  expansion  is  prolonged,  above,  to  the 
fetlock,  where  it  is  confounded  with  the  superficial  fascia  of  the  meta- 
carpal region ;  it  is  margined,  laterally,  by  two 
small,  very  strong  ligamentous  bands  which,  at 
their  middle  portion,  cross,  in  a  very  oblique 
manner,  the  fasciculus  formed  by  the  vessels  and 
nerves  of  the  digit.  Each  of  these  bands  is  fixed, 
superiorly,  to  the  base  of  the  rudimentary  digit 
known  as  the  ergot,  and  to  the  knob  of  the  lateral 
metacarpal  bone ;  their  inferior  extremity  is  at- 
tached within  the  retrossal  process. 

The  infero-jMsterior  face  of  the  cushion  is 
covered  by  the  keratogenous  membrane,  and  pre- 
sents at  its  middle  the  pyramidal  body,  a  promi- 
nence exactly  like  that  of  the  frog,  to  which  it 
corresponds.  It  shows,  then,  in  front,  a  single 
conical  prolongation,  and  behind,  two  divergent 
jirominences  separated  by  a  median  excavation. 

The  base  of  the  apparatus  lies  behind,  and  is 
inclined  upwards ;  it  is  divided  by  a  depression 
into  two  lateral  masses — the  bulbs  of  the  plantar 
cushion — on  the  inside  of  which  the  posterior 
prominences  of  the  pyramidal  body  reach,  and 
which  become  confounded,  outwardly,  with  the 
posterior  and  inferior  angle  of  the  cartilaginous 
plates.  This  portion  of  the  cushion  is,  like  the 
1,  Heel ;  2,  Coronary  cushion ;    anterior  face,  covered  by  a  cellulo-fibrous  expan- 

3,  Branch  of  the  phantar  gJon,  which  separates  it  from  the  skin  of  the  pas- 
cushion  ;  4,  Median  hicuna;  ^^^^  ^jj-g  expansion  is  attached,  bv  its  lateral 
5,  Laminic  oi   the   bars;    b  '.         ,       ,i  ,      •       t       -t  j?  j.i  j.-i    - 

Velvety  tissue  of  the  sole,  margins,  to  the  posterior  border  of  the  cartilages, 
and  continued,  superiorly,  on  the  surface  of  the 
anterior  expansion,  with  which  it  soon  unites. 

The  summit  (point  or  apex)  forms  a  sharp  border,  more  or  less  regularly 
convex ;  it  is  fixed  into  the  plantar  face  of  the  pedal  bone,  in  front  of  the 
semilunar  ridge  and  the  insertion  of  the  perforans  tendon,  with  which  the 
plantar  cushion  mixes  its  fibres  at  this  part. 

The  lateral  borders  are  wider  behind  than  before,  in  consequence  of  the 
wedge-like  shape  of  the  whole  organ ;  they  are  continuous  with  the  inner 
face  of  the  lateral  cartilages,  as  already  indicated  in  describing  the  latter. 

The  organisation  of  the  plantar  cushion  differs  much  from  that  of  the 
cartilages.  It  has  for  its  base  a  fibrous  structure,  continuous  with  that  which 
constitutes  the  fundamental  framework  of  these  ;  this  structure  is  very  close 
towards  the  infero-posterior  part  of  the  organ,  and  becomes  gradually  looser 
as  it  leaves  this  region ;  the  meshes  it  contains  are  filled  with  a  yellow  pulp 
composed  of  fine,  elastic,  and  connective  fibres,  in  the  midst  of  which  some 
adipose  cells  are  found.     (I  have  attentively  examined  this  yellow  pulp,  and 


LOWER  FACE  OF  THE  HORSE  S 
FOOT,  THE  HOOF  BEING  RE- 
MOVED. 


TEE  INTEGUMENTARY  APPENDAGES. 


803 


Ficr.  373. 


can  perceive  that  it  is  essentially  constituted  by  adipose  tissue.)     Numerous 
blood-vessels  and  nerves  complete  this  structure. 

B.  The  Keratogenous  Membrane,  or  Subcorneus  Integument. — The 
keratogenous  membrane  envelops  the  extremity  of  the  digit,  by  spreading 
over  the  terminal  expansion  of  the  tendon  of  the  extensor  pedis,  through  the 
medium  of  a  tibi-ous  fascia — a  dependency  of  the  lateral  cartilages  ;  and  also 
over  the  inferior  moiety  of  the  external  face  of  these  cartilages,  the  bulbs  of 
the  plantar  cushion,  pyramidal  body,  anterior  part  of  the  plantar  face  of  the 
third  phalanx,  and  over  the  auterior  surface  of  the  same  bone.  It  covers  all 
these  parts  like  a  sock,  and  the  hoof  incloses  it,  as  a  shoe  does  the  human  foot. 

Tliis  membrane  becomes  continuous  with  the  skin  of  the  digital  region 
at  a  circular  line  that  intersects  the  middle  portion  of  the  second  phalanx, 
and  inclines  obliquely  downward  from  behind  to  before.  Below  this  line, 
in  front  and  laterally,  the  subungular  tissues  form  a  semicylindrical  pro- 
tuberance, covered  with  villi,  and  designated  the  "  bourrelet."  (This 
elastic  prominence  has  received  several  most  inappropriate  names  from 
English  farriers  and  hippotomists,  such  as  "  coronary  ligament,"  "  coronary 
substance,"  "  cutiduris,"  etc.  From  its  function,  structm-e,  situation,  and  its 
analogy  to  the  jjlantar  cushion.  I  have  designated  it  the  "  coronary  cushion.') 

On  the  plantar  cushion  and  the  lower  face  of  the  pedal  bone,  this  mem- 
brane is  also  a  villous  tunic — the  velvety  tissue,  which  is  continuous,  towards 
the  bulbs,  with  the  extremities  of  the  coronary  cushion. 

The  portion  spread  over  the  anterior  face 
of  the  third  plialanx  constitutes  the  laminal 
or  "  leafy  tissue,"  so  called  because  of  the 
laminae  or  parallel  leaves  seen  on  its  sur- 
face. 

The  three  regions  of  the  keratogenous 
apparatus  will  be  successively  studied. 

1.  Coronary  Cushion. — This  part  is  the 
matrix  of  the  wall  of  the  hoof,  and  is  lodged 
in  a  cavity  excavated  at  the  ujjper  border  of 
this  part  of  the  horny  case.  It  forms,  ac- 
cording to  the  expression  employed  by 
M.  Bouley,  a  rounded  prominence,  which 
projects  like  a  cornice  above  the  podo- 
phyllous  tissue. 

Its  inferior  border  is  separated  by  a  white 
zone  from  the  upper  extremity  of  the  laminae, 
which  constitute  this  boimdary. 

The  superior  border  is  limited  by  a 
slightly  projecting  margin  named  the  peri- 
oplic  ring,  because  it  originates  the  horn  of 
the  periople.  Between  this  margin  and  the 
cushion  is  a  sharply  defined  groove. 

The  extremities,  narrower  than  the  middle 
portion,  on  arriving  at  the  bulbs  of  the 
plantar  cushion,  bend  downwards  into  the 
lateral  lacunae  of  the  pyramidal  body,  where 
they  become  confounded  with  the  velvety 
tissue. 

The  surface  of  the  organ  shows  filiform  prolongations,  a  little  constricted 
at  their  base,  and  named  papillae,  villo-papillce,  villi,  and  villous  loops,  whose 


LATERAL  VIEW  OF  THE  HORSE's  FOOT, 
AFTER   REMOVAL    OF    THE    HOOF. 

1,  Perioplic  ring,  divided  by  a  narrow 
groove  from  the  coronary  cushion, 
2,  which  is  continuous  with  the 
plantar  cushion,  4,  and  joins  the 
vascular  lamina;,  3,  through  the 
medium  of  the  white  zone. 


804  THE  APPARATUS  OF  THE  SENSES. 

size  is  greatest  towards  the  lower  part  of  the  cushion  ;  those  of  the  perioi)lic 
ring  are  smallest.  Contained  within  the  minute  apertures  at  the  upj^er  part 
of  the  wall,  these  papillae,  considered  as  a  whole,  and  when  the  hoof  has  been 
removed  by  maceration,  form  a  tuftj  surface  most  perfectly  seen  when  the 
foot  is  immersed  in  water. 

The  structure  of  the  coronary  cushion  resembles  that  of  the  derma,  of 
which  it  is  in  reality  only  a  continuation.  It  comprises  a  fibrous  frame- 
work, remarkable  for  its  thickness  and  its  condensation,  with  a  considerable 
number  of  vessels  and  nerves,  whose  ramifications  may  be  followed  to  the 
extremity  of  the  villi.  It  owes  to  its  great  vascularity  the  bright  red  colour  it 
shows  on  its  surface ;  this  colour  is  sometimes  masked  by  the  black  pigment 
belonging  to  the  mucous  portion  of  the  hoof. 

(I  have  found  a  notable  quantity  of  adipose  tissue  in  the  cushion.) 

2.  Velvety  Tissue. — Much  thinner  than  the  plantar  cushion,  the  vel- 
vety tissue,  the  formative  organ  of  the  sole  and  frog,  extends  over  the  whole 
of  the  plantar  region  of  the  third  phalanx,  as  well  as  the  plantar  cushion, 
whose  bulbs  and  pyramidal  prominence  it  covers  by  adapting  itself  exactly 
to  the  irregularities  of  this  elastic  mass. 

Its  surface,  which  altogether  resembles  the  general  configuration  of  the 
plantar  surface  of  the  hoof,  is  divisible  into  two  regions :  a  central,  corre- 
sponding to  the  pyramidal  body  and  the  fit)g,  and  continuous  on  the  bulbs 
of  the  cushion  with  the  extremities  of  the  coronary  cushion  and  the  periojilic 
ring,  but  chiefly  with  the  latter ;  the  other,  peripheral,  is  covered  by  the 
horny  sole,  separated  from  the  podophyllous  tissue  by  the  plantar  border  of 
the  foot,  somewhat  encroached  upon  posteriorly  by  the  laminte  corresponding 
to  the  bars,  and  is  continuous,  above  these  laminse,  with  the  plantar  cushion. 

The  surface  of  the  velvety  tissue  is  studded  with  villi  similar  to  those 
of  the  coronary  cushion,  and  about  the  same  in  size.  The  longest  are 
towards  the  circumference  of  this  surface,  and  the  shortest  in  the  median 
lacuna  of  the  pyramidal  body ;  all  are  lodged  in  the  porosities  on  the  inner 
surface  of  the  horny  sole  and  frog. 

This  tissue  shows  the  same  organisation  as  the  coronary  cushion.  The 
vascular  cerium,  forming  its  base,  is  thickened  at  its  peripheral  portion  by 
a  fibrous  network  named  the  plantar  reticulum,  in  the  meshes  of  which  are 
sustained  the  veins  of  the  inferior  face  of  the  foot. 

3.  Laminal  Tissue. — This  part  of  the  keratogenous  membrane  is  also 
very  frequently  designated  the  podophyllous  tissue  (and  still  more  frequently, 
in  this  country,  as  merely  the  lamince).  It  is  spread  over  the  anterior  face 
of  the  third  phalanx,  occupying  the  interval  between  the  plantar  border  of 
that  bone  and  the  lower  margin  of  the  coronary  cushion  ;  its  width  is, 
therefore,  greater  at  the  anterior  part  of  the  plialanx  tlian  on  its  sides,  where 
the  extremities  of  the  membrane  are  reflected  below  the  bulbs  of  the  plantar 
cushion  on  to  the  velvety  tissue. 

This  membrane  owes  its  name  to  the  leaves  it  exhibits  on  its  superficies  ; 
these  are  from  five  to  six  hundred  in  number,  run  parallel  to  each  other, 
and  are  separated  by  deep  channels,  into  which  are  dovetailed  analogous 
leaves  on  the  inner  side  of  the  wall  of  the  hoof ;  they  extend  from  the  white 
zone  that  limits  the  inferior  border  of  the  coronary  cushion — where  they  are 
not  so  salient— to  the  plantar  border  of  the  foot,  where  they  each  terminate  in 
five  or  six  very  large  villous  prolongations,  which  are  lodged  in  the  horny 
tubes  at  the  circumference  of  the  sole. 

The  leaves  (lamince)  of  the  podophyllous  tissue  increase  in  width  from 
above  to  below;  their  free  margin  is  finely  denticulated,  and,  under  the 


THE  INTEGUMENTARY  ATTENDAGES.  805 

influence  of  any  inflammatory  cause  (laminitis,  ablation  of  the  wall),  these 
denticulje  become  largely  developed,  and  transformed  into  veritable  papillae. 
Their  sides  are  traversed  by  folds,  about  sixty  in  number,  which  pass 
uniuteruptedly  from  top  to  bottom.  These  secondary  leaves,  or  lamellfe, 
are  fixed  obliquely  on  the  sides  of  the  laminae,  as  the  barbules  of  a  feather 
are  attached  to  the  barbs. 

The  podophyllous  tissue  is  not  in  immediate  contact  with  that  of  the 
keraphyllous  tissue,  or  horny  laminae ;  between  the  two  there  is  a  mass  of 
soft,  elliptical  cells,  always  destitute  of  pigment,  easily  stained  with  carmine, 
and  appearing  to  stud  the  ramifications  of  the  vascular  laminae.  A  trans- 
verse section  of  the  union  of  the  hoof  with  these  lamiufe,  when  treated  with 
carmine,  presents  a  very  fine  aspect,  appearing  as  so  many  fern  or  acacia-of- 
Judea  leaves  placed  between  the  keraphyllous  laminae  :  the  principal  nerve, 
and  the  secondary  nervules  of  the  leaves,  being  represented  by  the  lamina 
and  its  lateral  ridges,  the  limb  of  the  leaves  by  the  young  cells  sj)read 
ai'ound  the  latter. 

The  structure  of  the  podoj)hyllous  membrane  resembles  that  of  the  other 
jmrts  of  the  keratogenous  a^jparatus.  Its  corium  is,  like  that  of  the  peri- 
pheral portion  of  the  velvety  tissue,  separated  from  the  os  pedis  by  a  fibrous 
reticulum,  which  supports  the  veins,  and  forms,  to  some  extent,  the  periosteum 
of  the  third  phalanx. 

The  leaves  of  the  podophyllous  membrane  are  immense  lamellar  papillae, 
which  should  be  included  among  the  principal  instnmients  concerned  in  the 
tactile  sensibility  of  the  Horse's  foot,  and  which  play  a  really  mechanical 
part,  in  concurring,  by  their  dovetailing  with  the  keraj)hyllous  (or  horny) 
laminae,  to  assure  the  solidity  of  the  union  of  the  hoof  with  the  living  parts. 
The  cells  which  multiply  on  their  surface  have  usually  but  little  share  in 
the  formation  of  the  horn.     This  will,  however,  be  alluded  to  hereafter. 


6.  Description  of  the  Hoof. 

,  The  hoof  of  the  Horse,  considered  as  a  whole,  represents  a  kind  of  box 
that  envelops  the  inferior  extremity  of  the  digit,  by  fitting  closely  on  the 
keratogenoiTS  membrane,  to  which  it  is  united  in  the  most  intimate  manner 
by  a  reciprocal  penetration  of  the  prolongations  into  the  cavities  that  exist 
on  the  surfaces  in  contact. 

Its  general  shape  is,  as  was  demonstrated  by  Bracy  Clark,  that  of  the 
moiety  of  a  cylinder  cut  obliquely  across  its  middle,  and  resting  on  the 
surface  of  this  section.     In  nearly  all  feet,  however,  it  is  slightly  conical. 

Prolonged  maceration  separates  it  into  three  portions  :  the  ivall,  sole, 
and  frog. 

Wall. — The  wall,  also  named  the  crust,  is  that  part  of  the  hoof  which  is 
apparent  when  the  foot  rests  on  the  ground.  This  thick  plate  of  horn 
covers  the  anterior  face  of  the  foot,  and,  gradually  narrowing  in  width  and 
diminishing  in  thickness,  passes  round  each  side  until  it  reaches  the  bulbs 
of  the  plantar  cushion,  when  its  extremities  are  sharply  inflected  inwards, 
between  the  frog  and  internal  border  of  the  sole,  becoming  confounded  with 
the  latter  about  its  middle  or  anterior  third,  after  being  greatly  reduced  in 
breadth  and  substance. 

The  middle,  or  anterior  part,  of  this  horny  envelope  is  pojiularly  known 
as  the  toe,  the  two  sides  of  which  are  designated  as  outside  and  inside  toe ; 
the  lateral  regions  constitute  the  quarters  ;  the  heels  are  formed  by  the  angles 
54 


806 


THE  APPARATUS  OF  THE  SEXSES. 


Fi2.  374. 


of  inflexion  of  its  extremities ;  while  these  extremities  themselves,  passing 
along  the  inner  border  of  the  sole,  are  termed  the  bars. 

Examined  with  regard  to  the  direction 
that  it  affects  in  its  relations  with  the 
ground,  this  envelope  is  seen  to  be  much 
inclined  in  its  middle  region  or  toe,  and 
this  obliquity  gradually  diminishes  until 
the  posterior  part  of  the  quarters  is  reached ; 
at  this  point  the  wall  is  nearly  perpen- 
dicular. 

The  following  are  the  characters  it 
oifers  in  the  conformation  of  its  faces,  bor- 
ders, and  extremities : 

The  external  face,  convex  from  side  to 

"""''  TZJ^llTviir'  ^'^       «^^^«'  ^^^  perfectly  straight  from  the  upper 

,     '  ,.      .    ,        ^„,,.„    to  the  lower  border,  is  smooth,   polished, 

a,  Inner  surfoce  ot  penople,  or  coronary  ^      ,.    .  '  .^'    -^  ^      ' 

frog-band,  with  some  hairs  passing  and  shming  :   an  appearance  it  owes  to  a 

through ;  a',  Outer  surface  of  same  thin  horny  layer,  independent  of  the  wall 

at  posterior  part  of  foot ;  a",  A  sec-  proper,  designated  the  periople. 
tion  through  the  wall  to  show  its  rpj^-g  „^,./ou/e  forms,  on  the  upper  part 

thickness;    b  to  c,  Quarter   of   the  |,       f  ■     i     j?    •  ,-    ^-^       ^  •,, 

hoof,  from  b  to  the  front  is  the  out-  of  the  wall,  a  kind  of  ring,  continuous  with 

side  (or  inside)  toe ;  from  c  to  d  the  the  bulbs  of  the  plantar  cushion,  and  with 

outside  (or  inside  heel)  •,  e,  Frog ;  /,  the  frog,  of  which  it  is  only  a  dependency  ; 

Bevel  on  upper  margin  of  wall  for  responding,  by   its  Upper   margin,  to   the 
reception    of  coronary    cushion:    g,  K      ^.     ^.  i  •   i  .        •?       .  -i 

leLepuuu  \     .         '   •^'  perioplic  ring,  "'bJdi  secretes  it ;    towards 

Keraphylla,  or  horny  laminae.  t-         i  &'  n    -4.    •  i      n 

the  lower  part  <h  tiie  wall  it  is  gradually 

lost,  friction  incessantly  thinning  and  destroying  it. 

The  inner  face  presents,  over  its  entire 
extent,  the  white  parallel  leaves  which 
dovetail  with  the  laminae  of  the  podo- 
phyllnus  tissue.  Collectively,  these  are 
named  the  hemphyllous  tissue. 

The  superior  border  is  bevelled-oflf, 
on  its  inner  aspect,  into  a  circular  con- 
cavity, into  which  the  plantar  cushion  is 
received.  This  excavation  is  named  the 
cutigeral  cavity,  because  of  its  relations ; 
it  offers  on  its  surface  a  multitude  of 
minute  openings — the  commencement  of 

HOOF,  -WITH  OUTER  PORTION  OF  THE  WALL   ^hc  homy  canalicuU  which  receive  the 

REMOVED   TO    SHOW    ITS    INTERIOR  yillositicS  of  tho  CUtiduHs. 

a,  a,  Penople,   or  coronary  trog-band ;  0,  mi       •    /•     •       7       ?        •  x     1.       'it. 

Cavity  in  Jpperpart  of  wall  for  coro-  The  inferior  border,  in  contact  with 

nary  cushion  ;  c,  Upper,  or  inner,  surfoce  the   ground,    and    subjected    to   wear    m 

of  "bar;"  c?.  Vertical  section  of  wall ;  d',  unshod  animals,  is  united  inwardly,  and 

The  same  at  the   heel;    e,    Horizontal  -^   ^j^^   ^^^g^  intimate   manner,  with  the 

section  of  ditto;  /',   Horny   laminae   ot  .  „  ^  , ,  , 

bar ;  /",  Ditto  of  wall ;  /'",  literal  aspect  Circumference  of  the  sole 
of  a  lamina;  (J,  Upper,  or  inner  surface  The    extremities,    constituted   by    the 

of  the  horny  sole;   h,  Junction  of  the  reflected  and  re-entering  prolongations 

horny  lamina  with  the  sole  (the  "  white  jj^g^n  as  the  bars,  form,  outwardly,  the 

line");  i  Toe-Stay  at  the  middle  of  the  ^  ^    gj^g   ^f  the    lateral    lacunar    of 

toe;    *,  Upper,  or  inner  surface  of  the  ,,        .  ,,  -it-  ^^ 

horny  frog ;    I,  Frog-stay ;    m.   Cavity  the  frog  :_  they   are  provided,   inwardly, 

corresponding  to  a  branch  of  the  frog ;  with  laminte  like  the  rest  of  the  wall. 

n,  Ditto  corresponding  to  the  body  of  ^]^q  xipper  margin  of  these  prolonga- 

the  frog. 


Fig.  375. 


THE  INTEGUMENTARY  APPENDAGES. 


807 


tious  is  confounded  with  the  frog  and  sole ;  the  lower  appears  between  these 
two  parts,  and  is  effaced  at  a  certain  distance  from  the  point  of  the  frog. 

Sole. — The  sole  is  a  thick  horuy  plate  comprised  between  the  inner  bor- 
der of  the  wall  and  its  reflected  prolongations  ;  thus  occupying  the  inferior 
face  of  the  hoof.     It  offers  two  faces  and  two  borders  or  circumferences. 

The  inferior,  or  external  face,  forms  a  more  or  less  concave  surface 
according  to  circumstances.  The  superior,  or  internal  face,  corresponds  to 
the  peripheral  portion  of  the  velvety  tissue ;  it  shows  a  multitude  of  little 
.pertures  analogous  to  those  of  the  cutigeral  cavity,  into  which  are  inserted 
the  papilla)  of  the  keratogenous  membrane. 

The  external  border,  or  large  circumference,  is  united,  throughout  its 
extent,  to  the  inner  contour  of  the  lower  border 
of  the  wall,  by  means  of  its  denticulfe,  which 
are  reciprocally  dovetailed  into  those  on  the 
inner  face  of  the  wall  near  its  inferior  border. 
The  internal  harder,  or  small  circumference,  is  a 
deej),  V-shaped  notch,  widest  behind,  which  cor- 
responds to  the  bars,  and  at  the  bottom  of  which 
the  point  of  the  frog  is  fixed, 

Fkog. — This  is  a  mass  of  horn,  pyramidal  in 
shape,  and  lodged  between  the  two  re-entering 
portions  of  the  wall.  It  offers  four  planes  (or 
sides),  a  hase,  and  a  summit  (or  point). 

The  inferior  and  the  two  lateral  "planes  con- 
stitute the  external  surface  of  the  organ.  The 
first  is  hollowed  by  a  longitudinal  excavation, 
which  is  shallow  in  well-formed  hoofs,  and  is 
named  the  median  lacuna  of  the  frog,  separating 
the  two  salient  portions,  or  branches,  which  di- 
verge posteriorly  and  join  the  heels.  T lie  other 
two  planes  are  directed  obliquely  downwards  and 
inwards;  they  adhere  closely,  at  their  upper  third, 
to  the  external  side  of  the  bars,  and  anteriorly 
to  the  inner  border  of  the  sole.  "  This  union 
is  so  close  that  no  line  of  demarcation  is  ajipa- 
rent  between  these  parts,  and  their  separation 
can  only  be  obtained  by  j^rolonged  maceration. 
The  non-adherent,  or  free  portion,  forms  the  inner 
side  of  the  angular  cavities  known  as  the  lateral 
lacunce,  or  commissures  of  the  frog,  whose  external 
side  is  constituted  by  the  inferior  face  of  the  bars." — Bouley. 

The  superior  plane,  forming  the  internal  face  of  the  frog,  is  cribbled 
with  holes  like  that  of  the  sole,  and  is  exactly  moulded  on  the  pyramidal 
body  of  the  plantar  cushion.  It  also  offers  a  triangular  excavation,  divided 
posteriorly  into  two  latter  channels  by  a  prominence  directed  from  before 
backwards,  to  which  Bracy  Clark  gave  the  name  of  frog-stay,  but  which 
M.  Bouley  prefers  to  designate  the  spine  or  ridge  (ar^te)  of  the  frog. 

The  base  or  posterior  extremity  of  the  frog,  constituted  by  the  extremities 
of  its  branches,  forms  two  rounded,  flexible,  and  elastic  eminences  separated 
from  each  other  by  the  median  lacuna ;  they  cover  the  angles  of  inflexion  of 
the  wall,  and  are  continuous  at  this  point  with  the  perioplic  band.  Bracy 
Clark  named  them  the  glomes  of  the  frog. 

With  regard  to  the  summit,  or  anterior  extremity  of  the  organ,  it  is  a 


PLANTAR  OK  GROUND  SURFACE 
OF    A    HOOF  ;    RIGHT    FOOT. 

The  intei'val  from  a  to  a  repre- 
sents the  toe  ;  Fi'om  a  to  b,  b, 
outside   and   inside    quarters ; 

c,  o,  Commencement  of  bars ; 

d,  d,  Inflexions  of  wall  at  the 
heels,  or  "  buttresses  ;"  e,  La- 
teral lacuna ;  /,  /,  /,  Sole  ;  g, 
White  line ;  g',  </',  Ditto  be- 
tween the  sole  and  bar :  h, 
Body  of  frog ;  i,  Branch  of 
frog  ;  k,  k,  Glomes,  or  heels  of 
frog ;  /,  Median  lacuna. 


808  THE  APPARATUS  OF  THE  SENSES. 

point  wedged  in  tlie  re-entering  angle  comprised  between  the  two  portions 
of  the  inner  border  of  the  sole. 

In  the  Ass  and  Mule,  the  hoof  is  always  narrower,  laterally,  than  that  of 
the  horse ;  the  wall  is  always  higher  and  thicker,  the  sole  more  concave, 
the  frog  smaller  and  deeper  seated  at  the  bottom  of  the  excavation  formed 
by  the  sole,  and  the  horn  is  much  more  hard  and  resisting. 

(The  angle  of  the  wall  of  the  hoof  in  front  varies  from  50°  to  56% 
though  usually  erroneously  stated  to  be  45°.  The  inner  face  of  the  wall, 
at  the  middle  of  the  toe,  and  in  a  line  with  the  frog-stay,  frequently  shows  a 
more  or  less  salient  and  conical  prominence — base  towards  the  lower  margin 
of  the  wall — which  corresponds  to  a  vertical  depression  in  the  os  pedis. 
Vallada  imagined  that  this  projection  served  to  unite  the  wall  and  sole  more 
closely,  but  it  is  far  more  probable  that  its  function  is  the  same  as  that  of 
the  frog-stay — -to  maintain  the  position  of  the  os  pedis,  and  prevent  its 
rotation  within  the  hoof.     I  have,  therefore,  named  it  the  "  toe-stay.") 

Strtjctuee  of  the  Hoof-hoen.— The  structure  of  the  horn  has  been  the 
object  of  a  great  number  of  researches ;  Gurlt,  Delafond,  Bouley,  Gourdon, 
and  Ercolaui '  have  given  descriptions  of  it,  and  we  have  also  some  details  to 
add  to  the  labours  of  these  authorities. 

The  horny  substance  constituting  the  hoof  of  Solipeds,  has  a  fibrous 
appearance ;  this  is  most  conspicuous  in  the  wall,  less  apparent  in  the  frog 
and  deeper  portions  of  the  sole,  but  impossible  to  distinguish  in  the 
superficial  layer  of  the  latter,  where  the  disintegration  continually  taking 
place  separates  the  horn  in  scaly  fragments  of  varying  thickness  and 
extent.  The  consistence  of  the  horn  is  always  less  in  the  frog  than  in.  the 
sole  and  wall.  Its  tint  is  in  some  hoofs  black,  in  others  white,  and  in 
others  again  a  mixture  of  these  two.  The  inner  face  of  the  wall,  however, 
is  never  black ;  and  when  the  lower  part  of  the  limb  is  partially  or  wholly 
white,  we  may  be  sure  that  all  the  thickness  of  the  wall  will  either  be  white 
at  corresponding  points  in  the  former,  or  entirely  so  in  the  latter. 

Except  in  the  keraphyllous  tissue,  the  minute  structure  of  the  hoof-horn 
always  exhibits  the  same  characters ;  everywhere  it  is  perforated  by  cylin- 
drical canals  whose  upper  end  is  funnel-shaped,  and  these  contain  the  papillae 
of  the  matrix,  whether  they  belong  to  the  coronary  cushion  or  velvety  tissue ; 
while  the  lower  end  reaches  the  inferior  border  of  the  wall,  or  lower  face  of 
the  sole  and  frog,  according  to  their  situation.  It  is  rare  to  find  them  in  the 
horny  laminae.  All  are  rectilinear,  with  the  exception  of  those  of  the  frog, 
which  are  somewhat  flexuous ;  and  all  have  the  same  oblique  direction 
do^Tiward  and  forward,  following  the  inclination  of  the  anterior  portion  of 
the  wall.  They  are,  therefore,  almost  exactly  parallel  to  each  other,  not 
only  in  the  same,  but  in  the  two  different  regions.  Their  diameter  varies 
considerably,  though  the  smallest  are  always  those  of  the  periople ;  in  the 
wall,  they  are  smaller  as  they  approach  the  outer  surface. 

These  tubes  are  not  mere  canals  hollowed  out  of  the  horny  substance  ; 
on  the  contrary,  they  have  very  thick  walls  which  are  formed  of  numerous 
concentric  layers,  one  within  the  other,  and  the  horny  tissue  connecting 
them  has  not  the  same  apparent  stratiform  disposition.  Filled  by  the 
papillBB  of  the  keratogenous  membrane  at  their  superior  extremity,  these 

'  (The  researches  of  Professor  Eawitsch  must  not  be  omitted.  They  will  be  found  in 
Volume  xxviii.  of  the  '  Magazin  fiir  Thierheilkunde,'  and  also  in  a  little  hrochnre 
entitled  '  Ueber  den  feineren  Bau  und  das  Wachsthum  deg  Hufhorns.'  Berlin,  1863. 
Leisering  must  likewise  be  referred  to.  My  own  researches  are  published  in  the 
'  Veterinarian'  for  1871.) 


TEE  INTEGUMENTARY  APPENDAGES. 


809 


Fig.  377. 


canals  are  not  empty  for  the  remainder  of  their  extent ;  but  contain  q. 
particular  white  substance,  which  is  so  opaque  that  it  appears  of  a  fine 
black  hue  when  examined  as  a  transparency  in  the  microscope.  This  matter 
is  not  deposited  in  a  uniform  manner  in  the  canals,  but  irregularly-lookincf, 
like  a  knotted  cord  or  a  necklet  of  beads ;  and,  where  it  does  exist,  it 
does  not  always  exactly  fill  the  calibre  of  the  tube,  an  interval  being 
observed  between  the  inner  face  of  the  latter  and  the  intratubular  deposit. 
Sometimes  it  is  seen  without  the  canals,  among  their  concentric  lamellae, 
and  even  in  the  horny  intertubular  substance. 

If  we  are  desirous  of  completing  our  knowledge  of  the  minute  organ- 
isation of  the  hoof-horn  by  studying  the  anatomical  elements  constituting 
it,  we  will  find  that  it  is  foilaed  of  epithelial  cells  belonging  to  the  kind 
most  wide-spread  in  the  economy — pavement  epithelium.  These  horn 
epifhelial  cells  are  very  thin,  j)ale,  polygonal,  and  generally  oblong,  have 
sharply  defined  borders  and  finely  granular  faces,  sometimes  showing  a 
nucleus  containing  a  single  or  multiple  nucleolus.  The  nuclei  sometimes 
occupy  the  centre,  at  other  times  another  part  of 
the  cells — even  their  margins ;  and  they  also  con- 
tain pigment  granules  more  or  less  coloured  and 
numerous.  Acetic  acid  acts  very  slowly  on  them, 
and  is  limited  to  making  them  more  transparent. 
Potass  and  soda  at  first  softens,  then  distends 
them,  causing  their  granulated  aspect  to  disappear, 
and  roimding  their  contours ;  afterwards,  they  be- 
come quite  diaphanous,  and  finish  by  being  com- 
pletely dissolved. 

Examined  in  their  reciprocal  relations,  these 
epithelial  cells  are  not  seen  to  be  agglomerated 
confusedly  together,  but  are,  on  the  contrary,  dis- 
posed in  a  regular  manner,  forming  a  real  frame- 
work that  wonderfully  concurs  in  assuring  solidity 
and  flexibility.     In  the  walls  of  the  tubes  we  see 

them  arranged  horizontally  around  the  canal,  and  horn-cells^  from  the  sole 
stratified  from  within  to  without,  so  as  to  form 
successive  concentric  layers.  In  the  intertubular 
horn  they  are  disposed  differently,  their  stratifi- 
cation being  no  longer  parallel  to  the  direction  of 
the  tubes,  but  perpendicular  to  it,  and  piled  upon 
each  other  in  the  intervals  separating  the  latter.  This  change  of  direction 
does  not  occur  suddenly;  at  the  limits  of  the  tubes  epithelial  cells  are 
seen  lying  obliquely. 

In  a  transverse  section  of  the  wall,  there  are  observed  around  the  tubes, 
in  the  intertubular  substance,  as  well  as  in  the  horny  laminje,  small 
iiTcgularly  elliptical  spaces  containing  a  solid  denticulated  mass  of  a 
brownish  tint,  which  is  easily  stained  with  carmine.  These  bodies  are 
more  elongated  in  the  intertubular  substance  than  in  the  walls  of  the  tubes, 
and  have  a  certain  resemblance  to  the  cartilaginous  capsules,  but  especially 
to  the  bone  cavities  filled  by  their  contents. 

Independently  of  the  hard,  dry,  and  flattened  cells,  there  is  found  an 
opaque  substance  that  partly  fills  the  tubes,  and  which  is  also  sometimes 
met  with  in  their  walls.  This  material  does  not  differ  from  the  last  in  its 
nature ;  it  is  also  formed,  as  has  been  asserted  by  Gourdon  and  Ercolani,  of 
irregular  granular  cells  which  are  stained  by  the  carminate  of  ammonia. 


OP    THE    HOOF. 

a,  Young  cells  from  the  upper 
surface  of  the  sole ;  b,  Cells 
from  the  lower  sui'face,  or 
dead  horn  of  the  sole. 


810 


THE  APPARATUS  OF  THE  SENSES. 


Fi?.  378. 


CONSTITUENT    ELEMENTS 
OF    THE    WALL. 


Pigmentary -corpuscles  exist  in  tlie  substance  of  the  coloured  liorn, 
and  are  disposed  singly,  or  in  small  masses,  in  the  epithelial  cells  of  the 
intertubular  substance.  The  presence  of  these  corpuscles  has  been  denied, 
and  the  coloration  has  been  attributed  to  a  greater 
condensation,  at  certain  points,  of  the  epithelial 
elements.  Fine  pigment-granules  are  disseminated 
in  the  cells,  but  it  is  evident  that  beyond  these  there 
are  at  different  points  pigment-corpuscles ;  for,  after 
treating  a  section  of  coloured  horn  with  soda,  the 
epithelial  elements  are  distended,  become  pale,  and 
disappear,  leaving,  however,  here  and  there,  masses 
of  black  granulations.  '  These  pigmentary-corpuscles 
are  absent  in  white  horn. 

Development  of  the  Hoof. — The  hoof  being  a 
dependency  of  the  epidermis,  is  developed  like  it : 
that  is,  by  the  incessant  formation   of  cells  in  the 
layer  that  corresponds  to  the  rete  mucosum,  at  the 
expense  of  the  plasma  thrown  out  by  the  numerous 
vessels  in  the  keratogenous  membrane.     The  velvety 
tissue  forms  the  sole  and  frog ;  the  perioplic  ring  the 
periople,   and  the   coronary   cushion   the    wall.     In 
these  different  parts,  the   ej^ithelial  cells   multiply, 
and  become  flattened  in  layers  parallel  to  the  surface 
that  secretes  them,  and  in  proportion  as  they  recede 
a,  Horn-cells;    b,    Horn-   from  that  surface;    so  that  the  wall  grows  from  its 
fibre  from  the  hoof  of  superior  to  its  inferior  border,  and  the  other  two  parts 
a  new-born  foal   show-   ^^  ^^^  ^^^^  ^^.^^  ^j^^j^.  internal  to  their  external  face. 
ing  the  vertical  disposi-  „,         .,1      .,•  ^   .1  i  .  i    ,1 

tion  of  the  cells.  The  villosities  01  the  coronary  cushion  and  the 

velvety  tissue  are  the  organs  ai'ound  which  the  epi- 
thelial lamellae  are  grouped,  and  their  presence  determines  the  tubular 
structure  of  the  horn ;  their  function  is  completed  by  the  exhalation  of  a 
particular  fluid  that  maintains  the  flexibility  of  the  hoof,  and,  probably,  by 
the  development  on  their  sui"face  of  the  irregular  cells  which  cluster  in 
the  interior  of  the  tubes. 

The  leafy  tissue,  in  a  normal  condition,  does  not  concur  to  any  extent 
in  the  develojiment  of  the  wall.  The  cells  covering  it  are  miiltijjlied  in 
describing  a  downward  and  forward  movement ;  and  though  they  are 
certainly  applied  to  the  inner  face  of  the  wall,  yet  they  do  not  constitute 
the  horny  laminae.  The  latter  are  formed  on  the  coronary  cushion,  at  the 
commencement  of  the  vascular  laminae,  and  they  descend  with  the  wall  in 
gliding  along  the  surface  of  the  layer  of  cells  separating  them  from  the 
latter ;  this  downward  movement  is  facilitated  by  the  multiplication,  in  the 
same  sense,  of  these  cells.  This  opinion  as  to  the  function  of  the  vascular 
laminae  is  based  on  comparative  anatomy,  on  the  presence  of  some  lon- 
gitudinal tubes  in  the  homy  laminae,  and  on  pathological  observations. 

When  the  j)odophyllous  tissue  is  inflamed,  whether  or  not  it  is  exposed, 
its  latent  activity  is  quickly  manifested,  and  it  rapidly  throws  out  a  large 
quantity  of  hard  consistent  horn,  traversed  by  tubes  which,  according  to 
M.  Gourdon,  are  directed  obliquely  backwards.  These  tubes  are  more 
ii'regular  than  those  of  the  normal  wall,  are  disposed  in  parallel  series,  and 
are  formed  around  the  villo-papillse  developed  on  the  free  border  of  the 
laminae.  In  this  horn,  produced  by  the  vascular  laminae  only,  there  are 
never  observed  between  these  latter  the  horny  plates  of  cells — sharp  and 


TEE  INTEGUMENTARY  AFFENDAGES. 


811 


distinct  in  the  midst  of  the  other  cells,  as  in  those  of  the  wall  formed  by  the 
coronary  cushion. 

The  horn  thrown  out  on  the  surface  of  the  podophyllae,  immediately 
after  the  removal  of  a  fragment  of  the  wall,  is  not  a  definitive  horn,  but 
must  be  replaced  by  that  from  the  coronet.  This  substitution  is  complete ; 
as  a  microscopal  examination  proves  that  the  wall  which  descends  from  the 

Fig.  379. 


HORIZONTAL   SECTION   OF   THE   JUNCTION   OF   THE   WALL   WITH   THE   SOLE   OF   THE    HOOF. 

a,  Wall,  with  its  horn-tubes ;  6,  b,  Horny  lamina  projecting  from  the  wall ;  c,  c, 
Horn-tubes  formed  by  the  terminal  villi  of  the  vascular  laminae,  the  horn 
surrounding  them  and  occupying  the  spaces  between  the  horny  lamina;,  con- 
stituting the  "  white  line ;"  d,  Horny  sole,  with  its  tubes. 

cushion,  and  is  furnished  with  horny  laminae,  passes  beneath  the  provisional 
wall,  and  glides  downward — by  the  combined  action  already  mentioned— over 
the  surface  of  the  soft  cells  of  the  vascular  laminas.  As  soon  as  the  latter 
are  covered  by  the  proper  wall,  their  marginal  papillfe  become  atrophied, 
and  they  again  assume  the  limited  function  pertaining  to  their  physiological 
condition. 


HORIZONTAL   SECTION   OF   THE   WALL,    AND   HORNY,    AND   VASCULAR   LAIIIN.E,   TO 
SHOW    THE    JUNCTION    OF    THE    LATTER    AND    THE    LAMINELL.E. 

a,  Inner  portion  of  the  wall  with  the  laminse  arising  fi-om  it ;  b,  Vascular  laminae ; 
c,  Horny  lamina  of  average  length ;  c',  c'.  Unusually  short  lamina;  \  c  ,  c  , 
Laminellte  on  the  sides  of  the  horny  laminae ;  d,  Vascular  lamina  passing  between 
two  horny  ditto ;  d',  Vascular  lamina  passing  between  three  horny  laminae ;  d  , 
Lateral  laminellae ;  e,  e,  Arteries  of  vascular  laminae  which  have  been  injected. 

(The   description  of  the    disposition  of  the   epithelial   cells   given  by 
Chauveau  does  not  coincide  with  my  owti  observations.     As  he  correctly 


812  THE  APPARATUS  OF  THE  SENSES. 

states,  these  cells  are  formed  in  planes  parallel  with  the  surface  that 
secretes  them ;  consequently,  around  the  papillae  they  are  more  or  less 
vertical,  while  between  them  they  are  horizontal.  The  walls  of  the  tubes, 
or  fibres,  are  therefore  composed  of  cells  disposed  in  a  vertical  manner; 
while  in  the  interfibrous  horny  matter  they  are  arranged  in  the  oj^posite 
direction.  The  loose  nodulated  contents  of  the  tubes  is  composed  of  cells 
thrown  off  from  the  termination  of  the  papilla,  and  corresponds  to  the  pith 
of  feathers.  The  soft  cells  interposed  between  the  vascular  and  horny 
laminae  are  carried  down  to  the  lower  margin  of  the  wall,  where,  with  the 
elastic  horn  secreted  by  the  papillae  which  terminate  the  former,  they 
constitute  the  peculiar  light-coloured  band,  or  "  white  line,"  which  marks 
the  junction  of  the  sole  with  the  wall  (Fig.  379).  This  intermediate  band 
of  soft  flexible  horn  at  this  point  obviates  tearing  of  the  sole  from  the  wall, 
and  fracture  of  the  former.  The  cells  of  the  horny  laminae  are  more  or  less 
fusiform. 

M.  Chauveau  has  also  evidently  overlooked  the  presence  of  beautiful 
lateral  leaflets  on  the  sides  of  the  horny  laminae,  corresponding  to  those  on 
the  vascular  leaves.  These  were  observed  by  me  in  1858 ;  in  1862  they 
were  described  by  Rawitscli  and  Ercolani,  and,  at  a  later  period,  by  Colin  of 
Alfort  and  Leisering  of  Dresden.  They  are  very  conspicuous  in  a  well- 
prepared  section  (Fig.  380,  d"). 

It  should  be  observed  that  the  growth  of  the  wall  of  the  hoof  is 
indefinite,  but  that  the  sole  and  frog,  after  attaining  a  certain  thickness, 
exfoliate.  For  complete  details  as  to  the  physiology  of  the  Horse's  foot,  the 
student  is  referred  to  the  '  Veterinarian'  for  1871.) 

2.  The  Claws  of  Buminants  and  Pachyderms. 

la  the  Ox,  Sheep,  and  Pig,  the  plantar  cushion  covers  the  bulb  of  the  heel  of  each 
digit,  where  it  forms  a  convex  mass ;  it  extends  to  the  insertion  of  the  deep  flexor 
tendons  of  the  phalanges,  in  becoming  triangular  in  shape,  and  thinner.  The  horny 
envelope  covering  the  extremity  of  the  digits  of  these  animals  is  a  kind  of  cupola, 
having  almost  the  form  of  the  third  phalanx ;  it  is  usually  named  the  claio. 

The  claw  of  the  Ox  has  an  outer  face  resembling  the  wall  of  the  Horse's  hoof,  and  an 
inner  face  which  is  slightly  concave,  and  marked  by  undulating  grooves ;  owing  to  tiiis 
concavity,  the  two  claws  of  each  foot  only  touch  at  the  extremities  of  their  adjacent 
faces.  The  plantar  region  of  tlie  claw  is  slightly  depressed,  and  but  little  developed ; 
it  is  chiefly  made  up  of  the  plantar  cushion,  whicii  is  covered  by  a  thin  layer  of  supple 
tubular  horn.  On  the  inferior  of  Ihe  claw  is  seen  a  wide  shallow  cutigeral  cavity, 
perforated  by  very  fine  openings,  and  laminae  thinner  and  more  numerous  than  in  the 
Horse's  hoof.  The  tubes  of  the  claw-horn  are  very  &maU,  being  surj^assed  in  diameter  by 
those  of  the  periople  and  sole. 

Above  and  behind  each  claw  are  two  little  rudimentary  horny  capsules,  which  are 
named  ergots.  (Each  contains  a  small  bone,  which  is  not  attached  to  tlie  skeleton  in 
Buminants.  In  the  Pig,  tliese  rudimentary  claws  are  larger,  and  are  connected  with  the 
bones  of  the  leg.  In  this  animal  the  horn  of  the  claws  is  altogether  thinner,  softer, 
and  less  resisting  than  in  Solipeds.  The  ergot  is  the  representative  of  those  digits  which 
are  apparently  absent  in  the  solid  and  cloven  foot.) 

8.  TJie  Claws  of  Carnivora. 

In  these  animals,  the  third  phalanx  of  the  digits  is  enveloped  in  a  conical  horny 
sheath  that  curves  downwards  like  the  bone  itself.  This  covering  is  designated  the 
clmo  or  nail,  and  off'ers  somewhat  tlie  same  organisation  as  the  liorns  of  Ruminants  ;  it 
is  developed,  and  grows  in  the  same  manner,  as  the  hoof  of  Solipeds,  its  matrix  being  a 
prolongation  of  the  corium  which  extends  over  the  third  phalanx,  after  dipping  into 
the  circular  farrow  at  the  base  of  that  bone. 

Placed  at  the  extremity  of  the  digital  region,  the  claw  in  these  animals  is  not 
utilised  in  locomotion,  as  the  foot  does  not  rest  on  the  ground  by  the  extremities  of  the 


THE  APPARATUS  OF  TASTE.  813 

digits,  but  by  the  whcle  plantar  surface.  Therefore  it  is,  tliat  we  find  on  tliis  face  a  kind 
of  cj)idermic  pad  covering  live  fibro-adipose  tubercles :  four  small  ones  placed  along  tlie 
four  principal  digits — the  tifth  or  thumb  not  being  sufficiently  developed  to  reach  the 
ground — and  a  large  central  one,  circumscribed  in  front  by  the  others.  This  ar- 
rangement is  destined  to  diffuse  the  pressure  caused  by  the  weight  of  the  body  (and, 
doubtless,  to  ameliorate  the  concussion  arising  from  the  exertions  these  animals  make,  as 
well  as  to  insure  their  footsteps  being  noiseless  in  approaching  their  prey).  In  the  Dog, 
the  claws  may  be  used  for  burrowing  in  the  ground. 

In  the  Cat,  the  claws  are  very  sharp  and  retractile ;  being  capable  of  -erection  and 
depression  in  the  interdigital  spaces,  by  mtans  of  a  small  yellow  elastic  ligament 
passing  from  the  second  to  the  third  phalanx.  This  animal's  claws  constitute  its  most 
powerful  weapon  of  attack  and  defence. 

4.  Uie  Frontal  Horns. 

These  are  conical  homy  sheaths,  more  or  less  large,  crooked,  and  annulated 
transversely,  formed  by  concentric  layers  of  epithelial  cells  and  some  pigment  corpuscles. 
The  horns  grow  like  the  epidermis  and  the  hair,  their  elements  being  secreted  by  that 
portion  of  the  coriiun  spread  over  the  osseous  cores  of  the  frontal  bones,  and  wliich 
completely  envelope  these ;  this  portion  of  the  skin  is  remarkable  for  its  great 
vascularity. 

(The  length,  direction,  and  general  form  of  the  horns  varies  in  TJuminants,  not  only 
with  regard  to  species,  age.  and  race,  bufalso  the  sex.  The  Bull,  in  the  Bovine  species, 
generally  has  short,  thick,  powerful  horns ;  the  Coio  long  and  slender  ones ;  and  the  Ox 
large,  long,  and  strong  ones.  Some  breeds  have  no  horns  at  all ;  the  same  with  the 
Goat  sj^ecies,  though  generally  the  horns  in  these  are  long,  flattened,  and  curved 
backwards  and  downwards.  With  the  Bam,  the  horns  are  sometimes  immense  and  very 
powerful,  being  of  a  spiral  form.  They  are  usually  less,  or  altogether  deficient,  in  the 
Ewe.  In  the  Bovine  species,  the  transverse  rings  on  the  homs  serve  to  indicate  the  age^ 
the  first  appearing  after  two  years.) 

5.  TJie  Chesnuts. 

This  name  is  given  to  a  little  horny  (oval  or  round)  plate  found,  in  the 
Horse,  on  the  inner  face  of  the  fore-arm — in  the  lower  third  of  the  region, 
and  at  the  upper  extremity  of  the  inner  face  of  the  metatarsal  bone.  It  is 
composed  of  a  mass  of  epithelial  cells,  arranged  in  tubes  like  the  horn  of 
the  hoof.  In  Solipeds,  the  chesnut  is  the  representative  of  the  thumb. 
That  on  the  posterior  limbs  is  absent  in  the  Ass;  in  the  Mule  it  is  very 
small.  "^ 

(In  fine-bred  Horses,  this  homy  production  is  much  less  developed 
than  in  the  coarser  breeds.     It  is  always  smaller  in  the  hind  limbs. 

In  the  hind  and  fore-legs,  we  also  find  a  similar,  but  smaller  corneous 
mass,  growing  from  the  skin  of  the  fetlock,  and  named  the  err/ot.  Like  the 
chesnut,  it  bears  the  same  relative  development  in  fine  and  coarse-bred 
horses.) 


CHAPTER  II. 
APPARATUS   OF  TASTE. 

The  sense  of  taste  permits  the  appreciation  of  savours,  or  the  sapid  properties 
of  bodies. 

Two  nerves— the  chorda  tympani  and  the  lingual  branch  of  the  ninth  pair 
—appear  at  present  to  be  the  only  sensory  filaments  endowed  with  the 
exercise  of  this  function.  They  ramify  in  the  lingual  mucous  membrane, 
"which  is  thus  made  the  organ  of  taste. 


814  THE  APPARATUS  OF  THE  SENSES. 

The  tongue  and  its  investing  membrane  having  been  described  at  page 
335,  their  anatomy  need  not  again  be  referred  to ;  but  we  must  ghxnce  at 
the  organisation  of  the  latter  in  considering  it  as  the  special  apparatus  of 
gustation.  This  will  necessitate  a  few  words  on  the  free  surface  of  the  mem- 
hrane  which  comes  into  contact  with  the  sapid  bodies,  and  some  consider- 
ations ou  the  terminations  of  the  nerves  which  transmit  the  impressions 
produced  by  these  bodies  to  the  brain. 

Free  Surface  op  the  Lingual  Mucous  Membrane. — This  surface  is 
studded  by  a  multitude  of  papillary  prolongations,  which  are  nearly  all 
limited  to  the  upper  surface  of  tlie  tongue,  to  which  they  give  a  tufty 
appearance.  Their  form  and  volume,  as  mentioned  at  page  336,  are  very 
variable,  according  to  their  situation :  some  are  microscojDic,  while  others 
form  voluminous  caruncles ;  others,  again,  are  long,  conical,  and  iiliform ; 
another  variety  is  round  or  depressed,  representing  a  hemispherical  tubercle 
scarcely  projected  beyond  the  general  surface,  or  placed  at  the  bottom  of  an 
excavation  in  the  mucous  membrane.  The  latter  constitute  the  cahjciform 
pajiillce  (p.  circumvallaice,  p.  lenticulares),  and  are  considered  the  true  organs 
of  gustation  ;  the  others  are  the  fungiform  (p,  capitatce)  and  filiform  papillce, 
which  play  a  mechanical  jiart  on  the  surface  of  the  tongue. 

The  cahjciform  papiU(x,  in  the  Horse  are  two  in  number,  and  situated  near 
the  base  of  the  tongue ;  their  diameter  is  so  considerable  that  they  have  been 
named  the  blind  or  cfecal  openings  (trous  horgnes).  They  are  the  principal, 
but  not  the  only  organs  of  taste.  Their  surface  is  mammillated,  each 
prominence  corresponding  to  a  single  papilla,  and  being  placed  below  the 
level  of  the  raised  border  encircling  them.  A  deep  fossa  surroimds  them, 
and  limits  at  their  base  a  pedicle,  which  unites  them  to  the  other  portions 
of  the  mucous  membrane. 

The  calyciform  papillas  show,  around  their  peduncle,  a  band  of  adenoid 
tissue ;  and  in  their  substance  conglomerate  glands,  as  in  other  jjarts  of  the 
mucous  membrane.  They  are  covered  by  an  epithelium  containing  some 
scattered  pigment  gi'anules,  the  thickness  of  which  is  much  diminished  at 
the  bottom  of  the  fossa  circumscribing  them. 

Termination  of  the  Gustatory  Nerves. — The  hypoglossal  is  the  motor 
nerve  of  the  tongue,  the  lingual  the  nerve  of  general  sensibility,  and  the 
chorda  tympani  and  glosso-pharyngeal  the  filaments  of  special  sensibility : 
this  appears  to  be  clearly  ascertained  from  the  recent  experiments  and 
observations  of  Lussana.  The  lingual  branch  of  the  glosso-pharyngeal 
nerve  gives  gustatory  sensibility  to  the  posterior  third  of  the  tongue ;  the 
chorda  tympani  to  the  anterior  two-thirds. 

The  gustatory  nerves  present,  as  do  all  those  of  the  organs  of  sense,  a 
particular  mode  of  termination.  First  indicated  by  Axel  Key,  their  sijecial 
manner  of  terminating  has  been  carefully  studied  by  Lowen  and  Schwalbe. 
According  to  these  anatomists,  the  terminal  nerve-tubes  lose  their  medul- 
lary envelope  and,  reduced  to  their  axis-cylinder,  are  thrown  out  in  small 
oval  masses  which  might  be  termed  gustative  bulbs.  These  bulbs  are  more 
particularly  placed  around  the  pedicles  of  the  calyciform  papillae,  in  the 
substance  of  the  epithelium.  They  are  fusiform,  their  inner  extremity 
rests  on  the  mucous  derma,  where  they  receive  the  terminal  nerve-tubes; 
and  their  external  extremity  reaches  the  epithelial  layer,  where  they  are  seen 
either  between  two  'cells,  or  in  an  orifice  pierced  in  a  single  pavement  cell. 
Each  bulb  is  composed  of  a  small  cluster  of  cells,  which  are  distinguished 
from  each  other  by  their  character  and  position ;  those  occupying  the  axis 
of  the  oi'ganule  are  tlie  gustative  cells;  they  are  in  communication  with  the 


THE  APPARATUS  OF  SMELL.  815 

nerve-tubes  on  one  side,  and  on  the  other  are  furnished,  for  the  most  part, 
with  rods  which  attain  the  free  surface  of  the  tongue.  The  sujjerticial,  or 
protective  cells,  completely  envelop  the  preceding;  they  are  a  kind  of 
epithelial-cells  imbricated  like  the  skins  of  an  onion. 

These  sensitive  organs  are  very  numerous  in  the  walls  of  the  calyciform 
papillas,  Schwalbe  reckoned  their  number  at  35,000  in  the  papillae  of  the 
Ox.  They  are  not  met  with  in  these  papillae  only;  Lowen  has  found 
them  in  a  large  quantity  of  fungiform  papillaj,  if  not  in  all.  There  is 
nothing  extraordinary  in  this,  as  the  whole  surface  of  the  tongue  may,  in 
various  degrees,  apjireciate  savours.  (Szabadfoldy  has  described  small 
oval  or  pyriform  bodies,  lying  with  their  long  diameter  parallel  to  the  surface. 
The  axis-cylinders  of  the  gustatory  nerves  enter  these,  and  terminate  at  their 
lower  part  in  a  slight  swelling;  so  that  they  resemble  small  Paccinian 
bodies). 

DIFFERENTIAL   CHARACTERS   IN   THE   APPARATUS   OF   TASTE   IN   OTULE   THAN   SOLIPED 

ANIJIALS. 

In  the  domestic  raammifers,  the  differences  in  this  apjiaratus  are  found  in  the  number 
and  variety  of  forms  of  tlie  papillfe  of  the  tongue. 

In  Euminants,  the  calyciform  papillse  are  disposed  in  two  rows  at  the  base  of  the 
tongue;  they  are  smaller  tliaii  in  the  Horse,  but  more  numerous — about  a  dozen  being 
counted  in  each  row.  In  the  Ox.  the  filiform  pai^illie  are  covered  by  a  horny  sheatli, 
which  renders  them  hard  to  the  toucli. 

The  Pici,  like  Solipeds,  has  only  two  calyciform  papillsp. 

In  the  Bog  and  Cat,  there  are  two  principal  papillae,  and  in  their  vicinity  some  smaller 
calyces.  The  filiform  papillfe  are  composite,  and  covered  by  a  tliick  horny  layer. 
Between  them,  regularly  placed,  are  seen  the  fungiform  papillae,  which  have  a  brilliant 
aspect  when  looked  at  obliquely  to  the  surface  of  the  tongue. 

COMPARISON   OF   THE   APPARATUS   OF   TASTE   IN   MAN   WITH   THAT   OF   ANIMALS. 

This  has  been  already  alluded  to  at  page  364. 


CHAPTER  III. 

APPAKATUS    OF   SMELL. 


The  sense  of  smell  gives  the  appreciation  of  odorous  emanations  to  animals. 
The  active  instruments  of  this  sense  are  the  filaments  of  the  first  pair  of 
encephalic  nerves,  which  ramify  in  the  upper  jxart  of  the  pituitary  membrane  ; 
this  becomes,  with  the  cavities  it  lines,  the  olfactory  apparatus.  These  parts 
have  been  already  referred  to  at  page  444. 

(The  olfactory  filaments,  passing  down  from  the  olfactory  ganglion,  form 
a  plexus  upon  the  surface  of  the  pituitary  membrane.  These  filaments,  as 
already  noted,  difter  widely  from  those  of  the  ordinary  ceplialic  nerves,  in 
containing  no  white  substance  of  Schwann,  but  are  nucleated  and  finely- 
granular  in  structure,  and  resemble  greatly  the  gelatinous  form  of  nerve- 
fibres.  Their  distribution  is  limited  to  the  menabrane  at  the  upper  third  of 
the  nasal  septum,  the  upper  part  of  the  turbinated  bones,  and  the  wall  of 
the  nasal  cavities  adjoning  the  cribriform  plate  of  the  ethmoid  bone :  all 
this  surface  being  covered  with  an  epithelium  of  a  rich  sepia-brown  hue. 
As  has  also  been  mentioned,  Schuitze  divides  these  cells    into  two  sets: 


816 


THE  APPARATUS  OF  THE  SENSES. 


Fie;.  381. 


one  (Fig.  382,  a)  being  described  as  terminating  externally  by  truncated 
flat  surfaces,  which  cannot  be  observed  to  be  covered  by 
any  membrane  sej)arate  from  the  contents  of  the  cell. 
These  contents  api:)ear  to  consist  of  protoplasma  with  a 
yellow  granular  aspect  externally,  while  at  the  lower 
part  an  oval  nucleus  imbedded  in  transparent  protoplasm 
can  be  easily  seen.  At  their  attached  end,  these  cells  be- 
come attenuated,  and  may  be  traced  inwards  for  a  con- 
siderable distance  until  they  expand  into  a  broad  flat 
sheet  or  plate,  which  is  never  coloured,  though  it  fre- 
quently presents  a  granular  appearance.  The  processes 
passing  off  from  this  appear  to  be  continuous  with  the 
fibres  of  the  submucous  connective  tissue.  Towards 
the  margin  of  the  true  olfactory  region,  cells  perfectly 
analogous  to  these  are  met  with,  the  only  difference 
being  that  they  present  a  well-defined  band  or  seam  at 
their  free  extremity,  which  is  surrounded  by  a  circle  of 
FIBRES  or  ULTIMATE  cilia  (Fig.  382,  c).  The  cells  of  the  second  set  (Fig. 
382,  h)  are  continuations  of  the  nerves,  and  have  been 
named  olfadorij  cells.  They  are  thin,  fibrous,  or  rod-like 
bodies,  terminating  at  the  same  level  as  the  proper 
epithelial  cells,  and  presenting,  when  traced  inwards,  a  series  of  varicose 
swellings  directly  continuous  with  the  prolongations  of  deeper-seated  nerve- 
cells.  Clarke  states  that  the  nerve-fibres,  on  reaching  the  base  of  the 
epithelial  layer,  divide  into  finer  and  finer  branches,  to  form  a  network  with 
numerous  interspersed  nuclei,  through  which  they 
are  probably  connected  with  the  olfactory  cells  (Fig. 
382,./).  The  proper  epithelial  cylinders  (d,  e)  are 
connected  at  their  bases  with  the  septa  formed  of  the 
connective  tissue  belonging  to  the  subepithelial  glan- 
dular layer.) 


RAMIFICATIONS  OF 
OLFACTORY  NERVES 
OF   DOG. 


Fig.  382. 


CHAPTEE  IV. 


APPAEATUS   OF  VISION. 


Designed  for  the  perception  of  external  images  ren- 
dered visible  by  the  luminous  rays,  the  sense  of 
sight  depends  upon  the  excitability  of  the  optic  nerve, 
the  terminal  extremity  of  which  is  expanded  as  a  thin 
membrane  at  the  back  of  each  eye.  The  latter  is  a 
globular  organ  lodged  in  the  orbital  cavity,  attached  to 
muscles  which  can  move  it  in  various  directions, 
and  protected  by  membranous  and  movable  screens 

CELLS  OF  THE  OLFACTORY  kuowu  as  tlic  eyeltdls,  whose  play  over  the  surface  of 
MUCOUS  MEMBRANE.      tho  cyo  is  facilitated  by  the   lachrymal  fluid,  which 

a,   b,   c,    After    Schultze ;  j^^      ^  ^j^g^j,  -^j^gj.  g^^.^j^^g  gQj,g|.,j^jj^^  jj^Qjg|._ 

a,  e,  f.  After  Lockhart         -Vm  ..7  ^•'  77       ^  ti 

Qjjjj!].g'  The  essential  organ  oj  vision,  or  globe  oj  the  eye, 

will  be  first  described ;  then,  under  the  designation 

of  the  accessory  portions  of  the  visual  ajyjparatus,  we  will  notice  the  receptacle 


THE  EYE. 


817 


of  this  globe,  or  orbital  cavity,  the  muscles  that  move  it,  the  protective  mem- 
branes or  eyelids,  the  memhrana  nictltans  or  accessory  eyelid,  and,  lastly,  the 
lachrymal  apparatus,  which  concurs  in  the  protection  of  the  oculai-  globe  by 
the  fluid  it  incessantly  throws  out  upon  its  surface. 

Article  I. — The  Essential  Organ  of  Vision,  or  Ocular  Globe. 

(Fig.  SS\i.) 

{Preparation. — The  eye  should  be  as  fresh  as  possible.  All  the  fat  and  muscles 
should  be  carefully  removed  with  scissors,  the  optic  nerve  being  allowed  to  remain.) 

The  globe,  or  ball  of  the  eye,  is  a  spherical  shell,  whose  interior  is  filled 
with  fluid  or  semifluid  parts,  named  the  humours  or  media  of  the  eye.  The 
•wall  of  this  shell  is  formed  by  a  continuous,  very  resisting,  colourless 
envelope,  limpid  and  translucid  in  its  anterior  portion,  which  constitutes  the 
transparent  cornea,  and  white  and  opai^ue  for  the  remainder  of  its  extent, 
known  as  the  sclerotica. 

On  the  inner  face  of  the  sclerotica  is  a  second  tunic — the  choroid :  a  black 
membrane  that  lines  the  posterior  face  of  the  retina,  and  which,  near  where 
the  two  constituent  portions  of  the  external  envelope  imite,  projects  into  the 
interior  of  the  eye  an  elliptical  diaphragm  with  a  large  opening  in  its  centre 
— the  iris.  Immediately  behind  this  disc  is  suspended  or  set,  like  a  rose- 
brilliant,  in  the  centre  of  a  circular  zone  depending  from  the  choroid, 
a  biconvex  body — the  crystalline  lens,  one  of  the  media  of  the  eye,  and 
which  divides  the  interior  of  its  cavity  into  two  compartments :  a  posterior, 
very  large,  occupied  by  the  vitreous  humour ;  and  an  anterior,  itself  divided 
by  the  iris  into  two  chambers  of  uneq[ual  dimensions,  which  contains  the 
aqueous  humour. 

Viewed  externally,  and  as  a  whole,  the  organ  resulting  from  the  union 
of  all  these  parts  represents  a  globular  body,  the  anterior  region  of  which 
corresponds  to  the  cornea,  and  is  more  convex  than  the  other  points  :  a 
circumstance  that  tends  to  increase  the  antero-posterior  diameter  of  the  eye. 
But  as  this  ocular  sphere,  to  which  is  added,  in  front,  this  segment  of  a 
smaller  sphere,  is  sensibly  depressed  from  before  to  behind,  it  results  that 
the  other  two  principal  diameters  —  the  vertical  and  transversal  —  offer 
about  the  same  dimensions  as  the  first ;  Girard  has  even  stated  that  the 
latter  is  the  least.  With  an  eye  hardened  by  chromic  acid,  we  have 
found  that  the  transverse  diameter  measured  0",036,  and  the  vertical  0",040 
(1-417  X  1-575  inches). 

Two  paragraphs  will  be  devoted  to  the  description  of  the  constituent 
parts  of  the  globe :  one  for  the  membranes,  the  other  for  the  media. 


THE   MEMBRANES    OF    THE    EYE. 

1.  Hie  Sclerotic.     (Fig.  383,  b.) 

The  sclerotic  is  a  white,  very  solid  membrane,  forming  in  itself  about 
fom--fifths  of  the  external  shell  of  the  eye. 

Its  external  face,  in  relation  with  the  recti  muscles  and  adipose  tissue, 
receives  posteriorly,  though  lower  than  the  middle,  the  insertion  of  the 
optic  nerve,  which  passes  thi-ough  it  and  the  choroid  to  form  the  retina.  Its 
internal  face  is  loosely  united  to  the  choroid  by  vessels,  nerves,  and 
cellular  tissue. 

In  front,  the  sclerotic  shows  an  elliptical  opening  whose  greatest  diameter 


818 


THE  APPARATUS  OF  THE  SENSES. 


is  transversal,  and  whose  border,  bevelled  on  the  inner  side,  is  closely  united 
to  the  circumference  of  the  cornea.  The  substance  of  this  membrane  is 
traversed  by  numei-ous  vessels  and  nerves,  and  is  not  of  the  same  thickness 
throughout ;  at  the  back,  around  the  entrance  of  the  optic  nerve,  it  is 
thickest ;  it  then  diminishes  gradually  towards  the  larger  axis  of  the  organ, 
and  afterwards  increases  until  it  meets  the  cornea. 

Fiff.  383. 


THEORETICAL   SECTION   OF   THE   HORSE'S   EYE. 

a,  Optic  nerve;  6,  Sclerotic,  c,  Choroid;  d,  Retina;  e,  Cornea;  /,  Iris;  g,  h,  Ciliary- 
circle  (or  ligament)  and  processes  given  off  by  the  choroid,  though  represented  as 
isolated  from  it,  in  order  to  mdicate  their  limits  more  clearly ;  i,  Insertion  of 
the  ciliary  processes  on  the  crystalline  lens ,  j,  Crystalline  lens ;  k,  Crystal- 
line capsule;  /,  Vitreous  body;  ?»,  ?i,  Anterior  and  posterior  chambers ;  o.  The- 
oretical indication  of  the  membrane  of  the  aqueous  humour ;  p,  p,  Tarsi ;  q,  q, 
Fibrous  membrane  of  the  eyelids ;  r,  Elevator  muscle  of  the  upper  eyelid ;  s,  s. 
Orbicularis  muscle  of  the  eyelids;  t,  t,  Skin  of  the  eyelids;  u,  Conjunctiva;  v. 
Epidermic  layer  of  this  membrane  covering  the  cornea ;  x,  Posterior  rectus  muscle ; 
y,  Superior  rectus  muscle,  z,  Inferior  rectus  muscle;  w,  Fibrous  sheath  of  the 
orbit  (or  orbital  membrane). 

STRrcTUEE. — The  sclerotic  is  wholly  composed  of  fasciculi  of  fibre- 
cell  ular  tissue  interwoven  in  a  very  close  manner,  with  some  elastic  fibres  and 
little  masses  of  pigment,  especially  at  its  back  part.  Among  these  fasciculi 
a  large  number  pass  from  before  to  behind,  and  these  are  intersected  by 
others  which  are  placed  in  a  circular  manner  around  the  globe.  The  sui^er- 
fioial  fibres  are  continuous  with  the  neurilemma  of  the  optic  nerve.  (The 
optic  nerve,  at  its  entrance  into  the  sclerotic,  is  very  much  constricted, 
and  passes  thi'ough  a  funnel-shaped,  porous  mesh  of  fibrous  tissue  named  the 
lamina  cribrosa,  in  the  centre  of  which  is  a  larger  openiag  than  the  others, 
for  the  passage  of  the  arteria  centralis  retinje — the  porus  opticus.     The  inner 


THE  EYE.  819 

surface  of  the  sclerotic  is  coated  by  a  thin  layer  of  areolar  tissue  stained 
witli  black  pigment — the  lamina  fiisca. ) 

The  arteries  of  the  sclerotic  are  derived  from  the  anterior  and  posterior 
ciliary  ai'teries ;  the  veins  pass  into  trunks  lying  parallel  to  the  ciliary 
arteries.  Nerves  have  been  found  in  the  sclerotic  of  the  Eabbit,  but  in  none 
other  of  the  domesticated  animals.  "  It  is  frequently  found  that  in  the  Ass, 
particularly  when  it  is  old,  the  back  part  of  the  sclerotic  is  encrusted  with 
an  unmistakable  layer  of  bony  matter.  This  fact  was  unknown  to  Carus, 
who  states  that  in  none  of  the  mammalia  does  this  membrane  become 
ossified." — Lecoq.  (In  Birds,  bony  plates  are  found  in  this  region,  and 
some  rei)tiles  also  have  them.) 

2.  The  Cornea.     (Fig.  383,  e.) 

(^Preparation. — The  cornea  should  be  removed  with  the  sclerotic  coat,  by  immersing  the 
eye  under  water,  and  making  a  circular  incision  with  scissors  about  a  quarter  of  an  inch 
from  the  margin  of  the  membrane). 

The  cornea  is  a  transi^arent  membrane  forming  the  anterior  part  of  the 
eye,  to  whose  interior  it  allows  the  light  to  pass.  It  closes  up  the  anterior 
opening  of  the  sclerotic,  and  thus  completes  tiie  external  envelope  or  shell 
of  the  globe,  of  which  it  forms  about  a  fifth  part. 

Elliptical,  like  the  opening  it  closes,  the  cornea  presents:  1,  Two /aces, 
perfectly  smooth — one  external,  convex,  the  other  internal,  concave — form  the 
external  wall  of  the  anterior  chamber ;  2.  A  circumference,  bevelled  on  its 
outer  edge,  and  received  into  the  similar  bevel  around  the  sclerotic  opening, 
like  the  glass  (jf  a  watch  into  its  case. 

Structure. — Three  layers  enter  into  the  composition  of  the  cornea :  an 
external,  internal,  and  middle. 

Middle  layer. — This,  the  proper  cornea,  is  remarkable  for  its  thickness. 
When  pressed  between  the  fingers,  its  two  faces  can  be  easily  made  to  glide 
over  each  other,  a  proof  that  its  tissue  is  disposed  in  superposed  and  parallel 
planes ;  it  is  indeed  possible  to  decompose  the  cornea  into  several  lamiute 
and  lamellfe,  but  as  their  number  varies  witli  the  amount  of  skill  employed 
in  their  separation,  they  should  be  considered  as  an  artificial  production  of 
dissection.  Microscoi>ically  examined,  it  is  found  to  be  formed  by  bundles 
of  excessively  fine  conjuutival  fibrillse,  slightly  undulating,  and  arranged 
parallel  to  the  surface  of  the  cornea.  These  wavy  fasciculi,  when  placed 
alongside  each  other,  leave  numerous  spaces  which  are  oval  in  a  transverse 
section ;  these  commimicate  by  means  of  fine  canaliculi,  and  contain  round 
cellular  elements  which  may  move  from  one  space  to  another. 

Between  the  fasciculi  of  the  cornea  is  found  a  fluid  amorphous  substance, 
"  a  kind  of  transparent  serosity  like  the  cornea  itself,  which  maintains  its 
flexibility,  and  which,  like  it,  also  loses  its  transparency  under  the  influence  of 
different  causes.  It  is  only  necessary,  in  a  fresh  eye,  to  squeeze  the  globe  in 
order  to  produce  a  degree  of  opacity  in  the  cornea  which  mil  be  more  or 
less  great  in  proportion  to  the  amount  of  pressure  exercised.  Is  a  similar 
effect  produced  by  the  swelling  of  the  eye  when  the  cornea  becomes  opaque 
in  ophthalmia  ?" — Lecoq. 

The  external  layer  is  only  the  conjunctival  epithelium  spread  over  the 
anterior  face  of  the  cornea.  This  epithelium  is  stratified,  flattened  on  its 
surface,  but  cylindrical  below,  where  it  rests  on  the  middle  layer,  and  from 
which  it  is  not  separated,  as  in  many  species  of  animals,  by  a  proper 
limitary  membrane. 

The  inner  layer  is  a  portion  of  the  membrane  of  the  aqueous  humour. 


820  THE  APPABATUS  OF  THE  SENSES. 

It  is  composed  of  a  membrane  that  becomes  slightly  fibrous  at  the 
periphery  of  the  cornea,  where  it  forms,  in  passing  on  to  the  iris,  the 
pectinated  ligament.  It  has  also  a  covering  of  polygonal  epithelial  cells, 
which  are  provided  with  a  large  nucleus. 

(Some  authorities  give  five  layers  to  the  cornea,  the  first  being  the 
conjunctival.  The  second  consists  of  a  very  elastic  tissue,  perfectly 
structureless,  and  possessing  a  remarkable  tendency  to  curl  up;  while 
boiling,  or  the  action  of  acids,  does  not  render  it  ojiaque  as  with  the  other 
layers ;  very  fine  fibres  pass  obliquely  between  it  and  the  next  layer — the 
cornea  proper — consisting  of  a  large  number  of  strata  with  branched 
fusiform  cells.  The  fourth  layer  is  also  elastic  and  like  the  second,  though 
thinner.  The  fifth  layer  ci^nsists  of  the  ej)ithelial  cells  already  mentioned. 
Wilson  says  that  the  oj)acity  of  the  cornea  produced  by  pressure  on  the 
globe,  results  from  the  infiltration  of  fluid  into  the  areolar  tissue  connecting  • 
its  layers,  and  that  this  appearance  cannot  be  produced  in  a  sound  living 
eye,  although  a  small  quantity  of  serous  fluid  (liquor  corneal)  is  said  to 
occupy  the  spaces  in  that  tissue.) 

Vessels. —The  cornea  has  but  little  vascularity.  The  vessels  form  loops 
around  its  borders,  and  in  the  Sheep  they  advance  to  near  the  middle  of  its 
surface. 

Nerves. — These  were  discovered  by  Schlemm.  They  penetrate  by  the 
periphery  of  the  coriiea,  and  form  a  network  on  its  sui'face.  According  to 
Kiihne,  Hoyer,  and  Couheim,  the  ultimate  nervous  ramifications  pass  into 
the  epithelium  of  the  anterior  face,  and  arrive  between  the  most  superficial 
cells. 

3.  The  Choroid  Coat.     (Fig.  383  c.) 

(Preparation. — If  the  cornea  has  not  yet  been  removed,  it  and  the  sclerotic  may  now 
be  dissected  away  from  the  choroid  or  second  tunic.  Tiie  connections  between  tliem  are 
closest  at  the  circumference  of  tiie  iris,  and  at  the  entrance  of  the  ojDtie  and  ciliary  nerves 
and  arteries.  Fine  blunt-poinled  scissors  are  necessary.  A  small  portion  of  the 
sclerotic,  near  its  anterior  circumference,  is  pinched  up  and  clipped  ofi',  the  edge  of  the 
incision  is  rai.sed,  the  circumference  of  the  sclerotic  divided,  and  tliat  tunic  removed 
piecemeal;  a  gentle  pressure  with  the  edge  of  the  knife  will  remove  it  from  its 
attachments  aroimd  the  circumference  of  the  iris.  Tliis  dissection  is  best  conducted 
under  water.  The  ciliary  nerves  and  long  ciliary  arteries  will  be  seen  passing  forward, 
between  the  sclerotic  and  choroid,  to  the  iris.) 

The  choroid  is  a  thin,  dark-coloured  membrane  spread  over  the  inner 
face  of  the  sclerotic,  whose  general  conformation  it  rejjeats.  It  is  divided 
into  two  zones  by  the  ora  serrata — a  denticulated  line  which  corresponds  to 
the  point  where  the  retina  changes  its  characters. 

Posterior  or  choroid  zone. — Throughout  the  extent  of  this  zone  the 
choroid  is  uniformly  thin,  and  corresponds,  by  its  external  face,  to  the 
sclerotic ;  by  its  internal  face,  it  is  in  contact  with  the  retina,  but  does  not 
adhere  to  it.  Posteriorly,  it  shows  an  ojjening  through  which  the  optic 
nerve  passes.  In  front,  at  the  anterior  ojjening  of  the  sclerotic,  it  is 
continuous  with  the  anterior  zone. 

The  inner  face  of  the  choroid  is  not  uniform  in  colour,  being  perfectly 
black  in  the  lower  part  of  the  eye ;  this  is  abruptly  terminated  at  a 
horizontal  line  that  passes  about  the  8th  or  9th  part  of  an  inch  above  the 
optic  papilla.  From  this  line,  on  the  segment  of  a  circle  from  y*y  to  -/^  of 
an  inch  in  height,  it  shows  most  brilliant  colours :  at  first  blue,  then  an 
azure-blue,  afterwards  a  brownish-blue,  and  after  this  the  remainder  of  the 
eye  is  occupied  by  an  intense  black.     The  bright  portion  is  the  tapetum. 

Anterior  or  ciliary  zone. — This  includes  two  parts :  the  "  ciliary  circle 


THE  EYE. 


821 


(or  ligament) "  and  tlie  "  ciliary  body."  The  ciliary  circle,  ligament,  or 
mvscle  {annuliis  alhidus)  varies  in  width  from  one  to  two  millimetres;  its 
external  face  adheres  closely  to  the  sclerotic,  and  its  internal  is  confounded 
with  the  ciliary  body ;  the  posterior  border  is  continuous  with  the 
choroid  zone,  near  the  canal  of  Fontana  (ciliary  canal).  The  anterior 
border  gives  attachment  to  the  greater  circumference  of  the  iris.  Its 
structure  and  uses  will  be  referred  to  hereafter. 

The  ciliary  body  (corjms  ciliare)  forms  a  kind  of  zone  or  ring,  wider  than 
the  ciliary  ligament,  and  consequently  overlaps  the  latter  before  and 
behind.  It  extends,  on  one  side,  on  the  inner  face  of  the  choroid,  and  on 
the  other,  on  the  posterior  face  of  the  iris.  When  the  cornea  and  sclerotic 
are  removed  so  as  to  expose  the  ciliary  ligament,  this  zone  is  not  seen ;  and 
to  discover  it,  it  is  necessary  to  excise  all  the  posterior  part  of  the  shell  of 
the  eye  by  a  cii'Ciilar  incision,  and  evacuate  tlie  vitreous  humour.  We  then 
observe,  around  the  crystalline  lens,  a  wide,  black  circle,  forming  very 
regular  radiating  folds  {ciliary  processes)  projecting  inwards  by  their  inner 
extremities,  and  appearing  in  the  posterior  chamber  of  the  eye,  after  cutting 
away  the  iris ;  all  abut  by  these  extremities  on  the  circumference  of  the 
lens,  which  they  do  not  quite  reach,  although  the  latter  is  sustained  by,  and 
"  set  "  in,  the  middle  of  the  ligament. 

These  radiating  folds  (Fig.  384, 4)  are  from  110  to  120  in  number  in  the 
Horse,  and  are  constituted  by  little  j)arallel  leaves,  Avider  at  their  inner  than 
their  outer  extremity ;  the  furrows  that  separate  them  posteriorly  are 
partly  concealed  by  the  prolongation  of  the  retina  that  constitutes  the 
zonula  of  Zinn.  The  coronet  formed  by  the  ciliary  processes  is  usually 
asymmetrical. 

(Between  the  sclerotic,  the  cornea,  and  the  ciliary  ligament,  exists  a 
minute  circular  canal— the  ciliary  canal, 
canal  of  Schlemm,  sinus  circularis  iridis, 
circulus  venosus  orhiculi  ciliaris,  or  canal  of 
Fontana,  from  its  discoverer.  It  is  sur- 
mised to  be  a  venous  sinus,  as  it  can 
always  be  injected  from  the  arteries.) 

Structure. — The  choroid  zone  is  com- 
posed of  four  superposed  layers:  1,  The 
external  is  formed  by  a  network  of  con- 
nective elastic  fibres,  among  which  are 
disseminated  a  great  number  of  pigment 
cells ;  2,  The  second  layer  is  constituted  by 
a  network  of  large  arteries  and  veins — 
the  posterior  ciliary — and  a  plexus  of 
nerves  (ciliary)  accompanied  by  ganglia  and 
some  (stellate)  pigment  cells.  (The  veins 
are  arranged  with  great  regularity  in  droop- 
ing branches,  to  form  the  vasa  vorticosa 
(Fig.  386,  2,  4) ;  these  are  chiefly  on  the 
outer  surface  of  the  layer,  the  arteries 
ramifying  on  the  inner  surface.)  3,  The 
third  layer,  or  tunica  JRuyschiana,  has  for 
its  basis  an  amorphous  substance  containing 
a  network  of  exceedingly  fine  caj)illaries 
(extending  to  the  ciliary  processes) ;  4,  The 
internal  layer  is  composed  of  hexagonal  cells,  regularly  placed  one  upon  the 
55 


Fig.  384. 


ANTERIOR  SEGMENT  OP  A  TRANSVERSE 
SECTION  OF  THE  GLOBE  OF  THE  EYE 
(human),    SEEN    FROM    WITHIN. 

1,  Divided  edge  of  the  three  tunics, 
sclerotic,  choroid  (the  dark  layer), 
and  retina ;  2,  Pupil ;  3,  Iris,  the 
uvea;  4,  Ciliary  processes;  5,  Den- 
ticulated anterior  border  of  the 
retina. 


822 


THE  APPARATUS  OF  THE  SENSES. 


Fig.  385. 


other  on  the  surface  of  a  structureless  laminae ;  the  cells  are  provided  with  a 
nucleus,  and  contain  pigment-granules  which  exclusively  occupy  their  anterior 
moiety.  (On  the  choroid  this  cell  formation  is  single,  but  on  the  iris  and  ciliary 
processes  there  are  several  layers.  A  very  delicate  memhvane— membrane 
of  Bruch — has  been  described  as  lining  the  inner  surface  of  the  choroid,  and 
retaining  the  pigment  in  its  place  ;  this  membrane  may  be  seen  on  the 
posterior  surface  of  the  iris,  and  it  probably  prevents 
the  pigment  being  removed  by  the  aqueous  humour.) 
The  use  of  the  choroid  membrane  is  to  convert  the 
ocular  globe  into  a  veritable  darkened  chamber.  (The 
pigment  absorbs  the  rays  of  light  which  pass  through 
the  retina,  and  thus  prevents  their  becoming  reflected 
and  confusing  the  vision.  The  brilliant  metallic- 
coloured  layer  named  the  tapeium  is  more  particularly 
observed  in  nocturnal  animals,  and  especially  in  the 
Carnivora ;  it  is  due  to  the  presence  of  a  thick  layer 
of  wavy  fibrous  tissue  outside  the  choroidal  epithe- 
lium. By  reflecting  the  rays  of  light  a  second  time 
through  the  retina,  it  probably  enables  the  animal 
to  see  better  at  night.  It  is  the  cause  of  the  glare 
perceived  in  the  eyes  of  Cats  aud  other  creatures  in 
the  dark.) 

The  ciliary  ligament  is  a  contractile  body,  being 
composed  of  unstriped  muscular  fibres  which  are  arranged  in  orbicular 
fasciculi,  or  extend  backwards  (and  are  lost  in  the  choroid,  behind  the  ciliary 
processes).  These  fibres  are  intermixed  in  the  plexus  of  ciliary  nerves,  on 
whose  track  small  ganglia  are  formed.  By  its  contractions,  the  ciliary 
muscle  (or  ligament)  plays  an  important  part  in  accommodating  the  eye  to 
the  perception  of  objects  at  different  distances.  (In  Birds,  the  muscular 
fibres  are  strijied.) 

The  ciliary  body  or  processes  are  formed  by  intercrossed  fasciculi  of  con- 
nective tissue,  vessels,  aud  some  imstriped  fibres;  their  inner  surface  is 
covered  by  pigment,  like  that  of  the  choroid  zone. 


CELLS  FROM   PIGMENTUM 

NIGRUM. 
a,     Pigmentary     granules 

concealing  the  nucleus ; 

b,  The  nucleus  distinct. 


4.  The  Iris.     (Figs.  383  /;  386,  6.) 

The  iris  forms  in  the  interior  of  the  eye,  at  the  anterior  opening  of  the 
sclerotic,  and  in  front  of  the  crystalline  lens,  a  veritable  diaphragm  pierced 
with  a  central  opening — the  j3?fj3i7 — which  contracts  or  dilates  according 
to  the  intensity  of  the  light  and  the  distance  of  the  objects  to  which  the 
vision  is  directed.  This  diaphragm  divides  the  space  between  the  cornea 
and  the  anterior  face  of  the  lens  and  internal  extremities  of  the  ciliary 
processes,  into  two  compartments  or  chambers  of  unequal  size :  the  anterior 
being  the  largest,  and  the  posterior  having  only  a  virtual  existence,  the  iris 
being  close  to  the  crystalline  lens. 

In  shape,  the  iris  is  elliptical,  like  the  cornea  and  the  sclerotic  aperture. 

Its  anterior  face  is  flat  or  very  slightly  convex,  and  has  very  marked 
circular  farrows  and  radiating  strife,  noticeable  only  at  the  outer  cir- 
cumference of  the  membrane.  It  is  diversely  coloured,  not  only  according 
to  species,  but  also  in  individuals.  In  Solipeds,  it  has  nearly  always  a 
brownish-yellow  hue ;  though  sometimes  it  is  nearly  white  or  bright  grey, 
when  the  animal  is  said  to  be  "  wall-eyed." 

The  posterior  face,  in  relation  with  the  lens  and  ciliary  processes,  is 


TEE  EYE. 


823 


covered  by  a  very  thick  layer  of  pigment  named  the  uvea:  portions  of 
which,  supported  by  a  small  pedicle,  frequently  pass  through  the 
pupillary  aperture  and  appear  in  the  anterior  chamber  of  the  eye,  where 


THE   EYE  (human)  WITH   THE   SCLEROTIC   COAT   REMOVED. 

1,  Sclerotic  coat ;  2,  Veins  of  the  choroid  ;  3,  Ciliary  nerves ;  4,  Veins  of  the 
choroid ;  5,  Ciliary  ligament ;  6,  Iris. 

they  are  known  as  "  soot-balls "  or  corpora  nigra.  (There  are  frequently 
several  of  these  black  spongy  masses,  which  are  generally  attached  to  the 
upper  border  of  the  pupil ;  on  the  lower  margin,  when  present,  they  are 
much  smaller.  Their  colour  is  a  brownish-black.  They  are  sometimes  so 
large  as  to  give  rise  to  apprehensions  of  injury  to  the  vision.) 

The  larger  circumference  of  the 
iris  is  attached  to  the  ciliary  liga- 
ment, which  unites  it  to  the 
choroid ;  it  is  also  related  to  the 
margin  of  the  cornea,  as  well  as  to 
that  of  the  sclerotic  opening. 

The  lesser,  or  internal  circum- 
ference, is  elliptical,  and  cii'cum- 
scribes  the  pupillary  aperture. 

Structure. — The  organisation 
of  the  iris  has  been  much  dis- 
cussed ;  but  at  present  it  is  ad- 
mitted that  its  principal  element 
is  unstriped  muscular  fibre.  A 
proper  membrane  and  two  epi- 
thelial layers  enter  into  its  form- 
ation. The  proper  membrane  has, 
for  its  framework,  circular  or  radia- 
ting fasciculi  of  wavy  connective 
tissue,  with  pigment  cells.  Be- 
tween the  fasciculi  are  placed  the 
unstriped  fibres  ;  these  are  disposed 
in  a  circular  manner  around  the 
pupil  to  constitute  the  pupillary  sphincter,  and  others  radiate  from  the  lesser 


MUSCULAR  STRUCTURE   OF   THE   IRIS   OF   A 
WHITE    RABBIT. 

a,  Sphincter  of  the  pupil ;  b,  b,  Radiating  fasciculi 
of  dilator  muscle ;  c,  c,  Connective  tissue  with 
its  corpuscles. 


824  THE  APPABATVS  OF  THE  SENSES. 

circumference  towards  the  ciliary  ligament  to  form  the  dilator  of  the  pupil. 
The  very  fine  radiating  vessels  are  disseminated  among  these  fibres,  and 
pass  to  the  anterior  ciliary  trunks.  The  nerves  supplied  to  the  iris  are 
from  the  ciliary  plexus. 

The  anterior  epithelial  layer  is  composed  of  the  polygonal  cells  of  the 
aqueous-humour  membrane,  already  described  as  existing  on  the  posterior 
sui'face  of  the  cornea. 

The  posterior  epithelial  layer,  or  uvea,  is  constituted  by  pigment  cells 
analogous  to  those  of  the  choroid,  but  less  regular  in  shape. 

In  the  foetus,  the  pupil  is  closed  by  a  very  thin  transparent  membrane — 
the  memlrana  pupillaris.  (It  is  identical  with  the  anterior  layer  of  the 
capsule  of  the  crystalline  lens.) 

5.  The  Betina.     (Fig.  383,  d) 

{Preparation. — The  choroid  must  be  removed  under  water  by  means  of  forceps  and 
scissors,  after  the  lens  and  vitreous  humour  have  been  evacuated.  A  good  view  of  the 
retina  is  to  be  had  by  looking  through  the  vitreous  humour,  after  the  leus  and  iris  have 
been  excised  from  an  eye  ) 

The  retina,  the  essential  portion  of  the  eye,  considered  as  the  terminal 
expansion  of  the  optic  nerve,  extends  over  the  internal  face  of  the  choroid, 
from  which  it  is  easily  separated,  and  lies  between  that  membrane  and  the 
vitreous  hmnour.  On  arriving  at  the  ciliary  body,  it  is  exactly  moulded  on 
the  radiating  folds  of  its  posterior  face,  and  with  them  is  prolonged  to  the 
circumference  of  the  crystalline  lens,  on  the  capsule  of  which  it  appears  to 
become  lost,  after  being  closely  united  to  it.  It  also  adheres  so  firmly  to 
the  ciliary  processes  that,  in  the  fresh  eye,  it  is  impossible  to  detach  it. 
When  the  eye  has  been  kept  some  time,  however,  the  two  are  easily 
separated ;  the  cornea  is  removed  with  a  portion  of  the  sclerotic ;  then 
dividing  the  iris  into  several  pieces  by  diverging  incisions,  each  is  turned 
outwards  by  a  slight  traction  that  ruptures  the  ciliary  zone  and  the 
choroid  ;  the  retina  being  thus  divested  of  the  parts  which  cover  it  anteriorly, 
is  seen  to  form  around  the  lens  a  kind  of  Elizabethan  ruff,  dovetailing  with 
the  ciliary  processes.  This  plaited  collar  has  been  named  the  zonula  of 
Zinn  (zonula  ciliaris,  and  ora  serratd).  The  majority  of  anatomists,  through 
having  neglected  to  study  this  part  in  fresh  eyes,  have  wrongly  considered 
it  as  distinct  from  the  retina. 

At  the  point  where  the  optic  nerve  enters  the  eye,  there  is  found  on  the 
retina  a  small  oval  elevation,  whose  larger  axis  is  about  \  inch  ;  this  little 
prominence  is  the  optic  papilla  or  punctum  ccecum  (papilla  conica).  From 
its  centre  emerge  the  vessels  of  the  retina. 

Structure. — The  retina  is  the  most  important  of  the  three  tunics  of  the 
eye,  and  it  is  also  the  thinnest  and  most  delicate.  It  forms  a  soft,  pulpy, 
transparent  expansion  when  quite  fresh,  but  is  white  and  opalescent  soon 
after  death.  It  is  composed  of  connective  tissue  and  nerve  elements, 
which  are  arranged  to  form  nine  or  ten  superposed  layers. 

Connective  Tissue, — This  is  very  delicate  and  nucleated,  and  forms 
two  thin  laminsB  named  the  external  and  internal  limitary  membranes ;  these 
are  connected  by  radiating  fibres  which  pass  through  the  nerve  elements, 
and  anastomose  very  closely  in  the  molecular  layer. 

Nerve  Elements. — These  are  distributed  in  seven  layers,  which  present 
the  following  characters : 

1.  Layer  of  rods  and  cones.    (Fig.  388,  1.) — This  is  also  termed  the  mem- 


THE  EYE. 


825 


Ficr.  388. 


hrana  Jacdbi  (hacillary  or  columnar  layer).     It  is  situated  between  the  inner 
face  of  the  choroid  and  the  external  limitary  membrnne. 

Bods  and  cones,  regularly  mixed,  make  up  its  structure.  Each  of  these 
comprises .  two  portions  or  segments  (separated  by  a  bright  transverse  Hne). 
The  outer  segment  (or  shaft)  is  brilliant  and 
refractive,  and  consists  of  a  small  stalk  termi- 
nating in  a  point  for  the  cones ;  with  a  shorter 
stalk  than  the  inner  segment  for  the  latter, 
and  equal  in  length  to  this  segment  for  the 
rods.  The  inner  segment  is  a  small  granular 
shaft  for  the  rods,  and  an  enlargement  whose 
base  is  towards  the  centre  of  the  eye  for  the 
cones.  The  elements  of  this  layer  quickly 
alter  after  death. 

2.  External  granular  layer  (2), — This  is 
comprised  between  the  external  limitary  and 
the  intermediate  membrane.  It  is  formed  by 
the  granulations  of  the  cones  and  those  of  the 
rods :  small  oval  nucleated  cells,  furnished 
with  an  external  prolongation  that  joins  tbem 
to  the  base  of  the  cones  and  rods,  and  an  ex- 
ternal varicose  prolongation  which  often  en- 
larges on  arriving  at  the  intermediate  layer. 

3.  Intermediate  layer  (3), — This  is  very 
thin,  and  composed  of  flexuous  fibrillse,  which 
are  connected  with  the  adjoining  elements. 

4.  Inner  granular  layer  (4). — In  this  we 
find  cells  whose  membrane  is  in  contact  with 
the  nucleus ;  these  cells  have  minute  prolong- 
ments  analogous  to  those  of  the  external 
granular  layer,  and  which  connects  them  with 
the  surrounding  layers. 

5.  Molecular  layer  (5). — One  of  the  thickest, 
this   layer    (the    grey    vesicular)    presents    a 
granulous  aspect ;  in  its  mass,  the  connective 
tissue  forms  a  close  mesh,  in  the  midst  of  which  are  seen  fine  fibrillse  passing 
in  every  direction. 

6.  Ganglionic  layer  (6). — This  is  composed  of  a  single  stratum  of 
ramified  nerve-cells,  whose  prolongations  pass  into  the  molecular  layer, 
where  they  join  the  filaments  of  the  next  layer. 

7.  Layer  of  optic-nerve  fibres  (7). — The  fibres  (ultimate  fibrils)  of  the 
optic  nerve,  in  passing  through  the  sclerotic  and  choroid,  anastomose  with 
each  other,  and  arrange  themselves  in  a  cone  shape,  whose  apex  corresponds 
to  the  papilla  conica  ;  at  this  point  they  suddenly  spread  out  in  every 
direction,  between  the  ganglionic  layer  and  the  limitary  membrane. 

To  sum  up,  the  retina  comprises  the  following  layers,  reckoning  from 
before  to  behind :  1,  Internal  limitary  membrane ;  2,  Layer  of  optic-nerve 
fibres ;  3,  Layer  of  nerve-cells ;  4,  Molecular  layer ;  5,  Inner  granular 
layer ;  6,  Intermediate  granule  layer ;  7,  Outer  granular  layer ;  8,  Outer 
limitary  membrane;  9,  Columnar  layer;  10,  Pigmentary  layer  of  the 
choroid,  if  this  be  attached  to  the  retina,  as  Schultze  proposes. 

It  is  to  be  remarked,  that  at  the  ora  serrata  all  the  nerve  elements  of  the 
retina  disappear,  and   the   membrane,  reduced  to  its  connective  tissue,  is 


VERTICAL  SECTION   OF   EETIKA. 

1,  Bacillar  layer ;  2,  Outer  granu- 
lar layer ;  3,  Intermediate  fibrous 
layer  ;  4,  Inner  granular  layer ; 

5,  Finely-granular  grey  layer ; 

6,  Layer  of  nerve-cells ;  7,  Layer 
of  fibres  of  optic  nerve  ;  8,  Limi- 
tary membrane. 


826 


THE  APPARATUS  OF  THE  SENSES. 


Fig.  389. 


Fiff.  390. 


continuous   witli   the   posterior  face   of    the    ciliary   processes,   where  it 

afterwards  forms  the  zonula  of  Zinn. 

(At  the  papilla  conica,  all  the  other  elements 
than  the  nerve-fibres  are  entirely  absent ;  hence  this 
is  presumed  to  be  a 
"  blind  spot.") 

Blood-vessels. — The 
retina  possesses  a  par- 
ticular vascular  distri- 
bution. The  arteria 
centralis  retince,  with  its 
vein,  enters  the  optic 
nerve  at  a  short  distance 
from  the  globe,  and 
with  it  passes  into  the 
eye;  they  traverse  the 
papilla,  and  immediate- 
ly divide  into  two 
branches,  one  of  which 
is  directed  upwards, 
the    other   downwards. 

Close  and  fine  anastomoses  unite  the  vessels  of 
the  retina  with  the  ciliary  vessels  at  the  back  of  the 
sclerotic. 


CAPILLARIES   IN   THE   VASCULAR 
LAYER   OF    THE    RETINA. 


THE   MEDIA    OP    THE    EYE. 

The  Crystalline  Lens.     (Fig.  383,  j.) 


DIAGRAM   OF    THE   STRUC- 
TURE  OF   THE   RETINA, 

p,  Pigment  cell  of  the 
retina  connected  with  a 
rod ;  n.  Cone  seated  on 
the  membrana  limitans 

externa,  the  inner  seg-  mi      t  •  •       t         •  /     t  i\ 

ment  containing  a  cone  The  lens,  as  its  name   implies,  IS  a  (solid)  trans- 

ellipsoid,  and  a  needle;  parent  body,  sustained  at  the  smaller  circumference 
»"j  />  Pi'oper  fibre  con-  ^f  ^\^q  ^one  formed  by  the  ciliary  processes  (behind 
necting  rod  and   cone   ^^^         -j    ^^^  partially  imbedded  in  the  vitreous 

with  one  ot  the  ceils  ot    ,         ^     \        t,    •     i  •  •       n  t    n   ,,  •. 

the  membrana  fenestra,  humour).  It  IS  biconvex  m  shape,  and  flatter  on  its 
whose  cells  are  in  com-  anterior  than  its  posterior  surface.  We  have  mea- 
munication  with  the  gured  the  lens  of  the  Horse's  eye,  and  find  the  follow- 
membrana  limitans  in-  ^^^  dimensions  :  vertical  diameter  ^ths,  and  trans- 
verse diameter  yo^ths  of  an  inch.  The  posterior  face 
is  evidently  more  convex  than  the  anterior,  for  we 
found  the  transverse  diameter  of  the  last  to  be  x^^ths, 
and  that  of  the  first  -^^ih^  of  an  inch. 

Structure.— The  lens  is  enveloped  in  a  trans- 
parent membrane,   the  capsule,  which  contracts  no 
adhesions  with  it.     Its  thickness  is  uniform  in  the 
Horse,  and  its  tissue  is  slightly  striated  transversely ; 
its  internal  face  is  lined  by  a  layer  of  jiavement  epithelium. 

The  proper  tissue  of  the  lens  is  disposed  in  concentric  layers,  which  the 
microscope  proves  to  be  composed  of  fibres ;  the  outer  layers  are  almost 
fluid  (gelatinous),  but  their  consistence  gradually  increases  towards  the 
centre.  Between  the  proper  tissue  and  the  epithelium  of  the  capsule  are 
two  or  three  layers  of  round  cells,  whose  dissolution  some  time  after  death 
forms  the  liquor  Morgagni — which  is  consequently  nothing  more  than  the 
result  of  a  cadaveric  phenomenon. 

(The  capsule  of  the  lens  is  composed  of  tissue  exactly  similar  to  tho 


terna,  m,  I,  i,  by  means 
of  a  thick  radial  fibre 
with  an  oval  nucleus 
attached ;  g,  g,  Multi- 
polar ganglion  of  nerve 
elements;  o,  p,  Optic 
fibrilla ;  g,  r,  i,  Supposed 
connection  of  the  nucleus 
with  prolongation  of  a 
ganglion  cell. 


TEE  EYE.  827 

elastic  layer  of  the  cornea.  To  examine  the  structure  of  the  lens,  it  is  best 
to  boil  it,  or  to  immerse  it  in  alcohol  or  nitric  acid,  which  renders  it  hard 
and  opaque.  It  is  then  found  to  be  divided  into  three  equal  parts  by  three 
lines,  which  radiate  from  the  centre  to  within  one-third  of  the  circumference ; 
so  that  each  of  these  portions  is  composed  of  hundreds  of  concentric  layers, 
arranged  within  one  another,  like  the  coats  of  an  onion.  According  to 
Kolliker,  these  fibres  are  tubular,  and  contain  an  albuminous  fluid.  If  any 
single  layer  is  examined  with  the  microscope,  it  is  found  to  be  made  up  of 
these  parallel  fibres,  which  measure  about  soVo^^  ^^  ^^  ^^<^^  ^  thick- 
ness, and  are  united  with  each  other  by  finely  serrated  or  scalloped  borders 
that  dovetail  in  the  most  beautiful  manner. 

The  lens  is  nourished  by  means  of  the  extremely  delicate  layer  of 
nucleated  cells  on  its  surface,  which  absorb  nutriment  from  the  capsule.) 

The  lens  receives  neither  vessels  nor  nerves.  In  the  foetus,  the  arteria 
centralis  gives  off  a  branch  which  passes  forward  through  the  vitreous 
humour,  and  enters  the  posterior  face  of  the  lens  ;  but  this  vessel  disappears 
long  before  birth. 

(The  use  of  the  lens  is  to  bring  the  rays  of  light  to  a  focus  upon  the 
retina,  they  being  greatly  refracted  in  passing  through  it.) 

2.  The  Vitreous  Humour.     (Fig.  383,  I.) 

The  vitreous  body,  or  Immour,  occupies  all  the  cavity  of  the  eye  behind  the 
lens  (about  two-thirds  of  the  interior  of  the  eye). 

It  is  a  kind  of  colourless,  transparent  jelly,  much  more  fluid  than  the 
lens,  and  entirely  amorphous,  according  to  Ch.  Eobin  ;  though  the  majority 
of  anatomists  add  some  embryonic  cells.  At  the  surface  of  the  vitreous 
mass  is  a  very  thin  sti'ucture,  the  hyaloid  membrane,  which  is  in  contact, 
externally,  with  the  retina  and  the  posterior  face  of  the  lens. 

(This  hyaloid  membrane  forms  cells,  in  which  the  watery  fluid  consti- 
tuting the  humoiu-  is  contained ;  the  cells  communicate  freely,  and  are 
rendered  apparent  by  freezing  the  eye  or  steeping  it  in  chromic  acid,  when 
it  is  found  that  the  humour  is  intersected  by  a  large  number  of  delicate 
partitions,  with  a  cylindrical  space  in  the  axis  for  the  passage  of  the  central 
artery  in  the  foetus.  The  membrane  is  firmer  on  the  surface  than  else- 
where, so  that  it  serves  as  a  capsule  for  the  humour,  and  sufBces  to  keep  it 
in  shape  after  the  outer  envelopes  of  the  eye  are  removed.  As  mentioned, 
the  lens  is  maintained  in  situ  by  the  zone  of  Zinn.) 

There  has  been  described  around  the  lens,  between  the  hyaloid  membrane 
and  the  zone  of  Zinn  a  circular  passage  named  the  canal  godronne  {canal  of 
Petit),  because  of  its  form.  I  look  upon  this  canal  as  an  artificial  production, 
and  due  to  the  means  employed  to  demonstrate  it  in  mankind  and  animals. 

(This  humour  concurs  in  refracting  the  rays  of  light.) 

3.  The  Aqueous  Humour. 

This  is  a  liquid  that  owes  its  name  to  its  great  fluidity ;  it  is  contained 
in  the  anterior  and  posterior  chambers  of  the  eye,  in  front  of  the  lens.  It  is 
secreted  by  a  particular  membrane,  the  membrane  of  the  aqueous  humour,  or 
membrane  of  Descemet  or  Demoiirs ;  this  is  an  extremely  thin  serous  layer, 
easily  distinguished  on  the  posterior  face  of  the  cornea,  and  admitted  to  exist 
on  the  two  fiices  of  the  iris,  the  ciliary  processes,  and  anterior  face  of  the 
capsule  of  the  lens,  where  it  is  reduced  to  epithelium  only. 


828  TEE  APPARATUS  OF  THE  SENSES. 

(The  chief  function  of  this  humonr  appears  to  be  to  maintain  the  con- 
vexity of  the  cornea,  and  to  facilitate  the  movements  of  the  iris  and  lens  ;  as 
well  as  to  assist,  to  some  extent,  in  refracting  the  light  that  passes  through  it 
to  the  lens  and  retina.  The  rapidity  with  which  this  fluid  can  be  regenerated 
is  very  striking ;  absorption  also  takes  place  very  rapidly  in  the  anterior 
chamber  of  the  eye.  The  frequency  of  adhesions  between  the  iris  and  lens, 
after  attacks  of  ophthalmia,  is  accounted  for  by  the  small  quantity  of  this 
fluid  that  exists  between  them,  as  owing  to  the  smallness  of  the  posterior 
chamber  this  is  reduced  to  a  mere  film.) 

Article  II. — Accessort  Organs  of  the  Visual  Apparatus. 

ORBITAL    CAVITY. 

Situated  at  the  side  of  the  head,  at  the  point  corresponding  to  the  union 
of  the  cranium  and  face,  the  orbital  cavity  is  circumscribed  by  a  bony 
margin,  in  the  formation  of  which  the  orbital  process,  frontal,  lachrymal, 
malar,  and  a  small  portion  of  the  zygomatic  process  of  the  temporal  bone, 
concur.  Posteriorly,  however,  there  are  no  bony  walls,  and  the  cavity,  in 
the  skeleton,  is  confounded  with  the  temporal  fossa.  A  fibrous  membrane 
completes  this  cavity  in  the  domesticated  animals,  and  keeps  it  distinct 
from  the  fossa. 

Designated  the  ocular  sheath  (ocular  membrane  or  periorbita),  this  fibrous 
structure  is  attached,  posteriorly,  to  the  border  of  the  orbital  hiatus,  and 
anteriorly  to  the  inner  face  of  the  orbit ;  being  prolonged  beyond  the 
external  lip  of  this  osseous  rim  to  form  the  fibrous  membrane  of  the  eyelids. 
Strong  externally,  the  ocular  sheath  is  thin  within  the  cavity.  It  is 
traversed  by  vessels  and  nerves,  and  is  composed  of  a  mixture  of  elastic  and 
inelastic  fibres.  (Unstriped  muscular  fibres  have  also  been  described  as 
existing  in  this  orbital  periosteum.) 

Thus  completed,  the  orbital  cavity  has  the  form  of  a  regular  hollow 
cone,  open  at  its  base,  and  closed  at  the  apex,  which  corresponds  to  the 
orbital  hiatus. 

In  the  ordinary  position  of  the  head,  the  opening  of  this  cone  is  directed 
forwards,  downwards,  and  outwards. 

Independently  of  the  globe  of  the  eye,  this  cavity  lodges  the  muscles  that 
move  it,  the  membrana  nictitans,  and  the  lachrymal  gland. 

MUSCLES    OF    THE    EYE.      (Fig.  391.) 

These  are  seven  in  number :  five  termed  recti  muscles,  and  distinguished 
as  posterior,  superior,  inferior,  external,  and  internal ;  two  named  oblique — a 
large  and  small. 

{Preparation. — Detach  the  eyelids  from  the  margin  of  the  orhit,  cutting  away  the  lower, 
but  leaving  the  upper.  Saw  through  the  zygomatic  process  of  the  temporal  bone,  in  front 
of  the  temporo-maxillary  articulatiim,  also  through  the  temporal  process  of  the  zygo- 
maticus,  and  tlie  base  of  the  orbital  process  of  the  frontal  bone;  remove  the  excised 
piece  of  bone,  and  the  temporal  fossa  and  ocular  sheath  are  exposed.  Cutting  through 
the  latter,  the  muscles  of  the  eye  are  seen  disposed  in  a  conical  manner  around  the 
globe ;  dissect  away  the  fat  lodged  among  them,  in  order  to  isolate  them.) 

1.  Posterior  Eectus  Muscle  (or  retractor  oculi). — This  muscle  com- 
pletely envelops  the  extra-cranial  portion  of  the  optic  nerve,  being  a 
muscular  sheath  resembling  in  shape  the  fibrous  lining  of  the  orbit.  Its 
fibres  are  disposed  longitudinally,  arise  around  the  optic  foramen,  and  are 


THE  ACCESSOEY  OBGANS  OF  VISION. 


829 


Ficr.  391. 


inserted  into  the  posterior  part  of  the  external  face  of  the  sclerotic.  It  is 
always  more  or  less  fasciculated,  and  is  most  frequently  separated  into  four 
portions — superior,  inferior,  external,  and  internal. 

In  contractiug,  it  retracts  the  globe  towards  the  back  of  the  orbit.     The 
physiological  tinality  of  this  movement  will  be  noticed  hereafter. 

2.  SuPEuioR,  Inferior,  External,  and  Internal  Kecti  Muscles. — These 
four  muscles  are  placed  longitudinally  on  the  preceding,  and  repeat,  on  a 
lar«e  scale,  the  disposition  of  its  four  bundles.  As  their  borders  are  in 
contact,  they  constitute  a  fleshy  sheath  around  it,  analogous  to  that  which  it 
forms  around  the  optic  nerve.  Exactly  resembling  each  other,  these  four 
muscles  compose  so  natural  a  group,  that  they  may  be  described  together. 
Each  is  a  flat  band,  formed  of 
parallel  fibres,  firmly  attached 
by  its  posterior  extremity  to 
the  back  of  the  sheath,  and  to 
the  interior  of  the  subsphe- 
noidal  canal ;  anteriorly,  it  is 
inserted  by  a  thin  aponeurosis 
into  the  sclerotic,  at  the  mar- 
gin of  the  cornea.  Isolated 
from  one  another,  and  from 
the  retractor,  by  the  mass  of 
fat  belonging  to  the  mem- 
brana  nictitans,  these  small 
muscles  are  related,  externally, 
to  the  ocular  sheath. 

There  is  nothing  par- 
ticular to  be  noted  regarding 
them,  their  position  being 
6u£6.ciently  indicated  by  their 
names.  Their  function  is  to 
bring  the  pupillary  opening 
into  contact  with  the  rays 
of  light,  by  inclining  the 
cornea  towards  them,  either 
upwards,  downwards,  inwards, 
or  outwards ;  or  into  inter- 
mediate      positions,      which 

happens  when  two  adjacent  muscles — the  inferior  and  external  rectus,  for 
instance — combine  their  action  at  the  same  moment. 

3.  Great  Oblique  Muscle  (trochlearis,  or  ohliquus  superior  oculi). — 
Lying  to  the  side  of  the  internal  and  superior  rectus,  and  formed,  like  them, 
of  a  fleshy  band  terminated  by  a  thin  aponeurosis,  this  muscle  differs  from 
the  preceding  in  its  interrupted  course.  Arising  from  the  back  of  the 
orbit,  and  jjassing  forward  against  the  inner  wall  of  that  cavity,  it  reaches  a 
strong  fibrocartilaginous,  pulley-like,  process — a  dependency  of  the  aponeu- 
rosis of  the  orbit — attached  by  its  extremities  to  the  frontal  bone,  at  the 
base  of  the  orbital  process ;  it  passes  through  this  loop,  and  then  bends 
outwards,  to  insinuate  itself  below  the  terminal  extremity  of  the  superior 
rectus,  and  become  inserted  into  the  sclerotic,  between  the  latter  muscle 
and  the  external  rectus. 

This  muscle  pivots  the  eye  inwards  and  upwards  in  the  orbit,  carrying 
the  outer  aspect  of  the  globe  upwards,  and  its  lower  part  outwards ;  this 


MUSCLES   OF    THE    EYEBALL,    VIEWED    FROM    ABOVE. 

1,  Section  of  orbital  process  of  frontal  bone  to  which 
the  fibro-cartilaginous  pulley,  4,  of  the  superior 
oblique  muscle,  5,  is  attached ;  2,  Zygomatic 
process  of  the  temporal  bone ;  3,  Portion  of  sphe- 
noid bone  into  which  the  recti  and  superior 
oblique  muscles  are  implanted  ;  6,  Pathetic!  nerve : 
7,  Internal  i-ectus ;  8,  Superior  rectus  ;  9,  Levator 
palpebrse  muscle;  10,  External  rectus;  11,  Eye- 
ball ;  12,  Upper  eyelid ;  13,  Lower  eyelid ;  14^ 
Inner  canthus  of  eve. 


830  THE  APPARATUS  OF  THE  SENSES. 

faculty  it  owes  to  its  reflexion  in  the  cartilaginous  loop,  as  it  acts  as  if  its 
insertion  was  at  the  angle  it  forms  there. 

4.  Small  Oblique  Muscle  (obliquus  inferior  oculi). — Much  thicker, 
though  veiy  much  shorter  than  the  preceding,  and  almost  entirely  fleshy, 
this  muscle  is  placed  in  a  transverse  direction  on  the  globe  of  the  eye,  being 
nearly  parallel  to  the  reflected  portion  of  the  great  oblique.  It  arises  in 
the  lachrymal  fossa,  passes  outwards,  and  terminates  in  the  sclerotic, 
between  the  external  and  inferior  recti  muscles. 

It  is  an  antagonist  of  the  great  oblique,  pivoting  the  eye  in  a  contrary 
direction. 

It  is  to  be  noted  that  the  double  rotatory  movement  executed  by  the 
oblique  muscles  is  altogether  involuntary,  and  that  it  is  constantly  produced 
when  the  animal  inclines  its  head  to  one  side :  doubtless  to  maintain  the 
visual  axis  always  in  the  identical  relations  with  the  same  point  of  the 
retina.  This  movement  is  well  seen  in  Man  when  the  head  is  brought 
round  to  either  shoulder :  the  eye  then  pivots  in  the  orbit  in  an  inverse 
direction  to  that  to  which  the  head  inclines,  so  that  a  mark  placed  at  the 
upper  part  of  the  iris  when  the  head  is  straight  would  occupy  the  same 
position  after  the  lateral  movement.  Simultaneous  in  both  eyes,  this 
pivoting  is  executed  by  certain  muscles  in  each  ;  the  great  oblique  for  one, 
the  small  oblique  for  the  other,  according  to  the  direction  in  which  the 
head  is  turned. 

(A  third,  or  middle  oblique  muscle,  has  been  mentioned  by  the  late 
Professor  Strangeways,  of  the  Edinburgh  Veterinary  School,  as  some- 
times, if  not  always,  found  between  the  superior  and  inferior  oblique 
muscles.  It  has  been  described  as  arising  by  a  fine  tendon  from  a  small 
depression  in  the  upper  part  of  the  orbital  process  of  the  frontal  bone, 
between  the  origin  of  the  inferior  oblique  and  the  pulley  of  the  superior 
oblique  muscle.  This  tendon  is  succeeded  by  a  fusiform  fleshy  mass,  about 
three  lines  in  diameter  and  an  inch  long,  imbedded  in  adipose  tissue ; 
it  passes  obliquely  upwards  and  outwards  on  the  external  face  of  the 
rectus  muscle,  and  terminates  in  a  thin  flat  tendon  which  accompanies  the 
upper  belly  of  the  superior  oblique  for  a  short  distance,  and  becomes  con- 
founded with  the  tendon  of  that  muscle  as  it  runs  beneath  the  superior  rectus. 
It  is  supposed  to  be  an  accessory  of  the  superior  oblique,  and  to  regulate 
and  facilitate  the  gliding  of  that  muscle  through  the  acute  angle  formed  by 
its  pulley.) 

PEOTECTIVE    ORGANS    OF    THE    EYE. 

1.  The  Eyelids.      (Figs.  383,  391.) 

The  surface  of  the  eye  is  covered  and  protected  in  front,  by  two  movable 
membranous  curtains— the  eyelids  (palpebrce)  :  one  superior,  the  other  inferior. 

Attached  to  the  circumference  of  the  orbit  by  their  external  border,  the 
eyelids  have  a  convex  external  face  formed  by  the  skin,  and  a  concave 
internal  face,  moulded  on  the  anterior  surface  of  the  eye,  and  lined  by  the 
conjunctiva  which  is  reflected  above  and  below  on  the  eyeball :  the  duplica- 
tures  constituting  the  superior  and  the  inferior  conjunctival  (or  palpebral) 
sinuses. 

Each  lid  has  also  a  free  border  opposed  to  that  of  its  fellow,  with  which 
it  unites  at  an  angle  by  its  extremities,  so  as  to  form  two  commissures  (or 
canthi).  This  border  is  slightly  bevelled  on  the  inner  side,  and  shows  a 
series  of  small  openings— the  excretory  orifices  of  the  Meibomian  glands ;  as 


THE  ACCESSORY  ORGANS  OF  VISION  831 

well  as  a  row  of  erect  hairs,  the  eyelashes :  these  will  be  described 
presently. 

When  the  two  lids  are  closed  by  the  approximation  of  their  free  borders, 
they  completely  cover  the  eye,  and  form  a  narrow  fissure  comparable  to  a 
closed  button-hole.  When  they  are  separated,  they  circumscribe  an  oval 
space  (Jissura  palpebrarum),  whose  greater  axis  is  directed  obliquely  down- 
wards, forwards,  and  inwards.  The  upper  lip  or  contour  of  this  space, 
formed  by  the  free  margin  of  the  superior  eyelid,  is  always  more  curved 
than  the  lower.  The  superior  commissure  (or  canthus)  has  also  been  named 
the  temporal  angle  of  the  eye.  Tlie  7iasal  angle,  constituted  by  the  inferior 
commissure,  is  always  rounder  than  the  other;  it  lodges  the  lachrymal 
caruncle  (in  the  laclius  lachrymalis). 

Structure  of  the  Eyelids. — A  fibrous  plate,  terminated,  towards  the 
free  border  of  the  lid,  by  a  small  tendinous  arch  named  the  tarsus;  a 
sphincter 'muscle,  the  orbicularis  palpebrce,  in  contact  with  the  fibrous  mem- 
brane ;  the  levator  palpebrce,  a  muscle  partly  lodged  in  the  ocular  sheath, 
and  terminated  anteriorly  by  a  very  thin  and  wide  expansion  placed  beneath 
the  superior  fibrous  plate ;  a  cutaneous  envelope  in  two  parts,  containing 
the  above  :  an  external,  the  skin  ;  and  an  internal  of  mucous  membrane,  the 
conjunctiva,  joining  at  the  free  border  of  the  lid ;— these  are  the  elements 
which  enter  into  the  composition  of  the  protective  coverings  of  the  eye. 

1.  Fibrous  Membrane. —  Usually  thicker  in  the  lower  than  the 
upper  lid,  this  membrane  is  attached,  by  its  adherent  border,  to  the  rim  of 
the  orbit,  where  it  is  continuous  with  the  periosteum  and  the  fibrous  wall  of 
the  ocular  sheath.     Its  free  border  is  margined  by  the  tarsus. 

2.  Tarsus. — This  is  a  fibrous  lamella  that  forms  a  solid  frame  for  the 
free  border  of  the  lid  :  it  is  elongated,  narrow  at  its  extremities,  thin  at  its 
fixed  border,  w-here  it  is  confounded  with  the  fibrous  membrane,  and  chan- 
neled on  its  inner  face  by  several  transverse  parallel  grooves  which  lodge 
the  Meibomian  glands.  This  small  fibrous  arc  regulates  the  contraction  of 
the  orbicularis  muscle,  and  prevents  the  lid  being  drawn  into  wrinkles  ;  by 
the  rigidity  it  bestows  on  the  eyelids,  it  allows  these  to  meet,  border  to 
border,  without  puckering,  when  that  muscle  is  in  action. 

3.  Orbicular  Muscle  of  the  Eyelids  (musculus  ciliaris). — This  is  a 
wide  thin  sphincter  common  to  the  two  lids,  aj^plied  to  the  fibrous  mem- 
brane and  the  bone  forming  the  rim  of  the  orbit.  Its  external  face  is 
covered  by  the  skin,  to  which  it  closely  adheres.  A  small  tendon  that 
passes  to  the  lachi-ymal  tubercle  of  the  nasal  angle  of  the  eye,  is  generally 
considered  as  the  origin  of  the  fibres  of  this  muscle,  the  majority  of  which, 
directed  upwards,  are  disposed  in  a  circular  manner  in  the  substance  of 
the  upper  lid ;  while  the  others  go  to  the  lower  lid,  both  joining  at  the 
temporal  angle  of  the  eye. 

The  contraction  of  this  muscle  causes  the  occlusion  of  the  palpebral  open- 
ing. (It  is  a  prominent  agent  in  defending  the  eye  from  external  injury.) 
We  may  regard  as  an  appendage  of  the  orbicularis,  a  little  short,  flat  fascicu- 
lus, usually  designated  the  fronto-superciliary  muscle  from  its  attachments  (or 
.corrugator  supercilii,  from  its  function).  It  arises  from  the  outer  face  of 
the  frontal  bone,  passes  downwards  and  outwards,  and  mixes  its  fibres  with 
those  of  the  latter  muscle  at  the  superorbital  foramen,  which  it  covers,  and 
in  the  skin  of  the  eyebrow.  It  has  been  erroneously  considered  an  elevator 
of  the  upper  lid,  for  when  it  contracts,  it  only  corrugates  the  skin  of  the 
eyebrow  by  slightly  drawing  the  nasal  angle  of  the  eye  outwards ;  this  it 
does  as  well  when  the  lids  are  closed  as  when  they  are  open. 


832  TEE  APPARATUS  OF  THE  SENSES. 

4.  Elevator  Muscle  of  the  Upper  Eyelid,  or  Orbito-palpebralis 
{Levator  palpebrce). — When  the  ocular  sphincter  ceases  to  contract,  the 
lower  eyelid  drooi)S  from  its  own  weight ;  the  upper  lid,  however,  requires 
some  special  muscular  agency  to  raise  it,  and  this  it  finds  in  the  levator. 
This  is  a  very  thin,  narrow,  fleshy-band,  lodged  in  the  ocular  sheath  with 
the  other  muscles  of  the  eyeball,  and  is  related  to  the  superior  rectus,  whose 
course  it  follows.  On  reaching  the  lachrymal  gland,  it  expands  into  a  wide 
aponeurotic  membrane  that  passes  between  the  conjunctiva  and  the  fibrous 
plate  of  the  eyelid,  and  terminates  on  the  tarsus. 

It  will  be  seen  that  this  muscle  is  inflected  on  the  eyeball  in  a  pulley- 
like manner,  and  it  is  owing  to  this  disposition  that  it  has  the  power  of 
raising  the  lid.  If  the  eyeball  were  not  present,  the  muscle  would  draw  the 
free  margin  of  the  lid  towards  the  back  of  the  orbit,  instead  of  elevating  it. 

5.  Integuments  of  the  Eyelids. — The  difierent  layers  enumerated  are 
comprised  between  two  tegumentary  folds,  the  skin  and  conjunctiva,  which 
are  continuous  at  the  border  of  the  eyelids.  We  will  examine  these,  with 
their  appendages — the  eyelashes  and  Meibomian  glands. 

a.  Skin. — Intimately  adhering,  by  its  inner  face,  to  the  orbicularis 
muscle,  this  membrane  is  thin  (smooth),  and  covered  with  numerous  fine 
short  hairs.  In  the  foetus,  it  shows  at  the  orbital  arch,  when  the  skin 
everywhere  else  is  nude,  a  well-marked  semicircle  of  hairs— ^the  eyebrow. 
Fat  is  never  found  beneath  it. 

b.  Conjunctiva. — The  conjunctiva,  as  its  name  indicates,  joins  the  eyelids 
to  the  eyeball.  Very  fine  and  highly  vascular,  this  mucous  membrane  is 
a  continuation  of  the  skin  at  the  border  of  the  lids,  lines  the  inner  face  of 
each  of  them,  envelops  the  anterior  portion  of  the  membrana  nictitans  in  a 
particular  fold,  covers  the  caruncula  lachrymalis,  and  enters  the  puncta ; 
it  is  then  reflected,  at  the  adherent  border  of  the  eyelids,  on  to  the  eyeball, 
extending  over  the  sclerotic  and  terminal  aponeurotic  expansion  of  the  recti 
muscles.  On  arriving  at  the  margin  of  the  cornea,  it  is  impossible  to  trace 
it  further ;  though  it  is  represented  by  the  thin  layer  of  pavement  epithelium 
already  described.  At  the  surface  of  the  lachrymal  caruncle,  it  shows 
some  very  fine  hair  bulbs.  It  possesses  some  i)apilla3  (on  the  palpebral 
portion  only,  the  ocular  reflection  being  thinner,  and  having  none  of  these 
nervous  processes),  and  tubular  and  aggregate  glands,  as  well  as  closed 
follicles.  We  have  found  large  numbers  of  the  latter,  whose  volume  was 
considerable ;  they  form  a  corona  around  the  cornea. 

The  nerves  of  the  conjunctiva  terminate  by  small  oval  enlargements, 
the  corpuscles  of  Krause. 

(The  ocular  portion  has  generally  very  few  blood-vessels  visible  in  health ; 
when  inflamed  it  becomes  intensely  red  and  vascular.) 

c.  Eyelashes. — These  are  two  rows  of  hairs  (cilia)  implanted  in  the  free 
border  of  the  lids,  and  destined  to  prevent  the  entrance  of  dust  and  small 
particles  of  foreign  matter  into  the  eye.  They  are  much  longer,  and  more 
abundant  and  stronger,  in  the  upper  than  the  lower  lid,  their  presence  there 
being  more  necessary,  as  extraneous  particles  are  most  likely  to  enter  the  eye 
when  falling.  But  if  the  eyelashes  of  the  lower  lid  are  few  and  rudimentary, 
this  is  compensated  for  by  the  presence  on  its  surface  of  some  long  bristly 
hairs,  scattered  here  and  there,  and  exactly  like  the  tentacula  of  the  lij)s. 

Like  all  hairs,  without  exception,  the  eyelashes  are  flanked  at  their 
base  by  two  or  three  small  sebaceous  glands,  whose  duct  opens  into  their 
foUicle. 

d.  Meibomian  glands. — These  are  little  masses,  analogous  to  sebaceous 


THE  ACCESSORY  ORGANS  OF  VISION.  833 

glands,  Ypticli  open  alternately  into  a  common,  very  long  excretory  canal. 
They  arc  lodged  in  the  transverse  grooves  observed  on  the  inner  face  of  the 
tarsal  ligaments.  The  unctuous  matter  they  secrete  is  thrown  out  on  the 
free  border  of  the  lids,  and  enables  these  to  retain  the  tears  more  easily 
within  the  ocular  cavity.  In  sick  animals,  this  secretion  accumulates  at  the 
canthi  and  base  of  the  lids.  (Each  gland  consists  of  a  central  tube,  with  a 
number  of  openings  round  its  sides  leading  to  short  cfecal  dilatations.  The 
secretion  also  facilitates  the  movements  of  the  lids.) 

6.  Vessels  and  Nekves  of  the  Eyelids. — These  membranous  curtains 
receive  their  blood,  for  the  most  part,  by  the  supra-orbital  and  lachrymal 
arteries,  and  the  orbital  branch  of  the  superior  dental  artery.  The  terminal 
extremities  of  the  three  sensitive  nerves  of  the  eye,  formed  by  the  ophthalmic 
branch  of  the  fifth  pair  and  the  orbital  filaments  of  the  superior  maxillary 
branch,  ramify  in  them.  The  anterior  auricular  nerve  endows  the  orbicularis 
muscle  with  contractility.  The  motor  filaments  of  the  levator  palpebr^  are 
derived  from  the  third  pair. 

2.  Menibrana  Niditans. 

"  This  organ,  which  is  also  named  the  third  eyelid,  winhing  eyelid,  etc.,  is 
placed  at  the  great  (inner)  angle  of  the  eye,  whence  it  extends  over  the 
eyeball  to  relieve  it  from  foreign  bodies  which  may  fall  upon  it.  It  has  for 
its  framework  a  fibro-cartilage — elastic — irregular  in  shape,  thick  and  nearly 
prismatic  at  its  base,  and  thin  anteriorly  where  it  is  covered  by  the  conjunc- 
tiva ;  it  is  continued,  behind,  by  a  strong  adipose  cushion,  which  is  insinuated 
between  all  the  muscles  of  the  eye,  and  to  which  it  is  loosely  attached.  No 
muscle  directly  concurs  in  the  movements  of  this  body :  they  are  entirely 
mechanical.  When  the  eye  is  in  its  usual  position,  there  is  only  per- 
ceived the  fold  of  conjunctiva  that  terminates  it  in  front ;  the  remainder  is 
concealed  in  the  fibrous  case  of  the  eye.  When,  however,  the  latter  is 
withdrawn  into  the  orbit  by  the  contraction  of  its  recti  muscles,  the  globe 
compresses  the  fatty  cushion  belonging  to  the  cartilage ;  this  cushion, 
pressing  outwards,  pushes  the  membrana  before  it,  and  the  latter  then  entirely 
conceals  the  whole  front  of  the  globe.  This  movement  is  instantaneous, 
but  it  may  be  momentarily  fixed  by  pressing  gently  on  the  eye  when  the 
animal  retracts  it  within  the  orbital  cavity. 

"  The  use  of  the  membrana  is,  as  will  be  seen  from  the  above,  to  main- 
tain the  healthy  condition  of  the  eye,  by  removing  any  matters  that  have 
escaped  the  eyelids;  and  what  clearly  demonstrates  this  function,  is  the 
inverse  relation  that  always  exists  between  the  development  of  this  body, 
and  the  facility  with  which  animals  can  rub  their  eyes  with  their  anterior 
limbs.  So  it  is  that,  with  the  Horse  and  Ox,  whose  thoracic  member  cannot 
be  applied  to  this  purpose,  the  membrana  is  very  developed ;  and  in  the  Dog, 
which  may  use  its  paw  to  some  extent  when  it  requires  to  brush  its  eye,  it 
is  smaller  ;  in  the  Cat  it  is  still  less ;  while  in  the  Monkey  and  in  Mankind, 
whose  hands  are  perfect,  it  is  rudimentary.  In  tetanus,  the  membrana 
nictitans  often  remains  permanently  over  the  eye,  in  consequence  of  the 
continued  contraction  of  the  recti  muscles." — F  Lecoq. 

(Towards  the  middle  of  the  outer  face  of  the  membrana  is  a  small 
yellowish-red  gland,  the  gland  of  Harder,  covered  by  a  strong  fibrous 
membrane,  and  surrounded  by  adipose  tissue ;  it  secretes  a  thick  unctuous 
matter,  which  escapes  by  two  or  three  small  apertures  on  the  inner  face  of  the 
membrana.) 


834  TEE  APPARATUS  OF  THE  SENSES. 

LACHRYMAL    APPAEATUS. 

"  This  apparatus  comprises  :  1,  A  gland  which. secretes  the  tears  ;  2,  A 
series  of  canals  that  carry  the  superfluous  fluid  to  the  external  orifice  of  the 
nasal  cavities. 

"  Lachrymal  gland. — This  gland,  situated  between  the  orbital  process  and 
the  upper  part  of  the  eyeball,  from  which  it  is  separated  by  the  superior 
rectus  and  levator  palpebrae  muscles,  is  convex  on  its  upper  face,  and  concave 
inferiorly,  in  accordance  with  the  parts  it  adjoins.  But  little  developed,  it 
is  formed  of  very  small  granulations,  united  by  fine  connective  tissue  ;  from 
these  arise  minute  radicles,  whose  junction  forms  a  certain  number  of  very 
narrow  ducts  which  open  on  the  inner  face  of  the  temporal  (outer)  angle  of 
the  eyelids.     These  are  the  hjgr ophthalmic  canals. 

"  The  lachrymal  gland  secretes  the  tears  destined  to  lubrify  the  anterior 
surface  of  the  eye.  This  fluid  escapes  upon  the  organ  at  the  temporal  angle 
of  the  lids,  and  is  carried  between  them  and  the  eyeball  towards  the  nasal 
angle.  Its  secretion  is  incessant,  but  it  is  increased  by  anything  that 
irritates  the  conjunctiva,  and  its  character  may  even  change  under  the  same 
influences. 

"  The  lachrymal  gland  belongs  to  the  category  of  conglomerate  glands ; 
consequently,  it  is  analogous  to  the  salivary  glands.  (The  gland  is  maintained 
in  situ  by  a  capsule  formed  by  the  fascia  of  the  orbit.) 

"  The  hygrophthalmic  canals  have  a  thin  fibrous  membrane  for  their 
walls  ;  this  is  covered  by  cylindrical  epithelium. 

"  Caruncula  lachrymalis. — -This  name  is  given  to  a  small  round  (or  fusi- 
form) body,  frequently  entirely,  or  partially  black  (or  brown),  slightly 
uneven,  and  situated  in  the  nasal  angle  of  the  eye ;  it  is  nothing  more  than 
a  small  fold  of  conjunctiva  covering  some  agglomerated  follicles,  and 
the  bulbs  of  several  fine  hairs,  which  are  readily  seen  on  its  surface.  It 
may  be  regarded  as  designed  to  direct  the  tears  towards  the  puncta,  or  to 
separate  the  extraneous  particles  that  this  fluid  may  carry  towards  it. 

"  It  has  for  its  base  a  small  mass  of  connective  tissue,  in  the  midst  of 
which  are  some  hair-roots,  and  some  rather  large  glandules,  lined  by  an 
epithelium  charged  with  fat  granules.  Nerve-tubes  ramify  around  the  hair 
bulbs. 

"  Puncta  lachrymalia. — These  are  two  little  openings,  situated  one  in  each 
eyelid,  a  short  distance  from  the  nasal  commissure,  by  which  the  tears  pass 
from  the  oculo-palpebral  surface  into  the  lachrymal  ducts. 

"  Lachrymal  ducts. — These  are  continuations  of  the  last,  and,  like  them, 
are  very  narrow  ;  they  carry  the  tears  into  the  lachrymal  sac.  The  superior 
is  longer  than  the  inferior  duct,  and  arrives  at  the  sac  behind  it.  The 
mucous  membrane  lining  these  ducts  is  thin,  and  covered  by  a  stratified 
pavement  epithelium,  similar  to  that  of  the  conjunctiva. 

"  Lachrymal  sac. —  This  little  reservoir,  lodged  in  the  infundibulum  that 
precedes  the  lachrymal  foramen  in  the  bone  of  that  name,  receives  the  tears 
from  the  two  ducts,  and  passes  them  into  the  lachrymal  canal.  Its  mucous 
membrane  only  differs  from  that  of  the  ducts  in  being  covered  with  ciliated 
epithelium. 

"  Lachrymal  canal  (nasal  duct). — The  tears  accumulated  in  the  sac  flow 
into  this  long  duct,  which  extends  to  the  lower  aperture  of  the  nostril. 
About  one  half  of  its  course  is  in  the  osseous  canal  of  the  lachrymal  bone 
which  protects  it,  and  which  terminates  between  the  two  turbinated  bones. 
The  remainder  of  the  canal  is  beneath  the  nasal  mucous  membrane,  whence 


THE  ACCESSORY  ORGANS  OF  VISION.  835 

it  passes  to  the  inner  surface  of  the  outer  wing  of  tlie  nostril ;  tliere  it 
terminates  by  an  orifice,  sometimes  two,  that  looks  as  if  punched  out  of  the 
membrane,  towards  the  lower  commissure,  near  the  point  where  there  is  a 
line  of  demarcation  between  the  dark  colour  of  the  skin,  and  the  rosy  tint 
of  the  mucous  lining. 

"  This  aperture  constitutes  the  '  nasal  outlet '  (egout  nasal). 

"  The  epithelium  of  the  membrane  lining  the  canal  is  Ciliated  in  its 
bony,  stratified  in  its  nasal,  portion.  On  the  surface  of  the  membrane  are  to 
be  seen  the  openings  of  the  secretory  ducts  of  some  conglomerate  glands, 
which  are  lodged  in  the  walls  of  the  canal.  Throughout  its  extent,  the 
canal  is  lined  by  a  continuation  of  the  mucous  membrane  of  the  lachrymal 
sac.  In  Solipeds,  this  canal  opens  on  the  cutaneous  surface  at  the  entrance 
of  the  nostrils ;  and  it  therefore  happens  that  in  these  animals  the  con- 
junctiva, with  its  dependencies,  forms  a  particular  mucous  membrane,  really 
apart  from  the  great  gastro-pulmonary  membrane. 

"  In  the  Ass  and  Mule,  the  orifice  of  the  lachrymal  canal  is  situated  at 
the  inner  face  of  the  outer  wing  of  the  nostril,  and  not  near  the  inferior 
commissure,  as  in  the  Horse." — F.  Lecoq :  '  Exterieur  du  Cheval,'  etc. 

(Sometimes  this  outlet  is  double.  The  lachrymal  secretion  is  not  only 
useful  in  facilitating  the  movements  of  the  eyelids  over  the  eyeball,  but  it 
washes  away  dust  and  hurtful  matter  from  off  the  surface  of  the  cornea, 
keeping  the  latter  clean,  moist,  and  healthy.) 

DIFFERENTIAL    CHARACTERS   IN   THE   VISUAL   APPARATUS   IN   OTHER   THAN   SOLIPED 

ANIMALS. 

Essential  Organ  of  Vision.— la  the  Ox,  the  eyeball  resembles  in  shape  that  of  the 
Horse  ;  but  in  small  animals,  particularly  the  Dog,  it  is  much  more  spherical.  In  Birds, 
it  is  very  convex  in  front ;  its  largest  diameter  is  the  anteroposterior. 

Sclerotic. — This  is  the  same  in  all  the  domesticated  quadrupeds.  In  Birds,  however,  it 
has  some  curious  features.  Posteriorly,  it  has  for  base  a  cartilaginous  layer,  covered  on 
both  sides  by  tibrous  tissue ;  this  layer  frequently  ossifies  around  the  optic  nerve,  where 
it  forms  the  posterior  scler(jtic  ring.  Around  the  cornea,  there  is  the  anterior  sclerotic 
ring,  composed  of  small  bony  imbricated  scales,  capable  of  moving  on  each  other,  and 
modifying  the  shape  of  the  globe  of  the  eye. 

Cornea. — In  the  Dog  and  Cat,  the  structure  of  the  cornea  is  similar  to  that  of  the 
Horse.  (Kolliker  states  that  he  observed  lymphatics  in  the  cornea  of  a  young  Cat.)  In 
the  Ox,  Sheep,  and  Fig,  there  are  two  limitary  membranes  ;  one  beneath  the  epithelium 
of  the  anterior  face.     In  Birds,  this  limitary  membrane  is  thickest  in  front. 

Choroid. — In  mammifers,  there  are  some  slight  differences  in  the  coloration  of  the 
tapetum.  Thus, in  the  Ox.  it  is  g<ilden  green,  which  becomes  blue  at  the  circumference; 
in  the  Sheep,  it  is  a  pale  golden  green ;  a  golden  yellow  in  the  Cat ;  and  white,  bordered 
with  blue,  in  the  Dog.  (It  is  absent  in  the  Pig.)  In  Bird>!,  it  is  imiformly  black  ;  this 
membrane  has  also  a  network  of  non-striped  muscular  fibres,  and,  in  addition, ''  Cramptoii's 
muscle,  which  arises  from  tlie  inner  face  of  the  osseous  ring,  and  is  inserted  into  tiie 
cornea." — Leydig.  (According  to  Hassenstein,  in  rapacious  animals  there  is,  behind  the 
tapetum,  a  layer  of  corpuscles  composed  of  lime  salts ;  to  this  is  owing  the  brilliancy  of 
their  eyes  in  the  dark.) 

Iris. — In  all  animals  the  iris  is  muscular.  In  mammifers,  the  contractile  fibres  are 
non-striped ;  in  Birds,  they  are  striped.  (In  the  Ox,  its  anterior  face  has  a  brighter 
colour  than  in  the  Horse.  In  the  Sheep  it  is  a  brownish -yellow ;  in  the  Goat  blue.)  In 
the  Dog  its  colour  is  a  more  or  less  bright  golden-yellow  ;  in  the  adult  Cat  green  ;  and 
in  young  ftnimuls  a  bright  blue.  The  pupil  is  elliptical  in  the  Ox,  as  in  Solipeds  (in 
the  Sheep  and  Goat  it  is  more  elongated) ;  in  the  Dog  it  is  circular,  and,  when  very 
much  dilated,  it  is  the  same  in  the  Cat ;  but,  when  contracted,  it  becomes  elliptical 
vertically,  and  may  be  so  narrow  as  to  represent  nothing  more  than  a  thin  perpendicular 
slit,     (In  the  Pig  it  is  round.) 

There  are  no  differences  worthy  of  note  in  the  other  parts  of  the  eye. 

Accessory  Organs  of  the  Visual  Apparatus. — The  motor  organs  are  nearly  the 
same  in  all  the  other  animals. 


836  THE  APPARATUS  OF  THE  SENSES. 

(The  posterior  rectus,  or  retractor  muscle,  is  most  developed  in  Ruminants,  which, 
during  their  whole  time  of  feeding,  have  the  head  in  a  dependent  position.  In  most  of 
the  Carnivora,  instead  of  this  muscle  forming  a  complete  hollow  cone,  as  in  Ruminants, 
there  are  four  distinct  strips,  almost  resembling  a  second  set  of  recti  muscles,  but  deep- 
seated,  and  inserted  into  the  posterior,  instead  of  the  anterior,  portion  of  the  globe.) 

Muscles. — Birds  have  only  six  muscles :  four  recti,  and  two  oblique.  The  latter 
arise  from  the  anterior  wall  of  the  orbit ;  consequently,  the  great  oblique  does  not  pass . 
through  a  pulley. 

Eyelids. — The  disposition  of  these  is  the  same  in  all  mammifers.  In  Birds,  the  lower 
lid  is  the  largest,  and  is  furnished  with  a  particular  depressor  muscle ;  there  are  no 
Meibomian  glands.  There  is  a  third  eyelid,  corresponding  to  the  membrana  nictitans  of 
quadrupeds ;  it  is  sufficiently  extensive  to  cover  the  entire  front  of  the  eye. 

Glands. — In  Buminants,  the  Pig,  and  in  Birds,  there  is  found,  annexed  to  the  mem- 
brana nictitans,  Harder's  gland— a,  conglomerate  gland,  with  adipose  epithelium  in 
mammifers,  and  cylindrical  and  granular  in  Birds.  It  secretes  a  thick  white  matter, 
which  is  thrown  out  on  the  membrana  by  one  or  two  orifices.  Its  use  is,  doubtless,  to 
favour  the  movements  of  that  organ  over  the  surface  of  the  eye,  as  well  as  those  of  the 
eyelids.  (In  the  Ox,  this  gland  and  its  ducts  are  large.  The  lachrymal  gland  is  also 
voluminous  and  its  nasal  opening  is  situated  higher  in  the  nostril  than  with  the  Horse. 
In  the  Sheep,  there  are  found,  near  the  lachrymal  fossa,  several  adipose  follicles  which 
do  not  properly  belong  to  this  apparatus,  and  which  secrete  a  consistent,  unctuous, 
yellow  matter.  In  the  Pig,  the  lachrymal  ducts  are  separated,  by  a  bony  partition, 
into  two  sets,  as  far  as  the  lachrymal  sac.) 

(Orbital  cavity. — In  Buminants,  the  frontal  and  superior  extremity  of  the  maxillary 
bones  contribute  largely  to  the  formation  of  this  cavity.  In  the  Pig,  the  upper  part  of 
the  orbit  is  not  completed  by  the  orbital  process  of  the  frontal  bone,  which  is  short ;  it  is 
continued  by  a  ligament.  In  the  Dog,  the  superior  portion  of  the  cavity  is  entirely 
formed  by  a  ligament,  which  replaces  the  orbital  arch ;  in  the  Cat,  this  ligament  is 
smaller,  and  the  orbital  process  of  the  zygomatic  concurs  with  that  of  the  frontal  bone 
to  form  the  upper  wall.) 

COMPAEISON  OF  THE  VISUAL  APPARATUS  OF  MAN  WITH  THAT  OF  ANIMALS. 

Essential  Organ  of  Vision. — The  eyeball  of  Man  is  almost  spherical,  as  in  the 
Carnivora.  The  sclerotic  does  not  differ  much.  The  cornea  has  two  limitary  membranes, 
and  is  much  less  elliptical  than  in  Solipeds.  The  choroid  has  the  same  zones  as  in 
animals ;  it  is  uniformly  brown.  The  ciliary  processes,  seventy  to  eighty  in  number,  are 
a  little  longer  than  in  the  Horse,  and  do  not  exceed,  in  front,  the  ciliary  ligament,  to  the 
inner  face  of  which  they  adhere  throughout  their  external  border.  The  pupillary  opening 
of  the  iris  is  always  round.  The  retina  is  the  same  in  structure  as  already  described. 
A  little  above  the  optic  papilla,  there  is  a  circular  or  oval  patcii,  about  ^  of  an  inch  in 
diameter,  in  the  centre  of  which  is  a  transparent  spot ;  this  is  the  yellow  spot  (macula 
lutea),  yiith  the  fossa  centralis  of  the  retina  (fovea  centralis,  foramen  of  Soemmering). 

At  this  patch,  the  tissue  of  the  retina  is  slightly  modified,  especially  at  the  fossa ; 
there  are  only  cones  in  the  columnar  layer,  and  all  the  other  layers  appear  to  be  con- 
founded into  one  granular  mass.  (This  spot  only  exists  in  animals  which  have  the  axes 
of  the  eyeballs  parallel  with  each  other,  as  in  Man,  the  Quadrumana,  and  some  saurian 
reptiles.) 

There  is  nothing  particular  in  the  aqueous  humour,  lens,  or  vitreous  humour. 

Accessory  Organs  op  the  Visual  Apparatus. — The  orbital  cavity  of  Man  is 
entirely  inclosed  by  bony  walls,  and  there  is  no  fibrous  sheath.  (A  fold  of  the  orbital 
fascia  has  been  described  as  separating  the  eye  from  its  surrounding  adipose  tissue,  and 
which,  like  a  "tunica  vaginalis,"  enables  the  globe  to  roll  with  rapidity  and  precision.) 
The  muscles  are  six  in  number — four  recti,  and  two  oblique :  the  great  oblique  is  the 
same  as  in  animals.  Only  the  rudiment  of  a  caruncnhi  lachrymalis  is  present.  The 
nasal  duct  opens  at  some  distance  up  on  the  surface  of  the  inferior  meatus. 


THE  INTERNAL  EAR  OR  LABYRINTH.  837 

CHAPTER  V. 

AUDITORY   APPARATUS. 

The  sense  of  bearing,  destined  for  the  perception  of  sounds  produced  by  the 
vibration  of  bodies,  has  for  essential  agents  the  auditory  or  eighth  pair  of 
encephalic  nerves,  whose  terminal  fibrillfe  ramify  in  the  membranous  walls 
of  a  system  of  cavities  forming  the  internal  ear  ;  these  cavities  are  excavated  in 
the  substance  of  the  petrous  bone,  and  communicate,  externally,  by  means  of 
two  other  systems  of  diverticuli,  which  constitute  the  middle  and  external  ear. 

Article  I. — Internal  Ear,  or  Labyrinth, 

(Preparation. — The  dissection  of  this  part,  from  its  minuteness  and  complexity,  as 
well  as  the  density  of  the  bone  surrounding  it,  cannot  be  made  with  advantage  by  the 
student.  He  is,  tlierefore,  recommended  to  study  it  in  special  preparations,  and  in  the 
following  description.) 

The  cavities  which,  together,  compose  this  part  of  the  auditory  apparatus, 
being  entirely  channeled  within  the  petrous  portion  of  the  temporal  bone, 
have  their  w^alls,  forming  the  osseous  labyrinth,  constituted  by  that  bone. 
They  contain  the  soft  parts,  named  the  membranous  labyrinth,  and  fluids 
(endolymph). 

the  osseous  labyrinth. 
This  is  composed  of  three  portions  :  the  vestibule,  semicircular  canals,  and 

1.  TJie  Vestibule. 

This  is  a  small,  somewhat  oval  cavity,  in  the  centre  of  the  bone,  and  out- 
side the  perforated  bony  plate  that  forms  the  bottom  of  the  internal  auditory 
hiatus.  It  is  a  real  vestibule,  with  regard  to  the  other  parts  of  the  labyrinth, 
which  all  open  into  it. 

On  its  external  tvall  is  the  fenestra  oralis  (fenestra  vestibuli),  an  opening 
closed  by  the  stapes.  The  imier  shows  the  foramina  through  which  the 
filaments  of  the  vestibular  branch  of  the  acoustic  nerve  pass.  Beloiv,  and  in 
front,  is  a  large  orifice,  the  commencement  of  the  scala  cochleae ;  above,  are 
five  little  apertures,  the  openings  of  the  semicircular  canals. 

2.   The  Semicircular  Canals. 

Three  in  number,  and  very  narrow,  these  canals  owe  their  name  to  their 
form.  They  are  placed  above  the  vestibule,  like  three  semicircular  arches 
united  in  a  triangular  manner  at  their  base,  and  are  distinguished  as  superior 
or  anterior,  posterior,  and  external.  The  first  two  open  together,  by  their 
adjacent  extremities,  into  the  vestibule  ;  consequently,  there  are  only  five 
orifices  of  the  semicircular  canals  in  this  cavity  ;  in  addition,  the  adjoining 
openings  of  the  posterior  and  external  canals  are  so  close  to  each  other, 
that  they  appear  to  be  sometimes  united  at  the  bottom  of  a  short  common 
canal. 

3.  TJie  Cochlea. 

Situated  external  to,  and  below  the  vestibule,  at  the  inner  wall  of  the 
cavity  of  the  tympanum,  the  snail-shell  or  cochlea  is  well  named,  as  it  presents 
exactly  the  form  of  certain  molluscs'  shells.     It  is  a  spiral  conical  canal, 

56 


838 


THE  APPABATU8  OF  THE  SENSES. 


twisting  downwards,  forwards,  and  upwards,  around  a  central  conical  axis 
(the  modiolus)  ;  so  that  its  centre  nearly  corresponds  to  the  inner  wall  of  the 

tympanum.      A    partition — the 
Fig.  392.  lamina  spiralis,   spiral   like  the 

cavity — divides  it  into  two  dis- 
tinct sections  or  scalce  :  a  supe- 
rior and  inferior ;  this  lamina  is 
attached  by  its  inner  border  to 
the  central  axis  of  the  cochlea, 
but  is  free  at  its  external  margin, 
which  does  not  quite  reach  the 
periphery  of  the  cavity.  The 
two  scalsB,  therefore,  communi- 
cate, in  the  skeleton,  by  means 
of  an  opening  (the  helico-irema) 
that  follows  the  free  border  of 
the  lamina  spiralis  throughout 

SECTION   THROUGH   ONE   OF   THE   COILS   OF   THE  its  CXtCUt. 

COCHLEA.  The  inferior  scale   (or  scala 

ST,  Scala  tympani ;  sv,  Scala  vestibuli ;  CC,  Canalis  festibuU)   enters     the    vestibule ; 

cochleae  ;membmnaofReissEei-.-&  to /sft  Lamina  the  commencement   of  tho  supe- 

spiralis    membranacea ;    lis,    Lirabus   lamina;    spi-  .               -                     -                       .-c^ . 

ralis ;    ss.    Sulcus    spiralis ;   gs.    Ganglion    spirale  *'*^*'    scale,    or    Scala    tympani,    IS 

situated   on  nc,  the  nervous  cochlearis   indicated  formed    by  the   fenestra  rotunda 

by  the  black  line;  Iso,  Lamina  spiralis  ossea;  I,  (^fenestra   COcMeoe),  which  brings 

Membrana  tectoria;    6,   Membrana  basilaris;  Co,  (^    ^^^0   communication  with  the 

Organ   of    Corti ;    Isn,  Lisramentum    spirale;    Cc,  •■i-,-,                 •.^        .  .i 

Cells  of  Claudius.-l,  Rod  of  Corti  of  the  first  middle  ear,  Without  the  presence 

order ;  2,  Rod  of  Corti  of  the  second  order.  of  a   membrane  exactly   closing 

that  aperture. 

THE    MEMBRANOUS    LABYRINTH. 

The  membranous  labyrinth  comprises  three  parts,  corresponding  to  the 
three  cavities  of  the  osseous  labyrinth :  1,  The  vestibule ;  2,  The  semi- 
circular canals ;  3,  The  cochlea. 

Fig.  393.  1,  The  Membranous  Vestibule. 

This  is  composed  of  two  sacs  with  thin, 
soft  walls,  lodged  in  the  osseous  labyrinth ; 
the  superior  is  the  largest,  is  oval-shaped, 

1,  Modiolus;  2,  Infundibulum  in  which  the  mo- 
diolus terminates  ;  3,  3,  Cochlear  nerve,  send- 
ing its  filaments  through  the  centre  of  the 
modiolus ;  4,  4,  Scala  tympani  of  the  first 
turn  of  the  cochlea ;  5,  5,  Scala  vestibuli 
of  the  first  turn  ;  the  septum  between  4  and 
5  is  the  lamina  spiralis ;  a  filament  of  the 
cochlear  nerve  is  seen  passing  between  the 
layers  of  the  lamina  to  be  distributed  in  the 
membrane  investing  the  lamina ;  8,  Loops 
formed  by  the  filaments  of  the  cochlear 
nerve  on  the  lamina  spiralis ;  9,  9,  Scala  tympani  of  the  second  turn  of  the  cochlea ; 
10,  10,  Scala  vestibuli  of  the  second  turn  ;  the  septum  is  the  lamina  spiralis  ;  11, 
The  remaining  half  turn  of  the  scala  vestibuli ;  the  dome  above  is  the  cupola,  the  line 
passing  through  it  leads  to  the  remaining  half  turn  of  the  scala  tympani.  The 
osseous  lamina  forming  the  floor  of  the  scala  vestibuli  curves  spirally  round  to  con- 
stitute the  infundibulum  (2) ;  14,  The  helicotrema  through  which  a  bristle  is  passed ; 
its  lower  extremity  issues  from  the  scala  tympani  of  the  middle  turn  of  the  cochlea. 


SECTION  OF  THE  COCHLEA  PARALLEL  TO 
ITS  AXIS,  THROUGH  THE  CENTRE  OF 
THE   MODIOLUS. 


THE  INTERNAL  EAR  OB  LABYRINTH.  839 

and  is  named  the  utriculus  ;  it  communicates  with  the  semicircular  canals,  of 
which  it  is  a  confluent.  The  inferior  is  smaller,  spherical  in  shape,  and 
forms  the  sacculiis  ;  it  ap2)ears  to  be  perfectly  closed,  though  in  contact  with 
the  utriculus. 

The  membranous  vestibule  is  composed  of  two  distinct  layers :  an 
external,  cellular,  and  an  internal,  epithelial,  resting  on  an  amorphous 
membrane.  At  the  expansion  of  the  nervous  filaments,  the  latter  is  absent, 
and  is  replaced  by  a  white  calcareous  substance  (minute  crystalline  particles 
of  carbonate  and  phosphate  of  lime)  which,  in  the  domesticated  animals, 
appears  as  a  powder,  and  is  named  the  calcareous  powder  of  the  vestibule,  ear 
dust,  or  otoconites  (otoliths). 

(Some  authorities  give  four  layers :  an  external  or  serous,  derived  from 
the  lining  membrane  of  the  labyrinth  ;  a  vascular,  with  multitudes  of  vessels ; 
a  nervous,  formed  by  the  expansion  of  the  filaments  of  the  vestibular  nerve ; 
and  an  internal  serous  membrane,  which  secretes  the  limpid  fluid  contained 
in  its  interior.  Spots  of  pigment  are  constantly  found  in  the  tissue  of  the 
membranous  labyrinth.) 

2.  The  Membranous  Semicircular  Canals. 

These  are  three  thin  tubes,  which  correspond  exactly  with,  though  they  are 
of  smaller  diameter  than,  the  osseous  semicircular  canals  ;  they  open  into  the 
utriculus  in  the  same  manner  as  the  latter  do  into  the  bony  vestibule.  Each 
has  one  of  its  two  extremities  dilated  into  a  sac  or  ampulla  (sinus-ampuUaceus) ; 
for  the  two  superior  and  external  canals  it  is  the  anterior  extremity,  and 
for  the  posterior  canal  the  outer  extremity. 

In  structure  they  resemble  the  vestibular  sacs. 

3.  The  Membranous  Cochlea. 

The  membranous  cochlea  is  represented  by  two  membranes,  which 
complete  the  lamina  spiralis ;  they  continue  the  osseous  laminae  of  the 
latter,  and  are  inserted  into  the  external  wall  of  the  cochlea. 

They  give  rise  to  three  cavities,  or  scales,  in  the  interior  of  this  portion 
of  the  ear :  an  inferior,  or  tympanic  scalu ;  a  superior,  or  vestibular  scala  ; 
and  a  middle  or  auditive  scala,  in  which  the  organ  of  Corti  is  lodged.  The 
vestibular  scale  is  itself  divided  by  the  membrane  of  Reissner  into  two  canals 
— the  proper  vestibular  scala,  and  Loicenberg's,  or  the  collatei'al  scala  ;  so  that, 
in  reality,  there  are  four  cochlean  scales. 

We  do  not,  therefore,  find  in  the  cochlea,  as  in  the  other  regions  of  the 
labyi-inth,  a  system  of  membranous  cavities  included  in  osseous  cavities. 

The  structure  of  the  membranes  that  limit  the  auditive  scala  is  not 
perfectly  known,  and  is  still  disputed  by  anatomists ;  but  connective,  epi- 
thelial, and  nervous  elements  appear  to  form  their  base. 

With  regard  to  the  organ  of  Corti,  it  is  a  very  curious  and  interesting 
portion  of  the  auditory  scala,  being  formed  by  a  series  of  solid  and  elastic 
arches  resting  by  their  extremities  on  the  membrane — the  basilar — that  sepa- 
rates the  auditory  from  the  tympanic  scala,  their  convexity  being  towards 
the  superior,  or  membrane  of  Corti.  These  arches  number  about  three 
thousand  in  Man,  and  are  composed  of  two  portions  or  articles :  an  external 
and  an  internal,  united  by  a  thickening  in  the  vicinity  of  the  membrane  of 
Corti.  To  these  elastic  arches  are  added  conical  or  fusiform  cells,  whose 
nature  is  not  yet  determined. 


840  THE  APPARATUS  OF  THE  SENSES. 

FLUIDS   OF   THE    LABYRINTH. 

These  liquids  are  of  two  kinds :  one  is  contained  in  the  membranous 
labyrinth,  the  other  in  the  osseous  labyrinth. 

The  fluid  of  the  membranous  lahijrinth,  or  endo-lym2Jli  of  Breschet,  is  con- 
tained in  the  sacs  and  tubes  constituting  the  membranous  vestibule  and 
semicircular  canals.  It  is  limpid  and  fluid  like  water.  The  fluid  of  the 
osseous  labyrinth,  or  peri-lymph  of  Breschet,  fills  the  two  scalae  of  the  cochlea, 
and  bathes  the  external  surface  of  the  vestibule  and  membranous  semi- 
circular canals,  which  it  separates  from  the  corresponding  walls  of  the 
osseous  labyrinth. 

DISTRIBUTION    AND   TERMINATION    OF    THE   AUDITORY   NERVE    IN   THE    MEM- 
BRANOUS   LABYRINTH. 

This  nerve  (the  portio  mollis  of  the  seventh  pair)  divides,  as  we  have 
said,  into  two  branches :  a  cochlear  and  a  vestibular. 

The  cochlear  branch,  the  largest,  reaches  the  base  of  the  cochlea, 
where  it  breaks  up  into  a  large  number  of  fasciculi,  one  portion  of  which 
expands  over  the  first  turn  of  the  lamina  spiralis,  the  other  on  the  second, 
and  a  third  on  the  third  ;  the  latter  ramifications  penetrate  to  the  auditory 
scala,  and  terminate  above  or  below  on  the  organ  of  Corti. 

The  vestibular  branch  divides  into  three  portions,  whose  terminal  fila- 
ments ramify  in  the  wall  of  the  sacculus,  utriculus,  and  the  ampullae  at  the 
extremities  of  the  three  semicircular  canals. 

The  precise  manner  in  which  these  filaments  of  the  auditory  nerve 
terminate  is  doubtful.  (Breschet  says  they  communicate  and  form  a  series 
of  minute  arches.  Some  of  the  filaments  of  the  other  nerves  pass  into  the 
sac,  and  come  into  contact  with  the  otoconies  or  ear-dust  in  its  interior.) 

(The  membrane  of  the  labyrinth  is  supplied  with  blood-vessels  by  a 
branch  of  the  basilar  artery,  which  passes  with  the  auditory  nerve  to  the 
bottom  of  the  meatus,  and  divides  into  twigs  corresponding  with  the  nerve 
divisions  ;  its  ultimate  ramifications  terminating,  in  the  form  of  a  fine  net- 
work, on  the  membranous  labyrinth  and  the  spiral  lamina  of  the  cochlea. 
The  blood  is  returned  by  the  auditory  vein,  which  enters  the  superior 
petrosal  sinus.) 

Article  II. — Middle  Ear  or  Tympanum. 

Excavated  in  the  substance  of  the  tuberous  portion  of  the  temporal  bone, 
on  the  limit  of  the  petrous  and  mastoid  sections,  but  chiefly  in  the  latter, 
the  middle  ear  constitutes  an  irregular  cavity,  which  we  may  consider  as 
composed  of  two  icalls  and  a  circumference. 

The  external  wall  is  principally  constituted  by  the  membrane  of  the  tym- 
panum. The  internal  wall,  formed  by  the  petrous  bone,  offers  two  openings — 
the  fenestra  ovalis  and  fenestra  rotunda,  the  one  situated  behind  the  other, 
and  separated  by  a  small  eminence  named  the  promontory.  The  circumference 
is  occupied  for  nearly  the  whole  of  its  extent  by  the  mastoid  cells,  large 
open  cavities  in  the  tympanum. 

Internally,  the  tympanmn  contains  a  chain  of  small  bones  named  the 
malleus,  incus,  os  orbiculare.  and  stapes ;  these  bones  form  the  medium  of 
communication  between  the  tympanum  and  the  fenestra  ovalis — from 
one  wall  to  the  other  of  the  cavity  of  the  tympanum. 

This  cavity  is  lined  by  a  fine  mucous  membrane,  which  is  continuous  with 


THE  MIDDLE  EAR  OB  TYMPANUM. 


841 


that  lining  the  pharynx  by  means  of  a  cartilaginous  canal — the  Eustachian  tube, 
which  conveys  the  external  air  to  the  middle  ear. 

We  will  glance  briefly  at  the  anatomical  characters  of  the  parts  enu- 
merated, and  which  enter  into  the  formation  of  the  middle  ear. 

1.  Membrana  Tympani. 

ituated  on  the  external  wall  of  the  middle  ear,  which  it  separates  from 
the  bottom  of  the  auditory  canal,  this  membrane  is  oval  in  shape.  It  is 
thin,  dry,  and  capable  of  vibrating.  Its  inner  face,  inclining  inwards  and 
slightly  convex,  is  adherent  to  the  handle  of  the  malleus.  Its  external 
face  is  slightly  concave  (towards  the  meatus).  The  circumference  is  fixed 
in  a  bony  frame  named  the  tympanal  circle,  which  is  sharply  defined,  but 


EIGHT  TYMPANIC   CAVITY   OF   THE   HORSF/s   EAR ;   ANTERIOR   PLANE,    VERTICAL 
AND   TRANSVERSE   SECTION. 

A,  Auditory  canal ;  B,  Membrana  tympani ;  c,  Malleus  ;  D,  Incus  ;  E,  Os  orbiculare  ; 
F,  Stapes;  G,  Mastoid  cells;  H,  Fenestra  ovalis ;  I,  Vestibule;  J,  K,  L,  Outline  of 
the  semicircular  canals  ;  M,  Cochlea  ;  N,  Commencement  of  the  tympanic  scala. 

incomplete  at  its  upper  part,  and  enveloped  by  the  mastoid  cells,  whose 
cavities  radiate  around  this  circle. 

Although  very  thin,  this  membrane   is   composed   of  three  layers:   a 


842  THE  APPABATUS  OF  THE  SENSES. 

middle,  of  a  fibrous  (and  muscular)  character  (fibres  radiating  towards  the 
centre,  and  also  circular)  ;  an  external,  epidermic ;  and  an  internal,  the 
mucous  membrane  of  the  middle  ear.  It  has  vessels  and  nerves  in  the 
external  and  internal  layers.  (This  membrane  receives  those  vibrations  of 
the  air  which  set  in  movement  the  chain  of  bones  in  the  ear,  and  thus 
pro^xagates  them  to  the  fenestra  ovalis  and  labyrinth.) 

2.   The  Promontory,  Fenestra  Ovalis,  and  Fenestra  Rotunda. 

Placed  in  the  upper  part  of  the  tympanic  wall,  the  promontory  is  only  a 
very  small  eminence  separating  the  fenestra  rotunda  from  the  fenestra  ovalis. 
(It  is  marked  by  grooves  in  which  lie  the  branches  of  the  tympanic  nerves.) 

The  fenestra  ovalis  (fenestra  vestibuli),  situated  in  front  of  the  promontory, 
is  an  opening  whose  form  is  sufficiently  indicated  by  its  name.  It  is  the 
opening  of  communication  between  the  tympanum  and  osseous  vestibule, 
and  is  closed  by  the  base  of  the  stapes  and  the  lining  membrane  of  both 
cavities. 

The  fenestra  rotunda  (fenestra  cochlece')  is  separated  from  the  preceding 
by  the  promontory,  and,  placed  behind  this  small  projection,  it  is  closed  in 
the  fresh  state  by  a  thin  membrane  (m.  tympani  secundaria),  that  forms  a 
kind  of  diaphragm  between  the  middle  ear  and  the  tympanic  scala  of  the 
cochlea.  (The  aqueduct  of  Fallopius  is  a  canal  commencing  at  the  internal 
ear,  passing  above  the  fenestraea  and  promontory,  and  terminating  at  the 
mastoid  foramen.  It  contains  the  facial  nerve,  which  passes  through  the 
tympanic  cavity.) 

3.  The  Mastoid  Cells. 

These  cells  occupy  all  the  cii-cumference  of  the  tympanic  cavity,  except 
above.  They  are  small,  more  or  less  irregular,  and  deep  spaces,  separated 
by  thin  partitions  radiating  around  the  tympanic  circle,  and  whose  free 
margin  is  turned  towards  the  centre  of  the  cavity. 

In  several  animals,  and  particularly  the  Carnivora,  the  mastoid  cells 
form  a  special  compartment  in  the  tympanic  case,  communicating  with  the 
latter  by  a  single  opening.  (In  the  Sheej)  and  Goat,  the  mastoid  cells  and 
their  bony  septa  are  entirely  absent.) 

4.  The  Bones  of  the  Middle  Ear.     (Fig.  395.) 

Four  articulating  bones  (ossicula  auditus)  named  the  malleus,  incus,  os 
orhiculare,  and  stapes,  compose  the  bony  chain  of  the  middle  ear ;  this  chain 
extends  in  a  broken  course  from  the  external  to  the  internal  wall  of  the 
tympanum.  The  pieces  are  movable  on  each  other,  and  are  united  by 
ligaments  and  moved  by  muscles. 

1.  Malleus  (hammer). — This  is  the  longest  of  the  bones,  and  offers  a 
handle  and  a  head.  The  handle  {manuhrium)  is  placed  almost  vertical,  and 
fiirmly  fixed  to  the  inner  face  of  the  membrana  tympani.  The  head, 
directed  upwards,  has  a  diarthrodial  facet  for  articulation  with  the  incus. 
The  nech,  or  upper  part  of  the  handle,  shows  two  small  processes  for  insertion 
(processes  gracilis  and  hrevis),  the  innermost  of  which  is  very  developed. 

2.  Incus  (anvil). — This  bone  presents  a  body  or  middle  portion,  and 
two  branches.  The  body  is  channeled  externally  by  a  diarthrodial  facet 
corresponding  to  that  on  the  malleus.  Of  the  two  branches,  the  superior 
terminates  in  a  blunt  point ;  while  the  other,  inferior,  is  united  at  its 
extremitv  to  the  os  orbiculare. 


THE  MIDDLE  EAR  OR  TYMPANUM. 


843 


3.  Os  Orbiculare. — Tliis  is  a  little,  circular,  discoid  bone,  included 
between  the  inferior  branch  of  the  incus  and  stapes. 

4.  Stapes  (stirru])). — Eemarkable  for  its  shape,  which  is  exactly  that 
of  a  stirrup,  this  bone  is  placed  almost  horizontally.  Its  summit  (or  head) 
articulates  with  the  os  orbiculare ;  its  middle  imrt  is  divided  into  two 
hranches,  having  between  them  an  aperture  that  is  closed  by  the  tynij)anic 
mucous  membrane.  Its  base  is  received  into  the  fenestra  ovalis,  and  re- 
sembles that  cavity  in  shape ;  it  is  maintained  in  its  position  by  the  mucous 

Fi?.  395. 


BONES  OF  THE  MIDDI4E  EAR  OF  THE  HORSE. — From  an  Unpublished  Drawing  by  Lavocat, 
M,  Malleus  ;  1,  Handle  ;  2,  Head. — E,  Incus  ;  1,  Inferior  branch  ;  2,  Superior  branch  ; 
3,  Body. — L,  Os  orbiculare  ;   Ei,  Stapes  ;  1,  Summit ;  2,  2,  Branches  ;  3,  Base. — 
Me,  Muscle  of  the  stapes ;  o.  Bony  nucleus  in  the  terminal  tendon. 

lining  of  the  tympanum,  which  passes  over  the  stapes,  after  being  reflected 
around  the  margin  of  the  fenestra  ovalis. 

(These  bones  transmit  the  vibrations  of  the  membrana  tympani  to  the 
fluid  in  the  labyrinth.) 

5.  Ligaments  of  the  Auditory  Bones. — We  need  only  mention  the 
existence  of  these  here,  as  they  are  too  small  and  unimportant  to  merit  a 
particular  description. 

6.  Muscles  of  the  Auditory  Bones. — Four  muscles  have  been  de- 
scribed :  three  destined  to  move  the  malleus,  and  one  for  the  stapes.  But 
two  of  these  being  extremely  small,  and  their  muscular  character  doubtful 
to  many  anatomists,  we  will  only  notice  the  internal  muscle  of  the  malleus 
and  that  of  the  stapes. 

a.  Tlie  internal  muscle  of  the  malleus  (tensor  tympani,  musculus  intemus 
mallei). — This  is  a  little  elongated  fasciculus,  lodged  in  a  particular  groove 
in  the  mastoid  portion  of  the  temporal  bone,  and  arises  near  the  superior 


844  THE  AFFABATVS  OF  THE  SENSES. 

extremity  of  the  Eustachian  tube  ;  it  passes  downwards  and  backwards,  and 
terminates  by  a  tendon  which  is  reflected  outwards,  in  front  of  the  fenestra 
ovalis,  to  be  inserted  into  the  neck  of  the  malleus. 

h.  Muscle  of  the  stapes  (stapedius). — Lodged  in  an  excavation  in  the 
inner  wall  of  the  tympanum,  near  the  fenestra  vestibuli,  on  the  course  of 
the  aqufeductus  Fallopii,  this  muscle  is  remarkable  for  its  brevity,  its 
relatively  considerable  thickness,  and  its  conical  shape.  It  terminates  by  a 
small  tendon  in  front  of  the  head  of  the  stapes.  In  the  Horse,  Ox,  and 
Sheep,  a  small  bony  nucleus  is  found  in  the  tendon  (Fig.  395,  o). 

(The  tensor  tympani  retracts  the  bones  of  the  ear  inwards.  In  con- 
tracting it  draws  the  handle  of  the  malleus  towards  the  cavity  of  the 
tympanum,  and  this  brings  the  membrane  with  it ;  consequently,  the  con- 
vexity of  the  latter  is  increased  and  its  tension  is  augmented.  In  addition, 
while  the  handle  of  the  malleus  is  carried  inwards,  its  head  is  turned 
outwards  by  a  pivoting  motion,  and  this  pulls  the  body  of  the  incus  also, 
the  long  process  of  which  is  raised  and  inclined  inwards,  pushing  the  os 
orbiculax'e  and  stapes  towards  the  fenestra  ovalis.  The  base  of  the  latter 
bone  being  in  contact  with  the  fluid  in  the  vestibule,  this  is  stirred  ;  so  that 
this  muscle  likewise  acts  indirectly  in  producing  the  undulations  in  this 
fluid.  The  muscles  of  the  tympanum  are  classed  as  tensors  and  laxators. 
It  is  well  to  know  that  all  are  tensors  and  none  of  them  act  as  relaxors ; 
relaxation  of  the  membrane  occurring  when  the  muscles  are  not  in  action.) 

5.  Tlie  Mucous  Memhrane  of  the  Tympanum. 

Very  fine  and  vascular,  this  membrane  covers  all  the  angularities  of  the 
middle  ear,  is  reflected  on  the  chain  of  bones,  and  continued  into  the 
mastoid  cells.  It  is  continuous  with  that  lining  the  Eustachian  tube,  and 
thenceforward  should  be  considered  as  a  prolongation  of  the  tegumentary 
membrane  spread  over  the  walls  of  the  pharyngeal  vestibule.  It  is  covered 
by  a  simple  pavement  epithelium. 

6.  Eustachian  Tube. 

The  EustacJiian  tuhe  is  a  fibro-cartilaginous  canal  that  communicates 
between  the  cavity  of  the  middle  ear  and  the  pharynx. 

Extending  in  a  straight  line  beneath  the  base  of  the  cranium,  from  the 
tympanic  case  to  the  upper  and  lateral  part  of  the  pharyngeal  cavity,  this  canal 
is  also  named  the  guttural  duct  of  the  tympanimi ;  it  is  nearly  four  inches  long 
in  Solipeds,  "  is  flattened  on  both  sides,  and  bordered  by  the  stylo-pharyn- 
geus  muscle.  Its  upper  or  tympanic  orifice  is  narrow  ;  the  inferior,  guttural, 
or  pharyngeal  orifice,  situated  near  and  behind  the  guttural  openings  of  the 
nasal  cavities,  is  wide,  and  represents  a  great  slit  extending  obliquely  down- 
wards and  outwards ;  the  contiguous  borders  of  this  aperture  are  sustained 
by  a  cartilaginous  plate — a  kind  of  pavilion  formed  by  the  expansion  of  the 
tissue  constituting  the  base  of  the  tube. 

"  In  its  length,  the  guttural  duct  is  cleft  inferiorly,  and  by  this  long 
aperture  the  mucous  membrane  escapes  and  descends  to  form  the  large  sac 
peculiar  to  monodactyles,  known  as  the  guttural  pouch. 

7.  Guttural  Pouches. 

"  The  mucous  membrane  lining  the  Eustachian  tube  is  continuous,forward, 
with  that  of  the  pharynx  ;  above  and  behind,  it  is  prolonged  into  the  tym- 
panic cavity,  which  it  lines.    Below,  it  is  dilated  and  forms  the  guttural  pouch. 


THE  MIDDLE  EAR  OR  TYMPANUM.  845 

"Two  in  number,  one  being  on  each  side,  the  guttural  pouches  lie 
against  each  other  in  the  median  plane,  and  descend  to  the  larynx,  where 
they  terminate  in  a  cul-de-sac  constituting  their  fundus.  Before  and  behind 
they  extend  from  the  anterior  part  of  the  pharynx  to  the  inferior  face  of  the 
atlas.  The  capacity  of  each  is  about  f  ths  of  a  pint ;  but  in  consequence  of 
the  extensibility  of  the  mucous  membrane,  the  extent  and  capacity  of  the 
guttural  pouches  are  particularly  variable. 

*'  Irregular  in  shape,  like  the  space  which  it  occupies,  the  guttural  pouch 
corresponds,  behind  and  above,  to  the  base  of  the  occipital  and  sphenoid 
bones.  When  this  reservoir  is  distended,  its  lower  part,  or  fundus,  descends 
on  the  lateral  portions  of  the  pharynx  and  larynx,  to  the  lower  extremity  of 
the  parotid  gland,  in  the  loose  cellular  tissue  of  that  region. 

"  Externally,  the  guttural  pouch  contracts  numerous  different  relations 
in  the  intermaxillary  and  parotideal  regions,  and  in  its  posterior  portion. 

"fl.  In  the  intermaxillary  region,  it  is  in  relation  with  the  tensor  palati, 
pterygoideus  and  hyo-pharyngeus  muscles,  as  well  as  with  the  internal 
maxillary  artery  and  lingual  nerve ;  it  envelops  the  large  branch  of  the 
hyoid  bone,  and  covers  the  inner  face  of  the  internal  pterygoideus  muscle. 

"  h.  In  the  parotideal  region,  the  guttural  pouch  responds,  above,  to  the 
inner  face  of  the  parotid  gland,  from  which  it  is  separated  by  the  auricular 
vessels  and  nerves  ;  a  little  lower,  at  the  posterior  angle  of  the  hyoid  bone, 
to  the  stylo-hyoideus  muscle  and  the  styloid  process  of  the  occipital  bone ; 
here  the  auricular  artery  passes  obliquely  upwards  and  backwards,  and 
the  membrane  of  the  pouch  is  more  closely  united  to  the  parts  covering  it. 

"  Below  this,  the  guttural  pouch  is  in  relation  with  the  stylo-maxillaris 
muscle,  external  carotid,  and  the  nerves  forming  the  guttm*al  plexus,  such  as 
the  ninth  and  twelfth  pairs,  the  great  sympathetic,  etc.  Lower,  it  is  related 
to  the  parotid  gland,  to  the  inferior  extremity  of  which  it  may  be  prolonged. 

"  c.  Posteriorly. — The  guttural  pouch  is  in  relation  with  the  atlas,  flexor 
muscles  of  the  head,  occipital  artery,  etc.  ;  it  forms  a  fold  that  envelops 
principally  the  pneumogastric  and  sympathetic  nerves,  and,  anteriorly, 
another  fold  that  incloses  the  internal  carotid. 

"  The  mucous  membrane  of  the  guttural  pouches  is  thicker  and  stronger 
than  that  lining  the  Eustachian  tube  and  the  cavity  of  the  tympanum. 
Only  slightly  adherent  to  the  adjacent  parts,  except  at  the  branch  of  the 
hyoid,  the  inner  face  of  the  stylo-hyoideus,  etc.,  it  is  smooth  internally,  and 
lubrified  by  the  mucus  it  secretes.  It  may  become  the  seat  of  purulent 
collections,  which  compress  the  larynx  and  obstruct  the  respiration,  and  it  is 
in  such  cases  that  the  pouch  is  punctured.  This  membrane  receives 
numerous  fine  vascidar  and  nervous  ramifications  from  the  neighbouring 
branches. 

"  The  guttural  pouches  communicate  with  the  pharynx  and  cavity  of  the 
tympanum,  and  usually  contain  air  ;  the  quantity  of  this  may  vary  in  health, 
according  to  the  degree  of  dilatation  of  these  membranous  sacs.  Their 
dilatation  is  chiefly  produced  by  the  palato-pharyngeus  muscle,  several 
fibres  from  which  extend  to  their  mucous  membrane ;  and,  besides,  when 
the  ear  is  erected  this  membrane  is  thrown  into  a  state  of  tension,  through 
the  adhesion  of  the  lower  prolongation  of  the  concha  to  its  surface. 

"  The  functions  of  the  guttural  pouches  are  far  from  being  known.  It 
cannot  be  afl&rmed  that  they  increase  phonation  ;  indeed,  their  use  appears 
to  be  rather  related  to  audition,  if  it  be  considered  that  these  annexes  of  the 
guttural  duct  of  the  tympanum  coincide,  in  Solipeds,  with  a  less  development 
of  the  mastoid  cells  than  in  the  other  animals. 


846  TJJE  APPARATUS  OF  THE  SENSES. 

"  With,  regard  to  the  Eustachian  tube,  it  serves  to  renew  the  air  in  the 
tympanic  cavity,  this  renewal  being  indispensable  to  the  perfect  accomplish- 
ment of  hearing." — Lavocat. 

(It  is  essential  that  the  equilibrium  between  the  external  air  and  that 
in  the  cavity  of  the  tympanum  should  be  maintained,  in  order  to  avert 
irregular  tension,  and  even  rupture  of  the  membrana  tympani.  Perosino 
states  that  the  guttural  pouches  are  filled  with  warm  air  during  expiration, 
and  that  this  is  partly  changed  for  cold  air  in  inspiration.) 

Article  III. — The  External  Ear, 

The  external  ear  comprises  the  external  auditory  canal,  and  a  widened 
appendage  opening  outwardly,  designated  the  concha  or  pavilion. 

THE  external  AUDITORY  CANAL. 

This  canal  (meatus  auditorius  externus),  described  in  the  osteology  (as 
situated  in  the  petrous  bone),  has  at  the  bottom  the  membrana  tympani, 
which  separates  it  from  the  middle  ear.  Its  entrance,  the  external  auditory 
hiatus,  gives  attachment  to  the  infundibulum  of  the  conchal  apparatus.  It  is 
lined  by  a  thin  integumentary  membrane  intermediate  in  character  between 
the  skin  and  mucous  membrane,  and  has  in  its  substance  a  large  number  of 
glands  and  convoluted  tubes,  analogous  to  the  sudorijjarous  glands,  but  here 
named  ceruminous  glands,  as  they  secrete  an  unctuous  matter,  the  cerumen. 

the    concha   or    PAVILION. 

The  external  trumpet-shaped  appendage  named  the  concha  (concha  auris) 
varies  much  in  shape  in  the  different  animals,  though  in  all  it  offers  the 
same  details  in  organisation :  a  cartilaginous  framework  composed  of  three 
pieces,  muscles  to  move  these,  an  adipose  cushion  to  insure  liberty  of 
movement,  and  integuments  covering  the  whole, 

1.  Cartilages  of  the  Concha. 

The  three  pieces  composing  the  concha  are  :  1,  The  conchal  cartilage;  2, 
Annular  cartilage ;  3,  Scutiform  cartilage. 

1.  Conchal  Cartilage. — The  principal  portion  of  the  pavilion,  this 
cartilage  determines  its  general  configiu'ation.  In  shape,  it  resembles  a 
trumpet  with  a  wide  opening  on  one  side.  Its  entrance  is  elliptical,  and 
elongated  vertically,  being  circumscribed  by  tw^o  thin  borders  which  unite 
above  at  a  point  that  constitutes  the  summit  (apex)  of  the  organ.  Its  base, 
bulging  in  a  cul-de-sac,  terminates  in  front  by  a  constricted  infundibulum ; 
it  is  attached  to  the  margin  of  the  auditory  hiatus  by  means  of  the  annular 
cartilage,  and  to  the  sur^ice  of  the  guttural  pouch  by  a  pointed  prolongation 
that  descends  outside  this  annular  cartilage,  beneath  the  parotid  gland,  and 
terminates  by  several  fibrous  filaments.  This  portion  of  the  framework  of 
the  concha  is  a  cartilaginous  plate,  rolled  on  itself  in  such  a  manner  as  to 
circumscribe,  between  its  borders,  the  entrance  to  the  ear,  and  to  form,  in- 
feriorly,  the  complete  infundibuliform  canal  just  mentioned.  In  Solipeds, 
this  plate  is  rigid  and  erect,  and  much  more  developed  in  the  Ass  and  Mule 
than  in  the  Horse,  (Externally,  the  integument  of  the  ear  is  covered  by 
ordinary  hair,  but  internally  there  are  long  fine  hairs,  especially  near  the 
entrance  ;  these  prevent  the  intrusion  of  foreign  substances.) 

2.  Annular  Cartilage  — By  this  name  is  known  a  little  ring-shaped 


THE  EXTERNAL  EAB.  847 

plate,  placed  at  the  lower  part  of  the  conchal  plate,  intermediate  between 
it  aud  the  auditory  canal.  The  internal  integumentary  membrane,  with  some 
yellow  elastic  fasciculi,  unite  this  cartilage  to  the  other  two  portions 
between  which  it  is  situated.  Its  relations  with  these  are  such,  that  it 
receives  within  its  lower  border  the  bony  circular  i>rominence  forming  the 
margin  of  the  auditory  hiatus,  wliile  it  may  itself  be  received  into  the  in- 
fundibuliform  caual  of  the  conchal  cartilage — an  arrangement  resembling 
the  tubes  of  a  telescope. 

3.  ScuTiFOKM  Cartilage. — This  is  a  small  cartilaginous  plate,  situated 
in  front  of  the  base  of  the  concha,  at  the  surface  of  the  temporal  muscle ;  it 
is  irregularly  triangular,  is  attached  to  the  conchal  cartilage  by  some 
muscular  fasciculi,  and  transmits  to  that  cartilage  the  action  of  some  other 
muscles  which  are  iixed  on  the  cranial  bones. 

(The  arteries  of  the  concha  proceed  from  branches  of  the  external  carotid, 
and  the  veins  pass  to  a  trunk  of  the  same  name ;  the  nerves  are  divisions 
of  the  facial  and  the  first  cervical  pair.) 

2.  Muscles  of  the  External  Ear. 

There  are  found,  on  the  surface  of  the  concha,  within  and  without,  some 
fleshy  fibres,  which  are  veritable  intrinsic  muscles.  But  the  slight  importance 
of  these  induces  us  to  pass  them  over,  in  order  to  study  exclusively  the 
extrinsic  muscles,  which  move  the  conchal  apparatus.  These  are  ten  in 
number :  in  the  first  layer  are  the  zygomatico-auricularis,  temporo-auricidaris 
externus,  scuto-auricularis  externus,  three  cervico-auriculares,  and  the  paroiiclo- 
auricularis ;  in  tbe  second  layer,  the  temporo-auricularis  internus,  scuto- 
auricularis  internus,  and  the  mastoido-auricularis. 

1.  Zygomatico-auricularis  {attolens  anterior  —  Percivall  ;  temporo- 
auricularis — Leyh.  Figs.  110,  5  ;  396). — This  muscle  is  generally  composed 
of  two  fleshy  bands  joined  by  cellular  tissue,  and  rising  from  the  zygomatic 
process  of  the  temporal  bone  by  means  of  an  aponeurosis  common  to  it 
and  the  orbicularis  palpebras.  The  inferior  of  these  two  bands  is  inserted 
to  the  outside  of  the  base  of  the  concha,  its  fibres  mixing  with  those  of  the 
parotido-auricularis ;  the  superior  band  terminates  on  the  outer  border  of 
the  scutiform  cartilage. 

Placed  immediately  beneath   the   skin,  this  muscle  partly  covers  the 
superior  extremity  of  the  parotid  gland,  and  the  zygomatic  process. 
It  draws  the  ear  forward. 

2.  Temporo-auriculahis  ExTERNxrs  (attolens  maximus — Percivall.  Figs. 
110,  1 ;  396). — A  very  thin,  wide  muscle,  covered  by  the  skin,  lying  on  the 
temporal  muscle,  united  posteriorly  to  the  superior  cervico-auricularis,  in 
front  and  outwardly  to  the  zygomatico-auricularis.  It  arises  from  the 
whole  of  the  parietal  crest  or  ridge,^  mixing  in  its  upper  half  or  third  with 
the  muscle  of  the  opposite  side ;  it  terminates,  by  one  portion,  on  the  inner 
margin  of  the  scutiform  cartilage,  and  by  another,  on  the  inner  side  of 
the  conchal  cartilage,  by  means  of  a  thin  fascia  that  covers  part  of  the 
former  cartilage  and  the  external  scuto-auricularis. 

It  acts  as  an  adductor  of  the  concha,  drawing  it  inwards  ;  it  also  carries 
it  forwards,  and  concurs  in  making  it  pivot  on  itself,  so  as  to  bring  the 
opening  of  the  ear  forward.     (In  the  Ox,  the  common  muscles  of  the  ear  do 

'  Owins;  to  this  orest  borclerinj^  the  temporal  fossa,  Girard  has  thought  proper  to  give 
to  the  two  muscles  of  the  ear  attached  thereto,  the  name  of  temporo-auriculares  ;  but  it 
would  be  more  appropriate  to  designate  them  the  imrieto-auriculares. 


848  TEE  APPARATUS  OF  TEE  SENSES. 

not  join  on  the  median  line,  but  are  placed  at  the  sides  of  the  head,  below 
the  horns.) 

3.  ScuTO-AURicuLAEis  ExT^:ENUS  (^anterior  conchoe — Percivall.  Fig.  396). 
— This  muscle  may  be  said  to  be  a  dependency  of  the  preceding,  whose 
action  it  transmits  to  the  conchal  cartilage,  and  renders  it  more  comj^lete. 

Extending  from  the  external  face  of  the  scutiform  cartilage  to  the  inner 
side  of  the  concha,  and  generally  composed  of  two  fasciculi,  it  is  covered  by 
the  skin  and  the  conchal  band  of  the  external  temporo-auricularis,  while  it 
covers  part  of  the  internal  scuto-auricular  muscle. 

Fiff.  396. 


MUSCLES  OF   THE   EAR. 

1,  Cervico-auricularis  superficialis ;  2,  Temporo-auricularis  internus ;  3,  4,  Tem- 
poro-auricularis externus  ;  5,  Scutiform  cartilage  ;  6,  Scuto-auricularis  externus ; 
7,  Posterior  auricular  artery  ;  8,  Portion  of  the  zygomatico-auricularis  ;  9,  Orbital 
process;  10,  Temporo-auricularis  internus;  11,  Temporal  muscle;  12,  Scutiform 
cartilage;  13,  Ditto  ;  14,  Concha  of  the  ear  ;  15,  Scuto-auricularis  externus;  16, 
Internal  scuto-auricularis  ;  17,  Parotido-auricularis  ;  18,  Corrugator  supercilii ; 
19,  Zygomatico-auricularis. 


When  this  muscle  contracts,  it  principally  participates  in  producing  the 
rotatory  movement  that  carries  the  opening  of  the  concha  outwards. 

4.  Cervico-auriculares. — (Percivall  apparently  makes  one  muscle  of 
these  three — the  retrahentes  aurem ;  Leyh  designates  them  as  the  cervico- 
auriculares  externus,  medius,  and  internus.  (Fig.  396).  Three  in  number, 
and  situated  behind  the  ear,  these  muscles  are  broad,  thin  bands,  extending 
from  the  cervical  ligament  to  the  conchal  cartilage.  With  regard  to  their 
superposition  at  their  origin,  they  may  be  distinguished  as  superficial,  middle. 


THE  EXTERNAL  EAR.  849 

and  deep ;  the  situation  of  their  point  of  insertion  in  the  concha  also  permits 
their  being  classed  as  superior,  middle,  and  inferior. 

The  superior,  or  superficial  cervico-auricularis,  closely  united  to  the 
external  temporo-auricularis,  and  covered  by  the  skin,  covers  the  middle 
cervico-auricular,  and  internal  temporo-auricular  muscles.  Attached  by  its 
terminal  extremity  to  the  middle  of  the  posterior  face  of  the  concha,  it  draws 
that  cartilage  backwards  and  downwards. 

The  middle  cervico-auricularis,  comprised  at  its  origin  between  the  other 
two,  and  intimately  attached  to  them,  especially  the  deej)  one,  is  in  relation 
with  the  skin  for  the  greater  part  of  its  superficies.  Its  terminal  extremity 
is  very  wide  and  thin,  and  passes  over  the  upper  end  of  the  parotid  gland, 
to  be  inserted  outwardly  into  the  base  of  the  concha,  after  being  slightly 
insinuated  beneath  the  parotido-auricular  muscle.  1'his  is  a  rotator  muscle, 
turning  the  opening  of  the  ear  outwards  and  backwards. 

The  inferior,  or  deep  cervico-auricularis,  concealed  beneath  the  upper 
extremity  of  the  parotid,  to  which  it  adheres  closely,  is  inserted  at  the  base 
of  the  concha.     Its  action  is  similar  to  that  of  the  middle  muscle. 

5.  Parotido-aueicularis  (ahducens,  or  deprimens  aurem  —  Percivall. 
Fig.  110, 7). — Lying  on  the  external  face  of  the  parotid  gland,  this  is  a  long, 
thin,  ribbon-like  band,  narrower  and  thicker  at  its  ujjper  than  its  under 
extremity.  It  arises  on  the  tissue  of  the  gland,  and  terminates  outside 
the  base  of  the  concha,  below  the  inferior  commissure  formed  by  the  two 
borders  of  that  cartilage. 

Covered  externally  by  a  very  thin  portion  of  the  cervico-facial  cutaneous 
muscle,  the  parotido-auricularis  is  an  abductor  of  the  ear,  inclining  it 
outwards. 

6.  Temporo-auricularis  Internus  {attolens  posterior — Percivall.  Fig. 
110,  3). — Situated  beneath  the  superficial  muscle  of  this  name,  and  partly 
covered  by  the  superior  cervico-auricularis,  this  muscle  is  long  and  triangular 
in  shape,  bright-red  in  colour,  and  extending  transversely  on  the  surface  of 
the  temporalis ;  it  is  attached,  inwardly,  to  the  sagittal  or  spur-like  ridge  of 
the  parietal  bones,  and  outwardly,  by  means  of  a  small  tendon,  to  the  inner 
side  of  the  concha,  within  the  terminal  insertion  of  the  superficial  cervico- 
auricularis.     It  is  an  adductor  of  the  ear. 

(In  the  Ox,  this  muscle  is  not  covered  by  the  external  temporo-auricularis. 
In  the  Slieep  and  Goat,  it  is  placed  between  the  parietal  bone  and  that  muscle, 
and,  to  reach  the  concha,  it  passes  beneath  the  scutiform  cartilage.) 

7.  ScuTO-AURicuLAEis  Internus.  {Posterior  conchce — Percivall.  Leyh 
makes  two  muscles  of  it — small  and  great.) — This  is  a  muscle  composed  of 
two  short,  pale  fasciculi,  which  cross  each  other  very  obliquely,  are  concealed 
beneath  the  scutiform  cartilage  and  the  scuto-auricularis  externus,  and  lie 
directly  on  the  adipose  cushion  of  the  ear.  They  arise  from  the  inner  face 
of  the  scutiform  plate,  pass  backwards,  and  terminate  at  the  base  of  the 
concha,  behiod  the  infundibuliform  cavity  which  that  cartilage  forms  at  its 
root.  This  muscle  is  antagonistic  to  the  superficial  muscle  of  that  name, 
as  it  turns  the  opening  of  the  ear  outwards,  and  even  backwards. 

8.  Mastoido-auricttlaris. — This  name  is  given  to  a  very  thin  fasciculus 
lying  vertically  on  the  inner  side  of  the  cartilage,  at  the  entrance  to  the  ear. 
Arising  from  the  margin  of  the  auditory  external  hiatus,  and  attached  to  the 
base  of  the  concha,  this  little  muscle,  in  contracting,  constricts  the  carti- 
laginous tube  with  which  it  is  in  contact. 


850  THE  APPARATUS  OF  THE  SENSES. 

3.  Adipose  CusMon  of  the  External  Ear. 

This  cusliion,  which  is  never  absent,  even  in  the  most  emaciated  animals, 
envelops  the  base  of  the  concha  in  front,  inwardly,  and  posteriorly.  It 
facilitates  the  movements  of  that  organ. 

4.  Integuments  of  the  External  Ear. 

The  skin  covering  the  concha  is  covered  with  fine  close  hairs.  That 
lining  its  interior  is  very  thin  and  vascular,  adheres  closely  to  the  cartilage, 
and  is  furnished  with  long  silky  hairs,  to  prevent  the  entrance  of  dust  into 
the  ear. 

DIFFEEENTIAL   CHABACTERS   IN   THE   AfDlTORY    APPAEATUS   OF   OTHER   THAN   SOLIPED 

ANIMALS. 

There  are  no  notable  differences  in  the  internal  ear. 

In  the  middk  ear,  there  ai-e  souae  modifications,  either  in  the  bones  or  accessory  parts. 
In  Ruminants,  the  auditory  bones  are  like  those  of  the  Horse,  except  that  the  handle  of 
the  malleus  is  more  curved,  and  the  body  of  the  incus  is  longer.  In  the  Dog,  the  handle 
of  the  malleus  is  covered  with  small,  pointed  processes,  and  tlie  branches  of  the  stapes  are 
lono-  and  thick.  In  the  Pig,  the  branches  of  the  latter  are  slight  and  inilected,  and  the 
base  is  wide  and  thin  :  in  a  word,  the  stapes  of  this  animal  bears  no  resemblance  to  a 
stirrup ;  the  malleus  is  very  much  inflected  forwards.  In  the  last  two  animals,  no  osseous 
nucleus  is  found  in  the  tendon  of  the  stapedian  muscle. 

It  is  needless  to  say  that  the  fenestra  ov.ilis  varies  with  the  base  of  the  stapes.  (The 
absence  of  the  mastoid  cells  in  the  Sheep  nnd  Goat  has  been  already  noted.) 

The  Eustachian  tube  exists  in  all  the  animals,  but  the  guttural  pouches  are  only 
found  in  Solipeds. 

In  the  external  ear,  the  conclial  cartilage  varies  much  in  shape.  It  is  thin,  inclined 
outwards,  and  widely  opened  in  Ruminants.  In  the  Pig,  it  differs  a  little,  according  to 
breed,  though  it  is  always  much  developed,  sometimes  erect,  but  most  frequently 
drooping.  It  is  always  short,  pointed,  erect,  and  open  in  front,  in  the  Cat.  (In  this 
animal  a  small  duplicature  of  the  external  margin  of  the  concha  is  often  seen.)  In  Birds, 
the  external  ear  is  limited  to  the  auditory  canal. 

(The  differences  in  the  muscular  arrangement  have  been  noted  elsewhere.) 

COMPARISON   BETWEEN   THE   AUDITOKY   APPARATUS   IN   BtAN   AND   THAT   OP   ANIMALS. 

There  is  nothing  to  be  said  regarding  the  internal  ear.  The  middle  ear  comprises 
the  same  parts  as  that  of  mammifors  other  than  Solipeds.  The  handle  of  the  malleus  is 
straiuditer,  the  incus  more  voluminous,  and  the  stapes  thinner,  proportionately,  than  in 
animals.  There  is  no  bony  nucleus  in  the  stapedian  muscle.  The  muscle  of  the  malleus 
is  lodged  in  a  distinct  canal  belonging  to  the  Eustachian  tube. 

The  external  ear  is  composed  of  only  two  cartilages  :  one,  forming  the  base  of  the 
concha,  represents  that  cartilage  in  animals ;  the  other,  belonging  to  the  auditory  canal, 
resembles  the  annular  cartilage  in  the  Horse.  The  concha  is  very  irregular  in  shape,  and 
stands  at  an  angle  of  from  15°  to  4,5°  from  the  temporal  bone ;  it  is  convex  superiorly, 
and  terminates  inferiorly  by  a  small  lobe.  On  its  anterior  face  it  presents  prominences 
and  depressions;  the  former  are  four  in  number:  the  helix,  a  fold  encircling  the  ear 
behind  and  above ;  the  antihelix,  a  concentric  prominence,  almost  parallel  with  the 
preceding ;  the  tragus,  a  triangular,  pointed  process,  covered  with  hair,  situated  in  front 
of  the  auditory  canal  (meatus) ;  the  antitragus,  opposite  the  tragus,  behind  the  canal, 
and  above  the  lobule.  The  depressions  are  :  the  concha,  a  wide  cavity,  lihiited  by  the 
antihelix  ;  the  scaphoid  fossa  (fossa  innominata)  situated  above  the  latter;  and  the  fossa 
triangularis  comprised  between  the  helix  and  antihelix. 

The  pavilion  of  the  ear  is  traversed  by  several  muscular  fasciculi,  which  can  have  no 
influence  on  its  movements.  The  concha  lias  also  extrinsic  muscles — the  anterior  auri- 
cularis  (attrahens  aurem\  auricularis  superioris  (attolens  aurem),  and  the  auricularis 
posteriores  (retrahens  aurem).    The  action  of  these  on  the  concha  is  very  slight. 


BOOK  VIII. 

Generative  xIppaeatus. 

Individuals  in  the  organic  kingdom  possess  the  faculty  of  reproduction, 
and  thus  perpetuate  the  species  to  which  they  belong :  a  grand  and  beautiful 
law  of  the  vital  force,  which  holds  under  its  care  the  preservation  of  the 
organised  world.  In  mammifers,  the  generation  of  a  new  being  demands 
the  concurrence  of  two  individuals — a  male  and  female — who  have  inter- 
course imder  certain  determinate  circumstances.  The  female  furnishes  a 
germ — the  ovum,  and  the  male  a  fertilizing  fluid — the  semen,  which  vivifies 
the  ovum,  and  renders  it  capable  of  development. 

We  have,  therefore,  to  study  separately  the  generative,  or  genital  organs 
of  the  male,  and  those  of  the  female. 


CHAPTER  I. 


GENITAL   ORGANS   OF   THE   MALE. 


The  semen  is  elaborated  in  the  structure  of  the  two  testicles  :  lobular  glands, 
each  of  which  is  provided  with  an  excretory  duct,  doubled  a  great  number 
of  times  on  itseK  at  its  commencement,  to  form  the  epididymis,  and  destitute 
of  sinuosities  for  the  remainder  of  its  extent,  which  is  named  the  deferent 
canal  (vas  deferens).  This  canal  carries  the  fecundating  fluid  into  the 
vesicidse  seminales,  reservoirs  with  contractile  walls,  where  it  accumulates, 
and  whence  it  is  expelled  during  copulation  by  passing  through  the 
ejaculatory  canals  (or  ducts),  and  the  urethral  canal.  The  latter  is  a  single 
canal  common  to  the  two  apparatus  of  generation  and  urinary  depuration  ; 
it  is  provided  in  its  course  with  three  accessory  glands  -  the  prostate,  and 
Coicper's  glands,  and  is  supported  by  an  erectile  stalk,  the  corjnis  cavernosum, 
with  which  it  forms  an  elongated  organ,  the  penis,  which,  in  the  act  of 
copulation,  is  introduced  into  the  vagina,  to  the  bottom  of  which  it  carries 
the  spermatic  fluid. 

We  will  successively  consider  the  secretory  organs  or  testicles,  and  the 
excretory  apparatus,  comprising  all  the  other  organs. 

THE  TESTICLES,  OR  SECRETOKT  ORGANS  OF  THE  SEMEN. 

The  testicles  (testes)  are  two  glands  suspended  on  each  side  of  the  pines, 
between  the  thighs,  where  each  occupies  a  particular  serous  pouch,  the 
vaginal  sheath  (^tunica  vaginalis).  We  will  commence  by  describing  this 
cavity,  and  afterwards  the  organ  it  contains. 


852  THE  GENERA  TI VE  APFA  RA  TUS. 

1.  Tunica  Vaginalis. 

The  tunica  vaginalis,  in  tlie  domesticated  animals,  is  only  a  diverticulum 
of  tlie  abdominal  cavity,  the  serous  membrane  of  which — the  peritoneum — 
becomes  a  hernia  in  the  inguinal  canal,  passing  through  the  upper  (internal) 
inguinal  ring,  and  prolonged  below  the  inferior  (external)  ring,  so  as  to 
form  a  serous  sac,  which  is  enveloped  by  membranous  walls. 

We  have  to  study,  in  the  vaginal  sheath:  1,  Its  interior;  2,  The 
enveloping  membranes  which  form  the  external  walls,  and  to  which  we  give 
the  common  name  of  scrotum. 

Liter ior.— The  serous  sac  constituting  the  tunica  vaginalis,  is  vertically 
elongated,  and  slightly  inclined  downwards,  inwards,  and  backwards.  Its 
inferior  extremity,  forming  the  bottom,  or  cul-de-sac,  is  pear-shaped,  and 
lodges  the  testicle  and  its  epididymis.  Its  middle  portion,  contracted  into  a 
narrow  canal,  contains  the  spermatic  cord.  The  superior  extremity,  or 
entrance,  is  open,  to  maintain  communication  with  the  abdominal  cavity; 
through  it  pass  the  spermatic  vessels  and  vas  deferens. 

As  has  been  said,  the  peritoneum  forms  the  vaginal  sac.  As  in  the 
abdomen,  it  is  divisible  into  two  layers — parietal  and  visceral.  The  latter 
(tunica  vaginalis  propria)  covers  the  testicle  and  the  cord  ;  while  the  former 
{tunica  vaginalis  communis,  or  reflexa)  lines  the  innermost  of  the  membranous 
coverings  which  serve  as  a  wall  to  the  tunica  vaginalis.  These  two  layers 
are  made  continuous  by  a  serous  frsenum,  analogous  to  the  mesentery  which 
sustains  the  floating  colon  ;  like  it,  it  is  formed  by  the  junction  of  the  two 
layers.  Flat,  elongated  from  above  to  below,  and  extending  vertically  from 
one  end  of  the  sheath  to  the  other,  this  fraenum  is  attached,  by  its  upper 
border,  behind  the  spermatic  cord ;  its  lower  extremity  passes  over  the 
epididymis,  and  from  it  on  to  the  testicle ;  above,  it  is  continued  into  the 
abdominal  cavity,  in  accompanying  the  different  canals  composing  the  cord. 

(A  small  quantity  of  serous  fluid  is  usually  present  in  the  tunica 
vaginalis.     When  in  excess  it  gives  rise  to  hydrocele.) 

Enveloping  Membranes. — The  stratified  layers  that  form  the  external 
walls  of  the  vaginal  sheath,  and  which  are  generally  described  in  anatomical 
treatises,  with  the  two  serous  layers,  as  the  envelopes  of  the  testicle,  are  four 
in  number.  Reckoning  them  from  within  to  without,  they  are  the  fibrous 
tunic,  cremaster  muscle,  dartos,  and  scrotum. 

Fibrous  Tunic  {infundihuUform  fascia). — This  forms  the  most  complete 
covering  to  the  tunica  vaginalis,  extending,  as  it  does,  over  the  whole  surface 
of  the  parietal  serous  layer,  to  which  it  is  closely  adherent.  Very  thin, 
especially  at  the  points  corresponding  to  the  cremaster,  this  membrane  is 
continuous,  around  the  upper  inguinal  ring,  with  the  transversalis  fascia,  of 
which  it  is  only  a  dependency ;  its  external  face  is  in  relation  with  the 
cremaster  and  dartos. 

Cremaster. — This  muscle  is  usually  described  as  an  envelope  of  the 
testicle,  by  the  name  of  tunica  erytliroides.  In  the  domesticated  animals,  it 
is  a  bright-red  band,  attached,  above,  to  the  inner  or  peritoneal  surface  of 
the  ilio-lumbar  aponeurosis ;  it  descends  nito  the  inguina  1  canal,  envelops 
outwardly  only  the  middle  portion  of  the  sheath  of  the  testicle,  and  expands 
below  on  the  cul-de-sac,  where  its  fibres  terminate  by  small  tendons,  which 
are  inserted  into  the  external  sm*face  of  the  fibrous  tunic.  Therefore  it  is 
that  the  envelope  the  cremaster  forms  is  very  incomplete,  the  greater  portion 
of  the  testicle,  and  the  inner  side  of  the  cord,  being  left  unprotected  by  this 
muscular  tunic.     It  is  in  relation,  inwardly,  with  the  fibrous  membrane,  to 


TEE  MALE  GENITAL  ORGANS.  853 

which  it  is  united  by  a  plcutifiil  cellular  tissue ;  externally,  it  responds  to 
the  posterior  wall  of  the  inguinal  canal  and  the  dartos. 

It  is  the  contraction  of  the  cremaster  that  causes  the  sudden  ascent  of 
the  testicle. 

Daktos. — The  tissue  composing  this  tunic  is  contractile ;  it  is  con- 
stituted by  a  mixture  of  elastic  and  unstriped  muscular  fibres.  The  dartoic 
tunic  docs  not  reach  the  inguinal  canal ;  consequently,  it  does  not  cover 
that  part  of  the  tunica  vaginalis.  It  forms  a  pouch  below  the  inguinal  ring, 
and  is  spread  from  around  the  margin  of  this  on  to  the  neighouring  parts,  to 
which  it  adheres  somewhat  closely  ;  it  is  prolonged,  gradually  thinning,  into 
the  sheath  of,  and  even  on  to  the  penis  itself,  and  to  the  tunica  abdomiualis, 
as  well  as  between  the  thighs.  The  two  pouches  it  forms  are  quite  in- 
dependent of  each  other,  never  becoming  confoimded,  though  placed  in 
contact  on  the  mesial  line  to  form  a  double  partition  {septum  scroti),  whose 
leaves  are  separated  above  for  the  passage  of  the  penis.  The  dartos  is  in 
relation,  inwardly,  with  the  fibrous  and  erythroid  tunics,  from  which  it  is 
isolated  by  an  abundance  of  lamellar  cellular  tissue,  which  is  very  condensed 
towards  the  globus  major  epididymis,  and  forms  at  this  point  a  kind  of  cord 
that  passes  from  the  fibrous  tunic  to  the  dartos,  adhering  strongly  to  each. 
Externally,  the  dartos  is  covered  by  the  scrotum. 

This  tunic  determines  the  vermicular  movements  of  which  the  scrotum 
is  the  seat. 

ScKOTUM. — The  different  membranes  enumerated  above  are  double,  one 
being  for  each  tunica  vaginalis  ;  but  the  scrotum  constitutes  a  single  pouch, 
enveloping  the  two  testicles  at  the  same  time.  It  is  merely  the  portion  of 
skin  covering  this  region,  and  is  thin,  and  so  closely  adherent  to  the  dartos, 
that  it  can  only  with  diflSculty  be  separated  from  it.  It  is  covered  by 
very  short  fine  hair,  and  the  extremely  numerous  sebaceous  follicles  in  its 
texture  secrete  an  unctuous  matter  that  renders  its  surface  soft  to  the 
touch. 

(There  are  also  numerous  sudoriparous  glands,  and  these,  with  the 
sebaceous  glands,  keep  the  skin  soft  and  pliable,  and  modify  the  eifects  of 
friction  during  progression.  On  its  surface  it  shows  a  raphe  or  seam  in  the 
middle,  which  is  a  ti'ace  of  its  primary  division,  and  corresponds  to  the 
median  septum  separating  the  testicles.) 

2.  The  Testicles.     (Figs.  397,  398,  401.) 

External  Conformation. — Each  testicle  is  oval  in  shape,  flattened  on  both 
sides,  lodged  in  the  cul-de-sac  of  the  tunica  vaginalis,^  and  suspended  at  the 
extremity  of  the  spermatic  cord.  The  description  of  this  organ  is  extremely 
simple;  it  ofiers  for  study  two  faces,  two  Oorders,  and  tioo  extremities. 

The  faces,  external  and  internal  are  smooth  and  round.  The  inferior 
border  is  convex  and  free,  like  the  faces ;  the  superior,  almost  straight,  is 
related  to  the  epididymis,  which  adheres  to  it  by  its  head  and  tail. 

Means  of  Attachment. — The  testicle  is  freely  pendent  in  the  lower 
part  of  the  tunica  vaginalis,  where  it  cannot  readily  be  displaced,  because  of 
the  narrowness  of  the  space  containing  it.     It  is  suspended,  by  its  upper 

1  One  or  berth  testicles  may  be  retained  in  the  constricted  portion  of  the  tunica 
vaginalis,  or  remain  in  the  abdomen ;  animals  in  which  this  occurs  are  named  monorchids 
or  cryptorchids.  The  absence  of  one  or  two  testicles  (anorchidism)  is  extremely  rare. 
Ectopia  of  the  testicles  is  the  designation  applied  to  these  organs  when  they  are  found 
elsewhere  than  in  their  ordinary  situation. 

57 


854 


THE  GENERATIVE  APPARATUS. 


border,  to  the  testicular  or  spermatic  cord  ^  a  thick  funiculus  contained  in  the 
middle  portion  of  the  vaginal  sheath,  and  formed  by  the  aggregation  of  the 
spermatic  vessels  with  the  vas  deferens. 

This  cord  is  itself  sustained  in  the  sheath  by  the  fraenum  that  unites  the 
two  serous  tunics  of  that  cavity. 

Structure. — Independently  of  the  serous  tunic  that  covers  the  exterior 
of  the  testicle,  there  enter  into  its  structure  a  fibrous  membrane,  tissue  proper, 
and  vessels  and  nerves.     The  excretory  duct  will  be  studied  separately. 

Fibrous  Membrane. — This  membrane,  designated  the  tunica  albuginea, 
forms  a  strong  resisting  shell  around  the  testicle,  and  its  texture  is 
channeled  by  sinuous  spaces  which  lodge  the  large  spermatic  vessels.  It 
is  covered  by  the  visceral  layer  of  the  tunica  vaginalis,  to  which  it  closely 
adheres ;  its  inner  face  sends  thin  septa  into  the  proper  substance  of  the 
gland,  which  divide  the  latter  into  the  spermatic  lobules.  Towards  the 
upper  border  of  the  testicle,  and  in  front,  the  tunica  albuginea  is  slightly 
thickened;  this  part  is  named  the  corpus  Higmori  (ot  mediastinum  testis), 
and  at  this  point  the  seminal  ducts  pass  tlirough  it  to  reach  the  epididymis. 

(This  membrane  is  dense  and  inelastic,  being  composed  of  white  fibrous 
tissue  interlacing  in  every  direction.) 

Tissue  proper. — The   proper   substance 


Fig.  397. 


of  the  testicle  resembles  a 
greyish-yellow  pulp,  contained 
in  the  tunic  albuginea ;  it  is 
divided  by  the  prolongations 
which  that  tuuic  sends  into  its 
interior  into  small  distinct 
lobules  (lobuli  testis),  independ- 
ent of  each  other.  These 
lobules  vary  in  number,  from 
two  to  three  hundred,  and  all 
have  the  same  organisation, 
each  being  constituted  by  two 
or  three  extremely  convoluted 
filiform  tubuli,  about  fiom  one 
to  two  yards  in  length.  These 
tubes,  the  tubuli  seminiferi, 
anastomose  frequently  with 
each  other  near  their  extremi- 
ties, twine  together,  and  can  be 
unwound  like  a  ball  of  thread. 
One  of  their  extremities  ter- 
minates in  a  cul-de-sac,  the 
other  being  detached  from  the 
lobule,  and  enters  a  central 
system  of  excretory  ducts  wliich 
■will  be  referred  to  imme- 
diately. 

When  we  cut  through  a  tes- 
ticle vertically  and  lengthways, 
so  as  to  divide  the  corpus  HigJi- 
mori  into  two  lateral  portions,   there  is  seen  in  its  substance  a  whitish 

1  In  surgical  anatomy,  there  is  sometimes  included  in  the  spermatic  cord  the  middle 
portion  of  the  tunica  vaginalis  and  all  its  envelopes— the  serous,  fibrous,  and  erythtoid 
tunics. 


A   TESTICLE    (HUMAN)    INJECTED    WITH    MERCURY. 

a,  a,  Lobules  formed  of  seminiferous  tubes ;  6,  Rete 
testis ;  c,  Vasa  efferentia  ;  d,  Flexures  of  the  efferent 
vessels  passing  into  the  head,  e,  e,  of  the  epididy- 
mis ;  /,  Body  of  the  epididymis ;  g,  Appendix ;  h, 
Cauda  :  i,  Vas  deferens 


THE  MALE  GENITAL  OBGANS. 


855 


Fig.  398. 


framework,  sometimes  not  very  apparent,  "nhich,  curving  upwards  at  both 
extremities,  extends  from  that  body  to  the  posterior  end  of  the  testitde 
where  it  disappears  ;  from  this  are  given  off  a  Large  number  of  tibrill® 
(trabeculse  testis),  which  diverge  in  all  directions.  A  mercm-ial  injection 
by  the  vas  deferens,  shows  that  this  part  of  the  testicle  is  chiefly  formed 
by  a  ramifying  system  of  rectilinear  canals  wdth  very  thin  walls,  which 
open  into  each  other,  and  imite,  on  reaching  the  corpus  Highmori,  into 
about  twenty  principal  trunks.  These  are  named  the  straight  canaliculi  (rasa 
recta),  to  distinguish  them  from  the  convoluted  tubiili ;  they  receive  the 
latter  at  their  exit  from  the  lobules,  and  are  surrounded  by  numerous  blood- 
vessels and  sustained  by  the  fibrous  septa  of  the  tunica  albuginea,  which 
appear  to  converge  towards  the  point  they  occupy.  At  the  corpus  Highmori, 
the  vasa  recta  pass  through  that  body,  forming  in  its  texture  an  anasto- 
mosing network,  tlie  rete  testis,  and  are  continued  into  the  epididymis  as  the 
efferent  canals  (vasa  efferentia). 

The  seminiferous  tubes  in  the  lobules 
are  from  y^  to  the  yi^^  of  an  inch  in 
diameter.  They  are  composed  of  a 
very  thin  fibrous  membrane  (firmer 
than  that  in  the  walls  of  similar  gland 
canals  elsewhere) ;  slightly  elastic, 
and  made  up  of  connective  tissue 
with  longitudinal  nuclei,  this  mem- 
brane is  lined  internally  by  a  proper 
amorphous  membrane  {basement)  and 
epithelium.  The  latter  almost  com- 
pletely fills  the  tubuli ;  near  the  v/all 
of  the  canal  it  is  composed  of  polygonal 
cells,  but  towards  the  centre  these  in- 
crease in  volume,  become  circular  and 
transparent,  and  show  several  nuclei 
in  various  stages  of  transformation ; 
finally,  in  the  axes  of  the  tubuli  can 
be  perceived  sjiermatozoa  and  the 
detritus  of  the  spermatic  cells. 

Vessels  and  nerves. — The  blood  is 
carried  to  the  testicle  by  the  spermatic 
artery,  which  is  almost  exclusively 
appropriated  to  it ;  this  vessel,  after 
describing  a  great  number  of  very 
remarkable  flexions,  enters  the  upper  vertical 
border  of  the  gland,  a  little  behind 
the  epididymis.  It  does  not  imme- 
diately plunge  into  its  substance,  how- 
ever, but  jiasses  within  the  textm*e  of 
the  tunica  albugioea,  along  the  borders 
of  the  testicle,  and  forms  a  complete 
circle  around  it.  From  this  circle  it 
sends  ofi"  divisions,  which  spread  over 
the  sides  of  the  organ,  detaching  fine 
arterial  ramifications  that  jjenetrate  its 
proper  tissue  in  accompanying  the  interlobular  septa.  (There  is  generally 
described  a  tunica  vasculosa  that  forms  one  of  the  coverings  of  the  testicle. 


section  of  the  testicle 
(horse's),  passing  through  the  corpus 
highmori. 
1,  Spermatic  cord,  with  its  serous  covering; 
2,  Sections  of  the  flexuous  vessels  of  the 
cord  ;  3,  Head  of  the  epididymis,  or  globus 
major ;  4,  Tail  of  the  epididymis,  or  globus 
minor ;  5,  Yas  deferens ;  6,  Corpus  High- 
mori ;  7,  Eete  testis ;  8,  Tunica  albuginea 
sending  prolongations  from  its  inner  face, 
and  which  divide  the  testicle  into  lobules ; 
9,  Surface  of  the  ttinica  albuginea. 


856  TEE  GENERATIVE  APPARATUS. 

This,  in  reality,  is  not  a  distinct  coat,  but  merely  the  fine  ramifications  of 
the  spermatic  artery  spreading  beneath  the  tunica  albuginea,  and  held 
together  by  delicate  cellular  tissue,) 

The  veins  are  very  voluminous  and  freq^uently  varicose,  and  comport 
themselves  like  the  arteries ;  they  unite  in  a  single  trunk  that  enters  the 
posterior  vena  cava,  near  the  renal  veins.  (On  the  cord,  in  addition  to  their 
sometimes  varicose  condition,  the  spermatic  veins  have  been  observed  to 
form  a  network,  named  the  pampiniform  plexus?) 

The  lymphatics  are  most  numerous  beneath  the  serous  layer  and  the 
tunica  albuginea.  They  commence  in  the  lacunae  between  the  seminal  tubes 
and  vessels,  and  terminate  in  the  sublumbar  glands. 

The  nerves  of  the  testicle  are  derived  from  the  sympathetic  (and  pass 
from  the  abdomen  with  the  blood-vessels)  ;  they  form  a  small  particular 
plexus  around  the  artery.  (The  nerves  pierce  the  membrana  propria  of  the 
tubuli  seminiferi,  and  end  in  a  more  or  less  pyramidal  mass  of  protoplasm, 
in  which  lie  clear  elliptical  nuclei.  The  ends  of  the  fibres,  therefore,  lie 
in  close  proximity  to  the  outer  layer  of  secreting  cells.) 

Development, — In  the  foetus,  at  an  early  age,  the  testicle  floats  in  the 
abdominal  cavity,  being  suspended  from  the  sublumbar  region,  near  the  flank, 
by  a  wide  peritoneal  fold,  at  the  anterior  border  of  which  are  the  spermatic 
vessels  (Fig,  399,  e.) ;  the  tunica  vaginalis  is  not  yet  present.  The 
mechanism  of  the  formation  of  this  is  very  simple,  and  easy  to  understand. 
The  visceral  layer  of  the  tunica  vaginalis,  which  envelops  the  testicle  and 
the  cord,  being  already  formed,  as  well  as  the  serous  fraenum  that  establishes 
continuity  between  this  and  the  parietal  layer  in  the  adult  animal,  it  only 
remains  to  explain  how  nature  proceeds  to  construct  the  vaginal  sac  in  which 
the  gland  is  afterwards  contained. 

We  have  remarked,  that  to  the  posterior  extremity  of  the  testicle  is 
attached  a  thick  round  funicle,  the  other  end  of  which  passes  into  the  upj)er 
inguinal  ring,  being  enveloped  by  the  peritoneum,  and  fixed  to  the  posterior 
border  of  the  serous  layer  that  suspends  the  testicle.  This  funicle  is  the 
guhernaculum,  testis,  and  is  continuous,  by  its  inguinal  extremity,  with  the 
dartos,  whose  structure  it  ai)parently  shares,  and  which  alone  acts  as  the 
scrotal  sac  to  it.  The  serous  layer  covering  it  has  on  its  outer  adherent 
face  the  cremaster  muscle,  which  is  attached  to  the  ilio-lumbar  aponeurosis 
in  the  vicinity  of  the  inguinal  ring,  enters  the  serous  tube  formed  by  the 
peritoneal  envelope  of  the  guhernaculum,  and  advances  by  its  terminal 
extremity  to  near  the  testicle.  To  this  organ  is  due  the  principal  share  in 
the  formation  of  the  vaginal  pouch. 

When  the  progress  of  development  in  the  foetus  pushes  the  testicle 
towards  the  inguinal  region,  the  guhernaculum  acts  as  a  guide,  as  its 
picturesque  name  sufficiently  indicates.  It  is  the  first  to  descend  into  the 
inguinal  opening,  drawing  the  testicle  after  it.  But  in  performing  this 
movement  it  also  carries  along  its  peritoneal  covering,  which  gradually 
leaves  it  to  become  related,  by  its  adherent  face,  to  the  walls  of  the 
inguinal  canal ;  and  thus  this  membrane  becomes  reflected,  just  as  would  a 
sock  everted  or  turned  down  from  the  leg  to  the  foot,  the  latter  being 
suj)i)osed  to  represent  the  testicle. 

The  parietal  layer  of  the  vaginal  sac  is,  then,  nothing  more  than  the 
serous  tube  that,  in  the  foetus,  enveloped  the  guhernaculum  testis  while  in 
the  abdomen,  and  which  is  reversed  on  the  testicle  and  cord  after  their 
descent  into  the  scrotum,  the  cremaster  muscle  on  its  adherent  face  having 
become  external. 


THE  MALE  GENITAL  ORGANS. 


857 


In  all  species,  the  descent  of  the  testicle  commences  hefore  birth  :  in  the 
Bovidje  it  is  even  achieved  in  the  early  months  of  intra-iiterinc  existence. 
In  Solipeds,  however,  the  testicle  most  frequently  remains  in  the  inguinal 
canal  until  the  animal  is  from  six  to  ten  months  old. 


Fig.  399. 


raE   INTERNAL  GENITO-TTRINARY  ORGANS,   WITH  THE   STOMACH,   LIVER,   AND  SPLEEN, 
IN    THE    FCETUS   OF    A    MARE. 

R,  Left  kidney ;  v,  Bladder ;  T,  Testicle ;  at.  Spermatic  artery  ;  G,  Gubernaculum 
testis ;  e,  Epididymus — the  letter  is  placed  in  the  centre  of  the  serous  layer  which 
suspends  the  testicle  and  spermatic  vessels  from  the  siiblumbar  region,  and  after 
the  descent  of  the  gland,  forms  the  frasnum  between  the  two  layers  in  the  vaginal 
sheath;  e,  Stomach;  F,  Liver;  /,  Lobus  Spigelii ;  P,  Vena  portaj ;  c,  Umbilical 
cord  ;  o,  Umbilical  vein  ;  o',  Intrahepatic  course  of  that  vein,  indicated  by  a  double 
dotted  line. 

Function. — The  testicles  secrete  the  spermatic  (or  seminal)  fluid.    Pure 
semen,  such  as  is  derived  from  these  glands,  is  a  white,  viscid,  odorless. 


858 


THE  GENERATIVE  APPARATUS. 


and  slightly  alkaline  fluid.  It  contains  a  small  quantity  of  liquid  matter 
(liquor  seminis),  in  which  is  an  innumerable  mass  of  spermatozoa.  After 
the  semen  has  passed  through  the  genital  canals,  it  is  made  much  more 
aqueous  by  the  addition  of  the  fluids  secreted  by  the  walls  of  these  excretory 
ducts,  or  by  the  glands  annexed  to  them. 

The  spermatozoa,  zoosperma,  spermatozoides,  or  spermatic  filaments,  are 
little  elongated  bodies  from  -^^  to  ^f^  of  a  line  in  length.  They  have  a 
pyriform,  flattened,  or  lancet-shaped  head,  and  a  filiform  tail  terminating  in 
a  point ;  this  tail  is  often  furnished  at  its  origin  with  an  enlargement,  or 
unilateral  or  bilateral  alae.  Their  form  is  slightly  modified  during  their 
course  through  the  excretory  ducts.  (In  the  difierent  species,  though 
possessing  certain  fixed  characters,  the  spermatozoa  yet  oifer  some  curious 
diversities.  Some  of  these  are  well  exhibited  in  the  annexed  representations 
of  these  particles,  found  in  the  semen  of  very  dissimilar  animals.) 

The  spermatozoa  move  by 
Fig.  400.  undulations  of  the  tail  (Grohe 

attributes  the  motion  to  the 
contractile  protoplasm  con- 
tained in  the  head).  Their 
movements  persist  for  several 
days  in  the  genital  organs  of 
the  female  ;  they  are  suddenly 
arrested  by  water,  acids,  and 
the  electric  spark;  on  the 
contrary,  they  are  animated 
by  alkaline  fluids.  (The 
movements  cease  when  the 
spermatozoa  are  exposed  to  a 
temperature  of  120^  Fahren- 
heit.) These  bodies  are  de- 
veloped in  the  cells  of  the 
tubuli  seminiferi  by  a  modi- 
fication of  their  contents. 
The  cells  (vesicles  of  evo- 
lution) become  round  in  the 
centre  of  these  canals,  and 
have  from  one  to  ten  nuclei ; 
the  latter  are  elongated,  and  throw  out  a  prolongation  that  gradually 
extends  and  forms  the  tail  of  the  spermatozoon.  When  all  the  nuclei  are 
thus  transformed,  the  cell-wall  ruptures  and  liberates  the  spermatozoa,  which 
swim  about  in  the  minute  quantity  of  fluid  resulting  from  the  destruction  of 
the  cells. 


/ 


,  Spermatozoon  of  the  frog ;  2,  Of  the  triton 
the  finch ;  4,  Of  the  field-mouse ;  5,  Of  the 


;  3,  Of 

hedge- 


hog ;   6,  Sheep ; 
c.  Tail. 


Head  with  nucleus  ;    6,  Body  ; 


EXCRETORY    APPARATUS   OF   THE    SEMEN. 

1.  The  Epididymis  and  Deferent  Canal.     (Figs.  397,  398,  399,  401,  402.) 
Epididymis. — The  organ  thus  named  commences  the  excretory  canal  of 
the  testicle.     It  is  a  body  elongated  from  before  to  behind,  placed  against 
the  upper  border,  and  a  little  to  the  outside,  of  the  spermatic  gland.     It  has 
a  riiiddle  portion  and  two  extremities. 

The  middle  is  contracted,  flat  on  both  sides,  and  free  outwardly ;  it  is 
related,  inwardly,  to  the  spermatic  vessels  and  the  testicle,  to  which  it  is 
attached  by  a  very  short  serous  layer.  The  extremities  are  expanded,  and 
adhere  intimately  to  the  testicle.     The  anterior,  the  largest,  is  named  the 


THE  MALE  GENITAL  ORGANS. 


859 


Fis;.  401. 


head  of  the  epididymis  or  globus  major.  The  posterior,  the  tail  of  the  epidi- 
dymis, or  globus  minor,  is  more  detached  from  the  testicle,  and  is  curved 
upwards  to  be  ct)utinued  by  the  deferent  canal  (vas  deferens). 

Structure. — The  epididymis  is  constituted  by  a  long  duct  doubled  a 
great  number  of  times  on  itself,  and  whose  convolutions,  after  injection  with 
mercury,  can  be  very  readily  seen  through  the  serous  membrane.  This 
duct  results  from  the  union  of  from  twelve  to  twenty  small  tubes,  the 
efferent  ducts,  v,']iich,  arising  from  the  rete  testis,  open  together,  at  a  variable 
distance,  into  the  globus  major.  Towards  the  globus  minor  there  is  only 
one  duct,  which  is  more  voluminous  and  less  flexuous,  and  finishes  by 
becoming  detached  from  the  posterior  lobe  of  the  epididymis  to  constitute 
the  vas  deferens. 

The  organisation  of  the  walls  of  these  ducts  is  not  the  same  throughout. 
Thus,  in  the  efferent  ducts,  it  comprises  a  simple  ciliated  epithelium,  resting 
on  a  proper  amorphous  membrane,  which  again  is  placed  on  unstripcd 
circular  fibres  attached  to  a  thin  fibrous  tunic ;  u  hile  beyond,  there  is 
observed  a  stratified  ciliated  epithelium,  a  proper  membrane,  two  layers  of 
unstriped  fibres — circular  and  longitudinal — and  also  a  fibrous  tunic.  The 
thickness  of  the  muscular  layers  increases  from  before  to  behind. 

The  epididymis  receives  its  arteries  and  nerves  from  the  same  sources 
as  the  testicle. 

Deferent  Canal  (vas  deferens). — This  duct  is  about  the  thickness  of  a 
goose-quill,  and  is  at  first  flexuous,  then 
straight.  It  lies  parallel  with,  but  behind 
and  to  the  inner  side  of,  the  spermatic  vessels, 
as  far  as  the  opening  of  the  tunica  vaginalis ; 
passing  through  this  opening,  it  enters  the 
pelvic  cavity,  and  crosses  obliquely  the  ureter 
and  obliterated  cord  of  the  umbilical  artery. 
It  is  then  inflected  backwards,  placed  above 
the  bladder,  suddenly  dilates,  and  is  prolonged 
as  far  as  the  neck  of  that  reservoir,  where  it 
terminates ;  after  having  penetrated  beneath 
the  prostate  gland  by  a  sudden  contraction, 
at  the  origin  of  which,  and  outwardly,  the 
vesicula  seminalis  opens,  and  is  continued 
by  the  ejaculatory  ducts. 

The  vas  deferens  is  sustained  in  the 
tunica  vaginalis  by  a  very  short  serous  fold, 
a  dependency  of  the  fraenum,  whose  two  lay- 
ers envelope  the  spermatic  vessels,  within 
and  behind  which  this  duct  is  situated.  In 
the  abdominal  cavity,  it  is  fixed  by  the  pro- 
longation of  this  serous  duplicature.  Its 
dilated  or  pelvic  portion  is  in  contact, 
superiorly,  with  the  vesicul^e  seminales,  and 
is  finally  united  to  its  dilated  homologue  of  the  opposite  side,  which  it 
has  been  gradually  approaching,  by  means  of  a  triangular  peritoneal  fold, 
that  comprises  between  its  two  layers  a  small  club-shaped  cavity  which 
will  be  alluded  to  again. 

The  calibre  of  the  vas  deferens  is  very  small  in  its  vaginal  and  abdo- 
minal portions,  but  is  greater  towards  the  pelvic  dilatation,  where  the  walls 
of  the  duct  ofler  a  well-marked  areolated  disposition. 


diagram  of  the  testicle 
(human). 
1,  Mediastinum  testis,  containing 
the  rete  testis  ;  2,  2,  Trabeculi ; 
3,  One  of  the  lobules ;  4,  4,  Vas 
recta ;  5,  Globus  major  ;  6,  Globus 
minor;  7,  Vas  deferens. 


860 


THE  GENERATIVE  APPARATUS. 


Steuctuee. — Tlie  vas  deferens  is  formed,  internally,  by  a  very  fine 
mucous  membrane  covered  with  cylindrical  ej)itbelium,  and  to  this  is  added, 
externally,  a  contractile  and  a  fibrous  tunic.  The  contractile  layer  is  formed 
of  three  planes  of  unstriped  fibres :  the  deep  and  superficial  planes  have 
longitudinal,  and  the  middle  circular  fibres.  It  is,  proportionately,  very 
thick  at  the  dilated  portion  of  the  duct,  and  it  is  to  its  great  density  that 
the  vas  deferens  owes  its  consistence  as  a  hard,  rigid  cord.  The  mucous 
membrane  of  the  jielvic  dilatation  has  tubular  and  acinous  glands. 


S- 


2.  The  Vesiculce  Seminales  and  Ejaculatory  Ducts.    •(Fig.  326.) 

The  vesiculcB  seminales  are  two  oval  pouches  whose  volume  varies  witli 
Fig.  402.  their  contents,  and  which  are  placed  in  the 

pelvic  cavity,  above  the  bladder  and  the  vas 
deferens.  Each  vesicula  has  a  middle  portion 
and  tico  extremities.  The  middle  portion  is 
enveloped  by  a  loose  abundant  cellular 
tissue,  and  is  in  relation  with  the  rectum 
above,  and  below  with  the  bladder  and  vas 
deferens. 

The  anterior  e.xtremity  is  the  largest, 
and  forms  a  rounded  cul-de-sac,  covered  in 
almost  the  same  manner  as  the  bladder  by 
the  peritoneum,  which  at  this  point  fur- 
nishes a  very  small  triangular  frsenum  (the 
recto-vcsical  fold)  tliat  unites  the  two  vesi- 
culfe.  The  posterior  extremity  tapers  to  a 
narrow  neck,  which  passes  beneath  the  pros- 
tale  gland,  and  joins  at  a  very  acute  angle 
the  terminal  extremity  of  the  vas  deferens, 
to  constitute  the  ejaculatory  duct. 

The  w'alls  of  this  pouch  are  composed 
of  three  membranes  :  an  internal  mucous,  a 
middle  musctdar,  and  an  external  fibrous. 
The  mucous  layer  is  continuous  with  that 
of  the  ejaculatory  ducts,  and  is  very  thin, 
delicate,  and  follicular.  It  shows  numerous 
folds,  which  disaj^pear  with  distention  of  the 
duct.  The  middle  layer  evidently  belongs 
to  the  class  of  muscular  membranes ;  its 
identity  with  that  of  the  bladder  is  complete. 
1,  Left  vas  deferens;  1',  Its  pelvic  At  the  bottom  of  the  cul-de-sac  it  gives  off 
dilatation;  2   2   The  same  on  the    ggveral  fasciculi,  which  radiate  on  the  ex- 

ricrht  side ;  d,  4,  VesiculEe  seminales ;     ,  ■,  p  j.  ,  i  •■  /t        i  t 

5,  The  third  vesicula;   6,  Serous   vernal  surface  of  the  peritonemn.     (In  addi- 

layer  uniting   the  vasa   deferentia ;    tioD    to    these,   the  vesiculte   and   Vasa   defe- 

7,  That  comprised  between  the  two  rentia  have  a  muscular  covering  whose  fibres 

yesiculae;    8,    Prostate    gland;    9,  q^q  arranged  in  a  longitudinal  and   trans- 

I'dadder   seen   through    the    serous  t        x-         xi       i  li        -u   •         ii               l 

i-r-\A   ..e  +1,..     „  „   /^  „^+-„      1A  verse  direction,  the  latter  being  the  most 

told    or    the   vasa    dererentia ;    10,  .           mi  •                 i       i           i     • 

Membranous  or  intrapelvic  portion  Superficial.     This  inuscular  layer  being  con- 

of  the  urethral  canal,  covered  by  tinuous  over  the  vesiculiB  seminales  and  vas 

Wilson's  muscle;  11,  11,  Cowper's  deferens,   when  it  contracts,  will  compress 

glands  enveloped  by  that  muscle;  and  shorten  these  ;  consequently,  it  has  been 

12,    12,    Ischio-cavernosus   muscle;  -i     ,^                                       •     -f         ,     t     , 

13  Accelerator  urince  muscle.  named   the    compressor    vesiculce    ct  ductus 


SUPERIOR  VIEW  OF  THE  PELVIC  POR- 
TION OP  THE  VASA  DEFERENTIA, 
VESICULA  SEMINALES,  PROSTATE 
GLAND,  cowper's  GLANDS,  AND  THE 
INTRAPELVIC  PORTION  OP  THE 
URETHRA. 


THE  MALE  GENITAL  ORGANS.  861 

seminalis.  The  fibrous  coat  of  the  vesicnhTe  is  merely  condensed  cellular 
tissue.)  The  mucous  and  muscular  ct)ats  arc  supplied  with  blood  by  the 
vesico-prostatic  artery  (inferior  vesical)  ;  their  nerves  are  derived  from  the 
pelvic  plexus. 

The  richness  in  glands  of  the  mucous  membrane  of  the  vesiculae 
seminales,  has  led  several  anatomists  to  consider  them  as  organs  of  secretion, 
and  not  as  reservoirs  for  the  semen.  But  the  large  cavity  that  each  forms, 
appears  to  demonstrate  that  they  serve  as  reservoirs  and  secretory  organs  at 
the  same  time.  Their  fluid  production  is  added  to  the  semen,  as  is  the 
secretion  of  the  pi'ostate  and  Cowper's  glands. 

The  ejaculatory  duct  is  very  short,  and  succeeds  the  narrow  canal  of  the 
vesicula  after  the  latter  opens  into  the  vas  deferens.  The  two  ducts  pass 
between  the  prostate  gland  and  urethra,  and,  after  a  brief  course,  terminate 
in  the  latter,  on  the  side  of  the  veru  montanum—a  tubercle  which  will  be 
noticed  presently. 

Near  to.  and  in  front  of  this  tubercle,  is  a  third  very  small  orifice — the 
opening  of  the  third  pouch  included  between  the  serous  duplicatures  joining 
the  vasa  defereutia.  (This  is  the  sinus  pocidaris,  or  utricidus  prostatia, 
vesicula  seminalis  tertia  or  media  of  Gurlt.)  Improperly  designated  the 
third  vesicula,  or  masculine  uterus  (Weber),  this  pouch  (sometimes  double) 
secretes  a  fluid  which  is  thrown  into  the  urethra.  (This  third  vesicula  is 
present  in  all  the  domesticated  animals.) 

The  ejaculatory  ducts  may  become  obliterated ;  then  the  secretion  of  the 
vesiculaa  seminales  accumulates  in  their  interior,  and  gradually  distends 
them  until  they  attain  enormous  dimensions.  We  foimd,  in  a  Gelding,  a 
vesicula  which  was  nearly  as  large  as  the  bladder ;  it  contained  a  brownish, 
sticky  fluid,  holding  in  suspension  epithelial  cells,  free  nuclei,  and  mucus 
corpuscles. 

(The  vesiculfe  seminales,  in  addition  to  their  own  secretion,  receive  the 
semen  conveyed  by  the  spermatic  ducts,  and  keep  it  in  reserve  until 
copulation  ;  when  the  contraction  of  its  muscular  apparatus  expels  it  into  the 
ejaculatory  ducts,  and  from  these  into  the  urethral  canal.) 

3.   The  Urethra. 

The  urethra  is  a  canal  with  membranous  and  erectile  walls,  commencing 
at  the  neck  of  the  bladder,  and  terminating  at  the  fi*ee  extremity  of  the  penis. 

Course. — When  followed  from  its  origin  to  its  termination,  it  is  seen  to 
proceed  at  first  horizontally  backwards,  then  bend  downwards  at  the  ischial 
arch  tQ  leave  the  cavity  of  the  pelvis,  placing  itself  between  the  two  roots  of 
the  corpus  cavernosum,  and  passing  forward  in  the  channel  formed  at  the 
lower  border  of  these,  until  it  arrives  at  the  head  (glans)  of  the  penis,  where 
it  terminates  by  forming  a  small  (cylindrical)  prolongation,  named  the 
urethral  tube.  In  its  track,  the  urethra  is  divided  into  two  very  distinct 
portions :  the  intrapelvic,  the  shortest,  and  the  extrapelvic,  the  most  ex- 
tensive, and  supported  by  the  corpora  cavernosa.  The  latter  division  being 
alone  enveloped  by  the  erectile  tissue  that  enters  into  the  formation  of  the 
urethral  walls,  has  been  also  named  the  spongy  portion,  the  first  being 
designated  the  membranous  portion. 

Interior. — Internally,  this  canal  has  not  the  same  width  throughout. 
Very  constricted  at  its  origin,  towards  the  neck  of  the  bladder,  it  expands 
somewhat  suddenly  at  the  prostate  gland ;  its  dilatation,  improperly  named 
in  Man  the  cul-de-sac  of  the  bulb  {bulbous  portion),  or,  better,  the  ventriculus. 


862  TEE  GENERATIVE  APPAEATUS. 

extends  to  its  curve  over  the  ischial  arch,  where  it  gradually  contracts. 
After  this  it  preserves  the  same  reduced  dimensions  throughout  its  course, 
though  these  dimensions  may  be  increased  during  the  passage  of  the  urine 
or  semen.  There  is,  however,  behind  the  urethral  tube  a  small  oval 
dilatation,  named  the  fossa  navicularis  (Fig.  403).  Even  throughout  its 
extrapelvic  portion,  the  inner  surface  of  the  urethra  offers,  near  the  neck  of 
the  bladder,  and  on  its  upper  wall,  the  excretory  orifices  of  the  prostate  gland, 
and  which  form  two  lateral  lines  of  minute  perforated  tubercles.  Between 
these  two  lines  is  found  the  urethral  ridge  or  veru  montanum  {cafput  gal- 
linaginus),  a  little  eminence  elongated  from  before  to  behind,  on  the  sides  of 
which  tlie  ejaculatory  ducts  open.  Behind  this  are  the  excretory  orifices 
of  Cowper's  glands. 

Relations. — The  intrapelvic  portion  of  the  urethra  is  in  relation,  above, 
with  the  prostate,  which  adheres  closely  to  it,  and  with  the  rectum,  to 
which  it  is  united  by  the  abundant  loose  connective  tissue  in  this  part  of  the 
pelvis  ;  below,  it  lies  on  the  internal  obturator  muscle ;  laterally,  it  is  related 
to  the  muscles  and  ligamentous  or  aponeurotic  expansions  that  close  in  the 
sides  of  the  pelvis.  Without  the  pelvic  cavity,  the  urethra  is  united  in  the 
most  intimate  manner  to  the  corpora  cavernosa,  wliicli  embrace  its  anterior 
border.  Bj  its  posterior  border,  it  is  related  to  the  suspensory  ligament  of 
the  penis. 

Structure. — The  urethra  is  composed  of :  1,  Mucous  membrane  ;  2,  An 
erectile  envelope;  3,  Muscles;  4,  Vessels  and  nerves;  and,  5,  we  will  add 
some  remarks  concerning  the  perineal  aponeuroses,  which  are  in  immediate 
relations  with  this  canal. 

1.  Mucous  Membrane. — This  is  rather  delicate,  and  forms  the  lining  of 
the  canal ;  it  is  continuous,  posteriorly,  with  that  of  the  bladder,  and  in 
front  with  the  integument  enveloping  the  head  (glans)  of  the  penis  ;  it  is  also 
prolonged  into  the  excretory  ducts  of  the  glands  annexed  to  the  urethra  and 
the  ejaculatory  ducts.  It  has  longitudinal  folds,  and  is  always  in  contact 
with  itself,  except  during  the  passage  of  urine  or  semen ;  it  has  scarcely  any 
papillae,  only  a  few  being  found  near  the  anterior  extremity  of  the  canal. 

The  epithelium  of  this  membrane  is  stratified  and  cylindrical,  but  at  the 
portion  furnished  with  papillte  it  becomes  pavemental. 

2.  Erectile  Envelope, — This  envelope,  lying  outside  the  mucous  mem- 
brane, does  not  cover  the  intrapelvic  portion  of  the  canal.  It  commences  a 
little  above  the  ischial  contour,  behind  Cowper's  glands,  by  a  very  thick 
bulging  portion,  named  the  hulb  of  the  urethra.  In  front,  it  terminates  by 
another  bulbous  enlargement,  into  which  the  anterior  extremities  of  the 
corpora  cavernosa  enter,  named  the  head  of  the  penis  (glans  penis). 

The  tissue  composing  this  envelope  has  the  same  organisation  as  other 
erectile  apparatus,  being  a  network  of  communicating  cavities  separated  by 
elastic  septa,  the  latter  showing  in  their  structure  some  contractile  elements. 

3.  Muscles. — Behind  the  prostate  gland,  the  mucous  membrane  of  the 
urethra  is  covered  by  a  fleshy  layer  of  circular  fibres,  forming  Wilsoii's 
muscle.  Another  muscular  envelope,  constituting  the  bidbo-cavernous  or 
accelerator,  also  covers  the  erectile  tissue  of  the  m'ethra,  accompanying  it  to 
near  the  glans,  where  it  gradually  disajipears.  To  these  two  princii)al 
muscles  of  the  urethra  are  added  two  pairs  of  secondary  fasciculi — the 
iscliio-urethral  and  transversus  perinei.  This  is  the  description  of  the 
muscular  apparatus : 

a.  Wilsons  muscle. — This  may  be  described  as  a  single  muscle  com- 
posed of  two  portions,  an  inferior  and  superior.      Both   are   formed  by 


THE  MALE  GENITAL  ORGANS.  863 

transverse  fibres  thrown  over  the  membranous  portion  of  the  urethra,  and 
united  at  their  extremities,  which  are  attached  by  means  of  aponeurotic 
fasciculi,  to  the  hiteral  walls  of  the  pelvis.  Behind,  the  superior  fibres 
cover  Cowper's  glands,  and,  like  the  inferior,  are  mixed  with  the  accelerator 
urinje. 

h.  Accelerator  Urrnce. — Composed  of  transverse  fibres  encircling  the 
urethra  from  the  ischial  arch  to  the  free  extremity  of  the  penis,  this  will  also 
be  studied  as  a  single  organ,  separated  into  two  lateral  portions  by  a  median 
raphe  passing  along  the  whole  posterior  face  of  the  m-ethra.  The  fibres  jiass 
from  this  raphe  to  the  right  and  left,  enter  the  furrow  of  the  corpora 
cavernosa,  and  reach  the  upper  surface  of  the  urethra,  where  they  advance 
towards  each  other ;  they  do  not  join ;  so  that  the  circle  formed  by  this 
muscle  is  necessarily  incomplete. 

c.  IscMo-iiretliral  muscle  (compressor  urethrce). — This  is  a  thin  fleshy 
band,  pair,  situated  below  and  at  the  side  of  the  membranous  portion  of  the 
ui'ethra.  Attached  by  some  aponeurotic  fibres  to  the  ischial  arch,  this 
muscle  passes  forward  on  Cowper's  gland,  whose  lower  face  it  covers.  At 
the  periphery  of  that  organ,  it  is  confounded  with  the  portion  of  Wilson's 
muscle  that  envelops  its  upper  surface. 

d.  Transversus  perinei. — Tliis  is  a  very  thin  ribbon-like  fasciculus,  often 
scarcely  distinguishable  from  the  ischio-anal  muscle  [levator  ani).  It 
extends  transversely  from  the  ischial  tuberosity — to  which  it  is  attached 
through  the  medium  of  the  sacro-sciatic  ligament,  to  the  mesial  line  of  the 
perineum,  where  its  fibres,  confounded  with  those  of  its  homologue  on  the 
opposite  side,  appear  to  be  inserted  in  the  accelerator  urinfe  at  its  origin. 

e.  Action  of  the  urethral  muscles. — 1.  Wilsons  muscle,  when  it  contracts, 
compresses  between  its  two  layers  the  membranous  portion  of  the  urethra. 
It  is  a  veritable  sphincter,  and  opposes  the  escape  of  the  urine ;  when  the 
semen  is  thrown  from  the  vesiculfe  seminales  into  the  urethra,  it  also 
prevents  that  fluid  entering  the  bladder,  by  permitting  the  accelerator  to 
empty,  from  before  to  behind,  the  initial  dilatation  of  that  canal.  2.  The 
accelerator  is  correctly  named  from  the  jiart  it  plays  in  ejecting  the  semen 
from  the  urethra,  it  being  the  chief  agent  in  this  act.  3.  The  ischio-urethral 
muscle  pulls  back  the  membranous  portion  of  the  urethra,  with  Cowper's 
glands,  and,  like  Wilson's  muscle,  acts  as  a  compressor  to  these.  4.  The 
transversus  perinei  dilates  the  bulbous  portion  of  the  uretkra,  by  drawing  it 
out  laterally. 

4.  Vessels  and  Nerves. — The  urethra  is  supplied  with  blood  by  the 
bulbo-urethral  arteries  and  the  two  pairs  of  arteries — the  dorsal  of  the  penis. 
Voluminous  veins,  frequently  varicose,  and  satellites  of  the  arteries,  carry  it 
away.  The  hjmphatics  form  a  very  rich  plexus  beneath  the  mucous 
membrane ;  their  trunks  pass  to  the  inguinal,  and  some  to  the  sublumbar 
glands.  The  nervous  filaments  are  from  the  internal  pudic  and  great 
sympathetic. 

5.  Aponeuroses  of  the  Perineum. — In  the  perineal  region,  the  lU'ethra 
is  covered  by  two  superposed  fibrous  layers.  The  superficial  aponeurosis  is 
fibro-elastic,  and  appears  to  arise  from  the  inner  surface  of  the  thighs, 
where  it  is  mixed  with  the  dartos ;  it  covers  the  perineum,  and  its  fibres, 
becoming  disassociated,  disappear  on  the  sides  of  the  sphincter  ani.  This 
membrane  is  in  relation,  externally,  with  the  skin,  and,  internally,  with  the 
deep  aponeurosis.  On  the  middle  of  its  external  face,  it  receives  the 
insertion  of  a  muscular  fasciculus,  which  is  detached  from  the  sphincter. 

The  deep  aponeurosis,  formed  of  white  inelastic  fibrous  tissue,  adheres  to 


864  THE  GENEBATIVE  APPARATUS. 

tlie  latter  by  its  outer  face,  and  to  tlie  accelerator  and  ischio-cavernous 
muscles  by  its  inner  face.  Above,  it  is  lost  around  the  termination  of  tbe 
rectum ;  below,  it  expands  between  the  thighs ;  it  is  seen  insinuating  itself, 
to  the  right  and  left,  between  the  ischio-cavernous  and  semimembranosus 
muscles,  to  be  attached  to  the  ischiatic  tuberosity. 

4.  The  Glands  annexed  to  the  Urethra. 

A.  Prostatk  (Fig.  402,  8)  — This  single  and  symmetrical  gland  is 
situated  at  the  commencement  of  the  urethra,  and  lies  across  the  neck  of  the 
bladder.  A  constriction  in  the  middle  divides  it  into  two  voluminous 
lateral  lobes  inclining  slightly  forward.  Its  upper  face  corresponds  to  the 
rectum,  through  the  medium  of  the  cellular  tissue  at  the  bottom  of  the 
pelvic  cavity.  Its  inferior  face,  moulded  on  the  neck  of  the  bladder, 
embraces  it  above  and  laterally,  and  is  closely  attached  to  it ;  it  covers  the 
terminal  extremity  of  the  deferent  and  ejaculatory  ducts,  and  the  neck  of 
the  vesiculae  seminales. 

Structure.— The  tissue  composing  this  gland  forms  a  number  of 
communicating  cells,  which  are  larger  in  the  Ass  than  the  Horse ;  in  these 
is  collected  a  quantity  of  viscid  fluid  (succus  p-ostaticus)  secreted  by  their 
walls,  and  which  is  ejected  into  the  urethra  by  the  two  rows  of  orifices 
arranged  on  the  sides  of  the  veru  montanum.  These  communicating  cells 
are  nothing  more  than  conglomerate  glands,  which  are  distributed  in  a 
stroma  of  connective  tissue  and  unstriped  muscular  fibres. 

B.  Cowper's  Glands. — In  Veterinary  anatomy,  these  are  frequently 
named  the  small  prostates.  They  are  two  globular  bodies,  denser  in  texture 
than  the  prostate  gland,  but  otherwise  the  same  in  organisation,  and  are 
situated  on  each  side  of  the  urethra,  in  the  perineal  region,  above  the  ischial 
arch ;  they  are  completely  enveloped  by  a  somewhat  thick  fleshy  cover- 
ing, formed  by  the  fibres  of  Wilson's  and  the  ischio-urethral  muscles 
(Fig.  402,  11). 

The  fluid  they  secrete  is  thrown  into  the  urethral  canal  by  numerous 
orifices  disposed  in  several  rows.  It  has  the  same  physical  properties  as 
that  of  the  prostate,  and  both  are  poujed  into  the  urethra  in  abundance 
immediately  before  ejaculation ;  the  expulsion  of  the  semen  is  by  this 
means  facilitated. 

5.  The  Corpus  Cavernosum. 

The  corpus  cavernosum  is  an  erectile  stalk,  which  forms  the  base  of  the 
penis  and  supports  the  urethra ;  it  is  situated  between  the  thighs,  prolonged 
beneath  the  abdomen,  attached  behind  to  the  ischial  arch,  and  terminates  in 
front  by  a  free  extremity,  which  is  received  into  the  erectile  enlargement 
named  the  glaus  penis. 

External  conformation. — Flattened  on  both  sides,  this  body  offers  for 
study  two  lateral  faces,  two  borders,  and  two  extremities.  The  faces  are 
plane,  and  present  no  interesting  features.  The  superior,  or  dorsal  border,  is 
the  thickest,  and  is  rounded.  The  inferior  is  channeled  throughout  its 
extent  by  a  deep  furrow  which  lodges  the  urethra.  The  posterior  extremity 
is  bifurcated,  the  two  branches  constituting  the  roots  (corpora  or  crura)  of  the 
penis  ;  they  are  fixed  to  the  ischial  arch,  one  to  the  right,  the  other  to  the  left, 
and  are  covered  by  the  two  ischio-cavernosus  (erector  penis)  muscles  :  short, 
thick,  and  strong  masses  intersected  by  numerous  tendinous  fibres,  and  partly 
concealed  by  the  semimembranosus  muscles.     These  erector  penis  muscles 


THE  MALE  GENITAL  ORGANS.  865 

arise  from  the  ischial  crest,  aud  terminate  on  the  memhrane  enveloping  the 
crura  of  the  penis,  which  they  cover  posteriorly  aud  externally. 

The  anterior  extremitij  of  the  corpus  cavernosum  forms  a  blunt  point,  and 
is  surrounded  by  the  spongy  tissue  of  the  glans. 

Mode  of  attachment  of  the  corpus  cavernosum. — The  chief  attachment  is 
constituted  by  the  insertion  of  the  two  crm-a  into  the  ischial  arch.  There  is 
also  a  double  suspensory  ligament  proceeding  from  the  ischio-jjubic  sym- 
physis, where  it  is  confounded  with  the  superior  attachments  of  the  short 
adductor  of  the  thigh,  and  passes  to  the  dorsal  border  of  the  corpus 
cavernosum,  a  little  in  front  of  the  point  of  union  of  its  crura. 

Structure. — This  erectile  organ  is  composed,  externally,  of  a  white, 
elastic,  fibrous  envelope,  remarkable  for  its  thickness,  especially  on  the 
dorsum ;  it  gives  oif,  from  its  inner  face,  a  certain  number  of  lamellar 
trabeculpB  which  partition  the  interior  of  the  cavity  it  forms.  One  of  these 
septa  (septum  j)ectiniform)  is  directed  vertically  from  the  upper  to  the  lovrer 
border,  and  divides  the  corpus  cavernosum  into  two  lateral  portions  (corpora 
cavernosa),  which  would  indicate  th;>t  the  crm'a  are  not  one  mass  at  their 
point  of  union,  but  merely  joined  to  each  other.  In  the  Horse,  this  sej^tum 
is  generally  very  incomi^lete,  and  rarely  extends  the  whole  length  of  the 
organ. 

The  lamellar  prolongations  sustain  other  elastic  and  contractile  bands, 
which  circumscribe  the  cavities  in  which  is  lodged  the  essential  portion  of 
the  erectile  tissue.  According  to  Legros,  the  latter  is  composed  of  a 
network  of  capillaries  interposed  between  the  arterial  aud  venous  twigs,  and 
which  shows  abrupt  or  regular  dilatations  of  variable  diameter.  These 
successively  dilated  capillaries  have  very  thin  walls,  which  are  adherent  to 
the  contractile  prolongations  of  the  envelope,  and  are  lined  by  a  very 
delicate  pavement  epithelium.  In  the  areolee  of  the  cavernous  tissue, 
particularly  towards  the  base  of  the  organ,  the  arteries  offer  a  special 
disposition ;  their  walls  are  very  thick,  and  they  soon  divide  into  a  bouquet  of 
branches  which  enter  the  areolfe,  where  they  terminate  either  by  a  cul-de- 
sac,  or,  which  is  most  frequent,  give  off  small  free  branches  convoluted  in  a 
spiral  manner.  These  are  the  arteries  helicincB  described  by  Miiller  and 
Eouget.  (The  walls  of  the  cells  are  composed  of  white  and  yellow  fibrous 
tissue,  and  unstriped  muscular  fibres.  The  cells  themselves  are  in  reality 
venous  sinuses.  Kolliker  found  a  minute  artery  to  proceed  from  each  of 
the  Cfecal  terminations  of  the  helicine  arteries,  and  terminate,  like  the  other 
capillaries,  in  the  veins.  The  dilated  vessels  have  been  regarded  by  some 
anatomists  as  only  vascular  loops.  The  cells,  during  the  erection  of  the 
penis,  are  distended  with  blood.) 

The  arteries  of  the  corpus  cavernosum  and  dorsales  penis  pass  into  the 
erectile  structui-e,  and  supply  this  organ  with  blood.  The  collateral  veins  of 
these  arteries  arise  near  the  sui'face.  The  nerves  come  from  the  internal 
pudic  and  great  sympathetic. 

6.  Tlie  Penis. 

The  penis  is  the  male  organ  of  copulation,  and  results  from  the  union  of 
the  corpus  cavernosum  and  the  spongy  portion  of  the  urethra.  These  parts 
have  already  been  described;  it  now  remains  to  consider  the  organ  in  its 
entirety. 

The  penis  commences  at  the  ischial  arch,  passes  between  the  thighs 
aud  the  two  dartoid  sacs  containing  the  testicles,  and  is  prolonged  beneath 
the  belly,  where  it  terminates  in  a  free  extremity. 


866 


THE  GENERATIVE  APPARATUS. 


¥is.  403. 


All  the  portion  comprised  between  the  ischial  arch  and  the  scrotum,  is 
maintained  and  deeply  covered  by  the  surrounding  textui-es,  and  is  named 
the  fixed  portion  of  the  penis.  The  remainder  of  the  organ — its  anterior 
moiety — is,  on  the  contrary,  its  free  portion,  as  it  forms  a  detached  appendage 
sustained  by  a  cutaneous  fold,  the  slieath  (ot  prepuce). 

The  Fixed  Poetion  occupies  the  perineal  region  and  that  between  the 
thighs,  where  it  is  enveloped  by  the  arteries,  veins,  and  nerves  already 
known,  as  well  as  by  a  large  quantity  of  connective  tissue  (and  the  skin). 

The  Feee  Portion  is  lodged  in  the  sheath  during  the  inactive  condition 
of  the  organ,  but  protrudes  from  it  when  in  a  state  of  erection.  It  is  then 
seen  to  be  covered  by  a  smooth,  unctuous  tegumentary  membrane  with 
numerous  papillae,  and  of  variable   colour,    though   most   frequently  it   is 

black  or  variegated.  Its 
hase  presents  a  slight  circular 
enlargement,  due  to  the  ac- 
cumulation, beneath  the 
mucous  membrane,  of  a  small 
annular  mass  of  elastic  and 
contractile  tissue.  Its  ex- 
tremity or  glans  is  also  a  cii*- 
cular  enlargement  limited 
behind  by  a  sa-lient  collar — 
the  corona  glandis — which  is 
notched  inferiorly,  and  at 
the  moment  of  ejaculation 
assumes  a  considerable  de- 
velopment, its  shape  being 
then  not  unlike  the  rose  of 
a  watering-can.  This  en- 
largement has  for  its  basis 
the  terminal  expansion  of 
the  urethral  erectile  tissue, 
and  presents  on  its  anterior 
face :  1,  In  the  centre,  a 
rounded  prominence  due  to  the  point  of  the  corpus  cavernosum ;  2,  Beneath 
this,  the  urethral  tube  encircled  by  a  fossa ;  3,  At  the  bottom  of  the  fossa, 
and  below  the  urethra,  the  orifice  of  a  bilocular  cavity — the  urethral  sinus, 
which  widens  at  the  bottom,  and  in  which  accumulates  sebaceous  matter 
that  sometimes  becomes  so  hard  as  to  prevent  the  flow  of  the  urine  by 
compressing  the  tube  ;  4,  Inferiorly,  the  suburethral  notch. 

The  skin  covering  the  extremity  of  the  penis  is  rich  in  nerves  which, 
according  to  Kraiise,  have  round  dilatations  uhich  he  designates  as 
"  terminal  genital  corpuscles." 

To  complete  the  description  of  the  penis,  there  only  remain  to  be 
described :  1,  Two  suspensory  and  retractile  cords  which  concur,  with  the 
natural  elasticity  of  the  fibrous  envelope  of  the  corpus  cavernosum,  to  return 
the  organ  to  its  ordinary  position  when  the  lihenomenon  of  erection  has 
ceased ;  2,  The  tegumentary  fold,  or  sheath,  which  envelops  the  free  portion 
of  the  penis  when  in  its  ordinary  state  of  repose. 

A.  Suspensory  and  Eetractile  Cords  of  the  Penis. — Two  in  number, 
these  cords  arise  from  the  lower  face  of  the  sacrum,  descend  as  flat  bands  in 
front  of  the  sphincter  ani,  between  the  retractor  muscle  of  the  anus  and  the 
rectum,  to  which  they  give  numerous  short  fasciculi  from  their  posterior 


LONGITUDINAL    SECTION    OF    THE    FREE    EXTREMITY    OF 
THE    horse's    penis    IN    A   RELAXED   STATE. 

1,  Erectile  tissue  of  the  corpus  cavernosum  ;  2,  Urethra ; 
3,  Fossa  navicularis ;  4,  Urethral  tube ;  5,  Erectile 
tissue  of  the  urethra ;  6,  Ditto  of  the  glaus ;  7, 
Corona  glandis  ;  8,  Urethral  sinus. 


THE  MALE  GENITAL  ORGANS,  867 

border ;  they  then  unite  at  the  mesial  line,  below  the  anal  oj^euing,  thus 
forming  around  the  terminal  extremity  of  the  rectum  a  real  suspensory  ring. 
Lying  together,  and  intimately  united,  they  are  continued  on  the  accelerator, 
which  they  follow  at  the  rajihe,  and  are  eventually  lost  in  its  texture  near 
the  free  extremity  of  the  penis. 

These  cords  are  composed  of  unstriped  muscular  fibres. 

B.  Sheath  {prepuce). — The  sheath  is  a  cavity  formed  by  a  fold  of  the 
abdominal  integument,  and  lodges  the  free  portion  of  the  penis ;  it  is 
entirely  effaced  at  the  moment  of  erection,  when  the  copulatory  organ  is 
lengthened  and  enlarged.  The  skin  at  the  opening  of  the  sheath  enters  its 
cavity,  and,  on  arriving  at  the  free  portion  of  the  penis,  forms  a  circular 
cul-de-sac  in  becoming  reflected  over  the  organ,  which  it  envelops. 

This  lining  integument  of  the  sheath  is  fine,  and  very  irregularly 
plicated ;  it  is  destitute  of  hair,  and  holds  a  middle  place,  with  regard  to 
organisation,  between  the  skin  and  mucous  membranes.  It  contains  in,  or 
beneath,  its  substance  a  considerable  number  of  sebaceous  or  jJrcejmtial  glands 
that  secrete  an  unctuous  fatty  matter  (exhaling  a  pecular  odour,  and  dark- 
grey  in  colour,  the  smegma  prceputii),  which  is  spread  over  the  surface  of 
the  membrane. 

Above,  the  inner  integument  of  the  sheath  is  applied  to  the  fibrous  tunic 
of  the  abdomen.  Below,  and  on  each  side,  the  cutaneous  fold  constituting 
this  cavity  contains  between  its  layers  an  expansion  of  yellow  elastic  fibrous- 
tissue,  the  lateral  portions  of  which,  attached  to  the  abdominal  tunic,  are 
named  the  suspensory  ligaments  of  the  sheath. 

In  the  Ass,  there  exists,  near  the  entrance  to  the  sheath,  and  on  each  side, 
a  small  tubercle  which  may  be  looked  upon  as  a  rudimentary  teat  of  the 
female. 

(The  prepuce  protects  the  penis,  and  sustains  it  when  in  a  flaccid  state. 
In  certain  Horses,  a  gurgling  sound  is  produced  in  trotting,  from  the  au- 
entering  and  leaving  the  sheath  suddenly.) 

DIFFERENTIAL   CHARACTERS   IN   THE   MALE   GENITAL   ORGANS   OF   OTHER  THAN    SOLIPED 

ANIMALS. 

ErMiNANTS. — Testicles. — In  these  animals,  the  testicles  are  very  voliuninous,  oval, 
and  vertically  elongated.  They,  with  their  envelopes,  form  a  pendant  mass  that  occupies 
the  inguinal  region.  The  scrotum  ie  always  of  a  pale  colour.  In  the  interior  of  the 
testicle,  the  corpus  Highmoriauum  and  the  rete  testis  are  very  marked.  (The  proper 
tissue  is  yellow,  and  the  septa  formed  by  the  prolongations  of  the  tunica  albuginea  are 
not  very  distinctly  seen.) 

Epididymis. —  Vas  deferens. — The  head  of  the  epididymis  is  wide  and  flat,  and  partly 
covers  the  anterior  border  ot  the  testicle.  The  middle  portion,  smaller  than  in  Solipeds, 
represents  a  narrow  cord  lying  outside  the  posterior  border  of  the  seminal  gland.  The 
tail  is  a  little  free  appendage,  inflected  inwards  and  upwards  to  become  continuous  with 
the  vas  deferens.  The  latter  is  dilated,  as  in  the  Horse,  when  it  arrives  above  the  bladder, 
and  lies  beside  the  duct  of  the  opposite  side.  The  two,  thus  joined,  increase  from  before 
to  behind,  leave  the  neck  of  the  bladder  in  passing  above  the  vesicultB  seminales,  then 
go  beneath  the  prostate,  and  terminate  in  the  urethra,  on  the  summit  of  a  ridge,  by  two 
elliptical  orifices. 

Vesicidx  seminales. — In  the  Bull,  the  vesiculfe  seminales  have  not  the  same  appearance 
as  in  the  Horse,  and  they  have  not  so  large  a  cavity  in  their  interior.  They  are  two 
elongated  masses,  lobulated  on  their  surface,  yellow  in  colour,  and  possessing  quite  a 
glandular  aspect.  They  have  sometimes  been  designated  tlje  lateral  prostates.  They 
are  composed  of  aciniform  glands,  inclosed  in  a  mass  of  connective  tissue  and  unstriped 
fibres ;  they  open  into  a  comnn m  central  canal  which  terminates  in  the  vas  deferens. 

Urethra. — This  canal  is  inflected  like  the  letter  S.  Its  diameter  regularly  diminishes 
from  its  commencement  to  its  termination,  which  is  not  provided  with  a  urethral  tube, 
as  in  Solipeds.    Internally  it  presents  :  1,  Immediately  beyond  the  neck  of  the  bladder 


868 


THE  GENERATIVE  APPARATUS. 


Fis.  404. 


a  short,  but  very  i^alient  veru  montanum,  which  divides  iuto  two  raucous  columns,  that 
gradually  subside  posteriorly ;  2,  Towards  the  ischial  arcli,  a  valve  whose  free  border, 
directed  downwards,  covers  a  cul-de-sac  about  3-±ths  to  1  inch  deep. 

The  structure  of  the  urethra  is  also  different.  The  walls  of  the  memhranous  portion 
are  thicker  than  in  the  Horse;  they  have  a  layer  of  erectile  tissue,  and  a  Wilson's 
muscle,  very  thick  below  and  laterally,  and  whose  fibres  are  inserted  in  the  middle  of 
the  upper  surface,  into  an  aponeurotic  laphe'. 

At  the  ischial  arch,  when  the  canal  bends  downwaids,  the  spongy  tissue  becomes 

more  aljunlaut  to  form  the  bulb  of  the 
urethr/i :  but  the  prominence  at  this  point 
is  chiefly  due  to  the  accelerator  urinaj, 
as  is  shown  in  figure  404,  c,  4.  This 
muscle  is  extremely  powerful,  but  it 
so(m  ceases  beneath  tlie  ischial  arch. 
The  iransversus  perinei  is  as  strong  as  in 
Solipeds. 

Glands  annexed  to  the  urethra. — 
Cowper's  (jJands  are  absent.  The  pros- 
tate gland  is  not  voluminous,  and  forms, 
at  the  commencement  of  the  urethra, 
a  little  transverse  yellow  mass,  beneath 
which  pass  the  vasa  deferentia ;  it  also 
lies  beneath  Wilson's  muscle,  and  is 
|)rolonged  for  some  distance  on  the  mem- 
branous portion  of  tbe  urethra. 

Penis. — In  the  Bull,  the  penis  is  long 
and  thin,  and  carried  well  forward  be- 
neath tlie  belly.  It  is  inclosed  at  the 
perineum  in  an  aponeurotic  sheath, 
which  is  covered  by  the  ischio-tibial 
muscles.  This  sheath  is  double,  its 
superficial  layer  being  continuous  with 
the  dartos,  and  has  the  same  physical 
characters ;  the  deep  layer  is  thin,  white, 
anil  inelastic. 

In  front  of  the  pubis,  the  penis  des- 
cribes two  successive  curves — the  8  of 
the  penis — the  first  with  its  conve.\ity 
forwards,  the  secimd  backwards.  It  is 
at  the  second  curve  that  the  suspensory 
ligaments  join  the  penis,  and  continue 
along  its  sides  to  its  extremity. 

The  free  joortion  of  the  organ,  very 
fapering,  is  covered  by  a  fine,  papil- 
lated,  very  sensitive,  rose-coloured 
mucous  membrane. 

J  t  is  lodged  in  a  narrow  sheath  that 
advances  much  more  forward  beneath 
the  abdomen  than  in  Solipeds.  and  has 
at  its  opening  a  bunch  of  long  stiff  hairs. 
This  cutaneous  sheath  is  moved  by  four 
subcutaneous  muscles :  two  posterior  or 
retractors  (Fig.  405,  2)  which  draw  the 
sheath  backwards,  and  concur  in  ex- 
posing the  penis  at  the  moments  of  its 
erection ;  and  two  anterior  or  protractor 
muscles  (Fig.  405,  1)  which  carry  the 
.«heath  forward  to  its  former  position. 
The  latter  are  found  in  the  Cow,  and  do 
not  appear  to  be  of  any  use. 

The  two  constituent  portions  of  the 
copulatory  organ  are  not  joined  in  tbe 
same  manner  as  in  Solipeds,  tl)e  channel 
for  the  lodgment  of  the  urethra  being 
transformed  into  a  complete  canal  by  a  narrow  layer  of  the  fibrous  envelope  of  the  corpus 


SECTIONS   OF    THE   URETHRA   OF    THE   OX   AT 
DIFFERENT    POINTS. 

A,  latrapehic  portion ;  1,  Wilson's  muscle ;  2, 
Erectile  tissue ;  3,  Urethral  canal ;  4,  Prostate 
gland. — B,  The  middle  of  the  penis ;  1,  Fibrous 
cord  of  the  corpus  cavernosum ;  2,  Urethral 
canal ;  3,  Its  erectile  tissue ;  4,  Envelope  of 
the  corpus  cavernosum. — C,  At  the  crura  of  the 
penis  ;  1,  1,  Crura  of  the  corpus  cavernosum  ; 
2,  Urethral  canal ;  3,  Its  erectile  tissue ; 
4,  Accelerator  urinse ;  5,  Ischio-cavernosus 
muscle. 


THE  MALE  GENITAL  ORGANS. 


SG9 


cavernosnin.  Tlic  lattt-r  is  little  developed,  and  presents,  iuternally,  a  longitudinal  fil^rous 
cord;  it  is  not  niiich  dilated  during  erection.  In  this  act,  tiie  penis  is  elongated  by  the 
straightening  out  of  its  curvatures,  rather  thiin  by  any  real  lengthening;  when  erection 
ceases,  the  organ  is  retracted  into  the  preputial  cavity  by  the  contraction  of  the  sus- 
pensory cords,  which  reform  its  double  inflection  behind  the  scrotum. 

In  the  Bam  and  He-ijoat,  the  disposition  of  these  parts  is  somewhat  similar,  fin  the 
former,  the  extremity  of  the  urethra  has  the  form  of  a  narrow  cylinder  curved  backwards, 
its  opening  being  a  longitudinal  slit.  In  Ruminants,  towards  the  extremity  of  the  sheath 
are  small  teats;  these,  in  the  He-goat,  are  sometimes  glandular,  and  secrete  a  fluid 
analogous  to  milk.) 

Fis:.  405. 


PENIS   AND   MUSCLES  OF   THE   SHEATH   OF  THE   BULL. 

1,  Protractor  muscle  of  the  sheath  ;  2,  Retractor  of  ditto ;  3,  Testicles  in  the  scrotum ; 
4,  The  S  of  the  penis ;  5,  Suspensory  cords  of  the  penis  attached  to  the  second 
curve  :  6,  Subcutaneous  abdominal  vein. 

Pig. — The  testicles  of  this  animal  are  round,  and  placed  in  tlie  perineal  region.  The 
scrotum  is  narrow,  and  but  little  detadied:  the  pouches  of  which  it  is  composed 
appearing  simply  as  two  henuspheri -al  prominences  on  the  surface  of  the  perineum. 
There  is  nothing  particular  to  be  remarked  in  the  epididymis  and  vas  deferens;  (the 
tail  of  the  first  is  very  voluminous :  the  latter  has  no  pelvic  dihitation.) 

The  vesiculie  feminales,  with  regard  to  disposition,  are  intermediate  between  those  of 
the.  Horse  and  Ox  Their  walls  are  thick  and  very  glandular,  and  their  interior  is 
diverticulated.  (They  are,  proportionately,  very  large,  and.  in  structure,  closely  re- 
semble those  of  Ruminants ;  indeed,  in  these  animals  they  rather  appear  to  be  organs  for 
the  secretion  of  a  milky  liquid  that  is  mixed  with  the  semen,  than  reservoirs  for  the 
fecundating  matter,  as  tiiat  fluid  never  contains  any  spermatozoa.)  There  are  two 
proi'tates:  one  disposed  as  in  the  Ox;  the  other  jdaced  across  the  neck  of  the  bladder, 
as  in  Solipeds.  The  penis  resembles  that  of  Ruminants,  except  in  the  absence  of  the 
muscles  of  the  sheath ;  it  has  also  a  particular  preputial  sheath,  ■which  has  been  studied 
58 


870  THE  GENERATIVE  APPARATUS. 

by  Lacauchie.  (When  flaccid,  the  penis  of  the  Pig  is  twisted  in  a  spiral  manner  at  the 
extremity.  The  sheath  is  narrow,  and  longer  than  in  Ruminants.  At  the  upper  part  of 
its  opening  is  the  special  poucli  mentioned  by  Chauveau,  and  which  is  formed  by  a  fold 
of  the  skin  It  opens  into  the  sheath,  and  secretes,  in  the  Boar,  an  unctuous  fluid, 
possessing  a  particulaily  dij^agrecable  smell,  and  which  is  mixed  with  the  urine.  The 
odour  of  the  secretion  even  taints  the  flesh  of  this  creature.) 

Carnivora. — The  testicles  of  the  Cut  are  formed  like,  and  placed  in  the  same  situation 
as,  those  of  the  Pig ;  those  of  the  Dog  are  more  oval,  and  are  pendent. 

The  Carnivora  have  no  vesiculx  seminales.  The  prostate  gland  surrounds  the  neck 
of  the  bladder ;  it  is  of  a  yellow  colour,  concave  on  its  upper  surface,  and  divided  into 
two  lateral  lobes  on  its  lower  face.  Coivpers  glands  are  ai^sent  in  the  Dog ;  tliey  exist  in 
the  Cat  (in  which  they  are  very  small,  and  excrete  their  secretion  by  separate  eftVrent 
canals).  The  urethra  (in  its  pelvic  portion)  is  very  long;  towards  the  ischial  arch  it 
shows  an  enlargement  or  hidb,  though  this  is  less,  propoitionately,  than  in  the  Ox  ;  the 
accelerator  muscle  is  continued  for  a  longer  distance  around  it.  (The  spongy  portion  is 
thinner  in  the  Gat  than  the  Dog.) 

"  In  the  Dog,  the  penis  is  long  and  pointed.  The  posterior  half  is  constituted  by  the 
corpus  cavernosum,  whicli  is  little  developed,  and  has  not  a  complete  middle  septum. 
Tiie  anterior  moiety  has  for  its  base  a  bone,  found  in  several  other  mammifers,  which 
is  intended  to  favour  the  introduction  of  the  penis  into  the  genital  organs  of  the  female. 

"  The  penien,  or  penial,  bone  is  elongated,  conical,  and  incurvated,  so  as  to  constitute 
a  furrow  inferiorly,  in  which  is  lodged  the  urethra  when  it  leaves  the  fibrous  channel  of 
the  corpus  cavernosum;  its  apex,  anteriorly,  partly  forms  the  point  of  the  penis;  its  base 
is  intimately  united  to  the  anterior  portion  of  the  corpus  cavernosimi ;  the  median 
septum,  which  is  very  dense,  is  fixed  in  this  bone,  as  is  the  fibrous  envelope  which  mixes 
with  its  periosteum. 

"  Tlie  penial  bone  almost  entirely  constitutes  the  base  of  all  that  portion  of  the  penis 
included  within  the  sheath  ;  in  addition,  this  part  possesses  two  distinct  erectile  enlarge- 
ments— an  anterior  and  posterior.  The  first  is  analogous  to  thut  of  the  glans  penis  of  the 
Horse,  and  is  formed  by  an  expansion  of  the  erectile  tissue  of  the  urethra;  clul)— haped 
at  its  anterior  base,  it  has  there  a  point  suddenly  bent  downwards,  beneath  which  is 
pierced  the  urethral  orifice;  posteriorly  it  is  thin,  and  partially  covers  the  other  erectile 
mass.  The  latter  is  supplementary ;  it  begins  at  the  base  of  the  free  portion  of  the 
penis,  where  the  integument  of  the  sheath  is  folded  in  a  circular  manner  around  it. 
From  1  to  H  inciies  long,  it  embraces  the  upper  border  and  sides  of  the  bone ;  pyramidal 
in  shape,  its  base,  which  is  jjosterior,  is  |  to  1^  inches  thick ;  in  front,  it  thins  away  beneath 
the  erectile  tissue  of  the  head. 

"  Such  are  the  two  erectile  masses,  whose  summits  overlap,  so  that  the  free  portion  of  the 
penis,  bulging  in  front,  and  still  more  so  behind,  is  narrowest  in  the  middle.  Although 
contiguous,  these  two  vascular  dilatations  are  independent  of  each  other;  the  posterior 
has,  likewise,  no  communication  with  the  corptis  cavernosum,  and  possesses  two  parti- 
cular veins  which  pass  backward  in  a  lateral  groove.  Each  is  erected  separately  during 
•copulation,  when  they  assume  a  large  size;  the  great  volume  of  the  posterior  enlarge- 

■  ment  prolongs  the  duration  of  this  act,  until  flaccidity  ensues.     This  peculiarity  is  a 

■  consequence  of  the  absence  of  the  seminal  reservoirs  (the  vesiculse  seminales). 

"  In  the  Dog.  two  small  muscles  are  found  which  appear  to  be  destined  to  elevate  the 
penis  and  direct  it  during  its  introduction  into  the  sexual  parts  of  the  female,  as  its 
erection  is  always  feeble.  These  are  two  fasciculi  which  proceed  from  the  crura  of  the 
penis,  and  pass  forward  to  unite  in  a  common  tendon  implanted  on  the  dorsal  border  of 

■  the  organ  ;  they  thus  resemble  the  chord  of  an  arc. 

"  Tiie  subpenial  muscular  cords  exist  as  in  the  other  animals.  The  sheath  is  narrow 
and  long,  and,  as  in  the  didnctyles,  ha,?, protractor  muscles;  the  integument  is  thin  and 
rose-coloured,  like  that  covering  the  free  portion  of  the  penis. 

"  In  the  Cat,  the  penis  is  short,  and  directed  backwards  ;  but  in  a  state  of  erection  it 
is  inclined  forwards  for  copulation.  Its  free  portion  presents  some  peculiarities.  It  is 
conical,  and  its  summit,  near  wiiich  is  pierced  the  urethral  opening,  has  for  its  basis  a 
small  incomplete  penial  bone,  that  encloses  a  layer  of  erectile  tissue — an  expansion  of 
that  of  the  urethra.  This  free  portion  is  covered  by  an  integument  studded  with  some- 
what rigid  papillse  directed  backwards,  and  capable  of  being  made  erect  during 
oopulatiiin.  These  points,  which  are  met  with  in  nearly  all  the  Cat  kind,  are  analogous 
to  tlie  hairs,  scales,  strong  spines,  and  even  the  cartilaginous  saws,  of  certain  other 
animals,  and  which  appear  to  be  related  to  the  degree  of  sensitiveness  of  the  female 
sexual  organs." — A.  Lavocat. 


THE  MALE  GENITAL  OBGANS. 


871 


COMPARISON   OP   THE   GENITAL   ORGANS  pF  MAN   WITH   THOSE   OF   ANIMALS. 

Coverings  of  the  testicles. — The  scrotum,  dartos,  tunica  erythryoidea,  nr.d  tunica 
vaginalis  h;ive  the  same  org.inisation  as  in  Solipeds.  The  scrotum  is  rich  in  sebaceous 
glunds,  and  the  tunica  vagimdis  is  separated  by  a  serous  layer  from  the  peritoneal  cavity. 

'Jesticles. — Tliese  are  ovoid,  and  situated  in  an  oblique  direction  downwards  and 
inwards  ;  their  largest  curvature  is  forwards. 

The  epididymis  oti'ers  the  same  arrangement  as  already  noticed,  except  that  the  vns 
deferens,  in  being  detached  from  the  globus  minur,  is  bent  .omewhat  suddenly  to  reach 
the  abdominal  cavity.  There  are  several  diverticuli  annexed  to  the  epididymis,  named 
the  pediculated  hydatid  of  Morgagni,  non-jediculated  hydatid  uherrant  vessels,  anl  roipus 
innominatum  of  Giraldes. 

Fie;.  406. 


SECTION   OF    PELVIS   TO   THE   LEFT   OF   THE   MEDIAN    LINE   AT   THE    PUHES,    AND 
THROUGH    THE    MIDDLE    OF    THE    SACRUM. 

1,  Section  of  left  pubic  bone ;  2,  Peritoneum  on  bladder  ;  3,  Left  crus  penis  ;  4, 
Pelvic  fascia  forming  anterior  ligaments  of  bladder ;  5,  Part  of  accelerator 
urinse  ;  6,  Posterior  layer  of  triangular  ligament  forming  the  capsule  of  the 
prostate ;  7,  Anterior  layer  of  triangular  ligament ;  Between  6  and  7  are  seen 
the  membranous  urethra,  deep  muscles  of  urethra  (insertion),  and  Cowper's  glanJ 
of  the  left  side;  8,  Vas  deferens;  9,  Bulb  of  urethra;  10,  Rectum;  11,  Cut 
edges  of  accelerator  urinae  and  transversus  perinsei ;  12,  Left  ureter;  13,  Reflec- 
tion of  deep  layer  of  superficial  fascia  round  transversus  perinrei ;  14,  Left 
vesicula  seminalis;  15,  Cut  edge  of  levator  ani ;   16,  Rectum;  17,  Prostate  gland. 


The  hydatid  of  Morgagni  is  a  little  projection  at  the  head  of  the  epididymis,  filled 
with  a  serous  fluid  which  is  never  mixed  with  tlie  semen.  The  non-pedicuhited  hydatid 
is  a  small  white  mass  which  rises  from  tlie  testicle  Ht  some  distance  from  the  globus  mnjor  ; 
it  has  a  cavity  that  communicates  with  the  duct  of  the  epididymis.  The  aherrant  vessels 
are  fine  flexuous  ducts  given  off  from  the  globus  minor,  and  soon  terminate  in  a  cid-de- 
sac.  The  corpus  innominatum  of  Giraldes  is  a  small  mass  of  ramifying  tubes  included 
in  the  connective  tissue  uniting  the  globus  miijor  to  the  testicle.  All  these  appendages 
of  the  testicle  or  eindidymis,  are  the  remains  of  the  WolfSan  body. 

Vas  deferens.— This  is  not  united  to  its  fellow  by  a  peritoneal  fold;  it  is  slightly 
dilated  on  arriviu^^  at  tbe  neck  of  the  bladder,  as  in  tlie  Horse.  The  vesicular  seminales 
are  eloneated,  and  lobubite'l  on  their  surface,  as  in  Euminants. 

Urethra. — This  canal  has  a  fixed  and  a  free  portion  :  the  first  is  slightly  inclined 
downwards  and  forwards ;  the  second  is  suddenly  intlected,  and,  with  the  preceding, 
forms  the  prepubic  angle,  which  disappears  with  erection.  Its  diameter  increnses  a  little 
at  tiie  bidb,  and  again  at  the  meatus,  to  form  the  fossa  navicular  is.  Its  erectile  envelope 
forms  a  considerable  enlargement  at  its  commencement — the  bulb,  ami  this  is  covered, 
as  in  the   Ox,  by  the   accelerator  urinse ;   it  also  composes  another,  the  glans,   that 


872  TEE  GENERATIVE  APPARATUS. 

constitutes  the  head  of  the  penis.  On  its  inner  surface  are  some  valvular  folds,  some 
depressions,  the  lacunx  of  Morgagni,  the  veru  montaniim,  and  towards  the  summit  uf  this 
a  small  pouch — the  male  uterus  {sinus  pocularis),  which,  on  a  very  reduced  scale,  repre- 
sents the  third  vesicula  of  Solipeds.  The  muscles  of  the  urethra  are  the  iscldo-cavernosum, 
accelerator  urinie,  Wilsons  muscle,  and  the  transversus  perinxi — superficial  and  deep.  (Jn 
emerging  from  the  pelvic  cavity,  the  urethra  traverses  an  aponeurotic  membrane  named 
the  ligament  of  Carcassonne. 

Corpus  cavtrnosum. — This  offers  nothing  particular  in  its  disposition. 

Penis. — This  organ  is  free,  and  is  suspended  in  front  of  the  pubis.  It  is  enveloped 
by  a  fibrous  covering— the  superficial  fascia,  and  a  cutaneous  cylinder — the  sheath.  It  is 
attached  by  two  supensory  ligaments  :  the  superficial  is  elastic,  and  arises  from  the  linea 
alba;  the  deep  is  inelastic,  and  is  detached  from  the  symphysis  pubis  and  t!ie  anterior 
pillar  of  t lie  inguinal  ring.  (It  is  usual  to  describe  only  one  ligament — the  ligamentum 
susjjensorium  penis,  separating  to  form  two  layers  which  give  passage  to  the  dorsal 
vessels,  and  nerves  of  the  penis.)  The  glans  is  separated  from  the  rest  of  the  organ  by  a 
constriction  designated  the  cervix,  and  around  this  the  skin  forms  a  (circular)  fold — the 
prepuce,  which  covers  the  glans  more  or  less  completely.  It  is  attached  to  the  middle  of 
its  lower  face  by  a  thin  fold— the  frxnum  prxpuiii.  The  inner  surface  of  the  prepuce 
has  a  large  number  of  sebaceous  glands. 


CHAPTER  II. 

GENITAL   ORGANS   OF   THE   FEMALE, 

These  organs  resemble  those  of  the  male  in  their  general  disposition.  Thus 
we  find  in  the  female  :  1,  Two  secretory  organs,  the  ovaries,  analogous  to 
the  testicles,  and  charged  with  the  elaboration  of  the  germ ;  2,  The  uterine 
(Fallojnan)  tube,  disposed,  like  the  ej)ididymis  and  vas  deferens,  as  a  flexuous 
canal,  through  which  the  ovum  passes  on  leaving  the  ovary  ;  3,  The  uterus, 
a  single  reservoir  formed  of  two  lateral  moieties  which  may  be  compared  to 
the  vesiculas  semiuales,  as  it  is  there  that  the  germ  remains  until  it  is  fully 
developed ;  4.  The  vagina,  a  membranous  canal  analogous  to  the  urethra, 
and  giving  passage  to  the  foetus  after  it  has  been  formed  in  the  uterus :  this 
canal,  which  receives  the  penis  during  copulation,  also  shows,  at  its  exterior 
opening,  the  vulva,  an  erectile  apparatus,  and  the  clitoris,  which  is  nothing 
more  than  a  rudimentary  corpus  cavernosum  of  the  male.  The  female  has 
also  certain  glands,  which,  in  many  species,  exist  in  a  rudimentary  form  in 
the  male :  for  instance,  the  mammae,  organs  for  the  secretion  of  milk,  the 
first  nourishment  of  the  young  animal. 

(The  glands  of  Diiverney,  in  the  female  vagina,  seem  to  be  analogous  to 
Cowper's  glands  in  the  male,  as  they  are  present  in  the  females  of  all 
animals  where  the  latter  exist  in  the  male,  and  their  secretion  appears  to  be 
of  the  same  character.) 

It  may  be  remarked,  after  this  enunciation,  that  the  male  and  female 
genital  apparatus  are  constructed  on  the  same  type  :  a  circumstance  which  is 
most  clearly  demonstrated  at  an  early  period  of  intra-uterine  life,  when  it  is 
impossible  to  distinguish  the  sexes. 

1.   TJie  Ovaries.     TFig.  411,  1.) 
Situation — Form — Belations. — The  ovaries  (testes  muliehres'),  the  essential 
organs  of  generation  in  the  female,  are  two  ovoid  bodies,  smaller  than  the 
testicles,  though  of  the  same  shape,  situated  in  the  abdominal  cavity,^  and 

*  The  ovaries  sometimes  leave  this  situation.  Thus  M.  Dupont,  of  Plazac,  has 
observed  them,  in  four  swine,  occupying  little  cavities,  analogous  to  those  of  the  male 
scrotum,  in  the  perineal  region. — '  Journal  des  Ve'terinaires  du  Midi,'  December,  1869. 


THE  FEMALE  GENITAL  ORGANS.  873 

suspended  from  the  sublumbar  region,  where  tliey  correspond  with  the 
intestinal  convolutions,  a  little  behind  the  kidneys.  Smooth  on  the  surface, 
these  organs  j^resent.  in  the  middle  of  their  upper  face,  a  deep,  and  more  or 
less  oblique  fissure,  resembling  the  Mliis  of  the  kidney  ;  this  gives  attach- 
ment to  the  pavilion  of  the  tube. 

Means  of  attachment. — The  ovary  floats  at  the  anterior  border  of  the 
broad  ligament ;  it  is  also  sustained  by  the  vessels  which  enter  it,  and  by  a 
small  cord  of  unstriped  muscular  fibres,  the  ligament  of  the  ovary,  which 
attaches  it  to  the  uterus. 

Structure. — The  organisation  of  the  ovaries  comprises  a  serous  mem- 
hrane,  a  tunica  albiiginea,  p-o^er  tissue,  and  the  Graafian  vesicles  imbedded 
therein. 

Serous  membrane. — This  is  a  continuation  of  the  broad  ligaments ;  it 
covers  the  whole  organ  (except  at  the  hilus),  adhering  closely  to  the  tunica 
albuginea. 

Tunica  albuginea.  —This  is  similar  to  that  enveloping  the  testicle,  being 
a  very  resisting  fibrous  case  which  sends  prolongations  into  the  substance  of 
the  ovary. 

Proper  tissue. — The  proper  tissue,  or  stroma,  of  the  ovary  is  more  con- 
sistent than  that  of  the  testicle  ;  it  is  hard,  grates  on  being  cut  into,  and 
is  greyish-red  in  colour.  It  is  divisible  into  two  layers,  distinguishable  by 
their  aspect  and  structure. 

1.  The  medullary  layer,  that  nearest  the  hilus,  is  slightly  red  and 
spongy ;  it  is  formed  by  an  interlacing  of  the  connective  fibres,  uustriped 
muscular  fibres,  and  a  large  number  of  vessels  that  radiate  from  the  centre 
towards  the  periphery. 

2.  The  cortical  layer  has  the  elements  of  connective  tissue  for  its  base ; 
it  is  but  little  vascular,  and  contains  in  its  substance  the  Graafian  'vesicles 
ov  follicles  (ovisacs),  and  is  consequently  often  named  the  ovigenous  layer. 
These  ovisacs  are  in  various  stages  of  development ;  the  smallest  are 
situated  beneath  the  tunica  albuginea,  and  gradually  increase  as  they  lie 
deeper.  When  fully  developed,  they  are  filled  with  a  transparent,  citron- 
coloured  fluid  ;  the  ovigenous  layer  can  then  no  longer  contain  them,  and 
they  protrude  more  or  less  from  the  surface  of  the  ovary. 

A  Graafian  vesicle,  in  its  perfect  state,  is  composed  of  an  envelope  and 
its  contents-  The  envelojje  comprises:  a  fibrous  membrane  {tunica fibrosa), 
which  is  confounded  with  the  stroma  of  the  ovary,  and  in  it  we  may  re- 
cognise two  layers,  the  internal  of  which  is  rich  in  vessels ;  and  an  epithelium, 
or  membrana  granulosa,  consisting  of  round  or  polygonal  granular  cells. 
At  the  bottom  of  the  ovisac,  this  epithelium  forms  a  small  mass — the  cumulus 
proligenis  (or  germinal  eminence),  in  the  centre  of  which  is  the  ovidum  or 
egg  of  the  mammal.  The  contents  (liquor  folliculi)  are  a  clear  yellow  fluid, 
which  becomes  red  on  admixture  with  blood  when  the  vesicle  ruptures. 

The  ovulum  or  ovum  is  a  cell  about  1-1 00th  of  an  inch  in  diameter, 
inclosed  in  the  discus  proligerus  or  cumulus  proligerus.  The  ovidum  is 
invested  by  an  amorphous,  thick  cell-membrane  — the  zona  pellucida  (mem- 
brana vitellina) ;  its  granular  contents  are  named  the  vitellus  or  yelk ;  and 
its  (vesicular  nucleated)  nucleus,  designated  the  germinal  vesicle,  and  lying 
at  a  certain  point  on  the  zona  pellucida,  has  in  its  centre  a  white  patch — ^the 
germinal  spot. 

Vessels  and  nerves. — The  thick,  flexuous,  arterial  divisions  are  given  off 
by  the  utero-ovctrian  artery ;  they  ramify  in  the  spaces  formed  by  the  tunica 
albuginea,  before  reaching  the  proper  tissue  by  entering  the  hilus.     The 


874 


THE  GENERATIVE  APPARATUS. 


Fig.  407. 


veins  are  of  large  calibre,  and  form  a  very  rich  network  around  the  gland 
- — the  bulb  of  the  ovary  ;  they  terminate  in  the  vena  cava,  near  the  renal  veins. 
The  lympyiatks  pass  to  the  sublumbar  glands.  The  nerves  emanate  from 
the  small  mesenteric  plexus. 

Development. — The  ovary  of  Solipeds  is  of  great  size  in  the  foetus, 
being  often  nearly  as  large  as  in  the  adult  animal.  It  becomes  wasted  in 
aged  animals. 

Functions. — The  productive  organs  of  the  germ  or  ovum,  the  ovaries 
are  the  testicles  of  the  female.  They  form  the  ovulum,  and  then  at  a  cer- 
tain period  set  it  at  liberty.  As  the  ovulae  are  contained  in  the  ovisacs, 
it  is  necessary  to  study :  i,  The  development  of  these  ovisacs ;  2,  Their 
rupture  or  dehisence ;  3,  The  phenomena  occuriug  in  them  after  this 
rupture. 

Development  of  the  Ovisacs. — The  ovisacs  already  exist  in  the  ovary  of 
the  foetus  and  the  young  animal,  but  only  assume  their  greatest  activity  at 
the  age  of  puberty.  They  are  not  all  formed  at  birth,  but  are  incessantly 
re-developed,  this  development  taking  place  beneath  the  tunica  albuginea. 
(At  puberty,  the  stroma  of  the  ovary  is  crowded  with  ovisacs  so  minute, 
that  in  the  Cow  it  has  been  computed  that  a  cubic  inch  would  contain  two 
hundred  millions  of  them.) 

At  first  the  ovisac  consists  of  a  small  cell,  which 
presents  all  the  constituent  parts  of  the  ovulum.  As 
it  becomes  developed  it  sinks  into  the  cortical  layer, 
being  pushed  deeper  into  it  by  the  cells  that  grow 
outside  it ;  and  it  is  also  surrounded  by  a  granular 
membrane,  formed  at  the  expense  of  the  nuclear 
elements  of  the  adjacent  connective  tissue.  This 
membrane  soon  separates  at  a  given  point  into  two 
layers,  to  form  a  cavity  that  gradually  extends  and 
becomes  filled  with  fluid  :  this  is  the  cavity  of  the 
ovulum.  As  the  separation  is  not  complete,  tlie 
ovulum,  enveloped  by  the  internal  granular  membrane, 
remains  beside  the  external  granular  membrane,  and 
while  the  cavity  is  increasing,  the  tissue  of  the  ovary, 
pressed  around  it,  is  condensed,  constituting  the 
fibrous  wall  of  the  ovisac,  which  afterwards  receives 
a  network  of  vessels. 

Rupture  of  the  Ovisacs. — Until  puberty,  the  ovisacs 
do  not   exhibit  any  very  marked  phenomena ;  at  this 
period,  however,  the  ovary  becomes  vascularised,  and 
a   certain   number   of  Graafian   vesicles   increase   in 
OVARIUM  OF  THE  RABBIT   volumo.     At  the  pcriod  of  oestrum,  one  or  more  of 
AT    THE    PERIOD    OF   ^]jggQ    accoi'diug  to  tlio   specics,   participate   in   the 

CESTRUM,      SHOWING        -i  •       ,n  "^  ,  ^  ^t  i    i  •    j.        1     1 

VARIOUS     STAGES     OF   chaugo  lu  the   ovary,   become  vascular  and  distended, 

THE     EXTRUSION     OF    and  finish    by  rupturing  and  evacuating  the   discus 

OVA.  proligerus  and   ovulum.     The  latter  is  received  into 

the  Fallojiian  tube  and  conveyed  towards  the  uterus. 

Corpus  Luteun. — After  the  rupture  of  a   Graafian  vesicle,  its  cavity  is 

filled  by  a  clot  of  blood  which  gradually  contracts  and  loses  its  colour ;  at 

the  same  time  the  fibrous  membrane  becomes  hypcrtrophied,  and  the  granular 

layer    is    wrinkled    and    transformed    into    cylindrical    epithelium.       To 

this  period  of  progression  succeeds  one  of  regression,  during  which  the 

cylindrical  cells  become  infiltrated  with  fat  and  are  gradually  absorbed. 


THE  FEMALE  GENITAL  ORGANS. 


875 


The  term  corpus  luteum  is  given  to  tlie  cicatrix  resulting  from  the  rupture  of 
the  ovisac. 

The  progress  of  the  phenomena  of  hypertrophy  and  regression  is  much 
slower  when  the  escape  of  the  ovuliim  has  been  followed  by  impregnation ; 


¥iz.  408. 


Fls.  409. 


.^-^f^ 


/^_ 


'J 


CONSTITUENT   PARTS   OF    MAMMALIAN   OVUM. 

Fig.  408,  Entire  ovum  ;  Fig.  409,  Ovum  ruptured,  with  the  contents  escaping  ;  mv,  Vitelline 
membrane  ;  j,  Yolk  ;  vg,  Germinal  vesicle  ;  tg,  Germinal  spot. 

SO  that  we  have  false  corpora  lutea  (those  which  are  independent  of  preg- 
nancy), and  true  corpora  lutea,  those  of  gestation,  and  which  do  not  disappear 
until  several  weeks  after  parturition.     (The  true  corpora  lutea  are  recog- 

Fig.  410. 


SUCCESSIVE   STAGES   IN   THE    FORMATION   OF   THE   CORPUS   LUTEUM   IN   THE   GRAAFIAN 
FOLLICLE   OF    A    SOW;    VERTICAL   SECTION. 

a,  Tlie  follicle  immediately  after  the  expulsion  of  the  ovum,  its  cavity  being  filled 
with  blood,  and  no  ostensible  increase  of  its  epithelial  lining  having  yet  taken 
place;  at  6,  a  thickening  of  this  lining  has  become  apparent;  at  c,  it  begins  to 
present  folds  which  are  deepened  at  d.  and  the  clot  of  blood  is  being  absorbed  and 
decolorized ;  a  continuance  of  the  same  process,  as  shown  at  e,  f,  g,  h,  forms  the 
corpus  luteum,  with  its  stellate  cicatrix. 


nisable,  after  parturition,  as  small  white  or  dark-coloured  masses,  the  corpora 
albicans  vel  nigrum.     The   yellow  colour  to  which   they  owe  their  name  is 
due  to  the  infiltration  of  the  cylindrical  cells  with  fat.) 
Such  are,  very  briefly,  the  functions  of  the  ovary. 


876  THE  GENERATIVE  APPARATUS. 

(Beneath  the  hilus  of  the  ovary,  and  between  the  layers  of  the  broad 
ligament  and  the  round  ligament,  is  found  a  small  body,  usually  described 
as  the  parovarium,  consisting  of  a  number  of  fine  tubes  with  blind  extremities. 
It  is  considered  as  the  remains  of  the  Wolffian  body  :  a  foetal  structure  that 
forms  the  epididymis  in  the  male,  and  has  been  named  the  organ  of  Bosen- 
muller  in  the  female.  Chauveau  does  not  mention  its  existence  in  the 
domesticated  animals,  though  Leyh  does.) 

2.  The  Oviducts,  or  Fallopian  or  Uterine  Tubes.     (Fig.  411,  2.) 

The  uterine  tube  is  a  little  flexuous  canal,  lodged  in  the  broad  ligament, 
near  its  anterior  border.  It  commences  at  the  ovary  by  a  free,  exj^anding 
extremity — the  paiilion  of  the  tube  (or  ostium  nhdominale),  and  terminates 
in  the  cul-de-sac  of  tue  uterine  horn  by  ojieniug  into  it  (the  ostium  uterinum). 
Its  canal  at  the  middle  is  so  narrow  as  scarcely  to  admit  more  than  a  very 
thin  straw,  and  its  calibre  is  still  less  towards  the  uterine  extremity ;  near 
the  ovary,  however,  it  is  wide  enough  for  the  passage  of  a  thick  goose-quill. 

The  orifice  of  the  uterine  extremity  opens  in  a  small  and  very  hard 
tubercle.  The  ovarian  extremity,  in  all  mammalia,  offers  a  very  remarkable 
arrangement.  It  opens  into  the  peritoneal  cavity,  near  the  fissiu*e  of  the 
ovary,  and  in  the  centre  of  the  expansion  named  the  pavilion  of  the  tube, 
which  is  also  designated  the  fimbriated  extremity  (or  morsus  diaboli). 
This  pavilion  is  attached  to  the  external  side  of  the  ovary,  and  has  a  very 
irregular  outline :  notched  as  it  is  into  several  lancet-shaped,  unequal  pro- 
longations (fimbrice),  which  float  freely  in  the  abdomen.  Here  are,  then, 
two  important  anatomical  facts :  the  discontinuity  between  a  gland  and 
its  excretory  canal,  and  the  communication  of  a  serous  cavity  with  the 
exterior. 

Structure. — The  oviduct  is  formed  of  a  sei'ous,  a  contractile,  and  a 
mucous  tunic.  The  serous  (external)  is  furnished  by  the  broad  ligament, 
and  is  derived  from  the  peritoneum.  The  contractile  [middle)  is  constituted 
by  unstrij)ed  muscular  fibres,  which  extend  into  the  pavilion.  (They  are 
arranged  as  circular — internal,  and  longitudinal — external  fibres,  and  are  con- 
tinuous with  those  of  the  uterus ;  they  are  mixed  with  immature  nucleated 
areolar  tissue.)  The  mucous  membrane  is  in  longitudinal  folds  in  the  tube, 
but  in  the  pavilion  these  folds  are  radiating ;  it  is  covered  by  a  ciliated 
cylindrical  epithelium  (the  vibrations  of  the  cilia  being  towards  the  uterus.) 
(It  has  very  few  glands  and  no  villi.)  At  the  margin,  or  fimbriae,  of  the 
pavilion  it  suddenly  ceases,  and  is  continued  by  the  peritoneum  (a  serous 
cyst  is  frequently  found  in  this  situation ;  at  the  other  extremity  the 
mucous  membrane  is  continuous  with  that  of  the  uterus). 

Functions. — The  excretory  duct  of  the  ovary,  the  uterine  tube,  seizes 
the  ovulum  expelled  from  the  ovisac,  and  carries  it  to  the  uterus.  It  is 
therefore  necessary  that,  at  the  moment  of  rupture  of  the  ovisac,  the  fimbriae 
should  be  applied  to  the  ovary,  in  order  to  receive  the  germ  and  bring 
it  to  the  abdominal  orifice  of  the  tube.  The  application  of  the  pavilion  to 
the  ovary  is  brought  about  either  by  the  contraction  of  the  muscular  fibres 
it  contains,  or  through  the  distention  of  the  bulb  of  the  ovary.  Some- 
times this  mechanism  is  insufficient,  and  the  ovulum  falls  into  the  abdominal 
cavity,  becomes  fixed  there,  and  is  developed  if  it  has  been  previously  fecun- 
dated :  this  occurrence  constitutes  the  most  remarkable  variety  of  extra- 
uterine gestation. 

The  oviduct  also  conveys  the  seminal  fluid  of  the  male  to  the  ovulum. 


THE  FEMALE  GENITAL  ORGANS.  877 

3.  The  Uterus.    (Figs.  411,  412.) 

The  litems  is  a  membranous  sac  to  which  the  ovulum  is  carried,  and  in 
which  it  is  develojied. 

Sttuafion. — It  is  situated  iu  the  abdominal  cavity,  in  the  subhimbar 
region,  at  the  entrance  to  the  pelvic  cavity,  where  its  posterior  extremity  is 
placed. 

Form  and  relations. — In  its  posterior  moiety,  the  uterus  is  a  sinf^le 
cylindrical  reservoir,  slightly  depressed  above  and  below ;  this  is  the  body 
of  the  uterus.  Its  anterior  moiety  is  bifid,  and  gives  rise  to  tico  cormia, 
which  curve  upwards. 

The  body  is  related,  by  its  upper  face,  to  the  rectum,  which  lies  on  it 
after  passing  between  the  two  cornua ;  it  receives,  on  the  sides  of  this  face, 
the  attachment  of  the  broad  ligaments  ;  its  lateral  and  anterior  faces  are 
related  to  the  intestinal  convolutions.  {Inferiorhj,  it  is  in  relation  with 
the  bladder.)  Its  anterior  extremity  (or  fundus)  is  continuous,  without 
interruption,  with  each  of  the  cornua ;  the  posterior  is  separated  from  the 
vagina  by  a  constriction  of  the  neck  (^cervix)  of  the  uterus. 

The  cornua,  mingled  with  the  different  portions  of  intestine  whicli 
occupy  the  same  region,  offer :  a  free  and  convex  inferior  curvature ;  a 
superior  curvature,  to  which  the  suspensory  ligaments  are  attached;  a 
posterior  extremity,  or  base,  fixed  to  the  body  of  the  organ ;  and  an  anterior 
extremity  or  summit — a  rounded  blind  pouch  looking  downwards,  and  showing 
the  entrance  of  the  oviduct. 

Means  of  attachment. — Floating  in  the  abdominal  cavity,  like  the  in- 
testines, the  uterus  is  also,  like  them,  attached  by  lamellar  bands  which 
suspend  it  to  the  subliimbar  region,  and  which  for  this  reason  have  been 
named  the  suspensory  or  broad  ligaments  of  the  uterus. 

These  bands  are  two  in  number,  are  irregularly  triangular  in  shape,  and 
are  more  developed  before  than  behind.  Close  to  each  other  posteriorly, 
and  separating  in  front  like  the  branches  of  the  letter  V,  they  leave  the 
sublumbar  surface  and  descend  towards  the  uterus,  to  be  attached  by  tbeir 
inferior  border  to  the  s-ides  of  the  upper  face  of  the  body  and  the  small 
curvature  of  the  cornua.  Their  anterior  body  is  free  ;  they  sustain  the 
oviducts  and  ovaries,  the  former  being  placed  between  the  two  serous  layers 
of  the  ligament,  and  the  latter,  placed  within  this  ligament,  receives  a  band 
detached  from  the  principal  layer,  fo-rming  with  it,  beneath  the  ovary,  a 
kind  of  small  cupola. 

There  is  also  another  little  narrow  long  band  outside  the  broad  ligament, 
and  which  can  be  traced  as  far  as  the  upper  inguinal  ring.  Anteriorly,  it 
has  a  small  enlarged  appendix  ;  between  the  two  layers  forming  this  fold  is 
found  a  thin  muscle,  altogether  like  the  male  cremaster  before  the  descent 
of  the  testicle  into  the  scrotum.  This  may  be  looked  upon  as  the  analogue 
of  the  round  lirjament  of  Woman. 

The  uterus  is  also  fixed  in  its  situation  by  its  continuity  with  the 
vagina. 

Interior. — The  inner  surface  of  this  organ  offers  mucous  folds,  which 
exist  even  in  the  foetus ;  they  are  arranged  in  a  longitudinal  series,  and  are 
not  effacable  by  distension ;  though  they  disappear  during  gestation,  con- 
sequent on  the  enlargement  that  takes  place  in  the  uterine  cavity. 

This  cavity  has  three  compartments :  the  cavity  of  the  body,  and  those 
of  the  cornua.  The  latter  are  pierced,  at  their  extremity,  by  the  ixterine 
orifice  of  the  Fallopian  tube;   while  the  former  communicates  with  the 


878 


TEE  GENERATIVE  APPARATUS. 

Fi?.  411. 


GENERATIVE   ORGANS  OF   THE   MARE,    ISOLATED   AND   PARTLY   OPENED. 

1,  1,  Ovaries ;  2,  2,  Fallopian  tubes ;  3,  Pavilion  of  the  tube,  external  face ;  4,  Ibid., 
inner  face,  showing  the  opening  in  the  middle  ;  5,  Ligament  of  the  ovary ;  6,  Intact 
horn  of  the  uterus;  7,  A  horn  thrown  open;  8,  Body  of  the  uterus,  upper  face; 
9,  Bi'oad  ligament;  10,  Cervix,  with  its  mucous  folds;  11,  Cul-de-sac  of  the 
vagina;  12,  Interior  of  the  vagina,  with  its  folds  of  mucous  membrane;  13, 
Urinar}'  meatus,  and  its  valve,  14;  15,  Mucous  fold,  a  vestige  of  the  hymen;  16, 
Interior  of  the  vulva;  17,  Clitoris;  18,  18,  Labia  of  the  vulva;  19,  Inferior 
commissure  of  the  vulva. 


TEE  FEMALE  GENITAL  ORGANS.  879 

vagina  by  a  narrow  canal  that  passes  tlirougli  the  posterior  constriction  of 
the  uterus  (cervix),  and  which  is,  in  Human  anatomy,  named  the  cavity  (or 
canal)  of  the  cervix  {os  vteri,  os  externum,  os  tricce).  In  all  the  domesticated 
animals,  excejit  the  Eahbit,  the  uterine  canal  is  prolonged  to  the  bottom  of 
the  vagina,  in  something  the  same  fashion  as  a  tap  is  into  the  interior  of  a 
barrel ;  and  in  this  way  it  always  forms  a  very  marked  projection  in  the  vaginal 
cavity.  Around  this  projection,  the  utero-vaginal  mucous  membrane  is 
raised  in  transverse  folds  disposed  in  a  circular  manner,  which  give  it  the 
appearance  of  a  radiated  flower ;  in  Veterinary  anatomy,  this  projection  of 
the  cervix  is  consequently  named  the  "  expanded  flower  " — fleur  epanoiiie  ;  it 
is  the  tench's  nose  of  the  Human  being. 

Structure. — The  walls  of  the  uterus  are  composed  of  three  membranes  : 
an  external,  serous ;  a  middle,  muscular ;  and  an  internal,  mucous ;  with 
vessels  and  nerves. 

The  serous  tunic  envelops  all  the  organ  ;  it  is  an  expansion  of  the 
broad  ligaments,  which  are  prolonged  backwards  on  the  posterior  extremity 
of  the  vagina,  and  are  afterwards  doubled  in  a  circular  fashion  around  that 
canal,  to  pass  over  either  the  rectum,  the  bladder,  or  the  lateral  walls  of  the 
pelvis.  Between  the  two  cornua  this  membrane  forms  a  particular  frsenum, 
which  is  but  slightly  developed  in  Solipeds. 

The  muscular  layer  comprises  longitudinal  (superficial),  and  circular 
(<leepj  fibres,  analogous  to  those  of  the  small  intestine.  Near  the  insertion 
of  the  broad  ligaments,  they  give  off  a  series  of  fasciculi  which  are  pro- 
longed between  the  two  layers  of  these  ligaments.  These  are  not  the  only 
muscular  fibres  met  with  in  the  ligaments,  however ;  for  Eouget  has  found 
others  throughout  their  whole  extent,  but  particularly  in  the  vicinity  of  the 
ovaries.^  (Around  the  cervix  uteri,  the  circular  fibres  are  most  dense  and 
numerous.) 

In  the  pregnant  animal,  the  mimber  of  fibres  composing  this  layer  is 
much  more  considerable  than  in  ordinary  circumstances  ;  and  this  increase 
has  for  its  object  to  permit  the  dilatation  of  the  uterus,  without  allowing 
its  parietes  to  become  too  attenuated ;  they  do  become  more  or  less  thin, 
notwithstanding,  according  to  the  species.  It  has  also  been  remarked  that, 
during  pregnancy,  the  muscular  fibres  present  a  manifest  striation.  (The 
elements  of  these  fibres  are  short  fusiform  cells  with  long  oval  nuclei,  mixed 
with  a  large  quantity  of  immature  nucleated  areolar  tissue.) 

The  mucous  membrane  is  thin,  delicate,  and  raised  into  folds.  It  is 
covered  by  ciliated  epithelium,  which  becomes  cylindrical  in  the  canal  of 
the  cervix,  and  pavemental  around  the  os  uteri.  (The  cilia  vibrate  towards 
the  fundus  of  the  organ.  The  membrane  is  closely  connected  with  the 
muscular  tunic,  and  is  composed  of  immature  nucleated  areolar  tissue 
without  elastic  fibres.)  The  uterine  mucous  membrane  is  destitute  of 
papillas  (except  at  the  cervix,  where,  according  to  Leyh,  there  are  many 
highly  vascular  papillae)  ;  but  it  lodges  numerous  simple  or  ramified  glands, 
which  are  straight  or  slightly  flexuous  at  their  extremities.  At  the  cervix, 
these  glauds  enlarge  at  the  bottom,  and  assume  something  of  the  aj)i3earance 
of  acinous  glands. 

(These  mucous  glands  are  designated  simple  and  cylindrical.  The  first 
are  most  numerous  towards  the  cervix;  some,  here  and  there,  with  their 
orifices  closed,  are  enlarged,  and  form  small  vesicular  tumours,  the  ovula 
Nabothi ;  they  secrete  the    peculiar  transparent  mucus  found   here.      The 

'  Unstriped  contractile  fibres  are  also  fouml,  in  the  male,  along  the  spermatic  cord, 
beneath  the  vitceral  layer  of  the  tunica  vaginalis. 


880  THE  GENERATIVE  AFP  ABATES. 

cylindrical,  uterine,  or  utricular  glands  are  closely  clustered  together, 
sometimes  bifurcated,  often  twisted  m  a  spiral  fashion,  and  terminating  in  a 
cul-de-sac  in  the  substance  of  the  membrane.  In  structure  they  resemble 
other  mucous  glands,  consisting  of  a  membrana  propria,  an  epithelium  of 
spheroidal  cells  at  the  bottom  of  the  tube,  and  of  columnar  cells  in  its  duct. 
During  gestation  they  are  much  enlarged,  and  receive  the  cotyledonal 
processes  of  the  placenta.  At  the  period  of  oestrum,  the  glandular  secretion 
of  the  uterus  is  more  active  than  at  other  times.) 

Vessels Nerves. — The  blood  brought  to  the  uterus  by  the  tderine-  and 

utero-ovarian  arteries,  is  conveyed  from  it  by  veins  corresponding  to  the 
latter.  In  animals  which  have  been  pregnant  several  times,  the  vessels  are 
remarkable  for  their  enormous  volume  and  their  tortuousness.  (The 
arteries  freely  anastomose ;  they  ramify  through  the  muscular  and  mucous 
tunics,  constituting  coarse  and  fine  networks  which  ultimately  end  in  the 
veins.  These  are  very  large  and  have  no  valves  ;  the  plexuses  they  form 
are  considerable.) 

The  lymphatics  that  pass  from  the  uterus  are  as  remarkable  for  their 
number  as  their  dimensions  ;  they  reach  the  sublumbar  region. 

The  nerves  supplying  the  organ  come  from  the  small  mesenteric  and 
pelvic  plexuses.  (In  the  uterus  there  are  several  important  nervous  gan- 
glia ;  and  during  gestation  it  has  been  ascertained  that  the  nerves,  like  the 
vessels,  enlarge,  and  after  parturition  return  to  their  former  size.) 

Development. — Narrow  in  the  foetus,  and  in  the  adult  which  has  not  been 
impregnated,  the  uterus  increases  in  size  in  animals  which  have  had  young 
several  times. 

Functions. — The  uterus  is  the  sac  in  which  the  embryo  is  developed. 
The  ovulum  grafts  itself  upon  the  mucous  membrane  of  the  organ  by  its 
placental  apparatus,  in  order  to  draw  indirectly,  from  the  maternal  blood, 
the  materials  for  its  development.  This  function  of  the  uterus  gives  rise 
to  most  interesting  anatomical  and  physiological  considerations,  which  will 
be  referred  to  when  giving  the  history  of  the  ovum. 

4.  The  Vagina.     (Figs.  411,  412.) 

The  vagina  is  a  membranous  canal  with  thin  walls ;  it  succeeds  the 
uterus,  and  terminates  posteriorly  by  an  external  opening — the  vulva. 

Situation  and  Relations. — Situated  in  the  pelvic  cavity,  which  it  passes 
horizontally  across,  the  vagina  is  in  relation  with  the  rectum  above,  below 
with  the  bladder,  and  laterally  with  the  sides  of  the  pelvis  and  ureters. 
Loose  connective  and  adipose  tissue  surroimd  it  posteriorly. 

Internal  conformation. — The  inner  surface  of  the  vagina  is  always  lubri- 
cated by  an  abundance  of  mucus,  and  is  ridged  by  longitudinal  folds  (co- 
lumnre  rugosce).  In  front,  at  the  bottom  of  the  canal,  is  observed  the 
projection  formed  by  the  cervix  uteri ;  posteriorly,  this  sin-face  is  continuous 
with  that  of  the  vulva. 

Structure. — The  vagina  is  formed  of  two  tunics;  an  inner,  mucous,  and 
an  external,  muscular.  The  mucous  membrane  (pale-red  in  colour)  is  con- 
tinuous with  that  lining  the  vulva  and  the  uterus  (and  bladder) ;  it  is 
provided  with  papillfe,  and  is  lined  by  stratified  pavement  (squamous) 
epithelium.  (It  consists  of  connective  and  elastic  tissue,  to  which  its 
extensibility  and  firmness  are  due.) 

The  muscular  coat  is  rose-coloured,  and  traversed  by  a  large  number  of 
vessels  ;  it  is  surrounded,  for  the  greater  part  of  its  extent,  by  an  abundance 


THE  FEMALE  GENITAL  ORGANS.  881 

of  connective  tissue  wliicli  joins  it  to  the  organs  contained  in  the  i^clvic 
cavity ;  in  front,  however,  it  is  envcloiicd  by  the  peritoneum  which  sur- 
rounds the  vagina  before  passing  to  the  uterus.     (This  connective  tissue  is 


s  2  c 


E  o  fi 

—  .-«    t) 

•— •  r3    D 


o  a 


~  S      1^      ^H 

**  .^  '-H  ^ 

K  o  is 

H  Si, 


Ol  o  '"' 

"if 


sometimes  designated  the  tldrd  or  fibrous  tunic  of  the  vagina.     The  mus' 
cular  fibres  are  unstriped.  and  arranged  in  circular  and  longitudinal  series ; 
towards  the  posterior  portion  of  the  canal  they  are  redder  than  in  front.) 
Vessels  and  nerves. — The  vagina  is  supplied  with  blood  by  the  internal 


882  THE  APPABATVS  OF  GENERATION. 

pudic  artery ;  this  fluid  is  carried  from  it  by  numerous  veins,  wliicli  are 
disposed  in  a  plexus  around  the  canal,  and  enter  the  satellite  of  the 
artery.  The  nerves  come  from  the  pelvic  plexus.  (The  lymphalics  accom- 
pany the  veins,  and  pass  to  the  pelvic  glands.) 

Function. — The  vagina  receives  the  male  organ  during  copulation,  and 
through  it  the  foetus  passes  during  parturition. 

5.  The  Vulva.     (Fig.  411.) 

The  external  orifice  of  the  vagina,  the  vulva  is  situated  in  the  perineal 
region,  immediately  below  the  anus.  We  will  consider  in  succession  its 
external  opening,  its  caviiy,  and  its  structure. 

External  Opening. — This  is  a  vertical  elongated  slit,  presenting  two 
lips  and  tivo  commissures.  The  lips  (labia  vulvce)  are  covered  externally  by  a 
fine  smooth,  unctuous,  and  (almost)  hairless  skin,  rich  in  colouring  pigment, 
and  lined  internally  by  mucous  membrane ;  on  their  free  margin,  the  limits 
of  these  two  membranes  are  well  marked.  The  superior  commissure  is  very 
acute,  and  almost  meets  the  anus,  from  which  it  is  nevertheless  separated  by 
a  narrow  space— the  perineum.  The  inferior  commissure  is  obtuse  and 
rounded ;  it  lodges  the  clitoris. 

Cavity  of  the  Vulva. — By  all  Veterinary  authorities,  this  cavity  is 
described  as  belonging  to  the  vagina,  to  which  it  forms  the  entrance ;  but 
considering  the  analogies  that  exist  between  the  genital  jiarts  of  Woman  and 
those  of  animals,  this  cavity  must  be  distinguished  from  that  of  the  vagina. 
It  offers  for  study  the  hymen,  which  separates  the  two  cavities,  the  meatus 
urinarius  and  its  valve,  and  the  clitoris. 

The  Clitouis. — Exactly  similar  to  the  corpus  cavernosum  of  the  male, 
which  it  represents  in  miniature,  and  2  to  3  inches  in  length,  the  clitoris 
commences  by  two  crura  fixed  to  the  ischial  arch,  and  covered  by  a 
rudimentary  ischio-cavernosum  muscle.  After  being  attached  to  the 
symphysis  by  means  of  a  suspensory  ligament  analogous  to  that  of  the 
male,  it  passes  backwards  and  protrudes  into  the  vulvular  cavity,  tow%ards 
the  inferior  commissure.  Its  free  extremity,  lodged  in  that  cavity,  is 
enveloped  by  a  mucous  cap — the  prepuce  of  the  clitoris  (prceputium  clitoridis), 
which  is  folded  in  various  directions,  and  excavated  about  the  centre  of  the 
tubercle  by  a  small  follicular  cavity  that  represents  the  extremity  of  the 
male  penis.  The  organisation  of  the  clitoris  resembles  in  every  particular 
that  of  the  corpus  cavernosum  of  the  penis  :  a  fibrous  framework,  erectile 
tissue,  and  cavernous  vessels.  It  is  the  contact  of  the  penis  with  this 
organ  during  copulation  that  chiefly  occasions  the  venereal  excitation. 

The  Meatus  Urinarius  and  its  Valve. — The  urethral  canal  in  the 
female  is  very  short.  It  passes  immediately  beneath  the  anterior  sphincter 
muscle  of  the  vulva,  and  after  a  brief  course  in  the  texture  of  the  floor  of 
the  vagina,  it  opens  into  the  vulvular  cavity  by  an  orifice  covered  by  a  large 
mucous  valve  :  this  is  the  meatus  urinarius  and  its  valve.  The  urinary 
opening,  placed  at  the  bottom  of  the  cavity,  at  from  3i  to  5  inches  from  the 
external  opening,  is  wider  than  the  male  urethra,  and  will  admit  sounds  of 
somewhat  large  calibre,  for  the  catheterism  of  the  bladder.  The  valve  has 
its  free  border  inclining  backwards,  to  direct  the  flow  of  urine  towards 
the  exterior,  and  prevent  its  reflux  into  the  vagina. 

(The  female  urethra  is  composed  of  two  tunics  :  a  mucous,  continuous 
with  that  of  the  bladder  and  vagina;  and  a  muscular  coat,  also  a  con- 
tinuation of  that  belonging  to  these  organs,  and  chiefly  made  up  of  circular 


THE  FEMALE  GENITAL  ORGANS.  883 

fibres ;  some  flat  fasciculi  attach  it  to  tlie  periosteum  of  the  ischia.  The 
urethra  is  not  surrounded  by  a  spongy  body  as  in  the  male.) 

The  Hymen. — This  membrane,  when  it  exists,  distinctly  separates  the 
vulvular  from  the  vaginal  cavity.  It  is  rarely  present,  however ;  though 
we  have  observed  it  several  times  in  the  adult  Mare.  It  forms  a  circular 
partition,  fixed  by  its  margin  to  the  vulvo-vagiual  walls,  as  well  as  to  the 
valve  of  the  meatus  urinarius,  and  is  jjerforated  by  one  or  more  openings 
which  establish  a  commimication  between  the  vulva  and  vagina.  On  many 
occasions  we  have  found,  in  old  brood-mares,  pedicul'ated  appendages,  the 
remains  of  this  septum. 

Structure  of  the  Vulva. — The  vulva  offers  for  study  in  its  structure  : 
1,  The  mucous  membrane  lining  its  interior :  2,  An  erectile  body  lying  on 
that  membrane,  and  named  the  vaginal  bulb;  3,  Two  constrictor  muscles — 
anterior  and  posterior ;  4,   Two  muscular  ligaments  ;  5.  The  external  shin. 

1.  Mucous  membrane. — Continuous  with  that  of  the  vagina  and  bladder, 
this  membrane  has  a  rosy  colour,  which  may  become  a  bright-red  at  the 
period  of  heat.  It  often  shows,  near  the  free  border  of  the  labia,  black 
pigment  patches,  which  give  it  a  speckled  appearance.  It  has  in  its 
substance  a  greater  quantity  of  mucous  follicles  and  sebaceous  glands. 
The  latter  exist  near  the  free  border,  particularly  about  the  clitoris,  and  es- 
pecially in  the  space  between  that  erectile  body  and  the  inferior  commissure 
of  the  vulva,  where  they  meet  in  several  small  sinuses.  (These  glands 
secrete  an  unctuous  matter  possessing  a  special  odoui* ;  they  are  most  active 
during  oestrum.) 

2.  Vaginal  bulb. — This  is  an  organ  entirely  formed  of  erectile  tissue 
with  wide  areolfe ;  it  is  divided  into  t\\o  branches  (biilbi  vestibuli),  which 
arise  from  the  vicinity  of  the  crura  of  the  clitoris  and  pass  on  the  sides 
of  the  vulva,  where  they  terminate  in  a  round  lobe.  Covered  by  the 
posterior  constrictor  of  the  vulva,  the  vaginal  bulb  communicates,  inferiorly, 
with  the  veins  of  the  corpus  cavernosum.  The  influx  of  blood  into  the 
cells  of  its  tissue  contracts  the  vulvular  cavity,  and  concurs  to  render  the 
coaptation  of  the  copulatory  organs  more  perfect  during  coition. 

3.  Muscles  of  the  vulva. — Imperfectly  described  and  determined  in  books 
on  Veterinary  Anatomy,  these  belong  to  the  category  of  voluntary  muscles. 
We  recognise  two,  which  will  be  described  as  the  posterior  and  anterior 
constrictors. 

Posterior  Constrictor  of  the  Vulva. — Analogous  to  the  constrictor 
vagince  of  Woman,  this  muscle,  included  in  the  labia  of  the  vulva,  forms  a 
veritable  sphincter.  Above,  its  fibres  are  mixed  with  those  of  the  sphincter 
ani,  and  are  attached  to  the  sacrum  through  the  medium  of  the  suspensory 
ligaments.  Inferiorly,  the  most  anterior  are  fixed  to  the  base  of  the  clitoris; 
the  middle  are  prolonged  to  between  the  thighs,  and  are  inserted  into  the 
inner  surface  of  the  skin. 

Inwardly,  it  is  in  relation  with  the  vaginal  bulb  and  the  mucous 
membrane  of  the  vulva.  Its  external  face  is  separated  from  the  skin  of  the 
labia  by  a  very  vascular  cellulo-filirous  tissue  capable  of  contraction,  and 
in  the  midst  of  which  are  always  found  isolated  red  fasciculi — dependencies 
of  the  principal  muscle. 

This  muscle,  in  contracting  during  copulation,  constricts  the  aperture  of 
the  vagina  and  compresses  the  penis ;  and  as.  in  consequence  of  its  attach- 
ment to  the  clitoris,  it  cannot  act  without  raising  that  erectile  body,  it 
applies  this  to  the  male  organ  and  causes  a  greater  degree  of  excitement. 
With  animals  in  heat,  the  movements  of  the  clitoris  are  frequently  observed 


884  THE  APPARATUS  OF  GENERATION. 

to  proijel  tliat  organ  outwards,  especially  after  micturation ;  in  tliis  case,  tlie 
fibres  of  tlie  constrictor  attached  to  the  clitoris  erect  it  by  its  base,  while 
those  which  are  fixed  into  the  skin  between  the  thighs  depress  the  inferior 
commissure  of  the  vulva.  This  double  action  necessarily  exposes  the 
erectile  tubercle  lodged  in  that  commissure. 

Anterior  Constrictor  of  the  Vulva. — Analogous  to  Wilson's  muscle 
in  the  male,  this  constrictor  is  formed  of  arciform  fibres  which  envelop, 
below  and  laterally,  the  vaginal  walls  at  the  entrance  of  the  canal ;  its 
extremities  are  continued,  by  means  of  aponeurotic  fascia,  to  the  sides 
of  the  rectum,  where  they  are  lost.  By  its  posterior  border,  this  muscle 
is  mixed  with  the  preceding. 

4.  Muscular  ligaments  of  the  vulva. — Traces  of  the  suspensory  cords  of 
the  male  penis,  these  ligaments  are  disposed  in  the  same  manner  at  their 
origin.  After  becoming  united  beneath  the  rectum,  they  descend  in  several 
fasciculi  into  the  labia  of  the  vulva,  and  disappear  among  the  fibres  of  the 
posterior  constrictor. 

5.  External  shin. — This  is  fine  and  black  (or  light-coloured),  destitute  of 
hair,  smooth  and  unctuous,  and  adheres  closely  to  the  subjacent  tissues. 

6.  The  Mammce. 

The  mammce  are  glandular  organs,  Avhich  secrete  the  fluid  that  should 
noui-ish  the  young  animal  during  the  early  months  of  its  life.  They  are 
rudimentary  in  youth,  and  become  developed  with  the  advent  of  puberty, 
assuming  their  greatest  development  towards  the  end  of  gestation ;  they  are 
most  active  after  parturition,  and  cease  their  function,  as  well  as  diminish 
in  volume,  when  the  period  of  lactation  has  terminated. 

Situation. — These  glands  are  two  in  number,  placed  beside  each  other  in 
the  inguinal  region,  where  they  occupy  the  situation  of  the  scrotum  in  the 
male. 

Form. — They  are  two  hemispherical  masses,  separated  from  each  other 
by  a  shallow  furrow,  and  showing  in  their  centre  a  prolongation  called  the 
teat,  nipple  {dug),  or  mammilla,  which  is  pierced  at  its  free  extremity  by  several 
orifices  for  the  escape  of  the  milk ;  it  is  by  this  prolongation  that  the  young 
animal  effects  suction. 

The  two  glands  are  fixed  in  their  position  by  the  skin  which  covers 
them,  and  which  is  thin,  black,  covered  with  a  fine  down,  and  altogether 
destitute  of  hair  in  the  vicinity  of,  or  on,  the  teat,  where  the  cutaneous 
surface  is  smooth,  greasy,  and  supple.  They  are  also  attached  to  the 
tunica  abdominalis  by  several  wide,  but  short,  elastic  bands,  which  resemble 
the  ligaments  of  the  sheath  in  the  male. 

Structure. — Structurally,  the  mammary  glands  offer  for  study :  1,  A 
yelloio  (elastic)  fibrous  envelope;  2,  Glandular  tissue;  3,  The  galactoferous 
reservoirs  or  sinuses  ;  4,  The  excretory  canals  or  mammary  ducts. 

The  elastic  envelope,  placed  in  the  middle,  beside  its  fellow  of  the 
opposite  side,  is  mixed  with  the  suspensory  bands  that  descend  from  the 
abdominal  tunic,  and  sends  into  the  substance  of  the  gland  a  number  of 
septa,  which  are  interposed  between  the  principal  lobules. 

The  glandular  tissue  is  a  compound  of  gland  vesicles  or  acini,  clustered  in 
groups  around  the  lactiferous  ducts.  (The  gland  vesicles  are  made  up  of 
an  amorphous  membrane,  memhrana  propria,  lined  with  spheroidal  nucleated 
cells.  They  are  about  l-200th  of  an  inch  in  diameter.)  The  lactiferous 
ducts  commence  by  blind  extremities,  and  run  into  each  other  to  constitute 


THE  FEMALE  GENITAL  OEGAXS. 


885 


a  certain  number  of  principal  canals :  these  open  into  the  galactoferous  sinuses 
(each  a  saccuJus  vcl  sinus  lacti/erus).  The  glandular  culs-de-sac  are  lined 
with  a  polyhedral  epithelium,  which  becomes  spherical  and  infiltrated  with 
fat  during  lactation. 


Ficr.   41  O. 


Fisf.  414. 


GLAND-VESICLES,     WITH    THEIR     EXCRETORY  ULTIMATE    FOLLICLES,    OR    GLAND    VESICLES, 

DUCTS    TERMINATING    IN   A    DUCTUS    LAC-  WITH   THEIR    EPITHELIUM    OR   SECRETING 

TIFEROUS:  FROM  A  MERCURIAL  INJECTION;  CELLS,   a,  a,    AND   NUCLEI,   b,  b. 
MAGNIFIED   FOUR   TIMES. 

Placed  at  the  base  of  the  teat,  the  galactoferous  sinuses  or  reservoirs  are 
generally  two  in  number,  but  sometimes  there  are  three,  and  even  four ; 
they  nearly  always  communicate  with  each  other,  and  are  continued  into  the 
mammilla  by  an  equal  number  of  independent  excretory  canals — the  definitive 
duets,  whose  orifices  are  very  small,  and  are  seen  beside  each  other  at  the  free 
extremity  of  the  teat.  A  fine  mucous  membrane  lines  the  inner  face  of  this 
excretory  apparatus ;  it  is  doubled  in  the  teat  by  a  thick  layer  of  tissue, 
which  again  is  covered  by  the  skin  that  adheres  closely  to  it.  (Between 
the  external  and  internal  tunic  of  the  teats,  are  found  numerous  fasciculi 
of  unstriped  muscular  fibres,  arranged  in  a  circular  and  longitudinal  manner 
around  these  ducts.) 

Connective  tissue,  vessels  and  nerves,  complete  this  organisation.  (The 
arteries  are  from  the  external  pudic  trunk ;  the  veins  are  very  numerous,  and 
pass  to  the  trunk  of  the  same  name ; 

the  nerves  are  derived  from  the  first  F'§-  "^l^- 

lumbar  pair.) 

Fl'nctions. — Tlie  mammfe  secrete 
the  milk ;  they  undergo  remarkable 
modifications  at  puberty  and  at  the 
end  of  each  gestation — modifications 
which  are  related  not  only  to  their 
volume  and  secretion,  but  also  to 
their  minute  structure.  After  ges- 
tation, the  gland- vesicles  shrink: 
become,  as  it  w^ere,  atrophied,  and 
have  only  a  polygonal  epithelium. 
At  the  termination  of  gestation,  they 
are  enlarged,  new  vesicles  are  de- 
veloped, and  the  epithelium  changes 
its  character :  filling  the  gland  cavi- 
ties, assuming  a  spherical  shape,  and 
becoming  charged  with  fat  granula- 
tions. The  period  of  lactation  being 
completed,  the  mammte  take  on  their 
former  character.     (In  Mares  which 

have  not  been  bred  from,  the  mammte  are  hard  and  small,   the  teats  but 
slightly  prominent,  and  the  glandular  tissue  scanty.     In  old  brood-mares, 
59 


.b%° 


oo  Oo  »0 


O    Or 


^  Of 


O     o'a    V  Ar\-P  oO_ 


0  00 

MICROSCOPIC  APPEARANCE  OF  MILK,  WITH  AN 
INTERMIXTURE  OF  COLOSTRIC  CORPUSCLES 
AT    a,  a,    AND    ELSEWHERE. 


886  THE  APPARATUS  OF  GEXEEATION. 

on  the  contrary,  they  are  flaccid  and  pendant,  and  the  teats  somewhat 
lengthened.  The  milk  secreted  by  the  mammary  glands  is  a  white  fluid, 
possessing  a  sweet  taste,  and  composed  of  an  albuminous  water  containing 
caseine  in  solution,  milk  sugar,  salts,  and  fatty  matter  in  globules— the 
butter.  Usually  a  small  quantity  is  secreted  some  days  before  parturition  ; 
that  which  is  yielded  for  a  short  time  after  that  period  is  named  colostrum  ; 
it  is  rich  in  white  corpuscles  and  has  purgative  properties.  The  colostrum 
is  of  a  rich  yellow  colour,  less  fluid  than  the  milk  of  a  later  period,  of 
a  higher  specific  gravity,  slightly  acid,  and  containing  large  oil-globules,  a 
few  irregular  flakes,  probably  epithelium  scales,  a  little  granular  curd-like 
matter,  and  a  small  number  of  granular  corpuscles.) 

DIFFERENTIAL  CHAEACTERS   IN   THE   FEMALE    GENITAL   ORGANS   OF   OTHER   THAN   SOUPED 

ANIMALS. 

Certain  organs  offer  some  differences  worthy  of  notice,  while  others  are  formed  as  in 
Solipeds. 

Ruminants. — Ovaries. — In  the  Cow,  the  ovaries  are  relatively  much  smaller  than  in 
the  Mare,  but  their  form  and  structure  are  identical.  (The  Graafian  vesicles  are  visible 
throui^h  the  tunica  albuginea.) 

Uterus. — 'I"he  uterus  of  the  Cow,  compared  with  that  of  the  Mare,  offers  but  few 
differences  with  regard  to  its  general  disposition  in  the  pelvic  and  abdominal  cavities, 
except  that  it  is  not  so  advanced  in  the  latter.  Supposing  the  uterus  to  be  perfectly 
horiztmtal.  a  transverse  line  drawn  through  tlie  plane  of  the  abdomen,  before  the  external 
angle  of  the  ilium,  is  exceeded  by  the  extremity  of  the  cornua  about  1.^  to  2  inches ;  so 
that  if  the  anini'-d  wore  on  its  back,  the  uterus  would  be  only  prolonged  to  the  fourth  or 
fifth  lumbar  vertebra. 

With  regard  to  form,  the  uterus  of  the  Cow  pre-ents  a  very  remarkable  disposition, 
which  it  is  necessary  to  note  :  the  concave  curvature  of  the  coi'nun  looks  downwards, 
while  in  the  Mare  it  looks  upwards ;  though  in  both  the  sublumbar  ligaments  are 
attached  to  this  concavity.  Therefore  it  is  that  in  the  Cow,  if  we  consider  the  uterus  as 
freely  suspended  in  the  abdomen,  the  extremity  of  the  cornua  is  twisted  outwards  and 
upwards,  while  the  base,  although  drawn  in  the  same  direction  by  these  ligaments, 
maintains  its  direction,  because  it  is  in  a  manner  fixed  by  the  body  of  (he  uterus.  The 
latter  receives,  like  the  cornua,  the  insertion  of  the  broad  ligaments  on  its  lower  plane, 
so  that  it  overlaps  them,  while  the  uterus  of  the  Mare  projects  below  them.  Otherwise, 
these  ligaments  are  very  amfile.  especially  at  their  anterior  border ;  they  are  wide  apart  in 
front,  towards  their  lumbar  aitachment,  which  is  prolonged  even  on  the  parietes  of  the 
fl.mk.  The  ligaments  may  be  altogether  compared  to  a  triangular  cravat,  one  angle  of 
which  is  attached  to  the  bottom  of  the  pelvic  cavity,  and  the  other  two  to  the  tuberosities 
of  tlie  ilium.     On  this  cravat  lies  the  body  and  part  of  the  cornua  of  the  uterus. 

The  uterine  cornua  are  thin  and  tapering  at  fheir  anterior  extremity.  The  budy  is 
short  aid  narrow. 

The  interior  of  the  uterus  of  the  Cow  is  less  ample  than  that  of  the  Mare.  Its 
surf  ice  is  studded  with  rounded  tubercles,  known  as  cotyledons,  which  will  be  studied 
hereafter.  It  is  only  necessary  to  say  here  that  they  are  numerous  in  the  cornua,  but 
small  and  few  in  the  b:idy  of  the  organ. 

The  cervix  uteri,  about  from  2f  to  3J  inches  long,  is  narrow  and  irregular.  The 
"expanded  flower,"  more  finely  plicated  tl.an  in  the  Mare,  is  almo.-^t  cartilaginous. 
Three  other  pl'cated  rings,  each  smaller  than  the  other,  are  e'chelonned  in  the  cavity  of 
the  cervix,  from  the  external  orifice  to  the  body  '^corresponding  to  the  plicx  palmatie  or 
arbor  vitx  uteriiia  of  Woman). 

In  structure,  the  muscular  layer  is  generally  thicker  than  in  Solipeds. 

In  the  Sheep  and  Goat,  the  arrangement  is  the  same  as  in  the  Cow,  except  ti.at  ihe 
cotyledons  are  hollowed  like  a  cup  in  their  centre,  and  deserve  their  name.  (The  cornua 
are  longer  and  more  pendent  tiian  in  the  Cow.) 

Vagina. — In  the  Cote,  the  sides  of  the  vagina  are  traversed,  for  a  certain  distance,  by 
a  mucous  canal  that  opens  into  the  vulvular  cavity,  beside  the  meatus  urinarius.  These 
ducts,  the  use  of  which  is  unknown,  are  designated  the  canals  of  Gtertner.  They  are 
not  present  in  the  Slwep  or  Goat.  (In  Ruminants,  the  vagina  is  longer  and  its  external 
tunic  thicker  than  in  the  Mare.  Leyh  describes  the  canals  of  Gartner  as  present  in  the 
Mare,  though  rarely.) 

Vulva. — This  has  thick  lips  in  the  Cow.     The  inferior  commissure  is  acute,  and 


THE  FEMALE  GENITAL  ORGANS.  887 

furnished  with  a  tuft  of  hair.  (The  corpus  cavernosum  of  tho  clitoris  is  longer,  thinner, 
and  more  ficxuoiis,  and  the  gland  much  smaller  than  in  the  Mare.)  The  meatus 
urinarius  is  disposed  as  in  the  mare  ;  hut  tliere  exists,  on  the  floor  of  tlie  urethra,  a  valve 
whose  free  border  is  dir.'Ctod  backwards.  This  valve  surmounts  a  small  cul-de-sac 
which  it  is  necessary  to  avoid  in  catlcterism  of  the  bladder.  At  about  an  inch  from  the 
entrance  to  the  vulva,  there  are  found  in  the  texture  of  the  labia  the  vulvo-vaginal  glands 
(glands  of  Barlholine).  Discovered  by  Duverney,  described  by  Bartholine,  and 
recently  by  Colin,'  these  glands  (two  in  number)  are  about  the  size  of  a  large  almond  ; 
Iheir  wide  extremity  is  directed  upwards,  and  the  narrow  end,  situated  iu  the  vicinity 
of  the  ischio-ditorilis  muscle,  gives  origin  to  the  excretory  canaliculi.  They  are 
racemose,  and  their  ducts  unite  to  form  a  kind  of  sinus,  which  at  length  opens  in  the 
vaginal  cavity,  about  4  inches  from  the  labia  of  the  vulva.  (, These  glandulx  vaginm  are 
supposed  to  be  analogous  to  the  prostate  glands,  and  are  covered  by  muscular  fasciculi. 
They  are  composed  of  pyriform  glandular  vesicles,  lined  by  squamous  epithelium,  and 
surrounded  by  a  dense  nucleated  connective  tissue ;  the  excretory  ducts  are  invested  by 
columnar  epithelium,  and  surrounded  by  a  thin  layer  of  smooth  muscle-cells,  disposed 
longitudinally.     Their  secretion  is  a  clear,  yellowish,  viscid  mucus.) 

(In  the  Sheep  and  Goat,  the  labia  of  the  vulva  have  several  folds  externally,  and  the 
inferior  commissure  terminates  in  a  point.) 

Mammx. — In  the  Cow,  each  lateral  mammary  mass,  although  enclosed  in  a  single 
fibrous  capsule,  is  composed  of  two  distinct  glands,  each  having  its  teat ;  so  that  this 
animal  really  has  four  mammx  ami  four  teats.  There  are  also  frequently  found  behind 
these,  two  rudimentary  imperforate  "(sometimes,  though  very  rarely,  perforate)  teats. 

In  the  centre  of  each  gland,  at  the  base  of  the  teat,  is  a  single  galadofermis  sinus,  the 
general  confluent  of  all  the  lactiferous  ducts — a  wide  cavity  opening  at  the  extremity  of 
the  teat  by  a  definitive  excretory  canal.  (The  mammae  of  the  Cow  occupy  the  same 
region  as  those  of  the  Mare,  and  the  teats  are  longer  and  thicker.) 

In  the  Sheep  and  Goat,  there  are  only  two  mammae,  as  iu  the  Mare  and  Ass,  though 
they  are  formed  as  in  the  Cow.  The  Goat  has  frequently  two  posterior  rudimentary 
mammse. 

Pig. — The  ovary  of  the  Soto  has  a  lobulated  aspect,  like  the  ovary  of  birds  This 
appearance  is  due  to  the  ovisacs  which,  when  they  are  well  developi  d,  project  beyond 
the  surface  of  the  ovarium,  instead  of  remaining  encysted  in  its  stroma.  The  oviduct 
is  less  flexuous,  but  its  length  is  proportionately  greater  than  in  the  other  species.  The 
body  of  the  uterus  is  short,  but  the  cornua  are  very  long  aud  folded,  and  float  amongst 
the  intestinal  convolutions.  (Its  cervix  does  not  project  into  the  vagina,  and  the  two 
cavities,  vagina  and  uterus,  are  continued  into  each  other  without  any  marked  limit 
between  them.  The  mucous  membrane  is  very  loose,  soft,  and  fine  to  the  touch,  and  its 
surface  is  gathered  up  into  numerous  folds  of  various  forms.  The  broad  ligaments 
resemble  the  mesentery,  and  the  cornua  join  the  Fallopian  tubes  without  any  very 
perceptible  limit.) 

The  vagina  shows  Gartner's  canals,  as  in  the  Cow.  Cits  mucous  membrane  has 
numerou.  longitudinal  folds  anteriorly ;  and  in  front  a  multitude  of  fine  points,  which 
are  the  excretory  ducts  of  small  glands  analogous  to  the  prostates.  On  the  sides  of  the 
meatus  urinarius  are  two  small  fossettes  surrounded  by  a  ring.  There  is  no  vaginal  valve.) 
The  inferior  commissure  of  the  vuh-a  is  more  acute  than  in  Ruminants.  The  mammaj 
are  ten  in  number,  disposed  in  two  rows,  extending  from  the  inguinal  region  to  below 
the  chest  They  have  no  galactoferous  reservoirs,  as  iu  the  larger  Ruminants :  the 
lactiferous  ducts  uniting  directly  info  a  variable  number  of  definitive  canals  that  pass 
through  the  teat,  to  pierce  its  extremity  by  from  five  to  ten  orifices.  (There  are,  of 
course,  five  or  six  glands  in  each  row,  each  with  its  teat.) 

Carnivoea. — In  the  Dog  and  Cat,  the  ovaries  and  uterus  are  disposed  as  in  the  Pig ; 
the  ovaries  (are  situated  behind  the  kidneys,  and)  are  lodged  in  a  particular  fold  of  the 
broad  ligaments,  which  forms  a  kind  of  cup.  There  are  no  Gsertner's  canals  in  the 
vagina.  The  vidva  of  the  Dog  is  triangular,  and  acute  at  its  inferior  commissure.  The 
Cat  has  a  small  bone  in  the  clitoris.  The  mamma;  are  ten  in  number  in  the  Dog,  and 
eight  hi  the  Cat ,  they  are  distinguished,  as  in  the  Pig,  into  inguinal,  abdominal,  and 
pectoral.  (Each  teat  has  from  eight  to  ten  oriOces.  The  vagina  is  long,  and  wider  at 
the  vulva  than  towards  the  uterus.  Beside  the  smooth  muscular  fibres  of  its  external 
coat,  it  has  white  fibres  wliich  give  it  greater  thickness  and  resistance.  The  mucous 
mfembrane  forms  longitudinal,  intersected  by  transverse,  folds ;  the  valve  of  the  meatus 
uiinarius  scarcely  exists.  The  cervix  of  the  uterus  projects  into  the  vagina,  and  is  even 
more  voluminous  than  the  body,  which  is  short;  it  is  hard  to  the  touch.) 

'  '  Traite  de  Physiologie  Compare'e  des  Animaux  Domestiques.'    Paris,  1871. 


888 


TME  APPARATUS  OF  GENERATION. 


COMPARISON   OP  THE   GENERATIVE   ORGANS   OF   WOMAN   WITH   THOSE   OP  ANIMALS. 

Ovaries. — These  organs  are  oval,  about  IJ  inches  long  and  8-lOths  of  an  inch  broad, 
and  are  lodged  in  the  posterior  layer  of  the  broad  ligaments.  They  are  attached  to  the 
uterus  by  the  ligament  of  the  ovary,  and  united  to  the  Fallopian  tubes  by  the  Fallopio- 
ovarian  ligament.  Their  structure  is  the  same  as  in  animals.  A  Graafian  vesicle 
usually  ripens  every  month ;  its  rupture  corresponds  with  the  menstrual  period. 
Annexed  to  the  human  ovary  is  found  the  organ  of  Eoseiimiiller,  composed  of  from  fifteer^ 
to  twenty  tortuous  tubes  opening  into  a  transverse  branch  ;  these  tubes  ai-e  lined  by 
ciliated  epithelium,  and  iilled  with  a  yellow  fluid  ;  they  form  a  closed  system  included 
in  the  broad  ligament,  between  the  ovary  and  oviduct. 

Oviduct— Placed  at  the  upper  border  of  the  broad  ligament,  it  is  nearly  straight,  and 
terminates  by  a  pavilion  notched  into  about  fifteen  unequal  fringes. 

Uterus. — ^The  human  uterus  is  situated  between  the  bladder  and  rectum,  being  inclined 

Fig.  416. 


UTERUS  WITH   ITS   APPENDAGES,    VIEWED   FROM   THE   FRONT. 

1,  Body  of  the  uterus ;  2,  Fundus ;  3,  Cervix ;  4,  Os  uteri ;  5,  Vagina,  with  its 
columna  and  transverse  rugte;  6,  6,  Broad  ligament  of  the  uterus;  7,  Convexity 
of  the  broad  ligament  formed  by  the  ovary ;  8,  8,  Round  ligaments  of  the  uterus ; 
9,  9,  Fallopian  tubes:  10,  10,  Their  fimbriated  extremities;  11,  Ovary;  12, 
Utero-ovarian  ligament ;  13,  Fallopio-ovarian  ligament ;  14,  Peritoneum  of 
anterior  surface  of  uterus ;  it  is  removed  at  the  left  side,  but  on  the  right  is 
continuous  with  the  anterior  layer  of  the  broad  ligament. 

slightly  downwards,  from  before  to  behind.  Its  form  is  very  different  from  the  uterus  of 
the  animals  we  have  described,  being  that  of  a  flattened  gourd  ;  its  volume  varies  with 
age  and  the  number  of  gestations ;  it  weighs  about  two  ounces.  It  is  descrited  as  having 
a  body  and  cervix.  The  bod;/  is  triangular,  and  at  the  extremities  of  its  upper  border 
the  oviducts  open  into  it.  The  cervix  is  fusiform  ;  the  projection  it  makes  at  the  botlom 
of  the  vagina  is  the  tench's  nose — a  transversal  slit  bordered  by  two  unequal  lips*  The 
inner  face  of  the  cervix  shows  the  j^licx  palmata3,  arborisations  formed  by  the  mucous 
membrane. 

There  is  nothing  special  to  be  noticed  in  its  structure. 

The  broad  ligaments  comprise  a  quantity  of  muscular  fibres  between  their  layers, 
and  which  accumulate  at  certain  points  to  form  accessory  folds ;  among  these  the  most 
important  are  the  round  ligaments.  These  leave  the  anterior  face  of  the  uterus,  pass 
forwaid  and  outward,  enter  the  inguinal  canal,  and  terminate  in  the  connective  tissue  of 
the  mons  Veneris. 

Vagina. — This  canal  is  about  2|  inches  wide  ;  it  is  in  contact  with  the  rectum,  and 
responds  in  front,  by  connective  tissue,  to  the  bladder  and  urethra.  Its  internal  face 
has  longitudinal  folds,  the  coliimnie  of  the  vagina,  which  are  intersected  by  transverse 
folds.  Below  the  orifice  of  the  urethra  is  the  entra^ice  to  the  vagina,  a  circular  oiiening 
partially  closed  by  the  hymen  in  virgins.  Rarely  complete,  this  membrane  may  affect 
diflerent  shapes,  and  consequently  receive  various  names,  as  horse-shoe,  bilabial, 
semilunar,  annular,  and  fringed  hymen.  When  ruptured,  it  retracts  very  much,  but 
there  always  remain  some  vestiges  of  it,  and  which  are  designated  carunctclx  myrtiformes. 

Vulva. — This  presents  a  cavity  and  an  orifice,  as  in  the  domesticated  animals;  but 
the  cavity  is  not  so  deep,  and  is  named  the  vestibule;  it  extends  to  the  hymen  or  its 
debris.  The  entrance  to  the  vulva  occurs  in  the  middle  of  a  cuneiform  prominence 
which  is  confounded,  above,  with  a  kind  of  eminence,  the  mons  Veneris,  which  appears  to 
protect  the  pubic  symphysis.    It  is  margined  by  two  folds :  one  cutaneous,  the  labia 


THE  GENERATIVE  APPARATUS  OF  BIRDS.  S89 

majora;  the  other  mucous,  the  labia  minora  (or  nymphx).  The  labia  majora  are 
convex  externally,  continuous  above  with  the  mons  Veneris,  iinci  unite  helow  to  form  an 
acute  angle,  named  the  fourchetle ;  they  are  covered  externally  with  hair.  The  labia 
minora,  more  or  less  developed,  leave  the  fourchette,  and  extend  around  the  entrance  to 
the  vagina,  uniting  above  tlie  clitoris,  and  forming  the  prepuce  of  that  organ. 

The  clitoris  is  lodged  in  the  superior  connnissure  of  the  vulva ;  its  point  is  directed 
downwards,  especially  during  erection ;  its  base  is  attached,  on  each  side,  to  the  two 
erectile  lobes  which  constitute  the  bulb  of  the  vagina  (bnlhi  vestibuii). 

Two  racemose  glands,  the  vulvo-vaginal  or  glands  of  Bartholine,  pour  their  secretior. 
over  tlie  walls  of  the  vestibule. 

Mammx. — These  are  pectoral,  and  two  in  number.  In  their  centre,  they  present  an 
enormous  papilla  —the  nipple— into  which  the  excretory  canals  open.;  it  is  surrounded  by 
a  brown  ckcle,  the  areola  of  the  nipple. 


CHAPTER  III. 

GENERATIVE   APPAEATUS    OF   BIRDS. 

1.  Male  Generative  Organs. 

The  generative  organs  of  the  male  are  the  ^esticles,  and  an  excretory  apparatus  much 
simpler  than  that  of  mammals. 

Testicles. — These  organs  are  placed  in  the  sublumbar  region  of  the  abdominal  cavity, 
behind  the  lungs,  and  below  the  anterior  extremity  of  the  kidneys.  Their  form  is 
usually  oval,  and  their  volume  varies  with  the  different  species,  as  well  as  at  different 
seasons  ;  at  the  breeding  season  they  are  greatly  developed. 

Excretory  Apparatus. — In  birds  there  is  not,  properly  speaking,  any  epididymis.  The 
vas  deferens  passes  from  within  the  jiosterior  extremity  of  the  testicle,  is  directed  in  a 
flexuous  manner  backwards,  draws  near  to  the  ureter  on  its  own  side,  going  along  the 
kidney  with  it,  and  arriving  at  the  cloaca,  where  it  terminates  by  an  oritice  to  be  alluded 
to  hereafter.  In  the  Duck,  it  has  near  its  termination  a  small  oval  vesicle,  always  filled 
with  spermatic  fluid. 

Organ  of  CopulaHon. — This  varies  with  the  species.  In  the  GalUnaex,  it  is  only 
a  small  papilla  placed  below,  near  the  margin  of  the  cloacal  opening,  and  between  the 
two  orifices  of  the  deferent  canals.  This  papilla  is  traversed  by  a,  furrow  through  which 
the  semen  flows.  In  the  Palmipedes,  this  organ  is  much  more  developed,  and  is 
peculiar.  Contained  within  a  tubular  cavity  in  the  cloaca,  it  is  protruded  externally  at 
the  moment  of  copulation  by  the  eversion  of  this  cavity,  like  a  finger  out  of  a  glove  ;  it 
then  appears  as  a  long  pendant  appendage,  twisted  like  a  cork-screw. 

2.  Generative  Organs  of  the  Female. 

The  development  of  the  young  animal  taking  place  external  to  the  female,  the 
generative  organs  are  limited  to  that  producing  the  ovum,  and  the  duct  through  which  it 
passes  on  leaving  the  ovary. 

Ovary.— In  birds  there  is  only  one  ovary,  which  is  situated  on  the  left  side,  the  right 
one  becoming  atrophied  very  early  in  nearly  all  species.  This  ovary  is  situated,  like  the 
testicles,  in  the  sublumbar  region  of  the  abdominal  cavity,  and  constitutes  a  more  or  less 
voluminous  body,  composed  of  a  variable  number  of  ovules  in  process  of  development  : 
some  very  young,  little,  and  white;  others  more  advanced  in  age,  being  larger  and 
yellow  in  colour.  The  ova  are  enveloped  in  a  very  vascular  cellular  membrane,  which, 
when  they  are  ripe,  splits  in  a  circular  manner,  following  an  equatorial  line,  and  permits 
the  escape  of  the  essential  part  of  the  egg — the  yellow  (yelk),  or  vifellus. 

Oviduct. — This  duct  is  long,  very  wide  and  dilatable,  and  very  flixuous.  It  begins, 
near  the  ovary,  by  an  unfringed  pavilion,  and  terminates  in  the  "cloaca  by  a  somewhat 
narrow  orifice,  which  is  considerably  widened  when  the  egg  passes  through  it.  The  egg, 
composed,  on  entering  the  oviduct,  of  the  fundamental  part  named  the  yelk,  or  vitellus.  is 
enveloped  in  an  albuminous  sphere  during  its  progress  towards  the  cloaca,  and  after- 
wards with  a  protecting  shell.  The  oviduct  of  birds  is,  therefore,  something  more  tiian 
an  excretory  canal,  as  it  participates  in  the  formation  of  the  ovum.  It  is  composed  of 
three  membranes  :  an  external,  serous,  maintains  the  tortuous  tube ;  a  middle,  muscular ; 
and  an  internal,  mucous. 


BOOK  IX. 

Embryology. 

Embrtologt  has  for  its  study  the  modifications  to  which  the  ovulum  is 
submitted,  from  the  moment  when  it  is  fecundated  until  it  is  transformed 
into  a  new  being  capable  of  living  in  the  external  world. 

The  points  of  this  subject  belonging  to  the  domain  of  anatomy,  will  be 
divided  into  three  chapters.  In  the  first,  the  transformations  of  the  ovulum 
which  produce  the  ovum  and  embryo  will  be  examined.  In  the  second,  the 
various  portions  of  the  ovum — the  annexes  of  the  foetus — will  be  studied ; 
and  the  third  will  be  occupied  with  tl^e  development  of  the  foetus. 


CHAPTER  I. 

THE   OVULUM  AND   ITS   MODIFICATIONS   AFTER  FECUNDATION. 

Article  I. — The  Ovulum. 
The  ovulum  of  the  domestic  mammifers  is  a  vesicle  about  xsW  ^f  an 
inch  in  diameter  (the  germinal  spot  being  from  ^^Vir  *o  24V0  ^^  ^^  inch), 
contained  in  the  ovisac,  in  the  midst  of  the  cumulus  proligera.  It  possesses 
all  the  elements  of  a  comi)lete  cell,  comprising :  1,  An  amorphous,  trans- 
parent enveloping  membrane,  named  the  vitelline  membrane,  or  zona  pell ucida  ; 
2,  A  hazy  viscous  fluid,  holding  in  suspension  a  large  number  of  dark 
granulations  and  fat  globules :  this  is  the  vitellus  or  yelk ;  3,  The  ger- 
minative  vesicle,  a  spherical,  transparent  nucleus  lying  to  one  side  of  the 
vesicle,  and  readily  altered ;  4,  The  germinal  spot,  a  kind  of  very  brilliant 
nucleolus  seen  in  the  centre  of  the  nucleus.  According  to  Balbiani,  there 
also  exists  in  the  ovulum  of  all  animals,  from  insects  up  to  mammals, 
beside  the  germinative  vesicle,  a  second  nucleus — named  Balbiani's  or  the 
emhryogenous  vesicle — which  plays  a  very  important  part  in  the  nutrition  of 
the  ovulum  and  the  phenomena  succeeding  fecundation. 

Article  II. — Modifications   in  the  Ovulum  until  the  Appearance  of 

THE  Embryo. 

These  include  the  segmentation  of  the  vitellm,  the  formation  of  the 
blastoderm,  and  the  appearance  of  the  embryo. 

1.  Segmentation  op  the  Vitellus. — Several  times  spermatozoa  have 
been  seen  in  the  vitelline  zone  of  the  fecundated  ovulum.  This  fact  is  merely 
alluded  to,  as  we  have  to  speak  of  the  consequences  of  fecundation,  and  not 


THE  F(ETUS. 


8!)1 


of  fecundation  itself.  After  it  has  taken  place,  the  germinal  vesicle  is  not 
perceived ;  has  it  disappeared,  or  changed  its  character  if  it  does  yet  exist? 
This  question  cannot  beausvvered;  all  that  is  known  is  that  it  has  ctased 
to  be  visible.  Then  the  contraction  of  the  vitcUus  begins ;  it  leaves  its 
enveloping  membrane,  becomes  depressed  in  a  circular  manner,  and  ends  by 
forming  two  independent  masses,  each  provided  with  a  nucleus.  These  two 
globes  of  segmentation  (ov  cleavaye  masses) — for  such  is  the  name  given  to 


PROGRESSIVE    STAGES    IN    THE    SEGMENTATION    OF    THE    YOLK   OF    THE    MAMMALIAN    OVUM. 

A,  Its  first  division  into  halves,  with  the  spermatozoa  around  its  circumterence ; 
B,  Subdivision  of  each  half  into  two;  C,  Further  subdivision  producing  numerous 
segments. 

them — are,  in  their  turn,  divided  into  other  two  globes,  the  number  now  being 
four.  These  four  are  once  more  divided,  and  these  again  subdivided,  until 
the  whole  mass  of  the  vitellus  is  completely  transformed  into  globules 
(or  embryo-cells),  comuosed  of  a  nucleus  covered  by  a  thin  membrane. 

¥is.  418. 


LATER    STAGE    IN   THE    SEGMENTATION    PROCESS 

A,  Mulberry  mass  formed  b_v  the  minute  subdivision  of  the  vitelline  spheres;  B,  A 
further  increase  has  brought  its  surface  into  contact  with  the  vitelline  membrane, 
against  which  the  spherules  are  flattened. 

This  is  the  segmentation  of  the  ovulum :  an  operation  that  is  always 
preceded  by  the  retraction  of  the  vitellus,  and  the  appearance  of  one  or  t\70 
small  globules  about  the  point  where  it  commences  to  be  depressed ;  these 
Bobin  has  designated  polar  globules. 


892  EMBBYOLOGY. 

2.  Formation  of  the  Blastoderm.— Soon  a  fluid  is  formed  at  the  centre 
of  the  ovulum,  in  the  midst  of  the  mass  of  vitelline  globules,  or  rather  the 
mass  of  young  cells  that  take  the  place  of  the  vitellus.  This  fluid  presses 
the  globules  outwards  against  the  inner  face  of  the  vitelline  membrane,  and 
the  pressure  increasing  as  it  augments,  these  become  flattened  like  the 
elements  of  pavement  epithelium,  until,  finally,  they  constitute  a  membrane 
lining  the  zona  pellucida.     This  is  the  blastoderm. 

The  blastodermic  vesicle  (as  it  has  been  termed)  does  not  rercain 
simjile,  but  soon  divides  into  two  layers :  an  external  and  internal  hlas- 
todermic  layer,  which  are  readily  recognisable,  as  the  elements  of  the  fii"st 
are  pale  or  slightly  granular,  Vvhile  the  cells  of  the  second  are  filled  with  fat 
granules,  and  consequently  are  less  distinct  and  darker  coloured. 

3,  Appearance  of  the  Embryo. — While  the  blastoderm  is  dividing  into 
layers,  there  is  observed  another  modification  taking  place  in  the  ovulum, 
from  which  results  the  first  lineaments  of  the  embryo.  As  soon  as  tho 
blastodermic  vesicle  is  formed,  a  small  round  thickening  takes  place  at  a 
point  of  its  surface,  due  to  a  multiplication  of  cells.  This  mass  destroys  the 
transparency  of  the  blastoderm,  and  is  designated  the  embryonic  spot  or 
area  germinativa. 

The  area  germinativa  is  the  centre  where  commences  the  separation  of 
the  blastoderm  into  external  or  internal  layers.  The  middle  layer,  which 
is  to  form  the  foetal  organs,  does  not  extend  beyond  this  area. 

By  a  proliferation  of  the  elements  of  the  external  and  middle  layers,  the 
area  germinativa  increases  in  surface  and  ttdckness;  it  becomes  dark, 
prominent,  and  buckler-shaped,  and  is  named  the  opaque  area  ;  this  is  soon 
transparent  in  its  centre — the  area  pellucida.  The  area  pellucida  becomes 
elongated  and  constricted  in  its  middle  to  form  the  embryonic  area ;  in  tho 
middle  of  this  appears  a  dark  line,  the  primitive  trace  ov  furroiv,  and  below  is 
perceived  a  round  cord — the  chorda  dorsalis — which  develops  the  spinal 
axis. 

The  inner  layer,  in  its  turn,  becomes  two  layers  at  the  point  cor- 
responding to  the  embryo,  and  this  gives  rise  to  the  middle  layer. 

In  fine,  towards  the  twelfth  day  after  fecundation,  the  ovum,  having 
arrived  in  the  uterus,  measures  from  o-feth  to  ^^th  of  an  inch  in  diameter, 
and  is  composed  of  four  shells  contained  one  within  the  other,  thrte  of 
which  are  complete,  viz :  1,  The  zona  pellucida ;  2,  The  external  layer  of 
the  blastoderm ;  3,  The  middle  layer ;  4,  The  internal  layer.  At  this 
time  the  first  membrane,  destined  to  become  the  chorion,  is  already  studded 
with  fine  villosities. 

Article  III. — Development  of  the  Blastodermic  Layers. 

By  ulterior  metamorphoses,  the  layers  of  the  blastoderm  give  rise  to  the 
annexes  of  the  foetus  and  its  various  organs.  Therefore  it  is  that  these 
layers  receive  other  names  than  those  which  designate  their  situation. 
Thus  the  external,  or  serous,  is  named  the  sensitive  lai/er,  because  it  forms  the 
skin  and  organs  of  sense ;  the  middle  is  the  vascular  or  germinative,  as  it 
contains  the  principal  vessels  of  the  embryo,  and  in  its  substance  are 
developed  the  organs  of  locomotion ;  lastly,  the  internal  layer  is  termed  the 
mucous  or  intestino  glandular,  in  consequence  of  its  constituting  the  mucous 
membranes,  and  its  chief  portion  forming  the  intestines  and  their  glands. 

Each  blastodermic  layer,  then,  in  becoming  developed,  furnishes  the 
intrafoetal  and  extrafcetal  parts.     We  will  study  this  development,  having 


THE  FCETUS. 


893 


the  extrafoetal  parts  particularly  in  view,  and  reserving  the  others  until  we 
cuiue  to  examiuL!  the  development  of  the  foetus. 

EXTERNAL  LAYER. 

a.  Intrafcetal  parts. — The  external  or  sensitive  layer  (serous  stratum- 
epiblast)  forms  several  parts  belonging  to  the  fcetus;  these  are:  1,  The 
epidermis  and  its  dependencies,  such  as  the  hair,  hoofs,  horns,  glands  of  the 
skin ;  2,  The  central  nervous  system  :  the  organs  of  the  senses,  such  as  the 
retina  and  the  labyrinth. 

h.  Extrafoetal  parts. — So  long  as  the  foetus  is  represented  by  a  kind  of 
shield  at  a  given  point  of  the  blastodermic  layers,  the  external  layer  is 
everywhere  continuous,  and  extends  to  the  inner  face  of  the  chorion  and  the 
surface  of  the  embryo  without  any  line  of  demarcation.  But  the  embryo 
soon  becomes  inflected  at  its  two  extremities;  the  external  layer  of  the 
blastoderm  is  depressed  so  as  to  give  rise  to  two  layers :  the  cephalic  hood, 
which  covers  the  cephalic  extremity,  and  the  caudal  hood,  which  envelops 
the  other  extremity  of  the  embryo. 

The  lateral  parts  of  the  foetus  also  become  inflected  towards  one  another, 
as  may  be  proved  by  a  transverse  section;  thus  closing-in,  laterally,  the 
thoraco-abdominal  cavity  of  the  young  creature  which,  during  this  move- 
ment, is  more  deeply  placed  in  the  serous  layer.  The  latter  soon  comes  into 
contact  with  itself,  above  the  back  of  the  embryo. 

A  short  pedicle,  the  superior  umbilicus,  unites  the  two  portions  of  the 
blastodermic  layer.  This  pedicle  is  not  long  before  it  becomes  obliterated, 
then  breaks,  when  the  foetus  is  found  to  be  inclosed  in  an  independent  sac, 
which  is  nothing  more  than  the  amnion. 

Ficr.  419. 


TRANSVERSE   SECTION   THROUGH   THE   EJIERTO  OF   THE   CHICK   AT   THE   CLOSE   OF   THE 
FIRST   DAY   OF   IXCCBATION ;   MAGNIFIED   ABOUT    100   DIAMETERS. 

cA,  Chorda  dorsalis;  h.  External  serous,  or  corneal  layer;  m,  Medullary  position  of 
serous  layer;  Pr,  Primitive  groove  between  the  dorsal  laminje,  r/  and  ?« ;  dd, 
Intestinal  epithelial,  or  glandular  layer  (mucous  layer);  wicp,  Prevertebral  mass, 
in  which  the  primary,  or  protovertebrse,  are  formed,  and  which  is  continuous 
with  the  middle  lamina,  sp:  tcich.  Fissure  in  the  middle  lamina,  presentinc;  the 
first  indication  of  the  pleuro-peritoneal  (thoraco-abdominal)  cavity,  and  of  the 
subsequent  division  of  the  middle  lamina  into  two  layers. 

The  sensitive  layer  is  therefore  resolved  into  two  sections :  an  internal, 
the  amnion  ;  and  an  external,  the  serous  vesicle  (false  amnion  of  Pander,  the 
serous  covering  of  Von  Baer),  which  is  applied  to  the  inner  face  of  the  zona 
pellucida,  and  concurs  in  forming  the  chorion. 


MIDDLE    LAYER. 


All  the  parts  to  which  the  middle  layer  gives  rise,  belong  to  the  organs 
of  the  foetus;  the  development  of  this  layer  will  be  more  appropriately 
studied  in  the  chapter  devoted  to  the  foetus. 


894 


EMBRYOLOGY. 


INTERNAL    LAYER. 

a.  Intrafoetal  parts. — The  mucous  layer  of  the  blastoderm  forms  the 
epithelium  of  tlie  intestines,  the  glands  annexed  to  them,  the  respiratory 
apparatus,  the  kidneys,  and  the  bladder.  These  organs  are  developed  at  the 
same  time  as  the  extra  foetal  portions,  and  will  be  referred  to  presently. 

6.  Extrafoetal  parts. — In  incurving  on  itself,  the  embryo  incloses  in  its 
cavity  a  portion  of  the  internal  blastodermic  layer.  The  union  between  the 
free  and  the  imprisoned  portions  is  extensive;  but  before  long  it  is  only 
represented  by  a  narrow  canal  that  occupies  the  inferior  umbilical  ring. 
Tlie  mucous  layer  is  then  divided  into  two  distinct  portions:  the  intestinal 
groove,  or  intrafoetal  portion ;  and  the  umbilical  vesicle  (vesicula  alba),  or 
extrafoetal  portion ;  they  communicate  by  the  omphalo-mesenteric  or  vitelline 
duct. 


Tier.  420. 


Fig.  421. 


PLAN  OF  EARLY  UTERINE   OVUM. 

Within  the  external  ring,  or  zona  pellucida, 
are  :  the  serous  lamina,  a  ;  the  yolk,  6 ;  and 
the  incipient  embryo,  c. 


DIAGRAM   OF   OVUM   AT   THE   FORMATION 
OF    THE    AMNION. 

a,  Chorion ;  b,  Yolk-sac ;  c,  Embrvo  ;  d  and  e. 
Folds  of  the  sei'ous  layer  rising  up  to  form 
the  amnion. 


The  umbilical  vesicle  is  filled  with  a  granular  fluid,  which  is  conveyed, 
for  the  nutrition  of  the  foetus,  by  the  omphalo-mesenteric  vessels.  When 
this  alimentary  reserve  is  nearly  expended,  the  allantois  appears. 

The  allantois  commences  by  a  small  enlargement,  which  is  thrown  out  by 
the  intestinal  furrow  on  the  inferior  abdominal  wall.  This  bud  becomes 
elongated,  and  gradually  enlarges  by  drawing  the  umbilical  vessels  to  its 
border :  appearing  as  a  small  vesicle  that  at  length  extends  through  the 
umbilicus,  and  spreads  itself  over  the  inner  face  of  the  chorion,  between  it 
and  the  amnion. 

This  new  organ  is  divided  into  two  sacs  by  a  neck — the  urachus — at 
the  umbilical  ring ;  the  internal  is  the  smallest  and  forms  the  bladder,  and 
the  external,  the  most  voluminous,  constitutes  the  allantois  proper. 


TEE  FCETUS. 


895 


CHAPTER  11. 
THE   FCETAL   ENVELOPES   OF   SOLIPEDS. 

We  have  seen,  in  the  preceding  chapter,  that  the  vitelline  membrane  lined  by 
the  serous  vesicle  forms  a  complete  shell  around  the  developing  ovum ;  and 
we  have  also  noted  that  the  layers  of  the  blastoderm,  in  becoming  meta- 
morphosed, constitute  three  membranous  sacs,  which  contain  the  foetus. 
These  varioiis  membranes  are  described  as  the  envelojjes  or  annexes  of  the 
foetus.  There  are  also  added  to  these  the  cord  of  vessels  and  the  capillary 
ramifications  which  establish  the  relations  that  exist  between  the  mother 
and  the  young  creature. 

The  annexes  of  the  foetus  comprise :  1,  A  membranous  envelope  exactly 
moulded  on  the  uterus,  and  known  as  the  chorion ;  2,  A  second  ovoid  sac 
included  in  the  first,  and  directly  containing  the  foetus  :  this  is  the  amnion  ; 
3,  The  allantois,  a  membrane  formed  of  two  layers  spread  over  the  inner 
surface  of  the  chorion  and  the  external  face  of  the  amnion,  as  well  as 
covering  the  parts  between  these  two  envelopes ;  4,  A  small  pyriform  bladder 
constituting  the  umhilical  vesicle ;  5,  The  placenta,  a  collection  of  vascular 
tufts  which  graft  the  young  creature  to  the  mother ;  6,  The  umbilical  cord, 
comjJosed  of  vessels  that  attach  the  foetus  to  the  envelopes  suiTOundiug  it, 
and  which  ramify  in  the  placental  tufts. 


1.  The  Chorion.     (Fig.  422.) 

The  outermost  envelope  of  the  ovum,  the  chorion  is  a  vast  membranous 
and  perfectly-closed  sac,  whose  shape  exactly  corresponds  to  that  of  the  uterus. 

•  Fig.  422. 


EXTERIOR    OF    THE    CHORIAL   SAC;    MARE. 

A,  Body  ;  B,  c,  Cornua. 


It  has  a  body  and  two  cornua.  The  latter,  when  inflated,  are  plicated  and 
bosselated  like  the  caecum,  and  are  always  unequal  in  volume  :  that  in  which 
the  foetus  is  developed  having  by  far  the  largest  dimensions. 

The  external  face  is  studded  with  small  red  tubercles,  formed  by  the 


896 


EMBRYOLOGY. 


placental  tufts.     It  adheres  to  the  internal  surface  of  the  uterus.     Between 
the  two  membranes  there  is  found  a  small  quantity  of  sanguinolent  fluid. 

The  internal  face,  lined  by  the  external  layer  of  the  allantois,  is  united 
in  the  closest  manner  to  that  membrane,  except  at  the  umbilical  cord,  where 
there  exists  a  kind  of  conical  infundibulum  occupied  by  the  umbilical 
vesicle. 

Structure. — The  chorion  is  a  delicate  fibrous  membrane,  traversed  by 

the  vascular  ramifications  of  the  placenta.     It  is  formed  by  the  vitelline 

membrane,  to  the  inner  face  of  which  the  serous  vesicle   is  applied.     It  is 

stated  that  the  zona  pellucida,  or  primitive  chorion,  as  it  is  called,  disappears 

when  the  serous  vesicle,  the  definitive  chorion,  becomes 

Fig.  423.  independent  of  the  amnion. 

I  The    chorion   is   destitute    of   vessels    until   the 

allantois  is  developed. 

2.  The  Amnion.     (Figs.  423,  424.) 

The  second  sac  enveloping  the  foetus,  the  amnion 
floats  freely  in  the  interior  of  the  chorion,  to  which 
it  is  only  united  at  one  point  through  the  medium  of 
the  umbilical  cord.  It  contains  the  young  creature, 
which  is  also  attached  to  its  inner  face  by  the  vessels 
of  the  cord.  It  is  oval  in  shape,  and  has  thin  trans- 
parent walls.  » 

Its  external  face  is  covered  by  the  inner  layer  of 
the  allantois,  to  which  it  adheres  slightly.  The 
internal  face  is  perfectly  smooth,  and  is  applied  more 

or  less  directly  to  the  skin  of  the  foetus.     It  exhales  a  fluid  in  which  the 

latter  floats—  the  liquor  amnii. 

Liquor  amnii. — Inclosed  withf  the  foetus  in  the 
cavity  of  the  amnion,  this  fluid  is  more  or  less  abun- 
dant, according  to  the  period  of  gestation  ;  its  relative 
quantity  being  always  less  as  the  foetus  is  advanced 
in  development.  At  an  early  period  it  is  somewhat 
milky  in  appearance,  but  later  it  assumes  a  citrine  or 
slightly  reddish  tint.  It  has  a  salt  taste,  and  con- 
tains 99  per  cent  of  water,  with  albumen  and  salts, 
the  principal  of  which  are  chloride  of  sodium  and  the 
sulphate  and  phosphate  of  lime. 


FECUNDATED  EGG,  SHOW- 
ING FORMATION  OF  AM- 
NION   AND    ALLANTOIS. 

a,  Umbilical  vesicle ;  6, 
Amniotic  cavity  ;  c,  Al- 
lantois. 


Fi^.  424. 


FECUNDATED  EGG  OF  FOWL 
WITH  ALLANTOIS  NEARLY 
COMPLETED. 

a,  Inner  lamina  of  am- 
niotic fold ;  b,  Outer 
lamina  of  the  same ;  c, 
Point  where  the  amnio 


3.  The  Allantois.     (Fig.  423.) 

The  allantois  is  a  membrane  that  covers  the  inner 

face  of  the  chorion,  and  is  folded  around  the  insertion 

of  the  umbilical  cord,  to  spread  itself  over  the  whole 

external  surface  of  the  amnion.     It  thus  transforms 

tic  folds  come  in  contact    the  chorial  sac  into  a  kind  of  serous  cavity,  in  which 

with  each  other ;    the   the  amnios  is  inclosed  as  a  viscus. 

The  inner,  or  amniotic  lamina,  is  attached  to  the 
amnios  "so  slightly  that  dissection,  and  especially 
insufflation,  easily  destroys  its  adhesion.     When  the 
second  of  these  measures  is  resorted  to,  in  order  to 
separate  the  two    membranes,  the  allantoid  sm-face  assumes  a  bosselated 


allantois  is  seen  pene- 
trating between  the 
inner  and  outer  lamina; 
of  the  amniotic  fold. 


THE  FCETUS.  897 

or  blistered  appearance,  due  to  the  numerous  cellular  bands  that  attach  it  to 
the  amnion.  These  bands  rupture  when  the  inflation  is  forced,  and  a  noise 
is  heard  analogous  to  that  produced  by  the  rumpling  of  parchment.  With  a 
little  care,  the  whole  of  this  portion  of  the  allantois,  whose  extent  equals 
that  of  the  amnion,  may  be  entirely  detached. 

'•  The  degree  of  adhesion  of  the  chorial  allantois  is  more  marked. 
Ordinary  dissection,  which  is  easy  along  the  first  divisions  of  the  cord,  is 
much  more  difficult  towards  the  chorion,  and  soon  becomes,  if  not  im- 
possible, at  least  very  arduous,  if  we  desire  to  se2)arate  it.  But  here,  again, 
inflation  demonstrates  the  existence  of  the  membrane,  and  its  continuity 
with  the  portion  so  easily  dissected  from  the  amnion.  If,  after  oi)ening  the 
allantoid  sac  by  cutting  through  the  chorion  and  the  lamina  lining  it,  a 
tube  is  introduced  between  the  two  membranes — which  is  readily  done  near 
a  large  vessel,  by  a  slight  inflation  the  air  enters  between  the  allantois  and 
chorion,  though  it  only  follows  the  ti-ack  of  vessels  of  a  certain  size,  to  the 
sides  of  which  there  is  but  little  adherence.  If  the  inflation  is  pushed,  the 
air,  following  the  smallest  vascular  ramifications,  renders  the  membrane 
more  apparent,  though  without  detaching  it  from  the  points  where  the 
vessels  have  almost  become  capillaries. 

"  If,  instead  of  injecting  the  air  towards  tha  ramifications,  it  is  directed  in 
the  opposite  direction,  it  will  soon  be  perceived  to  extend  towards  the 
allantoid  portion  of  the  umbilical  cord,  and  insinuate  itself  between  the 
amnion  and  the  allantois  covering  it :  an  evident  proof  of  the  continuity 
of  the  two  layers  which  have  been  separated  for  the  purpose  of  studying 
them,  but  which  are,  in  reality,  only  two  portions  of  the  same  membrane 
that  forms  a  complete  sac."  ^ 

The  cavity  of  this  sac  communicates  with  the  bladder  by  means  of  the 
urachis,  a  narrow  canal  contained  in  the  amniotic  portion  of  the  umbilical 
cord,  and  expanding  towards  the  origin  of  the  allantoid  part  (at  D,  Fig.  425), 
where  its  walls  are  continuous,  one  part  with  the  amniotic  layer  of  the 
membrane,  the  other  with  the  chorial  layer,  after  being  prolonged  as  a 
sheath  around  the  cord  (b).  This  arrangement  shows  the  true  character  of 
the  allantoid  cavity,  which  is  evidently  a  kind  of  urinary  reservoir,  a 
dependency  of  the  bladder,  whose  fundus  is  prolonged  to  the  umbilicus  to 
constitute  the  urachus.  The  latter  follows  the  umbilical  vessels  in  tlie 
amniotic  portion  of  the  cord,  and  soon  expands  in  forming  the  allantoid 
cavity. 

Structure. — The  allantois  arises  from  the  intestinal  furrow,  or  otherwise 
the  included  portion  of  the  internal  blastodermic  lamina.  It  comprises  a 
slightly  fibrous  framework,  and  an  epithelial  layer.  It  carries  the  umbilical 
vessels  to  its  surface,  from  the  umbilicus  to  the  chorion. 

Allantoic  Fluid. — This  cavity  contains  a  fluid  analogous  to  the  liquor 
amnii,  and  which  has  almost  the  same  physical  qualities.  Analysis 
demonstrates  that,  during  the  early  months  of  foetal  life,  this  fluid  contains 
a  somewhat  large  proportion  of  sugar ;  this  gradually  diminishes,  and  at  last 
disappears  altogether.  The  fluid  has  been  considered,  towards  the  termina- 
tion of  gestation,  as  the  mine  of  the  foetus. 

HippoMANES. — This  name  is  given  to  small  brown  masses,  more  or  less 
numerous — though  often  there  is  only  one — which  float  in  the  allantoid  fluid. 
"  These  bodies,  of  the  consistency  of  gluten,  and  elastic  like  it,  are  flattened, 
thinner  at  the  borders  than  towards  the  centre,  oval  or  irregularly  circulai', 
and  about  the  diameter  of  a  five-franc  piece.  It  is  difficult  to  explain  the 
'  F.  Lecoq.     '  Des  Annexes  du  Foetus,' 


898 


EMBRYOLOGY. 


presence  of  the  hippomanes  in  the  allantoic!  sac.  Nothing  in  its  appearance 
indicates  that  it  may  be  formed  at  the  expense  of  the  lic[uid  contained  in  this 
membrane.  Sometimes  pediculated  hippomanes  are  found,  and  these  may 
assist  in  explaining  the  formation  of  the  free  hippomanes.  Bourgelat  speaks 
in  his  '  Anatomic '  of  pediculated  hippomanes,  and  I  have  been  able  to  make 
the  following  observations,  through  having  met  with  a  large  number  on  a 
foetus : 


•i'T.  425. 


^iK^^r-"^^"^'^'^^ 


FCETUS   OF    THE    MARE    WITH    ITS    ENVELOPES. 

A,  Chorion ;  C,  Amnion  removed  from  the  allantoid  cavity,  and  opened  to  expose  the 
fcGtus;  D,  Infundibiiluni  of  the  urachus;  B,  Allantoid  portion  of  the  umbilical 
cord. — b.  Point  of  the  external  snrfece  of  the  chorion,  destitute  of  placental 
villi,  and  corresponding  to  the  part  where  the  three  pediculated  hippomanes  are 
attached. 

"  Besides  the  free  hippomanes  found  floating  in  the  allantoid  fluid,  there 
were  remarked,  on  the  outer  wall  of  the  sac,  a  great  number  of  small  tear- 
shaped  bodies  of  variable  size,  adhering  by  a  pedicle  which  was  more  or  less 
narrow  as  the  mass  was  more  developed.     Their  colour  was  the  same  as 


THE  FOETUS. 


899 


tliafc  of  the  principal  hippomancs,  and  if  pressed  between  the  fingers,  the 
brown  matter  coLtaiued  in  a  thin-wallcd  sac  escaped  by  the  pedicle,  and 
sjjread  itself  over  the  external  surface  of  the  chorion.  There  the  villosities 
of  the  placenta  were  absent  at  the  margin  of  the  opening,  which  was 
surrounded  by  a  whitish  areola  (Fig.  425,  h). 

"  Might  it  not  be  admitted,  from  this  disposition,  that  the  hippomanes  is 
developed  between  the  placenta  and  the  uterus,  and  is  carried  inward,  by 
pushing  before  it  the  chorion  and  layer  of  the  allantois  covering  it,  until, 
on  reaching  the  allantoid  cavity,  it  becomes  detached,  like  certain  fibrous  or 
cartilaginous  bodies  in  the  synovial  or  serous  cavities  ?" — F.  Lecoq. 


4.  The  Umbilical  Vesicle. 

The  umhilical  vesicle  is  a  small  fusiform  or  pyriform  poiich,  lodged  in  the 
infuudibulum  at  the  extremity  of  the  umbilical  cord.  Its  fundus  adheres  to 
the  chorion :  the  opposite  extremity  is  prolonged  to  a  variable  depth  in  the 
substance  of  the  cord,  and  is  even  continued,  in  the  very  young  foetus,  to  the 
abdominal  cavity,  by  a  narrow  canal  that  communicates  with  the  terminal 
portion  of  the  small  intestine. 

This  pouch  has  a  red  colour,  from  its  great  vascularity ;  its  walls 
receiving  a  special  artery  derived  from  the  anterior  mesenteric,  the 
corresponding  vein  passing  to  the  jwrtal  vein.  These  are  the  two  omphalo- 
mesenteric vessels. 

In  the  last  months  of  foetal  life,  the  umbilical  vesicle  is  always  more  or 
less  atrophied ;  its  cavity  has  disappeared,  and  it  is  no  more  than  a  thin 
reddish-brown  cord.  Its  vessels  also  become  atrophied  in  the  same  mannei-, 
and  nearly  always  nothing  is  found  but  the  artery  reduced  to  the  dimensions 
of  a  thread. 


5.  The  Placenta. 

In  Solipeds,  the  placenta  is  composed  of  a  multitude  of  small  tubercles, 
spread  uniformly  over  the  external 

surface  of  the  chorion,  which  they  ^'"'  ^-^• 

almost  completely  cover.  These 
small  tubercles  are  formed  by  an 
aggregation  of  extremely  vascular 
villi,  which  implant  themselves  in 
the  follicles  of  the  uterine  mucous 
membrane.  The  terminal  ramifi- 
cations of  the  vessels  of  the  cord 
constitute  the  vascular  ajiparatus  of 
these  villi  TFig.  426  '. 

Structure. — The  villosities  of 
the  placenta  are  composed  of  a 
small  quantity  of  delicate  nu- 
cleated   connective    tissue   (and    a 

basement  membrane),  covered  by  simple  epithelium ;  at  their  centre,  they 
present  the  capillary  ramifications  of  the  vessels  of  the  cord,  which  generally 
form  loops  that  return  towards  the  base  of  the  papilla  (Fig.  427). 

The  villous  tufts  jienctrate  the  maternal  uterine  mucous  membrane,  in 
such  a  manner  that  the  two  capillary  systems  of  mother  and  fcetus  are  only 
separated  by  the  very  thin  walls  of  the  vessels  and  the  epithelium  of  the 


PORTION  OF  THE  ULTIMATE  RAMIFICATIONS 
OF  THE  UMF,ILTCAL  VESSELS,  FORMING  THE 
FCETAL    VILLI    OF    THE    PLACliNTA. 


900 


EMBRYOLOGY. 


villi.  The  fusion  of  these  two  systems  has  never  been  observed,  and  all  the 
interchanges  between  the  female  and  its  young  take  place  through  the 
capillaries  by  osmotic  force  only. 


6.  The  Umbilical  Cord. 

The   cord   is  formed   by  the    vessels   which,  in  the  foetus,  carry  the 

blood  to  the  enveloijes,  and  chiefly  to  the 
placenta.  It  is  divided  into  two  portions : 
an  amniotic,  the  longest,  which  is  always 
twisted  on  itself  like  a  cord,  and  covered 
externally  by  the  amnion  that  is  prolonged 
on  its  surface,  to  be  continued  with  the 
skin  around  the  umbilicus  ;  the  other,  the 
allantoid  portion  (Fig.  425,  b),  much 
shorter  and  less  twisted,  is  enveloped  by  the 
sheath  that  continues  the  two  laminse  of 
the  allautois,  and  is  inserted  into  the  supe- 
rior wall  of  the  chorion,  between  the  two 
cornua. 

Three  vessels  compose  the  cord :  two 
arteries  and  a  vein ;  these  are  covered  by 
a  layer  of  embryonic  tissue,  the  gelatine  of 
Wharton,  which  makes  them  appear  much 
larger  than  they  really  are. 

The  Umbilical  Arteries  arise  from 
the  internal  iliac,  and  pass  along  the  sides 
of  the  bladder ;  escaping  by  the  umbilicus, 
they  arrive  at  the  terminal  extremity  of 
the  amniotic  portion  of  the  cord,  and 
giving  off  some  branches  to  the  amnion, 
they  are  continued  to  the  extremity  of  the 
allantoid  portion,  where  they  end  in  an 
expansion  of  placental  ramifications.  The 
amniotic  divisions  of  these  arteries  are 
few,  and  extremely  flexuous ;  they  are  in- 
cluded between  the  allantoid  layer  and  the 
amniotic  membrane,  within  which  they 
may  be  seen.  The  placental  or  chorial 
divisions,  infinitely  larger  and  more  numerous,  leave  the  end  of  the  cord, 
and  pass  in  every  direction  between  the  chorion  and  external  lamina  of  the 
allantois,  beneath  which  they  project.  By  their  anastomoses  they  form  a 
very  rich  network,  from  which  proceed  the  capillary  twigs  that  enter  tho 
villosities  of  the  placenta.  Observation  demonstrates  that  these  twigs  do 
not  communicate  with  the  maternal  vessels,  and  that  they  are  continued  by 
venous  radicles,  the  origin  of  the  following  vessel. 

The  Umbilical  Vein  commences  by  these  capillary  radicles  of  the 
placental  villosities,  which  unite  between  the  chorion  and  amnion  to  form  a 
network  of  more  voluminous  divisions  and  complexity  than  that  of  the 
arteries.  Two  principal  branches  are,  finally,  the  result  of  the  coalescing; 
and  these  soon  unite  into  a  single  trunk,  which  accompanies  the  two 
arteries  in  the  cord.  On  reaching  the  imibilicus,  this,  the  xmililical  vein, 
bends  forward  on  the  inner  face  of  the  abdominal  parietes,  where  it  is 


PORTION  OF  ONE  OF  THE  FCETAL  VILLI, 
ABOUT  TO  FORM  PART  OF  THE  PLA- 
CENTA,   HIGHLY   MAGNIFIED. 

a,  a.  Its  cellular  covering;  b,  b,  b,  Its 
looped  vessels ;  c,  c.  Its  basis  of  con- 
nective tissue. 


THE  FCETU8. 


901 


covered  by  the  peritoneum,  and  arrives  at  the  liver,  into  which  it  enters  and 
opens  directly  into  the  vena  portfe  ;  the  junction  of  the  two  vessels  giving 
rise  to  a  single  canal  from  which  proceed  the  hepatic  veins.  In  other 
animals  than  Solipeds,  this  vessel  gives  off  a  particular  trunk  of  somewhat 

Fig.  428. 


A   FCETUS  OPENED   ON   THE   LEFT  SIDE   TO  SHOW   THE   COURSE   OF   THE   UMBILICAL 
VESSELS   IN   THE   BODY. 

A,  Umbilical  cord ;  B,  Umbilical  vein  ;  c,  Umbilical  artery ;  D,  Bladder ;  E,  Testicle  5 
F,  Kidney ;  G,  Spleen  ;  H,  Liver  ;  i.  Intestine  ;  J,  Lung ;  K,  Heart ;  L,  Pulmonaiy 
artery ;  Ji,  Ductus  arteriosus  ;  N,  Thymus  gland. 

considerable  volume,  which   passes   directly   to   the    posterior  vena   cava, 
forming  what  is  named  the  ductus  venoms  (Figs.  429,  430). 

Such  are  the  umbilical  vessels,  and  it  will  be  seen  that  they  form  a  part 
of  the  circulatory  system  of  the  young  creature  which  will  be  more  com- 
pletely studied  hereafter. 


OrFFERENTLiL   CHAKACTEES  IN   THE   ANNEXES   OP   THE    FCETUS   OF   OTHER   THAN   SOLIPED 

ANIMALS. 

1.  KonvANTS. — Placenta. — The  placental  apparatus  of  the  Cow  is  not  uniformly 
spread  over  the  outer  surface  of  the  chorion,  but  is  constituted  by  a  variable  number  of 
vascular  bodies,  about  sixty  on  an  average,  disseminated  here  and  there,  and  dovetailed  by 
reciprocal  penetration  of  prominences  and  cavities,  into  analogous  bodies  on  the  inner 
surface  of  the  uterus,  designated  coti/ledons.  These  are  only  thickened  points  of  the 
mucous  membrane,  the  follicles  of  which  are  enormously  enlarged.  They  exist,  we  have 
seen,  before  gestation ;  but  observation  demonstrates  that  they  may  be  afterwards  formed 
or  entirely  renewed,  especially  in  those  cases  in  which  accidental  circumstances  have 
rendered  those  present  insutficient  for  their  office.  The  largest  are  found  in  tlie  body  of 
the  uterus;  in  the  conuia  they  are  smaller  as  they  are  nearer  the  extremity.  Their 
form  is  generally  elliptical,  and  they  are  attached  to  the  uterine  surface  by  a  wide  mucous 
60 


902 


EMBRYOLOGY. 

V\s.  429. 


BLOOD-VESSELS   IN   THE   LIVER   OF    AN   EQUINE    F(ETUS   AT   MID-TERM. 

A,  Umbilical  vein ;  B,  Its  anastomoses  with  the  portal  vein,  c ;  D,  Ductus  venosu.s 
E,  Posterior  vena  cava. 


Fis:.  430. 


j^^^l 

■ 

■ 

IP 

9 

m^M 

m 

^ 

■ 

^^m 

^ 

1 

H 

1 

^ 

n 

1 

LIVER   OF    A    LAMB    AT    BIRTH. 

A,  Posterior  vena  cava ;  b,  Vena  portse ;  c,   Umbilical  vein ;  D,  Anastomosis  of 
the  umbilical  vein  with  the  vena  portae. 


TEE  FCETUS.  903 

pedicle ;  their  surface  is  convex,  and  perforated  by  numerous  openings,  into  which  the 
placental  tufts  pass.  They  have  always  a  yellowish  colour  which,  added  to  their 
external  characteristics,  gives  them  the  appearance  of  a  moril  mushroom. 

With  regard  to  the  ■placentiv,  they  repeat,  on  the  surface  of  the  chorion,  the  disposition 
of  the  cotyledons  on  the  uterus.  They  aie  vascular,  concave  patches,  closely  embracinc 
the  cotyledons,  and  showing  on  tlieir  surface  a  multitude  of  long  ramifying  papilL-e, 
which  bury  themselves  in  the  cotyledonal  cavities.  They  are  attached  to  the  chorion  by 
a  very  thick,  short,  vascular  pedicle. 

In  the  Sheep  and  Goat  the  arrangement  is  the  same,  except  that  the  cotyledons  are 
hollowed  out  in  tlieir  centre,  like  a  cup,  and  into  this  cavity  the  placenta  is  inserted. 

-  Chorion. — This  membrane  corresponds  to  the  inner  face  of  the  uterus,  in  the  inter- 
placental  points ;  its  internal  surface  is  united  by  lamellar  connective  tissue  to  the 
amnion  and  allantois.     Its  general  form  is  a  repetition  of  that  of  the  uterine  cavity. 

Allantois. — Very  difterent  trom  that  of  the  Mare,  and  otherwise  much  less  com- 
plicated, the  allantois  of  Ruminants  is  a  very  elongated  cavity,  whoso  middle  portion 
receives  the  insertion  of  the  urachus,  and  whose  extremities  are  prolonged  into  the  two 
cornua  of  the  chorion.  This  sac,  which  is  an  expansion  of  the  urachus,  is  always 
reversed  on  one  of  the  sides  of  the  amnion.  At  times  the  hippomanes  is  found  floating 
in  the  liquid  it  contains. 

Amnion, — Altogether  like  that  of  Solipeds,  this  membrane  is  readily  resolved  into 
two  lamina,  and  presents  on  its  inner  surface  a  great  number  of  little,  yellowish-white, 
epidermic  patches,  more  especially  visible  on  the  amniotic  covering  of  the  cord. 

Umbilical  cord. — This  comprises  two  arteries  and  two  veins ;  the  latter  forming  one 
trunk  on  their  entering  the  abdomen.  To  reach  the  chorion,  these  vessels  only  traverse 
the  amniotic  cavity.  They  are  accompanied  by  the  urachus,  which  at  their  extremity 
presents  the  dilatation  that  results  in  the  allantoid  sac. 

Umbilical  vesicle. — This  pouch  disappears  at  an  early  period,  and  not  a  vestige  of  it 
is  to  be  found  after  the  formation  of  the  abdominal  parietes. 

2.  Pig. — The  placenta  is  formed  by  an  expansion  of  the  villous  tubercles,  as  in 
Solipeds. 

The  chorion  has  not  a  body  and  two  cornua,  but  is  merely  an  elingated  sac,  whose 
two  extremities  are  in  relation  with  the  adjacent  ftietuses.  The  inner  face  corresponds, 
as  in  Ruminants,  with  the  amnion  and  allantois.  The  latter  is  the  same  as  in  the  Cow, 
though  it  is  very  much  shorter. 

The  umbilical  vesicle,  amnion,  and  cord  are  also  the  same  as  in  Ruminants. 

3.  Carnivora. — The  placenta  is  a  thick  cincture,  surrounding  the  middle  portion  of 
the  chorion.     The  latter  resembles  that  of  the  Pig. 

The  allantois  is  disposed,  in  principle,  as  in  Solipeds. 

The  umbilical  vesicle,  which  remains  very  developed  at  all  periods  of  foetal  life, 
resembles  in  shape  the  allantois  of  the  Pig  :  being  a  transversely  elongated  sac  included 
between  the  amnion  and  the  inner  allantoid  lamina,  and  provided  at  its  middle  portion 
with  a  narrow  pedicle,  which  is  prolonged  into  the  umbilical  cord;  its  walls  are 
extremely  vascular. 

The  amnion  is  lined,  internally,  by  the  inner  lamina  of  the  allantois. 

The  umbilical  cord  has,  as  in  Solipeds,  an  allantoid  portion ;  but  it  is  extremely 
short,  and  enveloped  in  a  wide  fold  of  the  allantois. 

Results. — The  comparative  examination  of  the  disposition  of  the  placenta  may 
furnish  valuable  indications  as  to  the  procedure  to  be  adopted  in  practising  artificial 
delivery  ;  as  the  surgical  manojuvres  should  necessarily  vary  with  the  extent  and  disposi- 
tion of  the  points  of  union  existing  between  the  uterus  and  the  foetal  envelopes. 

With  this  practical  object  in  view,  we  believe  tiiat  it  is  useful  to  divide  the 
domesticated  animals  into  two  groups:  those  which  have  a  simple,  and  those  which 
have  a  multiple  placenta.  The  first  group  may  be  subdivided,  according  as  the  simple 
placenta  is  general  or  local. 

This  division  is  summed  up  in  the  following  table : 

'  Simple  Placenta      j  ^^^neral |  j.^^J^- 

Animals  '   Local  and  Circular    .  {  ^^f . 

I  Cow. 

,  Multiple  Placenta \  Sheep. 

Goat. 


901 


EMBRYOLOGY. 


COMPABISON  OP  THE  ANNEXES  OF  THE  HDMAN  FCETTS  WITH  THOSE  OP  ANIMALS. 
The  human  fcetus,  like  that  of  the  domesticated  mammals,  is  enveloped  by  an  amnion 
and  chorion,  which  are  generally  identical  in  disposition  with  those  already  described. 
The  umbilical  vesicle  submits  to  the  same  change  as  in  the  Mare,  becoming  so  quickly 
atrophied  that  scarcely  any  traces  of  it  can  be  found  at  birth.  It  is  impossible  to 
isolate  the  amnion  from  the  inner  face  of  the  chorion ;  so  that  some  anatomists  only 
admit  its  presence  by  analogy  with  what  is  observed  in  animals. 


Fig.  431. 


(jQsrnnsmrry 


DIAGRAM  OF  AN  EARLY  HUMAN  OVUM, 
SHOWING  THE  AMNION  IN  PROCESS  OF 
FORMATION,  AND  THE  ALLANTOIS  BEGIN- 
NING  TO   APPEAR. 

a,  Chorion  ;  b,  Vitelline  mass,  surrounded  by 
the  blastodermic  vesicle  ;  c,  Embryo  ;  d,  e,f, 
External  and  internal  folds  of  the  serous 
layer,  forming  the  amnion ;  g,  Incipient 
allantois. 


DIAGRAM  OF  A  HUMAN  OVUM  IN  SECOND 
MONTH,  SHOWING  THE  COMPLETION  OF 
THE  SAC  OF  THE  AMNION,  AND  A  FUR- 
THER  DEVELOPMENT   OF   THE  ALLANTOIS. 

al.  Smooth  portion  of  the  chorion ;  a2,  Its 
villous  portion;  k,  k,  Elongated  villi  col- 
lecting into  placenta ;  b,  Vitelline,  or  um- 
bilical vesicle  ;  c.  Embryo ;  /,  Amnion,  inner 
layer ;  h,  Its  outer  layer  coalescing  with 
the  chorion. 


The  umhilical  cord  offers  nothing  particular.  The  placenta  is  circular;  its  diameter 
at  the  termination  of  pregnancy  being  from  6  to  8  inches,  and  its  thickness  from  1  to  1^ 
inches.  There  is  distinguished  the  fa^tal  placenta,  in  the  midst  of  which  the  umbilical 
cord  arrives ;  and  the  maternal  placenta,  whose  villosities  dovetail  with  those  of  the 
former. 

The  insertion  of  the  placenta  takes  place  towards  the  fundus  of  the  uterus,  near  one 
of  the  Fallopian  tubes.  "When  there  are  more  than  one  fcetus,  there  are  a  corresponding 
number  of  placentae. 

Independently  of  those  annexes,  which  are  the  same  in  all,  there  is  described  for  the 
human  fcetus  a  special  envelope,  external  to  the  chorion  ;  this  is  the  membrana  decidua. 
This  is  formed  by  the  hypertrophied  mucous  membrane,  which  is  doubled  around  the 
ovum,  when  the  latter  is  lodged  in  the  uterine  cavity.  Consequently,  there  results  the 
division  of  the  decidua  into  two  parts  :  the  true  decidua  {decidua  vera)  which  covers  the 
uterus,  and  the  reflected  decidua  {decidua  reflexa)  which  envelops  the  chorion.  These 
present  the  characters  of  the  hypertrophied  uterine  mucous  membrane. 


CHAPTER  ni. 

DEVELOPMENT    OF    THE   FOETUS. 

In  the  two  preceding  chapters,  we  have  seen  how  the  fecundated  ovulum 
is  modified  to  furnish  the  earliest  lineaments  of  the  foetus  and  the  organs 
annexed  to  it ;  this  chapter  will  be  devoted  to  an  examination  of  the  manner 
in  which  the  fcetus  is  developed. 

The  young  creature  is  designated  an  embryo  during  the  early  period  of 
gestation,  before  it  has  assumed  any  definite  shape ;  but  as  soon  as  it  exhibits 
the  form  of  the  species  to  which  it  belongs,  it  is  named  a  foetus.  The 
transition  between  these  two  states,  though  they  have  different  names,  is 
altogether  inappreciable ;  so  that  we  content  ourselves  with  studying  the 
first  phases  of  development  under  the  heading  of  the  formation  of  the 
embryo,  and  the  last  under  that  of  the  development  of  the  organs. 

Article  I. — Formation  of  the  Embryo. 

When  the  embryo  has  assumed  the  foim  of  an  elongated  streak,  and 
shows  in  its  middle  the  primitive  groove,  there  appear  in  the  middle  lamina 
of  the  blastoderm  the  chorda  dorsalis,  the  vertebral  lamincB,  and  the  lateral 
lamince. 

DEVELOPMENT  OF  THE  CHORDA  DORSALIS  AITD  VERTEBRAL  LAMINA. 

The  chorda  dorsalis  is  a  cylindrical  cord,  slightly  attenuated  at 
both  extremities,  which  is  developed  beneath  the  primitive  groove.  On 
its  sides  is  a  series  of  small  opaque  quadrangular  masses — the  vertebral 
lamince — which  are  nothing  more  than  the  protovertebrce,  or  first  traces  of 
the  foetal  vertebr®.  Each  of  these  little  masses  is  soon  perforated  by  an 
opening,  and  is  then  divisible  i^to  three  portions  :  the  protovertebral  cavity, 
the  muscular  lamina,  situated  above  the  cavity,  and  the  protovertebrce,  placed 
below  it. 

The  muscular  lamince,  in  augmenting  in  volume,  are  inflected  upwards, 
and  unite  in  the  middle  line  of  the  back.  They  form,  in  great  part,  the 
muscles  of  the  vertebral  furrows ;  they  also  give  off,  below,  prolongations 
which  concur  in  the  development  of  the  intercostal  and  abdominal  muscles, 
as  well  as  those  of  the  extremities. 

The  protovertebrce  curve  upwards  and  downwards  in  such  a  fashion  as  to 
surround  the  protovertebral  cavity  or  medullary  canal,  and  the  dorsal  cord. 
The  superior  ring  is  the  rudiment  of  the  annular  portion  of  the  vertebrae, 
and  the  inferior  ring  and  dorsal  cord  constitute  the  vertebral  bodies  and 
the  discs  uniting  them. 

DEVELOPMENT  OF  THE  LATERAL  AND  CEPHALIC  LAMINiE, 

The  lateral  lamince  is  the  name  given  to  that  part  of  the  middle  lamina 
of  the  blastoderm  which  is  placed  to  the  right  and  left  of  the  vertebral  laminae. 
In  the  region  of  the  trunk,  these  laminae  are  separated  for  a  certain  period 


906 


EMBRYOLOGY. 


from  the  vertebral  laminas;    in  the  cephalic  region   they  always   remain 
adherent  to  them,  and  at  this  point  they  are  named  the  cephalic  lamince. 

1.  The  proper  lateral  laminae  are  divided  into  two  layers :  an  external  and 
an  internal,  united  by  the  middle  lamina,  and  including  between  them  a 
cavity  which  becomes  that  of  the  pleura  and  peritoneum — the  pleuro- 
peritoneal  cavity.  It  is  after  these  primary  modifications  that  the  lateral 
lamiuBB  are  fused  to  the  vertebral  laminae. 

The  internal  lamina,  also  named  the  fihro-intestinal  lamina,  envelops  the 
deep  portion  of  the  blastodermic  layer  or  intestinal  furrow,  the  umbilical 
vesicle,  and  the  allantois.  It  constitutes  the  fibrous  and  vascular  part  of 
these  membranes,  and  carries  the  vessels  to  the  inner  face  of  the  chorion. 

The  external  or  cutaneous  lamina  is  developed  in  two  directions.  Above, 
it  passes  between  the  muscular  laminae  and  the  foetal  portion  of  the  external 
layer  of  the  blastoderm,  to  form  the  skin  of  the  back.  Below,  it  separates  into 
two  other  laminae,  which  receive  between  them  the  prolongations  of  the 
muscular  laminae,  destined  to  the  formation  of  the  intercostal  and  abdominal 
muscles  and  the  ribs.  Of  these  two  secondary  laminae,  the  external  forms 
the  skin  of  the  trunk,  and  the  internal  the  parietal  layer  of  the  peritoneum. 

The  cutaneous  laminae  also  have  an  extra-fcetal  prolongation — the  fibrous 
layer  of  the  amnion. 

Fig.  433. 


THE   EAULV   STAGES   OF   THE   DEVELOPMENT   OF   THE   BODY   OF   A   FOWL. 

A,  The  first  rudiment  of  the  embryo ;  a,  Its  cephalic,  and  6,  its  caudal  end ;  c,  The 
primitive  groove. — B,  The  embryo  further  advanced;  a,  b,  c,  As  before;  d,  The 
dorsal  laminae  as  yet  developed  only  in  the  cephalic  region,  and  not  quite  united 
in  the  middle  line  ;  e,  The  protovertebra. — c,  The  letters  as  before.  The  dorsal 
laminae  have  united  throughout  the  greater  part  of  the  cephalic  region,  and  are 
beginning  to  unite  in  the  anterior  spinal  region. — D,  Embryo  further  advanced, 
the  dorsal  lamina;  having  united  throughout  nearly  their  whole  length ;  the 
protovertebrffi  have  increased  in  number,  and  the  omphalo-mesenteric  veins,  /, 
are  visible. 


With  regard  to  the  middle  or  mesenteric  lamincp,  they  are  confounded  in 
the  mesial  line,  and  in  their  texture  are  developed  the  Wolffian  bodies  and 
the  principal  vessels  of  the  trunk. 


THE  F(ETUS.  907 

2.  The  cephalic  lamince  always  remain  adherent  to  the  vertebral  laminaB, 
and  are  inflected  inwards  with  them  to  form  the  anterior  portion  of  the 
cephalo-intestinal  cavity.  The  latter  is  divided  into  two  parts  :  the  pharyn- 
geal and  the  oesophageal  cavities. 

The  pharyngeal  cavity  opens  externally  by  the  mouth ;  it  is  partially 
closed,  laterally,  by  the  i)liaryugeal  arches.  The  oesophageal  cavity  soon 
offers  a  diverticulum,  which  shortly  after  communicates  with  the  pleuro- 
peritoneal  cavity;  this  diverticulum  lodges  the  heart,  and  is  named  the 
cardiac  cavity. 

The  cephalic  laminae  also  form  the  derm  of  the  cranium,  and  the  fibrous 
layer  in  which  some  of  the  cranial  bones  are  developed. 

Article  II. — Development  of  the  various  Organs  of  the  Animal 

Economy. 

development  of  the  nervous  system. 

We  will  at  first  glance  at  the  development  of  the  nervous  centres — the 
hrain  and  spinal  cord  ;  then  their  peripheral  parts,  the  nerves. 

1.  Development  of  the  Brain. — We  have  seen  in  the  preceding 
article  how  the  primitive  gi-oove  appears,  and  afterwards  the  medullary 
cavity.  The  latter,  the  first  trace  of  the  nervous  centres,  offers  an  en- 
largement at  each  of  its  extremities  ;  the  posterior,  or  rhomhoidal  sinus,  gives 
off  the  nerves  of  the  sacro-lumbar  plexus ;  the  anterior  gives  rise  to  the 
brain. 

The  latter  enlargement  is  resolved  into  three  successive  dilatations — the 
cells  or  cerebral  vesicles — distinguished  as  anterior,  middle,  and  posterior. 
They  are  filled  with  fluid,  and  the  middle  slightly  surmounts  the  other  two, 
which  gives  the  three  together  a  triangular  shape. 

The  vesicles  increase  irregularly  in  volume  ;  their  walls  are  gradually 
developed,  and  form  the  nervous  tissue;  while  their  cavity  persists,  and 
becomes  the  ventricles  of  each  portion  of  the  encephalon.  Thus,  the 
anterior  vesicle  represents  the  cerebral  hemispheres,  the  thalami  optici,  and 
the  lateral  ventricles.  The  middle  vesicle  forms  the  cerebral  crui-a,  the 
corpora  quadi'igemina,  and  the  aqueduct  of  Sylvius  or  middle  ventricle. 
The  posterior  vesicle  gives  rise  to  the  medulla  oblongata,  pons  Varolii, 
and  the  fourth  ventricle. 

The  middle  vesicle  is  that  which,  at  first,  increases  most  rapidly  in 
volume  ;  it  soon,  however,  ceases,  to  allow  the  anterior  cell  to  become 
developed,  when  the  encephalon  assumes  its  ovoid  form,  with  a  predominance 
of  the  anterior  part. 

Towards  the  end  of  the  first  third  of  intra-uterine  life,  nearly  all  the 
parts  of  the  brain  are  distinct :  the  two  hemispheres  have  become  isolable 
by  the  development  of  the  septum  lucidum  ;  the  convolutions  appear  on  their 
surface ;  the  corpora  quadrigemina  and  cerebral  crura  are  distinctly  defined. 
It  is  not  until  a  little  later  that  the  cerebellum  is  distinguishable,  as  well 
as  the  pons  Varolii,  medulla  oblongata,  corpora  restiformia,  and  corpora 
pyramidalia. 

2.  Development  of  the  Spinal  Cord. — The  medullary  (spinal)  canal 
is  the  first  trace  of  the  spinal  cord ;  it  occupies  the  whole  length  of  the 
vertebral  column,  and  its  cavity  communicates,  in  front,  with  the  fourth 
ventricle.  When  the  spine  is  developed,  the  marrow  does  not  increase 
proportionately  in  quantity,  and  appears  to  ascend  in  the  vertebral  canal ; 


908 


EMBRYOLOGY. 


Fi5.  434. 


it  stops  about  the  middle  of  the  sacrum  in  the  equine  foetus,  but  ascends 
higher  in  the  other  species.  During  this  apparently  ascensional  movement 
is  developed  the  filum  terminale,  and  the  nerves  of  the  cauda  equina. 

The  walls  of  the  medullary  canal,  at  first  very  thin,  increase  in  thickness 
by  the  appearance  of  the  nervous  matter  of  the  cord.  Soon  they  divide 
into  two  layers  :  an  internal,  the  epithelium  of  the  central  canal ;  the  other 
external,  the  grey  substance  of  the  cord.  Gradually  the  canal  contracts,  and 
the  marrow  is  seen,  with  its  longitudinal  furrows. 

At  the  end  of  the  first  month,  the  iaferior  roots  are  in  existence,  as  well 
as  the  spinal  ganglia  ;  the  latter  are  developed  at  the  expense  of  the  proto- 
vertebrsB,  as  will  be  shown  presently.  The  superior  roots  are  formed  some 
time  afterwards. 

The  envelopes  of  the  cerebro-spinal  centres  are  furnished  by  the  proto- 
vertebral  laminaB ;  they  are  developed  after  the  sixth  week,  progressing  with 
the  growth  of  the  parts  they  are  destined  to  cover. 

3.  Development  of  the  Nerves. — 
The  development  of  the  nerves  is  some- 
what obscure.  The  motor  roots  seem  to 
arise  from  the  cord ;  but  the  spinal  gan- 
glia are  formed  separately  in  the  pro- 
tovertebrse,  and  perhaps  originate  the 
sensitive  roots.  The  nervous  ramifica- 
tions begin  by  elongated  ramifying  cells, 
which  become  fused  to  each  other  by  their 
extremities ;  the  nuclei  of  the  cells  lying 
at  the  periphery  becoming  the  nuclei  of 
the  white  substance  of  Schwann,  the 
proper  nervous  tissue  being  afterwards 
gradually  deposited  between  the  axis- 
cylinder  and  the  envelope. 

The  gi-eat  sympathetic  is  early  seen 
as  a  nodulated  cord.     It  is  probably  de- 
lamina  ;  df,  Intestinal  fibrous  lamina ,  yeloped  in  the  Same  manner  as  the  other 

dd.  Intestinal  glandular  lamina;   dr,    ^ ^^ 

Pi-imitive  intestinal  groove ;  h,  Corneal 
lamina;  mr,  Medullary  tube — spinal 
cord ;  m,  Muscular  lamina ;  p,  Pleuro- 
peritoneal  cavity;  af,  Fold  of  the 
amnion ;  ao,  Primitive  aorta ;  vc,  Vena 
cardinalis ;  un,  Wolffian  body ;  unj, 
Duct  of  the  Wolffian  body. 


TRANSVERSE  SECTION  OP  THE  EMBRYO  OF 
A  FOWL  AT  THE  BEGINNING  OF  THE 
THIRD  DAY  OF  INCUBATION  X  90-100. 

ch,  Chorda  dorsalis ;  wwh.  Position  of  a 
thinning,  or  cavity  in  the  protoverte- 
bral  mass,  dividing  it  into  an  anterior 
and   posterior    portion ;    hp,   Parietal 


DEVELOPMENT  OF  THE  OKaANS  OF  SENSE. 


The  principal  portion  of  the  organs  of 
sense  belong  to  the  deiDendencies  of  the 
nervous  system,  and  are  developed  with  it ; 
the  other  parts  belong  to  the  external  epithelial  lamina,  the  skin,  and  the 
germinative  lamina. 

1.  Visual  Apparatus. — From  the  anterior  cerebral  vesicle  are  given  off 
two  tubular  prolongations,  which  are  directed  forward,  and  terminate  by  the 
primitive  eye-vesicles,  traces  of  the  ocular  globes.  The  hollow  protrusions 
form  the  optic  nerves ;  the  vesicles  furnish  the  retina  and  choroid.  The 
crystalline  lens,  vitreous  humour,  cornea,  and  sclerotica  arise  from  the 
external  blastodermic  layer.  These  modifications  take  place  in  the  follow- 
ing manner : 

The  external  integument  of  the  foetus  passes  over  the  front  of  the 
primitive  eye-vesicles.  Here  it  shows  a  slight  depression  on  its  outer 
sm-face,  and  on  its  inner  face  a  cellular  protrusion  (Fig.  435,  1,  o),  which, 
becoming  developed,  surrounds  the  external  depression,  completely  closes  it, 


THE  FCETUS. 


909 


Fig.  435. 


'it 


and  constitutes  the  commencement  of  the  crystalline  lens  (Fig.  435,  2,  /). 
The  latter,  thus  formed,  presses  on  the  primitive  eye-vesicle,  pushes  it 
backwards  (2),  and  gives  rise  to  a  secondary  eye-vesicle,  whose  anterior  wall 
becomes  the  retina,  and  the  posterior  wall  the  choroid.  The  lens  is, 
therefore,  a  dependency  of  the 
epithelial  lamina  ;  the  cells  com- 
posing it  become  elongated  into 
fibres  in  the  centre,  and  are  dis- 
posed at  its  circumference  as  a 
primary  amorphous  envelope — 
the  crystalline  capsule — and  after- 
wards as  a  secondary  envelope 
rich  in  vessels. 

The  portion  of  the  integu- 
ment which  is  not  doubled  to 
form  the  lens  envelops  the 
globe,  and  gives  rise  to  the 
sclerotica  and  cornea ;  the  epi- 
dermis furnishes  the  epithelium 
of  the  lattef,  which  becomes 
distinct  from  the  sclerotica  in 
the  coui'se  of  the  fourth  month. 

An  aperture — the  sclerotic 
cleft — is  made  at  the  lower  part 
of  the  fibrous  envelope  of  the 
eye ;  this  is  connected  with  the 
development  of  the  vitreous  body  : 
a  prolongation  of  the  derm — a 
kind  of  conjunctival  bud  passing 
through  this  opening,  and  placing 
itself  between  the  crystalline  lens  and  the  anterior  wall  of  the  secondary 
eye-vesicle  (3,  gl),  where  it  is  developed  and  transformed  into  the  vitreous 
body.  At  first  it  is  encircled  by  vessels  like  the  lens,  but  these  disappear 
before  the  termination  of  gestation. 

The  optic  nerve  is  developed  in  the  pedicle  uniting  the  eye-vesicle  to  the 
anterior  cerebral  vesicle.  The  retina  is  formed  by  the  inner  lamina  of  the 
secondary  eye-vesicle;  it  extends  to  the  leus  in  changing  its  character 
anteriorly.  According  to  Eemak,  the  choroid  is  constituted  by  the  posterior 
lamina  of  the  eye-vesicle ;  it  advances  at  first  to  the  lens,  and  then  becomes 
inflected  in  front  to  form  the  iris.  The  borders  of  the  pupil  are  attached 
to  the  vascular  envelope  of  the  lens,  and  this  gives  rise  to  the  pupillary 
diaphragm,  which  disappears  before  birth. 

The  motor  and  protective  organs  of  the  eye  are  gradually  developed 
around  the  globe.  The  eyelids  are  small  cutaneous  folds  that  appear 
towards  the  first  third  of  uterine  life ;  they  increase,  and  unite  at  their 
margin  until  irmnediately  before,  or  soon  after  birth,  when  they  separate. 

The  lachrymal  gland  is  a  dependency  of  the  epithelial  lamina  which  is 
pushed  in  above  the  globe.  At  first  solid,  it  gradually  becomes  channeled 
out  by  cavities,  from  which  arise  the  excretory  ducts. 

2.  Auditory  Apparatus. — The  internal  ear,  auditory  nerve,  and  middle 
ear,  are  developed  separately.  The  labyrinth  appears  in  the  shape  of  a 
vesicle,  which  is  not  in  direct  relation  with  the  posterior  cerebral  cell ;  it  is 
constituted  by  a  depression  of  the  epidermic  lamina,  the  auditory  fossa,  which 


\ 


LOXGITUDINAL  SECTION   OF   THE   EYE   OF   EMBRYO 
FOWL. 

1,  From  an  embryo  at  about  the  65th  hour  of  incu- 
bation ;  2,  From  an  embryo  a  few  hours  older ; 
3,  From  an  embryo  at  the  4th  day  of  incubation. 
— h,  Corneal  lamina ;  I,  Lens  in  Fig.  1,  still  con- 
nected with  the  corneal  lamina,  and  possessing 
a  small  cavity,  o,  in  its  interior  (in  Figs.  2  and 
3  it  is  seen  detached,  but  still  hollow) ;  r,  Intro- 
verted portion  of  the  primitive  optic  vesicle,  sub- 
sequently becoming  tlie  i-etina ;  a,  Posterior  part 
of  the  optic  vesicle,  which,  according  to  Remak, 
probably  becomes  the  choroid  coat,  ciliary  pro- 
cesses, and  iris,  and  in  Figs,  1  and  2  is  still  con- 
nected with  the  brain  by  the  hollow  optic  nerve ; 
X,  Thickening  of  the  corneal  lamina  ai-ound  the 
spot  from  which  the  lens  has  detached  itself; 
gl,  Vitreous  body,  or  humour. 


910 


EMBRYOLOGY. 


Fi2.  436. 


is  gradually  developed,  and  at  last  become  a  closed  cavity.  At  this  time, 
the  wall  of  the  labyrinth  is  only  a  simple  epithelial  membrane  ;  this  is  soon 
covered,  outwardly,  by  a  vascular  connective  membrane  that  separates  into 
three  layers :  an  internal,  joined  to  the  epithelium  to  form  the  membranous 
labyrinth  ;  an  external,  that  lines  the  cartilaginous  labyrinth ;  and  a 
middle,  whose  soft,  embryonic,  connective  tissue  disappears,  and  is  replaced 
by  the  perilymph.  At  the  same  time  that  these  changes  of  structure  are 
occurring,  the  vesicular  form  of  the  labyrinth  is  modified,  and  shows  the 
cochlea,  semicircular  canals,  ulriculus,  and  sacculus. 

The  middle  and  external  ear  arise  from  the  first  pharyngeal  (branchial) 
cleft,  which  is  never  completely  closed,  while  the  others  disappear.  At 
first,  then,  we  find  a  cavity  communicating  externally  with  the  pharynx ; 

this  cavity  contracts,  and  is  separated  into 
two  portions  by  a  partition  that  spreads 
across  its  middle,  and  which  becomes  the 
memhrana  ti/mpani ;  the  internal  portion  is 
the  middle  ear  and  Eustachian  tube;  the 
external  portion  is  the  external  auditory 
canal. 

The  ossicula  auditus  appear  in  a  cartila- 
ginous state  towards  the  third  month  ;  they 
gradually  ossify,  and  have  scai-cely  acquired 
their  definitive  volume  at  birth.  The  ex- 
ternal ear  (concha)  is  developed  above  the 
integument  after  the  second  month, 

3.  Olfactokt  Apparatus. — This  com- 
mences by  two  depressions  of  the  epidermic 
lamina,  analogous  to  the  auditory  fossa  and 
that  of  the  lens.  These  two  olfactory  fossas 
appear  below  the  ocular  vesicles,  and  become 
more  and  more  distinct,  being  margined  by 
small  projections  which  increase  their  depth. 
Behind,  they  communicate  with  the  pharynx. 
The  appearance  of  the  palate  separates  them 
in  front  from  the  buccal  cavity,  and  from 
this  period  the  nasal  fossae  are  constituted. 
They  are  completed  by  the  development  of  the  bones  of  the  face. 

The  olfactory  hulhs  and  nerves  are  primarily  hollow,  and  joined  to  the 
anterior  cerebral  cell.  The  nostrils  are  formed,  in  the  young  foetus,  by  a 
mass  of  mucus  and  epithelium ;  towards  the  middle  of  gestation  they  are 
open. 

4.  Gustatory  Apparatus.  —  ;S^ee,  subsequently,  the  development  of  the 
tongue  in  digestive  apparatus. 

5.  Tactile  Apparatus. — The  skin  and  its  dependencies. — The  skin  is 
developed  at  the  expense  of  the  epidermic  lamina  of  the  middle  layer  of 
the  blastoderm.  The  cutaneous  laminae,  by  the  modification  of  their  ele- 
ments, form  the  derma,  in  which  the  blood-vessels  are  very  apparent  at  the 
third  month.  In  the  epidermis,  the  mucous  and  the  horny  layers  are  soon 
distinguished  ;  in  the  first,  the  pigment  is  visible  at  the  commencement  of 
the  fifth  month  in  the  larger  quadrupeds.  When  the  foetus  increases  in 
volume,  the  epidermis  exfoliates  and  its  debris  floats  in  the  liquor  amnii. 

In  the  third  month,  the  hairs  are  seen  in  the  foetus  of  the  Mare  and  Cow ; 
they  appear  at  first  on  the  eyebrows,  lips,  and  the  joints  of  the  limbs  ;  at 


AN  EMBRYO  (human)  OF  FOUR 
WEEKS,  ENLARGED  ABOUT  THREE 
TIMES. 

a,  Vesicle  of"  corpora  quadrigemina ; 

b,  Vesicle  of  cerebral  hemispheres  ; 

c,  Vesicle  of  third  ventricle ,  (/, 
Vesicle  for  cei-ebellum  and  medulla 
oblongata  j  e,  Auditory  vesicle ;  /, 
Olfactory  fossa;  h,  Liver;  *  *, 
Caudal  extremity. 


THE  FCETVS.  911 

the  sixth  or  seventh  month  they  cover  the  body.  They  may  be  shed  aud 
renewed  before  birth.  They  are  developed  in  a  prolongation  of  the  epi- 
dermic lamina,  which  is  imbedded  in  the  substance  of  the  derm  ;  it  is 
shaped  like  a  little  bottle,  aud  is  composed  of  a  mass  of  cells  ;  in  its  centre 
these  cells  are  modified  and  collected  together  to  form  a  small  cone,  whose 
base  covers  the  growing  papilla.  This  cone  becomes  elongated,  touches  the 
surface  of  the  epidermis,  doubles  imder  the  effort  to  push  through  it,  and 
finally  makes  its  exit,  after  which  it  can  gi-ow  freely. 

The  sebaceous  and  sudoriparous  glands  are  developed  in  the  same  manner 
towards  the  middle  period  of  uterine  existence. 

"The  horny  productions— the  claws,  hoofs,  ergots,  clesniits—hegin  to 
show  themselves  early.  Towards  the  end  of  the  second  month,  in  the 
foetus  of  the  Cow,  there  is  perceived,  at  the  extremity  of  each  limb,  a 
small,  pale,  translucid,  conical  tubercle,  which  is  the  rudiment  of  the  hoof. 
At  the  commencement  of  the  fourth  month,  or  thereabouts,  the  hoof,  better 
defined,  has  become  firm  and  opaque,  and  has  assumed  a  fine  yellow  tint.  At 
mid-term,  brown  or  black  patches  are  manifest  if  the  coronet  is  provided 
with  pigment ;  it  is  only  about  the  end  of  gestation  that  the  hoof  towards 
the  coronet  begins  to  have  the  greenish  hue  peculiar  to  horn  destitute  of 
pigment,  but  the  remainder  of  this  production,  especially  at  the  inferior 
part,  preserves  its  yellow  colour  until  birth.  In  Solipeds,  the  "  chesnuts  " 
are  shown  at  mid-term  in  the  shape  of  thin  brown  plates,  which  are  soon* 
darker-coloured."  ^ 

The  horn  of  the  hoof  is  not  at  first  tubular ;  after  birth  it  is  shed  and  is 
succeeded  by  a  more  consistent  tubular  horn,  which  had  been  forming 
beneath  it. 


DEVELOPMENT  OF  THE  LOCOMOTOEY  APPARATUS. 

1.  The  Skeleton. — We  have  seen  at  page  16  how  the  development  and 
growth  of  the  bones  takes  place  ;  it  is  therefore  needless  to  recur  to  this 
subject  here ,  so  we  will  limit  oiu^elves  to  an  examination  of  the  mode  of 
development  of  the  principal  sections  of  the  skeleton. 

A.  Development  of  the  Vektebral  Column. — The  vertebral  column  is 
the  first  portion  of  the  skeleton  manifested  in  the  embryo ;  it  is  represented 
by  the  chorda  dorsalis,  a  stalk  constituted  by  a  mass  of  cells  situated  in  the 
interior  of  a  transparent  sheath.  The  protovertebrce  appear  on  each  side  of 
the  chorda  dorsalis ;  in  becoming  developed,  these  parts  encircle  the  latter 
and  the  medullary  canal ;  from  this  results  the  external  fheca  of  the  cord,  and 
the  superior  uniting  membrane.  From  this  time  the  vertebral  column  exists  in 
the  shape  of  a  membranous  axis. 

Soon  this  membranous  spine  is  segmented  to  give  rise  to  the  vertebraB, 
and  its  various  portions  gradually  become  cartilaginous.  Each  persistent 
vertebra  does  not  exactly  correspond  to  a  protovertebra ;  in  reality,  the 
latter  takes  a  share  in  the  formation  of  two  vertebrae,  and  divides  into  two 
portions :  an  inferior,  which  constitutes  the  posterior  moiety  of  a  permanent 
vertebra ;  and  a  superior,  which  forms  the  anterior  moiety  of  the  persistent 
vertebra  immediately  behind  the  preceding  and  the  intervertebral  disc. 

The  bodies  of  the  vertebrje  are  developed  more  rapidly  than  their  spinal 
portion :  thus,  towards  the  end  of  the  second  month,  all  the  vertebral  bodies 
are  already  cartilaginous,  wbile  the  vertebral  laminae  are  yet  membranous. 

'  Colin.    '  Traite  de  Physiologie  Compare'e  des  Animaiix.'     2n(l  Edition,  Paris,  1873- 


912 


EMBRYOLOGY. 


It  is  only  in  tlie  third  montli  that  ossification  begins  in  the  vertebral 
column.  The  number  of  osseous  nuclei,  primary  and  complementary,  is 
not  the  same  in  all  species ;  they  have  been  enumerated  at  page  20.  In 
a  large  number,  the  spinous  process  is  regarded  as  the  result  of  the  joining 
together  of  the  two  moieties  of  the  vertebral  arch ;  in  the  Sheep,  on  the 
contrary,  the  spinous  process  forms  a  nucleus  altogether  independent  of  the 
vertebral  arches.     Thomas  has  noted  this  disposition,  and  he  considers  it 


Fig.  437. 


Fiff.  438. 


DIAGRAM  SHOWING  THE  POSITION  OP  THE 
CHORDA  DORSALIS  IN  THE  BODY  OF  THE 
VERTEBRA,  AND  THE  FORMATION  OF  THE 
NEURAL   ARCHES. 

ch,  Chorda  dorsalis ;  cv,  Body  of  the  verte- 
bra ;  a,  Neural  arch,  or  neurapophysis  j 
c,  Rib ;  pr.  Transverse  process. 


DIAGRAM  SHOWING  THE  ATTENUATION  OF 
THE  CHORDA  DORSALIS  IN  THE  MIDDLE  OF 
THE  BODIES  OP  THE  VERTEBRA,  WHILST 
PRESERVING  ITS  ORIGINAL  DIAMETER  IN 
THE   INTERVERTEBRAL  SPACES. 

ch,  Chorda  dorsalis;  v.  Body  of  vertebra; 
li,  Intervertebral  spaces. 

as  peculiar  to  animals  whose  anterior  dorsal  vertebrae  are  furnished  with  a 
long  spinous  process. 

During  ossification,  the  chorda  dorsalis  disappears,  except  between  the 
vertebra,  where  it  is  developed  to  form  the  intervertebral  substance  or 
discs. 

B.  Development  of  the  Cranium  and  Face. — The  encephalon  is  en- 
veloped by  a  membrane  formed  at  the  expense  of  the  protovertebral  laminae. 
This  cranial  membrane  becomes  partly  cartilaginous,  partly  fibrous;  the 
cartilage  exists  at  the  base  of  the  cranium,  and  seems  to  prolong  the  bodies 
of  the  vertebrfe  into  this  region  ;  indeed  it  is  known  that  the  skull  may  be 
resolved  into  four  portions,  each  corresponding  to  a  vertebra.  The  cartilage 
is  insensibly  transformed  into  bone ;  while  the  fibrous  part,  composing  the 
roof  of  the  skull  and  its  lateral  walls,  passes  directly  into  an  osseous  state. 

The  bones  of  the  face  are  developed  at  the  expense  of  the  pharyngeal 
arches.  This  designation  is  given  to  four  laminae  (or  lamellae)  which  spring 
fi'om  the  anterior  extremity  of  the  chorda  dorsalis,  and  double  downward  and 
inward  to  join  those  of  the  opposite  side.  They  are  also  named  the  branchial 
and  visceral  arches,  and  the  spaces  between  them  are  called  the  pharyngeal 
clefts.  The  upper  jaw,  mouth,  nasal  cavities  :  i.e.  the  nasal,  maxillary,  and 
palate  bones,  are  furnished  by  the  first  arch.  Meckel's  cartilage,  which  arises 
from  the  handle  of  the  malleus  to  pass  towards  the  inferior  maxilla,  is  also  a 
dependency  of  this  branchial  arch  ;  it  disappears  towards  the  sixth  or  seventh 
month,  it  is  to  be  remarked  that,  at  the  commencement,  the  mouth  com- 
municateis  with  the  nasal  cavities ;  the  palate  is  developed  in  two  moieties 


TEE  FGETU8. 


913 


which  advance  towards  each  other,  though  they  remain  a  long  time  apart ; 

so  that  at  this  time  the  young  animal  really  has  a  hare-lip.     The  second 

jiharyngeal  arch  forms  the  stapes,  the  pyramidal  process  of  the  temporal 

bone,    styloid     arch,     and 

branch  of  the  hyoid.     The  Fig-  439. 

tliird   develops   the   hyoid 

with  its  cornua ;  while  the 

fourth  arch  only  constitutes 

the  soft  parts  of  the  neck. 

C.  Development  of  the 
Thorax. — The  ribs  are  de- 
pendencies of  the  proto- 
vertebral  laminas,  which 
ciu've  towards  the  lower 
face  of  the  vertebral  column. 
The  true  ribs  are  most 
rapidly  developed,  and 
before  attaining  the  middle 
line  are  united  by  their 
internal  extremity,  and 
form  a  moiety  of  the  ster- 
nimi.  A  fissure  separates 
the  costal  arches  of  the 
right  side  from  those  of 
the  left ;  this  gradually 
contracts,  and  finally  dis- 
appears, and  the  sternum 
is  then  formed.     The  ribs 

are,  after  the  petrous  bone,  the  parts  of  the  skeleton  which  are  most 
promptly  ossified,  ossification  commencing  in  the  middle  ribs. 

The  costal  arches  do  not  belong  exclusively  to  the  dorsal  vertebrte,  but 
have  a  tendency  to  form  along  the  whole  length  of  the  spine ;  and  it  is  not 
rare  to  see,  attached  to  the  lumbar  vertebrje,  a  small  cartilaginous  nucleus 
which  is  soon  lost  in  the  texture  of  the  abdominal  walls.  This  nucleus 
assumes  large  dimensions  on  the  last  cervical  vertebrfe  of  birds. 

The  form  of  the  thorax  varies  with  the  species ;  in  some  it  is  circular, 
in  others  it  is  flattened  laterally ;  and  in  all  cases  it  is  less  developed  in  the 
foetus  and  young  animal  than  in  the  adult.  It  is  in  the  latter  that  the 
thoracic  cavity  presents,  proportionately,  its  greatest  dimensions. 

D.  Development  of  the  Limbs. — The  limbs  do  not  show  themselves 
until  after  the  formation  of  the  spinal  coliunn,  the  pharyngeal  arches,  and 
the  thoracic  parietes.  They  appear  as  four  little  prolongations  from  the 
thorax  and  pelvis,  and  are  slightly  enlarged  at  their  origin  and  constricted 
in  the  middle.  Their  free  extremity  is  flattened,  and  either  divides  or 
remains  single,  as  the  animal  has  one  or  more  apparent  digits.  It  is  in 
these  prolongations  that  the  cartilaginous  rays  are  developed,  which,  at  a 
later  period,  become  the  bones  of  the  limbs.  For  the  manner  in  which  ossi- 
fication is  carried  on  in  each  bone,  reference  must  be  made  to  Ai'ticles  IV. 
and  v.,  pages  71  and  91. 

2.  Muscles. — The  muscles  are  developed  around  the  bones  when  these 
have  become  perfectly  distinct.  They  may  be  divided  into  four  groups  :  the 
vertebral  muscles,  which  come  from  the  muscular  laminae  of  the  protovertebrfe ; 
the  visceral  muscles — thoracic  and  abdominal  cavities,  neck  and  jaw — having 


the  head  of  a  fcetal  lamb  dissected  to  show 
Meckel's  cartilage. 
MOT,  The  malleus ;    i,  Incus ;  zy,  The  tympanic  ;    H,  The 
hyoid ;  sq,  The  squamosal ;  Pt,  Pterygoid  ;  pi,  Palatine  ; 
l,    Lachrymal ;  pmx,    Premaxilla ;   N,    Nasal    sac ;    em, 
Eustachian  tube. 


914 


EMBRYOLOGY. 


the  same  origin ;  the  cutaneous  muscles,  which  are  developed  at  the  expense 
of  the  cutaneous  laminae  of  the  middle  layer  of  the  blastoderm ;  and  the 
muscles  of  the  limbs,  whose  development  is  not  yet  perfectly  known. 

It  was  at  one  time  believed  that  the  muscular  iibres  were  formed  by  the 
junction,  end  to  end,  of  several  elongated  cells ;  but  it  is  now  known  that 
they  are  constituted  by  a  single  cell  which  lengthens,  and  whose  nuclei 
multiply  and  lie  at  the  sm-face,  while  its  contents  are  transformed  into  a 
substance  which  oifers  the  characteristics  of  contractile  tissue.     The  sar- 

colemma  is  formed  after  the  fibre, 
Fig.  440.  by    a    modification   of    the    con- 

^^  nective  tissue  surrounding  it. 

DEVELOPMENT    OF    THE  CIECULATORY 
APPARATUS. 

During  the  first  days  which 
follow  the  appearance  of  the  em- 
bryo in  the  substance  of  the  blas- 
todermic layer,  there  is  no  trace 
of  vessels  in  the  area  germinativa. 
It  is  not  long,  however,  before  the 
heart  and  some  blood-vessels  are 
seen  in  the  middle  layer,  the 
vessels  extending  to  the  sui-face 
of  the  mnbilical  vesicle,  which 
gradually  shows  itself.  While 
the  contents  of  the  vitelline  vesicle 
are  being  absorbed  by  the  embryo, 
the  heart  is  being  completed,  the 
vessels  are  developing,  the  allan- 
tois  is  formed,  and  the  placental 
circulation,  which  continues  until 
birth,  is  established.  From  this 
time  the  circulatory  apparatus  has 
acquired  its  definitive  disposition. 

1.  Appearance  of  the  Heart. 

diagram  of  the  formation  of  the  ven.e  „  -fj 

OMPHALO-MESENTERIC^   AND   UMBILICALES.  —CIRCULATION    IN    THE    UMBILICAL 

1,  At  the  time  of  the  first  appearance  of  the  um-  VeSICLE.—  The  pleuro-peritoneal 
bilicales,  and  the  commencement  of  the  cm-  cavity  of  the  embryo  presents, 
phalo-mesentericae ;  2,  At  the  time  of  the  first  anteriorly,  a  diverticulum,  the  car- 
appearance  of  the  branches  to  and  from  the  ^^^^  cavity,  in  the  interior  of  which 
liver,    and    the    diminution   of   the    omphalo-     j^       ^  .       developed.        This 

mesenteric  vessels ;  3,  4,  At  the  period  of  com-    "   ^        ^  f 

plete  foetal  circulation  in  1,  Omphalo-mesenteric  organ  appears  at  first  aS  a  small 
trunk  ;  in  2,  3,  Remains  of  it ;  in  4,  Vein  of  the  masS  of  cells,  the  innermost  of 
yolk  sac  alone ;  om',  Right,  and  om",  Left  vena  ^.jiicfi  become  separated  from  each 

omphalo-mesenterica; :    u.    Trunk   of  the    um-  .-i     „  .^    „„„„4.^  „  ^^^u^  r,r.A    r.r>n 

,  ...^  ,      .        I   D-  w       J    /»  I  i-i  other  to  create  a  cavity  and  con- 

bilical  vein ;   u ,  Right,  and  u  ,  Left  vena  ur»-  .            i     i  i       ^     ^   ^     t           a 

bilicalis;  dc,    Ductus   Cuvieri ;  i,  Jugularis;  c,  Stltute  the  blood- globules.    As  SOOn 

Cardinalis ;   I,  Liver ;  ha,  hepatica  advehentes ;  as  it    shows    itself,  the   heart   con- 

hr,  Hepatica;   revehentes ;  m,  Mesenteries ;  da,  tracts   and   dilates  alternately,  the 

Ductus  venosus  Arantii ;   ci,  Cava  inferior;  p,  movements  being  very  slow,  though 

vena  portse :    I,    Lienalis;   m,  Mesenterica  su-  ,,                  i      n        i                        •  i  „„ 

joj.*^        '    '               '     '  they   gradually    become    quicker. 

Towards    the    twelfth    day,    the 
central  organ  of  the  circulation  has  the  form  of  a  contractile  cylindrical  tube. 


THE  F(ETUS. 


915 


From  its  anterior  part  spring  two  branches,  the  aortic  arches  (arciis  aortce), 
which  are  directed  towards  the  head  of  the  embryo,  and  are  afterwards  in- 
flected downwards  and  backwards.  They  join  together  to  constitute  the  single 
aorta,  which,  in  its  turn,  divides  into  two  trunks,  the  arterio}  vertebralis  or 
primitive  aortce.  These  vessels  pass  along  the  lower  surface  of  the  embryo, 
parallel  to  each  other,  and  furnish  during  their  course  four  or  five  divisions, 
the  omplialo-mesenteric  arteries,  which  ramify  in  the  area  germinativa,  and 
open  into  a  limitary  vein  named  the  sinus  (or  vena)  tcrminalis.  From  the 
network  of  the  area  and  the  sinus  arise  two  vessels,  the  vence  omphalo- 
mesentericce,  which  enter  the  posterior  extremity  of  the  heart. 

The  circulation  in  the  umbilical  vesicle  is  somewhat  ephemeral  in 
several  species,  and  it  has  been  already  stated  that  the  vesicle  is  atrophied  at 
an  early  period  of  foetal  life.  In  birds  it  is  most  extensive  ;  and  its  presence 
may  be  noted  in  the  Carnivora  during  the  whole  term  of  uterine  existence. 

2.  Development  of  the  Heart  and  Vessels. — Placental  Circulation. — 
The  heart  which,  until  now,  was  a  cylindrical  tube,  is  considerably  modified 
before  it  attains  its  complete  development.  In  its  difierent  phases,  it 
successively  otfers  all  the  forms  known  to  exist  in  vertebrate  animals.  The 
first  change  consists  in  an  inflexion ;  the  tube  curves  in  an  S  manner,  so 


Fi2.  441. 


HEART     OF    THE     EMBRYO    OP 
RABBIT,    SEEN    FROM    BEFORE. 

ta,  Truncus  ."irteriosus ;  I,  Left  ven- 
tricle ;  r.  Right  ventricle ;  a.  Au- 
ricle ;  V,  Venous  sinus. 


THE   SAME,   SEEN   FROM   BEHIND. 

a,  Venae  omphalo-mesentericae ;  d. 
Right  auricle  ;  e,  Bulbus  aorta; ;  /, 
The  six  aortic  arches  ;  c.  Atrium  ; 
b,  Auriculje 


that  its  inferior  part  becomes  superior;  it  then  dilates  at  three  points: 
the  anterior  and  superior  dilatation  situated  at  the  origin  of  the 
aorta  is  named  the  aortic  bulb  (bulbus  aortce) ;  the  middle  dilatation,  the 
ventricular  cavity  ;  and  the  posterior  dilatation,  the  auricular  cavity.  Sailer's 
passage  is  the  name  given  to  the  constriction  between  the  auricle  and 
ventricle,  which  at  this  time  are  single.  They  do  not  remain  long  so,  how- 
ever. The  ventricular  cavity  is  the  first  to  be  divided  into  two  compart- 
ments, and  the  division  is  marked  externally  by  a  groove  which  appears  on 
the  surface  of  the  heart  of  the  Ovine  embryo  towards  the  nineteenth  day,  and 
on  the  twenty-fifth  in  the  Equine  foetus.  This  groove  corresponds  to  an  inter- 
ventricular septum  which  insensibly  rises  from  the  bottom  of  the  ventricles  ; 
when  it  reaches  the  auricles  it  concurs  in  forming  the  auriculo-veutricular 
openings.  The  margins  of  these  openings  are  provided  with  a  small  slightly 
salient  lip,  which  afterwards,  in  developing,  originates  the  mitral  and  tricuspid 
valves.  The  heart  has  now  three  cavities  :  two  ventricles  and  an  auricle  ,  but 
in  a  brief  period  the  latter  is  doubled,  and  the  comijartments  are  then  four  in 
number.    Externally,  there  is  observed  a  depression  which  shows  the  division 


916 


EMBRYOLOGY. 


in  the  auricles ;  at  a  point  corresponding  to  it,  a  septum  is  developed  in 
their  interior  which  remains  incomplete  diu-iug  the  whole  of  foetal  life,  being 

perforated   by   the  foramen   of 
Fig.  443.  Botal.      With    regard    to    the 

aortic  bulb,  it  contracts  and 
divides  into  two  vessels,  the 
aorta  and  pulmonary  artery. 

The  arteries  are  developed 
partly  at  the  expense  of  the 
vessels  of  the  primary  circula- 
tion, and  partly  in  the  vascular 
lamina  of  the  embryo.  The 
heart,  when  it  was  only  a  simple 
cylindrical  tube,  presented  at 
its  anterior  extremity  two  aortic 
arches,  which  curved  backwards 
and  united  to  form  the  single 
aorta,  then  the  vertebral  or 
common  aortae.  The  aortic 
arches  are  situated  at  the  inner 
face  of  the  two  first  pharyngeal 
arches;  afterwards  more  are 
developed,  which  are  placed 
within  the  other  pairs  of  arches, 
until  the  number  is  increased  to 
five,  though  they  never  all  exist 
at  the  same  time.  Some  atrophy, 
THE  EIGHT  AURICLE  whilc  othcrs  aro  being  developed : 
the  two  first  entirely  disappear ; 
the  third  form  the  carotids :  the 
fourth  the  axillary  arteries  and 
the  arch  of  the  aorta  ;  the  fifth 
atrophies  on  the  right,  and  on 
the  left  originates  the  pulmonary  artery,  the  ductus  arteriosus,  and  the  aorta. 
The  latter  is  continued  along  the  spine  by  the  fusion  of  the  two  primitive 
aortae ;  they  present,  at  their  posterior  extremity,  the  pelvic  vessels,  which 
are  very  small,  and  the  umbilical  arteries,  which  are,  on  the  contrary, 
remarkable  for  their  volume. 

The  peripheral  arteries  arise,  independently  of  the  central  vessels,  on  the 
interior  of  the  vascular  lamina.  They  appear  in  the  form  of  solid  cellular 
branches,  which  are  hollowed  in  the  centre  by  a  cavity  in  which  the  cells 
become  free.  In  proportion  as  these  new  vessels  are  developed,  the  omphalo- 
mesenteric vessels  disappear,  until  at  last  there  only  remain  one  or  two  ducts 
that  pass  to  the  umbilical  vesicle. 

The  umbilical  veins  are  developed  immediately  after  the  formation  of  the 
omphalo-mesenteric  veins  ;  they  enter  the  common  trunk  of  the  latter,  and 
when  its  ramifications  diminish  in  volume,  the  umbilical  veins  increase 
rapidly ;  when  the  liver  is  formed  around  them,  they  throw  into  it  branches, 
which  are  the  rudiments  of  the  hepatic  network.  Between  the  hepatic  and 
subhepatic  veins,  the  umbilical  vein  communicates  with  the  vena  cava  by 
the  ductus  venosus  of  Aranzi,  which,  according  to  M.  Colin,  does  not  exist  in 
the  foetus  of  Solipeds  in  the  last  moiety  of  uterine  life. 

The  veins  of  the  embryo  form  four  principal  trunks  at  first :  two  anterior, 


HEART  OF  AN  EQUINE  FCETUS. 

AND   POSTERIOR   VENA  CAVA  HAVE  BEEN  OPENED 
TO   SHOW   THE   FORAMEN   OF   BOTAL. 

1,  Left  ventricle  ;  2,  Right  ventricle ;  3,  Interior  of 
the  right  auricle  ;  4,  Posterior  vena  cava ;  5,  Fora- 
men of  Botal. 


THE  FCETVS. 


917 


the  anterior  cardinal  veins ;  and  two  posterior,  the  posterior  cardinal  veins. 
The  veins  of  the  same  side  unite  in  twos,  from  which  result  the  Cuvierian 
ducts ;  these  open  transversely  into  the  omphalo-mesenteric  trunk  close  to 
the  auricular  cavity. 

The  anterior  cardinal  veins  issue  from  the  cranium ;   they  form  the 
jugular  veins,  and  communicate  by  an  anastomosis  that  extends  transversely 


PLAN   OF   THE   AORTA   AND   ITS   ARCHES   AT   AN   EARLY   PERIOD. 

1,  Truncus  arteriosus,  with  one  pair  of  aortic  arches,  and  dotted  lines  indicating  the 
position  of  the  second  and  third  pairs.  2,  The  same,  with  four  pairs  of  aortic 
arches,  and  indications  of  the  fifth.  3,  The  same,  with  the  thi'ee  posterior  pairs 
of  aortic  arches,  from  which  the  permanent  vessels  of  the  embryo  are  developed, 
with  dotted  outlines  showing  the  position  of  the  two  (now)  obliterated  anterior 
arches.  4,  Permanent  arterial  trunks  in  their  primitive  form,  the  obliterated 
portions  still  shown  in  dotted  outline,  1-5,  Primitive  aortic  arches. — a,  Aorta  ;^, 
Pulmonary  artery ;  p\  p",  Branches  to  the  lungs ;  aw',  Koot  of  thoracic  aorta 
(ad)  on  left  side  j  aw,  Obliterated  root  springing  from  right  side  ;  s",  s'.  Subclavian 
artery ;  v.  Vertebral ;  ax.  Axillary ;  c.  Common  carotid ;  c'.  External  carotid ; 
c".  Internal  carotid. 

from  left  to  right.  Below  this  anastomosis,  the  left  vein  gradually  atrophies, 
as  does  the  Cuvierian  duct  of  the  same  side  ;  but  the  canal  on  the  right  side 
increases,  and  becomes  the  anterior  vena  cava. 

The  2)osterior  vena  cava  appears  behind  the  liver  towards  the  fifth  month ;  it 
receives  the  veins  of  the  kidneys  and  Wolffian  bodies,  and,  behind,  it  anasto- 
moses with  the  cardinal  veins.  The  latter  disappear  in  their  middle  portion, 
and  are  replaced  by  the  vertebral  veins,  the  right  of  which  forms  the  vena 
azygos.  There  only  remain  the  two  extremities  of  the  cardinal  veins ;  the 
anterior  enters  the  Cuvierian  duct,  and  the  posterior  constitutes  the  hypo- 
gastric and  crural  veins.  From  this  disposition,  it  will  be  seen  that  at  first 
the  venous  system  of  the  foetus  is  perfectly  symmetrical,  but  that  in  the  adult 
animal  it  becomes  asymmetrical. 

In  consequence  of  these  successive  developments,  the  placental  circulation 
is  instituted,  and  continues  the  same  until  the  termination  of  intra-uterine  life. 
The  heart  is  always  the  organ  that  propels  the  blood,  and  this  passes  into  the 
arteries,  reaches  the  umbilical  arteries,  and  is  carried  to  the  placenta.  There 
it  is  renewed,  becomes  arterial  through  contact  with  the  maternal  blood,  and 
is  returned  by  the  umbilical  veins.  In  the  substance  of  the  liver  it  is  mixed 
with  the  venous  blood  of  the  intestines  and  posterior  extremities,  through 
the  medium  of  the  ductus  venosus,  and  at  last  arrives  at  the  right  auricle, 
then  the  right  ventricle,  from  which  it  is  propelled  by  a  contraction.  Instead 
of  going  to  the  lungs,  which  do  not  act  as  respiratory  organs,  the  blood, 
being  pressed  by  the  contraction  of  the  right  ventricle,  passes  into  the  aorta 
61 


918 


Fig.  445. 


DIAGRAM  OF  THE  CIR- 
CULATION AT  THE 
COMMENCEMENT  OP 
THE  FORMATION  OF 
THE  PLACENTA  : 
SEEN  FROM  THE 
FRONT. 

a,  Venous  sinus  re- 
ceiving all  the  sys- 
temic veins ;  6,  Right 
auricle  ;  6',  Left 
auricle  ;  c,  Right 
ventricle ;  c',  Left 
■ventricle;  (?,  Bulbus 
aorticus,  subdividing 
into,  e,  e',  e",  Bran- 
chial branches ;  f,f, 
Arterial  trunks 

formed  by  their  con- 
fluence ;  g,  g',  Vena 
azygos  superior ;  /', 
h',  Confluence  of  the 
superior  and  inferior 
azygos ;  j,  Vena  cava 
inferior ;  k,  k',  Vena 
azygos  inferior ;  m, 
Descending  aorta ; 
n,  n,  Umbilical  arte- 
ries proceeding  from 
it ;  0,  o',  Umbilical 
veins ;  q.  Omphalo- 
mesenteric vein ;  r, 
vesicle,  t ;  v,  Ductus 


EMJBBYOLOGY. 

by  the  ductus  arteriosus.  To  sum  up,  the  foetus  never 
receives  pure  arterial  blood  into  its  organs,  this  being 
always  mingled  with  venous  blood,  the  mixture  taking 
place  at  several  points  :  1,  By  the  foramen  of  Botal ;  2, 
In  the  aorta  by  the  ductus  arteriosus ;  3,  In  the  liver 
by  the  ductus  venosus.  The  head  and  neck  are  the 
parts  which  receive  the  purest  arterial  blood,  a  fact 
which  explains  the  predominance  of  the  anterior  over 
the  posterior  portion  of  the  body  of  the  foetus. 

At  birth,  the  conditions  of  existence  being  suddenly 
changed,  marked  modifications  take  place  in  the  cir- 
culatory apparatus.  The  lungs  become  the  organs  of 
respiration,  and  rapidly  increase  in  capacity ;  the  pul- 
monary artery  dilates  to  give  passage  to  the  blood  that 
flows  to  them ;  while  the  ductus  arteriosus  is  obliterated, 
in  order  to  isolate  the  arterial  from  the  venous  blood. 
This  separation  of  the  two  fluids  also  takes  place  in  the 
liver  by  the  atrophy  of  the  ductus  venosus,  and  in  the 
heart  by  the  occlusion  of  the  foramen  of  Botal ;  though, 
according  to  M.  Goubaux,  that  orifice  frequently  remains 
open  in  young  animals.  Its  persistence  has  also  been 
noted  in  the  human  adult.  Notwithstanding  the  pre- 
sence of  this  foramen,  the  circulation  cannot  be  much 
disturbed ;  as  when  the  heart  contracts,  the  auricles 
become  isolated  by  the  constricting  of  the  orifice  and 
the  raising  of  a  valve. 

DEVELOPMENT   OF   THE    RESPIEATOEY  APPARATUS. 

Observers  are  not  unanimous  as  to  the  develop- 
ment of  the  lungs.  According  to  Eeichert  and  Bischoff, 
they  arise  from  two  small  solid  cellular  masses  lying  on 
the  surface  of  the  anterior  portion  of  the  intestinal 
canal.  These  become  channeled  out  into  numerous 
ramifying  cavities  (by  the  deliquescence  or  fusion  of  the 
internal  cells),  which  communicate  with  the  trachea. 
Costa  states  that  they  commence  by  a  median,  bud-like, 
hollow  process  that  opens  into  the  oesophagus.  The 
walls  of  the  communicating  aperture  elongate  consider- 
ably, and  at  a  later  period  form  the  trachea  and  larynx; 
while  the  hollow  bud  divides  into  two  pyriform  sacs, 
each  of  which  becomes  broken  uj)  into  a  multitude  of 
subdivisions  to  constitute  the  pulmonary  lobes,  with  their 
vesicles  and  infundibula. 

The  trachea  is  completed  by  the  development  of  the 
cartilaginous  rings  in  the  tube  that  binds  the  lungs  to 
the  oesophagus.  They  appear  at  the  commencement  of 
the  third  month. 

The  larynx  is  developed  in  the  same  manner  at  the 
pharyngeal  opening ;  it  is  always  somewhat  undefined 

Omphalo-mesenteric  artery  distributed  on  the  walls  of  the  vitelline 
venosus ;  y,  Vitelline  duct ;  z,  Chorion. 


TEE  EGETUS. 


919 


during  youth,  and  its  definitive  volume  is  not  acquired  until  the  iioriod  of 
puberty. 

The  thymus  gland  appears  as  a  process  of  the  respiratory  mucous  mem- 
brane; it  seems  to  be  formed  at  the 

larynx,  and  gradually  descends  along  Fig.  446. 

the   trachea   to  the   entrance   of  the 
thorax. 


DEVELOPMENT    OF    THE    DIGESTIVE 
APPARATUS. 


^p 


In  this  paragraph,  the  develop- 
ment of  the  alimentary  canal  will  be 
first  studied,  then  that  of  the  organs 
annexed  to  it. 

A.  Alimentary  Canal. — We  have 
seen  how  the  embryo,  in  becoming 
incurvated,  divides   the   blastodermic 

municate  by  a  large  pedicle.  The  external  portion  is  the  umbilical  vesicle ; 
the  pedicle  is  the  omphalo-mesenteric  duct,  and  the  inner  part  the  intestinal 
cavity. 

The  latter  may  be  decomposed  into  three  portions :  the  anterior  intestine, 

Fig.  447. 


FIRST   APPEARANCE   OF  THE   LUNGS ; 

a,  In  a  Fowl  at  four  days ;  6,  At  six  days ;  c, 
Termination  of  bronchus  in  a  very  young 

Pig- 
vesicle  into  two  parts  which   com- 


EMBRTO  OF   DOG,   TWENTY-FIVE   DAYS   AFTER   LAST   COPULATION. 

a,  a,  Nostrils ;  b,  b,  Eyes ;  c,  c,  First  visceral  arches,  forming  the  lower  jaw ;  d,  d, 
Second  visceral  arches ;  c,  Right  auricle ;  /,  Left  auricle ;  g,  Right  ventricle ; 
h,  Left  ventricle;  i.  Aortic  bulb;  k,  k,  Liver,  between  the  two  lobes  of  which  is 
seen  the  divided  orifice  of  the  omphalo-mesenteric  vein  ;  I,  Stomach ;  m,  Intestine, 
communicating  with  the  umbilical  vesicle,  n,  n ;  o,  o,  Corpora  Wolffiana;  p,  Al- 
lantois;  q,  q,  Anterior  extremities;  r,  r,  Posterior  extremities. 


which  forms  the  pharynx  and  oesophagus ;  the  posterior  intestine,  that  gives 
rise  to  the  rectum ;  and  the  middle  intestine,  which  becomes  the  stomach 
and  intestines. 


920  EMBRYOLOGY. 

The  middle  intestine  appears  at  first  as  a  uniform  cylindrical  tube,  whose 
diameter  is  afterwards  modified  to  constitute  the  organs  comprised  between 
the  oesophagus  and  rectum. 

1.  Mouth. — It  begins  by  a  depression  limited  by  the  maxillary  buds; 
this  blind  pouch  gradually  enlarges  inwardly,  and  proceeds  to  meet  the 
pharynx,  from  which  it  is  only  separated,  at  a  certain  period,  by  a  thin 
membrane  ;  this  is  at  last  absorbed,  and  the  two  cavities  then  communicate. 
Until  the  third  month,  the  mouth  is  confounded  with  the  nasal  cavities ;  at 
this  time  the  palate  appears,  and  eventually  isolates  them. 

2.  Tongue. — Appearing  at  first  as  a  small  prominence  from  the  maxillary 
buds,  the  tongue  is  completed  by  the  addition  to  it  of  a  bud  from  the  second 
branchial  arch.  Its  epithelium  and  glands  come  from  the  external  blas- 
todermic lamina ;  they  are  developed  in  the  third  and  fourth  months. 

3.  Pharynx  and  (Esophagus. — These  two  organs  become  enlarged  and 
elongated  as  the  foetus  grows.  The  oesophagus  communicates  at  first  with  the 
trachea  ;  but  it  slowly  closes,  and  finally  separates  completely  from  that  canal. 

4.  Stomach. — This  is  formed  by  the  dilatation  of  the  anterior  part  of  the 
middle  intestine ;  this  dilatation  is  fusiform,  and  its  largest  axis  lon- 
gitudinal ;  it  soon  incurvates,  and  its  longest  axis  is  then  transversal.  In 
Euminants,  the  stomach  is  at  its  first  appearance  simple ;  but  before  long  it 
shows  grooves  on  its  surface,  and  in  its  interior  septa,  as  in  the  normal 
state.  During  foetal  life  this  organ  is  small ;  but  after  birth,  when  solid 
food  begins  to  be  taken,  it  augments  rapidly  in  volume.  During  lactation 
in  Euminants,  there  is  remarked  a  predominance  of  the  fourth  over  the 
other  gastric  compartments  ;  but  immediately  the  young  animal  commences 
to  consume  fibrous  aliment,  the  rumen  quickly  increases  in  size,  and  it  is 
not  long  before  it  becomes  the  most  considerable  division. 

5.  Intestines. — The  intestinal  tube  is  primarily  of  a  uniform  calibre, 
though  in  a  short  time  there  can  be  distinguished  the  various  regions  of 
which  it  is  composed.  According  to  A.  Baer,  the  caecum  is  early  seen  in 
hoofed  animals,  and  is  situated  ia  the  vicinity  of  the  omphalo-mesenteric 
duct.  This  duct  detaches  itself  from  the  extremity  of  an  intestinal  loop, 
which  is  drawn  towards  the  umbilical  ring ;  when  the  latter  is  becoming 
atrophied  and  progressing  towards  complete  obliteration,  this  loop  re-ascends 
into  the  abdominal  cavity. 

The  intestines  are  smooth  on  their  inner  face  during  the  first  two 
months  ;  but  during  the  third  they  show  their  villosities  and  the  glands  of 
Lieberkuhn.  The  Brunnerian  and  solitary  glands  are  a  little  later  in 
showing  themselves. 

6.  Bectum.— This  is  derived  from  the  posterior  intestine,  and  is  de- 
veloped like  the  other  portions. 

7.  Anus. — Towards  the  caudal  extremity  of  the  foetus  is  observed  a 
depression  analogous  to  the  buccal  cul-de  sac.  This  gradually  deepens,  and 
is  joined  to  the  rectum  and  genito-urinary  organs.  Later,  it  is  separated 
from  the  latter,  and  then  belongs  exclusively  to  the  alimentary  canal. 

B.  Annexes  of  the  Alimentary  Canal. — These  are  the  salivary  glands, 
teeth,  liver,  pancreas,  and  spleen. 

1.  Salivary  glands. — These  are  developed  in  a  solid  cellular  bud,  which 
is  related  to  the  epithelium  at  the  commencement  of  the  digestive  apparatus. 
This  bud  increases,  and  at  the  same  time  is  hollowed  into  glandular  pouches. 
The  submaxillary  gland  is  the  first  to  appear ;  according  to  Bischoff,  it  is 
entirely  formed  in  the  foetus  of  a  Cow  only  an  inch  in  length.  The  parotid 
gland  is  the  last  to  be  formed. 


THE  FCETUS.  921 

2.  Teeth. — These  organs  are  developed  in  the  interior  of  a  cavity, 
named  the  dental  follicle  or  sac,  by  means  of  the  elements  of  three  germs : 
one  belonging  to  the  ivory,  another  to  the  enamel,  and  a  third  to  the 
cemeutmn. 

Follicle. — The  dental  follicle  is  an  oval  cavity  with  walls  composed  of 
two  layers :  the  external  is  fibrous  and  complete ;  the  internal,  soft  or 
gelatinous,  is  allied  at  the  bottom  to  the  ivory  germ.  The  latter  is  a 
prominence  which  is  detached  from  the  bottom  of  the  follicle,  and  has  the 
exact  shape  of  the  tooth.  Its  structxire  comprises,  in  the  centre,  delicate 
connective  tissue  provided  with  vessels  and  nerves,  and  on  the  surface  a 
layer  of  elongated  cells.  At  the  summit  of  the  follicle,  facing  the  ivory 
germ,  is  the  enamel  germ  ;  it  is  exactly  applied  to  the  dental  pulp  which  it 
invests  like  a  cap,  and  is  composed  of  a  small  mass  of  mucous  connective 
tissue  covered  by  a  layer  of  cylindrical  cells,  joined  to  the  buccal  epithelium 
by  the  guhernaculum  dentis.  The  cementum  organ  manifestly  exists  in  the 
Foal,  according  to  M.  Magitot.  The  base  of  the  ivory  germ  has  been  found, 
but  it  disappears  rapidly  after  having  performed  its  function. 

How  are  the  diiferent  parts  of  the  dental  follicle  developed  ?  On  the 
free  borders  of  the  raaxillse  the  epithelium  of  the  buccal  mucous  membrane 
forms  an  elongated  eminence — the  dental  ridge.  Below  this  ridge,  the 
epithelium  constitutes  a  bud  which  develops  in  size,  and  is  simk  in  the 
mucous  membrane  :  this  is  the  enamel  germ  ;  it  has  a  layer  of  cylindrical 
cells  on  its  deei)  siu'face,  and  in  its  centre  are  round  cells.  After  a  certain 
time,  it  is  only  joined  to  the  epithelium  by  a  very  thin  line  of  cells — the 
giibernaciilmn  dentis.  While  this  enamel  germ  grows  downwards,  it  covers, 
by  its  base,  a  connective  bud  which  rises  from  the  mucous  derma.  The 
two  buds  are  reciprocally  adapted  to  each  othei*,  and  around  them  the 
connective  tissue  condenses,  and  gives  rise  to  the  walls  of  the  follicle.  It 
will  therefore  be  seen,  that  the  enamel  organ  is  a  dependency  of  the 
epithelium,  and  the  ivory  organ  a  production  of  the  mucous  derma. 

Formation  of  tlie  ivory,  enamel,  and  cementum. — The  ivory  and  enamel 
are  developed  by  the  modification  of  the  elements  situated  at  the  sm-face  of 
their  germ. 

It  has  been  shown  that  the  germ  of  the  ivory,  or  dental  pulp,  had 
exactly  the  form  of  the  future  tooth  ;  consequently  the  ivory  which  arises 
from  its  periphery  ofiers  the  shape  of  this  tooth.  The  ivory  {dentine)  is 
constituted  by  the  cells  of  the  germ,  which  elongate,  send  out  prolongations 
— the  dental  fibres — that  ramify  and  anastomose,  and  by  an  intercellular 
substance  which  is  impregnated  with  calcareous  matter,  is  moulded  around 
these  fibres,  and  forms  the  dental  canaliculi. 

The  enamel  is  derived  from  the  deep  cells  of  its  germ,  which  are 
elongated  and  prism-shaped,  and  are  calcified  in  becoming  applied  to  the 
surface  of  the  ivory. 

The  cementum  is  developed  at  the  expense  of  the  walls  of  the  follicle, 
according  to  the  mode  of  ossification  of  the  connective  tissue. 

Eruption. — As  the  ivory  is  formed,  the  tooth  increases  in  length  and 
presses  the  enamel  germ  upwards;  the  latter,  constantly  compressed, 
becomes  atrophied,  and  finally  disappears  when  the  tooth  has  reached  the 
summit  of  the  follicle.  In  the  same  way  the  young  organ  pierces  the 
dental  follicle  and  gum,  and  makes  its  eruption  externally. 

Such  is  the  mode  of  development  of  the  caducous  teeth,  and  the  per- 
manent ones  are  formed  in  the  same  manner.  There  is  seen,  during  the 
development  of  the  enamel  germ  of  the  temporary  tooth,  a  bud  detaching 


922 


EMBRYOLOGY. 


itself  from  this  germ,  and  passing  backward  to  serve,  at  a  later  period,  in 
forming  the  persistent  tooth. 

3.  The  liver. — This  gland  commences  to  be  developed  very  early  in  all 
the  species.  It  apj)ears  on  the  surface  of  the  duodenum  in  the  form  of  two 
or  more  buds,  according  to  the  number  of  lobules  in  the  adult  liver.     To 

these  external  buds  are  correspond- 
Fig.  448.  jjjg  internal  ones,  arising  from  the 

intestinal  epithelium.  The  first 
enlarge  and  envelope  the  omphalo- 
mesenteric vein  ;  the  second  ramify 
in  their  interior,  and  form  the 
system  of  biliary  canals. 

The   liver  grows  rapidly,  and, 
towards    the    third    month,   almost 
entirely  fills  the  abdominal  cavity  ; 
at  a  later  j)eriod  its  growth  is  less 
opaGiN  OF  THE  LIVER  FROM  THE  INTESTINAL   niarkcd,  although  at  birth  it  is  yet 
WALL  IN  THE  EMBR\'o  OF  THE  FOWL,  ON  THE  proportionally  larger  than  in  adult 

FOURTH   DAY   OF   INCUI5ATI0N.  J^-fg 

a,  Heart ;  6,  Intestine  ;  c,  Everted  portion,  giving  4^     Pancreas.  —  The      pancreaS 

origin  to  liver :  rf,  Liver;  e.  Portion  ofvitel-    £     i.  ti  ai  t 

line  vesicle.  "^  vil«i    g^.g^     appear,    like     the    salivary 

glands,    in   the    form   of    a   solid 
cellular  bud,  which  afterwards  is  channeled  into  ramescent  cavities. 

5.  Spleen. — According  to  Bischoff,  this  body  is  developed,  during  the 

second  month,  on  the  large  curvature  of  the  stomach.     Arnold  states  that  it 

is  formed   at   the  same  time    as   the  liver,  in  a  strip  extending  from  the 

stomach  to  the  duodenum.     It  subsequently  separates  from  the  pancreas  and 

becomes  fixed  to  the  stomach,  where  its  elements 

Fig.  449.  assume  the  character  of  spleen  tissue. 

DEVELOPMENT    OF   THE   GENITO-TTEINAEY    APPARATUS. 

The  development  of  the  genital  is  related  to  that 
of  the  urinary  organs,  as  the  apj)aratus  they  form 
have  some  parts  in  common. 

Immediately  after  the  formation  of  the  intes- 
tines, the  genito-urinary  organs  are  supplied  by  the 
Wolffian  bodies.  These,  also  named  the  primordial 
Jcidneys  and  bodies  of  Olcen,  are  glandular  in  structure, 
and  extend  in  front  of  the  vertebral  column  from  the 
heart  to  the  pelvis.  They  are  composed  of  small 
transverse  canals,  filled  with  a  whitish  fluid,  which 
enter  a  common  excretory  duct  that  lies  parallel  to 
the  spine,  and  opens  inferiorly  into  that  portion  of 
the  allantois  that  becomes  the  bladder.  The  Wolf- 
xjRiNARY  APPARATUS  IN  fiau  bodies  are  placed  behind  the  peritoneum,  and 
THE  EARLY  EMBRYO  OF  ^rc  attached  by  two  serous  folds :  an  anterior,  the 
diapliragmatic  ligament,  and  a  posterior,  the  lumbar 
ligament  of  the  corpora  Wolffiana.  The  organs  furnish 
a  liquid  analogous  to  the  urine ;  though  it  is  not 
long  before  their  secretion  undergoes  great  modi- 
fications ;  indeed,  these  bodies  soon  atrophy,  and  dis- 
.ppear  more  or  less  rapidly,  according  to  species.     One  j)ortion  serves  for 


STATE     OF     THE     GENITO- 


THE    BIRD. 

«,  Corpora  Wolffiana ;  6,  b, 
Their  excretory  ducts; 
c,  Kidneys;  d,  Ureter; 
e,  e.  Testes. 


THE  FCETU8.  923 

tlae  development  of  the  genital  organs  ;  the  other  gives  rise  to  organs  vehose 
signification  is  unknown — such  as  the  organ  of  RosenmuUcr,  which  is  very 
developed  in  the  Mare,  and  the  canals  of  Gaertner,  visible  in  the  Cow  (Marc, 
and  Pig). 

A.  Urinary  Organs. — We  have  seen  above  how  the  allantois  is  derived 
from  the  terminal  portion  of  the  intestine  ;  it  has  now  to  be  stated  that  the 
bladder  is  derived  from  the  allantois.  This  reservoir  is  the  result  of  the 
dilatation  of  the  abdominal  portion  of  the  allantois.  During  foetal  life,  the 
bladder  is  extended  by  the  urachiis  to  the  umbilical  ring ;  but  after  birth 
the  urachus  is  obliterated,  and  the  bladder  is  withdrawn  into  the  pelvic 
cavity.     Hereafter  we  shall  study  the  urethra. 

The  liklneijs  appear  a  long  time  after  the  Wolffian  bodies,  in  the  shape  of 
two  blind  pouches  constituted  by  a  pushing  back  of  the  upper  wall  of  the 
small  vesicle  of  the  allantois.  These  little  culs-de-sac  ramify,  and  are 
afterwards  replaced  by  solid  buds,  in  whose  interior  are  developed  the 
uriuiferous  canals  and  Malpighian  bodies.  According  to  certain  observers, 
the  kidneys  subsequently  communicate  with  the  ureters,  which  are  developed 
separately  in  the  middle  layer  of  the  blastoderm. 

(In  the  female,  the  Wolffian  bodies  do  not  entirely  disappear ;  the 
canals  of  Gaertner  and  the  bodies  of  Eosenmiiller,  situated  in  the  broad 
ligaments,  between  the  ovaries  and  Fallopian  tubes,  are  their  remains  in 
adult  life  ;  traces  of  them  are  also  found  in  the  male,  near  the  head  of  the 
ej)ididymis,  where  they  constitute  the  vas  aberrans  of  the  testicles.  The 
suprarenal  capsules  are  very  large  in  the  Equine  foetus,  being  nearly  one 
half  the  size  of  the  kidneys.) 

B.  Genital  Organs. — The  genital  apparatus  of  the  male  and  female  are 
at  first  very  much  alike  ;  indeed,  during  a  certain  period  it  is  impossible  to 
distinguish  the  sexes ;  so  that  some  authorities  have  proposed  to  term  this 
period  the  "  indifierent  state  of  the  genital  organs."  Later,  the  sexes  are 
defined ;  and  this  period  of  development  may  be  studied  in  the  internal  and 
external  organs. 

1.  Indifferent  state  of  the  internal  genital  organs. — Towards  the  sixth 
week,  there  is  observed  on  the  lower  face,  and  near  the  inner  border  of  the 
Wolffian  bodies,  a  little  white  cord,  which  increases  in  volume  and  maintains 
almost  the  same  position.  This  is  the  genital  gland,  which  is  attached  to 
the  Wolffian  body  by  serous  folds,  and  is  formed  by  a  mass  of  young  cells 
sustained  by  an  enveloping  membrane. 

The  development  of  this  gland  is  accompanied  by  the  formation  of  the 
genital  or  Midler  s  duct,  which  is  seen  to  the  inside,  and  in  front  of,  the 
Wolffian  duct.  Miiller's  duct  is  at  first  a  solid  cellular  column,  which 
afterwards  becomes  a  canal ;  it  terminates  above  in  a  blind  pouch,  and 
oj)ens,  below,  into  the  bladder,  near  the  Wolffian  duct. 

Development  of  the  internal  genital  organs  of  the  male. — These  result  from 
modifications  of  the  genital  gland  and  Miiller's  duct.  The  testicle  arises 
from  the  gland,  which  shortens  and  widens  a  little,  while  its  tissue  is 
transformed  into  seminiferous  canaliculi.  The  head  (globus  major)  of  the 
epididymis  is  formed  by  the  middle  portion  of  the  Wolffian  body ;  the  tail 
(or  globus  minor),  vas  deferens,  and  ejaculatory  duct,  are  derived  from  the 
Wolffian  duct.  Lastly,  the  vesiculce  seminales  and  the  origin  of  the  urethra 
are  formed  by  the  posterior  extremity  of  Miiller's  ducts,  which  join  and 
open  into  the  uro-genital  sinus,  as  the  very  short  canal  is  named  which 
communicates  between  the  bladder  and  cloaca.  The  developed  testicle 
remains  in  the  abdominal  cavity,  or  descends  through  the  inguinal  canal 


924  EMBRYOLOGY. 

into  the  scrotum.  The  mechanism  of  this  descent  has  been  already 
explained. 

(It  may  be  only  necessary  here  to  state,  that  in  the  Equine  species  the 
testicles  do  not  usually  descend  into  the  scrotum  until  some  time  after 
birth — about  six  months ;  while  in  other  animals  they  reach  that  sac  during 
foetal  life.  In  the  Bovine  species,  the  testes  are  in  the  scrotum  about  the 
twentieth  week  of  gestation,  and  in  the  Sheep  and  Goat  about  the  fifteenth 
week;  indeed,  it  has  been  observed  that  in  all  Euminants  their  descent  is 
effected  before  the  skin  is  covered  with  hair.  In  the  Cai'nivora,  they  are 
usually  in  the  scrotum  a  few  days  before  birth.) 

Development  of  the  internal  genital  organs  of  tlie  female. — The  ovary  is 
derived  from  the  genital  gland,  whose  anatomical  elements  are  so  disposed 
as  to  form  the  stroma,  Graafian  follicles,  and  ovules.  The  Fallopian  tube 
and  its  pavilion  are  formed  by  the  anterior  part  of  Miiller's  duct,  whose 
extremity  shows  a  small  linear  orifice.  The  uterus  and  vagina  arise  from 
the  posterior  part  of  Miiller's  ducts.  These  lie  beside  each  other,  and  end 
by  joining  behind  to  constitute  a  single  canal ;  this  fusion  giving  origin 
to  the  body  of  the  uterus  and  the  vagina. 

The  two  diverging  portions  of  the  ducts  comprised  between  the  point  of 
junction  and  the  Fallopian  tubes,  compose  the  comua  of  the  uterus. 

The  uterus  and  vagina  are  at  first  placed  end  to  end,  without  any 
apparent  separation ;  but  towards  the  sixth  month  the  neck  of  the  uterus 
commences  to  be  defined. 

2.  Indifferent  state  of  the  external  genital  organs. — The  intestine  is 
terminated  by  the  cloaca,  a  cavity  into  which  the  digestive  canal  and 
bladder  open  by  the  uro-genital  sinus.  This  confusion  quickly  ceases  by 
the  development  of  a  transverse  septum  that  divides  the  cloaca  into  two 
compartments :  the  anal  opening,  and  the  uro-genital  canal.  At  the  inferior 
end  of  the  latter  appears  the  genital  tubercle,  a  rudiment  of  the  penis  or 
clitoris,  and  which  is  surrounded  by  cutaneous  folds — the  genital  folds. 
This  tubercle  increases  in  volume,  and  has  a  furrow  passing  from  behind  to 
before.     Up  to  this  moment  it  is  impossible  to  distinguish  the  sexes. 

Development  of  the  external  genital  organs  of  the  male. — The  male  sex  is 
marked  by  the  rapid  development  of  the  genital  tubercle,  which  becomes 
the  penis,  the  extremity  of  which  enlarges  to  constitute  the  glans.  The 
genital  furrow  closes  posteriorly,  and  forms  the  urethra.  The  folds  draw 
round  to  each  other  below  the  penis,  unite  in  the  middle  line,  and  thus 
produce  the  scrotum.  Owing  to  these  modifications,  the  digestive  ap- 
paratus is  completely  separated  from  the  genito-urinary  organs,  and  the 
lu'ethral  canal  is  connected  with  the  bladder  and  the  excretory  ducts  of  the 
testicle. 

Development  of  the  external  genital  organs  of  tJie  female. — The  indifferent 
state  of  the  genital  organs  is  readily  succeeded  by  the  feminine  type.  The 
uro-genital  sinus  forms  the  vulvular  cavity  or  vestibulum  of  the  vagina, 
which  is  so  marked  in  the  lower  animals.  The  genital  tubercle  becomes 
the  clitoris ;  the  genital  furrow  closes  at  a  certain  part  to  constitute  the 
perineum;  while  the  genital  folds  form  the  labia  of  the  vulva.  The 
mammffi,  dependencies  of  the  generative  organs,  appear  after  the  first  month 
of  uterine  life. 


CHAPTER  IV. 


Fisc.  450. 


THE   OVA  OF  BIRDS. 

It  Las  been  stated,  witli  regard  to  the  ovaries  of  birds,  that  the  ovules 
compose  nearly  the  whole  mass  of  these  organs.  When  it  leaves  the  ovary, 
the  oviun  presents  the  same  parts  as  that  of  mammals,  only  differing  in 
volume,  which  is  enormous  in  birds.  It  is  in  passing  through  the  oviduct 
that  it  is  covered  with  a  thick  layer  of  albumen  and  enveloped  in  a  white 
membrane,  and  then  a  shell,  to  compose  what  is  usually  known  as  an  egg. 
It  is  therefore  composed  of  the  ovulum  and  accessory  'parts  (Fig.  450). 

OvuLUM. — There  is  found  in  the  ovulum :  1,  A  vitelline  membrane  (2), 
thinner,  proportionately,  than  that  of  mammals ;  it  is  fibrous,  and  shows  on 
a  certain  point  of  its  surface  :  2,  The  cicatricula  (8),  a  yellowish- white  disc,  in 
the  centre  of  which  exists,  3,  Purlcinjes  vesicle,  or  the  germinal  vesicle ;  the 
yolh  or  vitellus  (1),  which  fills  the  enveloping  membrane.  In  the  mass  of  the 
vitellus  is  seen  what  appears  to  be  a  bottle-shaped  cavity,  the  long  neck  of 
which  is  applied  to  the  cicatricula. 

The  vitellus  of  the  egg  of  birds  difiers  from  that  of  mammals  in  its 
anatomical  composition,  being 
entirely  composed  of  what  are 
designated  vitelline  globules. 
These  globules  are  white  in 
the  centre  of  the  egg,  and  have 
only  a  few  nuclei ;  in  the  re- 
mainder of  the  mass  they  are 
much  more  voluminous,  and 
contain  a  large  number  of 
granulations  which  give  them 
their  yellow  colour.  It  is  the 
presence  of  the  clear  vitelline 
nucleated  globules  in  the  centre 
of  the  egg,  which  has  given 
rise  to  the  surmise  that  the 
bottle-shaped  figure,  named 
the  latebra  (9)  by  Purkinje,  is 
a  cavity. 

Accessory  Parts. — These 
comprise :  1,  the  white  or 
albumen  (3),  disposed  in  three 


SECTIONAL   VIEW   OF   FOWL'S   EGG. 

1,  Yellow  yolk  composed  of  successive  layers;  2, 
Vitelline  membrane ;  3,  Layers  of  albumen ;  4, 
Two  principal  layers  of  the  lining  membrane  of 
the  shell ;  5,  Calcareous  shell ;  6,  Chalazse  ;  7,  Air- 
space between  the  two  layers  of  the  shell ;  8, 
Cicatricula,  with  its  nucleus,  beneath  which  is 
seen  the  canal  leading  down  to  ths  white  yolk 
cavity,  or  latebra,  9. 


layers  of  different  densities,  and  which  are  deposited  around  the  yolk  at 
three  different  periods  during  its  course  along  the  oviduct ;  2,  The 
clialazm  (6),  species  of  albuminous  ligaments  twisted  in  a  spiral  manner, 
and  attaching  the  yolk  to  the  testaceous  membrane ;  3,  The  testaceous  or 
shell-membrane  (4),  which  offers  towards  the  obtuse  polo  a  doubling  into 
two  layers,  between  which  are  found :  4,  The  air-chamber  (7),  so  named 
from  the  air  it  contains  ;  5,  The  shell  (5),  decomposable  into  several  layers. 
The  testaceous  or  shell  membrane  is  composed  of  a  closely  woven  fibroid 
tissue ;  it  owes  its  opacity  to  the  air  it  contains  in  its  meshes. 


926  EMBRYOLOGY. 

The  shell  is  very  solid,  and  impregnated  with  calcareous  salts ;  it  is 
perforated  by  a  multitude  of  cavities  opening  on  its  surface.  When 
closely  examined,  it  is  found  to  have  a  more  or  less  shining  aspect,  and  in 
its  mass  fine  sand-like  particles. 

Landois,  who  has  completed  the  researches  of  Wittich  on  the  ovum  of 
birds,  distinguishes  several  layers  in  the  shell ;  otherwise  their  nmnber 
varies  with  the  species.  The  shell,  acting  merely  as  a  protecting  covering, 
is  all  the  more  solid  and  complicated  as  the  eggs  are  more  exposed  to 
the  inclemency  of  the  weather. 

Independently  of  the  testaceous  membrane  which  Landois  attaches  to 
the  shell  as  a  fibrous  layer,  this  authority  also  recognises  the  uterine  gland 
layer  and  the  sjwngy  layer.  The  former  is  much  impregnated  with  cal- 
careous salts,  and  deeply  studded  with  little  round  bodies  which  are  the 
remains  of  the  uterine  glands,  and  give  to  the  shell  its  sandy  appearance. 
The  spongy  layer  is  structureless,  and  analogous  to  solidified  mucus. 

This  clescription  demonstrates  that  the  ovum  of  birds  is  distinguished  by 
the  considerable  volume  of  its  vitellus,  and  the  addition  to  it  of  those 
accessory  parts  which  give  the  egg  its  large  dimensions  and  solidity. 
These  differences  will  readily  be  understood,  when  it  is  remembered  that  the 
embryo  must  find  in  it  all  the  materials  necessary  for  its  development, 
which  takes  place  external  to  the  parent.  It  is  from  the  vitellus  and  the 
albumen  that  the  young  creature  derives  the  elements  which  the  mammal 
finds  in  the  uterine  mucous  membrane  to  which  it  is  fixed. 


INDEX. 


PAGE 

Abdomen 380 

Abdominal  aorta 524 

' cavity 380 

compai'ison  of     ...      .  385 

• ditiereutial  characters  iu      .  384 

divisions  of 381 

of  inferior        .      ,      .  238 

• lining  membrane  of       .      .381 

regions  of ib. 

reservoirs 481 

rings  of 241 

viscera  in 385 

Abdominal  salivary  gland    ,      ,      .      .  427 

Aboniasum 399 

structure  of ih. 

Absorbent  vessels      .....  627 
Accessoiy  portion  of  visual  apparatus,  816,  817 

Acervulus 681 

Adipose  cushion  of  ear 850 

Adrenals                    494 

Affluents  of  thoracic  duct    ....  637 

Aggregate  follicles 404 

Air-cells  of  lungs            468 

Air-chamber  of  egg 925 

Alimentary  canal 385,  400 

Allantoid  fluid 897 

Allantois 894,  895,  896 

chorial 897 

structure  of ib. 

Alveoli  of  glands 390 

lymphatic 632 

Alveolo-dental  periosteum   ....  347 

Amnii,  liquor 896 

Amnion 893,  896 

false 893 

Amniotic  lamina 896 

Amphiarthroses 129 

• classification  of ib. 

Ampulla  of  Yater 425,  428 

Amygdalae 335 

Amygdaloid  cavity ib. 

Anastomoses 517 

• by  arches ib. 

inosculation ib. 

■ composite ib. 

■ convergent ,  ib. 

mixed ib. 

transverse  communicating      .      .  ib. 

-         of  nerves 701 


Anatomical  elements 
Anatomy 

comparative 

definition  of 

descriptive 

general 

philosophical    . 

physiological    . 

regional 

special  . 

surgical 

topographical  . 

transcendental 

veterinary  . 

Ancyroid  cavity 
Andcrsch's  ganglion 
Aneurism 
Angiology 
Animal  amidon    . 
Annular  cartilage 

protuberance    . 

Annulus  albidus 

ovalis    . 

Anomalies  in  arteries 
Anorchidism 
Ansiform  tube  of  Henle 
Anterior  antibrachial  region 

aorta     .... 

brachial  region 

cerebellar  peduncle 

crural  region   . 

mediastinum    . 

peduncles  of  conarium 

tibial  region     . 

white  commissure  of 

Anus 

development  of 

Aorta 

anterior 


■  common 

•  comparison  of  . 
of  anterior    . 

•  differential  characters 
carnivora 

pig       • 

ruminants 

■  parietal  branches  of 

■  posterior    .      ,      . 
preparation  of       . 


brain 


PAGE 

3 

1 

ib. 

ib. 

ib. 

ib. 

ib. 

ib. 

ib. 

ib. 

ib. 

ib. 

ib. 

ib. 
691 
727 
529 
326,  499 
423 
846 
675 
821 
506 
520 
853 
488 
262 
559 
255 
678 
283 
464 
680 
298 
682 
3,414 
920 
522 
559 
522 
538 
559 
535 
537 

ib. 
535 
525 
523 
524 


41 


928 


INDEX. 


PAGE 

526 


Aorta,  visceral  branches  of       .      • 

Aortre,  primitive 91^ 

Aortic  heart ^06 

Aponeurosis 1'" 

antibrachial 261 

contentive 1°^ 

crural 2^1 

internal *^' 

fascia  lata "°^ 

gluteal -280 

perineal 863 

deep *"• 

superficial *^- 

plantar 268,308 

tibial 297 

Apparatus "^ 

circulatory,  iu  mammalia       .      .     498 

in  birds /  647 

digestive,  in  mammalia     .      .      .     325 

in  birds 435 

generative °51 

innervation,  of 650 

olfactory 815 

respiratory,  in  mammalia       .  .   .     439 

in  birds  .      .      .     ^     .      .     475 

sense,  of     ...      .     792,  815, 

smell,  of 815 

taste,  of     .......      813 

touch,  of 792 

urinary 484 

vision,  of 816 

Appendix  auricularis 503 

Aqueduct  of  Fallopius 842 

_-l- of  Sylvius 682,683 

Aqueous  humour 8^7 

. membrane  of      ...      .        «^- 

Arachnoid  membrane 663 

cranial 664 

spinal 663 

structure *^- 

ventricular 694 

Arantius,  nodule  of 505 

Aranzi,  duct  of 901,  916 

Arbor  vitae  cerebelli 688 

Arciform  fibres  of  bulb 685 

Arch  of  aorta 523 

haemal 11" 

ischial 96 

ischiatic *''• 

neural 119 

pharyngeal 912 

Arcus  aortffi 91o 

Area  germinativa 892 

pellucida '^• 

Arm,  boues  of 73 

Arms  of  pelvis  of  kidney      ....     486 

Arnold's  ganglion 720 

Arterial  zones  of  heart 508 

Arteriae  helicinte 865 

vertebralis 915 

Arteries 515 

anastomoses  of     ...      .     517 

anomalies 520 

■ course       ......     516 


acter 


Arteries,  direction    . 

dissection 

form    . 

general  considerations 

form 

injection  . 

■—  mode  of  distribution 

of  origin 

preparation    . 

relations   . 

structure. 

termination    . 

vessels  and  nerves 

abdominal,  anterior 

posterior 

subcutaneous 

accessory  thyroid  . 

anterior  dorsal  of  penis 

tibial       .      . 

asternal 

atloido-muscular   . 

auricular,  anterior 

posterior 

axillary 

collaterals     . 

comparison  of 

. differential  char 

basilar  .... 

brachial      ... 

bronchial    . 

•  broncho-cesophageal 

buccal  .... 

bulb      .... 

csecal    .... 

cardiac 

left    .      .      . 

right 

carotid,  common    . 

collateral  branches 

comparison  of 

differential  char 

external  . 

internal   . 

primitive 

centralis  retina; 

—  cerebellar,  anterior 
posterior 

—  cerebral,  anterior  . 

middle     . 

posterior. 

cerebro-spinal 

cervical,  deep  . 

inferior    . 

superior  . 

cervico-muscular   . 

transverse 

ciliary  .... 

circumflex,  of  coronary 

anterior,  of  shoulder 

posterior,  of  shoulder 

inferior,  of  foot 

circumflex  iliac 

coccygeal,  lateral  . 

middle     . 


acten 


PAGE 

516 
521 
515 

lb. 
lb. 
520 
517 
515 
520 
516 
518 
518 
520 
563 
547 
548 
576 
548 
551 
563 
577 
586 
585 
559 
560 
574 
570 
578 
559 
526 
ib. 
589 
540 
,  531 
,  523 
,        lb. 


.  575 

.  576 

.  579 

.  590 

.  581 

.  579 

.  915 
588,  826 

.  578 


cushion 


581 
ih. 
579 
578 
561 
564 
561 
ib. 
560 
588 
554 
565 
564 
554 
545 
541 
ih. 


INDEX. 


929 


PAGE 

Arteries  coaliac 527 

colic,  direct  or  right   ....     531 

left  or  retrograde     .      .      .        ih. 

collateral  of  the  cannon    .      .   551,  569 

branches 569 

of  the  digit 552 

colon,  first  of  small  colon        .      .      532 

coraco-radial 566 

coronary     .... 

coronary  circle 

corpus  cavernosum 

cremasteric 

crural 

dental,  inferior 

superior  . 

diaphragmatic 

digital  

dorsal 

anterior  of  penis 

posterior  of  penis 

duodenal     .... 

elbow,  external  collateral 

internal  collateral 

emulgent    .... 

epicondyloid     . 

epigastric   ...      - 

external  pudic 

facial    .      .      .      ■      i 

femoral       .... 

femoro-popliteal    . 

gastric        .... 

gastro-epiploica  dextra 

sinistra 

■ glosso-facial 

gluteal       .... 

great  posterior  of  thigh 

testicular 

gutturo-maxillary 

helicine       .... 

hepatic       .... 

■ humeral      .... 

collateral  branches 

deep  .      ,      .      , 

iliac,  external 

comparison  of 

differential  characters 

internal  

comparison  of 


584 
554 
543 
535 
545 
587 
589 
526 
552 
560 

ib. 
543 
528 
565 
566 
534 
566 
547 

ib. 
581 
547 
549 
528 

ib. 

ib. 
581 
542 
548 
534 
586 
865 
528 
565 


ib. 
545 
557 
in.  555 
538 
546 


differential  characters  in,  543 
531 
543 
541 

555 

ib. 

861 

559 


ilio-lumbar       ,      .      .      . 
■ muscular   .... 

•  inferior  circumflex  of  foot 
communicating    „ 

vesical     .... 

■  innominata 
innominate  branches  of  great  me 

senteric    .... 

•  intercostal 

•  internal  pudic 

• of  female    . 

• of  male 

■  interosseous,  of  fore-arm 


525 
540 

ib. 

ib. 
567 


PAGE 

Arteries,  interosseous  anterior  .      .      .  569 

metacarpal 568 

posterior       .....  ib, 

intestinal,  small 529 

ischiatic 541 

labial,  inferior 584 

superior 584 

lachrymal 588 

laminal,  anterior 555 

lateral  sacral 540 

collateral  branches      .  541 

middle 526 

terminal  branches       .  541 

lingual 582 

lumbar 526 

r-  mammary 548 

external 563 

internal 563 

masseteric 586 

mastoid 577 

maxillary,  external      ....  581 

internal 586 

maxillo-muscular 585 

median-spinal 579 

meningeal,  great 587 

mesenteric,  great 529 

anastomoses     .      .      .  532 

anterior 531 

of  left  fasciculus  .      .  529 

of  right  fasciculus       .  531 

innominate  branches  .  532 

small ib. 

metatarso-pedal 551 

muscular,  deep 548 

great  anterior     ....  ib. 

small 549 

superficial 548 

nasal 589 

obturator 542 

occipital 577 

• collateral  bi-anches  .      .      .  ib. 

occipi  to-muscular        .      .      .      .578 

(Esophageal 526 

omental 528 

omphalo-mesenteric    ....  915 

ophthalmic 588 

palatine 589 

palato-labial ib. 

pancreatic 528 

pedal 551 

perforating ib. 

■ perpendicular 553 

pharyngeal 582 

phrenic 526 

plantar 550 

cushion 553 

interosseous 550 

— ; ungual 555 

popliteal 549 

posterior  auricular      ....  585 

^—  communicating  ....  581 

• dorsal  of  penis    ....  543 

tibial 550 

collateral  branches     .  ib. 


930 


Arteries,  posterior  tibial  terminal  br 


INDEX. 


prehumeral 

preplantar  ungueal 

prepubic     . 

prevertebral     . 

profunda  femoris   . 

pterygoid   .      .      . 

pulmonary . 

preparation  of 

pyloric 

radial,  anterior 

posterior 

renal     .... 

retrograde 

sacral,  lateral  . 

sacra  media 

saphena 

scapulo-humeral    . 

small  testicular      . 

spermatic   . 

spheno-palatine 

spinous    . 

staphylin    . 

subcostal     . 

sublingual  . 

• subsacral    . 

■ subscapular 

subzygomatic  . 

superficial  temporal 

■ superscapular  . 

• supra-orbital    . 

temporal     . 

. : —  deep  anterior 

posterior 

terminalis  . 

testicular,  great    . 

small 

thoracic,  anterior  . 

external  . 

inferior    . 

internal  . 

terminal  br 

thyro-laryngeal 

trachelo-muscular 

transverse-cervical 

tranverse  of  face    . 

tympanic    . 

ulnar    .... 

umbilical    . 

uterine .... 

utero-ovarian  . 

vasa  brevia 

intestini  tenuis 

vertebral    . 

vertebralis. 

vesico-prostatic 

Arthrodia  .... 
Arthrology  .... 
Articular  cartilages  . 

surfaces 

Articulations 

in  general 

in  particular 

nomenclature 


anches 


PAGE 

anches  ib. 
565 
554 
547 
577 
548 
587 
521 
ib. 
528 
566 
567 
534 
577 
540 
526 
549 
564 
535 
534 
589 
587 
589 
561 
584 
540 
564 
586 
585 
564 
588 
585 
588 
587 
915 
534 
535 
563 

ib. 

ib. 

ib. 
576 
564 
560 
586 
587 
566 
538 
535 

ib. 
528 
529 
561 
915 
540,  861 
128 
123 
ib. 
121 


ib. 
129 
128 


Articulations,  anterior  limbs,  of 

atlo-axoid  . 

calcaneo-astragaloid 

carpal  . 

carpo-metacarpal 

chondro-costal 

chondro-sternal 

transverse 

vertebral 

coxaa 

coxo-femoral    . 

elbow    . 

femoro-tibial    . 

head 

humero-radial 

hyoideal 

interchrondral 

interhyoideal    . 

•  intermetacarpal 

interphalangeal 

first  .      . 

second 

third 

intertarsal 

intervertebral 

ischio-pubic 

laryngeal  cartilages,  ( 

metacarpo-phalangeal 

occipito-atloid 

pedal     . 

pelvic   . 

posterior  limbs 

radio-carpal 

ulnar 

sacro-iliac  . 

scapulo-humeral 

tarsal    . 

tarso-metatarsal 

• temporo-maxillar 

hyoideal 

thoracic 

tibio-fibular 

tarsal 

Arytenoid  cartilages 
Auditive  scala     . 
Auditory  apparatus 
Auricles  .... 
Auricular  facet  . 

mass 

Auriculo-ventricular  openin 

zones 

Axile  bodies  . 
Axillary  region  . 
Axis,  coeliac  . 

cylinder 

of  arteries 


Baccated  fibres  of  tooth 
Bacillary  layer  of  retina 
Balbiani's  vesicle 
Band  of  Reil  .  . 
Barbs  .... 
Bars  of  hoof  . 
Bartholine,  glands  of 


PAGE 

143 
135 
170 
148 
150 
142 
141 
ib. 
143 
160 
161 
144 
163 
135 
144 
139 
142 
139 
152 
156 


157 
171 

130 
160 
451 
153 
137 
157 
159 
ib. 
149 
147 
159 
143- 
168 
172 
138 
139 

140, 142 
167 
168 
451 
839 
837 

505,  507 
92 
500 
504 
508 
794 
231 
527 
652 
515 

346 
825 
890 
678 
34,  369 
806 
887 


INDEX. 


931 


PAGE 

Basement  membranes     ....       5,  327 

Basilar  membranes 839 

process  of  os  pedis        ....  85 

Baiihini,  valvula 402 

Bellini's  tubes 487 

Bicipital  tuberosity 256 

Bicuspid  valve 507 

Biflex  canal 794 

Biliary  ducts 423 

Bipolar  nerve-cells 653 

Bladder 49I 

attachments ib. 

development 493,  923 

form 491 

functions 493 

interior jlj. 

position 491 

relations {b. 

structure 493 

weight 491 

Blastema 327 

Blastoderm,  formation  of     ...      .  892 

development ib. 

Blind  spot 826 

Blood 498 

Bones,  in  general 6 

absolute  form       ....  11 

blood-vessels 15 

cavities 12 

cells  of 18 

configuration        ....  11 

conformation,  internal     .      .  13 

development  ....        16, 17 

direction 11 

eminences ib. 

external  peculiarities      .      .  26. 

general  principles      ...  10 

imprints 11 

internal  conformation     .      .  13 

lymphatics 15 

medulla ib. 

names 10 

nerves 15 

number 9 

nutrition  .                   ...  17 

periosteum 14 

regions 12 

relative  form        ....  11 

situation 10 

structure              ....  13 

in  birds 112 

anterior  maxillary       ....  45 

astragalus 102 

atlas 21 

axis ib. 

calcaneus 103 

calcis ib. 

capitatum 80 

carpus 78 

cervical  vertebrae 21 

coccygeal  vertebras            ...  27 

coccyx 27 

costse 67 

coxae 91 


Bones  cuboid 
cuneiform  . 

dentata 

dorsal  vertebra 

ethmoid 

falciform    . 

femur   . 

fibula    . 

first  metacarpa 

frontal 

great  cuneiform 

hamatum    . 

heart,  of     . 

humerus     . 

hyoid    . 

ilium    . 

incisive 

incus     . 

inferior  maxillary 

intermaxillary 

interparietal 

ischium 

lachrymal  . 

large  cuneiform 

lumbar  vertebr 

lunare  . 

magnum     . 

malar    . 

malleus 

maxillary,  infer 

superior 

metacarpals 

metacarpus 

metatarsus 

middle  cuneifor 

nasal     . 

navicular    . 

occipital 

OS  coronas   . 

innominatum 

orbiculare 

pedis 

penis 

palate   . 

parietal 

patella 

pedal    . 

pelvis    . 

penial   . 

peroneus     . 

pisiform 

premaxilla 

prominens  . 

pterygoid    . 

pubis    . 

pyramidal  . 

radius   , 

ribs 

sacrum 

scaphoid  of  carpus 

of  tarsus 

second  phalanx 

semilunar  . 

sesamoids    . 


932 


INDEX. 


PAGE 

Bones,  small  cuneiform  .      .      .      .      .  104 

small  sesamoid 86 

sphenoid 39 

stapes 842 

■ sternum 66 

styloid 54 

supercarpal 79 

superior  maxillary       ....  44 

supermaxilla ib. 

tarsus 102 

■ temporal 41 

third  phalanx 84 

tibia 100 

• trapezium 79 

trapezoides 81 

tricuspid 23 

turbinated 49,442 

ulnar 76 

unciform 80 

vertebra  dentata 21 

prominens 23 

tricuspid       .      .      .      .      •  ib. 

vertebrae 20 

cervical 21 

coccygeal 27 

dorsal 24 

lumbar 25 

vomer 51 

zygomatic 47 

Botal,  foramen  of 503,  916 

Bourrelet 803 

Brachial  bulb 668 

Brachio-rachidian  bulb ib. 

Brain 672 

Bristles 797 

Bronchi 460 

cartilages 461 

disposition        ......  460 

form 461 

glands 642 

relations 461 

structure ib. 

volume ib. 

Bronchial  cartilages ib. 

glands 642 

tubes 461 

Bruch,  membrane  of 822 

Brunner's  glands 403 

Buccal  mucous  membrane    ....  332 

Bulbi  fornicis      , 678 

TBstibuli     , 883 

Bulb  of  ovary 874 

of  plantar  cushion       ....  802 

of  urethra 862 

Bulbus  aortas 915 

olfactorius 692 

rachidicus  ,. 675 

Bursas,  serous 183 

Caducous  teeth 348 

Caecum 407 

of  mastoid  lobule  .      .      .      .    692,696 

of  Morgagni 335 

• pharyngeal 373 


PAGE 

Calamus  scriptorius 677 

Calcareous  powder  of  vestibule ,      .      .  839 

Calices 497 

Calyciform  papillae 336,  814 

Canal,  biflex 794 

Fontana 821 

Ga^rtner 886 

godronne 827 

Haversian 13 

hygrophthalmic 834 

inguinal 242 

Jacobson 443 

perivascular 665 

Petit 827 

Schlemm 821 

spinal 659 

Sylvius 682,683 

Canine  teeth 344,  352 

Canthi  of  eyelids 831 

Capillaries 519 

Capillary  system 518 

Capsular  ligaments 125 

Capsule  of  Glisson 422 

of  lens 826 

Capsules,  suprarenal 494 

Caput  gallinaginus 862 

Cardiac  cavity 907,  914 

ligament 389 

orifice 388 

septum 503 

Carpal  sheath 267 

Carpiis 78 

articulations 148 

bones 78 

movements 152 

Cartilage 16,  124 

of  the  tongue 336 

Cartilages,  complementary  fibro-    .      .  124 

incrustation 123 

iuterarticular      ....  124 

interosseous ib. 

stratiform 125 

cariniform 66 

costal 69 

ensiform 67 

iuterarticular  of  jaw  ....  138 

semilunar 163 

Wrisberg,  of 451 

xiphoid 67 

Cartilaginification 16 

CarUncula  lachrymalis 834 

sublingualis 372 

Cauda  equina 748 

Cava,  vena 600 

Cavernous  sinus 606 

Cavities 12 

Cell-germs 796 

Cells 3 

multiplication  of .      .      .      .  ib. 

bone 14 

calcigerous 16 

connective 4 

hepatic 422 

medullary 4 


IXDEX. 


933 


PAGE 

Cells,  nerve 4,  652 

olfactory 445 

Cellular  tissue 4 

Cementum 345,  346,  921 

Central  canal  of  spinal  cord       .      .      .     6G8 
Central  suprahepatic  veins  ....     424 

Centres  of  ossification 16 

Centrifugal  conductibility    ....      656 

nerves ib. 

Centripetal  conductibilitj'    ....        ib. 

nerves ib. 

Centrum 118 

ovale  of  Vieusseus       ....      697 

Cephalic  hood 893 

lamina _  .     907 

Cerebellar  crura 678 

peduncles 675 

ventricle    ....       679,683,688 

Cerebellum 672,686 

external  conformation       .      .      .      686 

internal  conformation       .      .      .      688 

Cerebral  hemispheres 673 

peduncles 675,  677 

trigonal 679 

ventricles 692 

vesicles 907 

Cerebro-spinal  axis 651 

nerves 700 

Cerebrum 689 

convolutions 689,  691 

external  conformation       .      .      .      690 

hemispheres 689,  691 

structure 697 

Cerumen 846 

Ceruminous  glands ib. 

Cervical  ganglia 782 

nerves .      784 

vertebrse 21 

Cervix  of  bladder 491 

of  iiterus 877 

Chalazc-e 925 

Chambers  of  the  eye 817 

Cheeks     .      .      .  "    .      .     332, 356, 359, 360 

functions 332 

structure ib. 

Chesnuts 799,812 

Chiasma  of  optic  nerves       ....      678 

Chorda  dorsalis 892,905 

Chorda  longitudinales 693 

tendince 504 

vocales 452 

Willisii 606 

Chorion  of  skin 792 

offcetus 895 

definitive 896 

primitive ib. 

Choroid  membrane  or  coat  ....     820 

anterior      ....        ib. 

posterior    ....        ib. 

structure   ....     821 

plexus,  cerebral     ....   693,  696 

zone 820 

Chyle 498 

Cicatricula    .........     925 

62 


Cilia 

Ciliary  body  . 
canal    .. 

circle    . 

ligament     . 

■ processes     . 

zone 

Ciliated  epithelium  . 
Circulation,  adult 

feet  us    . 

Circulatory  apparatus 

in  birds   . 

Circulus  venosus  orbicul 
Circumvallate  papilla 
Cistern  of  Pecquet    . 
Clark,  vesicular  column 
Claws       .... 
Cleavage  masses 
Clefts,  pharyngeal    . 
Clitoris     .... 

praputium  of  . 

Closed  follicles    . 

Coat 

Coccygeal  gland  . 
muscles 

nerves  . 

vertebrae     . 

Cochlea    .... 

membranous     . 

Coeliac  axis    . 
Cohesion        .      .      , 
Colic  mesentei'y  . 
Collateral  scala  .      j 

vessels  . 

Colon        .... 

double  . 

attachments 

capacity  . 

course 

form  . 

functions 

length 

relations 

structure 

small    . 

attachment 

course 

form  . 

interior   , 

length 

relations 

structure 

Colostrum 
Columnse  carnse 

papillares   . 

rugosffi 

Columnar  epithelium 
Columns  of  spinal  cord 
Commissures  of  frog 
— ■ —  of  inguinal  canal 

of  lips  . 

of  nostril    . 

of  optic  nerves 

of  spinal  cord  . 


of 


PAGE 

.  832 
821,  822 
.  821 
.  820 
821,822 
821,822 
820 
327 
498 
914 
498 
647 
821 
336, 814 
634 
671 
812 
891 
912 
882 

ib. 
340 
797 
781 
215 
753 

27 
837 
839 
527 
329 
383,413 
839 
517 
410 

ib. 
411 
410 
411 

ib. 
413 
410 
411 
412 

ib. 
413 
412 

ib. 
413 
412 

ib. 
413 
886 
503 

ib. 
880 
327 
669,671 
807 
242 
331 
440 
707 
669 


934 


INDEX. 


Commisures  of  vulva 

Common  aorta     . 

Comparison  of  abdominal  cavity 

of  abdominal  limb   . 

of  annexes  of  foetus 

of  aorta 

of  apparatus  of  taste 

articulations,  carpal 

coxo-femoral 

humero-radial 

interphalangeal 

radio-ulnar    . 

scapulo-liumeral 

tibia-fibular 

auditory  apparatus 

axillary  arteries     . 

bronchi 

carotid  arteries 

cerebellum 

cerebro-spinal  axis 

cerebrum    . 

external  iliac  arteries 

genital  organs,  female 

head      .... 

heart     .... 

— —  internal  iliac  arteries 

intestines    . 

isthmus  of  brain    . 

larynx  .... 

liver     .... 

lungs    .... 

mouth  .... 

muscles  of  abdominal 

arm  . 

back  . 

costal  region 

diaphragm    . 

fore-arm 

gluteal  region 

hand 

head  . 

shoulder 

sublumbar  region 

thigh       .      . 

nasal  cavities   . 

nerves,  brachial  plexus 

cranial     . 

great  sympathetic 

lumbo-sacral  pie 

oesophagus 

pancreas 

pharynx 

salivai-y  glands 

spleen   . 

spinal  cord 

• stomach 

thoracic  limb   . 

thorax  . 

thymus  gland  . 

thyroid  gland  . 

trachea 

urinary  apparatus 


PAGE 

882 
522 
385 
187 
904 
538 
814 
156 
163 
147 
159 
148 
144 
168 
850 
574 
472 
595 
689 
666 
698 
557 
888 
871 
63 
514 
545 
417 
685 
471 
434 
472 
362 
245 
260 
209 
238 
248 
274 
283 
279 
230 
310 
255 
215 
295 
449 
767 
740 
789 
778 
380 
434 
377 
372 
435 
672 
400 
89 
71 
475 
ib. 
472 
496 


PAGE 

Comparison,  venous  system        .      .      .  626 

vertebral  column  .      .            .      .  32 

visual  apparatus    .      .             .       .  836 

Complementary  apparatus  of  pedal  bone  801 

Composite  nerves 753 

Compressor  vesiculse 860 

Conarium 680 

Concha  auris 846 

cartilages ib. 

muscles ib. 

Conchal  cartilage ib. 

Confluent  of  jugulars 601 

Confluents  of  subarachnoid  fluid      .      .  664 

Congestion  of  liver 427 

Conglomerate  glands 329 

Conjuuctivre 832 

Conjunctival  tissue 4 

Connective  cells ib. 

fibres ib. 

tissue ib. 

Consistence 329 

Contractile  cells 4 

fibrillre 178 

Convoluted  tube  of  kidney  .      .      .      .  488 

Coracoid  process 73 

Corium  cutis 792,  793 

Cornea 819 

structure  of ib. 

Cornu  Ammonis 679,  695 

Cornua  of  spinal  cord 669 

of  uterus 877 

of  ventricles 695 

Corona  glandis 866 

Coronas  tubuloi'um 404 

Coronaria  ventriculi 527 

Coronary  cushion 803 

ligament ib. 

substance ib. 

■ • structure 804 

Corpora  albicans  vel  nigrum      .      .      .  875 

cavernosa 865 

fimbriata  of  fornix       ....  694 

geniculata 680 

Malpighiana 488 

nigra 823 

pyramidalia 676,  684 

quadrigemina 675,  679 

restiformia 677,^84 

Corpus  albicans 678,  695 

Arantius 505 

callosum 692,693 

cavernosum 864,  865 

external  conformation    .      .  864 

structure 865 

ciliare 821 

dentatum 688 

fimbriatum       ......  695 

geniculatum,  externum     .      .      .  680 

internum       ....   679,  680 

Highraorianum      .      .      .      .      .  854 

luteum 874 

false 875 

true ib. 

olivare 677 


INDEX. 


935 


Corpus  rhomboideum 688 

striatum 693,  695 

Corpuscula  tactus 794 

Corpuscles  of  Krause      ....   703,  832 

of  Meissner 703,  794 

Pacinian 703 

termiual  genital 866 

Cortical  layer  of  kidney       ....  487 

Corti,  membrane  of 839 

organ  of ib. 

Costae 67 

Costal  cartilages 69 

pleura 464 

region 235 

Cotyledons 886 

Cotyloid  cavity 91 

Cowper's  glands 864 

Cranial  arachnoid 664 

cavity 660 

■ dura  mater 662 

membrane 912 

nerves 703 

origin  of 704 

pia  mater 666 

Cranium,  bones  of 33 

Cremaster 852 

Cricoid  cartilage 450 

Crico-thyroid  membrane      ....  452 

• trachealis  ligament      ....  453 

Crown  of  tooth 345 

Crura  cerebelli 678 

cerebri 675,  677 

of  fornix 694,695 

of  penis 864 

Crural  aponeurosis 241 

arch ib. 

bulb 668 

internal  region 288 

ring 241 

Crus  ad  medullara  oblongatum        .      .  678 

cerebelli  ad  pontem     .       .      .      .  678 

Crusta  petrosa 346 

Cryptaa  mucosa  .......  403 

Cryptorchids 853 

Crystalline  lens 817,  826 

capsule  of     ...      .   826,  909 

structure  of.      .      .      .   818,826 

Cumulus  pi'oligeius 873 

Cuneiform  cartilages 451 

Cutaneous  gland  of  Pig         ....  794 

lamina 906 

Cuticle 792 

Cutiduris 803 

Cutigeral  cavity 806 

Cutis  anserina 793,  799 

Cuvierian  ducts 917 

Cj'sterna  chyli 634 

Cytoblasts    ' 796 

Czermak,  interglobular  spaces  of    .      .  345 


Dartos 853 

Deciduous  teeth 348,  358 

Deferent  canal 858,  859 

structure  of 860 


Deglutition  .... 
Demours,  membrane  of  . 
Dental  follicle     . 


germ     , 

pulp      ,      .      . 

tubuli   . 

Dentated  membrane 

Dentine    .... 

Derma      .... 

structure  of 

Descemet,  membrane  of 

Development  of  annexes  of  aliment 
canal 

of  auditory  apparatus 

of  brain 

of  cephalic  lamina; 

of  chorda  dorsalis 

of  circulatory  apparatus   . 

of  cranium  and  face    . 

of  digestive  apparatus 

of  fcetus 

of  genital  organs    . 

of  genito-urinary  apparatus 

of  gustatory  apparatus 

of  heart  and  vessels     . 

of  lateral  lamina   . 

of  limbs 

of  locomotory  apparatus   . 

of  lungs 

of  muscles        .... 

of  nerves     

of  nervous  system 

of  olfactory  apparatus 

of  respiratory  apparatus   . 

of  skeleton 

of  spinal  cord  . 

of  tactile  apparatus 

of  thorax    . 

of  urinary  organs  . 

of  vertebral  column 

lamina     . 

of  visual  apparatus 

Dewlap 

Diaphragmatic  pleura    . 

region  .... 

Diarthroses    .... 

Diastole  of  heart 

Differential    characters    : 
cavity  . 

air-tube  . 

annexes  of  fcetus 

anterior  limbs     . 

appai'atus  of  taste    . 

articulations. 

atlo-axoid  . 
carpal  . 
chondro-costal 
coxo-femoral  . 
femoro-tibial  . 
humero-radial 
interphalangea 

second     . 

occipito-atloid 
radio-ulnar 


abdominal 


347 
348 
345, 


rst 


PAGE 

376 
827 
,921 
,921 
,347 
345 
662 
345 
792 
793 
827 

920 
909 
907 
905 
ib. 
914 
912 
919 
905 
923 
922 
910 
915 
905 
913 
911 
918 
913 
908 
907 
910 
918 
911 
907 
910 
913 
923 
911 
905 
908 
796 
464 
245 
123 
573 

384 
461 
901 
86 
815 

135 
155 
142 
162 
167 
146 
157 
158 
137 
147 


936 


INDEX. 


PAGE 

Differential  characters,  scapulo-humeral    144 

sternal 

.      142 

tarsal   .... 

.      172 

temporo-maxillary 

.      139 

tibio-fibular     . 

.      168 

auditory  apparatus  . 

.      850 

axillary  arteries 

.      570 

brachial  plexus  . 

.      763 

carotid  arteries  . 

.      590 

cerebellum    .... 

.      689 

cerebrum      .... 

.      698 

cranial  nerves    . 

.      739 

envelopes  of  cerebro-sp 

nal 

axis 

.     666 

external  iliac  arteries    . 

.     555 

genital  organs  of  female 

.      886 

. of  male  . 

.      867 

great  sympathetic  syste 

m  .      789 

head  

55 

heart       

.     513 

intestines      .... 

.     414 

. internal  iliac  arteries    . 

.      543 

isthmus  of  brain 

.      685 

liver 

.     432 

lumbo-sacral  plexus 

.     777 

lungs 

.     470 

lymphatic  system    . 

.      645 

mouth 

.     356 

muscles 

abdominal  region 

.      245 

anterior  foot   . 

.      279 

arm     .... 

.      260 

axillary  region 

.      235 

cervical  region 

.     201 

inferior  . 

.        lb. 

superior 

.        ib. 

costal  region   . 

.     238 

diaphragm 

.      248 

facial  region    . 

.     228 

fore-arm    . 

.      270 

gluteal  region 

.      283 

head     . 

.     228 

hyoid  region    . 

.      230 

leg 

.      306 

masseteric  region 

.      229 

panniculus  carnos 

us   .      187 

shoulder    . 

.      .      254 

spinal  region  , 

.      .     209 

sublumbar  region 

.     215 

thigh   .      .      . 

.      .      294 

tunica  abdominal] 

s     .      240 

nasal  cavities 

.      .     448 

oesophagus    . 

.      .     380 

pancreas 

.      .     434 

pharynx 

.      .     376 

posterior  aorta  . 

.      .     535 

limb     . 

.      .      105 

salivary  glands  . 

.      .      370 

spinal  cord    . 

.      .      672 

spine        .... 

.      .      135 

spleen      .... 

.      .     434 

stomach  .... 

.      .     393 

thorax     .... 

,     70,  466 

thymus  gland     . 

.      .     475 

PAGE 

Differential  characters,  thyroid  gland  .  744 

urinary  apparatus    .      .      .  495 

venous  system    ....  625 

vertebral  column     ...  29 

visual  apparatus      .      ,    835,  836 

Digestive  apparatus        ....   325,  330 

of  Birds 435 

Dilator  of  the  pupil 824 

Dissection  of  artei'ies 873 

Discus  proligerus 521 

Dorsal  nerves 750 

nucleus  of  Stilling      ....  671 

vertebras 24 

Double-contoured  nerve-fibres  .      .      .  652 

Double  semicircular  centre  of  Vieussens  698 

Duct  of  Stenon 367 

of  Stenson 443 

of  Wharton 369 

ofWirsung 428 

Ducts,  accessory  pancreatic       .      .      ,  ib. 

biliary 423 

Cuvierian 917 

genital 923 

guttural 844 

mammarv 884 

Muller's  " 923 

omphalo-mesenteric    ....  894 

parotid 307 

perspiratory 794 

salivary 367,  369 

thymic 474 

Ductus  ad  nasum 834 

arteriosus 470,  916 

choledochus 424 

course 424 

structure 425 

cysticus 432 

ejaculatorius 860,  861 

galactoferus 884 

hepaticus 423 

lactiferus         884 

lymphaticus  dexter     ....  614 

pancreaticus  minor     ....  428 

prostaticus 864 

Riviniani 369 

thoracicus 634 

venosus  of  Aranzi.      .      .      .   901,916 

Duodenal  glands 403 

Duodenum 401 

Dura  mater 660,  661 

structure 661 

Duverney,  glands  of 872 

Ear,  external 846 

internal  nerves  of       .      .      .    837, 840 

middle 840 

Ear-dust 839 

Ectopia;  of  testicles 853 

Effluent  canals  of  dura  mater  sinuses   .     608 

Ejaculatory  ducts 860,  861 

Elastic  fibres 4 

Embryo-cells 891 

Embryogenous  vesicle 890 

Embryology ib. 


INDEX. 


937 


PAGE 

Embryonic  area 892 

Emergent  veins  of  spinal  sinuses     .      .      609 

Eminences 11 

Enamel    .      .      . "    .      .      .       345,  346,  921 

Enamel  organ 347,  921 

Enarthrosis 127 

Encephalic  arachnoid 664 

dura  mater 662 

pia  mater GiiG 

Encephalon 672 

as  a  whole ib. 

constitution ib. 

general  form ib. 

isthmus 673 

volume ib. 

weight ib. 

Endocardium 511 

Endolymph 837,840 

Ensiform  cartilage 67 

Envelopes  of  cerebro-spinal  axis      .      .      660 
Epeudymis  of  spinal  cord     .      .      .   668,  683 

Epidermis 795 

growth  of 796 

structure ib. 

Epididymis    . 858 

structure 859 

Epiglottis 451 

Epithelial  cells 4 

tissue 4 

Epithelium 327 

ciliated ib. 

columnar ib. 

cylindrical i6. 

pavement ib. 

simple ib. 

spherical ib. 

squamous ib. 

stratified ib. 

Erectile  tissues 578 

Ergot 797,  802,  812 

Ergot  of  Morand 699 

Essential  organ  of  vision      ....      816 

Ethmoidal  lobule 691,692 

sinus 447 

Eustachian  tube 841,  844 

valve 506,  514 

External  auditory  hiatus     ....      846 

Eye 817 

Eyelashes 832 

Eyelids 816,830 

■ commissures 830 

■ integuments 832 

structure 831 

Eye-vesicles,  primitive 908 

Falciform  ligament 382 

Fallopian  tubes 876 

functions ib. 

structure ib. 

False  glands 633 

nostril 440 

Falx  cerebelli 666 

cerebri 662 

Fang  of  tooth 345,  350 


PAGE 

Fascia  infundibuliform 852 

lata 284 

—  transversalis 242,  245 

Fasciculus,  primitive 178 

Fatty  nucleus  of  Baur 337 

Fauces 373 

isthmus  of ib. 

Femoral  region 283 

Fenestra  cochlea 8.'i8 

ovalis 837,  840,  842 

rotunda      ....       838,  840,  842 

vestibuli 837,  842 

Fenestrated  membrane 519 

Fetlocks 797 

Fibres .  4 

of  Remak 652,  782 

Fibro-cartilages,  complementary     .      .      124 

intervertebral     ....      130 

pedal  bone 801 

Fibro-intestinal  lamina 906 

Fibrous  tissue 4 

Fibrous  zones  of  heart 508 

Filiform  papillffi 336,814 

Filum  terminale 665,  908 

Fimbria  of  Fallopian  tube  ....      876 
Fimbriated  extremity  of  oviduct     .      .        ib. 

Fissure  of  Bichat 691 

interlobular 690 

interpeduncular 678 

plantar 85 

of  Sylvius 691,692 

Fissura  glaseri 587 

longitudinalis,  inferior     .      .      .      668 

superior ib. 

palpebrarum 831 

Flocculus 689 

Fluid  of  labyrinth 840 

Foetus,  development  of 905 

circulation  in 915 

Follicles,  aggregated 405 

closed 340 

hair 798 

Lieberkiihn 403 

mucous 327,  391 

simple 403 

solitary 329,404 

structure  of 329,  402 

ultimate 365 

Follicular  glands 339 

cavity  of  clitoris 882 

Fontana,  canal  of 821 

Foramen  of  Botal 503,916 

ccecum  of  Morgagni     ....     335 

of  Vicq-d'Azyr  ....      658 

commune  anterius       .      .      .   680, 682 

posterius 682 

condyloid 34 

inft-a-orbital 44 

intervertebral 24 

lacera  basis  cranii 40 

lacerum,  anterior        ....        34 

posterior ib. 

Monro,  of  .      .      .      .      682,  693,  694 

nutrient 15 


938 


INDEX. 


PAGE 

Foramen  obturator  .;....  93 

occipital 34 

ovale 40,503 

rotundum 40 

Soemmering,  of 836 

^ spinal 19 

spinosum 40 

stylo-mastoid 43 

subpubic 93 

subsphenoidal 40 

superciliary 36 

supersacral 27 

supra-orbital 36 

trachelian 34 

vertebral ih. 

Vidian 39 

Winslow 383 

Forceps  major 699 

Fore-arm,  bones  of 75 

Fore-foot,  bones  of 77 

Fore-lock 797 

Formation  of  embryo 905 

Fornix 679,  692,  694 

Fossa  centralis  retina 836 

ovalio 506 

navicularis 862 

Fossulate  papilla; 336 

Fourchette 889 

Fourth  ventricle  of  brain     ....  679 

Fovea  centralis 836 

Fra:num  lingua; 335 

prreputii 872 

Frog  of  hoof 807 

Frog-stay 807 

Frontal  horns 813 

sinus 446 

Functional  vessels  of  lungs        .      .      .  470 

Fundus  of  bladder 491 

Fungiform  papilla; 336,  874 

Funicular  ligaments       ....    125,  126 

Furrow,  primitive 892 

Galactoferous  ducts        ....   884,  885 

sinuses ib. 

Galeati's  glands 403 

Ganglia 780 

structure ih. 

Andersch's 727 

Arnold's 720 

cervical,  inferior 784 

middle ib. 

superior 782 

ciliary -718 

Cloquet's ib. 

Ehrenritter's 729 

Gasseriau 710,711 

geniculare 722 

guttural 782 

hypoglossal 739 

inferior  cervical 784 

intumescentia 722 

jugular 728,729 

lenticular 718 

— —  Meckel's 719 


PAGE 

Ganglia,  middle  cervical      ....  784 

naso-palatine 718 

ophthalmic 786 

otic 720 

petrosum 727 

semilunar 711,786 

solar 786 

spheno-palatine 719 

submaxillary 718 

superior  cervical 782 

Ganglion  cells 653 

Ganglion,  intercarotid 789 

Ganglionic  nerves 652,  701 

Gasserian  ganglion 710,711 

Gastro-colic  omentum    ....    382,  389 

Gastro-hepatic  omentum      ....  389 

Gastro-splenic  omentum      ....  383 

Gelatine  of  Wharton 900 

Gelatinous  substance  of  Rolando      .      .  670 

Gemmation 3 

Generative  apparatus 851 

of  Birds 889 

Genital  duct 923 

gland ib. 

organs  of  female 872 

— of  male 851 

tubercle 924 

Genu  of  corpus  callosum      ....  693 

Germ  of  hair 798 

Germinal  eminence 873 

spot ib. 

vesicle 873,925 

Ginglymus 128 

Glandulse  agminata; 404 

solitarise 404 

Glands 329 

agminated 404 

Bartholine,  of 887 

brachial 644 

Brunner,  of 403 

cajcal 641 

ceruminous 846 

cheeks,  of 332 

coccygeal 781 

colon,  of 641 

conglomerate 329 

Cowper's S64 

cutaneous,  of  Pig 794 

duodenal 403 

Duverney,  of 872 

follicular 339 

Galeati's 403 

gastric 391 

genital 923 

ECuttural 643 

Harder's 833,836 

honeycomb 404 

iliac 640 

inguinal,  deep 638 

superficial ib. 

intestinal 641 

interungulate  of  Sheep     .      .      .  794 

labial 331,  339,  370 

lachrymal 834 


INDEX. 


939 


PAGE 

Glands,  laryngeal 455 

lenticular 404 

Lieberkiihn's 403,  410 

lingual 335,  370 

liver 410,  642 

lobulated 329 

lymphatic 632 

mammary 884 

maxillary 367,  371 

Sleibomian 832 

molar 369,371 

mucous  of  stomach      ....     391 

Kiihn's 372 

odoriferous 445 

Pacchionian 663 

palate,  soft 343,  370 

pancreas 427 

parotid       ....       365,  370,  371 

Pecklin,  of 404 

peptic 391 

perspiratory 794 

Peyer's 404 

pharyngeal 643 

pineal 680 

pituitary 445,  681 

popliteal 640 

preputial 867 

precrural 640 

prepectoral 643 

prescapular 644 

prostate 864 

racemose 329,  339 

rectum,  of 640 

salivary 364 

simple 329 

socia  parotidis 372 

solitary 404,410 

spleen,  of 642 

staphyline 370 

stomach,  of 641 

subglossal 644 

sublingual 369,  371 

sublumbar 638 

submaxillary  .      .      .       367,  371,  644 

sudoriparous 794 

thoracic 642 

thymus 473 

thyroid 472 

tracheal 459 

tubular 329 

uterine 879 

utricular 880 

vulvo-vaginal 887 

Glandular  culs-de-sac 365 

tissue 4 

Glans  clitoridis 882 

penis ,      .      .      862 

Glenoid  cavity 73 

Glisson,  capsule  of 422 

Globes  of  segmentation 891 

Globus  major  epididymis     ....      859 

minor   ........        ih. 

Glomes  of  frog .      807 

Glomeruli  of  kidney 488 


PAGE 

Glottis 456 

Gluteal  aponeurosis 280 

region ib. 

Goose-skin 793 

Graafian  vesicles 873 

Granules,  fat 3 

pigmentary ib. 

proteic ih. 

Great  lymphatic  vein 644 

sympathetic  system     ....  781 

structure  ....  782 

transverse  cerebral  fissure      .      .  691 

Grey  nerve-libres 652 

root  of  optic  nerves     ....  683 

substance  of  isthmus  ....  685 

Gubernaculum  dentis     ....    347,  921 

testis 856 

Gum 347 

Gustative  bulbs 814 

cells 815 

Guttural  pouches 845 

Gyrus  fornicatus 695 

Habenae 681 

Hamal  arch  .      , 119 

Hrematies 4 

Hairs        .   • 797 

follicles 798 

formation  of 799 

functions ib. 

germ  of 798 

horse,  of 797 

sheath  of 798 

Haller's  passage 915 

Hand 89 

Harder,  glands  of 833,  836 

Harmonia  suture 129 

Haversian  canals 13 

Head,  bones  of 33 

in  general 54 

Heart 499 

action 513 

capacity 500 

direction ib. 

external  conformation      .      .      .  ih. 

form ib. 

general  sketch 499 

interior 503 

nerves  and  vessels  of  .      .      .      .  510 

serous  membrane 511 

situation 500 

structure 507 

volume 500 

weight ib. 

Helicine  arteries 865 

Helico-trema 838 

Hemispheres,  cerebral 673 

Hepatic  cells 422 

ducts 423 

lobules 422 

Hernia,  inguinal 547 

Herophilus,  wine-press  of    ...      .  606 

Highmorianum,  corpus 854 

Hilum  of  kidney ,  486 


940 


INDEX. 


PAGE 

Hilum  pulmonis 466 

Hippocampus 693,  695 

Ilippomanes 897 

Hollow  organs 326 

structure  of       ....  ib. 

Honeycomb  glands 404 

Hoof 800 

contents  of 800 

description  of 805 

development  of 810 

structure  of 808 

wall  of 805 

Hoof-horn 808 

structure  of ib. 

Horn  cells 809 

Horns,  frontal 813 

Horny  production 799 

Horse-hair 797 

Humours  of  eye 817,  827 

Hyaloid  membrane 827 

Hydatid  of  Morgagni 871 

Hygrophthalmic  canals        ....  834 

Hymen 883 

Hyoideal  region 225 

Hypochondriac  region 381 

Hypogastric  region 46. 

Hypophysis  cei'ebri 681 

Ileo-caBcal  valve 402,  408 

Ileum t      .  401 

Imprint 11 

Incisor  teeth       .        344,  349,  357,  359,  361 

Incus 842 

Inferior  umbilical  ring 894 

Infundibuli  of  lungs 468 

Infundibuliform  fascia 852 

Infundibulum 681 

Inguinal  canal 242 

hernia 547 

ring 242 

Injection  of  arteries 520 

-of  veins 599 

Inosculation 517 

InsuliE 635 

Integuments  of  extei'nal  ear      .      .      .  850 

Interarticular  meniseii 163 

Interauricular  partition       ....  503 

Intercarotid  ganglion 789 

Interglobular  spaces  of  Czermak     .      .  345 

Interlobular  fissure 690 

veins 423 

Internal  crural  region 288 

ear 837 

nerves  of 840 

Interosseous  cartilages 124 

Interpeduncular  fissure        ....  678 

Interstitial  substance 178 

Interuugulate  gland 794 

Interventricular  septum      ....  503 

Intervertebral  fibro-cartilages  .      .      .  130 

foramen 24 

Intestinal  groove 894 

Intestines 400 

development 920 


PAGE 

large 407 

Intestines,  large,  attachment     .      .      .  407 

capacity ib. 

dimensions ib. 

direction ih. 

functions 410 

interior 408 

relations 407 

situation ib, 

structure 410 

small 400 

attachment 401 

course ib, 

development       ....  406 

form 400 

functions 406 

interior 401 

relations ib. 

structure 402 

Intralobular  veins 424 

Iris 822 

structure  of 823 

Ischiatic  spine 93 

Isthmus  of  encephalon   .      .       673,  675,  676 

external  conformation  of     .  675 

internal  conformation  of     .  682 

structure  of 683 

of  fauces 373 

Iter  ad  infundibulum 682 

quartum  ventriculum   .      .  ib. 

Ivory 345,921 

Jacob's  membrane 825 

Jacobson,  nerve  of 728 

organ  of 443 

Jejunum 401 

Jugular  channel        ......  601 

— '■ —  vein ib, 

Keraphyllous  tissue 806 

Keratogenous  membrane      ....  803 

Kidneys   ...            484 

conformation,  external      .      .      .  ib. 

internal 486 

development 489,  923 

functions 490 

primordial 922 

proper  tissue 487 

relations     ..      =      ....  486 

situation 484 

structure   ......  486 

tunic 487 

weight 486 

Krause,  corpuscles  of     ,      ,      .      .   703, 832 
terminal  genital       .      .      .  866 

Labia  vulva; 882 

Labial  glands 331,  370 

Labyrinth 837 

osseous.      .      , 26. 

membranous 837,  838 

Lachrymal  apparatus 834 

canal j6. 


INDEX. 


941 


Lachrymal  ducts 
gland    . 

nerve    . 

sac 

Laclius  lachrymalis 
Lacteal  vessels  . 
Lactiferous  ducts 
Laniellaj  of  foot  . 
Lamina  cinerea  . 
cribrosa 

fusca     . 

spiralis 

Laminoe  of  foot   . 
Lamiual  tissue    . 
Lancisii,  chorda;  longitudina 
Large  intestine    . 
Larynx    . 

articulations 

development 

entrance     . 

external  surface 

form 

functions    . 

internal  surface 

muscles 

nerves  . 

situation    . 

structure   . 

ventricles  . 

vessels 

Latebra   . 

Lateral  columns  of  spinal 

fibro-cartilages 

lacun£B  of  frog 

laminJE  of  embi-yo 

triangular  fasciculus 

ventricles   . 

Left  auricle  of  heart 

ventricle  of  heart  . 

Leg,  bones  of      .      .      . 

— •  muscles  of 

Lens,  crystalline 

capsule  of     . 

structure  of. 

Lenticular  ganglion 

glands 

papillse 

Leucocytes     .... 
Lieberkiihn's  follicles 
glands  .... 

LiGAJIENTS    .... 

capsular  . 

funicular. 

general  consider;! 

interosseous    . 

membraniform 

peripheral 

white. 

yellow 

anterior  of  carpus 

arteriosum 

astragalo-metatarsal 

atlo-axoid,  inferior 

superior 


cord 


lis 


of 


of  is 


ition 


thm 


69 


83-4: 

ib. 
711 
834 
831 
402 
884 
850 
683 
S,  818 
819 
838 
804 

ib. 


693 
407 
449 
451 
918 
456 

ib. 
449 
456 

ib. 
453 
455,  734 
449 
450 
456 
455 
925 
669 
801 
807 
905 
678 
693 
507 
506 
100 
288 
826 
826 

ib. 

718 

404 

56,  814 

4 

403 


125 

ib. 

ib. 

ib. 
126 
125 

ib. 

ib. 
126 
148, 149 
522 
171 
136 

ib. 


Ligaments,  auditory 
bladder,  of. 

broad    .... 

calcancd-ast  ragaloid 

calcaneo-metatarsal 

capsular' of  atlo-axoid  articulation 

of  carpal  ,, 

of  costo-sternal  „ 

of  coxo-femoral  „ 

of  femoro-patellar       ,, 

of  humero-radial  „ 

of  hyoideal  ,, 

of  metacarpo-phalaugeal,,. 

of  occipito-atloid  „ 

of  scapulo-humeral  ,, 

of  teniporo-maxillary 

of  vertebral 

cardiac        .... 

carpo-metacarpal  . 

carpal,  anterior     . 

cervical      .... 

chondro-xiphoid     , 

ciliary 

common  carpal 

inferior  vertebral 

superior  cervical 

— • supersj)inous 

costo-sternal,  inferior 

superior     . 
costo-transverse,  anterio 

posterior   . 
cotyloid      .... 
coxo-femoral     . 
crico-trachealis 
cruciform   .... 
cuboiJo-cunean 
cuboido-scaphoid    . 
denticulated 
diaphragmatic. 
Fallopii       .... 
femnro-patellar 
glosso-epiglottic     . 
hepatic       .... 
hepatico-renal 
humero-radial,  external 

• — — internal  latei 

ilio-sacral,  inferior 

superior 
interannular     . 
interarticular  costo-vertebral 
intercarpal 
interlamellar   . 
interosseous  of  car))us 

• ■  radio-ulnar   . 

interphalangeal,  first 

second 

intersesamoid  . 
interspinous 
intervertebral 
latum  pulmonis 
nucha;  .... 
lobus  Spigelii,  of  . 
lumbar  of  corpora  Wolffian! 
metacarpo-phalangeal 


PACE 

842,  843 
.     491 

384,  877 
.      170 


ter 


171 
136 
151 
141 
162 
165 
146 
139 
154 
137 
143 
138 
134 
382 
150 
148,  149 
132 
142 
822 
151 
131 
ib. 
132 
142 
141 

ib. 
16'J 

ib. 
453 
137 
171 

ib. 
665 
922 
241 
165 
335 
420 
383 
145 

ib. 
159 


133 
140 
150 
133 
148,1-19 
147 
157 
ib. 
153 
133 
131 
467 
133 
383 
922 
154 


942 


INDEX. 


Ligaments,  odontoid. 

ovarian 

patellar 

pectinated  . 

peripheral,  inferior 

Poupart's   . 

pubio-femoral  . 

radio-carpal 

radio-ulnar,  interosseous 

peripheral 

external  tr: 

round,  of  uterus     . 

sacro-iliac  . 

sciatic 

scaphoido-cunean   . 

sesamoid 

inferior    . 

lateral     . 

spleen,  of   .      .      . 

stellate 

inferior    . 

subflava 

superdorso-lumbar 

superspinous  cervical 

suspensory  of  fetlock 

of  penis   . 

— of  sheath 

of  uterus 

tarsal    .... 

tarso-metatarsal,  postei 

teres     .... 

tibio-fibular 

tracheal 

transverse  . 

umbilical    . 

uterine,  broad 

rovmd 

• suspensory    . 

vulvular 

Wolffiani,  of  corpora 

Limbs  in  general 

their  parallelism    . 

Limitary  membranes 
Linea  alba     .... 
Linese  transversa; 
Lingual  canal 

glands  .... 

glandular    , 

lacunaj 

mucous  membrane 

Linguetta  laminosa  . 

Lips 

functions  of 

structure  of     . 

Liquor  amnii 

corneae 

folliculi 

labyrinth!  . 

Morgagni   . 

seminis 

Liver       

attachments     . 

development    . 


865, 


330 


.  136 
384,  873 
164 
819 
140 
241 
162 
149 
147 

ib. 

384,  877 
159 
160 
ib. 
171 
153 
ib. 
154 
429 
140, 141 
142 
133 
132 
ib. 
154 
866,  872 
867 
877 
168 
172 
162 
167 
459 
136 
491 
384,  877 
ib. 
877 
884 
922 
109 
110 
5,  327 
239,  240 
.   693 
.  334 
.   370 
.  335 
.  335 
.  814 
.  679 
, 356, 359 
.  332 
.  331 
.  896 
.  820 
.  873 
.  840 
.  826 
.  858 
.  419 
.  420 
427.  922 


PAGE 

Liver,  direction 419 

form ib. 

functions 426 

proper  tissue 422 

relations 420 

situation 419 

structure 422 

weight 419 

Lobes  of  liver 420 

Lobular  bronchial  tube         ....  468 

Lobulated  glands 329 

Lobule,  anterior  of  lung       ....  467 

Lobuli  testis 854 

Lobulus  pneumogastricus     ....  467 

Lobus  Spigelii 420 

Locomotory  apparatus 6 

Longitudinal  fissure  of  brain     .      .      .  690 

Lowenberg's  scala 839 

Lumbar  nerves 751 

vertebrce     .            25 

Lumbo-rachidian  bulb 668 

Lumbo-sacral  plexus 770 

Lungs 466 

development 470,  918 

form 466 

functions 470 

fundamental  tissue      ....  467 

general  disposition       ....  466 

relations ib. 

serous  envelope 467 

situation 466 

structure 467 

Lymph 498 

Lymphatic  glands  and  vessels    .      .      .  628 

course      .      .      .  631 

form        ...  628 

number    .      .      .  ib. 

plexuses  .      .   629,  631 

preparation  of     .  663 

rete  mirabile.      .  631 

structure       .    628,  633 

termination   .      .  631 

Lymphatics,  Birds,  in 649 

bladder,  in 493 

bone,  in      .      ^     ....      15, 630 

brachial 644 

bronchial 642, '461 

cjEcum,  in 641 

colon,  large,  in ib. 

small,  in 640 

guttural 643 

heart,  in 511 

hepatic  lobules,  in       ....  424 

iliac 640 

inguinal,  deep 638 

superficial ib. 

intestines,  in    .      .      .        641, 406, 410 

kidneys,  in 489 

laryngeal 455 

lips,  in 331 

liver,  in      ......      .  425 

lungs,  in 470 

mucous  membranes,  in      .      .      .  629 


INDEX. 


043 


PAGE 

Lymphatics,  muscle,  in.      .      .      .    180,630 

nervous  tissue,  in 630 

nostrils,  in 441 

ovary,  in 874 

penis,  in 863 

peritoneum,  in 384 

pharyngeal 643 

pia  mater,  in 665 

pituitary 446,  447 

popliteal 640 

precrural ib. 

pi'epectoral 643 

prescapular 644 

rectum,  in 640 

serous  membranes,  in        ...      630 

skin,  in 629,  795 

■ small  intestines,  in      ...      .     406 

spleen,  in 431,  642 

— -—  stomach,  in 392,  641 

subglossal 644 

sublumbar 638 

submaxillary 644 

suprarenal  capsules,  in      .      .      .      494 

testicle,  in 856 

thorax,  in 642 

thymus  gland,  in 473 

thyroid  gland,  in 472 

urethra,  in 863 

uterus,  in '    880 

vagina,  in 882 

vessels,  in 630 

Lymphatic  sheaths 520,  630 

sinuses 632 

Macula  lutea 836 

Malleus 842 

Malpighian  corpuscles    ....   430,  487 

glomerules 489 

MamnicTe 884 

form ib. 

functions 885 

situation 884 

structure ib. 

Mammary  ducts ib. 

glands ib. 

Mammilla ib. 

Mammillary  tubercle 687 

Manubrium 842 

Many];lies 397 

Masculine  uterus 861 

Mastoid  cells  of  ear 840,  842 

• lobule  of  brain       ....   691,692 

Matrix  of  hoof 800 

Maxillary  gland 367 

Meatus  auditorius  externus       .      .      .  846 

nasal 442 

urinarius,  female 882 

valve  of ib. 

Meckel's  cartilage 912 

ganglion 719 

^Meconium 427 

Median  lacuna  of  frog 807 

sinus 606 

Mediastinal  pleura    .      .      .      .      .      .  464 


PAGE 

Mediastinum,  anterior    .      =      ,      ,      .  464 

posterior .  ib. 

testis 854 

Medulla  of  bones 15 

Medulla  oblongata 675,  676 

Medullary  cells 4, 15 

layer  of  kidney 487 

Medullated  nerve-tibrcs 652 

Medullo-cells 4,  15 

Meibomian  glands     .      .      .        830,  831, 832 

Meissuer,  corpuscula  tact  us  of  .      .      .  794 

Membrana  dentata 666 

granulosa 873 

Jacobi 825 

nictitans 833 

pupillaris 824,  909 

tympani 841 

secundaria 842 

vitellina 873 

Membrane  of  aqiieous  humour  .      .      .  827 

basilar 839 

Bruch,  of 822 

choroid 820 

conjunctival 832 

Corti,  of 839 

Demours,  of 827 

dentated 662 

Descemet,  of 827 

eye,  of 817 

fenestrated 519 

hyaloid 827 

keratogenous 803 

mucous 326 

Reissner,  of 839 

serous 328 

Membranous  cochlea 839 

semicircular  canals      ....  ib. 

urethra 861 

vestibule 838 

Meningeal  granulations        ....  663 

Meninges  of  cerebro-spinal  axis       .      .  660 

Meniscii,  interarticular        ....  163 

Mesenteric  glands 641 

Mesenteric  lamina 906 

Mesentery 383,401 

colic 383,384,413 

proper 383 

Meso-cfficum 383,  407 

Mesocephalon 675, 677 

Meso-colon 383 

Meso-rectum 413 

Metacarpo-phalangeal  sheath     .      .      .  267 

Metacarpus 81 

Metatarsus 105 

Middle  cerebellar  peduncle  ....  678 

ear 840 

septum  of  nose 444 

ventricle  of  brain 682 

Milk 885 

Milk-fountains 625 

Mitral  valves 507 

Mixed  nerves 700 

Modiolus 838 

Molar  glands 36& 


944 


INDEX. 


Molar  teeth    . 
Monorchids    . 
Monro,  foramen  of    . 
Jlons  veneris 
Morgagni,  ca?cum  of 

hydatid  of . 

liquor  of    . 

Morsus  diaboli     . 
Motores  oculorum     . 
Mouth      .      .      ■      . 

development  of 

in  general  . 

Mucous  derm 

corium 

membrane  . 

of  bladder 

of  bronchi 

of  cheeks 

of  Fallopian  tubes 

of  guttural  pouches 

of  internal  ear 

of  intestines,  lar 

of  lar3'nx 

• of  lips 

lymphatics  in 

• of  mouth 

of  oesophagus 

olfactory 

of  pharynx    . 

of  sinuses  of  head 

of  soft  palate 

of  stomach    . 

of  tongue 

of  trachea 

of  tympanum 

of  ureters 

of  uterus 

of  vagina 

of  vulva  . 

jMiiller's  duct 
Multipolar  nerve-cells    . 
Muscle-plasma    . 
Muscles: — striped  in  gener 

action 

attachments  . 

appendages     . 

classification  . 

contractility  . 

development  . 

direction  . 

form   . 

general  table  of 

in  Birds    . 

insertions 

lymphatics     . 

manner  of  studying 

nomenclature 

physico-chemical  pr 

physiological  proper 

preparation  of 

preservation  of 

relations  . 

situation  . 


PAGE 

352,  359,  361 
,  .  .  853 
682,  693,  694 


les 


335 
871 
826 
876 
708 
330 
920 
355 
327 
ih. 
326 
493 
461 
331 
876 
845 
840 
410 
402 
Abb 
331 
629 
355 
379 
444 
374 
447 
343 
390 
335 
459 
844 
490 
879 
880 
883 
923 
653 
181 
174 
182 
175 
183 
ib. 
181 
181,913 
175 
174 
315 
313 
175 
180 
183 
176 
180 
ih. 
184 
185 
176 
174 


Muscles,  structure    . 

tissue 

uses    .... 

vessels  and  nerves 

volume     . 

imstriped    .... 

accelerator  urina;  . 

adductor  of  arm    , 

adductor  femoris   . 

longus 

tibialis    . 

alveolo-labialis 

anconeus     .•      .      .      . 

angularis  scapulae 

antea-spinatus 

anterior  constrictor  of  vulva 

extensor  of  metacarpus 

— ■ —  of  phalanges 

medius    . 

straight  of  thigh 

ulnaris    . 

arytenoideus     . 

— — •  aryteno-pharyngeus     . 

basio-glossus    . 

biceps  abductor  femoris 

brachial  biceps 

bronchial    .... 

buccinator 

bulbo-cavernous    . 

caput  magnum 

medium  . 

parvum  . 

ciliaris        .... 

circumflexus  palati 

common  intercostals    . 

complexus  major   . 

minor 

compressor  coccygis    . 

urethrse  . 

vesiculae 

constrictor  of  pharynx,  fir 

inferior 

second  middle 

:uperior     . 

vaginae    . 

vulvae,  anterior 

posterior    . 

coraco-brachialis    . 

humeralis 

corrugator  supercilii  . 

cremaster  .... 

crico-arytenoideus  lateral 

posticus 

pharyngeus  . 

thyroideus    . 

crotaphitic 
crural  triceps  . 
curvator  coccygis 

dartos  

deep  flexor  of  phalanges 

gluteal    . 

pectoral  . 

depressor  coccygeus     . 
laiii  iuferioris    . 


PAGE 

178 

ib. 

182 

180 

174 

4,328 

2,  863 

253 

291 


287 
218 
260 
189 
251 
884 
262 
263,  298 
222 
284 
266 


.Idle 


375 
337 
286 
255 
461 
218 
862 
258 
259 

ib. 
821 
342 
208 
191 
195 
217 
863 
860 
374 

ib. 

ib. 

ib. 
883 


883 
254 

lb. 
831 
852 
454 

ih. 
374 
453 
223 
284 
216 
853 
268,  305 
282 
233 
216 
222 


INDEX. 


945 


PAGE 

Muscles,  depressor  labii  superioris        .  222 

diaphragm 245 

digastricus 225 

dilatator  naris  anterior     .      .      .  221 

lateralis      ....  ib. 

erector  clitoridis 882 

cocc_vgeus 216 

penis 864 

extensor  metacarpi  magnus    .      .  262 

■ obliquus    ....  263 

pedis 263,  298 

suffraginis 264 

external  flexor  of  metacarpus       .  265 

• intercostals 237 

oblique  of  abdomen        .      .  240 

obturator 292 

pterygoid 224 

vastus 285 

extrinsic  of  tongue      ....  337 

fascia  lata 284 

fleshy  panniculus 186 

flexor  brachii 255 

metacai-pi  externus  .      .      .  265 

' internus     ....  266 

medius       ....  H), 

metatarsi 300 

parvus       ....  311 

pedis 305 

accessorius       .      .      .  306 

perforans  ....  268 

perforatus        .      .      .  267 

fronto-superciliary      .      .      .      .431 

gastric 389 

gastrocnemii 302 

gastrocnemius  externus     .      .      .  ih. 

internus 304 

gemelli  of  pelvis 293 

of  tibia 302 

gemini 293 

genio-glossus 338 

hyo-glossus ib. 

'          hyoideus 226 

gluteus  externus 280 

internus 282 

maximus 281 

medius j-5_ 

gracilis 289 

great  adductor  of  thigh    .      .      .  291 

anterior  straight  of  head     .  199 

complexus 191 

dorsal !  203 

hyo-glossus 337 

oblique,  of  abdomen       .      .  248 

of  head       ....  193 

psoas 21'' 

rectus,  of  abdomen  .      .      .  243 

serratus 236 

supermaxillo-nasalis       .      .  221 

heart,  of 509 

humeralis  externus      ....  256 

hj'o-epiglottideus 453 

glossus  brevis     ....  337 

longus        ....  ib. 

pharyngeus 374 


Muscles,  hyo-thyroideus       ....  453 

hyoideus  magnus 227 

:: — parvus ■  "j-^^ 

iliac  psoas 212 

iliacus *  j-j,_ 

ilio-spinal 2O6 

internal  flexor  of  metacarpus       .  266 

intercostals 237 

oblique  of  abdomen        .      .  242 

obturator 292 

pterygoid 224 

vastus 285 

interossei 278 

intertransversales  lumborum        .  215 

intertransverse  of  loins     .      .      .  ib, 

of  neck 193 

intestinal    ....        402  212  414 

intrinsic  of  tongue       ....  337 

ischio-cavernosus 864 

coccygeus 217 

urethral 863 

kerato-glossus 337 

kerato-hyoideus 227 

labialis 217 

lachrymal 320 

lachrymo-labialis 220 

large  extensor  of  fore-arm      .      .  258 

lateral  extensor  of  phalanges     264,  298 

lateralis  sterni 236 

latissimus  dorsi 203 

levator  ani 863 

humeri 197 

labii  superioris   ....  220 

meiiti 222 

palpebrffi 832 

levatores  costarum      ....  237 

• liugualis 33c) 

superficialis 337 

long  abductor  of  arm        .      .      .  249 

adductor  of  leg  .      .      .      .  288 

extensor  of  fore-arm      .      .  258 

■ flexor  of  fore-arm     .      .      .  255 

of  neck 2OO 

■ longissimus  dorsi 2O6 

longus  colli 200 

lumbrici 278 

masseter 223 

mastoido-auricularis    ....  849 

humeralis igg 

maxillo-labialis 222 

mento-labialis j5_ 

middle  extensor  of  fore-arm   .      .  259 

■ mylo-hyoideus 225 

nasalis  brevis 221 

longus 220 

oblique  extensor  of  metacarpus    .  263 

flexor  of  metacarpus      .      .  266 

of  phalanges    .      .      .  306 

obliquus  capitis  amicus    .      .      .  199 

inferior      ....  123 

superior     .      .      .      .194 

externus  abdominis        .      .  240 

internus  abdominis         .      .  242 

oculi  inferior      ....  830 


946 

Muscles,  obliquus  oculi  superior 

obturator  exteruus 

internus  .... 

occipito-styloideus 

oesophageal       .... 

onio-brachialis 

. hyoideus 

. orbicularis  oculis  . 

. palpebrsB       .      . 

. orbito-palpebral     . 

. panniculus  carnosus    . 

palato-glossus  .... 

pharyngeus  . 

staphyleus    . 

palmaris  magnus   . 

pectineus 

pectoralis  magnus . 

_ parvus     .... 

. transversus  . 

pedal     

perforans    ....        268, 

perforatus 

pericardium 

peristaphyieus  externus 

internus  . 

peroneus     .... 

pharyngo-glossus  . 

. staphyleus    . 

plantaris     .... 

popliteus     .... 

postea  spiuatus 

posterior  constrictor  of  vulva 

. great  rectus  of  head 

. medius    .... 

. ulnaris    .... 

■ protractor  of  sheath    . 

. psoas  magnus  .... 

. parvus     .... 

pterygoideus  internus 

pterygo-pharyngeus    . 

quadratus  cruralis 

lumborum     . 

retractor  aui    .... 

oculi        .... 

of  sheath 

rectus   

. abdominis 

. capitis  anticus  major 

minor 

posticus  major 

oculi  externus    . 

inferior 

. internus 

superior     . 

retractor  oculi 

rhomboideus    .... 

sacro-coccygeal 

coccygeus  inferior    . 

. superior 

lumbaiis 


INDEX. 


PAGE 

822 
292 
ih. 
Ill 
379 
254 
198 
832 
217 
831 
832 
186 
339 
342, 374 
342 
266 
289 
233 
234 
231 
311 
302,  568 
267, 304 
512 
343 
ib. 
298 
339 
,374 
304 
ih. 
251 
883 
195 
222 
265 


342 


Muscles,  sartorius     . 

scalenus      .... 

scuto-auricularis  externus 

internus     . 

semimembranosus 

semispinalis  dorsi  . 

semitendinosus 

serratus  magnus    .      , 

short  abductor  of  arm 

adductor  of  leg  . 

extensor  of  fore-arm 

flexor  of  fore-arm 

■ small  adductor  of  thigh 

anterior  rectus  of  head 

anterior  serrated 

complexus     . 

extensor  of  fore-arm 

hyoglossus    . 

lateral  rectus 

oblique  of  abdomen 

posterior  rectus 

serrated 

psoas 

scapulo-humeralis 

supermaxillo-nasalis 

solearis 

soleus   .... 

sphincter  ani   . 


212 
214 
224 
374 
292 
214 
414 
827 
868 
284 
243 
199 
ih. 
195 
ib. 
829 
ih. 
ib. 
828 
829 
828 
188 
215 
216 
ih. 
ib. 
214 


vagmte    . 

spinalis  colli     . 

dorsi        ... 

splenius      .... 

square  crural  . 

of  loins    . 

stapedius    .... 

sterno-aponeuroticus  . 

costales    . 

humeralis 

hyoideus 

maxillaris 

prescapularis 

thyro-hyoideus  . 

thyroideus     . 

trochineus     . 

stylo-glossus  . . 

hyoideus 

maxillaris 

pharyngeus  . 

subcutaneous  of  neck 

sublimis  of  phalanges 

subscapularis   . 

subscapulo-hyoideus    . 

subspinatus 

supercostals 

superficialis  costarum. 

superficial  gluteus 

flexor  of  phalanges 

pectoral  . 

superior  constrictor  of 

supermaxillo-labialis 

superspinatus  . 

temporal     . 

tempoi'o-auricularis  externu 


'  ph: 


PAOT5 

,  288 
.  200 
.  848 
.  849 
.  288 
.  209 
.  287 
.  236 
.  250 
,   289 
.  259 
.  256 
,  291 
.   199 
.  205 
.   191 
.  269 
.  330 
.   199 
.  242 
.  194 
.  195 
.  205 
.  214 
.  254 
221 
".  304 
ib. 
.     414 
.  880 
.  193 
.   209 
.   189 
.  292 
.  214 
.  843 
.  232 
.  237 
.  232 
,   198 
ib. 
.     234 
.  198 
lb. 
.     233 
.   337 
227 
*.  225 
343,  375 
.   196 
.  267 
.  252 
,  198 
.  251 
.  237 
.  205 
.  280 
267,  304 
.  231 
s  .  374 
.  220 
.  251 
.  223 
.  847 


INDEX. 


947 


PAGE 

Muscles,  teniporo-auricularis  internus  .  849 

tensor  palati 343 

tympani 843 

vaginai 880 

teres  major 249,  253 

minor 250 

thyro-arytenoidens      ....  454 

pharyngeus 374 

tracheal 459 

transrersalis  abdominis     .      .      .  244 

costarum 208 

hyoidei 228 

nasi 221 

transverse  of  abdomen       .      .      .  244 

of  ribs 236 

spinous  of  back  and  loins     .  209 

transversus  perinei      ....  863 

trachelo-mastoideus     .      .      .      .  191 

trapezius 203 

triangularis  of  sternum    .      .      .  237 

triceps  extensor  brachii    .      .      .  258 

trochlearis 829 

ureters,  of 490 

urethra,  of 862 

uterus,  of 879 

vagina,  of 880 

Wilson's  muscle     ....   493,  862 

zygomatico-auricularis      .      .      .  847 

zygomatico-labialis      .      .      .      .  219 

zygomaticus ib. 

Muscular  cell-fibres 429 

fibre 4,  178 

insertions,  table  of      .      .      .      .  315 

lamina 905 

tissue 5 

non-striped ib. 

striped ib. 

of  heart 508 

Musculi  papillares 503 

pectinati 506 

Myeloplaxes 4, 15 

Myolemma 178 

Nasal  cavities ^39,  440 

duct 834 

fossae 441 

meatuses 442 

Navicular  sheath 269 

Navicularthritis 158 

Nerve-cells 4, 652 

corpuscles 652 

fibres 4 

tubes 652 

Nerves: — cerebro-spinal    ....  700 

cranial 703 

distribution 701 

division    ......  700 

ganglionic      ....   652,  701 

mixed 700 

organic  life,  of     ...      .  652 

origin 701 

structure 700 

termination 702 

vegetative  life,  of      .      .      .  652 


Nerves,  in  Birds 

abducentes 

accesory  of  external  sa 

of  internal  saphe 

acromial     . 

anal      .... 

angularis    . 

anterior  brachial   , 

femoral   . 

gluteal    . 

tibial       .      , 

auditory 

auricular,  anterior 

middle     . 

posterior 

axillary 

brachial,  anterior 

buccal  .... 

cardiac 

chorda-tympani 

ciliary  .      .      .'      , 

circumflex 

clavicular  . 

coccygeal    . 

cochlear 

collateral-dorsal     , 

crural  .... 

cubito-cutaneous    . 

plantar    . 

dental   .... 

anterior  . 

middle     . 

posterior . 

diaphragmatic. 

digastric 

dorsal,  collateral    . 

great 

facial    .... 

femoral,  anterior  . 

femoro-popliteal,  great 

small    . 

frontal 

glosso-pharyngeal . 

gluteal,  anterior    . 

posterior 

gustatory   . 

ha;morrhoidal 

hypoglossal 

great 

small 

iliaco-muscular 

inguinal,  external 

internal  . 

infra-orbital     . 

infratrochlear  . 

ischio-rauscular 

Jacobson's  . 

lachrymal  . 

laryngeal,  external 

inferior   . 


superior 

lino-ual 


■  masseteric 
maxillary,  inferior 


pne 


PAGB 

789 
721 
774 
771 
749 
752 
754 
759 
771 
772 
774 
727 
725 

ib. 

ib. 
757 

715 
785 
,724 
718 
757 
749 
752 
727 
765 
771 
759 

ib. 
(13,717 
713 

lb. 

ib. 
749,  753 
725 
765 
757 
721 
771 
773 
774 
711 
727 
772 
773 
716 
752 
737 


716 
771,772 
751 


713 

712 

773 

728 

711 

733 

734, 

733 

716 

715 

714 


948 


INDEX. 


Nerves,  maxillary,  superior 

median 

mental 

musculo-cutaneou 

s])iral 

mylo-hyoid 

nasal     . 

obturator   . 

occipito-styloid 

oculo-motor,  common 

external 

internal 

oesophageal 

recurrent 

superior  , 

olfactory     . 

ophthalmic  of  Willis 

optic     .... 

orbital 

palatine,  anterior  . 

posterior 

palmar 

palpebro-nasal 

pathetici     . 

pectoral 

perforating  intercostal 

——  peroneal  cutaneous 

petrous,  great  deep 

superficial 

small  deep     . 

superficial 

pharyngeal 

phrenic 

plantar 

external  . 

internal  . 

pneumogastric 

popliteal,  external 

portio-dura 

intermedia    . 

mollis 

pterygoid,  internal 

pudic,  internal 

radial    .... 

recurrent   . 

oesophageal    . 

respiratory 

internal  . 

rhomboideal     .   .  . 

sacral   .... 

saphena,  external  . 

internal  . 

accessory 

sciatic,  great    . 

small 

spheuo  palatine 

spinal    .... 

■ — - — ■ accessory 

splanchnic,  great   . 

lesser 

staphylin   . 

stylo-hyoid 

subclavian 


73 


PAGK 
712 

759 
717 
4,  757 
7«8 
717 
713 
771 
7-25 
708 
721 
709 
735 
735 
733 
705 
711 
706 
712 
ib. 
713 
766 
712 
709 
755 
750 
774 
728 
722 
728 
724 
733 
753 
7G0,  766 
760 


ib. 
728 

774 
721 
722 
727 
716 
752 
758 
734 
735 
755 
753 
754 
751 
775 
771 
771 
773 
772 
713 
746,  752 
736 
786 
787 
713 


767 


PAGE 

Nerves,  sublingual 717 

subzygomatic 716 

superscapular 757 

temporal,  anterior  deep    .      .      ,  716 

middle  deep 715 

posterior  deep     ....  ib. 

superficial 716 

thoracic,  inferior 755 

subcutaneous      ....  ib. 

superior ib. 

tibial,  anterior 774 

posterior 775 

trachea],  recurrent      ....  734 

trifacial 710 

trigeminus ib. 

trochlearis 709 

tympanic 724 

tympano-lingual    .      .      .      .717, 724 

ulnar 759 

vestibular 727,  840 

Vidian 719 

Wrisberg,  of 723 

Nerve-tubes  of  spinal  cord         .      .      .  671 

Nervous  coUine 180 

glands 495 

medulla 652 

sheath ib. 

system 650 

general  comformation    .      .  651 

of  Birds 790 

tissue 5 

Neural  arch 119 

Neurilemma 653,  700 

Neurility 655 

Neuroglia 670,  671 

Nodule  of  Arantius 505 

Nodus  encephali 675 

Nomenclature 326 

Non-meduUated  fibres 652 

Nostrils 439,440 

framework       .......  440 

functions 441 

Nucleated  nerve-fibres 652 

Nuclei  of  corpus  striatum    ....  696 
oT  nerves 671,705 

Obturator  foramen 93 

Occipito-atloid  sinus 606 

Ocular  membrane 822 

sheath 828 

(Esophageal  groove 397 

CEsophagus 377 

course ib. 

form ib. 

functions 380 

relations 377 

■ structure 379 

Oken's  bodies 922 

Olfactory  apparatus 815 

cel'ls 445,  816 

lobules 691,  692 

nerves 705 

Omasum 397 

structure 399 


INDEX. 


949 


PAGE 

Omentum,  gastro-colic  ....   382,  389 

gastro-splenic 383,  429 

great 382,389 

Omphalo-mesenteric  duct     ....      894 

vessels 899,915 

Opaque  area 892 

Ophthalmic  nerve 711 

Optic  chiasma 707 

commissure »'j- 

layers 675 

nerves 706 

papilla 824 

thalami 675 

Ora  serrata 820,  824 

Orbiculare,  os 843 

Orbital  cavity 817,  828 

Organ  of  Corti 839 

of  Jacobson 443 

^ of  RosenmliUer       ....    876,923 

Organic  life,  nerves  of    .      .      .      .    652,  653 

Organs     5 

hollow 326 

structure  of ib. 

solid 328 

structure  of        .      .      .    328, 329 

Os  orbiculare 843 

externum 879 

ti-icaj ib. 

uteri ib. 

Osseous  labyrinth 837 

Ossicula  auJitus 842 

Ossification,  centres  of 16 

Osteo-dentine 347 

desm 118 

Osteogeny 16 

Osteology 6 

Ostium  abdominalis 876 

uterinum ib. 

Otoconites 839 

Otoliths ib. 

Ova  of  Birds 925 

Ovaries 872 

development 874,  924 

functions 874 

situation 872 

structure 873 

Oviducts 876 

Ovisacs 873 

development 874 

rupture    ■ ib. 

structure 873 

Ovula  Xabothi 879 

Ovulum 873,890 

modifications  in 890 

Ovum 873 

Pacchionian  glands 663 

Pacinian  corpuscles 703 

Palate 332, 356, 359 

hard     ....      333,  356,  359,  360 

functions  of 334 

■  structure 333 

soft       ....     340,  357,  359,  360 

functions  of       ....     343 

63 


PAGE 

Palate,  soft,  muscles 342 

structure 342 

Palatine  glands 370 

Palatum  moUe 340 

Palmar  arch 575 

Palpebra; 830 

Palpebral  sinuses ib. 

Pampiniform  j)lexus 856 

Pancreas 427 

development 922 

excretory  apparatus    ....  428 

•  form 427 

functions 428 

relations 427 

situation ib. 

structure 428 

Pancreatic  ring 427 

Papilla  cornica 824 

Papilla; 327 

of  foot 803 

ofskm 792,793 

of  tongue 336 

calyciformes 336,  814 

capitatas ib. 

circumvallatffi        ....  ib. 

filiformes ib. 

fossulate 336 

fungiformes 336,  814 

lenticulares ib. 

Parieto-temporal  confluents       .      .      .  608 

Parotid  duct 367 

gland 365,370,371 

Parovarium 867 

Pathetici  nerves 709 

Pavilion  of  Fallopian  tube   ....  876 

Pecklin's  glands 404 

Pecquet,  cistern  of 634 

Pectoral  cavity 462 

Pedunculi  cerebelli 675 

cerebri 675,  677 

Pelvis 91 

difference  in  sexes        ....  97 

in  general 95 

Penis 865 

Peptic  glands 391 

Perforans  tendon,  sheath  of       .      .      .  269 

Pericardium 512 

muscle  of ib. 

Perilymph 840 

Perimysium 179 

Perineum 882 

aponeuroses  of 863 

Perineurium 653 

Periople 806 

Perioplic  ring 803 

Periorbita 828 

Periosteum 14 

Peritoneum 381 

structure  of 384 

Perivascular  canals 665 

Perspiration 797 

Perspiratory  ducts 794 

glands ib. 

Pes  anserinus 712 


950 


INDEX. 


PAGE 

Pes  hippocampi   .......  679 

Petit,  canal  of 827 

Petrosal  sinuses 606 

Peyer's  glands 404 

Phalanges 82,  105 

Pharyngeal  arches 912 

ctecum 373 

clefts 912 

Pharynx 372 

development  of 920 

disposition 372 

form ''->• 

functions 37b 

muscles 374 

relations 373 

structure 374 

Phillips's  muscle 264 

Phrenic  centre 246 

Pia  mater 665 

cranial i'). 

■ spinal ib- 

Pigment  cells 821 

Pigmentary  corpuscles  of  horn        .      .  810 

granules 822 

Pigmentum  nigrum 822 

Pillars  of  diaphragm 247 

of  fornix,  anterior       ....  695 

posterior 694 

of  heart 503 

of  inguinal  canal 242 

of  rumen 395 

of  soft  palate 341 

anterior      ....  ib. 

jiosterior    ....  ib. 

of  tongue,  anterior      ....  335 

posterior ib. 

Pineal  gland 680 

Pisiform  tubercle 678 

Pituitary  fold  of  dura  mater     .       .    662,663 

gland 681 

membrane 444 

glands  of 445 

nerves  of ib. 

stalk 681 

Placenta 895,  899 

structure  of 899 

multiple 903 

■ simple i'y. 

Plantar  arcade  or  arch   555 

cushion 801 

bulbs  of 802 

structure  of        ....  ib. 

tunic,  of ib. 

nerves 761 

reticulum 612,  804 

Pleura 464 

structure 465 

Pleuritis,  effusion  of 466 

PI  euro-peritoneal  cavity      ....  906 

Plexus,  general  anatomy      ....  701 

anterior  auricular       ....  726 

mesenteric 787 

brachial 749,754 

bronchial    .......  732,735 


PAGE 

Plexus,  carotid -      - 

783 
469 

capillary,  of  lungs . 

cavernous  

783 
749 

cervical,  deep  .... 

■ superficial 

.      749 

choroides    ..... 

.      687 

cerebellar 

.      688 

coronary  (venous) 

612,614 

gastric 

.      787 

guttural 

783 
788 

hypogastric      .... 

lumbo-aortic    .... 

.     787 

sacral      .... 

.      770 

lymphatic 

.      629 

■  mesenteric,  anterior    . 

.      787 

■ posterior 

.      788 

myenteric 

.     406 

pampiniform    . 

.      856 

.      788 

•  pharyngeal 

728,  785 

podophyllous,  venous  . 

612,613 

787 

solar,  venous    . 

612 

• splenic        .... 

787 

■ subzygomatic  . 

7- 

2,  726 

superficial  cervical 

749 

suprarenal 

787 

■ •  sympathetic     . 

782 

786 

vaginal       .... 

423 

venous        .... 

597 

Plicae  palmata;    .... 

886 

Pneumogastric  lobule     . 

689 

Podoph3'llous  tissue 

804 

Pons  Valorii        .... 

6" 

5,677 

Popliteal  glands 

64D 

Portio  dura 

721 

727 

Porus  opticus       .... 

818 

Pouches,  giittural     . 

845 

Pou  part's  ligament  . 

241 

Praeputial  glands 

867 

Prajputium  clitoridis 

882 

Precervical  nerve 

794 

Precrural  glands 

640 

Preparation  : — arteries     . 

520 

dissection    . 

521 

injection 

520 

arteries,  anterior  tibial 

551 

aorta,  posterior  . 

524 

— — axillary  , 

560 

femoral   .      .      . 

547 

head,  of  . 

577 

iliac,  internal 

538 

internal  iliac 

ib. 

popliteal 

549 

posterior  tibial   . 

550 

pulmonary    . 

521 

tibial,  anterior    . 

551 

posterior    . 

550 

articulations    . 

130 

atlo-axoid 

135 

carpal 

.    148,149 

chondro-sternal 

141 

INDEX. 


951 


PAGK 

Preparation,  articulations,  costo-sternal  141 

coxo-femoral        .      .      .      .  161 

f'emoro-tibial       ....  163 

first  interplialangral      .       .  156 

humero-raclial    ....  144 

hyoideal 139 

interphalangeal,  first     .      .  156 

second        ....  157 

metacarpo-phalangoai    .      .  153 

— • — • occipito  atloid    .      .      .      .  137 

pelvis 159 

scapulo-humeral       .      .      .  143 

spine,  of 130 

tarsus 168 

temporo-maxillary  .      .      .  138 

auditory  apparatus      ....  837 

bracliial  plexus 755 

■ ■  bronchi 460 

clioroid  coat     ......  820 

cornea 819 

cranial  nerves 705 

ear,  internal 877 

enceplialou 674 

eye 817 

great  sympatlietic  nervous  system  781 

lieart 503 

structure  of        ....  507 

hoof 799 

■  internal  ear 877 

— intestines 400 

larynx 449 

liver 419 

lumbo-sacral  plexus     ....  770 

lungs 466 

lymphatics 633 

maxillary  gland 367 

mouth 330 

muscles 184 

abdominal  region,  iuferinr  .  239 

alveolo-labialis          .      .       .  218 

anterior  brachial  region       .  255 

crural  region  .      .       .  283 

medius       ....  231 

axillary  region   ....  ib. 

brachial  region,  anterior      .  255 

posterior       .       .  258 

cervical  region,  inferior       .  196 

— superior        .      .  187 

•  costal  region       ....  235 

crural  region      .      .      .      .  283 

• anterior  .      .      .  ib. 

internal  .      .      .  288 

—  posterior       .      .  286 

diaphragmatic  region     .      .  245 

external  scapular  region      .  249 

eye 828 

■femoral  region    ....  283 

flexor,  short,  of  fore-arm     .  256 

fore-arm,  of        ....  261 

gluteal  region     ....  280 

■  hyoideal  region  ....  225 

■  inferior  abdominal  region    .  239 

• cervical      .      .      .      .196 

• lumbar  region       ,      .  211 


Preparation,  muscles,  internal  scapular 

region 

252 

labialis 

217 

leg 

297 

lumbar  region,  inferior. 

211 

masseteric  region 

223 

— — mastoido-humeralis  . 

196 

medius,  anterior       .      .    22 

2,223 

j)anniculus 

186 

scapular  region,  external     . 

249 

— internal  . 

252 

spinal    region    of  back    aui 

loins    

203 

•  siiblumbar  region     . 

211 

— superior  cervical 

187 

— temporo-maxillary  region    . 

223 

nasal  cavities 

440 

oesophagus 

377 

palate  

332 

pancreas     

419 

parotid  gland 

365 

pericardium 

512 

pharynx      

372 

retina 

824 

soft  palate 

340 

• spinal  cord 

666 

spleen 

419 

■ stomach 

385 

■ submaxillary  gland     . 

367 

■ sympathetic  nervous  system  . 

781 

thoracic  duct   , 

643 

tongue        

.     334 

■ trachea 

.     457 

• urinary  apparatus 

,     484 

vems 

.     599 

Prepuce 

.      867 

of  clitoris 

.      882 

Preservation  of  muscles 

,      185 

Primitive  aortte 

.      915 

band  of  Remak       .... 

.      652 

chorion 

.      896 

eye-vesicles 

.     908 

fasciculus 

.     178 

furrow 

.     892 

trace     

.        ib. 

Primordial  kidneys 

.     922 

Processes  e  cerebello  ad  testes   . 

.     678 

Promontory  of  ear 8 

40,  842 

Properties  of  nervous  system     . 

.     655 

Prostate  gland 

.      864 

structure      .... 

*. 

Protoplasm 

3 

Protuberantia  annularis 

.      675 

Protovertebrffi     9 

05,  911 

Pi-otovertebral  cavity     .... 

.      905 

Pulmonary  artery     .      .            <.      . 

.      521 

heait    ...            ... 

.      503 

lobes . 

,     466 

lobules 

.     468 

opening  of  heart    .... 

.      505 

— —  pleura 

.     464 

tissue 

.      467 

vesicles       ...... 

.     468 

Puncta  lachrvmalia        .      .      o      . 

.      834 

952 


INDEX. 


PAGE 

Punctum  caecum 824 

Pupil 822 

Pupillary  membrane 824 

spliiuctei- 823 

Purkinje's  vesicle 92^ 

Pylorus •       •      •      ^^? 

Pyramidal  eminence  of  OS  pedis       .      .        85 
Pyramids  of  tiie  bulb 676 

Racemose  glands 329,  339 

Eachidian  bulb 675 

Raphe  of  scrotum 853 

Receptaculum  chyli        .      .      .      .      .  634 

Recto-vesicle  fold 860 

Rectum 413 

attachment 4-13 

development 920 

relations 413 

sti'ucture 414 

Recurrent  sensibility 650 

Reflex  power 657 

Reil,  band  of 678 

Reissner,  membrane  of 839 

Remak,  primitive  baui  of    ...      .  652 

Renal  glomerules 488 

pelvis 486 

Reseau  admirable      .      .      .        590, 591, 593 

Reservoir  of  thymus  gland  ....  473 

Respiratory  apparatus 439 

^"  of  Birds.      ......  475 

of  Mammifers     ....  439 

nerves 704 

Retemirabile      ....        593,594,631 

mucosum 796 

ophthalmicum 595 

testis 855 

Reticular  layer  of  the  derma     .      .      .  793 

Reticulum 397 

structure ib. 

processigerum 613 

Retina 824 

Retrossal  process  of  os  pedis      ...  85 

Rhomboidal  sinus           907 

Ribs         67 

Right  auricle  of  heart 505 

ventricle     „ 503 

Rima  glottis 456 

Ring,  inguinal 242 

pancreatic 427 

umbilical,  inferior       ....  894 

Vieussens,  of 506 

Rings  of  trachea 468 

Rivinian  ducts 369 

Rolando,  gelatinous  substance  of     .      .  670 

Root  of  lungs 461,  466 

Rosenmilller,  organ  of    .      .      .      .   866,  923 

Rudimentary  sinuses 606 

Rumen     .    " .394 

—  structure  of 396 

Sacculus  of  ear 839 

Sacral  nerves 752 

Sacrum 26 

Salivary  glands 364 


PAGE 

Salivary  glands,  development  of     .      .  920 

ducts 357,369 

lobules     . 364 

Saphena  A'eins 624 

Sarcolemma        , 178 

Sarcous  elements ib. 

Scala,  auditive 839 

■-  collateral ib. 

Lowenberg's ib. 

tympani 838,  839 

vestibuli     .......         ib. 

proper 839 

Schindylesis 129 

Schueiderian  membrane       ....  444 

structure  of       ....  445 

Schwann,  white  substance  of    .      .      .  652 

Sclerotica 817 

Sclerotic  cleft 909 

Scrotum 853 

Scutiform  cartilage 846 

Sebaceous  glands 794 

Secondary  dentine 347 

Segmentation  of  vitcllus      ....  890 

Semen 857 

Semicircular  anastomoses    ....  555 

band 680 

canals 837 

ganglia 711 

valves        505 

Semilunar  crest  of  pedal  bone   ...  84 

fibro-cartilages 163 

Seminiferous  tubes 855 

Sensitivo-motor  centre 657 

Sensorial  functions         658 

Septum  auricularum 503 

lucidum 092,  694 

pectiniforme 865 

scroti 853 

ventricularum 503 

Serous  bursas 183 

membrane 328 

stratum  of  epiblast     ....  893 

vesicle ib. 

Sesamoid  bones 84 

Sheaths,  arteries  of 516 

hair  of 798 

lymphatic 630 

metacarpo-phalangeal       .      .      .  267 

navicular 269 

ocular 54,828 

penis,  of 867,  868 

perforans  tendon,  of   .      .      .      .  269 

Schwann,  of 652 

tarsal 305 

Shell,  egg  of 925 

membrane ib. 

Shoulder,  bones  ot 72 

Sigmoid  valves 505,  507 

Simple  follicles         404 

glands 329 

placenta 903 

Sifius  ampullaceous 839 

aortici 522 

circularis  iridis 821 


INDEX. 


953 


Sinus  cutaneous  ungularum 

lactiterus 

pocularis    . 

I'enalis 

rhomboidalis    . 

terminalis 

Valsalva;    . 

Sinuses,  structure  of 
aortic   .... 

dura  mater,  of 

in  genera 

in  particul: 

cavernous  . 

fals  cerebri,  of 

• median 

■ occipito-atloid 

petrosal 

rudimentary    . 

sphenoidal 

spinal  in  particular 

- — —  transverse 

galactoferous   . 

head,  of      .      .      . 

development  of 

functions  of 

ethmoidal 

frontal    . 

■ maxillary,  infer 

• superior 

sphenoidal     . 

lymphatic 

palpebral    . 

renal     . 

rhomboidal 

— —  subarytenoid 

subepiglottic 

terminalis 

Valsalva,  of 

Skeleton 
Skin 

appendages  of 

derma 

epidermis  . 

— '—  functions    . 

structure  . 

Small  intestines 

Smegma  praputii 

Smell,  apparatus  of 

Socia  parotidis    . 

Soemmering,  foramen  of 

Soft  palate    ....     340 

Sole  of  hoof 

Solid  organs 

structure  of 

Solitary  glands  . 
Speculum  Helmontii 
Spermatic  cord 
Sphincter  ani 

pupillaris  . 

vagmte 

Spinal  arachnoid 

canal    . 

cord 

■ external  surface  of 


35 


PAGE 

.  724 

884,  885 
861 
486 
683,  907 
915 
522 
597 
522 
G05 
606 

ib. 

lb. 

ib. 

ib. 

ib. 

ib. 

ib. 
447 
608 
606 
884,  885 
446 
447 
448 
447 
446 
447 

lb. 

ib. 
532 
830 
486 
683,  907 
456 

ib. 

915 

522 

7 

792 

797 

792 

795 

796 

2,  796 

400 

867 

815 

372 

836 

, 359,  360 

807 

328 

328, 329 

404,  410 

246 

856 

414 

823 

880,  883 

663 

659 

666 

668 


Spinal  cord,  figure    . 

geneial  view  of 

internal  conformation 

— structure 

volume    . 

weight    . 

dura  mater 

marrow 

nerves 

constitution 

nerve-tubes  of 

pia-mater  . 

Spine,  the,  in  general 
Splanchnology    . 
Spleen     .... 

attachment 

development    . 

direction    . 

form 

functions    . 

relations     . 

situation    . 

structure   . 

weight 

Splenic  corpuscles     . 

pulp      .      .      . 

Spongy  portion  of  iireth 
Spontaneous  voluntary  movements 
Stapes     .... 
Staphyline  glands     . 
Stars  of  Verheyen    . 
Stenon's  duct 
Stenson's  duct    . 
Stilling,  dorsal  nucleus 
Stomach  in  Solipeds 

— development 

dimensions 

— form 

functions 

• interior 

ligaments 

muscular  m^ 

orifices    . 

situation 

structure 

Carnivora  . 

Pig       ... 

Ruminants 

functions 

Subarachnoid  fluid 
Subarytenoid  sinus 
Subcorneous  integument 
Subcutaneous  region 
Subepiglottic  sinus 
Subhepatic  veins 
Sublingual  crest 

gland    . 

Sublobular  veins 
Sublumbar  reservoir 
Submaxillary  gland 
Subpodophj'Uous  reticulum 
Subsphenoidal  confluents 
Substantia  gelatinosa 
ostoidea 


66 


PAGE 

ib. 
666 
668 

8.669 
668 
ib. 
661 
651 
747 
748 
671 
665 
28 
326 
428 
429 
922 
428 
ib. 
431 
428 
ib. 
429 
ib. 
430 
429 
862 
657 
843 

ro.  371 
489 
367 
443 
671 
385 
920 
386 


393 

388 

389 

ib. 

388 

386 

389 

393 

ib. 

ib. 

399 

663,  664 
456 
803 
106 
456 
423 
334 

369,371 

424,  425 
634 

567,371 
613 
608 
670 
346 


954 


INDEX. 


Substantia  perforata 
Suburethral  notch  . 
Succus  prostaticus  . 
Sudoriparous  glands 
Sulci  horizontalis  . 
Superior  umbilicus 
Sujirarenal  capsules 

development 

form 

functions 

relations 

situation 

structure 

Suprasphenoidal  appendage 
Suspensory  ligament  of  fetlock 

penis 

sheath 

uterus 

Sylvius,  fissure  of 
Sympathetic  nervous  system 

• functions 

structure 

Symphyses    . 
Synarthroses 

classification  o 

Synovia   . 
Synovial  capsules 

f0SS£E      . 

fringes 

Syntonine 
Systole  of  heart 


86: 


of 


Tactile  corpuscles 
Taenia  hippocampi 

semicircularis 

Tail    .... 

Tajietum 

Tarin,  valves  of 

Tarsal  sheath 

Tarsi 

Tarsus 

Taste,  apparatus  of 

Teats       .      .      , 

Teeth       .      .      . 

character 

development  of 

disposition  of 

eruption  of    . 

external  conform 

structure 

ofCarnivora    . 

Pig        .... 

Ruminants 

Solipeds 

Tegumentary  membranes 
Temporal  fossa    . 
Tela  choroidea    . 
Tendinous  sheaths    . 

synovial  membranes 

Tendo-Achilles    . 

Tendons  

anterior  extensor  of  metacarpus 

common,  of  abdominal  muscles 

deep  flexor       


itiou 


PAGF 

.  (392 
.  866 
.  86+ 
.  794 
.  686 
.  893 
.  494 
.  495 
.  494 
.  495 
.  494 

ib. 

ib. 
.  681 
.  154 
866,  872 
.  867 
.  877 
691,  692 
,  781 
.  789 

ib. 
.  129 
.  128 
.  129 
.  127 
.  126 
.   123 


680, 


820, 
687, 


347, 


127 
181 
513 

703 
695 
,695 
797 
822 
689 
305 
831 
102 
813 
884 
344 

ib. 
921 
344 
921 
344 
345 
261 
359 
357 
349 
5 

55 
696 
183 


302 
179 

262 
240 
268 


PAGE 

Tendons,  extensor  pedis        ....  263 

—  external  flexor  of  metacarpus       .  266 

flexor,  of  metatarsus         .      .      .  300 

— ■ hock 302 

gastrocnemii ib. 

great  dorsal 294 

large  extensor  of  fore-arm      .       ,  258 

lateral  extensor  of  phalanges        .  264 

middle       „ 259 

oblique  flexor 266 

perforatus 267,  304 

perforans   ....        267,  268,  305 

prepubic 240 

Tentorium  cerebelli        ....    662,  663 

Tentacula 797,798 

Terminal  genital  corpuscles       .      .      .  866 

motor  plate 180,702 

vessels 517 

Testaceous  membrane 925 

Testes  cerebelli 678 

— — -  muliebres 872 

tubercula 679 

Testicles 851,  853 

attachment  of 853 

descent  of 942 

development  of      ...      .    856,  923 

eetopiaa  of 853 

envelopes  of 852 

external  conformation       .      .      .  853 

function  of 857 

structure  of 854 

Testicular  cord ib. 

Thalami  optici 675,  679 

Thebesius,  valve  of  .....      .  506 

Theca  vertebralis 661 

Thiernesse's  muscle 264 

Third  ventricle  of  brain       ....  682 

Thoracic  aorta 524 

cavity 462 

duct' 634 

affluents  of 637 

course  of 634 

extent ib. 

origin ib. 

termination         ....  635 

varieties  iu ib. 

Thorax 66,462 

■ •  functions  of 466 

in  general 70 

internal  conformation        .      .      .  462 

situation ib. 

Thymic  ducts 474 

Thymus  gland 473 

development        ....  919 

■ functions 473 

structure ib. 

Thyroid  cartilage 450 

Thyro-hyoid  membrane 452 

Thyroid  "gland 472 

functions 473 

structure 472 

Tibial  aponeurosis 297 

Tissues 4 

Toe-stay 808 


INDEX. 


955 


PAGE 

Tongue 334,  357,  359,  360 

conformation  of 334 

development  of 920 

functions  of 340 

muscles  of 336 

pillars  of 335 

situation  of 334 

structure  of 335 

Tonsils 335 

of  cerebellum 689 

Torcular  Herophili 606 

Trabeculse  of  spleen 429 

testis 855 

Trachea 457 

course ih. 

development 918 

form 457 

relations ih. 

structure 458 

Trace,  primitive 892 

Tracheal  glands 459 

Tractus  lougitudiualis 693 

opticus 707 

respiratorius 704 

Transverse  sinuses 606 

Tricuspid  valves 504 

Trifacial  nerve 710 

Trigeminii ib. 

Trigonum  vesicEE 493 

Trisplanchnic  system 781 

Trochlea  .      .    " 128 

Trochlearis  nerve 709 

Tuber  annulare 677 

cinerium 681 

Tubercula  nates 679 

-^^  quadrigeniina ib. 

testes ib. 

Tuberculum  Loweri 506 

Tubular  glands 322 

Tubuli  seminiferi 854 

uriniferi 487 

Tuft  of  chin 331 

Tunic  of  plantar  cushion      ....  802 

Tunica  abdominalis 239 

albuginea  of  ovary       ....  873 

of  testicle 854 

erythroides 852 

Euyschiana 821 

vaginalis 852 

communis ib. 

propria ib. 

reflexa ib. 

vasculosa  testis 855 

Tympanal  circle 841 

Tympanic  scala 839 

Tympanum 840 

Ultimate  follicles 365 

Umbilical  cord 895,  900 

arteries 900 

region 381 

veins 900 

vesicle        ....        894,  895,  899 

Umbilicus,  superior 893 


Unipolar  nerve-cells 
Unitmg  tube  of  kidney 
Unstriped  muscular  fibr 
Urachus  . 
Ureters    . 

direction 

form 

origin    . 

structure    . 

termination 

Urethra   . 

male,  of 

course 

interior 

relation: 

structure 

female,  of  . 

Urethral  ridge    . 

sinus     . 

Urinary  apparatus 
Uro-genital  sinus 
Uterine  glands     . 

tubes    . 

functions  of 

structure 

Uterus 

attachment 

development 

■ —  form 

functions    . 

interior 

masculine  . 

•  situation     . 

• structure    . 

Utricular  glands 
Utriculus  of  ear 

prostatic    . 

Uvula  of  cerebellum 

Vagina     .... 

functions    , 

internal  conformat 

situation     . 

structure    . 

Vaginal  bulb 

sheath  . 

synovial  membrane 

Valsalva,  sinus  of 
Valves,  Bauhin,  of    . 
bicuspid 

Eustachian 

ilio-caecal    . 

Kerking,  of 

lymphatic  . 

meatus  urinarius 

mitral  . 

Renault,  of 

semicircular     . 

sigmoid 

Tarin,  of     . 

Thebesius,  of   . 

tricuspid    . 

veins,  of     . 

Vieussens,  of   . 


PAGE 

.     653 

.  488 
327, 328 
894,  897 
490 

ih. 

ib. 

ib. 

ib. 

ib. 
493 
861 

ib. 

ib. 
862 

ib. 
882 
862 
866 
484 
923 
879 
876 

ib. 

ib. 
877 

ib. 
880 
877 
880 
877 
861 
877 


839 
861 
689 

880 

882 

880 

ib. 

ib. 

883 

852 

183 

552 

402 

507 

506,  514 

402,  408 

.  402 

.   627 

.  882 

.  507 

683, 686 

.  505 

505,  507 

687,689 

.  506 

.   504 

.   597 

675,  679 


956 

Valves,  vulvo-vaginal 
Valvulte  conniventes 
Varolii,  pons 
Vasa  afferentia    . 

ei!erentia    . 

iuferentia  . 

recta     . 


INDEX. 


vasorum 
of  veins 


vorticosa     . 

Vascular  blood  glands    . 

Vas  deferens 

structure  of 

Vegetative  life,  nerves  of 

Veins: — definition  . 

external  conformation 

general  considerations 

injection  of    . 

internal  conformation 

structure 

abdominal,  subcutaneous 

alveolar      .... 

angular  of  eye 

auricular,  anterior 

. —  posterior 

axillary      .... 

basilic 

basium  vertebrarium 

buccal 

csecal 

cardiac        .... 

cai-dinal,  anterior  . 

posterior 

cephalic      .... 

central  of  foot 

of  retina 

cervical,  superior  . 

circumflex  of  foot 

coUatei-al  of  cannon,  exte 

internal 

coronary,  great 

small 

of  foot 

dental,  inferior 

superior  . 

diaphragmatic . 

digital  

dorsal 

femoi'al       .... 

Galeni 

gastric,  anterior    . 

• gastro-epiploic,  left     . 

glosso-facial 

hemorrhoidal 

humeral      .... 

iliac,  common  . 

external 

internal  . 

•  ilio-cajcal    .... 

innominate 

• ■  interlobular  of  liver    . 

■  interosseous 

intralobular  of  liver    . 


nal 


67 


PAGE 

887 
402 
5,677 
632 
632, 855 
632 
855 


ib. 
599 
597 
599 
625 
602 
ib. 
604- 
602 
609 
611 
131 
603,  605 
620 
599 
917 


520 
598 
821 
330 
859 
860 
652 
596 


603,611 
613 
825 
600 
613 
611 
ib. 
599 


614 
605 
603 
617 
2,  625 
600 
623 
608 
621 
621 
ib. 
602 
621 
610 
622 
623 
622 
620 
603 
423 
612 
424 


Veins,  iutra-osseous  of  foot 
jugular       .      .      . 

labial    .... 

lingual 

mammary,  internal 

maxillary,  extei-nal 

internal  . 

maxillo-muscular  . 

median  spinal  . 

subcutaneous 

■ •  mesenteric,  great  . 

• small 

meseraic,  anterior . 

■  • posterior 

■ •  metacarpal 

metatarsal 

deep  . 

external  . 

internal  . 

nasal     .... 

occipital 

■ omphalo-mesenteric 

pelvi-crural      . '     . 

plat       .... 

podophyllous    . 

■ popliteal     ... 

portal  .... 

posterior  communicati 

pterygoid   . 

pulmonary. 

radial,  anterior 

subcutaneous 

renal     .      . 

saphena,  external  . 

internal  . 

solar     .... 

spermatic  . 

splenic 

spur      .... 

subcutaneous,  abdomi 

internal  . 

thoracic  . 

subhepatic 

sublingual 

subscapular 

subzygomatic  . 

superficial  temporal 

siiprahepatic    . 

• temporal,  deep 

. siiperficial     . 

■ testicular   . 

Thebesii 

thoracic,  internal  . 

thyroid 

tibial,  anterior 

■ posterior 

ulnar    .... 

umbilical    . 

ungual 

utero-ovarian  . 

vertebral    . 

cava,  anterior  . 

posterior 

Velum  interpositum 


PAGE 

616 
601 
603 
605 
600 
602 
601, 605 
601 
608 
611 
620 
621 
620 
621 
611 
624 


'  foot 


603 
602 
915 
622 
603 
613 
623 
617 
615 
605 
599 
.0,  611 
611 
621 
624 
ib. 
612 
621 


60 


jO] 


610 
625 
611 
610 
619 
603 
610 
605 
1,603 
619 
605 
1,603 
622 
599 
600 
603 
623 
624 
610 
916 
612 
622 
600,  917 


ib. 
691,  696 


INDEX. 


957 


PAGE 

Velum  pendulum  palati       ....  340 

vasculosum 696 

Velvety  tissue  of  foot    ....    803,  804 

Vena  azygos,  great 600 

small ib. 

cava,  anterior 600 

posterior 617 

Galeni 691,  696 

porta 617 

Venre  comites 598 

vorticosa 8"21 

Ventricles  of  brain   .      .      682,  683,  692,  693 

cerebellar 688 

cerebral 693 

■  lateral 692,  693 

middle 682 

posterior 683 

third 682 

thalami  optici  of      .      .      .  628 

of  heart 500 

of  larynx 456 

Ventricular  arachnoid 694 

mass  of  heart 500 

Vermiform  appendix 418 

processes  of  cerebellum     .      .      .  686 

anterior     ....  ib. 

posterior    ....  ib. 

Vermis  of  cerebellum 687 

VertebrjE 18 

characters  common  to       ...  19 

proper  to 21 

development 20,  911 

structure 20 

Vertebral  column 18 

development  of  .      .      .      .  911 

constitution  of  skeleton    .      .      .  118 

lamina 905 

Vertebro-costal  channels      ....  462 

Veru  montanum 861 

Vesicle,  serous 893 

umbilical 899 

Vesicles,  Graafian 873 

pulmonary       .      .      .      .      .      .  468 

Vesicula  alba 894 

seminal  is  tertia 861 

Vesicula;  seminales 860 

Vestibular  scala 839 

Vestibule  of  ear 837 

Vibratile  cilia 327 

Vibrissa 449 

Vicq-d'Azyr,  cacum  of 658 


Vidian  canal       .... 

fissure        .... 

nerve    

Vieussens,  centrum  ovale  of 
Villi,  intestinal 

Villosities 

Villo-papiilfe  of  foot 
Villous  loops  of  foot 

Vitellus 

Vitreous  body     .... 

humour      .... 

Viscera 

Visceral  pleura  .... 
Vision,  apparatus  of 
Vitelline  duct     .... 

globules     .... 

Vocal  cords 

superior 

Voluntary  movements   . 

Vulva 

cavity  of    ...      . 

external  opening  of     . 

structure    .... 

Vulva  of  brain  .... 
Vulva,  labia   .... 


PAGE 

724 
ib. 


719 

697 
402 
327 
803 

ib. 

•3,  890 

827 

ib. 


326 
464 
816 
894 
925 
452 
453 
658 
882 
ib. 


Wall  of  hoof       .      .      . 

angle  of 

structure  of 

Wharton's  duct 
gelatine  of 


.   .   883 
.   .   699 

.   .  882 

.   .  805 

.   .  808 

.   .  ib. 

.      .  368 

.   .  900 

White  line  of  hoof 812 

substance  of  Schwann       .      .      .  652 

spinal  cord 671 

longitudinal  fibres  of  brain    .      .  685 

transverse          „           .,          .      .  ib. 

Wilson's  muscle        .      .      .      .      .    862, 863 

Winepress  of  Herophilus      ....  606 

Winslow,  foramen  of 383 

Wirsung,  duct  of 428 

Wolffian  bodies 922,  923 

Wrisberg,  nerve  of 723 

Xiphoid  appendage  of  sternum        .      .       67 

Yelk 873,890 

Yolk  of  egg .     925 

Zona  pellucida 873,  890 

Zonula  ciliaris 821,  824 

of  Zinn ib. 

Zoijsperma 858 


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and  interesting  work.     One  vol.,  i2mo.     Cloth,  $1.50. 

Contributions   to   Molecular   Physics  in  the 
Domain  of  Radiant  Heat. 

A  Series  of  Memoirs   published   in  the  "Philosophical   Transactions"  and 
"Philosophical  Magazine."      With  Additions,     i  vol.,  8vo.     Cloth,  $5.00. 

Lectures  on  Light  delivered  in  America. 

With  numerous  Illustrations.  Small  i2mo.  Illustrated.  Paper,  75c. ;  cloth,  $1. 

D.  APPLETON  &  CO..  Publishers,  549  &  551  Broadway,  N.  Y. 


The  Colored  Plates  illustrating  this  edition  of  the  work  requiring 
great  care  in  printing,  were  executed  in  London, 


SPECTRUM  ANALYSIS, 

In  its  Application  to  Terrestrial  Substances,  and  the  Physical  Constitu- 
tion of  the  Heavenly  Bodies, 

Familiarly  explained,  by  Dr.  H.  Schellen,  Director  der  Realschule  I.  O. 
Cologne.  Translated  from  the  second  enlarged  and  revised  German  edi- 
tion, by  Jane  and  Caroline  Lasell.  Edited,  with  Notes,  by  William  Hug- 
gins,  LL.  D.  With  numerous  Woodcuts,  Colored  Plates,  and  Portraits ; 
also,  Angstrom's  and  Kirchhoff's  Maps.     455  pages,  8vo,  cloth.     Price, 


Frotn  the  Chemical  News. 
"This  admirable  work  does  credit  to,  or  should  we  say  is  worthy  of  the  author,  the 
translators,  and  the  editor.  The  first  part  treats  on  the  artificial  sources  of  high  de- 
grees of  heat  and  light ;  the  second  on  Spectrum  Analysis  in  its  application  to  the 
heavenly  bodies.  We  must  approve  the  method  followed  in  the  translation,  and  by  the 
editor.  In  many  translations  the  views  of  the  author  are  suppressed,  in  order  that  the 
views  of  the  translator  or  editor  may  be  expounded ;  but  here  Dr.  Huggins,  however 
leniently  such  a  fault  might  have  been  looked  upon  with  him,  has  permitted  the  author's 
views  to  remain  intact,  clearly  stating  his  own  and  wherein  lies  the  difference." 

From  the  Chicago  Post. 
"The  object  of  this  volume  is  to  introduce  the  general  reader  into  a  new  realm  of 
science,  and  acquaint  him  with  the  particulars  and  the  results  of  the  most  brilliant  dis- 
covery of  the  present  century.  Whoever  has  an  appreciative  sense  of  the  beauties  and 
wonders  of  Nature,  illuminated  by  science,  will  find  this  volume  a  rich  mine  of  enjoy- 
ment which  he  will  do  wisely  to  explore." 

From  the  Philadelphia  Age. 
"The  contents  are  formidable  in  appearance,  but  the  average  reader  will  find  its  ex- 
position easily  intelligible.     To  many  the  revelations  of  this  book,  so   marvellously 
minute,  and  yet  so  unerringly  accurate,  will  be  as  wonderful  as   the   stories   of  the 
'Arabian  Nights.'" 

Fro7n  the  Boston  Globe. 
"Certainly,  as  regards  mere  knowledge,  the  Spectrum  Analysis  has  let  us  into 
many  secrets  of  the  physical  universe,  which  Newton  and  Laplace  would  have  declared 
impossible  for  man's  intellect  to  attain.  The  science  is  still  in  its  infancy,  but  it  is 
piosecuted  by  some  of  the  ablest,  most  patient,  and  most  enthusiastic  observers,  and 
some  of  the  keenest  thinkers,  at  present  existing  on  our  little  insignificant  physical 
globe." 

D.  APPLETON  &  CO.,  Publishers, 

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